HomeMy WebLinkAboutUpper Susitna River Basin Supplemental Feasibility Report 1979L
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SOUTHCENTRAL RAILBELT AREA. ALASKA
UPPER SUSITNA RIVER BASIN
SUPPLEMENTAL FEASIBILITY REPORT
APPENDIX -PART I
Section A -Hydrology
Section B -Project Description and Cost Estimates
Section C -Power Studies and Economics
Section D -Foundations and Materials
Section E -Environmental Assessment
Section F -Recreational Assessment
~.~ r~e~~,ed With
. . .R.L.l.S.
ALASKA. . t
u.s. D ''_.It £ -..
RY
February 1979
T'\---
SECTION A
HYDROLOGY
The 1976 Interim Feasibility Study was based on
25 years of historical streamflow records. Data
through 1977 has been added, extending the period
of historical streamflow to 28 years. The annual
runoff for the additional 3-year period was 96
percent of the long-term average.
Power capabilities of the hydroelectric projects
were reevaluated on the basis of the extended
period of record. The results of this analysis
appear in Section C, Power Studies and Economics.
SECTION B
PROJECT DESCRIPTION AND COST ESTIMATES
SECTION B
PROJECT DESCRIPTION AND COST ESTIMATES
Item
SUMMARY OF CHANGES
General
~Jatana
Devil Canyon
WATANA
Dam
Spillway
Outlet Works
TABLE OF CONTENTS
Diversion Features and Operation
Penstocks and Waterways
DEVIL CANYON
Ma i n Dam
Spillway
Diversion Structure
Powerplant
Penstocks and Waterways
CONSTRUCTION SCHEDULE
General
Diversion Plans
Ma in Dams
Power-on-Line
Transmission Line
COST ESTIMATES
Detailed Cost Estimates
Cont -j ngenc i es
Watana
Devil Canyon
LIST OF TABLES
Page
B-1
B-1
B-1
8-2
B-3
B-3
B-3
B-4
8-4
B-4
B-5
B-5
B-5
B-5
B-6
B-6
B-7
B-7
B-7
B-7
B-7
B-8
B-9
B-9
B-10
B-10
B-ll
Number Title Page
B-1 Detailed Cost Estimate -Watana (First added) B-13
B-2 Detailed Cost Estimate Devil Canyon Concrete Gravity
(Second added) B-23
i
LIST OF PLATES
Number Title
8-1 Selected Two-Dam Plan -General Plan
8-2 Watana Dam -Detail Plan
8-3 Watana Dam -Sections
8-4 Watana Dam -Profiles
8-5 Watana Dam -Profiles, Sections, and Details
8-6 Watana Dam -Details
B-7 Devil Canyon Dam -Concrete Gravity Dam -Detail Plan
8-8 Devil Canyon Dam -Concrete Gravity Dam -Elevation
and Sections
LIST OF FIGURES
8-1 Construction Schedule
i i
SUMMARY OF CHANGES
GENERAL
Field surveys during 1978 revealed that topography for Watana dam
shown in the 1976 Interim Feasibility Report was 15 feet higher than
actual conditions. Data in this report has base elevations corrected
to the 1978 topography. Only plates or text revised for this submittal
will reflect the new elevations which are 15 feet lower. The top of
dam is now shown at elevation 2,195 feet and normal pool at elevation
2,185 feet.
Quantities and cost estimates have been revised and updated to
October 1978 levels. The cost for Watana dam and reservoir (first-added)
is $1,765,000,000 versus $1,088,000,000 in the 1976 report. The cost
for Devil Canyon dam and reservoir (second-added) is $823,000,000
(concrete gravity) and $665,000,000 (concrete arch) versus $432,000,000
(concrete arch) in the 1976 report.
A construction schedule reanalysis resulted in the extension of the
construction period from 10 to 14 years. Initial power-on-line is
anticipated in 1994.
WATANA
The main dam cross section was revised to best utilize materials as
determined in 1978 field investigationso A grouting gallery was added
under a portion of the dam.
The spillway was moved laterally and revised to take better advan-
tage of rocklines and to discharge directly into Tsusena Creek at stream
1 evel .
The outlet works were revised to improve hydraulic layout and
access into the intake structures.
The diversion tunnel portals were relocated in better rock based
upon information obtained from the exploration program.
The power intake selective withdrawal system was revised to be more
comparable with those currently in use at other projects.
Rock excavation
tinuous cut slope.
should be terraced.
are compatible with
quantities in the 1976 report were based on a con-
Foundation explorations concluded that the rock cuts
Data in this report is based upon rock cuts that
this latest field information.
B-1
As a result of new and more accurate topography, the length of the
dam has changed; therefore, total embankment quantities have increased.
DEVIL CANYON
A gravity dam was evaluated and is presented with an overdam spill-
way, and the diversion structure modified to be more compatible with a
gravity structure.
Elevator access was provided to the powerplant instead of a road
access tunnel.
The power intake selective withdrawal system was revised to be
more comparable with those currently in use at other projects.
The general plan showing the locations of the two dams is on Plate
B-1.
8-2
WATANA
DAM
The crest length of the dam has changed from 3,450 feet to 3,765
feet, based upon new topography.
As a result of explorations in the river bottom, the foundation
excavation has been revised. The river alluvium will be removed to
bedrock under the cam. A grout gallery, excavated into rock, has been
added to insure adequate treatment of the permanently frozen bedrock.
The 1976 Interim Feasibility Report presented an earthfill dam
utilizing local gravel deposits for shell material. Explorations have
revealed that there are insufficient gravel deposits within economic
haul distances. Since a large amount of sound rock will be generated
from spillway excavation and an excellent quarry source is available
immediately adjacent to the damsite, the design has been revised to
substitute rockfill for gravel in the upstream and downstream shells.
Field explorations revealed an abundance of glacial till in the area
suitable for use as core material. For this reason, a semipervious
zone has been added to use the less expensive glacial material rather
than quarried rock. The filters have also been revised to take advan-
tage of adequate quantities of gravelly sand and the readily available
rock quarry (see Plate B-3). The gravelly sand from Borrow Pit E, near
the mouth of Tsusena Creek, will be used for the fine filter, and rock-
fill, in the smaller sizes from the quarry, will be used for the coarse
filter. Details of the revisions are discussed in Appendix D, Founda-
tions and Materials.
SPILLWAY
The saddle spillway centerline has been moved approximately 800
feet southwest (see Plates B-2 and B-5). The foundation explorations
more definitely located top of rock in this area; therefore, the spill-
way was relocated to insure construction in rock. Crest gate widths
were reduced from 59 feet to 55 feet after additional hydraulic calcu-
lations. The concrete lined downstream channel section was lengthened
from 150 feet to 800 feet to protect against rock plucking caused by
high water velocities. The length of channel divergence was revised
from 930 feet downstream of the crest to 1,360 feet to improve hydraulics.
The spillway channel slope was revised, requiring excavation its full
length, so that it emerges at the Tsusena Creek level to reduce environ-
mental damage expected from the 400-foot vertical water drop over natural
terrain with the original spillway design. This substantially increases
excavation; however, almost all of the material will be used in the dam
embankment.
B-3
OUTLET WORKS
The intake structures were moved, shifting the high level intake
structure away from the dam embankment, realining both intake tunnels
to improve connections to the diversion tunnels and changing the access
shafts from within the embankment to tunnels through the right abutment
rock upstream of the dam (see Plates 8-4 and 8-6). This improves access,
eliminates problems associated with a structural shaft in the embankment,
and reduces susceptibility to damage from seismic events. The high level
intake invert was raised to restrict operating heads on gates to under
250 feet.
DIVERSION FEATURES AND OPERATION
The two diversion tunnels were lengthened, both upstream and down-
stream, to locate the portals in better rock as a result of exploration
data obtained in 1978. The roller gates for controlling the diversion
tunnels have been deleted because stream regulation is not required
during diversion. Wheeled bulkhead gates will be used to close one
tunnel at a time during periods that closures are required. The diver-
sion tunnel inverts have been raised to reduce cofferdamming and
dewatering requirements at tunnel portals. Cofferdam height will
remain unchanged since there is outlet control of diversion tunnel
flows up to cofferdam design flood. The scheme of tunnel plugging
and water control during pool filling has not changed. See Plate 8-6
for plug and fill valve details.
PENSTOCKS AND WATERWAYS
The selective withdrawal system, designed to select water at elevations
within the reservoir which will allow meeting downstream water quality
requirements, has been revised to be more comparable with those currently
in use on other projects. This revision requires a larger concrete
structure on the upstream face of the dam to accommodate the gates,
trashracks, bulkheads, and operating equipment.
8-4
DEVIL CANYON
MAIN DAM
A concrete gravity dam (see Plates B-7 and B-8) is substituted in
this report for the double curvature thin arch structure of the 1976
Interim Feasibility Report. The thin arch dam's structural integrity is
dependent on the adequacy and integrity of the rock abutments. Founda-
tion investigations to date have raised no doubts concerning the abut-
ment rock structures but are inadequate to clearly establish abutment
conditions. The necessary horizontal drill holes at the vertical canyon
walls were estimated to be so costly that to proceed in the summer of
1978 would have prevented obtaining other required foundation data at
Watana damsite with the funds available. A careful reevaluation of the
situation indicated a study of the more conservative and technically
feasible gravity structure should be made. The concrete gravity struc-
ture is economically feasible. The required foundation investigations
will be conducted during the preconstruction advance engineering and
design period and the less expensive arch structure will be constructed
if adequate foundation conditions exists.
The gravity section will be 650 feet high from bottom of excavation.
based on indications that the rock is fractured near the surface. The
crest remains at elevation 1,455 feet. The concrete crest length will
be 1.590 feet and the earthfill portion will have a 720-foot crest length.
No field explorations were conducted at this site under the 1978
program except for three refraction seismograph lines. This information.
combined with the borings data collected by the Bureau of Reclamation
that was discussed in the initial report, is the basis of the foundation
design for the site.
SPILLWAY
The gravity dam will have a central gated overdam spillway discharg-
ing into the existing river channel.
DIVERSION STRUCTURE
The diversion tunnel has been lengthened from 1,150 feet to 1,230
feet because of the longer gravity dam base length. Since flow regula-
tion during d"iversion is not required, the intake gates have been replaced
with wheeled bulkhead gates. Regulation of Watana reservoir to release
water into Devil Canyon reservoir will be utilized to fill the reservoir
to the low level outlets in a matter of hours after diversion tunnel
closure. Proper timing will allow maintaining of downstream flows with
minimum interruption.
B-5
POWERPLANT
The access tun~el to the powerplant has been replaced with a housed
vertical entrance shaft and elevator. This shaft will be 20 feet by 30
feet wide by 548 feet deep and will house an elevator capable of lifting
the largest items required in the powerhouse. The l85-foot long access
tunnel will connect the access shaft to the powerplant. The elevator
will provide equipment, personnel, and vehicular access to the power-
plant level at elevation 907 feet.
PENSTOCKS AND WATERWAYS
The selective withdrawal system has been revised to be more compar-
able with those currently in use at other projects. The system has
been designed to select water at elevations within the reservoir which
will allow meeting downstream water quality requirements. This revision
required a larger concrete structure on the upstream face of the dam
to accommodate the gates, trashrack, bulkheads, and operating equipment.
B-6
CONSTRUCTION SCHEDULE
GENERAL
The construction period has been reanalyzed and extended from 10
to 14 years. The Watana dam and powerplant will take 10 years to con-
struct, an increase of 4 years over the previous schedule. The Devil
Canyon project construction will require 8 years rather than the pre-
viously reported 5 years. There will be 4 years of overlapping con-
struction to meet power-on-line dates. The schedule is portrayed
graphically on Figure B-1.
DIVERSION PLANS
The Watana diversion works construction and stream diversion period
has been extended to 3 years, from the previously reported 2 years,
because the construction access to the tunnel portals requires extensive
rock cuts and additional time. The start of construction of the diver-
sion works for the Devil Canyon dam has been delayed from the 5th to
the 7th year of Watana construction because it is dependent on stream
regulation by the upstream Watana dam.
MAIN DAMS
Foundation preparation at Watana is delayed to the 4th year as a
result of the extended diversion requirements which delay the start
of cofferdam construction. Watana embankment construction is scheduled
to begin in the 5th year and continue into the 10th, now requiring 6
years instead of the previously reported 3 years, based on construction
seasons of 5 months with daily placement rates of 80,000 cubic yards.
Water impoundment starts in the 8th year with power-on-line in October
of the 10th year. The reservoir filling would continue beyond the power-
on-line date and is dependent on inflow and power generation.
Foundation preparation for Devil Canyon dam would start in the 9th
year, a delay from the earlier reported 7th year of Watana dam construc-
tion. Concrete placement and dam completion would start in the 10th year,
requiring 5 years, an increase of 2 years over the earlier schedule.
Impoundment would begin in the 13th year with reservoir filling completed
by October of the 14th year.
POWER-aN-LINE
The scheduled power-on-line dates are 1994 for Watana and 1998 for
Devil Canyon compared to those previously scheduled in 1986 and 1990,
respectively. These dates include the result of the changes in scheduled
B-7
Congessional construction authorization from July 1980 to October 1984
and the reanalyzed construction schedule. The construction schedule
in the 1976 report was based on an authorization for construction, while
the Chief of Engineer's Report recommended authorization for Phase I
AE&D. This recommendation incorporated 4 years for study prior to
seeking construction authorization.
TRANSMISSION LINE
Transmission line construction is scheduled to be completed in 1991,
making it available to tie the Anchorage and Fairbanks areas together
in advance of Watana power-on-line.
8-8
COST ESTIMATES
DETAILED COST ESTIMATES
Tables B-1 and B-2 present the cost estimates for Watana and Devil
Canyon.
The estimates are presented in as much detail as possible based on
the concept drawings. Unit cost for a major items also includes minor
items that will appear as bid items as the design progresses.
Extensive use has been made of bid abstracts from similar projects
constructed in the western United States and Canada. All abstracted
costs have been escalated to the October 1978 level and an additional
factor applied to reflect the higher cost of construction in Alaska.
The Alaska Power Administration (APA) prepared the transmission
line cost estimate and have updated the estimate to the October 1978
level. The transmission line cost estimate includes all structures,
equipment and transformers for the switchyards and substations for
Watana, Devil Canyon, Fairbanks, and Anchorage. The transmission line
cost is shown in Table B-1, Watana.
The transformers 1 isted under "S witchyard" in Tables B-1 and B-2
are located in an underground transformer chamber adjacent to the power-
house. The cables listed connect the transformers to potheads located
in the switchyard.
The APA estimate did not include earthwork for the switchyards.
This cost is shown under "S witchyard" "in Tables B-1 and B-2.
The following lists the estimated January 1975 cost and the October
1978 cost.
Watana
Devi 1 Canyon
Thin Arch Dam
Concrete Gravity Dam
Jan 1975
($1 ,000)
$1,088,000
432,000
Oct 1978
($1,000)
$1,765,000
665,000
823,000
The project cost used in the economic analysis includes Watana and
the concrete gravity dam plan at Devil Canyon. The total cost is
$2,588,000,000.
B-9
CONTI NGENC I ES
Watana Dam
The total estimated contingencies for Watana dam are $245,917,000,
or 18 percent of the estimated Watana construction cost. The main dam,
the largest single feature of Watana project, has a contingency of 15
percent, or $58,178,000. This is a relatively uncomplicated earth and
rockfi11 structure. The 1978 exploration program established founda-
tion conditions and sources of suitable embankment materials in suffi-
cient quantities to construct the dam. The overburden is minimal and
foundation rock exposed over much of the site. Radical changes in
foundation conditions and borrow sources are not anticipated.
The design approach for the spillway is conservative for a rela-
tively uncomplicated structure. Fifteen percent contingencies, or
$20,528,000, were estimated.
The outlet works estimate includes 20 percent contingencies, or
$7,016,000. The estimate includes 100 percent lining of the diversion
and outlet tunnels. If rock quality is good, some of the lining may
be deleted.
The power intake works estimate includes 20 percent contingencies,
or $40,772,000.
The powerhouse estimate includes 20 percent contingencies or
$13,294,000. The underground powerhouse interior feature requirements
are known from comparison with other projects and a careful review of
this item.
Turbines, generators, accessory electrical equipment, and miscel-
laneous powerplant equipment are estimated with 15 percent contingencies.
These are known features with quantities and basic costs furnished by
experienced powerhouse design personnel.
The tailrace tunnels are assumed to be 100 percent concrete lined.
If the rock quality is 900d, some of these lining requirements may be
deleted. Contingencies for this feature are 15 percent.
Twenty percent contingencies were used for transmission facilities.
The transmission system estimate was prepared by the Alaska Power
Administration with consultation with Bonneville Power Administration.
Contingencies of 20 percent were used for roads and bridges.
Assumptions on foundations assume extensive tundra removal and replace-
ment with nonfrost susceptable fill which requires large borrow quantities
for replacement.
B-10
The construction facility requirements have been reviewed and com-
pared with facilities required for similar structures on similar projects
such as Dworshak, Mica and Oroville. The Trans Alaska Oil Pipeline
construction camp experience was also reviewed. Diversion tunnels are
assumed to be fully lined and rock support assumptions during tunneling
have been conservative. Careful analyses of means of diversion and
procedures have been made. Contingencies for construction facilities
are 20 percent.
Devil Canyon Dam
The total contingencies used for the Devil Ca~yon gravity dam
estimate are $120,551,000, or 20 percent of the Devil Canyon construction
costs. Contingencies for all features are the same percentages as for
Watana dam for the same reasons, except that contingencies for the main
dam, spillway, and auxiliary dam features have been increased to 20
percent.
Twenty percent contingencies were used for the main dam. Assump-
tions on foundation excavation and preparation for a gravity dam are
conservative. Both abutments are exposed rock. The concrete gravity
structure is relatively simple with known features. Aggregate locations
and quantities available have been established.
The auxiliary earthfill and concrete dam was estimated at 20 per-
cent contingencies. The borrow source is known, partially explored,
and quantities determined. This is a simple, uncomplicated structure.
Foundation excavation and preparation assumptions are conservative.
The total contingencies for the thin arch dam alternate are
$103,756,000 or 21.2 percent of the updated total estimated construc-
tion cost of $665,000,000.
In general, the contingencies used for this project are based on
intensive study and comparison with cost histories and experience with
other projects.
The Office of Management and Budget (OMB) has questioned the con-
tingencies used based on a 36 percent overrun on the Snettisham project.
The project cost estimate for the Snettisham project was $41,500,000 for
fiscal year 1967. the first year of construction. This estimate included
the Long Lake phase of project development, camp facilities, the trans-
mission system, and related features. The Crater Lake phase of project
development was added in fiscal year 1973, but design and construction
were subsequently deferred.
B-11
The estimate submitted to Congress for fiscal year 1976 was
$98,540,000, of which $22,132,000 was a price level adjustment, reflect-
ing a 35 percent cost overrun; however, with deferment of the Crater
Lake phase, total expenditures through fiscal year 1978 are $81,386,975,
an actual cost overrun of $17,754,975, or 22 percent. This cost overrun
includes the temporary repair and subsequent permanent relocation of a
failed portion of the transmission line. Environmental considerations
dictated its original location in an area of unanticipated and unknown
extreme winds and ice conditions not previously encountered on any trans-
mission line in North America. The increased cost for the transmission
line temporary repairs and permanent relocation was $9,976,000 of the
overrun, reducing the remainder of the overrun to $7,778,985 or 10 per-
cent. This information is reflected in the General Accounting Office
Report to Congress on Financial Status of Major Civil Acquisitions -
December 31, 1975, dated 24 February 1975.
B-12
TABLE B-1--DETAILED COST ESTIMATE
WATANA DAM AND RESERVOIR ELEVATION 2185
OCTOBER 1978 PRICE LEVEL
(FIRST -ADDEO)
Cost
Account Unit Total
Number Description or Item Unit Quant Cost Cost
($) ($1,000)
01 LANDS AND DAMAGES
Reservoir
Public domc.in AC 2,560 195.00 500
Private land AC 99,170 186.00 18,446
Site und other AC 1,080 185.00 200
Access road AC 780 186.00 "145
Transmission facilities AC 3,965 965.00 3,826
Recreation AC 90 222.00 20
Mining claims EA 4 8,000.00 32 .
Subtotal 23,169
Contingencies 20% 4,634
Government administrative costs. 880
TOTAL LANDS AND DAr~AGES (28,683)
Construction cost 28,000 Economic cost ( 500)
03 RESERVOIR
Mob and Prep LS 1 204
. Clearing AG-5,100 800.00 4,080
Contingencie's 20% 857
TOTAL, RESERVOIR 5,000
04 DAMS
04.1 MAIN DAM
Excavation common
Left abutment CY 1,466,000 5.00 7,330
Right abutment CY 1.292.000 5.00 6,460
River channel CY 1,547,000 5.00 7,735
Rock Excavation
Left abutment CY 616,000 18.00 11 ,088
Right abutment CY 428,000 18.00 7,704
River channel CY 198,000 18.00 3,564
Drainage system LF 135, 000 35.00 4,725
Foundation preparation . SY 114,000 35.00 3,990
Drilling-grouting LF 145,000 50.00 7,250
Care of water and
pumping LS 1 2,000
Mobilization and Prepa-
tory work LS 1 19,000
Instrumentation LS 1 960
Clearing grubbing AC 111 3,500.00 389
B-13
TABLE B-l--U~TAIL~O CUST ESTIMATE--Continued
WATANA DM1 Arm RESERVOI R
Cost
Account
Number Descript: .. o.~ Item Unit
04 DAMS
04.1 MAIN DAM (Cont'd)
04.2
Embankmer::
Semi Pen'i ous
From stockpile
From req. excavation
Impervious
From req. excavation
From bOI'TOW
Rock
From abutments
Cy
cv
cv
CV
riReq .1:excavCiti on CY
Sttickpi 1 e CY
From Spillway Req. exca.CY
From roads (stocKpile) CV
From grout ga 11 er'Y , CV
From stockpile misc. CV
From borrow CV
Filters from borrow CV
Riprap CV
Grout gallery
Excavation CV
Concrete (roof-sides), CV
Cement Cwt
Reinforcement LB
Concrete floor steps,
landings, etc CV
Ventilati8n
Access tun~el from
Powerhouse
Excavation rock
Cor.crete
Cement
Resteel
Subtotal
Contingencies 15%
TOTAL, Mi\ I N DAJvl
SPILLWAY
Cleari~g & stripping
Foundation pl'ep.
Excavdioc
ComnOI)
CY
CV
Cwt
LB
AC
SV
Cy
Quant
1.335,000
4,743,OGO
3,342,000
4,031,000
1,123 JJOO
420,000
'13,693,000
2,348,000
36,000
800,000
17,876,000
7,822,000
223,000
26,700
19,000
87,000
6,793,000
2,750
10,768
6,528
26,109
2,164,000
Unit
Cost
($)
3.50
1.00
l. 00
4.00
.75
3.25
.75
3.25
.75
3.25
9.00
8.00
22.00
75.00
375.00
8.00
.55
500.00
190.00
600.00
8.00
.55
158 2,500.00
33~700 50.00
10,568,000 2.00
Total
Cost
($1,000)
4,673
4,743
3,342
16,124
842
1 ,365
10,270
7,631
27
2,600
160,884
·65,576
4,906
2,003
7,125
696
3,736
1,375
375
2,046
3,917
209
1 ,190
387,850
58,178
446,000
395
1,685
21 ,136
Cost
Account
Number
04
04.2
"II\I\L[ L;-1--UI_lI\I LLU CU',I LJI1I'1/\ IT--CUll L i 111WU
\'JATANA D/\i-l flrW RESERVOIR
Oescri ption or Itclli Unit Quant
DAMS
SPILLWJ\y
Rock CY 10,533,000
Concrete
Mass CY
Structurc.l CY
Lining CY
Cement Cwt
Rei nforcement Lb
Drill & grout for
anchors LF
Tainter gates 1200000#
16,9CJU
9,750
15,600
82,500
1, 23,000
17,200
Unit
Cost
($ )
8.00
100.00
500.00
450.00
8.00
.55
20.00
gate hoists EA
Storlogs (400000#) LS
3 1,250,000.00
1
Spillway bridges
( 55 I L by 26 I W) (3EA) LS
Drainage LS
Mob-Prep LS
Subtotal
Contingencies 15%
TOTAL, SPILLWAY
1
1
1
04.3 OUTLET WORKS
Excavation
Common
Rock
Tunnel 25 0
45° slope
Vertical
Horizontal
Concrete
Lining
45° slope
Rebar
Vert"j ca 1
Rebar
Horizontal
Rebar
Structural
Rebar
Rockbolts
In vertical face
Drill & grout bolts
(92,200 LB)
CY
CY
CY
CY
CY
CY
U3
CY
LB
CY
LI3
CY
LB
LF
8-15
35,700
115,400
29,400
1 ,880
4,250
6,000
322,000
350
14,100
B20
33,100
9,600
900,000
21 ,400
15.00
50.00
190.00
140.00
125.00
600.00
.55
500.00
.55
. 300.00
.55
600.00
.55
20.00
Total
Cost
($1 ,000)
84,264
1 ,690
4,875
7,020
1 ,460
618
344
3,750
600
500
2,000
6,517
136,854
20,528
15/,OOD
536
5,770
5,586
263
531
3,600
177
175
8
246
18
5,760
495
428
T/\I~I.r 1\-1 --Ill T/\I LrIJ COS I Isr Ir~/\lf· --ConI. i n\J('d
WATANA DAM ANU RESERVOIR
Cost
t\ccoun t Unit Total Number Description or Item Unit Quant Cost Cost
(S) (Sl,OOO)
04 DAMS
04.3 OUTLET WORKS
45° Slope LF 4,800 20.00 96
Horizontal LF 4,400 20.00 88
Tainter gates (4) LB 496,000 3.00 1 ,488
Slide gates (4) LB 2,200,000 3.00 6,600
Trashracks (2) LB 64,800 2.00 130
Cement Cwt 110,700 8.00 886
Elevators (50-ton) LS 2 250,000.00 500
Mob and Prep work LS 1 1 ,700
Subtotal 35,081
Contingencies 20% 7,016
TOTAL, OUTLET WORKS 42,000
04.4 POWER INTAKE WORKS
Mob and Prep Work LS 9,700
Intake structure
Excavation (rock) CY 222,000 30.00 6,660
Foundation preparation SY 3,700 50.00 185
Mass concrete CY 39,500 100.00 3,950
Structural concrete CY 102,900 500.00 51 ,450
Cer:lent CVJt 555,600 8.00 4,445
Resteel LB 9,372,000 .55 5,155
Emb. meta 1 U3 35,000 4.50 158
Trash rack LB 938,000 2.00 1 ,876
Stairs LS 1 100
Elevator LS 1 300
Bu"! khead gates LB 3,860,000 2.00 7,720
Stoplogs : LB 1 ,594,000 2.00 3,188
El ectri ca 1 and
mechanical work LS 1 2,250
Truck crane LS 1 300
Bridge LS 1 3,500
Trash boom LS 1 425
Tunnel excavation CY 95,100 175.00 16,643
Concrete CY 35,200 350.00 12,320
Cement Cwt 140,800 8.00 1 , 126
Resteel LB 483,000 .55 266
Steel 1 i ner U3 24,350,000 2.70 65,745
Bor.netted ga tes EA 3 1,800,000.00 5,400
Log Goom LS 1 500
B-16
1/\1 ~ LI_ 1\-1--IJU /\ l LI_IJ ell:) 1 L~)ll M/\ I L --COIl L i Jlu(~d
hATANA DAt1 ArW RESERVOIR
Cost
Account Unit Tota 1
Number Description or Item Ur. it Quant Cost Cost
($) ($1,000)
04 [JAMS
04.4 POWER INTAKE WORKS (Cont'd)
Electrical and
mechanical work LS 500
Subtotal 203,862
Contingencies 20% 40,T/2
TOTAL, POWEF: INTAKE l-JORKS 24~~,OOO
TOTAL DAt~S 8:)O,UUO
07 POWERPLANT
07.1 pm'JERHOUSE
Mob and prep work LS 3,000
Rock excavation, tunnels,
P.H. chamber, trans-
former chamber, etc CY 202,000 75.00 15,150
Concrete CY 57,600 500.00 28,800
Cement Cwt 261 ,000 8.00 2,038
Reinforcerr.ent LB 6,912,000 .55 3,802
Architectural features LS 1 ,500
El eva tors LS 600
r~echanc i a 1 and
electrical work LS 1 5,000
Structural steel U3 1,250,000 2.00 2,500
Misc. ~1etalwork LB 150,000 4.50 675
Draft tube bulkhead
gates -guides LS 750
Rock bo lts LF 8,445 . 30.00 253
Steel sets LB 102,000-2.00 204
600 ton bridge crane LS 1 1,000
" 30 ton bridge crane LS 1 250
Airshaft (transformer
chaillber) 3' DIA 880' LS 900
Subtotal 66,472
Contingencies 20% 13,294
TOTAL, POWERHOUSE 80,000
B-17
-11\/:1[: H-l--On/\IL[I) eusl L S T H~I\ T [ --c () 1\ Lin u e d
WATANA [)M~ AIW R[SERVOIR
Cost
Account Unit Toto 1
Number Description or Item Unit Quant Cost Cost
(S) ($1 ,000 )
07 POWERPLANT (Cont'd)
07.2 TURBINES AND GENERATORS
Turbines LS 1 18,900
Governors LS 1 814
Generators LS 1 21,600
S~Jbtota 1 41,314
Contingencies 15% 6,197
TOTAL, TURBINES AND GENERATORS 48,000
07.3 ACCESSORY ELECTRICAL EQUIPMENT
Accessory Electrical
Equ-ipment LS 3,532
Contingencies 15% 530
TOTAL, ACCESSORY ELECTRICAL EQUIPMENT 4,000
07.4 MISCELLANEOUS POWERPLANT EQUIPMENT
Miscellaneous Powerp1ant
Equipment LS 1 ,716
Contingencies 15% 257
TOTAL, II1ISCELLANEOUS POWERPLANT EQUIPMENT 2,000
07.5 TAILRACE
Mob and Prep Work LS 1 2,400
Tunnel excavation CY 233,000 85.00 19,805
Concrete 1in-ing CY 28,200 250.00 7,050
Cement Cwt 112,800 8.00 902
Reinforcement LB 5,202,000 .55 2,861
Rock bolts LF 51,000 20.00 1 ,020
Steel sets LB 1,115,000 1. 50 1 ,673
Outlet Portal
Excavation rock CY 2,500 75.00 188
Concrete CY 450 500.00 225
Cement Cwt 1,800 8.00 14
Reinforcement LB 207,000 .55 114
Stop1ogs-stee1 LB 737,100 1. 50 1 ,106
Tailrace channel
Excavation rock CY 176,300 50.00 8,815
Concrete CY 4,425 300.00 1 ,328
Cement Cwt 17,700 8.00 142
Reinforcement LB 177 ,000 .55 97
Anchor bars #9 LF 5,700 15.00 86
B-18
1/\ I \ II ! \ -I --Il L"I/\I L I J) C () S I I S I I M/\ 11--C () II Lin I j(' d
WA1ANA UAM A~U klS[RVOIR
Cost
Ilccount
Nun:ber
07
07.5
U:.: scri p t i on or [len]
POWERPLANT (Cont'd)
TAILRACE (Cont'd)
Cofferdam
Subtota 1
CClntingencies 2
TOTAL, TtULRACE
Un~ t
LS
07.6 SWITCHVARD
Transformers
Insulated cables
Earthwork
Subtotal
Contingencies 20%
TOTAL, SWITCHVARD
LS
LS
lS
07.7 TRANSMISSION FACILITIES
08
Transmission facilities LS
Contingencies 20%
TOTAL, TRANSMISSION FACILITIES
TOTAL, POWERPLANT
ROADS AND BRIDGES
Permanent Access Road -
(Highway NO.3 to Oevil
Clearing and grubbing
Excavation
27 mi 1 es
Canyon)
AC
Rock IV
Common CV
Embankment CV
Riprap CV
Road surfacing (crushed) CV
Bridges LS
Culverts and guardrail LS
Permanent Access Road -37 miles
(Devil Canyon to Watana)
Clearing
Excavation
Rock
Common
fiC
CV
CV
B-19
QUilnt
135
200,000
60,000
890,000
2,700
216,000
1
1
195
300,000
90,000
Unit
Cost
($)
1,500.00
20.00
3.00
3.50
30.00
15.00
1,500.00
20.00
3.00
Tota 1
Cost
($1,000)
2,000
49,£1,26
9,9GS
60,000
5,434
2,832
1,300
9,566
1 ,913
11 ,000
255,000
51 ,000
306,000
5n ,000
203
4,000
180
3,115
81
3,240
15,000
1 ,250
293
6,000
270
1/\lllL !\-I--\)[1/\1 LUJ CU~); LS 11 M/\ TL - -CUll L i lIuL:d
WATANA D/\M /\NU RESERVOIR
Cost
Account Unit Total Number Description or Item Ur. it Quant Cost Cost
($ ) ($1,000)
08 ROADS AND BRIDGES (Cont'd)
Embankment CY 1,244,000 3.50 4,354
Riprap CY 3,800 30.00 114
Road surfacing (crushed) CY 304,000 15.00 4,560
8ridges LS 1 5,000
Culverts and guardrail LS 1 2,250
Permanent on-site roads
Pow~r plant access
tunnel LS 1 15,459
Power plant access road LS 1 1 ,97l
Dam crest road LS 1 125
Mob and prep LS 1 3,500
Spillway access road LS 1 560
Switchyard access road LS 1 300
Road to operating
faci 1 ity LS 300
Power intake structure
access road LS 375
Airstrip access road LS 650
Subtotal 73,150
Contingencies 20% 14,630
TOTAL, ROAD AND BRIDGES 38,000
14 RECREATION FACILITIES
Site D
Camp units (tent camp) EA 10 3,000.00 30
Vault toilets EA 2 3,000.00 6
Subtotal 36
Contingencies 20% 7
. Tota 1 Site D 43
Site E
Tra i 1· sys tern MI 12 15,000.00 180
Contingencies 20% 36
Total Site E 216
TOTAL, RECREATION FACILITIES 1,000
19 BUILDINGS, GROUND, AND UTILITIES
Living quarters and
O&M facilities LS 1 2,500
B-20
Cost
Account
Number
19
20
50
I/\[ILL 11-1--l)LII\JUjJ COSI ISIJr~I\I[--C()ntinueu
WATANA DM-' AIW j{[SEI{VOII{
Description or Item Unit Quant
BUILDINGS, GROUNDS, AND UTILITIES (Cont'd)
Visitor facilities
Visitor building LS 1
Parking area SF 12,000
Boat ramp LS 1
Vault toilets EA 2
Runway fac i 1 i ty LS 1
Subtotal
Contingencies 20%
TOTAL, BUILDINGS, GROUNDS, AND UTILITIES
PERMANENT OPERATING EQUIPMENT
Operating Equipment
and Facilities LS
Contingencies 20%
TOTAL, PE~MANENT OPERATING EQUIPMENT
CONSTRUCTION FACILITIES
Diversion tunnels
D.S. Bulkhead
Excavation
Common
Rock
Tunnel 33 H.S.
Concrete
L-ining
Rei nforcerilent
Structural
Reinforcement
Rock bolts
Vertical face
Tunnel roof
Bulkheads
Celnent
Pluq tunnels
Ca re of \va ter
Mob and prep work
Subtotal
Contingencies 20%
LS
CY
CY
CY
CY
LG
CY
LB
LF
LF
LS
Cwt
LS
LS
LS
TOTAL, CONSTRUCTION FACILITIES
B-21
37,700
173,600
336,200
58,350
3,155,000
9,150
1,045,000
24,900
40,OO()
1
386,1"00
1
1
1
Unit
Cost
($ )
3.00
3,000.00
15.00
50.00
90.00
275.00
.55
500.00
.55
20.00
20.00
8.00
TotJl
Cost
(S 1 ,000.'
100
36
200
6
250
3,192
638
~,OOO
2,500
500
3,000
75
566
8,680
30,258
16,046
1 ,73G
4,575
575
493
800
900
3,094
1 ,352
1 ,250
3,500
73,924
14,785
<39,000
-1/\lILl lJ-l--OLTl\l LEO COS I LSI IMATI:.--Con ti nued
WATANA DAM AND RESERVOIR
Cost
Account
Number Description or Item
TOTAL CONSTRUCTION COST
ENGINEERING AND DESIGN 4%
SUPERVISION AND ADMINISTRATION 5%
TOTAL PROJECT COST
WATANA DAM AND RESERVOIR
ELEVATION 2185
(First-Added)
Unit Quant
8-22
Unit
Cost
($)
Tota 1
Cost
($1,000)
1,619,000
65,000
81,000
1,765,000
TABLE B-2--DETAILED COST ESTIMATt
DEVIL CANYON DAM AND RESERVOIR, ELEVATION 1450, GRAVITY DAM
OCTOBER 1978 PRICE LEVEL
Cost
Account
Number Description or Item
01 LAND AND DAMAGES
Reservoi r
Public Domain
State & Private Land
Mining Claim
Subtota °1
Contingencies 20%
(SECOND-ADDED)
Unit
Government Administrative Cost
03
TOTAL, LAND AND DAMAGES
Construction Cost
Economic Cost
RESERVOIR
lV1ob-Prep Work
Clearing
Subtotal
Contingencies 20%
TOTAL, RESERVOIR
04 DAt~S
04. 1 t~AIN DAM
Excavation Rock
Excavation common
Exterior mass concrete
Interior mass concrete
Structural concrete
(dam structure)
Concrete (spillway)
Post cooling
Instrumentation
Pier & spillway rebar
Taintor gates
Bridges
Prevention or water
pollution
AC
CY
CY
CY
CY
CY
CY
LS
LS
Lb
EA
LS
LS
B-23
Quantity
1 ,920
476,400
89,400
256,100
2,138,000
8,883
18,600
1
1
3,255,000
2
1
Unit
Cost
(S)
800.00
20.00
5.00
80.00
75.00
475.00
450.00
.55
1,500,000.00
Total
Cost
($1,000)
(0)
14,160
8
14, 168
2,834
558
18,000
18,000
l8,00C
77
1 ,536
1 ,613
323
2,000
9,528
447
20,488
160,350
4,219
8,370
8,000
900
1 ,790
3,000
700
1 ,000
TABLE 1)-2--DETAI L ED COST EST H~ATE--Conti nucd
D[V 1 L CI\NYOI~ DAM Ai'll) HLSUWOII{, lLLVI\TlOl'~ 145[), GHI\V ITY l)/\I~
Cos t
Account Unit Total
Number Description or Item Unit Quantity lost Cost
($) ($1,000)
04 DAMS
04. 1 MAIN DAM (Contld)
Scaling canyon walls LS 1 ,000
Stop log, COlilP 1 ete LS 1 ,000
Gantry crane LS 750
Elevator LS 600
Stairways LS 686
Rock bolts LS 1,500
Electrical and
mechancial work LS 1 1,500
Miscellaneous metalwork Lb 2,500 4.50 11
Foundation treatment LF 400,000 5.56 2,224
Drilling and grouting LF 70,000 50.00 3,500
Drilling drainage holes LF 52,500 35.00 1 ,838
Concrete for parapet
and over hong CY 3,352 500.00 1 ,676
Resteel Lb 4,296,115 .55 2,363
Slide gates, frames,
guides and operators Sets 4 1,350,000.00 5,400
Chain link fence LF 1 ,845 20.00 37
Resteel for sluce conduits Lb 891,560 .55 490
Exploratory tunnels
(excavation) CY 3,500 400.00 1 ,400
Rock bolts LF 50,000 20.00 1,000
Contraction joint & cooling
system grouting LS 1 2,750
Cement Cwt 7,441,000 8.00 59,528
Mob and Prep LS 1 15,400
Subtotal 323,445
Contingencies 20% 64,689
TOTAL, MAIN DAM 388,000
04.4 POWER INTAKE WORKS
Mob and Prep LS 4,496
Excavation
Open cut CY 7,200 75.00 540
Tunnels CY 34,400 175.00 6,020
Concrete
Mass CY 7,300 100.00 730
Structural und backfill CY 10,430 500.00 5,215
Cement Cwt 74,000 8.00 592
Reinforcing steel Lb 2,478,000 .55 1',363
Penstocks Lb 9,582,270 2.25 21,560
8-24
T/\I~LE Il-2--DUAILED COST lSTIMATE--Cont i nucd
IJI:VIL CMYOI~ lJ/\M /\NIJ R[S[I{VOll{, LLlVATION 1450, GI(AVIIY i)1\t~
Cost
Account
Number
04
04.4
04.5
IJcscri fJtioll or I telll
DA~1S
POWER INTA~E WORKS (Cont'd)
Bonnetted gates and
controls
Stoplogs, (936000#)
Trashracks (421,000# each)
Intake selector gate tower
Excavation rock
Concrete structural
Cement
Reinforcement
Selector gates(l,500,000#)
Subtotal
Contingencies 20%
TOTAL, POWER INTAKE WORKS
Unit
EA
LS
EA
CY
CY
Cwt
Lb
EA
AUXILIARY DAM (EARTH FILL AND CONCRETE)
Mob and Prep LS
Excavation
Dam foundation CY
Foundation prepareation SY
Dam embankment CY
Drilling and grouting LF
Subtota 1
Contingencies 20%
TOTAL, AUXILIARY DAM
TOTAL, DAMS
07 POWERPLANT
07.1 POWERHOUSE
Mob and Prep worK
Excavation, rock
Concrete
Cement
Reinforcing steel
Architectural features
LS
CY
CY
Cwt
Lbs
LS
B-25
Quantity
4-
1
2
7,400
47,100
188,400
7,OG5,00O
Unit
Cost
($ )
1 , 80C , 000.00
1. 50
50.00
500.00
8.00
.55
4-3,375,000.00
100,000
2,100
835,000
8,800
1
208,400
22,000
88,000
5,400,000
1
6.00
50.00
6.00
60.00
75.00
500.00
8.00
.55
Tota 1
Cost
($1 ,000)
7,200
1,875
1 ,263
370
23,550
1,507
3,886
13,500
94,417
18,883
113,000
312
600
105
5,010
528
6,555
1 ,311
8,000
509,000
2,000
15,630
11 ,000
704
2,970
1 ,500
TAGLE G-2--DETAILCD COST lSTIMATE--Continued
DEVIL CANYON DAM AND RESERVOlR, ELEVATION 1450, GRAV lTY DAM
Cost
Account Unit Tota 1
Nunlber Descri pt; on or Itelll Unit Quantity Cost Cost
($ ) ($1 ,000)
07 Po\~ERPLANT
07.1 POWERHOUSE (Cont'd)
E1evJtor LS 200
Mechancia1 and
electrical work LS 1 4,812
Structural steel Lb 1 ,200,000 2.25
Miscellaneous metalwork Lb 150,000 4.50 675
Subtotal 42,191
Contingencies 20% 8,438
TOTAL, POWERHOUSE 51 ,000
07.2 TUR8INES AND GENERATORS
Turbines LS 1 20,250
Governors LS 1 1 ,053
Generators LS 1 22,950
Subtotal 44,253
Contingencies 15% 6,638
TOTAL, TUR8INES AND GENERATORS 51 ,000
07.3 ACCESSORY ELECTRICAL EQUIPMENT
Accessory Electrical
Equipment LS 2,512
Contingencies 15% 377
TOTAL, ACCESSORY ELECTRICAL EQUIPMENT 3,000
07.4 MISCELLANEOUS POWERPLANT EQUIPMENT
Miscellaneous Powerp1ant
Equ"j pment LS 1 ,798
Contingencies 15% 270
TOTAL, MISCELLANEOUS POWERPLANT EQUIPMENT 2,000
07.5 TAILRACE
Mob and Prep LS 1 766
Excavation tunnel CY 74,500 85.00 6,333
Concrete CY 17,500 300.00 5,250
Cement Cwt 70,200 8.00 562
Restee1 Lb 3,029,000 .55 1 ,666
Draft tube bulkh0ad
qJte and guides LS 700
Tailrace tunnel
stoplogs (370,000#) LS 1 800
Subtotal 16,077
Contingencies 20% 3,215
TOTAL, TAILRACE 19,000
B-26
TA3LE 8-2--DETAILED COST LST1MATE--Continued
IJEV[L CI\NYON D/\M /\NO I{[:)ERVOI R, [L[VATION 1450, GRAV ITY DI\M
Cost
Account Unit Total
Number Ucscription or Item Unit Quant ity Cost Cost
($) ($1 ,000 )
07 POWERPLANT
07.6 SvJITCHYARD
Transformers LS 6,545
Insulated cables LS 3,312
Excavation
Rock CY 36,000 20.00 720
Common CY 75,000 5.00 375
Embankment CY 470,000 4.00 1 ,880
Subtota 1 12,832
Contingencies 20% 2,566
TOTAL, SWITCHYARD 15,00Cl
TOTAL, POWERPLANT 141 ,000
08 ROADS AND BRIDGES
Mob and Prep LS 400
On-site road
Clearing and earthwork Mile 2.3 300,000.00 690
Paving Mile 2.3 11 0 ,000. 00 253
Culverts LF 850 100.00 85
Powerhouse and tailrace
access LS 6,000
Road to operating fac; 1 ity Mile 2 125,000.00 250
Portals EA 2 500,000.00 1, 000
Subtotal 8,678
Contingencies 20% 1 ,736
TOTAL, ROADS AND BRIDGES 10,000
14 RECREATION FACILITIES
Site A
(Boat access only)
Goat dock EA 1 40,000.00 40
Camping units EA 10 3,000.00 30
Two-vault toilets EA 2 3,000.00 6
Subtotal 76
Contingencies 20% 15
Total Site A 91
Site B
Access road Mile 0.5 150,000.00 75
Overnight camps EA 50 4,000.00 200
B-27
TABLE B-2--DETAILEO COST lSTIMATE--Continued
ULVIL CArlYON DAM ANO RESERVOIR, ELEVATION 1450, GRAVITY ON~
Cost
Account Unit Total
Number Oeseri ption or I tell! Unit Quant i ty Cost Cost
($) ($1,000)
14 RECREATION FACILITIES
Site B (Co n tid)
Comfort stations EA 2 60,000.00 120
Power LS 1 40
SevJage LS 1 75
Subtota 1 510
Contingencies 20% 102
Total Site B 612
Site C
Trailhead picnic area
access road Mile .2 lSO,OOO.OO 30
Picnic units w/parking EA 12 3,000.00 36
Tra -j 1 sys tern Mile 30 lS.OOO.OO 4S0
Two-vault toilets EA 2 3.000.00 6
Subtotal 522
Contingencies 20% 104
Total Site C 626
TOTAL, RECREATION FACILITIES 1,000
19 BUILDINGS, GROUND, AND UTILITIES
Living quarters and O&M
facilities LS 2,SOO
Visitor facilities
Visitor buildings LS 300
Parking Area LS 70
Boat ramp LS 220
Vault toil ets EA 2 3,000.00 6
Subtotal 3,496
Contingencies 20% 699
TOTAL, BUILDINGS, GROUNDS, AND UTILITIES 4,000'
20 PERMANENT OPERATING EQUIPMENT
Operating Equipment and
facil ities LS 2,200
Contingencies 20% 440
TOTAL, PERMANENT OPERATING EQUIPMENT 3,000
B-28
TABLE B-2--UETAILED COST LSTIMATE--Continued
DEVIL C/\NYOr~ D/\M /\ND RESERVO!f\, ELEVATION 1450, GR/\ V ITY [J/\M
Cost
Account Unit To ta 1
Number Descri ption or Item Unit QUilntity Cos t Cost
($ ) ($1 ,000)
50 CONSTRUCTION FACILITIES
Mob and Prep work LS 1,885
Coffer dams
Sheet pile Ton 1,024 1,500.00 1 ,536
F.arth fill CY 38,000 15.00 570
Pumping LS 1 3,500
Remove Coffer dams LS 1 600
Diversion workds
Tunnel excavation Cy 35,700 100.00 3,570
Concrete CY 9,200 300.00 2,760
Cement Cwt 36,800 8.00 294
Re-j nforcement Lb 1,564,000 .55 860
Steel sets Lb 157,000 3.00 471
Rock bolts EA 1 ,150 300.00 345
Tunnel Plug
Concrete CY 1,100 600.00 660
Cement Cwt 4,400 8.00 35
Reinforcement Lb 187,000 .55 103
Diversion Intake Structure
Excavation rock CY 104,000 30.00 3,120
Concrete structural CY 3,800 500.00 1,900
Cement Cwt 15,200 8.00 122
Reinforcement Lb 380,000 .55 209
~ulkhead Lb 960,000 1. 50 1,440
Approach Channel Lining
Concrete CY 1 ,600 300.00 480
Cement Cwt 6,400 8.00 51
Rei nforcement Lb 80,000 .55 44
Diversion Outlet Structure
Excavation Rock CY 274,000 50.00 13,700
Concrete CY 1 ,100 500.00 550
Cement Cwt 4,400 8.00 35
Reinforcement Lb 110,000 .55 61
Stoplogs Lb 100,000 1. 50 150
Outlet Channel Lining
Concrete CY 900 500.00 450
Cement Cwt 3,600 8.00 29
Reinforcement Lb 45,000 .55 25
Subtota 1 39,555
Contingencies 20% 7,911
TOTAL, CONSTRUCTION FACILITIES 47,000
B-29
Cost
Account
Number
30
31
T/\I\L[ 13-2--DLTA1LlD COST E.STIM/\TE--Continued
DEVlL CANYUN DAM AND RESERVOIR, ELEVATION 1450, GRAVITY DAM
Description or Item Unit
TOTAL, CONSTRUCTION COST
ENGINEERING AND DESIGN 7%
SUPERVISION ANO ADMINISTRATION 5%
TOTAL PROJECT COST
DEVIL CANYON DAM AND RESERVOIR
ELEVATION 1450, GRAVITY DAM
(SECOND-ADDED)
6-30
Quantity
Unit
Cost
($ )
Total
Cost
($1 ,OOO)
735,000
51 ,000
37,000
823,000
SECTION C
POWER STUDIES AND ECONOMICS
SECTION C
POWER STUDIES AND ECONOMICS
TABLE OF CONTENTS
Item
SUMMARY OF CHANGES
STUDY AREA ECONOMY
Summary of Changes
Introduction
Human Resources
Employment
Personal Income
Aggregate Economic Performance
PRESENT AND HISTORICAL POWER REQUIREMENTS
FUTURE POWER NEEDS
Summary of Changes
Forecast Methodology
Population and Economic Activity Forecast
Development Assumptions, 1975-2000
Development Assumptions, 2000-2025
Forecast Results
Utility Sector
National Defense Sector
Self-Supplied Industries Sector
Credit for Energy and Capacity
THE SELECTED PLAN
Power Capabilities
Seasonal Reservoir Operation
ECONOMIC ANALYSIS
Costs -The Base Case
Hydropower Benefits
Power Values and Alternative Costs
Natural Gas Alternative
Oil-Fired Alternative
Derivation of Power Benefits -The Base Case
Other Benefits
Recreation
Flood Control
Employment
Intertie
i
C-1
C-2
C-2
C-2
C-2
C-3
C-4
C-5
C-9
C-11
C-11
C-12
C-12
C-13
C-21
C-31
C-32
C-33
C-34
C-39
C-48
C-48
C-49
C-54
C-54
C-54
C-54
C-57
C-64
C-65
C-66
C-66
C-66
C-66
C-69
TABLE OF CONTENTS (cont)
Item
Plan Justification -Base Case
Sensitivity of Project Justification
Comparability Test
Alternate Discount Rates
Variations in the Load Forecast and Project Timing
Construction Delays
Alternate Investment Cost Estimates
Oil-Fired Thermal Alternative
Inflation
Fuel Escalation
Fuel Cost Assumptions
Test Results
Summary
Number
C-l
C-2
C-3
C-4
C-5
C-6
C-7
C-8
C-9
C-10
C-11
C-12
C-13
C-14
C-15
C-16
C-17
C-18
C-19
C-20
C-21
C-22
C-23
LIST OF TABLES
Title
Study Area Population as Percent of Total
Industry Employment Shares
Total Personal Income in Alaska
Alaska Economic Indicators
Summary of Existing Generating Capacity
Near-term Planned Reso~rces
Historical Net Generation
Development Assumptions
Population Estimates
Per Capita Use Projections
Self-Supplied Industry Sector Assumptions
Total Power and Energy Requirements
Anchorage-Cook Inlet Area Power and Energy
Requirements
Fairbanks-Tanana Valley Area Power and Energy
Requirements
Usable Capacity and Energy, Base Case
At-Site Power Capabilities
At-Market Power Capability
Annual Cost Computations
Cook Inlet Natural Gas Balance
Cook Inlet Natural Gas Reserves and Committments
1976 Alaska Gas Use
Manpower Expenditures
Intertie Capacity Benefits
i i
C-71
C-73
C-73
C-73
C-75
C-76
C-76
C-77
C-78
C-80
C-82
C-83
C-83
C-3
C-4
C-5
C-7
C-9
C-10
C-10
C-22
C-32
C-33
C-35
C-36
C-37
C-38
C-45
C-48
C-49
C-55
C-60
C-62
C-63
C-67
C-71
Number
C-24
C-25
C-26
C-27
Number
C-l
C-2
C-3
C-4
C-5
C-6
C-7
C-8
C-9
C-10
C-11
Number
C-l
C-2
Number
C-l
C-2
C-3
C-4
C-5
C-6
C-7
LIST OF TABLES (cont)
Title
Average Annual Costs
Average Annual Benefits
Plan Justification
Inflation Adjustment Multipliers
LIST OF FIGURES
Title
Load Forecast Comparison
Devil Canyon and Watana Unit Maximum Performances
Annual Head-Duration Curve, Watana Reservoir
Loads and Resources
Marketable Energy
Operating Levels, Watana Reservoir
Spill Frequency Diagram
Transmission Line Capacity Credit
Plan Justification Under Alternate Discount Rates
Sensitivity to Inflation and Escalation -Coal-Fired
Alternative
Sensitivity to Inflation and Escalation -Oil-Fired
Alternative
LIST OF PLATES
Ti tl e
Reservoir Operation and Energy Output, Watana
Reservoir Operation and Energy Output, Devil Canyon
EXHIBITS
Title
Load-Resource Analyses
Load-Resource Graphs
Usable Capacity Summary
Power Value Calculations
Power Benefit Calculations
Investment Cost Calculations
Correspondence
; i i
C-72
C-72
C-72
C-79
C-11
C-42
C-43
C-46
C-47
C-51
C-53
C-70
C-74
C-84
C-85
SUMMARY OF CHANGES
This section updates benefit calculations and the determination of
the project's economic justification presented in the 1976 Interim
Feasibility Report. Economic trends and power usage continue to indi-
cate that significant amounts of new generation will be required in
the railbelt area of southcentral Alaska. A new load forecasting
methodology and the three additional years of historical data result
in slightly decreased peak load projections. The estimated costs of
both the hydroelectric project and the coal-fired alternative have risen
significantly since 1975. Under the base case set of assumptions,
hydroelectric development in the upper Susitna River basin continues
to appear economically justified. The 1978 updated benefit-cost ratio
of the proposed development is 1.4 compared to the earlier estimate
of 1.3.
C-l
STUDY AREA ECONOMY
SUMMARY OF CHANGES
The economic base analysis presented in the 1976 Interim Feasibility
Report was based on the market area's economic performance through 1974.
Fears of a severe post-pipeline depression in Alaska have been largely
dissipated by the slJstained performance of the State's economy in the
2 years since the pipeline phased down in 1976. In 1977. higher pro-
duction levels were reached in the forest products, fisheries, and
agricultural industries when compared to 1976. The State's financial
institutions reached record high levels in 1977 in deposits, loans.
and total assets. In addition, more houses and commercial and indus-
trial buildings were constructed in 1977 than during any previous year.
In fact, by excluding contract construction employment (under which
pipeline workers were classified), there appears to have been a net
increase in 1977 of 1,500 nonagricultural jobs in Alaska.
INTRODUCTION
The discussion that follows both augments and updates the economic
base analysis of the 1976 report. It is based on three primary sources.
One is a detailed analysis of the southcentral Alaska economy between
1965 and 1975. This work was done by the Institute of Social and
Economic Research of the University of Alaska for the Southcentral
Level B Study. Two other reports, one by the State's Department of
Commerce and Economic Development and the other by the Department of
Labor, provide information on the performance of the economy since
1975. Some of the population and income estimates through 1974 presented
here differ from the estimates reported in the 1976 Interim Feasibility
Report. These differences result from recent efforts by the State and
others to develop a consistent data base.
HUMAN RESOURCES
The rapid economic growth in the Railbelt area of Alaska and in
Alaska as a whole has resulted in substantial immigration of people
seeking jobs in the Alaskan economy. Table C-l summarizes population
growth in the study area and in the state as a whole.
C-2
TABLE C-l
STUDY AREA POPULATION AS PERCENT OF TOTAL
Year Total Alaska Stud~ Area Percent of Total
1960 226,167 149,186 66
1970 302,361 209,178 69
1973 330,365 234,768 71
1974 351,159 245,846 70
1975 404,634 290,522 72
1976 413,289 301,250 73
Source: State of Alaska Department of Commerce and Economic
Development, The Alaskan Econom~, Year-End Performance
Report 1977.
There are two major economic motivating factors which explain the
large population increase. One is the fact that real incomes have
been rising in Alaska faster than the rate in the U.S. as a whole.
This is an indication that Alaska has been a region of improving economic
opportunity in comparison to nationwide averages. In addition, indi-
viduals see explicit opportunities in the growth in employment. 1/
The Alaska Department of Labor estimates that net migration accounted
for a 73,000 increase in resident population between 1970 and 1975,
about 72 percent of the increase, while natural increase accounted for
only 29,000, or about 28 percent of the total.
EMPLOYMENT
Employment shares of major industrial categories are presented in
Table C-2. As can be seen, some significant changes in employment
percentages have taken place over the past 5 years. In 1973, govern-
ment claimed by far the largest share (38 percent) of total employment
with services and retail trade a distant second at 14 percent. By 1978,
Government's share declined to 30 percent. Manufacturing is the only
other sector to show a significant decline -its share drops from 8.5
percent to 7 percent. Mining, construction, and services show the
largest gains.
1/ Institute for Social and Economic Research, University of Alaska,
Southcentral Alaska's Economy 1965-75, draft report.
C-3
TABLE C-2
INDUSTRY EMPLOYMENT SHARES
(Percent)
Industry
Mining
Manufacturing
Government
Construction
Retail Trade
Wholesale Trade
Finance, Insurance and
Real Estate
Transportation
Communications
Pu b 1 i c Ut i 1 it i es
1973
1. 79
8.50
37.75
7.09
13.60
3. 10
3.86
2.40
2.40
0.92
1978 (Projection)
3.06
7.11
30.49
10.02
14.02
3.40
4.87
2.46
2.46
0.78
Source: Alaska Department of Labor, Alaska Economic Outlook
to 1985, July 1978.
Data for 1977 indicates that while the mid-year completion of the
trans-Alaska oil pipeline had an impact on the State's economy, it has
not been as severe as expected. As a result of the large decrease in
contract construction employment, total nonagricultural employment
declined accordingly. The decline in nonagricultural employment,
however, was less than that of contract construction, indicating a
previously unexpected economic stability.
PERSONAL INCOME
Total personal income is defined as the sum of wage and salary
income, proprietor's income, dividends, interest and rental income,
and transfer payments. Subtracted from this are personal contributions
for social insurance. Once total personal income is compiled, it is
then adjusted by the residency of the worker.
From statehood in 1959 through 1973, there has beerr stable growth
in the State's personal income, paralleling the national trends.
Alaska's per capita income estimate increased 86 percent from $2,498
C-4
in 1959 to $4,644 in 1970 while the U.S. average rose 83 percent from
$2,167 to $3,966 respectively during this same time period. This
trend continued through 1973 with Alaska's per capita income rising
an additional 28 percent while the national level rose 27 percent.
Since 1973 per capita income in Alaska has demonstrated a phenome-
nal rate of growth. In 1974 it increased 17 percent to $7,117 while
in 1975 the reported increase was 33 percent to $9,440. During 1976
the annual rate of increase slowed considerably to 10 percent, boosting
per capita income to $10,415. Correspondingly, on the national level
it increased 9 percent in 1974, 8 percent in 1975, and 9 percent in
1976.
Clearly, Alaska's resident personal income has increased substan-
tially the past few years. The State's economy has received a tremen-
dous boost from construction of the oil pipeline, Native land claims,
outer continental oil development, and government expenditures. With
the completion of the oil pipeline, personal income of Alaskans is
initially declining in real terms. As additional projects come on
line in the future, the rate of growth in real personal income will
again turn positive.
TABLE C-3
TOTAL PERSONAL INCOME IN ALASKA, 1970-1977
Year
1970
1971
1972
1973
1974
1975
1976
1977
Personal Income
(In billions of $)
1.3
1.5
1.6
1.9
2.4
3.3
3.8
3.9
Source: Alaska Department of Commerce and Economic Development,
The Alaska Economy, Year-End Performance Report 1977.
AGGREGATE ECONOMIC PERFORMANCE
It has generally been assumed that there existed a direct cause
and effect relationship between pipeline construction and the State's
C-5
economic expansion. Preliminary data for 1977 indicate that while
pipeline construct"ion employment declined during the year, it did not
trigger massive layoffs in other nonpipeline sectors of the State's
economy. Indeed, even with an annual average loss of 11,300 construc-
tion workers, total employment in Alaska for 1977 declined by only
about 9,700 workers, or less than 6 percent, from the historic high
level in 1976. Refer to Table C-4.
Obviously, there have been other factors which have contributed
significantly to the State's recent economic expansion. By the end of
September 1977, over $348 million had passed through the Alaska Native
Fund to the Native corporations. Of this amount, a considerable por-
tion had been invested in Alaska businesses and industry. In addition,
public sector expenditures by Federal, State, and local governments
have demonstrated dramatic increases in recent years, and mineral
expioration activity has continued at a strong pace. These and other
sources of nonpipeline economic stimulation have occurred during the
pipeline construction time period and they appear to have played a
significant role in expanding and strengthening Alaska's economy.
The forest products industry, after considerable expansion in 1976
from the previous depressed levels, maintained a stable high level of
activity in 1977. Pulp and lumber production remained constant in
1977 although the production of wood chips declined significantly as
a result of world market conditions. Japan, the major purchaser of
Alaska's forest products, continues to be hampered by the slow recovery
of its national economy, especially in its residential housing sector.
The State's commercial fisheries industry greatly surpassed all
expectations during 1977. The salmon harvest was the highest since
1970 with strong returns of pink salmon to the southern portion of
southeast Alaska and with good returns to most other areas of the
State. Generally, the shellfish harvest and prices paid to fishermen
were higher than in 1976.
As a result of the overall increases in 1977's fin and shellfish
harvest, higher employment levels were stimulated in the State's fish
processing sector.
Investment in hard rock mineral exploration increased substantially
during 1977 to an estimated record high of $60 million. Oil exploration
continued with 33 wildcat and step-out wells drilled in 1977, represent-
ing nearly a threefold "increase "in activity over the 1976 total. Major
oil discoveries were announced in 1977 at Point Thompson and Flaxman
Island (located east of Prudhoe Bay), indicating the possibility of
additional North Slope oil and gas fields of significant scale. In
October 1977, the Lower Cook Inlet lease sale was held in Anchorage.
C-6
n
I
'-J
TABLE C-4
ALASKA ECONOMIC INDICATORS
.
1970 1971 1972 1973 1974 1975 1976
Resident Population (000) .. · · 302.4 312.9 324.3 330.4 351.2 404.6 413.3
Civilian Labor Force #(000) .• · 87.2 92.9 98.6 103.8 119.5 148.5 158.0
Employment #(000) . . . . · . . . 81.1 85.4 90.5 95.2 11 O. 3 138.5 145.0
Nonagricultural Employment (000). 92.5 97.6 104.2 109.9 128.2 161. 3 171. 7
Number Unemployed #(000). · · · 6.0 7.5 8.0 8.6 9.2 10.0 13.0
Wage & Salary Payments ($000,000) . · $1 ,253 $1 ,359 $1 ,471 $1,621 $2,167 $3,449 $4,247
Resident Personal Income *($000,000). $1,412 $1 ,563 $1 ,698 $2,006 $2,429 $3,443 $3,979
Anchorage CPI (1967 = 100). · · · . · 109.6 112.6 115.9 120.8 133.9 152.3 164.1
Percent Change in CPI . . · · . · 3.5 3.0 2.7 4.2 10.9 13.8 7.8
N.A. = Not Available
e = Estimate
# = Current Population Survey Basis
* = Place of Residence Basis
Source: Alaska Department of Commerce and Economic Development, The Alaska Economy, Year-End Performance
Report 1977.
1977e
N.A.
158.9
136.4
162.0
20.5
$3,737
$4,000
175.7
7. 1
Although drilling results in the Gulf of Alaska have been disappoint-
ing to date, other oil and gas exploration activities are continuing
on the National Petroleum Reserve Alaska (old PET-4) and on Native
corporation lands.
C-8
PRESENT AND HISTORICAL POWER REQUIREMENTS
This section presents the existing and planned generating capacities
of the railbelt area as of 1977 along with generating resources that
are planned for the near future. Also shown are the historical net
generation estimates through 1977.
TABLE C-5
SUMMARY OF EXISTING GENERATING CAPACITY
Installed CaQacitt (MWl
Gas Steam
Ht dro Diesel Turbine Turbi ne Total
Anchorage-Cook Inlet Area:
Util ity System 45.0 27.5 435.1 14.5 522. 1
National Defense 9.2 40.5 49.7
Self-Supplied Industries 11 .3 15.2 37.5 64.0
SUBTOTAL 45.0 48.0 450.3 92.5 635.8
Fairbanks-Tanana Valley Area:
Utility Systems 35. 1 203.1 53.5 291 .7
National Defense 14.0 63.0 77 .0
SUBTOTAL --0 49.T 203.1 116.5 368.7
TOTAL 45.0 97.1 653.4 209.0 1004.5
Source: Alaska Power Administration, "Power Market Analysis," January
1979. Anchorage-Cook Inlet figures include the Valdez-
Glennallen area which totals 56.8 MW.
The total 1977 installed capacity of 1,004.5 MW represents a 45
percent increase over the 692 MW of installed capacity that existed
in 1974.
C-9
TABLE C-6
NEAR-TERM PLANNED RESOURCES
Installed Ca~acit~ (MW}
~-----.-Gas Steam
Year Turbine Turbine Total
Anchorage-Cook Inlet
Utilities 1978 66.7 66.7
1979 113.7 113.7
1980 100.0 100.0
1981 18.0 18.0
1982 100.0 100.0
1984 18.0 400.0 418.0
SUBTOTAL 416.4 400.0 816.4
Fairbanks-Tanana Valley
Utilities 1982 104.0 104.0
TOTAL 416.4 504.0 920.4
Source: Ba ttell e Pacifi c Northwest Laboratori es, "A 1 askan El ectri c
Power: An Analysis of Future Requirements and Supply Alter-
natives for the Rai"'belt Region," March 1978.
TABLE C-7
HISTORICAL NET GENERATION (GWH)
Anchorage-Cook Inlet Area Fairbanks-Tanana Valley Area
Year Util Nat. Oef Indu Util Nat. Def Indu Total
1970 744. 1 156.2 1.7 239.3 203.5
1971 886.9 161. 2 25.0(e)1I 275.5 201. 4
1972 1,003.8 166.5 45.3 306.7 203.3
1973 1 , 1 08. 5 160.6 45.3(e) 323.7 200.0
1974 1 , 189. 7 155. 1 45.3 353.8 197.0
1975 1,413.0 132.8 45.3(e) 450.8 204.4
1976 1,615.3 140.3 45.3(e) 468.5 217.5
1977 1,790.1 130.6 69.5 482.9 206.8
l! (e): estimated industrial load, revised by APA, January 1979.
Source: APA, Upper Susitna Project Marketability Analysis,
November 1978.
C-l0
1 ,344.8
1,550.0
1,725.6
1,838.1
1,940.9
2,246.3
2,486.9
2,679.9
FUTURE POWER NEEDS
SUMMARY OF CHANGES
The forecasted demand for electrical power presented in this section
constitutes a downward revision from those estimates used in the 1976
Interim Feasibility Report. The cumulative changes are due to the use
of a different forecast methodology, 3 additional years of historical
data, and generally more conservative economic development assumptions.
The extent of change in the forecasts, however, is not great. For
instance, the midrange forecast of peak load for the year 2000 has been
revised to 2,852 MW, a 10 percent decrease from the earlier estimate
of 3,170 MW (refer to Figure C-l). The most noticeable change occurs
in the high range forecast which was reduced 36 percent in the year 2000.
Additionally, the revised forecast has been extended an additional
25 years to 2025 in order to facilitate longer range planning.
)000
Figure C-I
LOAD FORECAST CONPARISON
(Medium Grow·th)
/
/ .'
/
/
/.' .
'i 2000 1975 FORECAST /
6
Q
c:{
o
...J
~
<[
LU
/."
/ .. '
,/' •• '1978 FORECAST
,/' .. '
,/'.' .
,/'" ..
0.. 1000 /"" ...
,../ .. '
/"" .. '
/ .. ' ,p"
~'HISTORIC
O~-r----------~------'----r----------r---------,--______ ___
1974 I ~ 110 90
TIME IN YEARS
C-11
FORECAST METHODOLOGY
The Alaska Power Administration (APA) has used a simplified end-use
model to forecast future power requirements, augmented by trend analysis
and an econometric model. Total power demand has been categorized into
three primary end uses: the residential/commercial/industrial loads
supplied by electric utilities, the national defense installation sector,
and the self-supplied industrial component.
Those factors in each category that best explain historical trends
in energy use were identified. In the utility sector, those explanatory
variables are population and per capita use. Population was forecasted
with the help of a committee of experts using a regional econometric
model, while per capita use estimates are an extrapolation of past
trends adjusted to account for anticipated departures from those trends.
National defense needs are assumed to depend on the level of military
activity and the number of military personnel in the study area. Future
self-supplied industrial power requirements are based on explicit assump-
tions regarding future economic development and the energy needs associa-
ted with such development.
POPULATION AND ECONOMIC ACTIVITY FORECAST
The most important sector in terms of magnitude of electrical
energy use is the utility sector, and population is the key factor in
this sector's future power requirements. Population forecasts in turn,
are highly dependent upon assumptions of future economic activity.
Economic activity assumptions are also important because they have a
direct impact on energy requirements in the self-supplied industrial
sector.
The population and economic activity assumptions used in this fore-
cast are based on a draft report of the Economics Task Force, South-
central Alaska Water Resources Study, dated September 18, 1978. The
report is entitled, Southcentra1 Alaska's Economy and Popu1ation,_
1965-2025: A Base Study and Projection.
The report was a joint effort of economists, planners, and agency
experts who were members of the Economics Task Force of the Southcentra1
Alaska Water Resources Study (Leve1 B), being conducted by the Alaska
Water Study Committee, a joint committee of Federal and State agencies,
the Alaska Federation of Natives, the Alaska Municipal League, the
Municipality of Anchorage, the Southcentra1 region borough governments,
and regional Native corporations.
The projections repol~ted relied on two long-run econometric models
devised by economists from the University of Alaska Institute of Social
C-12
and Economic Research and from the MIT-Harvard Joint Center for Urban
Studies. Funding was provied by the National Science Foundation's Man
in the Arctic Program (MAP). The two specific models used here were
modifications of the Alaska State and regional models developed under
that program. The models produced estimates of gross output, employ-
ment, income, and population for the years 1975-2000. Population and
employment were disaggregated and extrapolated to the year 2025 by ISER
researchers under Economics Task Force direction, and using Task Force
concensus methodology. The data required to run the model were provided
by various members of the Economics Task Force, the assumptions were
reviewed by the Task Force, and the model outputs and tentative pro-
jections were reviewed for internal consistency and plaus'ibility by
ISER researchers and by the Task Force.
The use of the econometric model requires a set of assumptions
related to the level and timing of development. The assumptions pri-
marily consist of time series on employment and output in certain of
the export-base industries and in government. Because of the importance
of these assumptions to the electrical energy load forecast, they are
presented here in full on pages C-13 through C-31 from the Economic
Task Force Report.
Assumptions Used to Produce Economic and Population Projections, 1975-
2000
The critical assumptions are organized into two scenarios which
consist of all low-range assumptions taken together and, alternatively,
all high-range assumptions taken together. The scenarios were intended
to show a "reasonable" high and reasonable low development series of
specific projects which together would offer about the broadest range
of employment and population outcomes which could be foreseen. This
does not mean that the Task Force predicts that all or any of the
projects assumed will actually occur; on the contrary, there is a highly
variable degree of uncertainty with respect to the level and timing of
all developments in the scenarios. However, some projects were subjec-
tively rated more likely than others, some unlikely, and some very
unlikely. Task Force consensus assigned most of the more likely projects
to the low development scenario, some of the less likely to the high
development scenario, and the remainder were assumed not to occur within
the time horizon of the study.
The resulting low and high scenarios should not be considered synonyms
for the terms "minimum" and "maximum" development. The Task Force did
not feel competent to say what the theoretical minimum or maximum
possible level of economic development in Southcentral Alaska might
be, since this could be influenced by Government policy at Federal,
State, and local levels and by market developments beyond the power
of anyone to predict at this time; nor would that exercise have been
of much use to planners.
C-13
The assumptio:cs are organized by industry and discussed in the
following sections.
Agriculture: Agriculture is currently a marginal industry in Alaska,
employing about 1,000 people statewide (depending upon the definition
of part-time, family help, and proprietors). In southcentral Alaska,
about 115 man-years per year are expended in agriculture. Under a
set of very favorable public policy decisions and favorable markets,
considerable further development might occur. PY'imary requirements
include: public priority given to agricultural production in Alaska
at the same level as petroleum, minerals, and marine products; active
pursuit of statutes and programs to reserve and preserve agricultural
lands; and public aid to innovative settlement and development techniques.
In this case, the agricultural experts on the Task Force could foresee
possible commercial agricultural employment of around 800 man-years in
southcentral Alaska per year, and about 4,600 statewide by the year
2000, rising to 6,900 by 2025. This reflects the current emphasis on
development of the Tanana Valley, rather than the southcentral area.
Total statewide sales of agricultural products in the high case rise to
about $400 million (1975 dollars) per year in the year 2000, and to
about $500 million in 2025. Value of output in constant 1958 dollars
rises to $51 million by 2000, about $8.5 million from southcentral. By
the end of the study period in the high case, about 1.06 million acres
would be cultivated for crops, and 5.2 million acres of range land
utilized. (Currently, about 20,000 acres are used for crops and grass
in the State, about 12-13 thousand in southcentral.)
In the low case, public priority is given to "national" and "public"
interest in esthetic, recreational, subsistence, and wilderness values,
tending to reduce the amount of land available for crops and reducing
the access and usability of land for agriculture. In addition, public
agricultural agencies and institutions which support agriculture are
allowed to atrophy. In this case, and with market conditions continuing
to be unfavorable to Alaskan agriculture, the southcentral industry out-
put and commercial employment drops to zero as the land is subdivided
for homesites and recreational use. Value of commercial output drops
to zero by 1991, with only "amenity" (part-time, partly subsistence)
output remaining.
Forestry: Aggregated in State statistics under Agriculture-Forestry-
Fisheries, this is a tiny sector which employs about 22 people statewide.
Virtually all employment in logging occurs in lumber' and wood products
manufacturing. Value added is likewise negligible. In the high case,
this sector grows in proportion to growth in lumber and wood products.
In the low case. it stays at current levels.
C-14
Fisheries: The fisheries sector primarily consists of persons
actually engaged in fishing, but it is troublesome for several reasons.
It is difficult to count fishermen since this is an industry in which
proprietors do much of the work, often with unpaid family help, the
work is seasonal in nature, and many out-of-state persons take part.
This causes the State's employment statistics, based on employment
covered by unemployment insurance, to be misleading. Likewise, multiple
licenses and unfished licenses make fisherman licenses a misleading
indicator. Area-of-catch statistics collected on fish landed in Alaska,
together with independent data on crew size, by gear type, give a
pretty good picture of total persons actually engaged in fishing. For
southcentral Alaska (but including the Aleutian chain), annual average
employment on this basis is about 2,000 persons, while it was 4,359
statewide in 1975. In the high case, it is assumed that in existing
fisheries, expansion of fishing productivity would be offset by 1 imited
entry and 1 abor-savi ng improvements in the fl eet, 1 eaving employment
constant at existing levels despite a fourfold increase in the salmon
catch. However, given very favorable conditions, major development of
the American trawl fishery off Alaska's coast could result in 100 per-
cent replacement of the foreign fishing effort inside the 200-mile limit
by the year 2000, employing about 17.5 thousand persons in fishing state-
wide and 8.7 thousand (or 50 percent) in southcentral. This was consid-
ered to be a very speculative development; consequently, no bottomfishing
development was considered in the low case, while existing fisheries
just maintained current employment.
Output level of existing fisheries in the high case expands consider-
ably, since the State is assumed to undertake an aggressive hatchery
and habitat improvement program, together with the 200-mile economic
zone. The combined effect is assumed to be a quadrupling of salmon
catch, while shellfish remain at about existing levels. The expansion
of the trawl fishery was assumed to result in a southcentral catch of
1.85 billion pounds per year, worth $361 million exvessel in the high
case. In the low case, all fisheries maintain their approximate 1975
1 evels.
Mining, Including Oil and Gas: The mining sector is dominated by
employment and output in oil and gas, with lesser amounts in coal,
sand, and gravel, and a few persons engaged in precious metal exploration
and extraction. For the State as a whole, oil and gas developments are
expected to dwarf all other considerations in this industry. Within
southcentral Alaska, an important local issue is the development of
the Beluga coal field.
The developments in mlnlng in the high case are assumed to be as
follows: There is a small find of hydrocarbons in the Northern Gulf of
Alaska, but no important production. If the mean expected reserves are
C-15
found, peak production would be about 932 thousand barrels of oil per
day in 1985, and peak gas production of 0.5 billion cubic feet per day
in 1987. The Sadlerochit, Kuparuk River, and Lisburne formations at
Prudhoe Bay all combine in the high case for a 1,785 million barrels/
day flow of oil in 1985. In addition, the joint State/Federal offshore
lease sale is assumed to contain oil and gas resources equivalent to
total reserves of 1.9 billion barrels. There are also two lease sales--
in the Northern Gulf of Alaska (Sale 55) and Western Gulf/Kodiak area
(Sale 46)--which result in moderate sized oil finds. Peak oil produc-
tion in the Northern Gulf is about 0.550 million barrels per day in 1986,
and 0.515 million barrels per day in 1992 in the Western Gulf. Daily
gas production peaks at 1.0 bcf/day in the Northern Gulf and 0.26 bcf/
day in the Western Gulf. Coal production in the high case would begin
in 1983, with full-scale mining of 730,000 tons of coal per year by
1984 to feed a mine-mouth powerplant, twice that amount by 1986 to feed
a second plant, and development of 6 million tons/year exports by
1990. In the high case, employment peaks at slightly over 9,000 in
1984, subsequently declining to 8,200 in 1995, while output rises to
$3.2 billion (constant 1958 dollarsl/), tail"ing off to $2.6 billion.
Low case oil and gas development basically consists of development
at or around Prudhoe Bay. There is exploration in all the areas noted
in the previous case, but exploration turns up far fewer prospects
worth developing. While the Kuparuk and Lisburne are developed in this
case and there is a joint offshore sale, the Beaufort sale turns up
only 0.8 billion barrels of reserves instead of 1.9 billion. The lower
Cook Inlet turns up only a small find, while the northern and western
regions of the Gulf of Alaska are dry and result in "exploration only"
,employment. Beluga coal is not developed in the low case. As a result
of all this, statewide peak employment in mining rises to about 7,000
in 1984, dropping to less than 4,800 by the end of the century.
Within the region, exploration plus development of oil and gas
employ almost 4,800 persons by 1984 in the high case, declining to
almost one-fourth that number by 1993. Beluga coal adds about 220
workers by 1990 5 the first year of coal export. In the low case, the
peak employment is only 2,700 persons -in 1984, the peak year, declines
sharply thereafter, and levels off at 1,200 after 1987.
Food Manufacturing: The food manufacturing industry in Alaska is
dominated by seafood processing, a situation which i~ not expected to
change in the near furure. In the high case, the projected fourfold
increase in the output of the salmon fisheries implies about a doubling
l/ The 1958 base year was used for convenience since U.S. Department
of Commerce estimates of gross product were in terms of 1958 dollars
when the study began.
C-16
in employment required to process the salmon. Since it was the con-
sensus of the Task Force that shellfish are at or near maximum sustained
yield, the overall processing plant employment for existing fisheries
is projected to increase about 25 percent. Also in the high case, by
the year 2000 the 100 percent replacement of foreign bottom fish effort
off Alaska results in a catch of 3.7 million metric tons per year,
requiring estimated total processing employment of about 12,000 and
short-term (5-month) seasonal employment of 21 ,211--for an annual
average of 21,000 by 2000. However, we assumed that only about one-third
of total catch would be processed in Alaska shore-based facilities,
resulting in total Alaska shore-based employment of 3,759, half of
whom are employed in southcentral, and affect the local economy. The
remainder of the 21,000 work on processing vessels near shore and off-
shore. but their incomes probably would affect the Anchorage economy
and the statewide economy to some degree. Output for this industry
was estimated by taking the expected exvessel value and using the historic
ratio of exvessel to wholesale value, and the ratio of value-added to
wholesale value. In the high cases, the value of catch in existing
fisheries was assumed to rise at the same rate as total catch, yielding
$145 million in value added in 2000, while catch in the emergent trawl
fishery was assumed to rise to $722 million (3.7 million metric tons),
yielding about $167 million of value added in processing (all value
added in constant 1958 dollars). In the low case, a growth rate of
1 percent per year was projected for total output, yielding $81.5
million per year val~e-added by 2000.
Lumber and Wood Products Manufacturing: The two critical assumptions
for this industry are the annual cut of timber in the State, determined
mostly by Forest Service allowable cut and Japanese market conditions,
and whether any dimension sawmills are built in Alaska. In the high
case, the annual cut by the year 2000 was assumed to be 1,260 million
board feet (probably partly from Native lands), compared with 660
million in 1970. In the low case, the increase is to only 960 million.
No new mills are built in either case. While not exactly proportional,
the increase in employment is similar: in the high case, statewide
employment rises to 3,834 from 2,176 in 1975; in the low case, the rise
is from 2,176 to 3,280. The output of this industry was estimated by
calculating the 1975 ratio of output per employee. This was assumed
to escalate at its 1965-1975 rate of growth in the high case (about
1.66 percent), but stayed at 1975 levels in the low case.
Since almost all the prime timber likely to be exploited by an
expanding industry is located outside the southcentral region, we
assumed that outside of Anchorage, the employment of firms in this
sector would escalate by about 1 percent per year in the low case, by
2.3 percent per year in the high case, which is about the same or less
than the statewide rates. Employment was assumed constant in Anchorage.
C-17
Pulp and Paper M~nufacturing: The growth in this sector is determined
by most of the same factors as lumber and wood products. In neither
case is there a pulp mill built in southcentra1 Alaska, so there is no
employment or output in this sector within the region. In the State,
the increase in total cut results in average employment increases of
about 1.6 percent per year in the low case, 1.8 percent per year in
the high, resulting in totals of 1,777 and 1,886, respectively. In
the low case, productivity per worker remains at its 1975 value; in
the high case, it increases at 2.76 percent annually, its 1965-1975
rate, resulting in value added of $88.2 million and $93.6 million,
respectively, in the year 2000.
Other Manufacturing: This sector is an odd mixture of a wide variety
of cottage industries, printing and publishing, and consumer goods
manufacture, together with a few major petrochemical plants and refin-
eries. The major possible sources of new employment in this sector were
assumed to be the Alpetco royalty oil refinery-petrochemical complex,
Alaska Pacific LNG plant, and whatever other LNG or gas treatment
facilities might be associated with gas output from lower Cook Inlet
and the Gulf of Alaska. In the high case, the total operating employment
of these facilities was about 2,000 persons (mostly working for Alpetco).
In the low case, the only source was Pacific LNG, employing about 60
persons. Statewide output in this sector was more of a problem since
it was unclear how much the output to be added by any of the LNG plants
might be. It was decided to subsume LNG value-added under mining, and
in the high case, value-added in other manufacturing was estimated as
the existing level of output, plus total revenues of Alpetco, minus
cost of feedstocks, from the A1petco pro forma financial projections
of March 10, 1978. All the growth was entered outside of Anchorage.
In the low case, the existing level of output was used.
Construction: For modeling purposes, it was only necessary to
estimate total employment working on major projects exogenous to the
economy, since the rest of construction is projected with the support
sector and output is determined by employment in this sector in the
models. In the high case, the significant projects within the region
were assumed to be oil treatment and shipment facilities in the Gulf
of Alaska and Kodiak subregions and the Kenai-Cook Inlet Census Division,
small LNG facilities associated with the Northern Gulf and lower Cook
Inlet development, a Beluga coal transshipment facility, Pacific LNG
and Alpetco plants, and a new State capital in Willow. Outside the
region, there is augmentation of TAPS pipeline capacity, the northwest
Alaska gas pipeline is constructed, and field development facilities
are projected for the Beaufort Sea and the Kuparuk and Lisburne form-
ations. Statewide, total exogenous construction employment peaks at
a total of about 14,000 in 1981, declining rapidly thereafter to less
than 1,000 by 1991. In the region, the peak employment is a bit less
than 7,000 in 1981.
C-18
The level of construction employment was considerably less in the
low case, both because of fewer developments in oil and gas, and because
several projects needing State support do not occur, e.g, Alpetco and
the State capital move. In this case, the northwest Alaska pipeline
is constructed, but the oil finds at Prudhoe Bay offshore areas are
relatively small, as are those in lower Cook Inlet. The Kuparuk and
Lisburne formations are developed, and the Pacific LNG plant is built.
However, there is no new substantial augmentation to fish processing
in the form of new plants to process bottom fish. In the low case, state-
wide peak employment in exogenous construction is about 9,500, while
in the region it is about 1,800.
Federal Government: Federal Government employment has been growing
very little over the last 10 years, with civilian increases about offset
by decreases in military employment. The rate of civilian increase has
been about 0.5 percent per year, and lacking the boost of any massive
developments requiring Federal support, and lacking a new State capital,
the likely rate of increase in Federal civilian employment for the low
case is assumed to remain at 0.5 percent, increasing employment from
18,000 to 21,000 statewide, and from 10,900 to 12,250 in the region by
2000. In the high case, general development results in a doubling of
the average rate of increase to about 1 percent per year in Federal
Government in most of the State, and 1.2 percent per year in south-
central to reflect the State capital move. This increases statewide
Federal civilian employment from 18,000 to 22,000, and regional employ-
ment from 10,900 to 14,500. Federal military employment is assumed to
remain constant at 1975 levels in both the State and region.
State Government: State Government employment went through several
revisions because of concern about State budgets. Historically, the rate
of growth in this sector averaged 8.5 percent per year, a rate which
most Task Force members believed was unlikely to continue. On the other
hand, in the high case bottomfish development, major oil development,
and the moving of the State capital to Willow were likely to result in
fairly substantial increases in State employment. In the high case,
it is assumed that 2,750 positions were transferred from Juneau to
Willow and that total State Government employment would increase from
14,700 to about 39,000 in the year 2000, declining from around 7.6
percent of civilian wage and salary employment to about 7.2 percent.
In the region, State employment bulks fairly large because of the State
capital move, with the total from Anchorage and other southcentral
combined moving from 5,400 to 14,900, or from 5.2 percent to 13.1 per-
cent of total ernp 1 oyment.
In the low case, it was assumed that government growth was restricted
by lower development needs, by funding constraints or public opinion,
and by the fact that the State capital did not move. Before 1985, State
Government employment growth was held to about 2 percent per year, with
C-19
zero growth thereafter. State employment as a result goes from 14,700
in 1975 to 19,159 in 2000, about 6.4 percent of civilian employment in
the latter year. In the region, total State employment rises from 5,400
to 7,140 in 1985-2000, about 6.1 percent of civilian employment in 1975
and 3.1 percent in the year 2000.
Local Government: Local government was assumed to be influenced in
the future by many of the same factors influencing the rate of growth
in State employment. The historic rate from 1965 to 1975 was 10.5 per-
cent (10.1 percent in southcentral), partly a result of development of
school systems and the transfer of State-operated rural schools in the
unorganized borough to local control. Due to increasing numbers of
functions being performed at the local level and rural development in
the high case, statewide growth was expected to be faster than in
southcentral, where local governments are already well organized. Due
to the moving of the State capital and due to local government response
to fishing and oil, local government employment was projected to sustain
about a 4 percent per year growth rate outside the region and about 3.4
percent within the southcentral region. This meant a statewide increase
in local employment from 14,200 in 1975 to 34,900 in 2000. In the low
case, since the State capital does not move and State-local transfers
are expected to be sharply curtailed after 1985, the assumed rates of
growth are about 2 percent until 1985 and about 1 percent thereafter.
Total employment in local government goes from 14,200 in 1975 to 20,100
in 2000. Within the region, local government in the high case grows
from about 8,100 to about 18,600. In the low case, regional local
government employment grows from 8,100 to 11,300.
Miscellaneous Assum tions: In the model, Alaskan wage rates are
determine in most ln ustries as a function of Alaskan prices and U.S.
average weekly wages in the private econon~, deflated by the U.s.
Consumer Price Index for Urban Clerical Workers. (Both the latter
series are published by the Bureau of Labor Statistics.) Alaskan prices
are in turn determined as a function of U.S. prices and local demand
conditions, reflected by changes in employment. Finally, migration to
Alaska is calculated as a function of the change in employment oppor-
tunities and relative per capita income in Alaska, compared to the
rest of the country. In order to project a "high" and "low" scenario,
the economics Task Force reexamined the assumptions usually used to
run the model for impact-assessment purposes in Alaska and concluded
that "high" or "low" growth could occur because of movements of the
economy outside the State as well as inside the State. In particular,
the rates of growth of U.S. disposable personal income per capita (2.0
percent) and wages (1.2 percent) appeared a bit optimistic for the low
case. Therefore, in the low case, "pessimistic" forecasts by Data
Resources, Inc. were used: 1.0 percent per annum average increase in
real wages and 1.77 percent average increase in real disposable per-
sonal income per capita. These two changes had little influence.
C-20
Government expenditures other than wages and salaries directly
influence output in the construction sector. To avoid having to make
a series of complex assumptions of doubtful validity concerning govern-
ment capital spending programs, the Task Force assumed other Government
spending increased proportionately to Government employment.
Finally, the Task Force recognized that some of the service, pub-
lic utilities, and transporation employment in the southcentral area
would not be local-serving employment at all. Particularly, employment
in these sectors for Alyeska Pipeline Service Company and Beluga coal
extraction would be essentially exogenous to the local economy. Con-
sequently, an exogenous component was added for employment in these
three sectors to adjust for the employment by Alyeska and by Beluga.
These assumptions are summarized in Table C-8.
Assumptions Used to Estimate Employment and Populations, 2000-2025
The Task Force was charged with estimating total employment and
population after the year 2000, but the econometric models' results
were doubtful that far in the future. The Task Force instead developed
some educated guesses concerning the Alaskan economy in the post-2000
period, and these were used to extrapolate the year 2000 results to
2025.
Basically, the same methodology was used as above. The basic sector
employment was projected by individual industry, a relationship between
nonbasic and basic employment was assumed, and then a relationship
between population and employment assumed and projected.
Basic employmemt was projected as follows: Since there were no
significant additional prospects for oil development in southcentral
Alaska after 2000, this sector was assumed to stabilize at its year 2000
level, replacing old fields with some additional development. This
was true in both cases. Exogenous construction tends to follow oil
development, so it, too, was left at its year 2000 level. Federal
civilian employment continued to grow to serve the expanding post-2000
population; by 1.2 percent per year in the high case and 0.5-0.6 percent
in the low case. State and local government continued to grow at the
rates projected for their respective cases from 1975 to 2000, with
fairly rapid expansion in the high case, and virtually no expansion in
the low case. Agriculture continued to expand after 2000 in the high
case, with some significant opening up of lands. There was no post-2000
development in the low case. Since manufacturing of fish products,
lumber, wood, and pulp was assumed to fully utilize the available
resources (as in the high case}, or its growth was restricted by
external institutional market factors (as in the low case), the level
C-21
n
I
N
N
SECTORS
Exogenous
Construction
Employment
TABLE C-8
DEVELOPMENT ASSUMPTIONS
HIGH
1. Oil treatment and shipment facilities:
Gulf of Alaska
Kodiak
Kenai -Cook Inlet
2. Small LNG facilites in:
Lower Cook Inlet
North Gulf of Alaska
3. Beluga coal developed and tranship
facil ity
4. State capital built at Willow
5. ALPETCO built on Kenai Peninsula
6. Pacific LNG built on Kenai Peninsula
7. Northwest Gas Pipeline built
8. TAPS expanded
9. Facilties developed for Kaparuk and
Lisburne at Prudhoe Bay
10. Major Beaufort Sea oil discovery
11. Peak employment of 7,000 in 1981 in
Southcentral, 14,000 Statewide
LOW
Pacific LNG built on Kenai Peninsula
Northwest Gas Pipeline built
Facilites developed for Kaparuk and Lisburne
at Prudhoe Bay
Small oil find offshore
Peak employment of 1,800 in Southcentral,
9,500 Statewide
n
I
N
W
SECTORS
Agri culture
Employment
Agriculture
Va lue of
Output
Forestry
Employment
Forestry
Value of
Output
Fishery
Employment
Fisheries
Value of
Output
TABLE C-8 (cont)
HIGH
1. Major development: 800 man-years by
2000 in Southcentral, 4,600 Statewide,
6,400 by 2025
1. 1958 dollars: 8.5 million in Southcentral
by 2000, 51 million Statewide
1. Essentially none
1. Negligible increase
1. No increase in existing fisheries
2. 17,500 increase in bottom fishing
Statewide, 8,750 in Southcentral
by 2000
1. Salmon quadruples by 2000
2. No increase in shellfish
3. Bottom fish: 722 million 1958 dollars
Statewide by 2000, 361 million South-
central
LOW
Zero employment by 1990
Amenity only
Essentially none
Negligible increase
No increase in existing fisheries
No bottom fish development
No increase in salmon
No increase in shellfish
No bottom fish development
TABLE C-3 (cont)
n
I
N
SECTORS HIGH
Pulp and 1. Employment increases by 1.8% per year,
to 1,886 by 2000 Statewide Paper
Manufacturing
Employment 2. No employment in Southcentral
Pulp and
Paper Value
of Output
3. Value added of $93.6 million by 2000
1. Real output per employee grows at
2.76% Statewide
2. Employment does not grow in Southcentral
~ Outer 1. Dominated by petroleum industry
Manufacturing
Employment
2. Increases reflect employment by
ALPETCO, Pacific LNG, and two small
LNG plants
3. Total employment of 2,000
Other 1. Existing level, plus additons from
Manufacturing ALPETCO
Value of
Output
LOW
Employment increases by 1.6% per year, to 1,777
by 2000 Statewide
No employment in Southcentral
Value added of $88.2 million by 2000
Real output per employee remains constant
Only increase is for Pacific LNG, employing
60 people
Existing level of output
TABLE C-8 (cont)
n
SECTORS HIGH
Lumber 1. Annual cut by 2000 is 1,260 million
and Wood board feet
Products
Manufacturing 2. No new mills
Employment
3. Statewide rises to 3,834
4. Other Southcentral employment increases
2.3% per year
5. Employment constant in Anchorage
r.!v Lumber and 1. Real output per employee grows at
1 .659% per year ~ Wood Products
Value of
Output
Food 1. Fourfold increase in output of salmon
fisheries Manufacturing
Employment
2. Doubling of salmon processing employment
3. Existing fisheries plant employment
increases 25%
4. By 2000, 100% replacement of foreign
bottomfish effort
5. 3.7 million metric tons/year catch by
2000
LOW
Annual cut by 2000 is 960 million board feet
No new mi 11 s
Statewise rises to 3,280
Other Southcentral employment increases 1%
per year
Employment constant in Anchorage
Output per employee does not grow
Existing fisheries stay at existing levels
No bottomfish development
n
I
SECTORS
Food
Manufacturing
Employment
(cont)
N Food 0'\ Manufacturing
Value of
Output
Mining Oil
and Gas
Employment
TABLE C-8 (cont)
HIGH
6. Total processing employment of 12,000
by 2000
7. Short-term (5-month) processing employ-
ment of 21,211
8. Annual processing employment average of
21,000 by 2000
9. Total Alaska shore-based employment of
3,759, 1/2 in Southcentral
1. Existing fisheries value added (1958 $)
$145 million by 2000
2. Trawl fishery catch rises to 3.7 million
metric tons, $722 million, $167 million
value added in processing
1. Development of Kaparuk River sand and
Lisburne formation, 1.785 million
barrels/day in 1985
2. 1.0 billion barrels developed offshore
Prudhoe Bay
3. North Gulf of Alaska: .550 million
barrels/day in 1986
LOW
Growth at 1% per year for total output,$81.5
million per year value added by 2000
No enhancement of fisheries output
Development of Kaparuk River sands and Lisburne
formation
0.8 billion barrels developed offshore Prudhoe
Bay
No find in North Gulf of Alaska
n
I
N
"-.J
SECTORS
Mining Oil
and Gas
Employment
(cont)
Value of
Hard Mineral
Production
TABLE C-8 (cont)
HIGH
4. West Gulf/Kodiak Area: .515 million
barrels/day in 1992
5. 1.0 BCF/day gas production in North
Gulf of Al aska
6. .26 BCF/day gas production in West
Gulf/Kodiak Area
7. Coal production begins in 1983:
730,000 tons/year by 1984 to feed
mine mouth plant; 1,460,000 tons/year
by 1986 to feed second plant; 6 million
tons/year exports by 1990
8. 9,000 employed in 1984 Statewide
8,200 employed in 1995 Statewide
9. North Gulf of Alaska: 932,000 barrels
of oil per day by 1985, 0.5 billion
cubic feet per day in 1987
10. 4,800 employed regionwide by 1984,
declining thereafter
11. 220 employed by Beluga coal by 1990
1. Present levels plus output of Beluga
coal
LOW
No find in West Gulf/Kodiak Area
No gas production in North Gulf of Alaska
No gas production in West Gulf/Kodiak Area
No Beluga coal development
7,000 employed in 1984 Statewide
4,800 employed in 2000 Statewide
2,700 employed in 1984 regionwide
declines sharply thereafter
Present levels
n
I
N ex>
SECTORS
Value of
Oil and Gas
Production
Federal
Government
Employment
Total Local
Government
Employment
Total Local
and State
Government
Expenditures
TABLE C-8 (cont)
HIGH LOW
1. Production is multiplied times estimated Production is multiplied times estimated
2.
l.
2.
l.
2.
3.
4.
l.
wellhead values of $17.00/bbl ($1.80/MCF 1/ wellhead values of $7.50/bbl (l.40/MCF for
for gas), new fields only in Southcentral -gas), new fields only in Southcentral l!
Prudhoe and other North Slope production
starts at $5.32/bbl and 25¢/MCF in 1977,
with oil rising to $29.28 by 2000 l!
Rises at 1.2% per year in Southcentral,
10,857 to 14,500 by 2000
Rises at 1% per year outside Southcentral
4% growth rate outside the region
3.4% growth rate within Southcentral
region
Statewide increase from 14,200 to 34,900
in 2000
Southcentral region increase from 8,100
to 18,600
Proportional to increase in wages and
salaries of Government workers
Prudhoe and other North Slope production
starts at $5.20/bbl and 25¢/MCF in 1977,
with oil rising to $29.28 by 2000 1/
Rises at 0.5% per year in Southcentral,
10,900 to 12,250 by 2000
Rises at 0.5% per year outside Southcentral
2% growth iate until 1985, 1% thereafter
Statewide increase from 14,200 to 20,100
in 2000
Southcentral region increase from 8,100
to 11 ,300
Proportional to increase in wages and
salaries of Government workers
lJ Estimates are in current dollars incorporating a 5 percent annual rate of inflation.
n ,
N
1.0
SECTORS
Total State
Government
Employment
Value of
Facilities
Oil and Gas
Production,
Transportation
Value of
Facilities,
Manufacturing
TABLE C-8 (cont)
HIGH
1. 2,750 positions transferred from Juneau
to Willow, 1982-1984
2. Total employment increases from 14,700
to 38,000 in 2000
3. Declines from 7.6% of civilian wage and
salary employment to about 7.2% by 2000
4. Southcentra1 employment increases from
5,400 to 14,900, or from 5.2% to 13.1%
of total employment
5.
1.
1.
Statewide rate of employment growth is
about 5.4% per year
Based on Dept. of Revenue, Alaska's Oil
and Gas Tax Structure, February 1977,
Page IV, 23, thru 1985, declined at 5%
per year thereafter
Includes estimated value of LNG and
Petrochemical facilities for local
property tax
LOW
Total emp1o~nent increase from 14.700 to
19,159 in 2000
Declines to 6.4% of civilian employment by
2000
Southcentra1 employment rises from 5,400 to
7,140, from 6.1% of civilian employment to
3.1% by 2000
Before 1985, government employment growth
held to 2% per year, with zero growth
thereafter
Based on Dept. of Revenue. Alaska's Oil and
Gas Tax Structure. February 1977, Page IV,
23, thru 1985. declined at 5% per year
thereafter
Includes value of Pacific LNG facilities
SECTORS
Exogenous 1.
Transporation
and Services
Employment
Rate of 1.
Growth of
Disposable 2.
Personal
Income Per
Capita and
'( Wages
w a
TABLE C-8 (cont)
HIGH
Estimated Alyeska employees in these
sectors, plus 40 workers at the Beluga
coal transshipment facilities
Income -2%
Wages -1. 2%
LOW
Alyeska workforce only
Income -1.77%
Wages -1.0%
of employment in these industries was held constant at the year 2000
level. Fishing itself was assumed to replace 10 percent of the foreign
bottomfishing effort after 2000 by the year 2025 in the low case, but
there was assumed to be no change in the traditional fisheries beyond
their year 2000 level. In other manufacturing, the year 2000 employment
level was sustained, except that nonpetrochemical "other" manufacturing
was projected to double after the year 2000 to serve local markets in
the high case.
In projecting the nonbasic/basic ratio, somewhat different pro-
cedures were used for Anchroage and the rest of the region. In Other
Southcentral, the year 2000 regional ratio of nonbasic to basic employ-
ment was multiplied times regional basic employment each year out to
2025 and disaggregated, using year 2000 proportions, which permitted
proportional growth in the nonbasic sector in each subregion after the
year 2000. In the high case, the nonbasic/basic ratio was assumed to
converge to the existing 1975 U.S. ratio by 2025, but it was found to
be already there by 2000. In Anchorage, it was recognized that much
of the "support sector" employment in fact serves statewide needs in
transportation, financial services, etc. Therefore, an estimate was
made of local-serving nonbasic employment by multiplying the statewide
nonbasic/basic ratio by local basic sector employment. The remainder
was designated "statewide-serving" nonbasic employment, which was
assumed to grow at the same rate as basic employment because Anchorage
statewide services in both the basic sector and this part of the non-
basic sector can be assumed to grow in response to similar statewide
demands for central offices and general support services. With the
Anchorage economy relatively mature by that time, it is more difficult
to argue that statewide-serving nonbasic firms would continue to grow
faster than their counterparts in the basic industries after 2000 than
before 2000.
Finally, civilian non-Native population not employed in exogenous
construction was estimated using year 2000 population/employment ratios
at the regional level and allocated to subregions using year 2000 pro-
portions. Any assumption other than proportional population growth
among subregions after 2000 was judged too difficult to defend, since
so little is known about the character of Alaska's economy at that
point. To this was added exogenous construction employment (no growth).
Native population (2 percent growth per year), and military (no growth).
FORECAST RESULTS
The Level B population forecast for the Anchorage-Cook Inlet sub-
region was adopted by APA for estimating power requirements without
any modification. APA applied projected statewide growth rates to the
Fairbanks-Tanana Valley area to develop population forecasts for that
region. The resulting population projections upon which the load
C-31
forecast is based are presented in Table C-9. The figures include
national defense personnel. Actual population growth will likely fall
within the limits established by the high and low forecasts. The APA
population and load forecasts are discussed at length in Section G,
Marketability Analysis.
TABLE C-9
POPULATION ESTIMATES
Anchorage-Cook Inlet Fairbanks-Tanana Valle1 Statewide
Year Low High Low High Low High
1980 239,200 247,200 60,390 62,020 500,225 513,766
1985 260,900 320,000 68,010 77 ,350 563,303 640,718
1990 299,200 407,100 74,660 95,370 618,397 790,042
1995 353,000 499,200 82,130 114,360 680,286 947,312
2000 424,400 651,300 89,700 139,760 743,034 1,157,730
2025 491,100 904,000 99,040 179,240 820,369 1,484,784
UTILITY SECTOR
The midrange net generation forecast from 1977 to 1980 was based
on the average annual growth rate between 1973 and 1977. This rate was
adjusted upward and downward by 20 percent to establish the 1980 high
and low forecasts respectively. Beyond 1980, the high and low case net
generation is estimated by multiplying forecasted population by pro-
jected per capita use. Between 1973 and 1977, per capita use of elec-
tricity grew at an annual rate of 3.8 percent in Anchorage and 9.4
percent in Fairbanks. The lower Anchorage growth rate was adopted as
the basis of the per capita use trend. Increasing electrification is
assumed to be partly offset by increasing effectiveness of conservation
programs, resulting in a gradually slower rate of growth in per capita
use. The future rate of growth in per capita use was projected to
decline as shown in Table C-10.
In order to test the validity of this methodology for estimating
per capita power consumption, comparable regions in the Pacific North-
west were examined. The Eugene metropolitan area, Oregon, (population
150,450) as well as the Richland-Kennewick SMSA, Washington, (population
100,100) were selected on the basis of their similarity in population
and commercial/industrial characteristics to the railbelt area (i.e.,
substantial population coupled with relatively little heavy industry).
In the period from 1970-1977 per capita electricity use increased
by an average of 5.4 percent and 7.1 percent for Eugene and the Richland-
Kennewick SMSA, respectively. This compares to a 3.8 percent per capita
C-32
growth rate for Anchorage (1973-1977). Furthermore, the power sales
anticipated by the utilities which serve Eugene and the Richland-
Kennewick SMSA, coupled with the population projections for these two
regions, reveal an ever increasing rate of per capita consumption.
Clearly, these utilities make little or no provision for energy con-
servation.
In 1977, per capita use in Eugene and the Richland-Kennewick SMSA
was 13,424 kWh and 17,297 kWh, respectively. These current rates meet
or exceed the high forecast for Alaska in the 1980-1985 period. With-
out doubt, Alaska holds a considerable potential for increased electri-
fication.
Pacific Northwest current per capita consumption (excluding aluminum
and others that buy at bus bar) is 13,550 kWh/yr.
TABLE C-10
PER CAPITA USE PROJECTIONS
Low Mid-Range High
Rate Forecast Rate Rate Forecast
Period (%) ( KWH/CaQ} ilL ilL (KWH/CaQ)
1980-1985 2.5 11 ,000 3.5 4.5 13,800
1985-1990 2.0 12,400 3.0 3.5 16,300
1990-1995 1.5 13,100 2.5 3.0 18,900
1995-2000 1.0 13,800 2.0 2.5 21,400
2000-2025 0 13,800 1.0 2.0 35,000
With the high and low population forecasts and with high, mid, and
low per capita use assumptions, six different net generation forecasts
were calculated. From these, the high population-high energy use and
the low population-low energy use combinations were used for the high
and low range net generation forecasts. The midrange utility sector
forecast came from averaging the high population-low energy use and the
low population-high energy use forecasts.
The resulting forecasts are shown in Tables C-12 through C-14.
Peak load forecasts were calculated from projected net generation using
a 50 percent load factor.
NATIONAL DEFENSE SECTOR
The forecast for this relatively minor sector is based on historical
data from Army and Air Force installations in the rail belt area. Zero
growth is assumed for the midrange forecast. For the high range, growth
C-33
at percent per year is assumed, while the low range forecast is based
on a decline of 1 ~ercent annually (see Tables C-12 through C-14).
SELF-SUPPLIED INDUSTRIES SECTOR
This category of load is comprised of those existing industries
that generate their own power, along with all similar type facilities
expected to be constructed in the future. It is likely that such
industries would purchase power and energy if available at reasonable
cost. The specific assumptions for this sector are based on Battelle1s
March 1978 report entitled Alaskan Electric Power, An Analysis of
Future Requirements and Supply Alternatives for the Railbelt Region.
The high range of development includes an existing chemical plant,
LNG plant and refinery, along with a new LNG plant, refinery, coal
gasification plant, mining and mineral processing plants, timber
industry, capital city, and some large energy intensive industry. This
set of assumptions coincides with the Level B Study Task Force high case
development assumptions with two exceptions. Coal gasification and an
energy intensive industry were included by APA because informed judge-
ment indicates their definite potential. Their impact on population
and economic activity is relatively minor but their effect on peak load
requirements could be substantial.
The University of Alaska and Battelle completed a study entitled
Energy Intensive Industries for Alaska in September 1978. The study
evaluated a number of energy intensive industries that might be attracted
to the State as a consequence of the availability of its large and
diversified sources of primary energy. For a number of economic reasons,
it was concluded that the availability of energy resources per se would
not be sufficient to overcome the higher capital, operating and market-
ing costs for a world scale primary industry located in the State.
However, it was also concluded that of all industries examined, the
primary aluminium metal industry appeared to be the most likely to
succeed in Alaska. It was further concluded that a large electro-
process industry would have important implications to Alaska1s electric
power supply· planning. The viability of such an industry is contingent
upon the availability of low cost hydropower. For these reasons, the
development assumptions for the high range case include some large
energy intensive industry.
The assumed peak load requirements in the year 2000 are presented
in Table C-ll. The midrange forecast is the same as the high range
except that the large energy intensive industry (aluminium smelter) is
excluded. The low range further excludes the new capital city. There
is also some reduction of peak load requirements of the mid and low
range cases. The resulting forecast is shown on Tables C-12 through
C-14.
C-34
TABLE C-11
SELF-SUPPLIED INDUSTRY SECTOR ASSUMPTIONS, 2000
(High Range)
Type of Load
Existing Facilities:
Chemical Plant
LNG Plant
Refinery
Timber
New Fac il it i es :
LNG Plant
Refinery
Aluminium Smelter
Coal Gasification Plant
Mining and Mineral Processing
Plant
Timber
New City
Total Peak Load
C-35
Load (MW)
26.0
0.6
2.4
5.0
17.0
15.5
280.0
250.0
50.0
7.0
30.0
683.5
TABLE C-12
TOTAL POWER AND ENERGY REQUIREMENTS
Anchorage-Cook Inlet Area and Fairbanks-Tanana Valley Area Combined
Peak Power
1977 1980 1985 1990 1995 2000 2025
~1I MW MW MW MW MW MW
TOTAL
High 890 1 ,671 2,360 3,278 4,645 10,422
Median 650 829 1.162 1,592 2,134 2,852 4,796
Low 769 961 1,177 1,449 1 ,783 2,146
Annual Energy
GWH 1I GWH GWH GWH GWH GWH GWH
TOTAL
High 3,928 7,636 10,684 14,844 20,936 47,054
Median 2,681 3,663 5,133 7,078 9,528 12,738 21 ,578
Low 3,391 4,256 5,219 6,430 7,890 9,630
lJ Thousand KW = MW
Million KWH = GWH
Source: Alaska Power Administration, Department of Energy
C-36
TABLE C-13
ANCHORAGE-COOK INLET AREA POWER AND ENERGY REQUIREMENTS
Peak Power
1977 1980 1985 1990 1995 2000 2025
~1I MW MW MW MW MW MW
UTILITY
High 620 1,000 1 ,515 2,150 3,180 7,240
Median 424 570 810 1,115 1,500 2,045 3,370
Low 525 650 820 1,040 1 ,320 1 ,520
NATIONAL DEFENSE
High 31 32 34 36 38 48
Median 41 30 30 30 30 30 30
Low 29 28 26 24 24 18
INDUSTRIAL
High 32 344 399 541 683 1 ,615
Median 25 32 64 119 199 278 660
Low 27 59 70 87 104 250
TOTAL
High 683 1,376 1,948 2,727 3,901 8,903
Median 490 632 904 1,264 1,729 2,353 4,060
Low 581 737 916 1 ,151 1 ,448 1 ,788
Annual Energ~
GWH l! GWH GWH GWH GWH GWH GWH
UTILITY
High 2,720 4,390 6,630 9,430 13 ,920 31,700
Median 1,790 2,500 3,530 4,880 6,570 8,960 14,750
Low 2,300 2,840 3,690 4,560 5,770 6,670
NATIONAL DEFENSE
High 135 142 149 157 165 211
Median 131 131 131 131 131 131 131
Low 127 121 115 105 104 81
INDUSTRIAL
High 170 1,810 2,100 2,840 3,590 8,490
Median 70 170 340 630 1,050 1,460 3,470
Low 141 312 370 460 550 1 ,310
TOTAL
Hi gh 3,025 6,342 8,879 12,427 17,675 40,401
Median 1,991 2,801 4,001 5,641 7,751 10,551 18,351
Low 2,568 3,273 4,075 5,125 6,424 8,061
II Thousand KW = MW Million KWH = GWH
Source: Alaska Power Administration, Department of Energy
C-37
TABLE C-14
FAIRBANKS-TANANA VALLEY AREA POWER AND ENERGY REQUIREMENTS
Peak Power
1977 1980 1985 1990 1995 2000 2025
~l! MW MW MW MW MW MW
UTILITY
High 158 244 358 495 685 1 ,443
Median 119 150 211 281 358 452 689
Low 142 180 219 258 297 329
NATIONAL DEFENSE
High 49 51 54 56 59 76
Median 41 47 47 47 47 47 47
Low 46 44 42 40 38 29
TOTAL
High 207 295 412 551 744 1 ,519
Median 160 197 258 328 405 499 736
Low 188 224 261 298 335 358
Annua 1 Energy
Gl~H l! GWH GWH GWH GWH GWH GWH
UTILITY
High 690 1,070 1,570 2,170 3,000 6,320
Median 483 655 925 1,230 1,570 1 ,980 3,020
Low 620 790 960 1 ,130 1 ,300 1 ,440
NATIONAL DEFENSE
High 213 224 235 247 260 333
Median 207 207 207 207 207 207 207
Low 203 193 184 175 166 129
TOTAL
High 903 1,294 1,805 2,417 3,260 6,653
r~ed;an 690 862 1,132 1,437 1,777 2,187 3,227
Low 823 983 1 ,144 1,305 1,466 1 ,569
l! Thousand KW = MW Million KWH = GWH
Source: Alaska Power Administration, Department of Energy
C-3S
CREDIT FOR ENERGY AND CAPACITY
The amount of project power for which benefit can be claimed
depends on both the project's capability and the market requirements.
The latter, in turn, is a function of total loads and the mix of avail-
able generating resources. The determination of this lIusable" energy
and capacity from the Susitna project is based on a load/resource
analysis conducted by Battelle Pacific Northwest Laboratories for APA.
The load/resource analysis matches forecasted electric power
requirements with appropriate generating capacity additions. The
computer aided analysis schedules new plant additions, keeps track of
older plant retirements, and computes the loading of installed capacity
on a year-by-year basis over the period 1978 to 2011.
The analyses are based on the load forecasts and the existing and
planned generating resources described in the previous sections.
Reserve margins of 25 percent for non interconnected load centers and
20 percent for the interconnected systems are assumed. The results of
the load/resource analysis are in terms of net deliverable capacity
and energy after deductions for anticipated transmission losses. The
load/resource analysis methodology recognizes construction schedule
constraints by not allowing call-up of new generation or transmission
capacity that could not be made available. For purposes of this
analysis, the following economic facility lifetimes have been assumed:
Coal-fired Thermal Generation
Oil-fired Steam Generation
Gas-fired Combustion Turbine
Oil-fired Combustion Turbine
Hydroelectric Generation
Years
35
35
20
20
50 11
At the end of its economic life, the facility is retired from
servi ceo
Generating plant availabil.ity can be expressed in terms of plant
utilization factors (PUF's), which are primarily dependent upon plant
type and plant age. For new capacity and most types of existing
capacity, the following maximum PUF's are assumed:
1/ While the payback period for financial calculations is 50 years,
the physical life of a hydroelectric project is typically in excess
of 100 years. The effect of this discrepancy is insignificant
because there are only 53 MW of hydro capacity.
C-39
Hydro
Stream Electric
Combustion Turbine
Diesel
Maximum PUF
0.50
0.75
0.50
0.10
Plants are allowed to run at the maximum PUF from the start, except
for new coal-fired steam electric plants which generally experience
lower plant utilization in the first few years and also toward the
end of their economic lives.
Hydroelectric generation systems, as a result of their storage
ability and conservative ratings, can make additional power available
for peaking and it is assumed they can be scheduled at 115 percent of
design capacity for this service, except during the critical hydraulic
period when head limits plant output.
The results of the base case are presented as Exhibit C-l. In
those years when Susitna hydropower is available, the total system1s
surplus capacity in any given year is subtracted from Susitna hydro
capability in that year to give the actual amount of Susitna capacity
that is usable. The remainder of the Susitna capacity is considered
temporarily surplus to the needs of the market area and no capacity
benefit is claimed. For instance, refer to Exhibit C-l, Watana POL in
1994 and the midrange load forecast. In 1995-96 (Pages C-1-13 and
C-1-14), adding Anchorage and Fairbanks, Watana is on line with 703 MW
dependable capacity and 808 MW overload capacity. The combined Anchorage
and Fairbanks surplus peak capacity in that year is 543 MW. 1/ There-
fore, only 265 MW, or 808 less 543, is usable Susitna capacity. Although
no benefits are claimed for the hydro capacity that appears surplus to
the needs of the market area, that capacity in actuality would be
utilized to generate power. This would result in older thermal genera-
tion being placed in a cold reserve status. This, in turn, extends the
useful life of these temporarily retired plants and postpones the need
for future capacity additions. Though real, the monetary benefits
attributable to this postponement of new capaicty are minor and has
been ignored in this analysis.
For both the medium and high range load growth cases, additional
coal-fired generation would have to be installed after Watana completion
lJ The load resource analysis shows 101 MW surplus in Fairbanks, but
this must be adjusted down by 25 MW to account for the 25 MW steam
plant that comes on line subsequent to Watana.
C-40
but before Devil Canyon power would be available. Unfortunately, due
to construction timing requirements, Devil Canyon cannot be advanced
in order to postpone the coal-fired addition.
Once the Susitna project's dependable capacity is fully absorbed
by increasing peak load requirements, there is the opportunity to
capitalize on the hydroelectric projects' capability to produce addi-
tional peaking capacity on an intermittent basis. This additional
capacity is available when the net power head exceeds the critical head.
(The critical head is where rated capacity is available at full gate
opening.) The amount of additional capacity increases with head until
the full 15 percent overload is reached. This occurs at full gate and
average head (where generator output is maximum), which is at about
630 feet for Watana and 545 feet at Devil Canyon, as can be seen on
Figure C-2. Figure C-3 shows that the head at Watana exceeds 630 feet
about 75 percent of the time. Because the power pool at Devil Canyon
is almost never drafted, Devil Canyon head is sufficient to produce
15 percent overload essentially 100 percent of the time.
Since this interruptible capacity cannot be guaranteed, its value
is typically less than that for dependable capacity. In keeping with
accepted practice, interruptible capacity, when needed to meet peak load
requirements, is valued at 50 percent of dependable capacity. 1/ For
purposes of benefit calculations, Watana is credited with 15 percent of
its at-market dependable capacity, or 103 MW of interruptible capacity.
(Since the full amount is available only 75 percent of the time, the
figure is adjusted downward to 77 MW.) The comparable figure for Devil
Canyon is 100 MW, which brings the combined project's interruptible
capacity to 177 MW for benefit calculation.
Again referring to the load resource analyses in Exhibit C-l (Pages
C-1-13 through C-1-18), it can be seen that the Susitna project's energy
is fully utilized as it becomes available. There is no surplus energy
because thermal plant utilization factors are reduced to take advantage
of the less expensive hydro energy. Therefore, unlike Susitna capacity
benefits which are only claimed through assimilation into the system,
all Susitna energy is useful and benefits can be claimed for all of it.
The value of this hydro energy depends upon the type of generation
that would otherwise be producing the energy in the absence of the
hydroelectric generation. Part of the hydro energy goes to meet the
growth in demand for energy over time. In the absence of the hydro-
electric project, this load growth would be met by new coal-fired
11 Department of the Army, Office of the Chief of Engineers, Digest
of Water Resources Policies, p. A-129.
C-41
generation, and the value of this portion of the hydro energy is there-
fore the cost of coal-fired energy. The remainder of the hydro energy
displaces more costly thermal generation. While the existing thermal
plants continue to provide peak load capacity, the utilization of the
plants decline. This displaced energy is comprised of several types of
generation: coal-fired steam, oil-fired and gas-fired plants, and
diesel plants, each having its unique energy cost. The value of the
hydro energy produced in any year, then, is a composite value deter-
mined by the relative shares of generation type that would be pro-
ducing energy in the absence of the hydro.
The load-resource analysis shows that the great majority of the
displaced generation is coal-fired, since the plant utilization factors
of the diesel, gas, and oil-fired plants were already reduced prior
to Susitna hydropower availability. This results in a composite energy
value that, in the most extreme year, is only 5 percent greater than
the coal-fired energy value. Within 12 years after power-on-line, all
Susitna energy goes toward meeting load growth and is therefore valued
entirely at the coal-fired value. Because the effect on project justi-
fication is so minor over the lOO-year economic life, the benefit of
the hydro energy has been calculated using the coal-fired energy value,
not the slightly higher composite energy value.
The usable capacity and energy for the midrange forecast with
interconnection in 1991, Watana power-on-line in 1994 followed by Devil
Canyon in 1998 is presented in Table C-15 and is portrayed graphically
on Figures C-4 and C-5. The usable capacity analysis results for the
various cases analyzed appear as Exhibit C-3 and are presented graphi-
cally in Exhibit C-2. Shown are cases for the low and high-range load
forecasts, as well as for delayed power-on-line dates.
C-44
TABLE C-15
USABLE CAPACITY AND ENERGY, BASE CASE
Dependable Interruptible Prime Secondary
Year Ca~acit~ (MW} CaQacit~ (MW) Energ~
1994 * 27 0 2,997
1995 265 0 3,058
1996 680 0 3,058
1997 680 0 3,058
1998 # 950 0 6,057
1999 1,035 0 6,057
2000 1,231 0 6,057
2001 1,347 1 6,057
2002 ## 1 ,347 177 6,057
* Watana power-on-1ine with interconnection.
** Less than full energy avai1abe due to reservoir filling.
# Devil Canyon power-on-1ine.
## Full utilization of Susitna power.
C-45
Energ~
o **
397
397
397
397 **
785
785
785
785
THE SELECTED PLAN
POWER CAPABILITIES
The installed capacities at Devil Canyon and Watana reservoirs
were selected based upon the project firm annual energy produced in
a 28-year period of historical streamflow (1950-1977). This period
included three new years of streamflow, in addition to the 25 years
used in the original scoping analysis prepared in 1975. An updated
seasonal load curve prepared by APA was used in the new simulated
operation study.
The addition of the 3-year period of recorded streamflows resulted
in changes to the average annual and firm annual energy capability
amounting to less than 2 percent. The annual runoff for the 3-year
period is 96 percent of the long-term average. Therefore, no adjust-
ment in the original energy capab-ilities is considered necessary. The
power generating capabilities for the project are given in Table C-16.
TABLE C-16
AT-SITE POWER CAPABILITIES
Installed Capacity, MW
Peaking Capacity, MW
Dependable Capacity, MW
Average Annual Energy, 10 3 MWh
Firm Annual Energy, 10 3 MWh
Secondary Energy, 10 3 MWh
Average Annual Spilled Energy, 10 3 MWh
Plant Factor -Percent l/
II Based on firm annual energy.
Devil Canyon
689
792
689
3,410
3,020
390
31
50
Watana
703
809
703
3,480
3,080
400
44
50
Total
1 ,392
1 ,601
1 ,392
6,890
6,100
790
75
50
The driest year of record was 1969, which was estimated to have a
1,000 year return period based upon a Log Pearson Type III probability
distribution, with an average annual runoff at Devil Canyon of 5,600
cubic feet per second, or 59 percent of average. The second driest
year of record (1950) had a return period of 20 years with an average
annual runoff of 7,340 cubic feet per second. The 100-year average
annual low flow is estimated to be 6,500 cubic feet per second or 68
C-48
percent of average. The 10 month period immediately following the 100-
year low flow would likely be the most critical power period to be encoun-
tered in the life of the project.
The project dependable capacity is based upon the firm annual
energy and is equal to the installed capacity. The project firm annual
energy using the 28-year record of historical flows occurred in 1971.
During May of that year total project storage was reduced to its lowest
level of the entire period (230,000 acre-feet or 3 percent of usable
storage). The annual energy produced by the project in 1971 was approxi-
mately 6,100,000 megawatt hours.
The maximum peaking capacity for both powerplants is 115 percent
of installed or rated capacity at 0.9 power factor. This 15 percent
overload capability was assumed to be available only at or near maximum
head on each unit for routing purposes.
The large storage capacity of Watana reservoir provides nearly full
river control. Spills occurred in 8 of the 28 years of record and were
only about 1 percent of the average annual project energy.
The transmission losses have been estimated by APA to be 3.2 per-
cent on-peak and 0.7 percent for the long-term average. The at-market
power capabilities are shown in Table C-17.
TABLE C-17
AT-MARKET POWER CAPABILITY
Installed Capacity, MW
Peaking Capacity, MW
Dependable Capacity, MW
Average Annual Energy, 10 3 MWh
Firm Annual Energy, 10 3 MWh
Secondary Energy, 10 3 MWh
SEASONAL RESERVOIR OPERATION
At-Site
1 ,392
1 ,601
1,392
6,890
6,100
790
Losses At-Market
45 1 ,347
51 1,550
45 1,347
48 6,842
43 6,057
6 784
The 1978 update of the simulated operation study did not result
in any substantial revisions to the overall pattern of project opera-
tion. The general criterion as before was to maintain Devil Canyon
reservoir at maximum pool to realize the greatest possible head on
C-49
that reservoir. During the winter, withdrawals were made from Watana
storage to meet th~ system power demand. Devil Canyon storage was
used only after the supply in Watana reservoir was exhausted.
The general characteristics of the Watana operation are shown in
Figure C-6. The pool elevations shown have been adjusted in accordance
with the topographic information obtained in the 1978 field surveys
at the Watana damsite. In years of average streamflow the maximum
drawdown on Watana reservoir waS about 100 feet. The reservoir reached
minimum active pool (elevation 1,940 feet) on only two occasions in
the 28-year period.
In the simulated operation, one criteria was to fill Watana reser-
voir on September 30 each year. This was not possible, however, in
13 of 28 years of record. In such years of reduced streamflow, it
proved to be inefficient to draw the Watana pool to a low level on
September 30 in order to meet the system load requirement. If the
reservoir was consistently drawn below elevation 2.100 feet (storage =
6,700,000 acre-feet) on September 30 each year, the resulting head
loss was of such magnitude that the project was unable to recover
sufficiently to meet minimum system load requirements, even in years
with above average runoff. The minimum September 30 carry-over for
Watana reservoir was therefore set at 6,700,000 acre-feet for the
updated 1978 simulated operation studies. The generation and water
storage levels for Devil Canyon and Watana reservoirs for the entire
28-year period of record are shown on Plates C-l and C-2.
The spring and summer filling operation for Watana reservoir in the
operation studies was guided only by a fixed flood control rule curve.
In later scoping studies this operation could be improved somewhat
through the use of a variable rule curve based upon both 7-day and
seasonal volume forecasts.
In the simulated operation, only the releases necessary for minimum
generation requirements were made until the month when the reservoir
would fill or encroach the flood space. Only during that month could
the excess runoff be used to generate secondary energy. The method of
operation results in unnecessary spillage of water.
In order to obtain a more realistic estimate of the spill frequency
at Watana reservoir, a separate study was conducted. In this study
the daily inflow to Watana reservoir was estimated using the records
from the stream gage at Gold Creek. It was assumed that the full
hydraulic capability of the Watana turbines could be used for 15 days
in advance of the spills observed in the other simulation study. In
addition, for 5 days in advance of the spills, the outlet tunnel with
discharge capacity of 30,000 cfs was used to maintain the pool below
C-50
the crest of the spillway as much as possible. When the inflows
exceeded the discharge capacity of both the powerplant and the outlet
works and the reservoir reached full pool, the spillway, of course,
had to be used.
The results of the study are shown in Figure C-7. The curve on the
right indicates the frequency of spills if the outlet tunnel is not
used; the curve on the left assumes both the powerplant and the outlet
tunnel are used. The curve illustrates that the spillway at Watana
reservoir would be used approximately once in 10 years.
C-52
ECONOMIC ANALYSIS
COSTS -THE BASE CASE
A detailed construction cost estimate for Watana, Devil Canyon,
and the connecting transmission systems is presented in Section B,
Project Description and Cost Estimates. It is expected that construc-
tion will begin in 1984, the transmission intertie would be complete
in 1991, Watana would be complete in 1994, and Devil Canyon would be
complete in 1998. Total estimated first cost of Devil Canyon and
Watana plus the transmission system is $2.588 billion.
Interest During Construction (IDC)
The interest charged on money expended during the construction period
is considered an additional cost of the construction phase. Simple
interest is calculated at 6-7/8 percent for each year1s expenditure
and added to first cost to establish the investment cost.
System Annual Costs
Expenditures and IDC made after the October 1994 POL date of Watana
are discounted to 1994. The resultant total investment cost is then
transformed into an equivalent average annual fixed cost by applying
the appropriate capital recovery factor associated with the 6-7/8 per-
cent interest rate and 100-year project life.
Annual Operations, Maintenance, and Replacement
Operations, maintenance, and replacement costs estimated by APA
are added to the average annual costs to obtain a total average annual
cost of $228 million. See Table C-18.
HYDROPOWER BENEFITS
Power Values and Alternative Costs
The power values and alternative costs for use in power benefit
calculations were developed by the San Francisco Regional Office of
the Federal Energy Regulatory Commission (FERC), an agency of the
Department of Energy. A copy of the letter forwarding the power values
is included in Exhibit C-7. The method of analysis used by the FERC
staff in developing the power values is explained in H droelectric
Power Evaluation, by the Federal Power Commission (FPC , dated March 1968.
The calculations were based on a 50 percent plant factor for the
upper Susitna basin projects. Based on future load estimates, FERC
C-54
TABLE C-18
ANNUAL COST COMPUTATIONS
(in thousands of dollars)
Watana Devil Canton Gravit~ Dam
Accumulated Present Worth Accumulated Present Worti'
Year Expenditure Expenditure IDC Expenditure of Expenditure Expenditure IDC of IDC
1984 30,500 1,048
1985 107,000 30,500 5,775
1986 114,000 137,500 13,372
1987 159,000 251,500 22,756
1988 218,500 410,500 35,733
1989 214,000 629,000 50,600
1990 248,000 843,000 66,481
n 1991 258,000 1,091,000 83,875
I 1992 223,000 1,349,000 100,409 39,000 39,000 1 ,341 1 ,341 c.n c.n 1993 161,000 1 ,572,000 113,609 98,500 98,500 39,000 6,067 6,067
1994 32,000 1,733,000 120,244 117,000 117,000 137,500 13,475 13,475
1995 1,765,000 1,765,000 613,902 137,000 128,187 254,500 23,581 22,064
1996 144,000 126,070 391 ,500 38,191 33,436
1997 158,000 129,428 535,500 43,622 35,734
1998 129,500 99,258 693,500 53,505 41 ,010
823,000 737,443 823,000 179,782 153,127
Watana Devil Can~on Total Watana & Devil Canyon
Construction Cost $1,765,000 $737,443 $2,502,443
I.D.C. 613,902 153,127 767,029
Investment Cost $2,378,902 $890,570 $3,269,472
Interest and Amortization $ 163,761 $ 61 ,307 $ 225,068
Operation, Maintenance, and
Replacement 2,620 700 3,320
Average Annual Cost $ 166,381 $ 62,007 $ 228,388
assumed that the output of the proposed hydropower project would be
utilized between the two major railbelt area load centers in the ratio
of 80 percent to Anchorage-Kenai and 20 percent to Fairbanks-Tanana
Valley.
Power values are provided for two generation alternatives at each
of the load centers. An oil-fired combined cycle plant located near
Anchorage and a mine-mouth coal-fired steam-electric generating plant
located near the Beluga coal fields are considered as alternatives to
hydropower for the Anchorage-Kenai area. For the Fairbanks load center,
an oil-fired regenerative combustion turbine plant near Fairbanks and
a mine-mouth coal-fired steam-electric plant near Healy are suggested
as the proper alternative power sources. FERC notes that the agency is
unable to state that either is the most probable source, despite the
oil-fired alternatives appearing less expensive.
Whereas in 1975 FPC presented gas-fired generation as a possible
alternative, it is no longer considered a viable option because of
national policy and, specifically, the National Energy Act.
The Anchorage area coal-fired power values are based on a two
unit, 450 MW plant with a service life of 30 years. The heat rate is
10,000 BTU/kwh and the annual plant factor is 55 percent. The invest-
ment cost estimate is $1,240 per kilowatt, while the cost of fuel is
estimated at $1.10 per million BTU. Included in the estimate are
baghouse filters and S02 scrubbers at $187 per kilowatt and cooling
towers at $35 per kW. These are July 1978 costs, and neither infla-
tion nor fuel cost escalation are considered.
The coal-fired alternative at Fairbanks is a two unit 230 MW plant,
also with a 30 year service life. Its heat rate is 10,500 BTU/Kwh and
has a 55 percent plant factor. The estimated investment cost is $1,475
per kilowatt and the fuel cost is assumed to be $.80 per million BTU.
Included in this estimate are electrostatic precipitators and S02
scrubbers at $357 per kW and cooling towers at $44 per kW. Again,
these are the costs as of July 1978.
Financing for the Anchorage alternative is a combination of 75
percent REA and 25 percent municipal. In Fairbanks, the assumption is
that financing would be provided by the Alaska Power Authority.
The composite capacity value of the coal-fired alternative is
$186.58 per kilowatt-year. The corresponding energy value is 12.76
mills per kWh. This and other sets of power values are shown in more
detail in Exhibit C-4.
C-56
Natural Gas Alternative
In not providing power values for a gas-fired thermal alternative,
FERC indicates its agreement with APA and the Corps of Engineers that
natural gas is not an appropriate long-term alternative to hydropower
in the Anchorage area. This is in keeping with the National Energy
Act which prohibits such use in base-load plants with very limited
exception.
The strongest argument against the use of natural gas for electrical
generation is the national energy policy, but limited Cook Inlet supplies
offer additional rationale. Since the Office of Management and Budget
specifically commented on the Cook Inlet gas supply situation, updated
information has been gathered.
The estimated Cook Inlet natural gas balance through the year 2000
is presented in Table C-19. The reserve estimates are based on an
analysis entitled "Estimated Recoverable Gas Reserves from Gas Fields
in the Cook Inlet Area" by the State Division of Oil and Gas Conser-
vation, April 13, 1978. Division analysts believe that more detailed
study would likely result in as much as a 20 percent increase in the
estimate for three fieldso 1/ This correction would result in an
increase of 436 BCF over the 13 April 1978 estimate of 3,776 BCF. Not
included in the Divisionis estimate are approximately 216 BCF of Kenai
Field gas that has been leased for reservoir pressure maintenance.
This gas will be returned in future years and will be available for
sale. The adjusted estimate of recoverable Cook Inlet gas reserves is
therefore 4,428 BCF. The Alaska Division of Mineral and Energy Manage-
ment estimates potential additional resources of about 7 trillion cubic
feet; such estimates are speculative with little agreement among experts.
Approximately 3,698 BCF, or 84 percent of those reserves are
presently committed to Alaskan and export uses. Table C-20 presents
the estimated reserves and commitments by field. The Pacific Alaska
LNG contracts, amounting to 952 BCF. have lapsed as a result of failure
to gain FERC approval of the project. The approval has been delayed
largely due to the PALNGls inability to gain gas cornmittments suffi-
cient to operate at required scale. PALNG continues to explore for
gas in Cook Inlet and eventual FERC approval is anticipated. PALNG
expects the lapsed contracts to be readily reinstated with an extended
deadline for project approval and some renegotiation of price. The
PALNG lapsed contracts are therefore considered committments for this
analysis.
l! Conversation with staff of the Division of Oil and Gas Conservation,
27 September 1978.
C-57
There has been an unwillingness on the part of natural gas owners
to enter into contracts for the provision of gas during a period of
rapidly escalating gas prices and great uncertainty regarding gas
price deregulation. Additional commitments are anticipated as the
pricing structure stabilizes.
In 1976, 34 percent of Alaska's total energy consumption was pro-
vided by Cook Inlet natural gas. The uses are detailed in Table C-21.
In the same year, 54 percent of Alaska's electrical generation was
provided by Cook Inlet gas. Natural gas is exported in large quantities
in the form of both LNG (liquified natural gas) and ammonia-urea
fertilizer. Comparing consumption in 1976 with the previous year,
natural gas use was up 12 percent with the largest increase, 18 percent,
in electricity generation.
Projections of natural gas consumption levels between 1980 and 2000
were developed in a study for the Alaska Royalty Oil and Gas Development
Advisory Board and the 1978 Alaska State Legislature. The report, pub-
lished in January 1978, is entitled Oil and Gas Consumption in Alaska,
1976-2000. A base case projection of gas demands is presented and
possible departures from the base case are analyzed. Over the entire
period, natural gas use is forecasted to grow at 2 percent annually.
This low rate is attributable to the base case assumptions of prohibi-
tion on the use of gas in new electricity generating facilities "in the
mid-1980's and only moderate increases in industrial use. As a result,
use of gas in 1980 is 238 billion cubic feet, up from 165 BCF in 1976.
By 2000 its has risen to 267 BCF, reflecting the fact that most of the
growth in natural gas consumption is assumed to occur in the near
term and in the industrial sector.
The forecast shows gas use in space heating to be the most rapidly
growing demand throughout the period at 5 percent. Gas use in elec-
tricity generation remains essentially constant, while industrial use
of gas rises sharply in the near future, but further increases are
assumed to be zero because of supply constraints. The base case
assumes population growth of about 3 percent annually, per capita
demand somewhat moderated by high energy prices, and no significant
new industrial consumers of large amounts of gas.
The sensitivity of the projection to changes in several of the
assumptions was tested. All resulted in increased demand relative to
the base case. Two of the possible scenarios are of special interest
and appear in Table C-19.
One possibility is the continued use of gas in new electricity
generating units in Anchorage after the mid-1980's. By 1990 this
would add about 23 BCF annually to gas demands for electric power,
C-58
essentially doubling gas use by that sector. This would add 10 per-
cent to total gas requirements in that year and increase the overall
growth rate in gas consumption from 2 percent up to 3 percent for the
projection period.
The active proposal to liquify Cook Inlet natural gas for transport
to California is a second scenario of interest. As noted earlier,
required FERC approvals have yet to be given, but PALNG continues to
actively explore for additional Cook Inlet gas and to plan for con-
struction of facilities beginning in 1980. This proposal would
require about 80 BCF annually in its initial phase. Were adequate
reserves available, this would be essentially doubled to 161.6 BCF
annually. Over a period of 15 years (assuming a start in 1985) such
a project would thus require from 1,200 to 2,424 BCF of Cook Inlet gas.
Another source of Cook Inlet gas demand forecasts is Natural Gas
Demand and Supply to the Year 2000 in the Cook Inlet Basin of South
Central Alaska, a November 1977 report compiled by the Stanford
Research Institute (SRI) for Pacific Alaska LNG Company. The SRI
forecast is somewhat higher than that previously discussed. This
difference is accounted for primarily in the industrial component,
where SRI does not limit growth as was done in the 1978 base case
forecast to accommodate anticipated supply constraints. The SRI
intermediate forecast is presented along with the other three scenarios
in Table C-19.
Summing the annual estimates of Cook Inlet demand requirements
from 1976 to 2000 results in total estimated requirements of 5,211 BCF
in the base case. The addition of Pacific Alaska LNG increases the
forecast to 6,411 BCF or 7,635 BCF depending on the scope of the opera-
tion. The addition to the base case of new gas-fired electrical gen-
eration increases the forecast to 5,743 BCF. The SRI intermediate
forecast of total demand over the period is 8,232 BCF, which includes
full scale PALNG, but no new gas-fired generation.
Estimated proven Cook Inlet gas reserves are inadequate to meet the
requirements in all forecasted cases. The deficit through the year 2000
varies from a low of 783 BCF in the base case to 3,804 BCF in the SRI
intermediate forecast (see Table C-19). The use of Cook Inlet gas for
new gas-fired electrical generation after 1985 would increase the year
2000 deficit by about 532 BCF.
There mayor may not be sufficient undiscovered gas reserves in the
Cook Inlet area to meet the anticipated deficit. Estimates of undis-
covered reserves range from 6-29 trillion cubic feet. Because the Cook
Inlet gas supply has historically far exceeded local demand and because
C-59
TABLE C-19
COOK INLET NATURAL GAS BALANCE
1977 to 2000 11
(Billion Cubic Feet)
LNG to California New Gas Generation SRI
(80 BCF/161 in Anchorage (79 BCF Intermediate
Base Case BCF Annua lll:) Annuall~ in 2000) Case
Demand
(A) Estimated Requirements 5,211 6,411/7,635 ?J 5,743 Y 8,232 Y
(B) Committed Reserve ~ 3,698 3,698 3,698 3,698
(C) Remaining Requirements §j 1,513 2,713/3,937 2,105 4,534
n
I
0'1 Suppll: 0
(D) Estimated Recoverable
Reserves 11 4,428 4,428 4,428 4,428
(E) Uncommitted Reserves ~ 730 730 730 730
(F) Undiscovered Reserves ~ ? ? ? ?
Balance
(G) Deficit (Not Including
Possible Undiscovered
Reserves) .!.Q! 783 1,983/3,207 1 ,375 3,804
NOTES TO TABLE C-19:
11 Based on "Oil and Gas Consumption in Alaska, 1976-2000," January
1978 by the Division of Energy and Power Development and the
Division of Minerals and Energy Management, Table IV.l. with
modifications explained below.
?J Base case requirements plus additional LNG export from 1985 to
2000 of either 80 BCF annually or 161 BCF annually.
}/ Gas use in new gas-fired electrical generation increases from zero
in 1985 to 79 BCF annually in 2000.
if Intermediate case without additional gas-fired electrical generation
from "Natural Gas Demand and Supply to the Year 2000 in the Cook
Inlet Basin of southcentral Alaska," November 1977 by the Stanford
Research Institute for Pacific Alaska LNG Company, Table II.
~/ See Table 2.
§j (C) = (A) -(B)
]j See Table 2.
(E) = (D) -(B) f}j
9/ Estimates range from 6 to 29 trillion cubic feet but are too
speculative for purposes of power planning.
(G) = (A) -(0) or (C) -(E)
C-61
TABLE C-20
COOK INLET NATURAL GAS RESERVES AND COMMITTMENTS
Field
Beaver Creek
Beluga River
Birch Hill
Falls Creek
Ivan River
Kenai
Lewis River
McArthur River
Nicolai Creek
North Cook Inlet
North Fork
Sterling
Swanson River
West Forelands
West Fork
TOTAL
NOTES:
Source lJ
PALNG
DOGC, PALNG
PALNG
DOGC
PALNG
DOGC, PALNG
DOGC
Committed -(Ben
112
1,003
101
1,708
22
87
666
3,698
Total Reserves £!
(BCn
239
1 ,057
11
13
101
1,785 3/ 4/ 90 - -
140 3/
17 -
912 3/
12 -
23
o
20
8
4,428
lJ DOGC is short for "Summary of Gas Sales Contracts, Cook Inlet Area,
March 15, 1976" by the Division of Oil and Gas Conservation.
PALNG refers to data provided by Len McLean of Pacific Alaska LNG
Company in un interview on 4 October 1978.
?J The total reserve estimates are taken from "Estimated Recoverable
Gas Reserves from Gas Fields in the Cook Inlet Area," April 13,
1978 by the State Division of Oil and Gas Conservation. The report
was augmented by information provided by Lonnie Smith, Chief
Petroleum Engineer, DOGC, in an interview on 28 September 1978.
~ Includes a 20 percent increase over estimate contained in April 13,
1978 DOGC report on the basis of new information avai~able to DOGC.
if Includes 216 BCF leased for reservoir pressure maintenance that
was not included in the DOGC report.
C-62
TABLE C-21
1976 ALASKA GAS USE Jj
Use
Final Consumption (Heating)
Electrical Generation
Extraction and Processing Uses
Exports
TOTAL
NOTES:
Quantity (MMCFl
16,804
29,284
137,880 Y
87,765 'ij
271,733
.lI Source is "Oil and Gas Consumption in Alaska, 1976-2000,"
January 1978.
~ 26,798 MMCF production related; 111,082 MMCF reinjected, much
of which can be eventually recovered.
11 63,509 MMCF for LNG; 24,256 MMCF for ammonia-urea.
C-63
until recently there has been no substantial export market, the Cook
Inlet area has not yet been extensively explored for natural gas.
Despite the possibilities, the speculative reserves are inappropriate
for consideration in power planning. Regardless of availability, how-
ever, the worldwide competition for natural gas will escalate the price
of gas to levels which will likely make new gas-fired base load genera-
tion uneconomic in the face of large available supplies of coal and
hydropower potential.
Oil-Fired Generation Alternative
As noted previously, FERC provided power values based on both oil-
fired and coal-fired generation for both Anchorage and Fairbanks. The
National Energy Act generally prohibits the use of oil as fuel in new
large-scale base load generating plants. The act also includes, however,
several provisions under which a utility may be exempted from the restric-
tions on use of oil. Under the law, companies may be exempted from the
fuel-switching requirement for new plants if they can prove it would
be overly costly, environmentally unsound, or impossible because of
insufficient or unavailable supplies of coal or other fuels at the
plant's location.
Proposed regulations to implement the coal-conversion portion of the
energy bill have been issued by the Department of Energy. 1/ To gain
an exemption on cost grounds, for instance, a company would have to
prove that a coal or alternate fuel plant was much more expensive
than the oil or gas plant. Under the proposed rules, coal plants
costing 30 to 80 percent more than oil or gas plants would not neces-
sarily be considered too costly to avoid mandatory conversion. Based
on the FERC-provided power values, annual costs for coal-fired genera-
tion are approximately 40 percent higher than for oil-fired. This
is based on a 50 percent plant utilization factor and includes capital
expenses as well as the costs for operation and fuels.
To gain an environmental exemption under the proposed rules, com-
panies would be required to produce decisions from the Environmental
Protection Agency or State agencies proving that coal plants would be
environmentally unacceptable. Although some proposed plant sites in
Alaska are extremely sensitive, such as at Healy adjacent to Mt. McKinley
Park, there is no evidence that acceptable sites cannot be found.
To gain an exemption based on fuel availability at a plant's
location, a utility would have to show it fully considered a range of
alternative sites, including sites outside the utility's traditional
service area. The substantial proven coal resources at both Healy
and Beluga argue against using this rationale in seeking an exemption.
l! As reported in the Wall Street Journal, November 14, 1978, P 14.
C-64
To gain an exemption based on an inability to raise capital, a
company would have to show that the added capital needed to burn coal
or alternate fuels, instead of oil or gas, equals 25 percent or more
of the annual average capital budget.
In writing these regulations, it is clear that the administration's
intent is to severly limit the scope of exemptions and place a heavy
burden of proof on utilities seeking an exemption. Based on the proposed
regulations, it would appear that rail belt utilities would have a
difficult time obtaining exemption for new base load plants. The Alaska
Power Administration, Department of Energy, agrees with this assessment.
The APA Administrator, Robert J. Cross, writes that "(APA's) finding is
that exemptions don't seem all that permanent or pertinent in terms of
a large new hydro project coming on line in 1992. I just don't see the
logic of the oil assumption in benefit determinations for lOO-years of
power from a major new hydro project." 1/ Also agreeing that oil is an
inappropriate alternative for benefit calculation is the State's Alaska
Power Authority. The Power Authority's Executive Director, Eric P. Yould,
states that, "oil-fired generation for the rail belt area may not be accept-
able either for legal and regulatory reasons or from the standpoint of
fuel availability." 2/ He notes further that Golden Valley Electric
Cooperative at Fairbanks recently analyzed the coal versus oil-fired
generation question. GVEA has determined that the coal-fired genera-
tion alternative is preferable to oil if capital costs are not pro-
hibitive. The full text of both pieces of correspondence are contained
in Exhibit C-7.
Based on the foregoing, coal-fired generation has been selected
as the most likely and appropriate alternative against which to compare
the Susitna hydroelectric proposal. Coal is therefore the basis for
the base case benefit calculations. Oil-fired generation is addressed
in the sensitivity analysis.
Derivation of Power Benefits -The Base Case
Annual power benefits were computed by applying the unit value of
capacity and energy to the usable output of the hydropower project.
Benefits were computed for each year of the lOO-year economic life of
the project and were then discounted to the base date to determine the
combined present worth. The base date in all cases is the power-on-
line date of the Watana project. The prescribed Federal discount
rate of 6-7/8 percent was used. The last step of the calculations
1/
~/
Robert J. Cross, Administrator, Alaska Power Administration in a
memo to FERC dated 9 November 19780
Eric P. Yould, Executive Director, Alaska Power Authority in a
letter to Colonel George Robertson dated 17 November 1978.
C-65
entailed the conversion of the present worth value to an equivalent
average annual benefit, again using the 6-7/8 percent discount rate.
The results of the computer-aided calculations are shown in Exhibit C-5.
For the base case, which included coal-fired power values, the
median load forecast, power-on-line dates of 1994 and 1998 for the
two stages of development, transmission line completion in 1991, publici
non-Federal financing of the thermal alternative, and stable prices,
the average annual power benefits are estimated at $289 million. For
Watana alone, the corresponding figure is $158 million.
OTHER BENEFITS
Recreation
Recreation-day values for 1978 were researched in order to check
the need for changing the values as originally reported in the 1976
Interim Feasibility Report. A review of other projects such as the
Chena Lakes Project at Fairbanks indicated that the former values are
typical of 1978 visitor-day recreation values and remain unchanged.
Therefore, the average annual benefit for recreation is $300,000.
Flood Control
The extent of damage prevention from downstream flooding remains
unchanged. The dollar value of those losses has been adjusted to
reflect the time elapsed since the original estimate. The annual
benefits for flood control are $65,000.
Employment
When otherwise unemployed labor resources are used in the construc-
tion of a project, the economic cost of those resources is less than
the prevailing wage rate. Conceptually, this adjustment can be made
either by an appropriate reduction to the project's cost or by an
increase in project benefits. The latter approach has been adopted by
Corps of Engineers regulations.
The labor area for this project is to be Anchorage and Fairbanks.
The proposed project will be located in an unpopulated area and will
draw heavily from these two population centers. Alaska is designated
by the U.S. Department of Labor as an area of substantial and persistent
unemployment.
The present labor force in the Anchorage/Fairbanks area is 114,800,
with approximately 12,534 in the construction industry. With an
average 10,443 unemployed, approximately 25 percent or 2,610 are
construction labor. The possibility of a gas pipeline project and the
C-66
capita 1 rel ocati on wi 11 affect the avail abil ity of otherwi se unemployed
workers to the Susitna project. The adjustment depends on whether
these projects occur prior to or concurrent with the Susitna project.
During the oil pipeline construction a preferential hire law was
in force which directed pipeline contractors to hire qualified Alaska
residents in preference to nonresidents. The Alaska Department of
Labor reports that during construction of the oil pipeline the average
percent of manpower requirements drawn from within Alaska was 40 to
50 percent. The proposed upper Susitna hydro project is much smaller
than was the oil pipeline project. It is thought that an 80 percent
local hire goal could easily be met. The proposed gas pipeline project
is planned to begin in the early 1980's and completion is anticipated
before Susitna construction begins.
Estimated yearly manpower expenditures for construction of the Devil
Canyon and Watana dams and the transmission line are shown in Table
C-22. These figures were derived by estimating the labor cost associated
with each major feature of the project, net of contingencies. Overall,
38 percent of project costs are estimated to be labor expenses.
TABLE C-22
MANPOWER EXPENDITURES
($1,000)
Percent
Year Sk ill ed Unskilled Total of Total
1984 8,307 2,077 10,384 1.2
1985 28,378 7,094 35,472 4. 1
1986 30,454 7,614 38,068 4.4
1987 42,221 10,555 52,776 6.1
1988 58,140 14,535 72,675 8.4
1989 57,448 14,362 71,810 8.3
1990 66,446 16,611 83,057 9.6
1991 69,214 17,304 86,518 10.0
1992 69,906 17,477 87,383 1 0. 1
1993 69,214 17,304 86,518 10.0
1994 40, 144 10,036 50,180 5.8
1995 36,683 9, 171 45,854 5.3
1996 38,760 9,690 48,450 5.6
1997 42,221 10,555 52,776 6.1
1998 34,607 8,651 43,259 5.0
692,143 173,036 865,179 100.0
C-67
Approximately 6 percent of these labor expenses are attributable to
the contractors' supervisory and managerial functions. Of the remaining
$813 million labor costs, 80 percent are expected to be paid to locally
hired labor. Of this total an estimated 20 percent or $130,000,000
will be for unskilled labor, while 80 percent or $521,000,000 will be
for skilled labor. Following the recommendations of Draft ER 1105-2-354,
the proportion of labor costs claimed as employment benefits for skilled
and unskilled categories are 40 percent and 55 percent respectively.
Using an interest rate of 6-7/8 percent, each year's benefits are
present-worth to POL. Then, using the summation of all years, the
appropriate capita1 recovery factor is applied to obtain the annual
employment benefit for each category of workers (skilled and unskilled).
The annual skilled labor benefit is $17,562,000 and the annual unskilled
labor benefit ;s $6,037,000. Thus, the total employment benefit for the
Susitna project is $23,599,000.
Similar procedures have been applied to the coal-fired and oil-fired
generation alternatives to estimate their respective employment benefits.
This is in keeping with Draft ER 1105-2-354 which directs that employ-
ment impacts of each alternative plan are to be assessed. The estimated
labor portion of the total project cost was calculated using FERC invest-
ment cost data and labor percentages for the planned Healy II coal-fired
plant. At a composite (Anchorage-Fairbanks) investment cost of $1,287
per kilowatt, the total cost of coal-fired plant construction, equivalent
in output to the Susitna project, is $2,060,487,000. This total amount
was scheduled over the planning period to reflect capacity additions
indicated by the load-resource analysis medium range case.
According to Stanley Consultants, the engineering firm that has
developed the plans for Healy II on behalf of Golden Valley Electric,
approximately 40 percent of construction costs are payments to labor. 1/
Using the same proportion of skilled and unskilled labor as was used
with the hydro project calculations and the same discounting procedures,
the average annual equivalent employment benefit for the coal-fired
generation alternative is $19,635,000. 2/ The comparable figure for
the oil-fired alternative is $5,203,000~ These estimates are presented
for rough comparison only since they do not reflect a detailed study
of labor requirements for thermal plant construction. Since, on average,
a more skilled workes is required for construction of the thermal plant
and since such a worker would probably not be available locally, the
thermal alternative employment benefit estimate is probably somewhat
overstated.
1/ Per conversation with Stanley Consultants, 20 December 1978.
~ This amount incorporates a 20 percent reduction to account for
contingency factors in the cost estimates, thus insuring comparability
with the hydro project.
C-68
The thermal alternatives are procedurally defined to have power
benefits equal to plan costs. The crediting of employment benefits,
therefore, results in the thermal alternatives each having positive net
benefits equal in magnitude to the employment benefit.
Intertie Benefits
The original feasib-ility report discussed the value of intercon-
nected load centers made possible by the construction of a transmission
line between Anchorage and Fairbanks. It was noted that intertie
benefits arise from two aspects of interconnection, shared reserves
and energy transfer.
The load-resource analysis has demonstrated that capacity additions
can be postponed as a result of reduced reserve requirements in an inter-
connected system. Since the reserve margin effectively increases the
amount of generating capacity in place at any given time, it contributes
costs to the system. Therefore a reduction in that reserve margin
will reduce cost. Realizing that a more refined analysis of desired
reserve margins will be needed at a later date, APA now estimates that
a 25 percent margin would be required without interconnection while
only 20 percent reserves would be needed with interconnected load centers.
These estimates are based largely on the experience in other market areas.
The flexibility afforded by the transmission line decreases as the
1 i ne becomes loaded with Sus itna power. The reserve reducti on capabi 1 ity
is limited by the unused portion of the line segment with the least
capacity -that portion from Devil Canyon to Fairbanks. When the line
is completed and before Watana power production beg"ins, a full 300 MW
capacity is available in the line. 1/ This is reduced as time goes
on by the amount of Susitna capacity allocated to the Fairbanks load
center. The capacity savings due to interconnection for each year,
then, is the lesser of unused line capacity and the 5 percent reserve
differential applied to the total peak load requirement. This is
shown graphically in Figure C-8, and the results are presented in
Table C-23. Each year's capacity saving is valued at the capacity
value of a coal-fired steam plant as provided by FERC, $170 per kW.
The values are discounted at 6-7/8 percent to give the present worth
as of the Watana power-on-line date. The lOO-year capital recovery
factor is then applied to the summation to give the equivalent annual
capacity benefit from interconnection.
This figure is not an absolute maximum capacity, but rather a
reasonable limit for the Devil Canyon-Fairbanks segment based on
acceptable line loss.
C-69
TABLE C-23
INTERTIE CAPACITY BENEFITS
Capacity Capacity Present
Year Saving Value Worth
(MW) ($1 ,000) ($1 ,000)
1991 90 15,300 18,700
1992 96 16,300 18,600
1993 101 17 ,200 18,400
1994 107 18,200 18,200
1995 114 19,400 18,200
1996 121 20,600 18,000
1997 128 21 ,800 17,900
1998 30 5,100 3,900
1999 through 2041 12 2,000 27,300
Total ($1,000) $159,200
Annua 1 Benefit ($1,000) $ 10,959
The other aspect of interconnection discussed in the original
feasibility report was the capability for transfer of energy from the
low energy cost producing load center to the high cost area. The
transfer allows a cost saving equal to the differential cost of energy
production for the amount transferred. Estimates in 1975 indicated
that energy could be transferred from Anchorage to Fairbanks for a
cost saving of 2.48 mi 11 s/kWh. The 1978 estimates by FERC indicate
that coal will be cheaper in Fairbanks than in Anchorage with the
result that Fairbanks energy would be 2.65 mills/kWh cheaper than that
produced by coal plants in Anchorage. This reversal in 3 years high-
lights the volatility of this cost differential. For instance, if new
coal plants had to be located at some distance from the Healy coal
fields due to their proximity to Mt. IVlcKinley National Park's clean air,
the additional cost for transporting the coal would essentially eliminate
any energy cost differential. Therefore, although the opportunity
remains to take advantage of energy cost differentials through the
transfer of energy, no energy transfer benefits are claimed because of
the possibility that energy production costs in the two load centers
might well be almost equal.
PLAN JUSTIFICATION -THE BASE CASE
A summary of project costs and benefits for the proposed two stage
development as well as for Watana alone are presented in Tables C-24
and C-25. The base case set of assumptions applies.
C-7l
Development
Watana
TABLE C-24
AVERAGE ANNUAL COSTS
Interest &
Amortization
($1.000)
o. r~ & R
($1 • 000)
Watana and Devil Canyon
163.761
225.068
2.620
3.320
TABLE C-25
AVERAGE ANNUAL BENEFITS
Watana Watana and Devi 1
($1.000) ($1 .000)
Power 163.958 288.700
Recreation 100 300
Flood Control 65 65
Intertie 10.959 10,959
Employment 18.654 23,599
Total 193.736 323.623
Benefits and costs are compared in Table C-26.
TABLE C-26
PLAN JUSTIFICATION
Annual Costs ($1.000)
Annual Benefitis ($1.000)
Net Benefits ($1.000)
Benefit Cost Ratio
Watana
166,381
193.736
27.355
1. 16
C-72
Watana and
Devil Canyon
228,388
323,623
95.235
1. 42
Total (Rounded)
($1 .000)
166.381
228,388
Canyon
Devil Canyon
Last Added
63,007
129.887
67,880
2.09
These figures indicate that, given the base case assumptions, the
Watana-Devil Canyon system is economically justified; the Watana
project first added is economically feasible by itself; and Devil
Canyon is incrementally justified on a last added basis.
SENSITIVITY OF PROJECT JUSTIFICATION
This section presents the results of various sensitivity tests
conducted to determine the impact on the project's economic justi-
fication of possible departures from the basic set of assumptions
that underlie the calculation of benefits and costs. Each test was
conducted using the same procedures as described earlier in this
section, but with certain specific assumptions altered as outlined in
the following paragraphs.
Comparability Test
The power values for the base case are computed using the most
likely means of financing the various thermal alternatives. These
included municipal, REA, and Alaska Power Authority financing. This
test examines project justification when the power values are calculated
on the basis of thermal alternative financing at the same rate applied
to the hydropower alternative, the Federal discount rate of 6-7/8 per-
cent. Using power values based on Federal financing, the average annual
power benefits are $264 million, a decrease of 9 percent. The hydro
project costs and nonpower benefits are already based on the Federal
discount rate and therefore remain unchanged. The effect on project
justification is noticeable; net benefits fall from $95 million to $71
million, while the justification ratio becomes 1.31.
With Federal financing, Watana alone offers net benefits of $14
million and a justification ratio of 1.08.
Alternate Discount Rates
The rate at which future project benefits are discounted and at
which interest during construction is calculated can affect the com-
parison of projects. The discount rate to be used in the evaluation
of Federal water resource projects is established annually and is
pegged to the interest rate on long-term government bonds. This serves
as an approximation of the opportunity cost of Federal funds. The
established rate has risen to the current value of 6-7/8 percent,
reflecting the influence of inflation.
In order to determine the magnitude of impact a different discount
rate would have on the project's economic justification, benefits and
C-73
Variations in the Load Forecast and Project Timing
The base case set of assumptions incorporates the mid-range load
forecast because it has been judged to reflect the most likely future
power requirements. The actual demand for electrical power, however,
will almost certainly depart from the mid-range forecast, and it is
important to determine how such departures can effect the viability of
the project. A significant departure on the low side could have several
results. The first, and most likely, would entail a planned delay in
the start of project construction when it became apparent that the load
was not growing as rapidly as expected. Another possibility would be
that the departure from anticipated growth only becomes apparent after
construction has already begun. In this case, the construction period
would be stretched out so that the project is not completed until the
project's power is needed. A third possibility would be to postpone
or cancel other generating resource additions with shorter lead times.
The last and potentially most damaging possible circumstance would
entail the sudden slackening of load growth immediately after the project
was completed.
If, on the other hand, the load requirements grow more rapidly
than expected, Susitna power would be needed earlier than presently
planned. The Watana project, however, probably cannot be completed
any earlier than the planned 1994 power-on-line date, and the Devil
Canyon project cannot be completed earlier than 4 years after Watana.
To assess the impacts of these various circumstances, the load-
resource analysis was conducted using the low and high range forecasts.
With the low range forecast, the initial project continues to be required
as soon as it is available, ie., 1994. A coal-fired steam plant addition
in 1997 is no longer needed, but Devil Canyon is still required in 1998.
The net effect is that Susitna capacity is absorbed at a slower rate,
and power benefits fall 3 percent to $280 million. Net benefits become
$87 million and the benefit-cost ratio is 1.38.
As noted above, the most damaging possibility in terms of project
economics would occur if there was a sudden decrease in the rate_of load
growth immediately after power-on-line. This would mean that Susitna
power would be needed less rapidly, and less Susitna capacity would
be usable in the early years. In the base case, Susitna power is fully
absorbed in the railbelt system by 2002. The annual growth rate in
peak load during the period between power-on-line and 2002 is 4.6 per-
cent. In the low-load growth case, Susitna power is absorbed over a
longer period, between 1994 and 2010. The annual growth rate in peak
load for this case is 1.9 percent. Additional cases were analyzed to
determine how low the growth rate would have to be before the power
benefits declined to the point that the project would no longer be
C-75
during construction assume that flue gas desulpherization would be
required. Mid-1976 costs from the WPPSS study were increased to
October 1978 using the Handy-Whitman Steamplant cost trends and a 1.8
Alaska factor to account for cost differentials. The resulting com-
posite investment cost estimate of $1,644 per kilowatt for the 450 and
230 MW plants in Anchorage and Fairbanks respectively was used in the
calculation of power values in lieu of the FERC composite estimate of
$1,299 per kilowatt. This resulted in an increased capacity value.
See Exhibit C-4. Using the adjusted value results in a $40 million
increase in the power benefit. Net benefits rise to $135 million, and
the benefit-cost ratio becomes 1.59.
Oil-Fired Thennal Alternative
, As discussed in a previous section, oil-fired generation is not the
most appropriate alternative for derivation of power values. National
energy policy priorities strongly suggest that coal-fired generation
is the likely and proper alternative to hydropower in the mid-1990's
and beyond. Since oil-fired power values were provided by FERC along
with coal values, however, and since the Office of I~anagement and
Budget raised questions specifically addressing the sensitivity of
project justification to oil prices, power benefits were also calcula-
ted using oil-fired power values.
In Anchorage, FERC reports that the likely oil-fired alternative
is a combined cycle plant consisting of four units of 105 MW each.
The service life is 30 years, and the heat rate is 8,350 BTU/kWh. The
investment cost is estimated at $360 per kilowatt, while the oil fuel
cost is $3.00 per million BTU.
For Fairbanks, the oil-fired alternative is a regenerative com-
bustion turbine with four 60 MW units. The service life is again 30
years, while the heat rate in this case is 10,000 BTU/kWh. The invest-
ment cost is $265 per kilowatt, and fuel is estimated at $2.00 per
mi 11 i on BTU.
The composite railbelt oil-fired power values with public, non-
Federal financing are $43.95 per kilowatt and 26.92 mills per kilowatt
hour. Power benefits amount to $212 million which is 27 percent less
than the base case. The corresponding benefit-cost ratio is 1.08, with
net benefits of $18 million.
C-77
Inflation
The economic evaluation procedures normally followed in Federal
water resource studies ignore the effects of inflation and escalation. 1/
The implicit assumption is that price level changes will impact equally-
on all alternatives being compared. In time of relatively stable
prices, this is a reasonable simplifying assumption.
Ever since the 1930's, however, there has been an accelerating
rise in costs in the United States. Nationwide, the annual increase
in construction costs from 1970 to 1976 approximated 10 percent. The
Anchorage composite consumer price index has increased at an annual
rate of 4 percent since 1960 and at almost 7 percent since 1970. In
spite of possible temporary periods of price stability, it appears that
substantial inflation may become a regular aspect of the economic scene.
The extent and persistence of inflationary trends indicates the need
to examine their effect on the comparison between hydroelectric and
thermal generation.
Inflation does not affect hydro and thermal alternatives equally
because there is a differential susceptibility to rising prices. The
extent of these differential impacts is determined by adjusting the
capacity and energy values as well as the hydro project costs to account
for inflation. A distinction has to be made between interest and
amortization costs on the one hand and all other charges on the other,
because the affect of inflation on these two categories of expenditure
is quite different. The latter category is addressed first.
A multiplier is developed for adjustment of annual charges associated
with operating costs, fuel costs, insurance, interim replacements, and
taxes. Expenditures for these items are continually susceptible to
rising prices. The initial annual expenditure associated with these
cost components in the base year is the value used in the standard
method of computing power values. With inflation, a higher figure
must be used, since the annual expenditures increase from year to
year. The assumed rate of inflation, the duration of the assumed
inflation, and the discount rate together determine how large the increase
will be. The appropriate adjustment multiplier is found by computing
the sum of the present values of the inflated payments, and dividing
that by the sum of the present values of the yearly payments without
inflation. The resulting quotient is the multiplier by which the
fixed initial payment of the standard method must be adjusted to take
inflation into account.
Throughout this report, lIinflation" refers to increases in the
general price level, while lIescalation" refers to real price changes
or changes over and above increases in the general price level.
C-78
For this analysis, inflation is assumed to prevail for a period
of 15 years beyond the initial project's power-on-line date. This
period of inflation is assumed to be followed by a period of stable
prices to the end of the 100 year economic life of the project. 1/
Inflation rates of 3 and 5 percent have been adopted as reasonable
values with which to explore the magnitude of inflationary impact. The
corresponding annual expenditure multipliers for a discount rate of
6-7/8 percent are 1.34 and 1.64.
The second type of cost to examine is the interest and amortization
charge. During the life of a hydroelectric project, an alternative
thermal plan with a life of only 30 to 35 years will have to be replaced
at least twice. Each time it is replaced, its cost will have risen
in keeping with the compound rate of inflation. The multiplier
reflecting the increase in these capital expenditures resulting from
inflation ;s found by dividing the present worth of the interest and
amortization with inflation affecting future replacements by their
present worth without inflation. Again, inflation is confined to the
first 15 years beyond power-on-1ine with stable prices assumed there-
after. The multipliers are 1.08 for 3 percent inflation and 1.15 for
a 5 percent rate.
TABLE C-27
INFLATION ADJUSTMENT MULTIPLIERS
(6-7/8 percent discount rate, 30 year thermal plant
life, 15 year period of inflation)
Cos t Category
Variable Costs
Capital Expenses
Inflation Rate
3% 5%
1.34
1.08
1.64
1. 15
These multipliers are then applied to the various cost components
of the power values and to the elements of the hydro project cost as
shown in Exhibit C-4. Note that the multiplier for interest and
amortization of the hydro project is unity. This occurs because the
hydro project does not have to be replaced during the period of analysis
and is therefore not susceptab1e to inflating prices.
l! Inflation in the years prior to power-on-1ine is ignored because
there is little differential inflation impact before costs are
actually incurred. Battelle in Alaskan Electric Power, March 1978,
page 6-3, reports that prices for thermal powerp1ants have risen
since 1970 at almost exactly the same rate as that for hydroelectric
facil ities.
C-79
Fuel Escalation
In deriving power values for use in benefit analysis, FERC uses
present day costs for the fuel requirements of the thermal plant. Even
after inflation is taken into account, this procedure is not equitable
in a period of sUbstantial fuel cost escalation, when fuel prices
rise faster than the general price level. Whereas a hydro development
will continue to produce its energy from falling water without cost,
a thermal plant depends on fossil fuels that are susceptible to real
price increases as well as to inflationary trends. Depleting supplies,
intensified environmental controls, cartelized production, and the
need to go further and deeper for supplies all tend to boost prices
at rates higher than inflation.
Fuel Oil: As a practical matter the world oil market is controlled
by the Organization of Petroleum Exporting Countries (OPEC). The OPEC
cartel pricing strategy appears to be based on their perception of the
marginal costs of production of their nearest competitor. This policy
is intended to maximize their long-term profits. 1/
In the future OPEC's most probable strategy (assuming the cartel
can be sustained and no other super-giant oil fields are found or
alternative lower cost technologies are developed) will be to escalate
its prices paralleling the market rate of interest occurring in its
western world market area. The market rate of interest sets the basis
from which OPEC can measure its opportunity cost and escalates at
approximately 3 percentage points higher than the general inflation
rate as measured by the GNP deflator. Thus for a general 5 percent
per annum inflation rate, the OPEC oil price increase rate would be
expected to be about 8 percent per annum.
If Mexico enters the continental market as a major source, it will
probably shave prices slightly to gain market entry by displacing
Middle East crude, but then generally trade at OPEC's world market
price.
Another possibility is the collapse of the OPEC cartel. Iran and
Saudia Arabia, the largest oil producers in OPEC, are committed along
with many other OPEC nations to rapid economic development programs.
These programs are dependent upon oil export revenues for their fund-
ing. Under the umbrella of OPEC's pricing policy, there is opportunity
and strong incentive to develop substantial new productive capacity
both within and outside the cartel. The increase in capacity imposes
This discussion of fuel price behavior is based largely on a March
1978 report by Battelle Pacific Northwest Laboratories entitled,
Alaska Electric Power, An Analysis of Future Requirements and Supply
for the Railbelt Region and on discussions with Ward Swift of Battelle.
C-80
downward pressure on prices. To offset this pressue and maintain the
cartel price, production must be cut back somewhat; principally this
will fallon the largest producers, Iran and Saudia Arabia in this case.
Thus they are caught in a d"ilemma between a decl ining market share
and the need for export earnings for developmental programs. This
situation could lead to price wars to regain market shares and thus
the collapse of OPEC as an effective cartel.
Price cutting has a theoretical floor -the marginal cost of
producing the level of output demanded at such a market price. This
would likely be determined by Mexico, the North Sea producers and the
costs of increased production in Iran. All of the conditions con-
tributing to the initial cartelization would still be present, a highly
concentrated market and very inelastic commodity demand. Thus a
collapse might only be temporary and under this scenario, world prices
could become rather volatile.
Given the many vested (U.S. and foreign) interests in maintaining
oil prices, a major downward break in oil prices is not likely. As a
case in point, if Saudi Arabia went back to pre-1973 prices, and could
satisfy demand, (not likely at those prices) both North Sea and North
Slope production could be shut in.
Given that scenario and without governmental intervention, U.S.
and other nations' dependence on foreign oil would increase markedly,
domestic exploration and field devel~pment would be severely cut back,
and consumption would increase. Although existence of contingency
policies to respond to such a case are unknown, it is hard to visualize
that very rigorous governmental intervention would not occur either
through import quotas or duties that would maintain the economic
viability of the domestic industries.
In 1977, the domestic refinery acquisition cost of domestic crude
was about 35 percent less than that of foreign crude ($9.20 per bbl
versus $14.10 per bbl). A price decline of greater than 35 percent
is deemed highly unlikely for the reasons outlined above.
Coal: Coal prices in Alaska appear much more predictable due to
the absence of regulation and the currently limited influence of
marketability factors.
Two sources of coal supply for the rail belt region are most per-
tinent to this analysis:
1. The Healy coal field is currently being mined by the Usibelli
Coal Company at about 700,000 tons/year with plans for expansion to
1.5 million tons per year. This mine currently supplies the Golden
Valley Electric Association (GVEA) plant located at Healy and the
Fairbanks Municipal Utility System in Fairbanks.
C-81
2. A potential future coal source is the Beluga field in the Cook
Inlet region. The latter field is known to contain very substantial
reserves but the new mine development required will be costly due to
lack of transporation facilities and mine supporting infrastructure.
The Healy coal field is the obvious supplier for future interior
generation based on coal. Recent cost of coal delivered by truck to
the GVEA Healy plant is $0.80/MMBTU and by rail at Fairbanks, $1.15/
MMBTU. 1/ Although the Healy site may be able to expand to perhaps 200
MW capacity, its location 4.5 miles from Mt. McKinley l~ationa1 Park
may restrict further development due to air quality considerations.
Thus further coal fired expansion in the upper rail belt most probably
will necessitate plant location in the Nenana area along the rail
line. In this case, additional costs above mine mouth costs, will
be incurred including tipple costs (approximately $0.11 per MMBTU
currently) and Alaska Railroad tariffs. The latter may be reduced if
unit trains were to be employed.
The Usibelli Coal Mine, Inc. has indicated that they expect their
prices to rise at about 7 percent per annum. This pricing schedule
appears reasonable if it is assumed that a 5 percent per annum general
inflation rate continues and a 2 percentage point markup escalation
is appropriate for the resource owner.
The Beluga/Susitna coal field is an obvious source of supply for
coal fired generation. The reserves are very large and capable of
supporting a world scale mine for export and mine mouth power generation.
The coal is subbituminous (Rank C) and of relatively low heating value
(7,100 BTU/lb) at run-of-mine but quite low in sulfur (0.15 percent
typical). Coal preparation including washing and drying could raise
the heating value to 9,000 BTU/lb. Some of the coal will be of too
low a quality for export but would nevertheless be suitable for moine
mouth power generation.
Fuel Cost Assumptions
To calculate the impact of relative changes in the price of fuels
on project feasibility, adjustments are made to the power values
upon which the calculation of power benefits is based. The period
from 1978 to the initial project power-on-1ine date is looked at
separately from the period after POL. For the initial period, the
estimated 1978 fuel price is compounded at the assumed annual escala-
tion rate to give the anticipated constant dollar fuel cost at the
time of power-on-line. The energy and capacity values are then recal-
culated using standard FERC procedures. For the post-POL period, a
multiplier is used to adjust the energy value using procedures identical
to those used to adjust for inflation. The period of escalation is
limited to the years prior to the 30th year after power-on-1ine.
Thirty years corresponds to the service 1 ife of the initial thermal
plant.
1/ September, 1978
C-82
Three sample cases are analysed. First, for both coal and oil,
there is an assumption that fuel costs escalate at 2 percent per year
between 1978 and the 30th year after power-on-line, after which there
is no additional escalation. The 2 percent rate is selected as repre-
sentative of long-term real price increases arising from depleting,
more distant sources, increasing environmental safeguards in extra-
ction, processing and handling, and anticipated producing nation pricing
policy. (Refer to the previous discussion of fuel price trends.)
The second case looks at no escalation prior to power-on-line
followed by a 3D-year period of 2 percent annual escalation. This case
is designed to reflect the possibility of a near-term softening of the
market for oil due to slackening demand or increased supply in the
short-term.
The final case explores the impact of real oil price declines prior
to power-an-line. An immediate 35 percent drop in price is assumed,
with no change in price thereafter. This scenario is included to show
the possible effect on project justification of a breakup of the OPEC
cartel. Exhibit C-4 shows how these various adjustments are made to
the energy value provided by FERC.
Test Results
The results of the sensitivity tests for inflation and escalation
are presented on Figures C-10 and C-ll. Two percent annual escalation
in the price of coal results in a 55 percent increase in net benefits
and the benefit-cost ratio becomes 1.64. In the most extreme coal-fired
case, 2 percent fuel escalation with 5 percent inflation, the benefit-
cost ratio rises to 2.17. The worst case analyzed in terms of project
justification is with the oil-fired alternative and a sudden 35 percent
drop in oil prices. The resulting benefit-cost ratio is 0.85.
Summary
In summary, it has been shown that the benefit-cost ratio is sensi-
tive to the source of financing, to the discount rate, to the type of
alternative generation, to construction delays, and to inflation and
fuel cost escalation. It is relatively insensitive, on the other hand,
to variations in load requirement forecasts. Under the full range of
forecasts, Susitna hydropower is needed as soon as it is available.
Despite the sensitivity of project economics to many of these
parameters, the degree of sensitivity is not sufficient to make the
project uneconomic, except in one case. Only if oil-fired generation
were to be considered the appropriate long-term alternative to hydro-
power and if the price of oil were to suddenly fall drastically as a
result of world market forces would net benefits of Susitna hydropower
development be less than those of the thermal generation alternative.
C-83
CORPS OF ENGINEERS u S AR~Y
-Ii
::I:
I
t-
!;t 600
~ 500 (!) w
::::E 400 0
0
o~ 300
>-200 <.!)
0::
W 100 Z
W 0
t-= u... 9,624
I
w 9,000 a::: u
<t
o o q.
8,000
7,000
W 6,000
<.!)
<t
0:: o
I-
CI)
5,000
4,000
3,400
WATANA GE NE RATION
~
I • ~ M a • .a
A IA I AliA ~ ~ M ~ ~ ~ ,-~ \ lA,~ ~\ ~ A IA .A j .A A ... • l
\J '~ ~\j ~ , IF, ~ " , \ , .. I' , , r 1 , , 'y. ''.1 '\KV V V rv-~V ~ -1 1 " ,. , ...
1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977
WATANA STORAGE
r I ~ , l r l r ~ , ,. ~ , l I ~ , ~ / ~ J ~ /' l ~ , lL l L ~ L~ , , \ \ r \/ \ 1\ J
r 1\ r \/ \ \ r \/ \/ \1 \/ 1\ / ~I 1\ / 1\ \/ \~ ~
\ t ~ V V 1 , I ~ Y y y y y l V , y V \ I \ r\ ~ lJ • , , , (~ 1\ \ , I ~ 1\ J
\ \ \ \ , \ I • \ , 1 ~ 1 \, \/
1 , 11 V
1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977
SOUTHCENTRAL RAILBELT AREA, ALASKA
SUPPLEMENTAL FEASIBILITY STUDY
UPPER SUSITNA RIVER BASIN
RESERVOIR OPERATION a ENERGY OUTPUT
WATANA DAM
ALAS.A DISTRICT, CORPS OF ENGINEERS
ANCrlORAGE, ALAS.A
NOVEMBER, '978
PI ATE C-l
CORPS OF ENGINEERS U S. ARMY
2
:::z:::
tL
~ 600
~ 500 (!)
ILl
~ 400 0
0 q 300
> 200 (!) a::
UJ 100
Z
UJ 0
.,..:
1,250 u..
I
ILl a:::
1,000 u
cl
8 750 q
UJ 500
(!)
< a::: 250
0 .-
(fJ 0
DEVIL CANYON GENERATION
n ~ ~ jl .. j ..
~ & -'" I\-~ .& 1I'l "-~ Vl ~ ~ ~ h ~, ~ W A JI'\. fi .a....L .... .. ...
II'--"-~ r-• " ~, ~ ... ""\"..0 ~ \. J 'r-'-" ~ -~, ~, ~, /)
1950 1951 1952 195~ 1954 1955 1956 1957 1958 1959 1960 1961 1962 196~ 1964 1965 1966 1967 1968 1969 1970 1971 1972 197~ 1974 1975 1976 1977
DEVIL CANYON STORAGE
-------r---rr---~V --
1950 1951 1952 195~ 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977
SOUTHCENTRAL RAILBELT AREA, ALASKA
SUPPLEMENTAL FEASIBILITY STUDY
UPPER SUSITNA RIVER BASIN
RESERVOIR OPERATION a ENERGY OUTPUT
DEVIL CANYON DAM
ALASKA cISTRICT, CORPS OF ENGINEERS
ANCHORAGE, ALASKA
NOVEMBER,I'I78
PLATE C-2
EXHIBIT C-l
LOAD RESOURCE ANALYSES
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1 2b2.
1
1
1
52.
1 11311.
1
1
1
1
o.
O. 1 90.
PEAK PtAI< LOAO/I;;EHt'RATlNG CAPACITY i<EGlUIREI-lEr.TS("1EGAtlATTS)
~puF MAX'~u" PLa.T UlILIlAlIU~ FAC1U~
APUF ACT~AL PLA~I ulILIZATlO~ FACTO~
198&-1987
~""~ APUF
• 511 .50
• 15 .5&
• 50 .2&
.15 .00
E'~EIo/Gr --GU~tIo/ATHk/"'II'~UAL E~,f.I<GY hEI.iUIREMENTS(MILLluNS OF KILUIjATl-HOURS)
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4b57.
5111 •
2259 •
1958 •
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4727.
11727.
70.
4&57 •
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I
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CO
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FAI.~~~'S CAS,: l --~EOluM L~A~ ~RO~T"
I ,l,,"'fl~ tt~l/: 19"'2.
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CilITICAL
1
1 Pt::API
1------------_._------,
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-----------·---1 ~t::~Ov~CES 1
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I
TOTAL I 3&0.
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"YIJRJ 1
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/
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/
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/
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/
/
/
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.::'() .,0
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/
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/
/
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42". /
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/
114'1. /
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/
/
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/
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/
/
114'1. I
/
I O.b(ot
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I 08.
I
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/
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1l3. /
313. /
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115. /
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/
/
/
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/
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/
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I
1211. /
/
/
/
/
/
18. I
I
11'13. /
/
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/
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204.
22.
0.523
12.
14.
350.
o.
P~AK PiAPI LOAD/GE~~RArl~~ CAPACITy kEQUlREME~TS(MEG~wATTS)
~PUF M~~lMuM PL~~T UTILllArI0~ fACTOI'<
~PIIF A('TwAL PLIO'.T ullLllATlON FACTUI<
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.50 .50
• 'S ."
• 50 .111
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E"EF<GY --Gt:lIt,IoIA' lur,/A .. ,.UAL ENERGY kEvU}I<EMEI'4TS(MILLIO'4S OF KlLOI"" H-I"iu~S)
1l54.
o.
1018 •
254 •
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ll13.
1213.
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---------------1 "f".ll"l"·;t. .• TS 1
---------------1 wEl>(luRCE"
ExI"TlNu
t1."Jttl.S I
Htl'IIELEC I
(;O'Il>.TuRt!l!.E I
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1
1 J 211.
TOTAL 1 t 452.
I
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fiTUilO
STEA~/ELEC 200.
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/
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I
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I
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/
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/
. f! RE SUURCE ~ .' 1301.
1
1 u.
I
I
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1407-a''8b
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.~I) _!l0
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.~O _.o!1O
.15 _.00
• 15 _cO
1
1 I-EAI\
1------1
/ 1192.
I
I
I
I SIC..
2413. 1
1780. I
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/
/
I
I
I
I
/
I
I
/
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I
I
I
/
/
I
/
I
1513.
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I
75. I 60.
I
1196':'. I Illb.
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1
1
1
510. 1
325Q. 1
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5393. I
/
1
I
I
I
I
/
I
I
I
1I. I
I
I
I
53'13. I
I
I
/
I
I
80. /
I
5313. I
/
I
I
I
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1573.
lOO.
1173.
Jib.
63.
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130.
PEAK --PtAII LOA."GEI>jt:AA TI NG CAPAC ITT HEQUIWEMEJ.HHMEGA,ooA TtS)
~'''IIf' --"'Ani~UM II" ....... T UlIt..IlAtIU ... f ,ilCTOR
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.75 .bl>
.;0 .11>
.15 .00
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f~E~G' -. Gt~LRA •• O~/ANN~AL E~E~GT REQUIRE~ENrS(MILLIONS OF KILO~AT'-HOU~S)
510.
3145.
Illu • o •
5l75.
J50 •
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85.
5&4t •
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('"')
I
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--' o
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1 • T r.: w I 1 c. t C. " k : 1':;' -'-de.
"UT~:.::.uv. ~4J. I'i-"fl! ,,1 u.S.-l<;"4.
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-------.-----.---------------------------~-----------------------------------------------1
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1---------------------1 "'t"J'.II~E,·t IfS 1 ~O<l.
---------------1 wE:>OvI'CES 1
lU:'Il,~G I
HYI)HO I
::.H.A ~/ElEC 1
t(I",~. T'j.(oI'4t I
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1
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1
AvOlTIO",S I
HYVlm I
SH.AMELEC I cu •• e. Tuijblf.E I
DIeSEL I
I
liE. T lI(E" 'H S I
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S Tt: ~ '1liLlC I
C 0 '''~. r L1I<tll r,t: 1
l! IE SEL I
I
---------------1 b!il,:;:' ~ESO\lR(;ESI 43&.
I
(;A~ ~ES. ~A~&l~1 11.452
I
HE:.E"VE kE~. I 1~.
I
lOSSES I I,.
lRANl)FEREO
SUI<PlUS
I
1
1
I
I
I
o.
l'h,7-I"bb
H'uF AP,lf
.50 .5il
.15 • ."i
• ~(\ • 11
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E •• E~G' I PEA .. .-------1------
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I
I
I
O. 1
1 n<;. 1
1 ~t>. I
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1335. I
I
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I I".
I
I
I
I
I
I <;.
I
I 22.
I
I
1335. I 419.
I
I 0.334
I
I 79.
I
211. I 10.
I
1115. I 325.
I
I II.
I
I
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.. PuF APl,f
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.75 • b8
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• 75 .20
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I
" .. E-<bY I PEAK --------/------
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I
I
I
O. I
11<;/1. I
17e. I
O. I
I
1312. I
I
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25. I
I
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I
21. I
I
B1b. I
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82.
lb.
421.
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PEAl<, PtA .. 1.0A()J'Gfl.E,UTlh\j, CAPACITY rlEwIJlRE.",ENTS(MEGA .. aHS)
Iwm MAX1~HJ'" PLl.H tHILIlATIUN f.CTOR
."lIf ACTuAl. 1'1.".H uTIlI1ATIOfJ fACTOI<
H!!9-1'l"11
~''',-,'' APuF
.,:)0 .50
.7':) .5<;
• ':)J .10
.Itl .110
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E"EIIGV --GtNt.il""liJ,./ANi~IJAL E",EkGY kltollIHEI'IENTS(MILlIOijS \If KIlOt'/AlT·"O(j~S)
ENERGY
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1
I PEb
1-------------·-------1 r<tl.:.lltlWt""t~.Jl" I
---------------1 "El:iOvWCES 1
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"Yvlii) 1
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1.(, •. I;;.l,jw;'Ii.f I
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1
1
1
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1
1
1
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l:il~A"lElEC I
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llll:.SEl I
I
---------------1 "IWS;:, "ESOl/liet.SI
1
CAP k~5 •• u~b1t'l
I
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LOSSES
1
I
1
t 3~7.
13'1.
1<'13.
7<1'.
5.
117 3.
177 3.
0.~u7
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1
I
1
I
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1<1"0-1 .... 1
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• ">Ii .11l
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.75 .co
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• 00 .00
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1
1
1
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4193. I
1205. I
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1
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I 0.235
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Pt::A~ Pt.A" LIJA.II/",t:>lEtUT1Nb ClPlCIl'\' KEIoIUlWE"EI\ITS(""EGA .. ATTSl
f;l'uf I~H!H;J:~ ... l. ... "'T IJi1lIZATlOI\I FACfUR
A"(JF ACTtAL 1-1l..·I.'4f ,JlII.IlATIO' FACTOI(
\'i9i!-19H
"'''"F APUF
• ,)0 .50
.75 .70
• SO • I b
.15 .00
.75 .20
.00 .00
E.,EkGY --Gt.f<I:JtA.lll.J..,,.;.,WAl E"'ttibT kE!.lUIREMENT5(MllLIl!NS OF KIlIJWATl-110URS)
ENERGY
b90Y.
'5110 •
5159 •
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3'510.
v.
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f>907.
o.
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I ......
......
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A'[A: FIl)o(fI ...... S
f~I""~'~i~!' C~S~: ~ --"Eu" .. ,,. LOAO GROll Hi
I"l,,"ll{; IE ... : 1""~.
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CRITICAL P t .. I 0 {)
I Pt .... /---------------------1 tiE"uiili:."i:."rs / 3~$.
---------------1 KE50~~CfS 1
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MY~RO I o.
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CO"rl. T"II!:;1;;£ I 20'1.
uIlSl:L 1 u.
1
TOTAL / 519.
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S'EAM/fLtC I 32.
CO.\~. TuR& Ir.E I
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I
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:,TtAM/tLtC 1 32.
C. 1);.11<. 'Uktl J I.E 1
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I ----------_._--,
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1
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1
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5b. I
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1
I
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519.
519.
18.
430.
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"'i'liF JII'uF
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.75 .'51
.511 .10
.10 .00
15n.
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I
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11110. 1
171>. I
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1
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I
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1
I
1
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I 40.
I
I
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1591 •. I 419.
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I 0.281
I
I 75.
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PEAK --PtAK L04U'GE~lRATl~~ CAPACIty R£QUIMEME~TS(MEGA~ATTa)
IooPIJF --~'AAl"'lJM !"LA.,T UTILllAU(lN FACTO~
APOIf --ACTUAL PL .... r UTJLIZAT!O •• F.CTUR
199i!-1993
~,p ... F A"uF
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• 75 .55
• 50 .10
• to .00
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E~EtiG' --GlNtRATIO./A~HU4L E~EWG' kEYUIHEM~NTS(MILLIO.S ~F K[LO~AT'-HO~.S)
fNEkG'f
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CR1TIC"L .. £ Ii I U 0 -._-----------------------------------------.------------------------... -------_._.------
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I "I:AI\ 1-----------'----------1 "~I'UilllE" .t,T:; I lb3b.
---------------1 "i:.::'OukCES I
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LU~fi.TUNdJ~E I 55.
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I
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7151. I 2321.
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A~Tu~L PL~~I UTllilArl0~ fACTOR
1~'15-I"ib
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.IiO .110
P':AK
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6311.
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EXHIBIT C-2
LOAD RESOURCE ANALYSES (GRAPHS)
EXHIBIT C-3
USABLE CAPACITY SUMMARY
Year
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
NOTES: 1/
2/
'*
TABLE C-3-1
USABLE CAPACITY SUMMARY
(Dependable Capacity Only)
9411, Low?:! 94, Med 94, High
0 27 99
214 265 533
533 680 680
680 680 680
*858 *950 *1,151
1,023 1,035 1,347
1,143 1 ,231
1 , 178 1,347
1,321
1,339
1,347
Watana power-on-line and interconnection date.
Low, Medium or High load forecast.
Year of Devil Canyon power-on-line.
96, Med
160
476
674
680
*731
847
1 ,069
1 ,167
1 ,281
1,347
EXHIBIT C-4
POWER VALUE CALCULATIONS
TABLE C-4-l
COAL-FIRED, FERC VALUES
BASE CASE AND FUEL ESCALATION TO POL
Item of Cost Anchorage Fairbanks
Interest & Amortization 110.77 X .80 = $ 88.62 99.64 X .20 = $19.93
Interim Replacements, Insurance,
and Taxes 9.26 X .80 = 7.41 8.33 X .20 = 1.66
Annual Carrying Cost of Fuel
Inventory .91 X .80 = .73 .48 X .20 = .10
Fixed Operating Costs 14.69 X .80 = 11.75 16.29 X .20 = 3.26
Administrative & General 5.65 X .80 = 4.52 6.68 X .20 = 1.34
Transmission Cost 30.25 X .80 ::: 24.20 30.50 X .20 = 6.10
Total Capacity Cost ($/Kw) $137.23 $32.39
with Hydro Adjustment
Energy Fuel (mil s/kWh) 11.00 X .80 ::: $ 8.80 8.40 X .20 = $ 1.68
Variable O&M 1.64 X .80 = 1. 31 1.82 X .20 ::: .37
Transmission Cost .65 X .80 ::: .52 .42 X .20 = .08 ---
Total Energy Cost (mi l/Kwh) $ 10.63 $ 2.13
(B)
(A) Fuel
Base Escalated
Case l! to 1994 @ 2%
---.~ .. "~---~ --
$108.55 $108.55
9.07 9.07
.83 1.20
15.01 15.01
5.86 5.86
30.30 30.30
$169.62 $169.99
186.58 186.99
$ 10.48 $ 14.39
1.68 1.68
.60 .60
$12.76 $ 16.67
l! Base case is a composite value based on the weighted average of Anchorage and Fairbanks values.
The 80-20 proportion is derived from the relative future estimated electrical needs of Anchorage
and Fairbanks.
TABLE C-4-2
COAL-FIRED~ FERC VALUES
(F) (G)
(C) (D) (E) With 3% With 5%
With 3% With 5% With 2% Fuel Inflation & 2% Inflation & 2%
Item of Cost Inflation Inflation Escalation l! Fuel Escalation Fuel Escal
Interest & Amortization A X 1.08 = 117.23 A X 1.15 = 124.83 108.55 E X 1.08 = 117.23 E X 1.15 = 124.83
Interim Replacements~
Insurance & Taxes A X 1.34 = 12.15 A X 1.64 = 14.87 9.07 E X 1.34 = 12.15 E X 1.64 = 14.87
Annual Carrying Cost
of Fuel Inventory A X 1.34 = 1.11 A X 1.64 = 1.36 B X 1.32 = 1.58 E X 1.34 = 2. 12 E X 1.64 = 2.59
Fixed Operating Costs A X 1.34 = 20.23 A X 1.64 = 24.62 15.01 E X 1.34 = 20. 11 E X 1.64 = 24.62
n Administrative & General A Xl. 34 = 7.85 A X 1.64 = 9.61 5.86 E X 1.34 = 7.85 E X 1.64 = 9.61
I
.~
I Transmission Cost 30.30 30.30 30.30 30.30 30.30 :"-l
Total Capacity Cost
($/Kw) 188.87 205.59 170.37 189.76 206.82
with Hydro Adjustment 207.76 226.15 187.41 208.74 227.50
Energy Fuel A X 1.34 = 14.04 A X 1.64 = 17.19 B Xl. 32 18.99 E X 1.34 = 25.45 E X 1.64 = 31. 14
Variable O&M A X 1.34 = 2.25 A X 1.64 = 2.76 1.68 E X 1.34 = 2.25 E X 1.64 = 2.76
Transmission Cost .60 .60 .60 .60
Total Energy Cost
(mil/Kwh) 16,89 20.55 21.27 28.30 34.50
l! Fuel escalates from 1978 to POL and from POL through 30-year life of initial thermal pl ant.
TABLE C-4-3
COAL -FI RED, FEDERAL FINANCING, & APA INVESTMENT COST
(I) (J)
(H) APA APA With 30/ /0
Federal Investment Inflation & 2%
Item of Cost Fi nand ng Cost Fuel Escalation
Interest & Amortization 101. 73 137.77 148.79
Interim Replacements,
Insurance & Taxes 11. 51 15.42
Annual Carrying Cost
of Fuel Inventory .71 .83 1. 78
Fixed Operating Costs 15.01 15.01 20. 11
(""') Administrative & General 5.86 5.86 7.85 I
-Po
I Transmission Cost 26.93 30.30 30.30 w
Total Capacity Cost ( $/Kw) 150.24 201.28 224.25
with Hydro Adjustment 165.26 221. 41 246.68
Energy Fuel 10.48 10.48 21.40
Variable O&M 1. 68 1. 68 2.25
Transmission Cost .60 .60 .60
Total Energy Cost (mil /Kwh) 12.76 12.76 24.25
TABLE C-4-4
OIL-FIRED, FERC VALUES
(K) (L)
Fuel Escalation No Inflation,
Item of Cost to 1994 No Escalation
Interest & Amortization 29.22 29.22
Interim Replacements,
Insurance & Taxes 2.55 2.55
Annual Carrying Cost
of Fuel Inventory 2.52 1. 75
Fixed Operating Costs
("')
I Administrative & General 2.98 2.98 ,.f:::.
I
+=>-
Transmission Cost 5.36 5.36
Total Capacity Cost ($/Kw) 42.63 41.86
with Hydro Adjustment 44.76 43.95
Energy Fuel 33.28 24.24
Variable 0&r1 1. 70 1. 70
Transmission Cost .98 .98
Total Energy Cost (mi l/Kwh) 35.96 26.92
TABLE C-4-5
OIL-FIRED, FERC VALUES
(Q) (R)
(M) (N) (P) With 3% \-Ji th 5%
With 3% With 5% With 2% Fuel Inflation & 2% Inflation & 2%
Item of Cost Inflation Inflation Escalation Fuel Escalation Fuel Escalation
--.~
Interest & Amortization L X 1.08 = 31.56 LX1.15= 33.60 29.22 P X 1.08 = 31.56 PX1.15= 33.60
Interim Replacements,
Insurance & Taxes L X 1.34 = 3.42 L X 1.64 = 4.18 2.55 P X 1. 3~ = 3.42 P X 1.64 = 4.18
Annual Carrying Cost
of Fuel Inventory L X 1.34 = 2.35 L X 1.64 = 2.87 K X 1.32 :: 3.33 P X 1.34 = 4.46 P X 1.64 = 5.46
Fixed Operating Costs
n Administrative & General L X 1.34 = 3.99 L X 1.64 = 4.89 2.98 P X 1.34 = 3.99 P X 1.64 = 4.89
I
-P:.
I Transmission Cost 5.36 5.36 5.36 5.36 5.36 c.n
Total Capacity Cost
($/Kw) 46.68 50.90 43.44 48.79 53.49
with Hydro Adjustment 49.01 53.45 45.61 51.23 56.16
Energy Fuel L X 1.34 = 35.48 L X 1.64 = 39.75 K X 1.32 =43.93 P X 1 .34 :: 58.87 P X 1.64 = 72.05
Va riab 1 e O&M L X 1.34 = 2.28 L X 1.64 :: 2.79 1. 70 P X 1.34 :: 2.28 P X 1.64 = 2.79
Transmission Cost .98 .98 .98 .98 .98
Total Energy Cost
(mil/Kwh) 38.74 43.52 46.61 62.13 75.82
TABLE C-4-6
OIL-FIRED, FERC VALUES, FUEL ESCALATION AFTER POL
(T) (U)
(S) With 3% With 5%
Without Inflation & 2% Inflation & 2%
Item of Cost Inflation Fuel Escalation Fuel Escalation
Interest & Amortization 29.22 S X 1.08 = 31.56 SX1.15= 33.60
Interim Replacements,
Insurance & Taxes 2.55 S X 1.34 = 3.42 S X 1.64 = 4.18
Annual Carrying Cost
of Fuel Inventory
(2% Esc after POL) L X 1.32 = 2.31 S X 1.34 = 3.10 S X 1.64 = 3.79
n Fixed Operating Costs
I
+=:0 Administrative & General 2.98 S X 1.34 = S X 1.64 = I 3.99 4.89 en
Transmission Cost 5.36 5.36 5.36
Total Capacity Cost ($/Kw) 42.42 47.43 51.82
with Hydro Adjustment 44.54 49.80 54.41
Energy Fuel
(2% Esc after POL) L X 1.32 = 32.00 S X 1.34 = 42.88 S X 1.64 = 52.48
Variable O&M 1.70 S X 1.34 = 2.28 S X 1.64 = 2.79
Transmission Cost .98 .98 .98
Total Energy Cost (mi l/Kwh) 34.68 46. 14 56.25
TABLE C-4-7
OIL-FIRED, FERC VALUES, FUEL COST DECLINE OF 35%
(W) (X)
(V) With 3~& With 5%
Without Inflation & 2% Inflation & 2~h
Item of Cost Inflation Fuel Escalation Fuel Escalation
Interest & Amortization 29.22 V Xl. 08 :; 31. 56 VX1.15:; 33.60
Interim Replacements,
Insurance & Taxes 2.55 V X 1.34 :; 3.42 V X 1.64 :; 4. 18
Annual Carrying Cost
of Fuel Inventory 1. 19 V X 1.34 = 1. 59 V X 1.64 :; 1. 95
('"') Fixed Operating Costs
I
.+:00 , Administrative & General 2.98 V X 1.34 :; 3.99 V X 1.64 = 4.89 ""-.J
Transmission Cost 5.36 5.36 5.36
Total Capacity Cost ($/Kw) 41.30 45.92 49.98
with Hydro Adjustment 43.37 48.22 52.48
Energy Fuel 15.77 V X 1.34 :; 21. 13 V X 1.64 :; 25.86
Variable O&M 1. 70 V X 1.34 = 2.28 V X 1.64 :; 2.79
Transmission Cost .98 .98 .98
Total Energy Cost (mil/Kwh) 18.45 24.39 29.63
("")
I
~
I co
Cost Item
Interest and Amortization
Operation and Maintenance
Replacement
Total
TABLE C-4-8
HYDROPOHER COSTS WITH INFLATION
($1,000)
No Inflation
216,671
2,890
430
219,991
37~ Inflation
X 1 = 216,671
X 1. 34 = 3,873
X 1.34 = 576
221,120
5~~ Inflation
X 1 = 216,671
X 1.64 = 4,740
X 1.64 = 705
222,116
EXHI BIT C-5
POWER BENEFIT CALCULATIONS
EXHIBIT C-6
INVESTMENT COST CALCULATIONS
TABLE C-6-1
INVESTMENT COST WITH 2 YEARS CONSTRUCTION DELAY
(in thousands of dollars)
Watana Devil Can~on Grav;t~ Dam
Accumulated Present Worth Accumulated Present Worth
Year Expenditure Expenditure IDC Expenditure of Expenditure Expenditure IDC of IDC
1984 30,500 1,048
1985 107,000 30,500 5,775
1986 114,000 137,500 13,372
1987 159,000 251,500 22,756
1988 214,500 410,500 35,595
1989 208,000 625,000 50,119
1990 230,000 833,000 65, 175
1991 245,000 1,063,000 91,503
("") 1992 223,000 1,308,000 97,591 I
0"'1 1993 161,000 1,531,000 11 0,791 I
1994 32,000 1 ,692,000 117,425 39,000 39,000 1 ,341 1 ,341
1995 25,000 1,724,000 119,384 98,500 98,500 39,000 6,067 6,067
1996 16,000 1,749,000 120,794 117,000 117,000 137,500 13,475 13,475
1997 1,765,000 1,765,000 851,328 137,000 128,187 254,500 23,581 22,064
1998 144,000 126,070 391 ,500 38,191 33,436
1999 158,000 129,428 535,500 43,622 35,734
2000 129,500 99,258 693,500 53,505 41,010
823,000 737,443 823,000 179,784 153,127
Watana Devil Can~on Total Watana & Dev; 1 Can~on
Construction Cost $1,765,000 $737,443 $2,502,443
I.D.C. 851,328 153,127 1,004,455
Investment Cost $2,616,328 $890,570 $3,506,898
Interest and Amortization $ 180,106 $ 61 ,307 $ 241,413
Operation, Maintenance, and
Replacement 2,620 700 3,320
Average Annual Cost $ 182,726 $ 62,007 $ 244,733
TABLE C-6-2
INVESTMENT COST WITH 8% DISCOUNT RATE
(in thousands of dollars)
Watana Devil Canyon Gravity Dam
Accumulated Present Worth Accumulated Present Worth
Year EXQenditure EXQenditure IDC EXQenditure of EXQenditure EXQenditure IDC of IDC
1984 30,500 1,220
1985 107,000 30,500 6,720
1986 114,000 137,500 15,560
1987 159,000 251,500 26,480
1988 218,500 410,500 41 ,580
1989 214,000 629,000 58,920
1990 248,000 843,000 77 ,360
1991 258,000 1 ,091 ,000 97,600
n 1992 223,000 1,349,000 116,840 39,000 39,000 1 ,560 1,560 I
0'1 1993 161,000 1 ,572,000 132,200 98,500 98,500 39,000 7,060 7,060 ~ 1994 32,000 1,733,000 139,920 117,000 117,000 137,500 15,680 15,680
1995 1,765,000 1,765,000 714,400 137,000 126,852 254,500 25,840 23,926
1996 144,000 123,457 391,500 37,080 31,790
1997 158,000 125,425 535,500 49,160 39,025
1998 129,500 95,186 693,500 60,660 44,587
823,000 725,420 823,000 197,040 163,628
Watana Dev; 1 Can~on Total Watana & Dev; 1 Can~on
Construction Cost $1,765,000 $725,420 $2,490,420
I.D.C. 714,400 163,628 878,028
Investment Cost $2,497,400 $889,048 $3,368,448
Interest and Amortization $ 198,442 $ 71.156 $ 269,598
Operation, Maintenance, and
Replacement 2,620 700 3,320
Average Annual Cost $ 201 ,062 $ 71,856 $-272-,918
TABLE C-6-3
INVESTMENT COST WITH 5% DISCOUNT RATE
(in thousands of dollars)
Watana Devil Canton Gravitt Dam
Accumulated Present Worth Accumulated Present Worth
Year Expenditure Expenditure IDC Expenditure of Expenditure Expenditure IDC of DC
1984 30,500 763
1985 107,000 30,500 4,200
1986 114,000 137,500 9,725
1987 159,000 251,500 16,550
1988 218,500 410,500 25,988
1989 214,000 629,000 36,800
1990 248,000 843,000 48,350
1991 258,000 1,091,000 61,000
("") 1992 223,000 1,349,000 73,025 39,000 39,000 975 975 I
0\ 1993 161,000 1,572,000 82,625 98,500 98,500 39,000 4,413 4,413 I w 1994 32,000 1,733,000 87,450 117,000 117,000 137,500 9,800 9,800
1995 1,765,000 1,765,000 446,476 137,000 130,476 254,500 19,575 18,643
1996 144,000 130,612 391 ,500 23,175 21,020
1997 158,000 136,486 535,500 30,725 26,541
1998 129,500 106,540 693,500 37,913 31,191
823,000 758,614 823,000 126,576 112,583
Watana Devil Canton Total Watana & Devi 1 Can,lon
Construction Cost $1,765,000 $758,614 $2,523,614
1.D.C. 446,476 112,583 559,059
Investment Cost $2,211,476 $871,197 $3,082,673
Interest and Amortization $ 111 ,421 $ 43,894 $ 155,315
Operation, Maintenance, and
Replacement 2,620 700 3,320
Average Annual Cost $ 114,041 $ 44,594 $ 158,635
TABLE C-6-4
INVESTMENT COST WITH ARCH DAM AT DEVIL CANYON
(in thousands of dollars)
Watana Devil Canlon Gravity Dam
Accumulated Present Worth Accumulated Present Worth
Year Expenditure Expenditure IDC Expenditure of Expenditure Expenditure IDC of IDC
1984 30,500 1,048
1985 107,000 30,500 5,775
1986 114,000 137,500 13,372
1987 159,000 251,500 22,756
1988 218,500 410,500 35,733
1989 214,000 629,000 50,600
1990 248,000 843,000 66,481
n 1991 258,000 1,091,000 83,875
I 1992 223,000 1,349,000 100,409 32,500 32,500 1,117 1,117 0'>
I 1993 161,000 1,572,000 113,609 61 ,000 61 ,000 32,500 4,331 4,331 +::> 1994 32,000 1,733,000 120,244 87,000 87,000 93,500 9,419 9,419
1995 1,765,000 1,765,000 613,902 113,000 105,731 180,500 16,294 15,246
1996 122,000 106,809 203,500 24,372 21,337
1997 148,500 121,646 415,500 33,670 27,581
1998 101,000 77 ,413 564,000 42,247 32,381
665,000 592,009 665,000 131 ,449 111,412
Watana Devil Can~on Total Watana & Devil Canyon
Construction Cost $1,765,000 $592,099 $2,357,099
I.D.C. 613,902 111,412 725,314
Investment Cost $2,378,902 $703,511 $3,082,413
Interest and Amortization $ 163,761 $ 48;429 $ 212,190
Operation, Maintenance, and
Replacement 2,620 700 3,320
Average Annual Cost $ 166,381 $ 49,129 $ 215,510
EXHIBIT C-7
CORRESPONDENCE
FEDERAL ENERGY REGULATORY COMMISSION
REGIONAL OFFICE
555 BATTERY STREET. ROOM 415
SAN FRANCISCO. CA 9411 t
Colonel George R. Robertson
District Engineer
Alaska District, Corps of Engineers
P. O. Box 7002
Anchorage, Alaska 99510
Dear Colonel Robertson:
October 31, 1978
This is in response to your letter of April 14, 1978, in which you
requested updated power values for use in your studies of the Upper
Susitna River Basin. We regret that we were not able to provide the
values earlier.
Attached Tables I through VI give details of our estimates. At
Mr. Mohnls suggestion, an annual capacity factor of 50 percent was
assumed for the Upper Susitna Basin projects.
At your request, we have provided a breakdown of our cost estimates
in order that your staff may make sensitivity analyses of the effects
of possible inflation of all components of the estimates including
fuel cost escalation. Power values are provided based on estimated
costs of power from two possible alternative thermal sources for both
the Anchorage-Kenai and Fairbanks areas. An oil-fired combined cycle
plant, located near Anchorage, and a mine-mouth coal-fired steam-
electric generating plant located near the Beluga coal fields are
considered as alternatives to hydro power for the Anchorage-Kenai area.
For the Fairbanks area, an oil-fired regenerative combustion turbine
plant near Fairbanks and a mine-mouth coal-fired steam-electric plant
are believed to be the proper alternative power sources. A combined
cycle plant alternative was not studied for Fairbanks because of its
associated "ice fogging" problems and proximity to populated centers.
Our estimates indicate that the combined-cycle plant near Anchorage
and the regenerative combustion turbine plant near Fairbanks,
respectively, are the least costly sources of power alternative to
hydroelectric. However, we are not able to state that either is the
most probable source.
As you know, there is significant speculation with respect to the
practical and economic feasibility of the development of a coal mine
-2-
in the Beluga area to serve a relatively small coal-fired steam-electric
plant. To be feasible, it is probable that the field must be developed
to provide coal for export in large quantities, or for added local use.
It is not readily apparent to us that coal will be available near term
to fuel a plant in the Beluga area. We have, nevertheless, included a
power value based on the existence of such an installation in our
estimates.
Coal is readily available in the Healy field near Fairbanks. Golden
Valley Electric Association, Inc. has contracted for a consultant's
study of the potential of installing additional coal-fired generation
to its system. Coal-fired generation, according to our estimates,
however, would be significantly more costly than that from a regenera-
tive oil-fired combustion turbine.
The National Energy Act generally prohibits the use of oil or natural
gas as fuel in large-scale base load generating plants. However, the
Act also includes many provisions under which a utility may be exempted
from the restrictions on use of oil, Exemptions may be obtained because
of unavailability of coal, high cost of coal and associated facilities,
site limitations, environmental requirements, and, most importantly,
if the required use of coal would not allow the petitioner to obtain
adequate capital for the financing of such a powerplant. Undoubtedly,
rules regarding the above will be prescribed and interpretations of
the Act will be made by proper authority. Care should be exercised in
the selection of probable alternative power sources because of these
exemption provisions. We suggest that inquiries be made of the inten-
tions of local utility officials regarding possible requests for
exemptions to the use of coal in lieu of other fuels in light of the
high investment cost of coal-fired plants.
Pursuant to one of your requests, associated investment costs of
pollution control equipment included in the total investment costs for
coal-fired plants are given below. These costs include indirects and
overheads as well as interest during construction.
(1)
(2)
Estimates of future loads are supplied the FERC on FPC Form 12E-2 by
the four principal utilities operating in Fairbanks and Anchorage.
These estimates show that in 1988 approximately 80 percent of the total
TABLE I
Annual Fixed Charge Rates
Anchorage-Kenai Market Area
Service Life, years
REA Financing
Cost of Money
Depreciation (Sinking Fund)
Insurance
Taxes
Total, Fixed Charges
Use
Municipal Financing
Cost of Money
Depreciation (Sinking Fund)
Insurance
Taxes
Total, Fixed Charges
Use
Composite -REA and Municipal 11
REA @ 75%
Municipal @ 25%
Total, Composite
Federal Financing
Cost of Money
DepreciatiQ? (Sinking Fund)
Insurance ~
Total. Fixed Charges
Use
Generating
Stations and
Substations
30
%
8.500
0.805
0.250
0.350
9.905
9.91
6.250
1.210
0.250
1.300
9.010
9.01
7.43
2.25
9.68
6.875
1.083
1.958
7.96
y Based on appro:r:imate proportion of total future
loads in Anchorage-Kenai Market Area.
~ omitted at request of NPD~ Corps of Engineers.
Steel Tower
Transmission
Lines
50
%
8.500
0.~46
0.100
0.350
9.096
9.10
6.250
0.317
0.100
1.300
7.967
7.97
6.82
1.99
8.81
6.875
0.257
7. 132
7.13
TABLE II
Annual Fixed Charge Rates
Fairbanks Market Area
Service Life, Years
Pub1ic-nonfedera1 Financing 1I
Cost of Money
Depreciation (Sinking Fund)
Insurance
Taxes
Total, Fixed Charges
Use
Federal Financing
Cost of Money
Depreciation (Sinking Fund)
Insurance Y
Total, Fixed Charges
Use
Generating
Stations and
Substations
30
%
5.750
1.322
0.250
7.322
7.32
6.875
1.083
7.958
7.96
Y Alaska Power Authority financing a8swned.
2/ Omitted at request of NPD, Corps of Engineers.
Steel Tower
Transmission
Lines
50
%
5.750
0.374
0.250
6.374
6.37
6.875
0.257
7. 132
7.13
TABLE III
Hydroelectric Plant Power Values At Market
Anchorage-Kena; Area
A. Plant Description
Capacity
Unit Size
Service Life
Heat Rate
Fuel Cost
Annual Plant Factor
B. Investment Cost
(Costs as of 7/1/78)
MW
MW
Years
Btu/kWh
¢/l06 Btu
%
$/kW
C. Annual Capacity Cost at Plant
Fixed Charges
Fuel Inventory
Fixed O&M
Administrative and General
Annual Capacity Cost at
Generator Bus
O. Energy Cost
Fuel
Variable O&M
Energy Costs at Generator Bus
Coal-fired
Generating Plant
450
225
30
10 000
110
55
Financing
Pub.-nonfed.l! Federal
1 240
120.03
0.91
14.69
5.65
141.28
11.00
1.64
12.64
1 220
$/kW-yr.
97.11
0.75
14.69
5.65
118.20
mills/kWh
11.00
1.64
12.64
TABLE III (cont'd.)
Hydroelectric Plant Power Values At Market
Anchorage-Kenai Area
(Costs as of 7/1/73)
Coal-fired Generating Plant
Fin a n c ; n 9
Pub.-nonfed. Federal ---$/kW-yr.-- -
mills/kWh
E. Cost of Thermal Plant Out2ut
at ~enerator Bus 141. 28 118.20 12.64
F. Plant to Market Thermal Plant
Transmission Costs -230 kV
l. Step-up substation
(a) Fixed charges 2.50 2.04
(b) O&M and Adm. & Gen. 0.53 0.53
2. Transmission Lines
(a) Fixed charges 10.97 8.79
(b) O&M and Adm. & Gen. 2.56 2.53
3. Receiving Station
(a) Fixed charges 1.83 1. 50
(b) O&M and Adm. & Gen. 0.39 0.39
4. Losses
~a) Capacity 11.45 9.58
b) Energy 0.65
G. Cost of Thermal Power Delivered
at Market
l. Capacity 171.51 143.56
2. Energy 13.29
H. ,Hol:dro-therma 1 Ca2aci tol: and Ener~ol:
Value ~Justments
1. Capacity 17.15 14.36
2. Energy -y
1. Value of H~dro Plant Out~ut Delivered
. at Market '
l. Capacity 188.66 157.92
2. Energy 13.29
1/ REA~ 75%; MUnicipal, 25%.
y Negligible.
TABLE IV
Hydroelectric Plant Power Values At Market
Anchorage-Kenai Area
(Costs as of 7/1/78)
A. Plant Description
Capacity
Unit Size
Service life
Heat Rate
Fuel Cost J Oil
Annual Plant Factor
B. Investment Cost
MW
MW
Years
Btu/kWh
¢fl06 Btu
%
$/kW
C. Annual Capacity Cost at Plant
Fixed Charges
Fuel Inventory
Fixed O&M 2/
Administrative and General
Annual Capacity Cost at
Generator Bus
D. Energy Cost
Fuel
O&M
Energy Costs at Generator Bus
Combined Cye1 e
Generating Plant
420
105
30
8 350
300
50
Financins
Pub.-nonfed.l! Federal
360
34.85
1. 91
3.20
39.96
$/kW ... yr.
355
28.26
1.58
3.20
33.04
millsjkWh
25.05
1.83
26.88
25.05
1.83
26.88
TABLE IV (cont'd.)
Hydroelectric Plant Power Values At Market
Anchorage-Kenai Area
(Costs as of 7/1/78)
Combined Cycle
Generating Plant
F 1 nan c i n 9
E. Cost of Thermal Plant Output
at Generator Bus
Pub.-nonfed. Federal
-$/kW-yr~-- -
39.96 33.04
mi11 s/kWh
26.88
F. Plant to Market Thermal Plant
Transmission Costs -138 kV
1. Step-up substation
(a) Fixed charges
(b) O&M and Adm. & Gen.
2. Transmission Lines
(a) Fixed charges
(b) O&M and Adm. & Gen.
3. Receiving Station
(a) Fixed charges
(b) O&M and Adm. & Gen.
4. Losses
(a) capacity
(b) Energy
G. Cost of Thermal Power Delivered
at Market
1. Capacity
2. Energy
H. Hydro-thermal Capacity and Energy
Value Adjustments
1. Capacity
2. Energy
I. Value of Hydro Plant Output Delivered
at Market
1. Capacity
2. Energy
1/ HEIt, 75%; MunicipaZ~ 25%.
2/ Included in energy cost. Y Negligible.
1.33 1.08
0.28 0.28
0.81 0.65
0.19 0.19
0.19 0.16
0.04 0.04
2.30 1.89
1.02
45.10 37.33
27.90
2.26 1.87
-'}j
47.36 39.20
27.90
TABLE V
Hydroelectric Plant Power Values At Market
Fairbanks, Alaska
A. Plant Description
Capacity
Unit Size
Service Life
Heat Rate
Fuel Cost
Annual Plant Factor
B. Investment Cost
(Costs as of 7/1/78)
MW
MW
Years
Btu/kWh
¢fl06 Btu
%
$/kW
C. Annual Capacity Cost at Plant
Fixed Charges
Fuel Inventory
Fixed O&M
Administrative and General
Annual Capacity Cost at
Generator Bus
D. Energx Cost
Fuel
Variable O&M
Energy Costs at Generator Bus
Coal-fired
Generating Plant
230
115
30
10 500
80
55
Financing
Pub.-nonfed.l/ Federal -----.,.. "'--"---'-
1 475
107.97
0.48
16.29
6.68 -
131.42
8.40
1.82
10.22
$/kW-yr.
mills/kWh
1 510
120.20
0.57
16.29
6.68
143.74
8.40
1.82
10.22
TABLE V (cont'd.)
Hydroel~ctric Plant Power Values At Market
F~irba~ks. ~laska
Costs as ~F 7 1 78 -_ .. ..---' .. _-----
Coal-fired Generating Plant
Fin a n c i n 9
Pub.-nonfed. Federal
- - -$/kW-yr. - - -mills/kWh
E. Cost of Thermal Plant Output
at Generator Bus
F. Plant to Market Thermal Plant
Transmission Costs -230 kV
1. Step-up substation
(a) Fixed charges
(b) O&M and Adm. & Gen.
2. Transmission lines
(a) Fixed charges
(b) O&M and Adm. & Gen.
3. Receiving Station
(a) Fixed charges
(b) O&M and Adm. & Gen.
4. losses
(a) Capacity
(b) Energy
G. Cost of Thermal Power Delivered
at Market
1. Capacity
2. Energy
H. Hydro-thermal Capacity and Energy
Value Adjustments
1. Capacity
2. Energy
I. Value of Hydro Plant Output Delivered
at Market
1. Capacity
2. Energy
1/ Alaska P~er Authority financing assumed.
2/ Negligible.
131.42 143.74 10.22
3.18 3.47
0.89 0.90
11.19 12.66
3.61 3.65
2.09 2.28
0.59 0.59
8.81 9.64
0.42
161.78 176.93
10.64
16.18
-2/
177 . 96
10.64
TABLE VI
Hydroe1ectric Plant Power Values At Market
Fairbanks, Alaska
A. Plant Description
Capacity
Unit Site
Service life
Heat Rate
Fue 1 Cost, Oil
Annual Plant Factor
B. Investment Cost
(Costs as of 7/1/78)
MW
MW
Years
Btu/kWh
¢/1 06 Btu
%
$/kW
C. Annual Capacity Cost at Plant
Fixed Charges
Fuel Inventory
Fixed O&M 2/
Administrative and General
Annual Capacity Cost at
Generator Bus
D. Energy Cost
Fuel
O&M
Energy Costs at Gen€rator Bus
Regen. Combustion
Turbine Plant
240
60
30
10 000
210
50
Financing
Pub.-nonfed.lI Federal
265 270
$/ HI-yr.
19.40 21,49
1.09 1.30
2.08 2.08
22.57 24.87
mills/kWh
21.00 21.00
1. 19 1.19
22.19 22.19
E.
F.
G.
H.
I.
1/
2/
ij
TABLE VI (cont'd.)
Hydroelectric Plant Power Values At Market
Fairbanks, Alaska
(Costs as of 7/1/78)
Regen. Combus!ion
Turbine Plant Fin a n c i n g
Pub.-nonfed. Federal
---$/kW-yr.-- -
mills/kWh
Cost of Thermal Plant OutEut
at Generator Bus 22.57 24.87 22.19
Plant to Market Thermal Plant
Transmission Costs -i138 kV
l. Step-up substation
(a) Fixed charges 1.60 1. 75
(b) O&M and Adm. & Gen. 0.44 0.45
2. Transmission Lines
(a) Fixed charges 1.88 2.14
(b) O&M and Adm. & Gen. 0.62 0.62
3. Receiving Station
(a) Fixed charges 0.25 0.27
(b) O&M and Adm. & Gen. 0.07 0.07
4. Losses
~a ) Capacity 1.39 1.52
b) Energy 0.81
Cost of Thermal Power Delivered
at RarKet
1. Capacity 28.82 31.69
2. Energy 23.00
Hxdro-thermal CaEacitx and
Qa1ue ~ajustments
Energy
1. Capacity 1.44 1.58
2. Energy -3/
Value of H~dro Plant OutEut Delivered
at Market
1. Capacity v 30.26 33.27
2. Energy 23.00
Alaska POwer Authority financing assumed.
IncZuded in energy cost.
NegUgihZe.
333 WEST 4th AVENUE SUITE 31 -ANCHORAGE, ALASKA 99501
Colonel George Robertson
U. S. /-\rillY Corps of [119 i neers
Alaska C'istrict
Post Office Box 7002
Anchorage, Alaska 99510
Dear Colonel Robertson:
Phone: (907) 277-7641
(907) 276-2715
Movcmber 17. 197:
1 have reviewed the material provided by tne Federal Lnergy
Regulatory Commission (FERC), associated with the Upper Susitna
study power values. 1 feel that oil-fired generation as an
alternative to Susitna hydroelectric must be questioned. Oil-fired
generation for new plants in Anchorage and Fairbanks will require
exemptions from the Secretary of Energy from the provisions of the
Powerp1ant and Industrial Fuel Use Act of 1978. The ability of
Anchorage and Fairbanks to qualify for the exemptions to meet peak
load requirements is doubtful. Due to limited refining capability
in Alaska, distillate fuel oil requirements by 1990 would require
a major expansion of refining capabilities in Alaska. Without expan-
sion the utilities will import distillate fuel and pay associated
high transportation costs. Therefore, oil-fired generation for
the rail belt area may not be acceptable either for legal and regu-
latory reasons or from the standpoint of fuel availability.
The cost of fuel for oil-fired generation is an area that is
not adequately addressed in the economic analysis of hydroelectric
alternatives by the federal government. The provision of power
values by FERC and the subsequent present worth analysis of alter-
native power generation is insensitive to National Energy Policy
and the inelastic commodity demand of non-renewable resources such
as distillate fuel. I feel that the economic analysis of the
alternatives must be sensitive to these considerations by
appraising the true costs of energy to the consumer over a fifty
year time frame with the capital intensive nature of facilities,
the economic life of facilities, and the projected cost of fuel
taken into account. The Golden Valley Electric Cooperative in
Fairbanks has recently studied the coal vs. oil-fired generation
question for the next addition to GVEA's base load capacity. GVEA
has determined that the coal fired generation alternative is pre-
ferable to oil.
Colonel George Robertson
Page Two
November 16, 1978
I hope these comments will assist the Corps of Engineers in
the application of Upper Susitna power values in the supplemental
feasibility studies currently in progress. Thank you for the
opportunity to comment.
C~ Jl
Eric P. YOU1~
Executive Director
SECTION D
FOUNDATIONS AND MATERIALS
SECTION D
FOUNDATION AND MATERIALS
TABLE OF CONTENTS
Item
SUMMARY OF CHANGES
Changes to the 1976 Interim Feasibility Report
Changes in Design
REGIONAL GEOLOGY
Physiography
Inferred Geologic History
Regional Tectonics
Seismicity
Rock and Soil Units
Rock Structure
DEVIL CANYON
Seismic Refraction Survey
Ma teri a 1 Requ'j rements
WATANA SITE
Scope of Investigations
Field Reconnaissance
Test Pits
Seismic Refraction Investigations
Instrumentation
Site Geology
Introduction
Foundation Conditions
Valley Wall Conditions
Relict Channel
Spillway
Permafrost
Ground Water
Reservoir Geology
Dam Design
Dam Foundation Treatment
Embankment Design
Powerhouse and Underground Structures
Intake Structure
Spi 11 way
Seepage Control, Relict Channel
i
Page
0-1
D-l
0-1
0-4
0-4
0-4
0-6
D-6
0-7
0-8
0-10
0-10
D-10
0-12
0-12
0-12
0-12
0-13
D-l3
0-17
0-17
0-18
D-19
0-21
0-22
D-23
1)-24
0-25
0-26
0-26
0-27
0-29
0-29
0-30
0-30
TABLE OF CONTENTS (cont)
Item
Construction Materials
Material Requirements
Sources of Materials
General
Rock Shell
Core Ma teri a 1
Filter Materials
Concrete Aggregates
Gradation Envelopes
LIST OF CHARTS
Number Title
0-1 Soils Gradation Envelope -Borrow Area E
Test Pits 1 through 5
0-2 Soils Gradation Envelope -Borrow Area 0
Test Pits 8 through 19
0-3 Gradation Envelopes -Borrow Area E
Superimposed on Fine Filter
0-4 Gradation Envelopes -Fine Filter and
Impervious Core
0-5 Gradation Envelopes -Coarse Filter and
Borrow Area E
0-6 Gradation Curve -Composite Sample No. 1
0-7 Gradation Curve -Composite Sample No. 2
0-8 Specific Gravity and Permeability Report
0-9 Compaction Test Report -Method A
0-10 Compaction Test Report -Method 0
0-11 Triaxial Compression Test Report I -Q Test,
Composite Sample No.1, 3.5% W.C.
0-12 Triaxial Compression Test Report II -Q Test,
Composite Sample No.1, 7.5% W.C.
0-13 Triaxial Compression Test Report III -Q Test,
Composite Sample No.1, 11.5% w.e.
0-14 Triaxial Compression Test Report IV -R Test,
Composite Sample No.1, 7.5% W.C.
0-15 Triaxial Compression Test Report IV -Back Pressure
and Pore Pressure Test Oata
0-16 Triaxial Compression Test Report V -R Test,
Composite Sample No.1, 3.5% W.C.
0-17 Triaxial Compression Test Report V -Back Pressure
and Pore Pressure Test Oata
ii
Page
0-31
0-31
0-31
0-31
0-31
0-33
0-34
0-35
Page
0-37
0-38
0-39
0-40
0-41
0-42
0-43
0-44
0-45
0-46
0-47
0-48
0-49
0-50
0-51
0-52
0-53
Number
0-18
0-19
0-20
0-21
0-22
0-23
0-24
0-25
0-26
0-27
0-28
0-29
Number
0-1
0-2
0-3
0-4
0-5
0-6
0-7
0-8
0-9
0-10
0-11
0-12
0-13
0-14
0-15
0-16
0-17
0-18
0-19
0-20
0-21
0-22
LIST OF CHARTS (cont)
Title
Consolidation Test Report I
Consolidation Test I -Time Curves -1, 2, 4, 8 tons
Consolidation Test I -Time Curves -16, 32 tons
Consolidation Test Report II
Consolidation Test II -Time Curves -1, 2,4,8 tons
Consolidation Test II -Time Curves -16, 32 tons
Consolidation Test Report III
Consolidation Test III -Time Curves -
1, 2, 4, 8 tons
Consolidation Test III -Time Curves -16, 32 tons
Consolidation Test Report IV
Consolidation Test IV -Time Curves -1, 2, 4,8 tons
Consolidation Test IV -Time Curves -16, 32 tons
LIST OF PLATES
Title
Devil Canyon -Site Plan and Explorations
Watana Oamsite -Exploration Plan
Watana Oamsite -Surficial Geology -West Sheet
Watana Oamsite -Surficial Geology -East Sheet
Watana Reservoir -Surficial Geology
Watana Oamsite -Stereographic Projections
Watana Oam -Section Along Oam Axis
Watana Embankment -Plan View
Watana Embankment -Section A
Watana Oamsite -Quarry Source A
Watana Damsite -Quarry Source B and Borrow Area 0
Watana Oamsite -Borrow Area E
Ground Temperature Data I
Ground Temperature Oata II
Ground Temperature Oata III
Piezometer Oata I
Piezometer Data II
Piezometer Data III
Watana Oamsite -Borrow Area E; Logs: Test
Pits 1 through 5
Watana Oamsite -Borrow Area C & 0; Logs: Test
Pits 7 through 14
Watana Oamsite -Borrow Area 0; Logs: Test
Pits 15 through 22
Watana Damsite -Borrow Area F; Logs: Test
Pits 6 and 23 through 26
iii
Page
0-54
0-55
0-56
0-57
0-58
D-59
0-60
0-61
D-62
0-63
0-64
0-65
Number
LIST OF PLATES (cant)
Titl e
0-23 Watana Damsite -Borrow Area 0; Logs: Auger
Holes 1 through 6
0-24 Watana Damsite -Borrow Area 0; Logs: Auger
Holes 6 (cont) through 9
0-25 Watana Damsite -Borrow Area D; Logs: Auger
Holes 9 (cont) through 14
0-26 Watana Damsite -Borrow Area 0; Logs: Auger
Holes 15 through 22
0-27 Watana Damsite -Borrow Area 0; Logs: Auger
Holes 23 through 24
0-28 Drill Hole Logs No.1; DH-l through DH-4
0-29 Drill Hole Logs No.2; DH-4 (cont) through DH-7
0-30 Drill Hole Logs No.3; DH-8 through DH-10
0-31 Drill Hole Logs I~o. 4; DH-10 (cont) through DH-12
0-32 Drill Hole Logs No.5; DH-12 (cont) through DR-15
0-33 Drill Hole Logs No.6; DR-16 through DR-20
0-34 Drill Hole Logs No.7; DR-20 (cont) through DH-2l
0-35 Drill Hole Logs No.8; DH-2l (cont) and DR-22
0-36 Drill Hole Logs No.9; DR-22 (cont) through DR-26
0-37 Drill Hole Logs No. 10; DR-27 and DH-28
0-38 Watana Damsite -Core Photos No.1; DH-l through DH-4
0-39 Watana Damsite -Core Photos No.2: DH-5 through DH-6
0-40 Watana Damsite -Core Photos No.3; DH-7 through DH-9
D-41 Watana Damsite -Core Photos No.4; DH-9 (cont)
through DH-ll
0-42 Watana Damsite -Core Photos No.5; DH-ll (cont)
through DH-12
0-43 Watana Oamsite -Core Photos No.6; 0 -15 through DR-20
0-44 Watana Damsite -Core Photos No.7; DH-21
0-45 Watana Damsite -Core Photos No.8; DR-22 through DH-28
iv
EXHIBITS
Number Title
0-1 location Maps and Seismic Refraction Velocity
Profiles, Watana and Devil Canyon Damsites.
By Shannon & Wilson, Inc. Geological Consultants;
Contract No. DACW85-78-C-0027, November 1978
0-2 Report -Reconnaissance of the Recent Geology of
the Proposed Oevil's Canyon and Watana Oamsites,
Susitna River, Alaska. By Kachadoorian & Henry J.
Moore, U.S. Geological Survey, November 1978
0-3 Report -Earthquake Assessment at the Susitna Project
by E.l. Krinitzsky, U.S. Army Engineer Waterways
Experimental Station, Vicksburg, Mississippi,
10 November 1978
0-4 Technical Note -Procedure for Estimating Borehole
Spacing and Thaw Water Pumping Requirements for
Artificially Thawing the Bedrock Permafrost at the
Watana Oamsite. By F.H. Sayles, U.S. Army Engineers
Cold Regions Research and Engineering laboratory,
Hanover, New Hampshire, October 1978
0-5 Open File Report 78-558-A, U.S. Geological Survey -
Reconnaissance geologic map and geochronology,
Talkeetna Mountains Quadrangle, northern part of
Anchorage Quadrangle, and southwestern portion of
Healy Quadrangle, Alaska by Csejtey, et al 1978
v
SUMMARY OF CHANGES
CHANGES TO THE 1976 INTERIM FEASIBILITY REPORT
In 1978, The Alaska District, Corps of Engineers, performed addi-
tional field explorations and geologic studies to verify the feasibility
of the Watana damsite. As a result of these studies, considerably more
information is now available concerning the site and the regional geology
of the area. Therefore, the entire sections on Regional Geology, pages
0-1 through 0-9; Watana Site, pages 0-10 through 0-12; and the paragraph
on Seismology at Devil Canyon, page 0-7, of Appendix 0, Foundations and
Materials, of the 1976 Interim Feasibility Report are deleted and replaced
by this supplemental report. No changes to the Vee Canyon and Denali
sites have been made. Plate 0-3, Watana -Site Plan and Centerline
Profile is deleted and replaced with revised drawings. Several new
plates showing geologic sections, borrow areas, and exploration logs
have been added. These are listed in the index.
CHANGES IN DESIGN
As a result of the additional field exploration and geologic studies,
a more knowledgeable assessment of the proposed project can now be made.
A summary of the items which reflect changes to the 1976 Interim Feasi-
bility Report, or reinforce the basic concepts of that report follows.
1. Nothing was found during this phase of the study to cast doubt
on the feasibility of a dam at the Watana damsite. All exploration and
geologic studies reinforced the concept that a large earth and rockfill
or a concrete gravity dam could be built in this general vicinity.
2. Detailed surveys were performed at the Watana site. It was
found that the topography used for the 1976 report was in error by
approximately 15 feet. Therefore, the elevations shown on the plates
or sections in this supplement are 15 feet lower than those shown in
the 1976 report. The detailed survey showed the valley section to be
a little wider than previously assumed and therefore, the crest length
of the dam and the total quantities within the dam are somewhat larger.
3. The explorations at the damsite indicate that the rock is as
good or better than previously assumed. Foundation rock is considered
adequate to support either an earth-rockfill structure or a concrete
gravity dam. To support this conclusion, the regional and site geology
as well as the rock structure are discussed in much greater detail in
this supplemental report.
D-l
4. The 1976 report recognized that the Watana damsite is an area
of marginal permafrost and, therefore, permanently frozen ground could
be expected in the vicinity. In the 1978 exploration program, specific
locations of permafrost were identified and a number of temperature
measuring devices were installed. The earlier assumption that perma-
frost does exist over much of this area was confirmed; however, it was
determined that this is a very "warm" permafrost, ranging from 0° C to
_1° C. Premafrost was encountered in bedrock in the left abutment of
the dam and its effects on the grouting in this area are discussed in
this supplemental report. Permafrost was also encountered in the imper-
vious borrow area; however, because of its marginal temperature, it
tends to be soft and can be easily excavated. A more detailed dis-
cussion is contained in the body of this report.
5. The 1976 report envisioned rather large amounts of gravel avail-
able for construction of the shells of the dam and limited amounts of
impervious core material. The recent explorations indicate that this
is not the case since gravels in large quantities were not verified but
large quantities of impervious core material were discovered near the
damsite. Because of the apparent shortage of gravel and an excess of
impervious material, the dam section has been completely revised. The
gravel shells have been changed to rock shells. This change to rockfill
has allowed the use of a somewhat steeper slope on the upstream face of
the dam. A large portion of the rock will come from required excavation
of the spillway. The remainder will come from excavation of underground
facilities and access roads and from a large borrow source on the left
abutment.
6. The foundation excavation has been increased to require the
entire foundation of the dam to be stripped to bedrock. The 1976 report
envisioned excavation to bedrock under the core and filters only. How-
ever, because the evidence of the limited drilling performed ;s incon-
clusive, it was considered adviseable to require removal of in situ
gravels beneath the entire embankment. If additional drilling supports
a less conservative approach, the change can be made under subsequent
feature design.
7. The core has been widened somewhat from that shown in the 1976
report and a zone of semipervious material, approximately of the same
width as the core, has been added. This was done because large amounts
of semi pervious material are available and estimates show that it can
be placed within the dam at a considerably lower cost than the rock
shell material. The total thickness of these impervious and semipervious
zones was determined by considering their effect on total stability of
the dam and the difficulties of placing materials which require careful
moisture control in the arctic environment. Laboratory tests performed
on these materials indicate that optimum moisture will be a rather criti-
cal factor in their compaction. Therefore, the use of such materials has
been held to within reasonable limitso
0-2
8. The 1976 report showed a vertical access shaft to the low-level
drain system which passed through the embankment of the dam. This has
now been changed to a tunnel through the right abutment, thereby elimin-
ating any structures in the dam embankment.
9. A grout gallery has been added to the lower portions of the dam
to facilitate grouting and to accommodate the process of thawing the
permafrost. Use of the gallery will allow embankment placement and
curtain grouting to proceed simultaneously, resulting in a shortened
construction schedule. The gallery will also provide for "read-out"
stations for instrumentation in the foundation and lower levels of the
embankment and for general access.
10. The spillway location as shown in the 1976 report has been
shifted southwest to a location which insures rock cut for its entire
length. The rock and overburden material from this large excavation
will be utilized in the dam embankment.
11. The 1976 report discusses a potential problem of seepage along
a relict channel in the right abutment. The 1978 explorations verified
the existence of this channel; however, studies indicate that it is not
a problem and, therefore, no remedial action is required.
12. The diverison tunnel portals have been shifted to ensure their
location in reasonably sound rock.
13. Professional services of Ellis Krinitzsky of the Waterways
Experiment Station and Reuben Kachadoorian and Henry J. Moore from the
U.S. Geological Survey were obtained by contract to perform seismic
studies and evaluate the earthquake risk at these sites. Their work was
divided into two phases. Kachadoorian and Moore of USGS performed the
field reconnaissance to look for active faults and other geologic hazards.
Krinitzsky's work was aimed at assessing the potential earthquakes which
could be associated with such faulting. The USGS report recognized that
this is a highly seismic region; however, the geologic reconnaissance of
the proposed Devil Canyon and Watana damsites and reservoirs did not
uncover evidence of recent or active faulting along any of the known or
inferred faults. In their work they did not uncover evidence of the
Susitna Fault, which was previously thought to exist a short distance
west of the Watana damsite. Krinitzsky's work assessed the possible
occurrance of earthquakes at the damsite and the motions that are likely
to be associated with earthqauke activity. His findings indicate that
the design of the proposed dams to withstand such activity is within the
state of the art of seismic design.
14. In the fall of 1978, the consulting firm of Shannon & Wilson
was engaged to perform refraction seismograph work at both the Watana
and Devil Canyon damsites. This work supplemented the drilling infor-
mation. The location maps and seismic velocity profiles from the Shannon
& Wilson report are included as Exhibit D-l to this appendix.
D-3
REGIONAL GEOLOGY
PHYSIOGRAPHY
The area of study is located within the Coastal Trough Province of
southcentral Alaska. The Susitna River is a glacially fed stream which
heads on the southern slopes of the Alaska Range, and flows by way of
a continuously widening valley to the tidewaters of Cook Inlet. Within
the upper 200 river miles, the Susitna passes through a variety of land
forms related to the lithology and geology of the region. From its
proglacial channel in the Alaska Range, it passes through a broad,
glaciated, intermontane valley characterized by knob and kettle topo-
graphy and by braided river channels. Turning westward along the
northern edge of the Copper River lowlands, the river enters a deep,
V-shaped valley and traverses the Talkeetna Mountains, emerging into
an outwash plain and broad valley which it follows to the sea.
Three regional topographic lows, still identifiable today, are the
Susitna River-Chulitna River area downstream of the Devil Canyon site,
the middle reach of the Susitna River from Prairie Creek to Watana
Creek, and the Oshetna River area at the Susitna Big Bend. These may
represent drainage base levels that existed during the glacial periods.
Whether they were interconnected at one time is not known since glacia-
tion has modified the original drainages. One possible interpretation
is that the ancestral Susitna River may have followed the course of the
present Watana Creek and continued southwest along an ancestral valley
through the area now occupied by Stephan Lake, Prairie Creek, and the
Talkeetna River.
The Susitna River, presently incised 500 feet into that broad,
ancestral, U-shaped valley, makes two sharp right-angle turns downstream
of Watana Creek in the Fog Creek area and leaves the ancestral valley
to flow westward into the steep, V-shaped Devil Canyon area. Glaciation
probably blocked its former southwest course forcing the river to find
a new outlet in Devil Canyon. Once established in a westward course,
the Susitna River downcut its channel rapidly and became entrenched in
Devil Canyon.
INFERRED GEOLOGIC HISTORY
The upper Susitna River basin is a complex geologic area with a
variety of sedimentary, igneous, and metamorphic rock types. These
range from Pennsylvanian to Pleistocene in age and have undergone at
least three major periods of tectonic deformation.
0-4
The oldest outcrops in the area are Pennsylvanian and Permian aged
metavolcanic flows and tuffs, locally containing limestone interbeds
that have subsequently been altered to marble. This transitional shelf
environment continued throughout the Triassic and into early Jurassic
times, with alternate deposition of basalt and thin sedimentary inter-
beds. Metavolcaniclastics include altered marine sandstones and shales.
This deposition was contemporaneous with a massive outpouring of lavas
in the eastern Alaska Range, resulting in regional subsidence.
The first major tectonic upheaval in the Susitna area occurred in
mid to late Jurassic time and consisted of large plutonic intrusions
accompanied by uplift and intense metamorphism. Erosional remnants
of these intrusives include amphibolites, greenschists, diorites, and
acidic granitic types in the upper Watana reservoir areas. This uplift,
and subsequent erosional period, was followed by marine deposition of
argillite and graywacke in late Cretaceous. These rocks are exposed
in the northwestern half of the upper Sus;tna basin and include the
phyllites of the Devil Canyon site.
The second major tectonic event occurred in middle to late Cretaceous.
Most of the structural features in the Talkeetna Mountains, including
thrust faulting, complex folding, and uplift, occurred at that time.
As a result of the thrust faulting, Pennsylvanian and Permian volcanic
flows and tuffs were thrust over the much younger late Cretaceous
argillite and graywacke.
In early Tertiary, approximately 65 million years ago, the north-
western portion of the upper Susitna basin was intruded by plutons of
igneous rock. The diorite pluton that underlies the Watana site is
one of these intrusives. Deposition of undifferentiated volcanic flows,
pyroclastics, and associated near-surface intrusives occurred concurrent
with and following the intrusion of the plutons.
The third major tectonic event was a period of extensive uplift and
erosion in middle Tertiary to Quaternary. Uplift of 3,000 feet has been
measured in the southern Talkeetna Mountains. The widespread erosion
that occurred during this period removed thick rock sequences from the
Susitna basin area.
Glaciation has been the prime erosion agent during the past several
million years. At least two, and probably more, periods of glaciation
occurred within the upper Susitna basin area. The central and eastern
portions of the area may have been partially covered by glacial lakes
during the latter glaciations. Renewed uplift in late Pleistocene
rejuvenated the erosion cycle until the streams, with their increased
0-5
gradients, became incised within glaciated valleys. The area currently
is undergoing continued stream erosion, and is covered in many areas
with a veneer of glacial and alluvial clay, silt, sand, and gravel
deposits.
REGIONAL TECTONICS
The arcuate structure of southcentral Alaska reflect both the magni-
tude and direction of regional tectonic forces caused by the collision
of the North American and Pacific Plates. The Talkeetna Mountains and
adjacent Susitna River basin are believed to have been thrust north-
westward onto the North American Plate from their parent continental
blocks. It was this thrusting action which caused most of the struc-
tural features now seen in the upper Susitna basin.
Two major tectonic features bracket the basin area. The Denali
Fault, about 43 miles north of the damsites and active during the
Holocene, is one of the better known Alaskan faults. A second frac-
ture, the Castle Mountain Fault, is 75 miles south of the river basin.
The Susitna basin is roughly subdivided by the northeast-southwest
trending Talkeetna Thrust, which roughly parallels the location of the
Susitna Fault, as referred to in the 1976 Interim Feasibility Report.
The Talkeetna River is a surface expression of the southern portion of
both structures; however, Kachadoorian and Moore were unable to locate
evidence of faulting in the Tsusena Creek area and, therefore, expressed
doubt that the Susitna Fault exists. They found evidence of movement
in the Talkeetna River and Watana Creek valleys and postulated that
the Talkeetna Thrust could be a projection of this feature. Such a
projection passes about 4 miles to the south of Watana damsite. The
major alpine orogeny which formed many of the basins' present northeast-
southwest trending compressional structures occurred in conjunction
with the Talkeetna Thrust in late Cretaceous. Another contemporary
zone of intense shearing, roughly parallel to the Talkeetna Thrust, is
located about 15 miles east of the Talkeetna Thrust.
Two poorly exposed normal faults of probable Cenozoic age have
been projected from gravimetric data as occurring in the Chulitna River
valley about 15 miles northwest of the proposed Devil Canyon damsite.
These faults have the northeast-southwest trend typical of the major
structures within the area. No faults with recent movement have been
observed within the upper Susitna River basin.
SEISMICITY
A seismological assessment of the basin area was prepared by
Dr. E.L. Krinitzsky of the U.S. Army Engineer Waterways Experiment
Station in the summer of 1978, under contract with the Alaska District,
0-6
Corps of Engineers. Field reconnaissance to look for active faults and
other geological hazards was conducted by U.S. Geological Survey under
the direction of Reuben Kachadoorian and Henry J. Moore. These reports
are included as Exhibits D-3 and D-2 in this appendix. They recognize
that the Devil Canyon and Watana damsites are in a region of high seis-
micity and major faults. However, the geologic reconnaissance of the
proposed Devil Canyon and Watana damsites and reservoir areas by the
USGS experts did not uncover evidence of recent or active faulting along
any of the known or inferred faults. The tectonic framework of the
region is not well understood because of the lack of local seismic moni-
toring stations. Present knowledge indicates that historical earthquakes
in the area often have hypocenter depths in excess of 50 km. Such events
are associated with movement along the Benioff zone and often are not
directly associated with local surface faulting. The Denali Fault in
the Alaska Range, approximately 43 miles to the north, is the dominant
surface feature in this area. The Susitna Fault, previously thought
to exist west of the Watana damsite, was not confirmed in recent geologic
mapping by the USGS team, nor did they find any evidence of faulting
in the river channel at either of the damsites. The results of the
core drilling and geologic reconnaissance at the damsite are strong
evidence that no major faulting exists under the Watana damsite. The
lack of significant shearing in DH-21, the 600-foot cross river hole,
reinforces this conclusion.
Krinitzsky's work assessed the possible occurrence of earthquake
activity based on the USGS field work. He assumes an earthquake of
magnitude 8 along the Denali Fault, however, these motions are not
critical when attenuated to the damsites. To account for the possibility
that a major active fault could exist near the damsites, Krinitzsky has
assigned a "floating" earthquake of magnitude 7 which could occur in
the near vicinity of the dam. This generates the most severe design
motions. The rational for the "floating" earthquake and a table of
associated motions is included in his report (Exhibit D-3). This
criteria is within the state of the art for earthquake design for large
dams, and therefore. should not preclude proceeding with detailed
design of the projects •.
ROCK AND SOIL UNITS
The proposed Watana damsite and reservoir area ;s underlain by a
complex series of metamorphic, igneous, and sedimentary rock. Specific
formation names have not been applied to most of these units and they
are instead assigned lithologic descriptions for correlation and mapping
purposes. The distribution of various rock units that underlie the
proposed reservoir are shown on Plate 5. Following is a brief descrip-
tion of the various rock units, beginning at the upper end of the res-
ervoir and proceeding downstream to the damsite. Additional informa-
tion and descriptive details concerning the rock units are included
in the U.S. Geological Survey's Open File Report 78-558-A, Reconnais-
sance Geologic Map and Geochronology, Talkeetna Mountains Quadrangle,
D-7
The upper reaches of the reservoir are underlain by an amphibolite
unit. These are metamorphic rocks including greenschists, diorites,
and local marble interbeds. Directly downstream of this unit is a
zone of granitic types that are exposed north of the river at elevations
above the proposed reservoir level.
The oldest rocks exposed within the area are farther downstream
within the middle reservoir reaches and include both volcanics and lime-
stone units. The volcanics consist mostly of metamorphosed basalt
and andesite flows and tuffs that outcrop in the vicinity of Jay Creek
and downstream from Kosina Creek. The limestone unit consists of marble
interbeds that occur locally within the volcanics. The volcanics are
overlain farther downstream by a volcanic unit of younger age consisting
of a series of metamorphosed basaltic flows with interbeds of chert,
argillite, and marble. This unit is exposed both near the mouth of
Watana Creek and on the higher slopes west of Watana Creek. A much
younger series of interbedded conglomerates, sandstones, and claystones
is exposed along the lower reaches of Watana Creek directly upstream
from its mouth.
The downstream reaches of the reservoir area are underlain by a
sequence of argillites and graywackes. Exposed within the immediate
damsite area is a granitic body intruded into these metasediments. It
consists primarily of diorite with upstream and downstream margins that
include associated schist, gneiss, and composite igneous and metamorphic
rock types. Andesite flows and dikes are associated with this diorite
pluton.
Other granitic intrusives occur east of the reservoir area. locally,
these intrusives are overlain by a series of younger igneous flows and
tuffs and related shallow intrusives.
Overburden units in the proposed reservoir area include deposits of
glacial till and drift with associated outwash and lake sediments,
colluvium including slopewash and talUS, alluvium and local slide debris.
ROCK STRUCTURE
Rocks within the reservoir area have undergone a complex deforma-
tion sequence, including uplift, intrusion, thrust faulting, folding,
shearing, and associated metamorphism. The most significant structural
feature within the reservoir area is the Talkeetna Thrust which strikes
northeastward across the lower reservoir area and is roughly parallel
D-8
to the lower reaches of Watana Creek. The Talkeetna Thrust, within the
Watana reservoir area, has displaced the volcanic unit over the much
younger metasediments.
A northeast striking shear zone that dips steeply southeasterly,
and is roughly parallel to the Talkeetna Thrust, crosses the reservoir
area about 15 miles east of the Talkeetna Thrust near Kosina Creek.
Whether this shear zone represents a significant feature is not known.
The most significant rock structure in the immediate dam area is
the intrusive diorite pluton of Tertiary age. It is observable for
4 miles parallel to the river and 2 miles north and south and is prob-
ably of great depth. Upstream and downstream border zones developed
with several different metamorphic and igneous rock varieties. Two
distinct northwest trending shear zones have been mapped in the vicinity
of the damsite. One is 3,400 feet upstream and the other 2,500 feet
downstream from the proposed dam axis. Attitudes vary with strikes
ranging from N 40 0 W to 60 0 Wand dips from 70 0 to 90 0 either SW or NE.
The two shears can be seen in the right valley wall, but not on the left
valley wall. The left wall is obscured by a slide block at the upstream
shear, and the left wall at the downstream shear has a rock face that
parallels the shear direction making observations difficult. The up-
stream shear zone has been named "The Fins," and has an observable
width in excess of 400 feet. It includes seven near vertical rock fins
averaging 5 to 25 feet in width bounded on both sides by altered and
crushed' rock. The downstream shear zone, named lIF;nger Buster", is some-
what less distinct and is partially covered by slope debris. It has an
estimated width of 300 feet. Another northwest trending shear zone,
similar to the two shears mentioned above, occurs downstream from the
damsite in the vicinity of Tsusena Creek.
Fracture patterns including both joints and local shears have been
mapped within accessible areas 'in the vicinity of the damsite. Details
of this mapping are shown on Plates 0-3 and 0-4. Fractures include both
cooling type jointing and structural deformation jointing resulting from
the regional tectonic forces of uplift and thrust faulting. Shear,
tension, and relief joints resulting from unloading by erosion of over-
lying sediments and/or melting of glacial ice are all present within
the damsite area. A joint diagram plotted on an equal area stereographic
projection is shown in Figure 0-6. The dominant fracture orientation
;s to the northwest, but fractures strike in several directions. The
major joint sets are N 50° Wand the minor joint sets are N 30 0 E as
observed within the area.
D-9
DEVIL CANYON
SEISMIC REFRACTION SURVEY
During September 1978, seismic refraction surveys were undertaken
at Watana and Devil Canyon damsites by Shannon and Wilson, geotechnical
consultants. At Devil Canyon, the seismic survey consisted of three
lines, each approximately 1,100 feet long. One of these lines was
located near the proposed ali.nement of the saddle dam on the left abut-
ment and the remaining two lines were located near an abandoned airstrip
on the alluvial fan at the confluence of Cheechako Creek and the Susitna
River (see Plate 0-1). The seismic line near the centerline of the left
abutment saddle dam was alined to expand information derived from drilling
accomplished on this site by the U.S. Bureau of Reclamation (USBR) in
1957. The refraction profile correlated well with the top of rock from
the drilling data (see Sheet No. 10, Exhibit 0-1). A lower velocity
zone of rock sandwiched between competent phyllite indicates the possi-
bility of a shear zone at the low point of the saddle. This correlates
with hole DH-6 which indicated shearing in the 20 feet of bedrock pene-
trated by the boring.
The seismic lines on the Cheechako Creek aggregate deposit were
alined to establish the depth to bedrock beneath these deposits and
thereby confirm the quantity of material available for borrow. The
velocities for the material in the alluvium indicate that the area is
composed of a layer of sands and gravels or glacial materials several
hundred feet thick overlying bedrock. This confirms the existence of
material well in excess of the requirements for the project.
The location map and seismic velocity profiles from the Shannon &
Wilson report and included in Exhibit 0-1 to this appendix.
MATERIAL REQUIREMENTS
Co,crete Requirements
Material requirements for Devil Canyon dam are based on a concrete
gravity dam. Under this proposal approximately 2.6 million cubic yards
of concrete will be required, most of which will be masi concrete. The
remainder will be structural concrete for the appurtenant structures
to the dam, including the powerplant. With stockpile losses, this
amount of concrete wi 11 requ; re approximately 3 mi 11 ion cub; c yards
of processed aggregate.
The USBR located an extensive deposit of material which will yield
concrete aggregate of adequate quality in an alluvial fan approximately
1,000 feet upstream of the proposed dam axis. The fan was formed at
the confluence of Cheechako Creek and the Susitna River.
0-10
Thirteen test pits and trenches were dug in the fan area by Bureau
of Reclamation personnel in 1957. About 1,300 pounds of minus 3-inch
material was tested by the USBR for basic aggregate suitability studies.
An additional 200 pounds of material was collected by Corps of Engineers
personnel in 1975 from the existing Bureau test pits and the riverbank.
This material was tested by the North Pacific Division Materials Labora-
tory in 1978 .
If the excavation of materials is confined to that part of the
alluvium located above river level (elevation 910 to 920 feet) with
conservative back slopes through the ridges and benches, approximately
6,000,000 cubic yards of material is available in this location with
all the resulting excavation in the reservoir area. Seismic refraction
surveys indicate that usable gravel exists to approximately elevation
870 feet, so additional material could be retrieved if needed by bailing
from below the water surface. Placement of the coffer dam, sizing of
the diversion tunnel, and the ability to control the flow in the river
at Watana dam will ultimately affect the method of exploitation of this
source.
The locations of the test pits are shown on Plate D-l and the
~etailed logs can be found in the U.S. Bureau of Reclamation's Alaska
Geologic Report #7, Devil Canyon Project, dated March 1960. Laboratory
investigations of the aggregate samples were reported in USBR Report
#C-932 by their Concrete Laboratory Branch, dated 21 December 1959.
Petrographic analyses of the fine (sand sized) particles and coarse
(gravel size) particles indicate that the sands and gravels in the fan
are composed of quartz diorites, diorites, granites, andesites, dacites,
metavolcanic rocks, aplites, breccias, schists, phyllites, argillites,
and amphibolites. The gravel particles are stream worn and generally
rounded in shape. The sand grains vary from nearly rounded to sharply
angular in shape, averaging subangular. The specific gravity (BSSD) of
the material ranges from 2.68 to 2.80.
Results from both labs indicate that the materiai in the Cheechako
Creek fan is of adequate quality for use as concrete aggregate.
Embankment Material Reguirements
The saddle dam on the left abutment, associated with the concrete
gravity dam, will require approximately 835,000 cubic yards of material.
These materials will be obtained from the same sources as discussed in
the Interim Feasibility Report.
D-ll
WATANA SITE
SCOPE OF INVESTIGATIONS
Field Reconnaissance
Geologic reconnaissance and mapping of the reservoir area and dam-
site were conducted concurrently with subsurface investigations through-
out the spring and early summer of 1978. The work of the geologic teams
was made easier in the early spring as rock outcrops were not obscured
by the leaves on the trees and the dense ground foliage. Through the
months of March and April, geologic mapping of the lower canyon was done
from the frozen surface of the river, which allowed access to areas
otherwise inaccessible after the ice had melted and high summer flows on
the river had begun. Within the damsite area the primary purpose was to
find, identify, 'and trace the surface expressions of discontinuities and
shear zones as an aid in directing the drilling program and to provide
preliminary geologic mapping of the site. Within the reservoir area~
the primary thrust of the reconnaissance was toward identification of
slopes, which by reason of shape, structure or overburden mantle could
develop minor slumps and slides as a result of permafrost degradation
or seismic action.
Borings and Test Pits
Ouring 1978, explorations were conducted in the dam foundation and
relict channel area. Core borings in the valley walls and floor were
used to explore the quality and structure of the foundation rock and to
obtain representative samples for testing. Borings in the relict channel
area were used to define the depth of overburden, the extent of perma-
frost, the location of the water table and to examine, by drilling and
sampling, the nature and condition of the materials.
Shallow auger holes were also used to determine the extent of deposits
in the borrow areas and to verify the existence of quantities necessary
for embankment construction. .
Locations of explorations are shown on Plate 0-2. Logs are shown
on Plates 0-19 through 0-37; and core photos are shown on Plates 0-38
through 0-45.
Test pits were dug in potential borrow areas utilizing tractor-
mounted backhoes. Bulk sack samples were retrieved from each test
pit for testing later at the North Pacific Oivison Materials Labora-
tory in Troutdale, Oregon.
0-12
A total of 27 test pits were dug in four areas as follows:
1. The mouth of Tsusena Creek (Borrow Area lEI) -6 test pits.
2. The glacial till borrow area (Borrow Area 10 1) -14 test pits.
3. Upper Tsusena Creek, north of Tsusena Butte, (Borrow Area IC I
) -
test pit.
4. Middle Tsusena Creek -6 test pits.
The locations of Test Pits 1 through 5 and 8 through 21 are shown
on Plates 0-12 and 0-11. The remainder of the test pits are located
in areas which are not presently considered as borrow areas; however,
they may be located on Plate 0-2. The logs of all the test pits are
shown on the appropriate borrow area Plates 0-19 through 0-22.
Seismic Refraction Surveys
A seismic refraction exploration program consisting of 22,500
lineal feet of seismic refraction lines was completed by Dames and \Vloore,
Consultants, in 1975. Results of those investigations were presented
as Exhibit 0-1, Section 0, Foundation and Materials, in the 1976 Interim
Feasibility Report. In the fall of 1978, an additional seismic refrac-
tion survey was completed by Shannon and Wilson, Consultants, which
includes 47,665 feet of seismic refraction lines. Locations of these
additional seismic explorations are shown on Plate 0-2, and the location
map and seismic velocity profiles are presented as Exhibit D-l. The
survey confirmed the findings of the Dames and Moore study. It confirmed
the existence of a buried channel in the relict channel area and in
general supported conclusions relating to shear zones in the abutments
as interpreted from the recent core borings and geologic reconnaissance.
The Shannon and Wilson survey also confirmed the existence of large
quantities of borrow materials on Tsusena Creek in the proposed borrow
area.
Instrumentation
Instrumentation conducted under this phase of the project consisted
of the installation and data reading of ground water measurement
devices, temperature logging devices, and the recording of the ambient
temperature.
Ground Water: All piezometers installed were of the open well point
type and were filled with diesel oil where they extend through permafrost
zones to prevent freezing. A total of 10 piezometers were installed at
the following locations.
0-13
TABLE D-l
Surface Tip
Location Elevation Elevation Date Set Size
DR-14 2,340 2,271. 0 26 Apr 411
2,340 2,295.2 19 Aug 1-1/211
DR-20 2,207 2,123.8 30 May 1-1/211
DR-18 2,172 2,107.0 21 Jun 1-1/2"
DR-17 2,167 2,136.3 8 Jun 1-1/2"
DR-16 2,099 2,05308 5 Jun 1-1/2"
AP-1 2,202 2,188.6 20 Jun 1-1/2"
AP-2 2,200 2,189.0 20 Jun 1-1/2"
DR-19 2,151 2,109.0 3 Ju1 1-1/2"
DR-22 2,229 2,005.5 3 Aug 1-1/211
DR-26 2,295 2,229.5 11 Aug 1-1/2"
All locations are shown on Plate D-2 and Plate D-ll. Plotted data
is shown on Plates D-16 through D-18.
Subsurface Temperature: The principal temperature logging device
consisted of a 3/4-inch galvanized pipe, with the lower end capped and.
sealed. The pipe was filled with a mixture of ethylene glycol and water
(50/50) or arctic grade diesel fuel. Readings were taken using a digital
volt-ohm meter and a single thermister which was lowered into the pipe.
At location DR-26 both a 3/4-inch galvanized and a 1-l/2-inch PVC
pipe were installed to determine if readings could be duplicated in a
pipe of larger diameter. A total of 14 devices were installed at the
locations shown in Table D-20
D-14
TABLE D-2
Date Buried
Location Ins ta 11 ed Length Stick UE DeEth Fl d
AP-8 23 Jun 64 1 4.2' 58.9' Diesel
AP-9 23 Jun 211 3.21 17.8' Diesel
DH-12 3 Jul 129' 1.8' 127.2' Diesel
DH-23 17 Ju 1 76' 0.5' 75.5' Antifreeze
DH-24 1 Aug 86 1 1.21 84.8' Antifreeze
DR-18 21 Jun 25,. 3.4' 247.6' Diesel
DR-19 3 Jul 83' 3.9' 79. l' Diesel
DR-22 3 Aug 492' 2.0' 490.0' Antifreeze
DH-28 30 Aug 124' 1.0' 123.0' Antifreeze
DR-26
(3/4" pipe) 11 Aug 68' 3.8' 64.2' Antifreeze
DR-26
(1-1/2" pipe) 11 Aug 99' 3.4' 95.6' Antifreeze
DR-14 19 Aug 65' 2.8' 62.21 Antifreeze
DH-21 23 Aug 160' 2.0' 158.0' Antifreeze
DH-25 15 Aug 80' 4.0' 76.0' Antifreeze
All locations are shown on Plate D-2 and Plate D-ll. The plotted
temperature data can be found on Plates D-13 through D-15.
A second type of temperature logging device, installed at DR-22,
consisted of a multipoint thermistor string. The purpose of this instal-
lation was to act as a check against the 3/4-inch fluid filled devices
described above.
Ambient Temperature: The ambient temperature was obtained using
a standard high-low Mercury thermometer placed in the shade on the
right abutment riverbank approximately 4 feet above the ground. Prior
to this phase of the project, there was no ambient temperature data
available for this section of Alaska. Data obtained is shown on Table
D-3.
D-15
TABLE 0-3
Date High of Low of Date High of Low of ---
23 Mar 78 22 0 23 t~ay 78 60 39
24 Mar 78 24 13 24 May 78 60 32
25 Mar 78 28 19 25 May 78 61 40
27 ~~ar 78 32 10 26 May 78 41 36
28 Mar 78 26 13 27 May 78 64
29 Mar 78 40 6 28 May 78 36
30 Mar 78 35 6 29 May 78 58 33
31 Mar 78 36 5 30 May 78 63 36
1 Apr 78 31 5 31 May 78 66 40
2 Apr 78 28 -4 1 Jun 78 54 36
3 Apr 78 28 3 2 Jun 78 58 38
4 Apr 78 36 4 3 Jun 78 68 41
5 Apr 78 36 20 4 Jun 78 68 38
6 Apr 78 33 11 5 Jun 78 57 39
7-8 Apr 78 40 28 6 Jun 78 66 44
9 Apr 78 41 10 11 Jun 78 72 44
10 Apr 78 43 13 12 Jun 78 62 39
11 Apr 78 38 20 14 Jun 78 57 40
12 Apr 78 38 15 16 Jun 78 58 34
13 Apr 78 40 30 19 Jun 78 52 33
14 Apr 78 44 32 20 Jun 78 61 33
15 Apr 78 40 38 21 Jun 78 63
16 Apr 78 39 29 22 Jun 78 46
17 Apr 78 38 21 27 Jun 78 55 38
18 Apr 78 43 21 28 Jun 78 59 37
19 Apr 78 44 20 30 Jun 78 62 43
20 Apr 78 48 24 1 Ju1 78 57 41
21 Apr 78 44 25 2 Ju1 78 62 43
22 Apr 78 45 30 4 Ju1 78 70 47
23-24 Apr 78 47 32 7 Jul 78 62 40
25-26 Apr 78 50 26 8 Ju1 78 73 43
30 Apr 78 59 32 9 Ju1 78 70 49
1 May 78 60 34 10 Ju1 78 66 42
9 May 78 64 30 11 Ju1 78 71
10 May 78 72 33 12 Ju1 78 50
11 ~1ay 78 70 33 14 Ju1 78 59 50
12 May 78 65 40 16 Ju1 78 58 47
13 May 78 72 30 26 Ju1 78 66 45
14 ~1ay 78 72 31 27 Ju1 78 78 40
15 May 78 66 36 28 Ju1 78 74 55
16 May 78 55 32 29 Ju1 78 78 39
17 May 78 60 30 30 Ju1 78 82 46
18 May 78 64 37 31 Ju1 78 84 52
19 May 78 60 37 1 Aug 78 80 58
20 May 78 75 24 9 Aug 78 71 46
21 ~~ay 78 70 43 10 Aug 78 68 54
22 May 78 36 11 Aug 78 66 49
0-16
Accuracy of Subsurface Temperature Data: Resistance measurements
were obtained using a Keithley volt-ohm meter, which allowed readings
to the nearest ohm. With a span of 225 ohms per degree centigrade, 1
ohm represents 0.005 0 C. The temperature data in this report has been
reported to 0.010 C and is reliable to that degree of accuracy. To
verify the accuracy of each thermister, its resistance was measured in
an ice bath. It was found that the thermistors are very stable and do
not tend to drift from their original resistance at 0.00 0 C.
General Comments
The drilling in the permafrost was performed with core drills and
rotary drills, which introduce a large amount of heat into the ground.
Where the penllafrost temperature is only slightly below the freezing
point, this tends to melt the permafrost and makes identification very
difficult. Therefore, the drilling operation mayor may not reflect
the existence of permafrost, and it is necessary to rely heavily on the
instrumentation for a true evaluation of the location and depth, at which
permafrost exists. By December of 1978, the temperature logging devices
may not have stabilized due primarily to the fact that the drilling
method used was rotary with drilling "mud" as the circulation medium,
which tends to thaw the permafrost. Upon inspection of the plotted
data for the locations in this area it can be seen that the temperatures
are gradually approaching the 00 C point. Through a cont"inual program
of monitoring these points, a great deal can be learned about IIfreeze
back."
At location DR-26, 3/4 inch and 1-1/2 inch pipes were installed to
determine if convection currents in the pipe would affect the accuracy
of the near surface readings. It can be seen from the temperature
plots, shown on Plates D-13 through D-15, that there is a degree of
convection in the upper zones, while with depth the two readings are
very similar. At location DR-22, the string had 14 thermistors in a
150 foot length. The data obtained from this string has not been
included in this report since its reliability is in question. This is
due to damage received during installation as well as the fact that the
thermistors are of a lower quality and adequate calibration could not
be obtained prior to installation. At location DH-12 the 3/4-inch pipe
temperature logging device was lost when it was decided that the bore-
hole camera should be run in this boring. At location DH-25 no data
is available because the 3/4-inch pipe froze up during installation.
5 ITE GEOLOGY
Introduction
The river valley at the site has a V-shaped lower or bottom canyon
deeply incised into an upper, much broader, U-shaped river valley of
considerable extent and width.
D-17
The lower ri ver valley fl oor ranges from 300 to 600 feet wi de and
has side slopes of 35 to 60 degrees with locally scattered rock outcrops
that rise in near vertical cliffs. The incised portion of the canyon
extends from subriver level upward about 500 feet to approximate eleva-
tion 2,000 feet, where it ranges in width from 1,500 to 3,000 feet.
Above elevation 2,000 feet, there is a distinct flattening of the valley
slopes and the area broadens out into a very wide fonner river valley.
Width of this former valley base level is from 8 to 10 miles in the
lower reservoir area, narrows to about 1 mile in the midreservoir area
upstream of Jay Creek and widens to more than 20 miles in the upper
reaches of the reservoir.
Foundation Conditions
The site was mapped and explored with 17 core holes, 12 of which
are on the dam axis shown in this report. Six of the holes are angle
holes, five were drilled normal to the dominant structural trend, and
one drilled across the river valley. The exploration plan with hole
locations is presented on Plate D-2.
The river valley is filled with alluvium consisting of gravels,
cobbles, and boulders in a matrix of sand or silty sand. Overburden
depths in the valley bottom range from 40 to 80 feet and may exceed 100
feet in places. Overburden depths on the valley slopes range up to 10
feet deep on the left abutment and up to 20 feet on the right abutment.
However, overburden upstream of the left abutment is more than 56 feet
deep.
Overburden on the valley slopes is mostly glacial debris and talus
consisting of various gravel and sand mixtures and some silts, with
cobbles and small boulders. The underlying rock is diorite, grano-
diorite, and quartz diorite with local andesite porphyry dikes and more
widely scattered minor felsite dikes. Most of the rock, although frac-
tured, is relatively fresh and hard to very hard within 5 to 40 feet
of top of rock. Overburden and rock stripping depths along the dam
axis are shown in cross section on Plate D-7.
Fractures are closely to moderately spaced at the bedrock surface,
generally becoming more widely spaced with depth. Fracture zones found
at all depths tend to be tight or recemented with calcite or silica.
The northwest trending joints and high angle shears mapped in the rock
outcrops are found at different depths within most drill holes and
range from single fractures to broken zones more than 20 feet thick.
Broken rock within the shear zones is locally decomposed but consists
mainly of moderately hard to very hard fragments. Many fractures have
thin clay gouge seams and slicken sides. Pyrite and chlorite minerali-
zation is found as coatings on many fracture surfaces. Shears are
D-18
spaced from a few feet to more than 100 feet apart, and since the shears
are mostly vertical, greater lengths of sheared material were recovered
in vertical drill holes. In addition to the shears, primary and rehealed
breccia zones occur in some areas adjacent to the andesite porphyry dikes.
Most of these rehealed breccias are relatively competent rock, but a
primary breccia zone downstream of the axis on the left abutment includes
locally decomposed materials.
Valley Conditions
The river valley bottom was explored with six core drill holes.
Three holes are on the axis and three are about 1,000 feet downstream
of centerline in the toe area. River alluvium varied in depth from 44
to 78 feet. This alluvium consists of gravels, cobbles, and boulders
imbedded in sands with local gravelly or silty sand lenses. The gravels
and larger sizes are mostly subrounded to rounded with occasional large
boulders. Most large sizes are of dioritic composition, but metamorphic
and other rock types were also noted. Most of the gravels are fresh,
but a few are coated with plastic fines. Alluvial materials in some
areas were frozen to depths in excess of 50 feet and possibly all the
way to bedrock at the time of drilling.
The bedrock is a diorite that in most holes is very closely fractured
in the upper 10 to 20 feet. Fractures become more widely spaced with
depth; however, local zones of closely spaced fractures occur throughout.
Joints are both open and rehealed or cemented with calcite and silica.
The rock below river level is mostly fresh and hard to very hard. Shear
zones occur in several of the holes and include some thin clay gouge
coatings and slickensides. Soft chloritic materials were also encountered
in one shear zone, and iron staining with pyrite mineralization is common.
It should be noted that DH-2l was drilled essentially across the river
from the left to the right abutment. No major fault or significant
change in materials was seen although six minor shear zones were
encountered in the hole. Most of these zones are less than 3 feet thick,
whereas, some of the vertical holes penetrated sheared material for
distances of more than 10 feet. This confirms the near vertical nature
of most shearing. Geologic mapping in rock exposures along the river-
bank also indicates the near vertical nature of shearing. An andesite
porphyry dike was penetrated at depth by OH-21. This dike has an
apparent thickness of about 13 feet, and the contacts with the diorite
are tight and contain no notable planes of weakness.
The left abutment was explored with five drill holes, three on the
dam axis and one each upstream and downstream of the embankment. Over-
burden depths in the downstream hole and the three axis holes are less
than 10 feet. This overburden consists of small subangular to sub-
rounded boulders in silt, sand, and gravel. Overburden in OH-28, located
approximately 1,000 feet downstream of the axis at elevation 1,971 feet,
0-19
consists of 6 feet of silty clay overlaying 2 feet of sand. DH-25,
located about 750 feet upstream of the axis at elevation 2.045 feet,
penetrated a vertical depth of 56 feet of glacial and alluvial deposits
and had not yet encountered rock when it was abandoned. Overburden in
DH-25 consists primarily of gravelly, silty sand with boulders to a
depth of 15 feet, underlain by gravelly, clayey silt. Gravels are sub-
rounded to rounded and the clayey silts are stiff and plastic.
Rock in the three axis holes is a hard quartz diorite, whereas in
DH-28 downstream of the embankment, it is an andesite porphyry. The
relationship between the quartz diorite as a plutontic rock and the
andesite porphyry as a surface flow rock is not clearly understood.
This contact area between the two type rocks is in the location of the
underground powerhouse and wi 11 be closely explored during des i gn ; nves-
tigations. It is assumed the underground powerhouse will be located in
the dioritic rock. Weathering is primarily staining on fracture surfaces.
Fracture spacings vary from very close to moderately spaced; spacing
increases with depth.
Fractured zones, encountered in all holes, are from less than 1 to
more than 20 feet thick and are separated by from 10 to more than 50
feet of relatively undisturbed rock. Many fractures include thin seams
of clay gouge, slickensides, secondary pyrite, and breccia. DH-28,
downstream of the embankment. appears to have been drilled in an andesite
porphyry breccia contact zone adjacent to the diorite pluton. Much of
the core is brecciated, moderately weathered to highly altered, and
recovered in small fragments. Several zones of clay gouge were noted.
Right abutment conditions were explored with six core drill holes
along the proposed dam axis. Three of these holes were angle holes
drilled normal to the dominant structural trends. Overburden depths
within the six holes range from 4 to 20 feet, with the greater depths
in the holes farthest upslope. Overburden consists of gravelly sand
with cobbles and small boulders.
Bedrock is moderately hard, but weathered, closely fractured and
locally sheared in the upper 10 to 40 feet. The rock is diorite or
quartz diorite with zones of quartz diorite breccia. The quartz diorite
breccia is healed, probably formed during emplacement, and is not con-
sidered a zone of weakness.
Fractured zones encountered during drilling are similar to those
noted on the left abutment. Shears range up to 22 feet thick and are
separated from each other by about 10 to 100 feet of competent rock.
Very thin films of clay gouge and slickensides occur on some fracture
surfaces. Iron staining occurs on many fracture surfaces and fine dis-
seminated pyrite mineralization occurs more widely.
D-20
Relict Channel Area
The relict channel is a suspected ancestoral Susitna River channel
north of the right abutment under the broad terrace area between Deadman
and Tsusena Creeks. Ground surfaces within the Relict Channel area are
between elevation 2,100 and 2,300 feet along low elongated ridges and
shallow depressions. This area was originally explored with two seismic
lines and the results presented in the Feasibility Report, Appendix 1
as Exhibit 0-1. Subsequent 1978 explorations include 1,814 linear feet
of drilling, borrow explorations near Deadman Creek and 23,600 feet of
seismic refraction lines. The 11 drill holes range from 21 to 494 feet
in depth and were mostly noncore rotary holes supplemented with drive
samples and some bedrock coring. The results of these 1978 explorations
confirm the existence of the deeply buried bedrock surface depression
discovered during the 1975 seismic investigations. The lowest bedrock
elevation encountered in drilling was in DR-22 at 1,775 feet, MSL or
454 feet below ground surface.
Overburden consists of both glacial and alluvial materials occurring
in varying sequences that are difficult to correlate with the limited
drilling to date.
Outwash occurs over much of the area, consisting of gravelly,
silty sands or silty, gravelly sands in varying proportions, with some
local cobbles and boulders and more widely scattered clay lenses.
These materials are mostly loose and the fines are predominantly non-
plastic.
Glacial till is the most abundant overburden material found within
the relict channel area. These tills occur in three separate sequences
in the deepest drill holes, separated by lenses of alluvial materials.
The near surface tills are normally consolidated while the tills from
greater depths are highly over consolidated and dense. It is quite
probable that this over consolidation was caused by glacial loading in
the geologic past. All of the tills contain fines that are nonplastic
or only moderately plastic. Smaller gravel sizes are rounded, while
larger si"zes are more subrounded to subangular. ~laterials are poorly
sorted with little or no indi'cation of bedding. The tills vary con-
siderably in thickness from only a few feet to a maximum of 163 feet
in DR-18. .
Apparent river deposited alluvial lenses which represent inter-
glacial periods, separate many of the till units. These deposits consist
of sandy gravels with some silts. Sandy alluvial units have a tendency
to cave during drilling and several appear to have relatively high
permeabilities. Most of these river deposits were less than 50 feet
in thickness but in DR-22, directly above bedrock, the alluvial unit
was 159 feet thick.
D-2l
At least two deposits of lake sediments were encountered during
drilling. The larger of these was named "Lake Woller" and occurs in
DR-l3, DR-15, DR-26, and DR-27 in varying thi.cknesses. Maximum thick-
ness is 60+ feet in DR-13. Lake Woller deposits appear to be confined
between elevations 2,240 and 2,305 feet. Another apparent lake deposit
was penetrated in DR-18 and DR-20. Maximum thickness of this deposit
is 33 feet and appears to be confined between elevations 2,130 and 2,190
feet. Both lake deposits may represent either quiet lake deposition
during an interglacial period, or possibly proglacial lakes formed
during glacial retreats. The lake deposits consist primarily of highly
to moderately plastic clays and silts with local gravel and sand lenses.
Spi 11 way
The original location of the Saddle Spillway in the Interim Feasi-
bility Report, Appendix I, Plate D-3, was found to lie directly upon
two adverse structures. The overburden depths increased from 9 feet
at DR-17 on the left side of the proposed alinement to 231 feet at DR-18
on the right or east side of the spillway. This depth of overburden
prevailed throughout the length of the spillway, including the proposed
gate structure area.
The glacial tills, clay, and intermittent sand lenses of the over-
burden would have required additional excavation and flatter sideslopes.
Added expense would also have resulted from increased foundation require-
ments for the gate structure and from the full length lining which would
have been required in the spillway channel. To avoid these disadvantages
a change of the channel alinement was made.
The new proposed a1inement lies approximately 800 feet laterally to
the left (southwest) of the original design and will be in rock cut from
inlet to final outlet at Tsusena Creek. This alinement will also avoid
potential structural problems from the second adverse structure, the
shear zone titled liThe Fins" (Plate D-4) which will now parallel the
spillway for its entire length. Rock quality is such that excavated rock
will be used as dam shell rock.
As a result of the move, it is anticipated that sound bedrock will
be encountered at a maximum depth of 25 feet at the gate structure and
will continue down spillway for at least 2,500 feet. As the spillway
dips down to Tsusena Creek, deeper glacial till is again encountered,
so the final section of the outflow may not be totally founded on bed-
rock. The plunge pool at Tsusena Creek will be contained by existing
rock cl iffs.
D-22
Permafrost
The Watana damsite lies within the discontinuous permafrost zone
of Alaska. For this reason it is to be expected that permafrost would
be found during the exploratory effort, particularly on north facing
slopes and areas where arctic vegetation has effectively insulated the
ground surface. Depths of permafrost within the discontinuous zone are
variable and often change drastically within short distances depending
on exposure, ground cover, soil characteristics and other factors.
Permafrost conditions at Watana as indicated by the exploratory
work done to date appear to be typical for the zone. The left abutment
which faces north and is either continuously shaded or receives only
low angle rays from the sun was explored with core drilling equipment.
Five holes were drilled and pressure tested by pumping water into the
drill holes at selected intervals using a double packer. Observation
of drill water returns and pressure tests showed that permafrost exists
for the entire depth of the holes. Holes drilled in the right abutment,
where the sun's rays are most effective, did not indicate any perma-
frost. Within the relict channel areas, on the terrace north of the
right abutment, indications of permafrost were observed as reflected
by ground water conditions and water table measurements, drill action,
and sampling. Drill hole DR-27 was sampled and ice lenses were retrieved
from a depth of 30 through 36 feet. Permafrost was also encountered
during test pit activities. However, in general, permafrost in the
spillway and relict channel area, while encountered as near as 1 foot
to the surface, is expected to be confined to a relatively shallow layer.
This expectation has been reinforced by the fact that ground water has
been encountered at various depths. In order to study the thermal regime
of the permafrost and to more accurately define the lower limits of the
frozen zone, temperature probes were installed at 13 locations. These
locations are shown on Table 1 under the heading "Instrumentation!! and
the graphs of readings taken to date are shown on Plates 0-13 through
0-15. It is still too early to reach definite conclusions from the
limited data obtained since installation due to the fact that heat was
introduced into the regime by drilling and equilibrium may not yet be
reestablished. However, it appears that the readings do support the
conclusion that permafrost is not as widespread or as deep as was previous
believed.
Of equal significance is the fact that the temperature probes
indicate that the temperatures within the permafrost are generally
within 1 degree of freezing. Construction in cold regious has shown
that, within this range, materials can be excavated with considerably
less dificu1ty than in areas where the permafrost temperatures are
lower. Particularly in borrow areas, where a rather large area can be
exposed, degradation is rapid and by alternating from side to side in
the area, the material can be ripped, left exposed to the sun for a
0-23
few hours and then handled in the normal fashion. The fragile nature
of the permafrost regime as indicated by temperature studies will be
of prime importance in the scheduling related to foundation grouting.
Permafrost barely within the frozen range will be much easier to thaw
and foundation grouting will be facilitated.
As explorations at the damsite continue, the installation of frost
probes will be expanded to provide detailed knowledge of the extent of
existing permaforst areas as well as their condition. A discussion of
design type of probes installed and the degree of accuracy to be expected
from data readings can be found under II Instrumentation. II
Ground Water
Ground water conditions in the terrace area north of the spillway
alinement were examined during exploratory drilling, but the use of
drilling mud used for most of the rotary drilling made direct water
table measurements difficult. Pervious zones were occasionally encoun-
tered where loss of drilling mud was noted. Examples are DR-22 where
mud losses were experienced of approximately 50 gallons per foot of hole
drilled between elevations 2,025 and 2,000 feet and losses of approximately
14 gallons per foot of hole drilled between elevation 1,940 and 1,855
feet. In a very few "instances water tables could be measured at the
time of drilling. A notable example of artesian head was measured while
drilling DR-13 and OR-14. In both of these holes the ground water was
under sufficient head to rise from elevation 2,240 and 2,270 feet,
respectively, to elevation 2,300 + feet when the overlying clay layer
was penetrated by the drill. -
A discussion of the overburden units encountered in the terrace
area can be found under the heading "Relict Channel Area." It will
be noted in that discussion that at least two deposits of lake sediments
were encountered which appear to be rather extensive. As might be
expected, perched water was encountered above the higher deposit, Lake
Woller, in some holes because of the impermeability of the material.
In the alluvial zones between the lake deposits water was usually encoun-
tered although, as previously noted, in only one instance was this water
under artesian head. Below the lower lake deposit, approximate elevation
2,190 feet, the glacial tills were very compact and can be expected to be
relatively impervious. The over consolidation of these materials as
previously stated is probably due to being overloaded by the weight of
ice in glacial times.
The significance of ground water conditions in this area lies in
the fact that the deep deposits in the relict channel area will be
under a head of approximately 400 feet from the proposed Watana reser-
voir. The decision as to whether or not an impervious cutoff across
this channel is necessary depends on the pervious nature of the materials
0-24
encountered. While a more detailed program of exploring, sampling,
and testing will be undertaken to ensure that pervious layers will not
present a seepage danger in this area, it is presently believed that
no impervious barrier is required. A more detailed discussion of the
rationale in support of this belief can be found under the heading
"Seepage Control, Relict Channel.1I
Reservoir Geology
The Watana reservoir includes seven general zones of geology, as
indicated by Plate D-5 (Watana Reservoir Surficial Geology). Glacial
fill, outwash, and proglacial lake deposits predominate in the mean-
dering reaches of the river upstream of the Oshetna River confluence.
The next zone extends downstream along the incised channel to Jay
Creek and Kosina Creek, and includes localized sedimentary and alluvial
units with metamorphics such as the Vee Canyon schist. The predominat-
ing dioritic gneiss and amphibolite is laced with bands of mica schist,
pyroxenite, and augen gneiss that are inferred to correspond with contact
and shear zones trending northeast. The area around Jay and Kosina
Creeks and downstream to Watana Creek includes two zones with outcrops
of high grade schist and basalt flows at the river level. The surround-
ing hills are composed of volcanics with limestone interbeds on the
south, and mixed volcanics and near surface intrusives to the north for
a minimum of 10 miles. The Watana Creek area consists of basalt flows
and semiconsolidated predominately clastic sediments overlain by thick
glacial and outwash deposits. This area also contains the Talkeetna
Thrust as identified by the U.S. Geological Survey. Downstream of
Watana Creek lie the remaining two units, starting with moderately
metamorphosed sediments (phyllite. argillite, graywacke) with two bands
of schist. The final unit starts just upstream of Deadman Creek and
includes all materials downstream to Fog Creek below the damsite. The
predominate types are the diorites, granites, and migmatites of the
damsite pluton.
The Watana reservoir includes many permafrost areas, especially on
north facing slopes. Frozen overburden will tend to slough as the
reservoir is filled and the permafrost degrades. Since most of the
lower canyon elevations are covered with only shallow overburden deposits,
sloughing will be minor and have minimal effects upon the reservoir.
Deep overburden deposits, mostly of glacial origin, occur above approxi-
mate elevation 2,000 feet where the slopes flatten out into a broad river
valley base level. Most of these glacial deposits will be stable due to
the flat topography.
Some rock and overburden landslide deposits have occurred within
the reservoir area. One such slide deposit, known as the "Slide Block,lI
is located upstream of the axis on the south bank opposite liThe Fins"
shear. Several old and potential landslides are identified by Kachadoorian
and Moore in their reconnaissance of the project area.
0-25
In general terms, the geology in the immediate damsite is controlled
by the diorite intrusive believed to be the top of a stock which uplifted
the surrounding sediments and volcanics and was later eroded by glaciers.
Subsequent glacial and stream deposition has masked much of the flat
upland areas and stream valleys.
DAM DESIGN
Dam Foundation Treatment
Main Dam: Foundation conditions are more than adequate for con-
struction of an earth-rockfill dam. The underlying rock is a diorite
or granodiorite which, in nonfractured fresh samples, had unconfined
compressive strengths that ranged from 18,470 to 29,530 psi. Only the
uppermost 20 to 40 feet of this rock is closely fractured and suffi-
ciently weathered to require removal within the core area. Stripping
depths along the centerline section are shown on Plate 0-7. Stripping
to sound foundation rock is required for the entire length and width of
the impervious core. Foundation treatment within the rock excava-
tion area will include removal of all loose and highly fractured rock
and soft materials, cleanup, and dental treatment. If there are any
zones where more than an 8 foot width of soft materials is removed, the
dental concrete will be contact grouted to the adjoining rock. Stripping
to rock will also be required under the remainder of the embankment area.
However, in this area excavation will not include removal of the inplace
rock. Only the loose and severly weathered surface rock will be removed.
Steep or overhanging rock walls will be trimmed to a smooth shape for
proper placement of embankment materials. Exploratory drilling in 1978
has shown the materials in the river channel to be a well graded mixture
of gravels and cobbles as good, or better, than the materials that
would be used to replace them. As the exploration program continues,
these gravels will be more completely explored and it may be demonstrated
at that time that there is no need for their removal beneath the shell
zones. Should this prove to be the case, the change can be made during
feature design.
Provision has been made for a 6-by 8-foot concrete grouting gallery
with concrete lining to be constructed in foundation rock under the
impervious core. This gallery will begin at elevation 1,900 feet on
the left abutment and will terminate at elevation 1,800 feet on the
right abutment. It will provide access for drilling and grouting which,
in some areas may be delayed to allow thawing of permafrost. Access
to the gallery will be provided from the powerhouse on the left abutment
and, by adit, from the downstream toe of the right abutment. Grouting
w'ill be on a single line of holes utilizing split spacing, stage grout-
ing techniques. Grout holes will be slanted upstream and may be included
0-26
to intercept the dominant high angle northwest tending fracture system.
Preliminary grout hole depths are estimated at two-thirds the height
of the embankment to a maximum depth of 300 feet with primary spacing
of 20 feet, secondary spacing of 10 feet. and tertiary spacing of 5
feet with additional holes as required.
Determination of final grout hole depths, spacing, inclination,
grout mixtures, and grouting methods will be dependent on the results
of future explorations, permeability studies, test grouting, and perma-
frost thawing investigations.
Rock permeability test results are shown on the drill logs presented
on Plates 0-28 through 0-37. Coefficients of permeability (K) were
computed in feet per minute times 10-4 , Permeability coefficients
ranged from 0.0 to 23.1 and average 4.9 for those holes that were tested.
Drill holes in the left abutment area indicated very low permeability
due to permafrost. River section hole DH-l had variable permeability
coefficients that range from 0.48 to 2.52 and averaged 1.98. Drill
water returns in the river holes were quite variable throughout the
entire hole depths and tended to drop off to low percentages at the
greater depths in the axis area. Right abutment drill holes had perme-
ability coefficients that ranged from 0.0 to 23.09 and averaged 5.47.
DH-10 was the only hole tested that had relatively low permeability
coefficients throughout. Drill water returns had similar patterns with
variable percentage losses. DH-7 and DH-9 had 0 percent returns through-
out and DH-8 and DH-ll maintained high percentages of drill water returns
throughout.
The existence of permafrost in the left abutment and the possibi-
lity of minor amounts in the right abutment necessitates assessment of
the problem of thawing a zone in the foundation bedrock sufficiently
wide and deep to allow proper installation of the grout curtain. In
anticipation of this need, the U.S. Army Cold Regions Research and
Engineering Laboratory was asked to do a desk study on thawing the per-
manently frozen bedrock. The Technical Note which was submitted in
response to the request is included as Exhibit 0-4.
Embankment Design
Design of the dam embankment at Watana damsite has been based on
the availability and proximity of construction materials in addition to
their suitability as engineering materials. As a result of these con-
siderations, the embankment contains a central section consisting of an
impervious core buttressed on the downstream side by a semi pervious zone.
D-27
This central section is supported, both upstream and downstream, by
suitable fine and coarse filters and rockfill shells. A typical cross-
section of the embankment is shown on Plate D-9.
The impervious core and semipervious zone will be constructed using
the glacial till which is readily available in the area. The semi-
pervious material will be obtained by selecting the coarser grained
materials while the finer materials will be placed in the impervious
zone. These materials, as discussed under IIEmbankment Materials,1I have
been shown by exploration and test to be a well graded mixture, which,
when compacted, has a very good shear strength and a high degree of
impermeability. Tests have shown that this material is quite sensitive
to moisture control; therefore, special attention must be paid to this
aspect of the design and construction. The 14,000,000 cubic yards
required are available within a very reasonable haul distance and will
only require removal of oversize boulders prior to use.
The fine filter material can be obtained from the gravelly sand
deposit at the mouth of Tsusena Creek. Chart D-3 shows an envelope of
gradations from this source superimposed onto the envelope for the fine
filter as established by engineering design criteria. This comparison
indicates that the Tsusena Creek source can provide material within the
ranges of sizes necessary to protect the core and semipervious zone
against piping or migration of fines into the filter material.
Proven sources of gravel which can yield large quantities of material
are scarce within short haul distances of the project. For this reason,
the decision was made to use material from the rockfill source as a
coarse filter. Chart D-5 is an envelope of the required gradation
which will provide proper filtering action for the fine filter material.
A curve has been superimposed on this envelope which represents the
materials expected from the rockfill source. As indicated, the rockfill
will provide the proper filter action. The maximum size material in
the coarse filter and the lift thickness for placement will, of course,
be limited to ensure design criteria are met.
The decision to utilize rockfill rather than gravel for the embank-
ment shells was made when reconnaissance and exploration indicated that
dependable deposits of gravels which would provide the necessary quanti-
ties could not be verified within reasonable haul distances of the dam-
site. On the other hand, rockfil1 can be readily obtained as discussed
under IIEmbankment Materials." Riprap for wave protection can be obtained
from the same source.
It is recognized that the 1 vertical on 2 to 2.25 horizontal side-
slopes shown on the typical cross section for the dam are conservative
for a rockfill dam, and, if rockfill is used, these slopes will be re-
fined in accordance with sound engineering practice. Refraction seismic
D-28
lines in the borrow areas show velocities which could represent large
deposits of gravels or glacial materials but rather extensive explora-
tions will be required to verify the true nature and quantity of the
materials. Should these explorations reveal that suitable gravel
deposits in the area are sufficiently extensive to provide the large
quantities required for the dam shell sections, the gravel will be
used in preference to borrowing quarried rock for rockfill.
Powerhouse and Underground Structures
An underground powerhouse is well suited to meet the restrictions
of subarctic weather and other environmental factors. Topographically,
the narrow Susitna Canyon is well situated for this type of underground
construction. The diorite pluton that underlies the foundation area
is expected to be competent for excavation and support of underground
facilites, but the location and design of the various structures may have
to be adjusted in some areas. liThe Finsll and "Fingerbuster ll Shear Zones
shown on Plate 0-3 and discussed in paragraph "Rock Structure" are the
two most significant shears within the damsite area. Other northwest
trending steep angled minor shears involving displacements of a fraction
of an inch up to a few feet are common in the site area and were noted
in many of the dri 11 holes. These minor shears appear to represent mass
adjustments to regional stress and compensation can be made for them in
design and construction of the underground structures.
Prior to powerhouse excavation, exploratory adits located near the
crown of the various chambers will be driven to confirm final design
criteria. The chambers will be constructed with straight walls as
required for maximum dimensions, and not notched or cut irregualarly
for support of interior powerhouse facilities. Rock support will include
pattern bolts consistent with wall and crown conditions. Use of steel
channeling and remedial concrete is anticipated in local areas where
fallout may occur or in fracture zones having a substantial width of
crushed rock. Wire mesh will be utilized where necessary as a temporary
facility prior to placing concrete. A thin layer of wire reinforced
shotcrete may be placed on the main powerhouse chamber walls and crown
as a protective measure against rock raveling. Additional shotcrete
will be utilized, as required, to seal surfaces and retain rock strengths.
Construction methods in the large chambers will include controlled blast-
ing and rock removal in lifts from the top downward. Gutter and floor
sloping for drainage will be provided in the interior structures between
chambers.
Intake Structure
Consolidation grouting may be necessary for the intake structure
foundation and the bridge pier footings. The higher bridge pier
footings will also be recessed into sound rock. Tunnel portals will
0-29
be designed so that there is a minimum of two tunnel diameters of sound
rock above the heading where they go underground. Initial tunnel
support will be by pattern bolts, with steel channeling and wire mesh
where necessary in closely fractured areas. Major shear zones will
require steel supports. Hydraulic and geologic considerations will
necessitate final concrete linings for all but the access tunnels, and
steel liners for the penstocks. Grout rings will be required in the
penstock portal areas.
The two diversion tunnels are to be separated by a minimum of four
tunnel diameters to provide greater structural stability. Downstream
diversion tunnel portals will have to be located to avoid the "Finger
Buster" shear zone to insure adequate portal construction conditions.
Spillway
The gated spillway has been relocated about 800 feet southeast of the
alinement presented in the 1976 report so that it will be constructed
in a through rock cut. The spillway will be unlined beyond the spill-
way gate structure and apron. The new spillway alinement extending
from the Susitna north valley wall to Tsusena Creek and the spillway
gradient are shown on Plates B-2 and B-5. It is anticipated that, with
the exception of minor amounts of waste, all the excavated materials
from the spillway will be used in the dam embankment. The major part
of the excavation is in rock and this material will be used in the
shell sections. The overburden materials are glacial till which, when
separated from the boulders can be used in the impervious or semi per-
vious zones.
Seepage Control -Relict Channel
The relict channel area is an overburden terrace underlain by a
bedrock depression, and extends northward from the right abutment for
about 6,000 feet. This terrace is composed of glacial till, some of
which has been reworked by alluvial action. For this reason, consid-
eration was given to the possibility of seepage through the area where
rock contours are below the proposed reservoir elevation. However,
preliminary seepage calculations indicate that even in the relict
channel area, where the head differential approaches 350 feet, and
using a very conservative 'k' value of 500 feet per day, the seepage
would be less than 0.02 cubic feet per second per foot of width for
a pervious layer assumed to be 80 feet thick. Assuming such a layer
to be 200 feet wide, the seepage would be in the order of 4 cubic feet
per second, which is a minor amount. The exit velocities associated
with such seepage w0Yrd be too low to cause serious piping or erosion.
Investigations during the summer of 1978 support this conclusion. In
ho 1 es DR-13 and DR-14, located in the vi ci nity of Borrow Area "0, II
ground water was encountered in alluvial layers between elevation 2,240
0-30
and 2,280 feet with an artesian head which exceeded the proposed reser-
voir level by 100 feet. In spite of this high head condition, no
evidence was found indicating seepage out of this layer into either
Deadman Creek or Tsusena Creek. Indeed, it is probable that the effect
of this artesian water, which evidently has its access to the alluvial
layer in the upper reaches of Tsusena or Oeadman Creek, would be to
resist flow from the reservoir into the aquifer. Because mud losses
in OR-22, located at the center of the relict channel, indicated the
possibility of permeable layers at approximate elevations 1,900 and
2,000 feet, a falling head permeability test was performed at this hole.
The permeabilities calculated from this test are a further indication
the seepage through the terrace would be minor or nonexistent. Conse-
quently, it was unnecessary to include any cutoff through the saddle
and relict channel area.
CONSTRUCTION MATERIALS
Material Requirements
Embankment: Approximately 57,792,000 cubic yards of embankment
materials will be required to construct an earthfill dam at Watana site.
The impervious core is estimated to require 7,373,000 cubic yards and
the semipervious fill zone 6,077,000 cubic yards of material. The fine
filters are estimated to require 5,621,000 cubic yards of material and
the coarse filters 2,201,000 cubic yards. The pervious rock shells,
which make up the largest portion of the dam, will require approximately
36,297,000 cubic yards. Slope protection on the upstream side of the
dam is estimated to require 223,000 cubic yards of riprap.
Sources of Materials
General: Several sources of embankment materials were investigated
in the damsite area. These sources included two quarry locations which
could yield rock shell and coarse filter materials, a source of glacial
till which could produce core material, and two areas containing rela-
tively clean sands and gravels for the fine filter material. Additional
embankment materials will be generated by required excavation for the
dam foundation, underground facilities, and the spillway channel. All
rock excavation from the spillway channel will be incorporated into the
rock shell zone of the dam. The overburden encountered in the excavation
for the spillway channel will be glacial till which can be processed by
removal of oversize material for use as core material.
Rock Shell Materials: Rock shell materials may be obtained from
two quarry locations shown on Plates 0-10 and 0-11.
0-31
Quarry sites were located on the left abutment of the dam (Quarry
Source 'AI) and in the northwest quadrant of the confluence of Deadman
Creek and the Susitna River (Quarry Source'B'). The Quarry Source (A)
on the left abutment is an outcrop of igneous rock ranging in elevation
from approximately 2,300 to 2,630 feet. The total volume of the hill
above the surrounding terrain is approximately 200 million cubic yards
of rock. Development would consist of open faces on the north flank
of the dome with the final quarry floor at an elevation of 2,300 feet.
This type of development would maintain the visible profile of the hill
essentially as it is now. The resulting quarry floor could provide an
ideal site for parking areas, visitor facilities, and perhaps, the
switchyard.
The material in the hill is a diorite on the western side and a
rhyodacite porphory on the eastern half. The appearance of outcropings
and exposed faces of each material indicates that the hill is composed
of sound rock.
The product of this quarry will be used for the rockfill shell
zones of the dam and in the coarse filter and riprap. This site
(Quarry IA') represents the nearest source of adequate quantities of
rock materials for the dam. From the approximate center of the quarry
to the approximate center of the dam is a distance of 4,000 feet and
movement of material would be downhill. If properly developed, virtually
all of the material removed from the quarry will be used in the dam
and the oversize material, overburden and weathered waste material can
be disposed of immediately adjacent to the quarry in the reservoir
area upstream of the dam.
The quarry source at the confluence of Deadman Creek and the
Susitna River (Source IBI) could be developed by excavating rock from
the open faces visible on Deadman Creek and continuing the development
of a face to the westward, maintaining the face between elevation
1,700 and 2,000 feet. Stripping and clearing would be minimized by
developing a long, narrow quarry paralleling the river and using the
quarry floor as a haul road for the length of development. If exploited
in this way, the quarry could yield 17,000,000 cubic yards of material.
The rock exposed in this area is a moderately weathered diorite.
The product of this quarry could be used on the rockfill shell sections
of the dam. The distance from the center of the Quarry IB' to the
center of the dam ;s approximately 2 miles.
The only reason for utilizing this quarry source instead of the
Quarry IAI on the left abutment would be the lessened environmental
impact since the quarry at Deadman Creek would be entirely in the
reservoir area. However, since the haul distance is greater and the
D-32
net environmental impact of the Quarry 'A' on the left abutment is
small, this area is a less desirable source of embankment materials.
Core Material: Impervious and semi pervious materials can be excavated
from the glacial tills which are present at the damsite. The most logical
source of glacial till appears to be in an area denoted as Borrow Area
'0' which lies between Deadman Creek and the saddle on the north side
of the dam (see Plate D-11).
Exploration in this area was accomplished by drilling with a track-
mounted, self-propelled auger and a Failing 1500 rotary drill, by test
pitting with a backhoe, and by use of seismic refraction methods. Five
holes were completed using the air rotary drill, 14 holes were completed
using the auger, 14 pits were completed with the backhoe, and 4 seismic
refraction lines were extended across the proposed limits of the borrow
area. The material in the area is composed of a surface layer of natural
ground cover of roots and moss, approximately 2 feet of boulders and
organic silts underlain by the tills which are classified as gravelly
silty sands. The tills range from 15 to 25 feet thick and usually over-
lie a clay. sandy gravelly clay and silty sandy gravel.
Sack samples from the test pits (in Borrow Area D) were tested at
the North Pacific Division Materials Laboratory to determine gradations,
compaction, consolidation characteristics, permeability', and triaxial
shear strength.
Gradation tests were run on each sample from each test pit. An
envelope of the gradation curves derived from the tests of samples from
Test Pits 8 through 19 is shown on Chart D-2. Because the range of
gradations of materials from the test pits centrally located in the area
is limited. a composite sample was formed. Use of a composite sample
was necessary to provide adequate material for a representative testing
program since retrieval of large bu"lk samples from the site was not
possible.
The coefficient of permeability (K20) for the minus l-inch fraction
of the till material, compacted to 95 percent of maximum density with
an optimum water content of 7.5 percent equals 10.90 X 10-6 cm/sec.
This relatively low coefficient of permeability is coupled with an
adequate shear strength at the optimum water content, acceptable con-
solidation values even when loaded to 32 tons/sq ft and a narrow band
of gradation throughout the central portion of the outlined borrow
area. The shape of the compaction curves indicates that moisture
content is critical in obtaining maximum densities with a pronounced
peak at the relatively low optimum moisture content of 7.5 percent.
The results of the triaxial compression tests indicate that in the
unsaturated and undrained condition the glacial tills will be sensitive
D-33
to moisture contents higher than optimum but that if placed on the dry
side of optimum they will maintain strength essentially equal to those
obtained when placed at optimum.
The results of this testing program indicate that the glacial tills
can be placed and compacted to provide a suitable material for both the
impervious and semipervious zones. The specifications will need to
provide for close controls of the moisture content and the quality
assurance programs will have to be adequately staffed to provide for
careful checks of moisture content in the pervious and semi pervious
fill. Deta"iled laboratory reports of the tests conducted are included
as Charts D-6 through D-29.
The materials from Borrow Area 0 can be used with very little
processing. The ground cover and organic silts and boulders will be
stripped from the surface and disposed of as designated near the mouth
of Deadman Creek in the reservoir area. The remainder of the material
can be utilized in the core of the embankment if oversize (12 inch plus)
material is removed by mechanically raking in the pit or on the embank-
ment fill. Less than 10 percent of the material will be too large to
use in the core. Since removal of only the silty, sandy gravel above
the clays will result in the floor of Borrow Area IDI being above
reservoir elevation, it will be necessary to contour and seed the
borrow area after the completion of removal of materials as a restora-
tion measure. Approximately 630 acres will be restored.
Filter Material: The nearest source of clean sands and gravels
for use in the fine filter of the embankment dam is an alluvial deposit
formed by materials washed out of Tsusena Creek and deposited at the
confluence of Tsusena Creek and the Susitna River on the right bank
of the Susitna (Borrow Area lEI, see Plate 0-12). Haul distance to the
dam ranges from 3 to 5 miles. This area was explored by digging 5 test
pits to a depth of 8 feet using a backhoe mounted on a small tractor.
The material in this area is composed of approximately 2 feet of
organic, sandy silt overlaying 6 feet of clean, well graded sands and
gravels having maximum size particles of up to 4 inches in diameter.
The materials are sound, well rounded particles. The bottoms of the
test pits indicate the possibility that the materials deeper than 8
feet below the ground surface contain up to 50 percent of boulders in
excess of 8 inches in diameter and ranging up to 24 inches in diameter.
The 6 feet of material which lies above the boulders may be used in
the embankment with required processing limited to some blending and
removal of material larger than 12 inches to produce fine filter
material. An envelope of gradation curves derived from tests of
samples from TP-l through TP-5 is shown in Chart 0-1. All of the samples
are from the first 8 feet of material. All of this material lies above
0-34
the water table and can be taken by front loaders. The quantity of
material available in the first 8 feet is approximately 3.7 million cubic
yards. After the boulders are encountered at a depth of 8 feet, the
oversize material will have to be removed and material below the water
table will have to be bailed from the area. A dike will be maintained
to separate the borrow operations from the river so that all turbidity
created by the excavation of materials will be filtered or settle prior
to entering the Susitna River. In terms of grading, particle soundness
and proximity, this area represents an excellent source of essential
filter materials.
The second area in which clean sands and gravels were located is
in the upper reaches of Tsusena Creek, north of Tsusena Butte (Borrow
Area 'C'). The materials are sound, well rounded particles and are
well graded with maximum sizes generally less than 4 inches. Consider-
able exploratory effort would be necessary to ensure quality and quantity
of materials before this could be considered an acceptable source.
Because of the haul distance of 12 miles, this source will not be con-
sidered unless further explorations and testing indicate that adequate
materials may not be obtained from the sources closer to the damsite.
Exploration at Site 'C' was accomplished by digging one test pit,
reconnaissance of the area on foot and from helicopter, and with a
seismic survey.
Concrete Agaregates: Approximately 310,000 cubic yards of concrete
will be require to construct the appurtenant structures for an embank-
ment dam at Watana damsite. Most of this will be structural concrete
placed in tunnel linings, the powerp1ant, gate structures, intake struc-
tures, and spillway channel lining. Maximum size aggregate will be 3
inches in all but the smaller structures or those with closely spaced
reinforcing. The most readily available source of concrete aggregate is
available at the confluence of Tususena Creek and the Susitna River
(Borrow Area 'E'). The materials from the first 8 feet in the alluvium
can be utilized with only limited screening. As oversize materials are
encountered at greater depths, the larger particles will be crushed for
use in the concrete aggregate, thereby achieving maximum utilization
of gravels from the area and also to increase the tensile strain resis-
tance of the concrete which will lessen problems with thermal cracking
in the more massive sections. Since Borrow Area E represents the most
economical source of concrete aggregate and the nearest acceptable
source of essential filter material, maximum utilization of the material
in this area ;s required.
A petrographic analysis of sands and gravels from Borrow Area E
was conducted by the Missouri River Division Laboratory at Omaha,
Nebraska. The results show the material to be approximately 70 percent
0-35
granitic rock with the remainder composed of basalt, andesite, and
ryholite. Chert is present in such small quantities as to be nondele-
terious.
The quarry site on the left abutment (Quarry Source IAI) is con-
sidered an alternate source of concrete aggregate. If material from
the quarry were used in the embankment dam aggregate could be produced
by placing a crushing and screening plant in the quarry and producing
the concrete aggregate incidental to the production of embankment material.
The concrete aggregates would be produced from the diorites in the
quarry to avoid the potential of problems caused by the reaction of
the alkalis in the concrete with the rhyodacite porphory in the eastern
half of the hill.
The materials in upper Tsusena Creek (Borrow Source IC I ) would
produce excellent concrete aggregate; however, because of the haul
distance involved (10 miles), it is not anticipated that this source
would be exploited to produce concrete aggregate unless embankment
materials are also taken from the same source.
It is anticipated that because of the relatively small quantities
of required concrete aggregate compared to the large quantities of the
various classes of embankment materials, that concrete aggregates will
be produced incidental to the production of embankment material and
stockpiled adjacent to the batch plants used.
The first concrete required on the project will be that required
to line the diversion tunnels and form gate and trashrack structures
for river diversion. The aggregate for this work could be produced
from Borrow Area E with a resulting haul distance of 2.3 miles.
0-36
NPDEN-GS-L (79-S-404)
WATANA DAM
Composite No. 1
14 NOV 1978
Report of Specific Gravity & Permeability Tests
1. Specific Gravity & Absorption (ASTM Cl27 & C128)
Bulk
Bulk, SSD
Apparent
10 Absorption
3/4 in. -No.4
2.633
2.671
2.737
1.44
Minus No.4
2.683
2. Coefficient of Permeability (Minus 1 inch material)
Remolded Density 126.6 P.C.F.
Optimum Water Content = 7.5%
Permeability KZO 10.90 x 10-6 cm/sec.
0-44
Chart D-8
~------------------------------------------------------------------------------.--~
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(" lCi.: CD
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lJ
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U}
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+' ~ i ' '
+.
0 . '
,
Standard Compaction Density
(126.6 P.C.F;) and Optimum
Water Content (7.5%).
. ~ .. . ~ , i .
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:-------,,---,------------------1
Area
i-.--------------------r-----~----~-~_.~
Bor1.n4!; No. Sample Jc$<;>mposite No.1
~h---' Datel4~
NPD TRIAXIAL COMPRESSION TEST ~
~--------------------------~~----EHG I'ORM
t JUN U 2089 (EM lJ1().;l-1902) PI'! E"'OU~ EO' T'ONS ARE OIlSO~ E T E
TRANSLUCENT 0-50
Chart D-14 r .,
" L
Coefflcient of Permellb1l1ty, ~O'
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0.27 L~ ["\
0.1 0.2 0.3 0.40.5 1 2 3 4 5 10 20 25 "!>Z-
Pressure, p, T/sq ft
Type of Specimen Remold Before Test After Test
D1em 4.445 In. Rt 1.006 in.
Overburden Pressure, Po T/sq ft
Preconsol. Pressure, Pc T/sq ft
CCIII;Iression Index, Cc 0.06
Classif1cat10n Si. SAND (SM)
LL G 2.68 s
PL D10
Remarks Remolded at 95% Standard
Compaction Density (122.5 P. C . F
and Optimum Water Content plus
4%(13.3%)
IMG 1'011101
I !olAV 6J 2090 PREVIQUS EDITIONS ARE OBSOL.ETE.
Water Content, Vo 13.3 '1> v f 10.9 '1>
Void RatiO, eo 0.365 ! e , f 0.289
Saturation, So 98 '1> Sf 100 1-
Dry Density, ']' d 122.5 lb/ft3 129.8
k20 at eo = X 10 -em/sec
Project WATANA DAM
Area
)eoriDg No.
Composite No.1
Sample No.
Depth Date I4 NOV 1978 El
NPDCONSOLIDATION TEST REPORT
(TRANSLUCENT) " ~424
D-63 Chart D-27
EXHIBIT 0-1
Location Maps and Seismic Refraction Velocity
Profiles; Watana and Devil Canyon Oamsites.
EXHIBIT D-2
Reconnaissance of the Recent Geology of the
Proposed Devil's Canyon and Watana Damsites,
Susitna River, Alaska.
RECONNAISSANCE OF THE RECENT GEOLOGY
OF THE PROPOSED DEVILS CANYON AND WATANA
DAMSITES, SUSITNA RIVER, ALASKA
by
Reuben Kachadoorian
and
Henry J. Moore
CONTENTS
ABSRACT--------------------------------------------------------------1
INTRODUCTION---------------------------------------------------------3
GEOLOGIC BACKGROUND--------------------------------------------------6
PROCEDURES-----------------------------------------------------------9
Ground and aerial observations-----------------------------------12
Visual observations during helicopter overflights----------------20
First order leveling observations--------------------------------31
Additional observations------------------------------------------33
Seismic activity-------------------------------------------------35
SUMMARY--------------------------------------------------------------38
RECOMMENDATIONS------------------------------------------------------39
REFERENCES CITED-----------------------------------------------------40
ii
Illustrations
Figu~
1. Overlay showing actual and inferred faults-----------------in back
Tables
1. Inferred faults-------------------------------------------------8
2. Partial list of scarps and landforms----------------------------ll
3. Location of selected examples of scarps-------------------------22
4. Selected examples of landforms----------------------------------23
5. Location of old and potential landslides------------------------27
6. Location of patterned ground------------------------------------28
7. First order leveling results------------------------------------32
iii
PRELIMINARY REPORT OF THE RECENT GEOLOGY
OF THE PROPOSED DEVILS CANYON AND WATANA
DAMSITES, SUSITNA RIVER, ALASKA
by
Reuben Kachadoorian and Henry J. Moore
ABSTRACT
At the request of the Corps of Engineers, the U.S. Geological
Survey conducted a reconnaissance of the recent geology of the proposed
Devils Canyon and Watana damsite areas, Susitna River. Alaska. The
purposes of the reconnaissance were to look for active faults and other
geologic hazards. Field work by the Geological Survey was conducted
between July 25, 1978 and August 7, 1978 using a helicopter which was
shared jointly and in cooperation with personnel of the Corps of
Engineers.
The geologic reconnaissance of the proposed Devils Canyon and
Watana damsite and reservoir areas did not uncover any evidence for
recent or active faulting along any of the known or inferred faults.
Recent movement of surficial deposits has occurred as the result of mass
wasting processes and, possibly, by seismic shaking and minor
displacements of bedrock along joints.
Landsliding has occurred in the past and future landsliding appears
probable. The occurrence of unconsolidated glacial debris, alluvium,
and Tertiary sediments at elevations below the proposed reservoir water
levels may slump and slide into the reservoirs when they are inundated.
Some of these sediments may be permanently frozen and, locally, may be
1
ice-rich which increases the probability of slumping and sliding when
the sediments are thawed by the water impounded behind the dams.
The tectonic framework of the Devils Canyon and Watana damsite
areas is not well understood. The present knowledge of the area
indicates that the seismicity of the region ranges in depth from less
than 10 km to greater than 175 km.
Additional detailed geologic and seismic studies are necessary in
order to reliably evaluate the potential geologic hazards in the region
of the proposed dam and reservoir sites.
2
INTRODUCTION
The feasibility of two dams on the Susitna River, Alaska, is
currently under evaluation by the U.S. Army Corps of Engineers. The
Corps of Engineers has proposed two dams for the purpose of developing
the hydroelectric power potential of the Susitna River: one at Devils
Canyob and the other at the Watana site. The proposed Devils Canyon
site is located about 29 km (l8 miles) upstream from Gold Creek Station
on The Alaska Railroad. This dam would be 194 m (635 ft) high and the
reservoir formed would have a water altitude of 442 m (1,450 ft) above
sea level and would extend about 45 km (28 miles) upstream to the
proposed Watana site. The height of the proposed Watana dam would be
247 m (810 ft) and its reservoir would have a maximum water altitude of
671 m (2,200 ft) and extend upstream 87 km (54 miles). The total power
produced by both structures would be about 600 megawatts (MW);
approximately 270 MW at Devils Canyon and the remaining 330 (MW) at
Watana· The current proposed locations for the damsites are shown in
Figure 1.
The study of active faults, seismic activity, potential and recent
landslides, and other potential geologic hazards are of particular
concern in the preliminary evaluation of the proposed Devils Canyon and
Watana damsites and their reservoirs. The U.S. Army Corps of Engineers
requested the U.S. Geological Survey to make such a study.
Authorization for the Geological Survey to make the study is embodied in
a letter from F. R. Brown, Technical Director, Corps of Engineers
Waterways Experiment Station to Dr. Dallas Peck, Chief Geologist,
Geological Survey (Appendix A) and a proposal letter to Dr. Ellis
3
Krinitzsky, Corps of Engineers, by Reuben Kachadoorian (Appendix B). In
practice, the scope of this reconnaissance was modified to include a
much larger area than that stated in Appendix B.
This report is based essentially on reconnaissance geologic
observations, both on the surface and from overflights, between July 25.
1978 and August 7. 1978. Field work was conducted using a helicopter
which'was shared jointly and in cooperation with Corps of Engineers
personnel who were conducting detailed studies at the proposed Watana
damsite. Unfortunately, adverse weather significantly curtailed the
number of surface observations during the limited amount of time that
the helicopter was available to us.
Details of the bedrock geology are beyond the scope of this report
but the geologic map and report of Csejtey and others (1978) is included
in this report as Appendix C for the sake of completeness and because we
refer to some of the geologic map units. The geologic map in the report
was important to our reconnaissance and wherever we field checked it. we
found it to be correct and commensurate ~th its scale. It should be
realized that mapping at a larger scale would permit finer subdivision
of the map units and portrayal in more detail. Additionally, the
definitions of the map units are not directed toward engineering
problems, but rather geologic ones; and. therefore, this fact must be
considered when using the enclosed geologic map. The map should be used
only to determine the gross geologic setting of the proposed Devils
Canyon and Watana damsites and their reservoirs. The map includes all
of the Talkeetna Mountains, Alaska, Quadrangle, and small segments of
the Healy, Alaska. Quadrangle, in the northwest part of the map and the
Anchorage. Alaska. Quadrangle in the south.
4
Figure 1 is intended to clarify the discussions and data presented
in this report. It has three parts: (1) a 1:250,000 scale topographic
map of the Healy, Alaska, Quadrangle, (2) a 1:250,000 scale topographic
map of the Talkeetna Mountains, Alaska, Quadrangle, and (3) a
transparent overlay depicting the inferred and actual faults in the
reconnaissance area. The overlay includes the northern three-fourths of
the Talkeetna Mountains Quadrangle and the southern one-fourth of the
Healy Quadrangle. the transparent overlay may be superposed on the
topographic maps to locate the inferred and actual faults and other
items in the text. Additionally, certain features discussed in the text
can be located on the topographic maps by Townships, Ranges, and
Sections. The geologic map in Appendix C also has the same scale as the
topographic maps and transparent overlay.
We must emphasize that the data and conclusions presented in this
report are based on a reconnaissance study of the proposed Devils Canyon
and Watana dam and reservoir sites. To evaluate thoroughly the proposed
damsites and their reservoirs additional studies must be made. We
specify some of these studies later in this report.
5
GEOLOGIC BACKGROUND
The geology of the Susitna River area (Csejtey and others, 1978;
Appendix C) is rather complex. Bedrock consists chiefly of tightly
folded, metamorphosed, and faulted volcanic and sedimentary sequences
that range in age from late Paleozoic to late Cretaceous and of late
Cretaceous to Early Tertiary granodiorite (55 to 75 m.y. old). These
rocks are overlain by Tertiary volcanic and sedimentary rocks (about 50
to 58 m.y. old). Tertiary sediments of possibly late Oligocene age
(about 25 m.y. old) (Wolfe, written communication, 1977) are exposed in
Watana Creek about 7 km (4.5 miles) upstream of its confluence with the
Susitna River. The Tertiary sediments are gently tilted and possibly
faul ted.
Unconsolidated sediments of late Wisconsin glaciation (8,000-
12,000-years ago; Pewe, 1975) cover much of the study area. These late
Wisconsin glacial sediments consist of unconsolidated tills, moraines,
sand and gravel deposits and eskers. Glacial scour features caused by
this glaciation are also present. The glacial sediments, in turn, have
been and are being eroded, cut, and modified by the Susitna River
drainage system and by mass wasting. These recent geologic events are
represented by V-shaped valleys, river sands and gravels, terrace
sediments, solifluction, slumps, landslides, talus, lakes, stream
channels, and other features due to mass wasting processes.
The late Wisconsin glaciation (8,000 to 12,000 y. old) covered the
Devils Canyon, Watana dam, and reservoir sites. Kachadoorian (1974)
reported field evidence from Devils Canyon indicating that the Susitna
River occupies the same channel at the present as it did prior to the
6
Late Wisconsin glacial period. Recent discovery of glacial debris on
the floor of the Susitna River Canyon upstream from the Watana damsite
confirms Kachadoorian's previous observation at Devils Canyon.
Of particular interest here are the faults that have been inferred
to exist by various investigators in the area. These faults are shown
in Figure 1 and are listed in Table 1. Table 1 also includes the
designation, type, and the reference from which we obtained the
information about these faults.
7
lIuaber
2.
3.
s.
6.
7.
8.
9.
10.
11.
12.
13.
u.
15.
16.
table 1. Inferred faulta in the general area of the Devil. Canyon
and Watana damaite., Susitna River, AlaskaY
Dealgnatlon
Zone of intenae
Ih.arina
talkeetna Thrust
Hear Watana Creek
Near Portage Creek
Chulitna It1ver
North of VABH Sheep
West of VABM Sheep
Suaitna Fault
Reference
Csejtey and others, 1978
Caejtey and others. 1978
Caejtey and others, 1978
Caejtey ano. others, 1978
Caej tey and others, 1978
Caejtey and others, 1978
Caejtcy ana others, 1978
Anon., 1974a. Turner and
others, 1974; Gedney and
Shapiro, 1975; Turner and
Smith, 1974
Near Clarence Lake Beikman, 1974; Smith and
others, 1975; Turner and
Sm! th, 1974
Near VABH Windua Belkman, 1974; Smith and
others, 1975, Turner and
Smith, 1974
North of VABMa Crebe-Anon., 1974a; Beikman,
Ht. Watana Salith and others, 1975,
Turner and Smith, 1974
East of VABH Sumarti-Anon., 1974a
dason
Watana Creek
North of Denali
Cretaceous to recent
ahearing
Anon., 1974a; Turner au~
Soaitb. 197 .. , Smith and
others, 1975
r,~e~t~v, p~r8~nal c~.,
1975. Lahr and
t:achadoorian. 1975
Anon., 1974a; Beikman, 1974;
Turner and Smith, 1974
Csejtey, personal commun.,
1975: Lahr and
Kacharloorian, 1975
Type Relllarb
Thrust Evidence is stratigraphic'and
petrograpllic.
Thrust Evidence is stratigraphic.
Thrust Evidence is stratigraphic.
Thrust Evidence is stratigraphic.
Thrust & Evidence is stratigraphic.
Vertical
Strike Slip Right lateral with aome vertica:
d ispl acemen t.
Strike Slip Two faults; left lateral and
right lateral.
Strike Slip Evidence is topographic lineament;
inferred to be right lateral from
seismic data.
High Angle Displacement apparently vertical.
High Angle Displacement apparently vertical.
Thrust Evidence is apparently stratigraphic.
Strike Slip Existence is questioned by the authors.
Norwal Evidence is stratigraphic.
'I'lrust Alternate trace ~or number 4
Thrust Evidence is apparently stratigraphic.
Complex Evidence partly stratigraphic.
JfTracea of theae inferred faulta are shown in Figure 1 ~nd indicated by corresponding number.
8
PROCEDURES
Four kinds of information have been gathered in this preliminary
reconnaissance' (1) ground and aerial observations on the traces of
known and inferred faults, (2) visual observations of surficial deposits
and landforms made during helicopter overflights and locally
supplemented by ground observations, (3) a comparison of first order
leveling elevations conducted in 1922 and 1965, and (4) the location of
epicenters and hypocenters of seismic events in the general area.
Additionally, relevant reports in the literature have been consulted for
certain areas where our observations were incomplete due to inclement
weather and lack of time.
Ground and aerial observations from a helicopter were intended to
seek or confirm stratigraphic evidence for faults in the general area
and to seek topograpic and geomorphic evidence for recent faulting along
the mapped and inferred traces. These fault traces were obtained from
the available literature and unpublished reports (Csejtey and others,
1978 and Appendix C; Anon., 1974a; Gedney and Shapiro, 1975; Turner and
others. ~1974; Beikman, 1974; Turner and Smith, 1974; Smith and others,
1975; Lahr and Kachadoorian, 1975).
Visual observations during helicopter overflights involved
searching for scarps, topographic lineations, and offsets of landforms
that might be the result of faulting--particularly active faulting-The
criteria required to establish active faulting and recent movements
were: (1) offsets of glacial landforms, (2) offsets of other landforms
such as stream courses, (3) fresh scarps that were devoid of vegetation.
and (4) superposition of landforms over preexisting ones. A partial
9
list of the kinds of scarps and landforms that one might expect to
observe are listed in Table 2.
First order leveling elevation data were obtained from literature
supplied by Thomas Taylor, Topographic Division, U.S. Geological Survey,
Anchorage, Alaska.
The section on Seismic Activity was written by John Lahr and
Christopher Stephens, Center for Earthquake Studies, U.S. Geological
Survey, Menlo Park, California. John Lahr made his unpublished data
available to us.
Our criteria for designating a fault as active were constrained by
the local geology. Much of the area around the Devils Canyon and Watana
dam sites is mantled by late Wisconsin (8,000 to 12,000 y. ago) glacial
sediments. In such cases our definition of an active fault necessarily
is one that has moved within the last 8,000 to 12,000 years. In areas
underlain by bedrock, a fault would be considered active if there were
fresh scarps. Most inferred fault traces were locally mantled by late
Wisconsin and younger surficial deposits.
10
Table 2. Partial list of scarps and landforms that maybe found in a
search for active faults.
Primary
Volcanoes, flow fronts
Rock structures
JOint scarps (mass wasting, rock terraces, shear zones, folds,
foliations, etc·
Glacial features
Moraines (lateral. end, ground), eskers, kames, kettles.
lee contact features (scours, channels, U-shaped valleys, rock
terraces, roches mountonnee, etc.)
River
Bars, terraces, meander scars, valleys
Lake
Wave cut cliffs, bars, deltas, thaw scarps
Other unconsolidated deposits
Soil creep scarps, solifluction lobes, gravity slumps
Rock flow
Landslides, avalanches, rock glaciers
Tectonic
Fault scarps, sag features, offset drainage, etc.
Wind
Sand dunes
11
Ground and aerial observations along traces of known
and inferred faults
During this part of our reconnaissance we found no evidence for
active faulting that could be unequivocally related to the inferred or
actual faults in the general area. Each of the faults is discussed
below by their corresponding number in Table 1.
1. Zone of intense shearing. The zone of intense shearing was
examined on the ground near the Talkeetna River (T28N, R5E, S34,
NW 1/4). At this locality, cataclastically deformed Jurassic
granodiorite was observed to be in contact with late Paleozoic
metavolcanics rocks (unit Pzv, Appendix C) along an intense zone of
shearing. The contact or faulted zone between these two units was
oxidized. Thus, we concur with the existence of this shear zone as
mapped by Csejtey and others (1978).
No evidence for active faulting was observed on the ground. Near
the Talkeetna River, the flat top of the mountain was not vertically
offset where it was intersected by the shear zone. In addition,
observations during an overflight of the shear zone a few miles to the
southwest across the Talkeetna River and to the northwest along Tsisi
Creek to ROsina Creek and then to VABM Sumartidason yielded no evidence
of fresh scarps and drainage offsets. Stratigraphic evidence indicates
no movement has occurred since early Tertiary (Csejtey and others, 1978;
Appendix C).
2. Talkeetna Thrust. This thrust fault is inferred to be
concealed throughout almost all of its length. It is exposed along its
12
southwest trace (T27N, RIW, S6) where late Paleozoic metavolcanic rocks
(unit Pzv, Appendix C) form the hanging wall and phyllites and schists
(unit Kag, Appendix C) form the footwall. Unfaulted Tertiary volcanics
overlie the thrust (T28N, RIW). The fault and Tertiary volcanics as
mapped by Csejtey and others (1978) appear to be correct.
No evidence for scarps or active faulting along the inferred trace
from Prairie Creek. by Fog Lakes, and along Watana Creek were found by
us· Tertiary (Oligocene?) sediments in Watana Creek are gently tilted
and possibly faulted, but not recently.
3. Near Watana Creek. This thrust is well exposed (T33N, T22S,
RlW) and. where we examined it, Triassic metavolcanic rocks (unit TRv,
Appendix C) make up the hanging wall and Jurassic sediments (unit Js,
Appendix C) constitute the footwall. Near the fault trace, slickensided
Jurassic sediments are abundant. We agree with both the existence and
location of this fault as mapped by Csejtey and others (1978). Aerial
reconnaissance suggests the fault continues into the Healy Quadrangle as
indicated in Figure 1.
We found no evidence for active faulting at the locality examined
or along the fault trace to the northeast in the Healy Quadrangle.
4. Near Portage Creek. This thrust is well exposed along its
mapped length (T33N, R9W, RBW) and Triassic metabasalts and slates (unit
lRvs, Appendix C) are found to the north of the fault trace while
Cretaceous phyllites (unit Keg, Appendix C) are found to the south of
the trace. Unfaulted Tertiary volcanics and sediments overlie the
thrust to the east (T22S, R7W, R6W) and the thrust is terminated by
intrusion of Tertiary granodiorite to the west (T33N, RIE, SI8).
13
We found no evidence of active faulting along this trace and agree
that movement occurred before the early Tertiary (Csejtey and others,
1978).
5. Chulitna River. Time and inclement weather did not permit
adequate reconnaissance of this area but stratigraphic evidence shows a
variety of faults are present (Csejtey and others, 1978). Existing maps
indicate there is no active to recent faulting (Csejtey and others,
1978), Appendix C; Reed and Nelson, 1977). First order leveling
elevations were measured across the Chulitna River; the results of these
measurements are discussed later in this report.
6. North of VABM Sheep-Ground observations were not made by us.
Evidence for strike slip and vertical movement is represented by offset
of contacts between Tertiary granodiorites and older Cretaceous and
Paleozoic rocks (Csejtey and others, 1978).
During overfl ights along the trace of the fault, no evidence for
active faulting was found either over the wooded areas or along the
Talkeetna River.
7. West of VABM Sheep. Ground observations were not made by us.
Evidence for these faults is similar to that in 6 above. During
overflights along the traces of these faults, no evidence for active
faulting was found.
8. Susitna fault. The trace of this inferred fault passes from
the vicinity of Stephan Lake, along Deadman Creek to Butte Lake in the
Healy Quadrangle, and then across the west fork of the Susitna River
(Anon., 1974a). Evidence for this fault is primarily geomorphic, and
comprises a prominent linear on LANDSAT imagery (Gedney and Shapiro,
14
1975). Right lateral displacement has been postulated on the basis of
seismic evidence (Gedney and Shapiro, 1975). In contrast to Gedney and
Shapiro (1975), we find no compelling evidence for this fault in the
seismic data reported by them or available to us (see Appendix D). This
position is based on two factors. First, plots of our data and their
data do not show a striking correlation, if any, of epicenters with the
inferred trace of the fault. Second, the data are not complete enough
or precise enough to be used in this way beca~se the coverage of the
seismic net is inadequate for precise determination of epicenter and
hypocenter locations in the Susitna fault area. Additional seismic
stations could resolve the problem-
Stratigraphic evidence for this fault is weak to non-existent. The
geologic map of Turner and Smith (1974) indicates stratigraphic
evidence which is contradicted by Csejtey and others (1978). Tertiary
granodiorites and their border phases (unit Tsmg or migmatized rocks,
Appendix C) lie along the trace of the fault. Tertiary volcanic rocks
(unit Tv, Appendix C) occur at relatively low altitudes in Fog Creek
(T31N, R4E, R5E) and may be down-faulted. Lack of time prevented us
from making detailed studies of the volcanic rocks in Fog Creek.
Overflights along the inferred trace of this inferred fault
indicate that active faulting has not occurred along the trace.
Evidence for scarps and horizontal offsets are absent from Stephan Lake
northeast to a point across the Susitna River. Numerous fresh scarps
occur along lower Tsusena Creek and upper Deadman Creek to Butte Lake.
Fresh scarps and horizontal offsets are absent northeast of Butte Lake
where late Wisconsin re-advance (8,000 y. ago) glacial ground moraines
15
are present. The fresh scarps observed are believed to be due to
landsliding, slumping. solifluction, and stream erosion. Orientation of
the scarps and the localized hummocky topography at the edge of Tsusena
Creek near Watana the damsite (T32N, R5E, 521, 28, 29) are consistent
with a landslide. In upper Deadman Creek, fresh scarps have a variety
of orientations but they tend to face in southerly or in a downslope
direction. The traces of the scarps are commonly arcuate and a
kilometer (about 0.6 of a mile) or less in length. For these reasons,
we believe these scarps are the result of recent slumping, solifluction
and Boil creep. It is noteworthy that fresh scarps are absent in the
moraines northeast of Butte Lake. If these scarps were interpreted to
result from faulting, it would follow that the faulting was pre-moraine
(older than about 8,000 yrs and younger than 12,000 yrs). Other fresh
scarps on Deadman Creek are clearly meander scars.
In summary, we find no conclusive evidence for a fault or active
faulting along the inferred trace of the Susitna fault but rather
landsliding, slumping, solifluction, and soil creep. The production of
the fresh scarps may be partly related to general seismic activity in
the area, however.
9. Near Clarence Lake. The evidence for this inferred fault is
apparently stratigraphic (Turner and Smith, 1974), but no such
stratigraphic evidence was found by Csejtey and others. (1978;
Appendix C). Jurassic amphibolites (unit Jam, Appendix C) occur on both
sides of the inferred fault trace but there is a change in metamorphic
grade in zones parallel to it (Csejtey, personal comm., 1978). A few
scarps occur along the hillsides near the trace but these are best
16
attributed to solifluction and slumping.
10. Near VABM Windus. This fault runs parallel to the Susitna
River and passes to the south of VABM Windus. Here again, Turner and
Smith (1974) report stratigraphic evidence for it whereas Csejtey and
others (1978) do not report evidence for the fault. Jurassic
amphibolites (unit Jam, Appendix C) occur on both sides of the inferred
trace over nearly its entire length.
We found no evidence for active faults along the trace of this
inferred fault. The eastern part of the trace transects glacial ground
moraines and eskers. No vertical or horizontal offsets of the
associated landforms were observed. Fresh scarps with 3 to 4.6 m (10 to
15 ft) of relief are particularly abundant near the trace in the
vicinity of VABM Windus. Traces of these fresh scarps parallel the
local elevation contours and a few occur on the northeast slopes of the
Windus hill. This, combined with large amounts of surface and spring
water runoff observed during the overflight, suggest that the scarps are
due to slumping, solifluction, and soil creep. Tilted trees south of
the scarp suggest movement of surface materials occurred within the last
40 to 50 years.
11. North of VABMs Grebe and Mt. Watana. This inferred fault
transects Paleozoic rocks (unit Pzv, Appendix C) north of VABMs Grebe
and Mt. Watana, crosses the Susitna River, and then more or less
parallels the contact between the Paleozoic rocks (unit Pzv) and
Triassic metavolcanics (DV, Appendix C). Stratigraphic evidence for
this fault is generally lacking, although the contact between the
Paleozoic rocks and Triassic metavolcanics might be inferred to be a
17
fault. Csejtey and others (1978) do not report a fault along the
inferred trace. When we checked this fault on the ground, we found no
stratigraphic or geomorphic evidence for it.
During the overflight along the trace of the inferred fault, fresh
scarps and horizontal offsets of glacial features (moraines, eskers,
etc.) and other surficial deposits were not observed. Thus, active
faulting has not occurred along the inferred trace after the glacial
features were formed.
12. East of VABM Sumartidason. The existence of this fault is
questioned by the authors (Anon., 1974a). The trace was not examined
during an overflight because it was unknown to us prior to the
reconnaissance.
13. Watana Creek. The trace of this fault generally coincides
with the inferred traces of the Talkeetna thrust (see 2 above) and the
"Near Watana Creek" (see 3 above) faults and has been inferred to have
vertical displacement (north-side up) (Anon_, 1974a; Turner and Smith,
1974). Stratigraphic evidence in support of this fault includes
Jurassic sediments (unit Js, Appendix C) in fault contact with Triassic
volcanics (unit TRv, Appendix C) and the occurrence of tilted Tertiary
sediments (unit Tsu, Appendix C; T32N, R7E) at low altitudes.
We found no evidence for active faulting along the trace of this
faul t.
14. Along Portage Creek. This fault trace was an alternate trace
to the eastern part of the thruat fault in 4 above (Csejtey, personal
comm., 1975). We found no evidence for active faulting along Portage
Creek.
18
15. North of Denali. Evidence for this fault is apparently
stratigraphic and its trace is truncated by intrusives (Cretaceous in
age?) (Anon .• 1974a; Turner and Smith, 1974). Both the mapping and
overflights in the general area indicate this fault is inactive.
16. Cretaceous to recent shearing. Time and inclement weather did
not permit adequate reconnaissance of this area which is the same area
as number 5 above. The reasons for inferring recent faulting are two
poorly exposed normal faults in the Chulitna River valley (Csejtey and
others, 1978). Csejtey (personal comm-, 1978) states that apparently
middle Tertiary or younger sediments have been displaced by the faults.
However, existing maps indicate there is no active to recent faulting
(Csejtey and others, 1978; Appendix C; Reed and Nelson. 1977).
As stated earlier, lack of time and inclement weather did not
permit us to investigate these faults thoroughly. Therefore, it is
unknown to us whether any active faulting has occurred along these
faults in the Chulitna valley. We attempt, however, to evaluate this
fault zone by studying first order leveling data. The results of first
order leveling surveys across the fault zone are discussed later.
19
Visual observations during helicopter flights
Within the study area, a number of geologic phenomena were observed
from the air which are relevant to the geologic problems related to dam
construction. The most important are: 1) very steeply dipping join~
sets and shear zones are common, 2) there are a significant number of
short fresh scarps, 3) landslides have occurred in the past and new ones
may occur in the future, 4) permafrost is present, at least locally, and
5) locally tills, alluvium, and Tertiary sediments with very low
cohesions occur at altitudes near and below the expected water level of
the Devils Canyon and Watana dam reservoirs.
1. Very steeply dipping joint sets and shear zones are common (see
for example Kachadoorian, 1974). Although these joint sets and shear
zones do not necessarily pose dam construction problems, their
implications to active tectonic movements and 1ands1iding are important.
In regard to active tectonic movements, it seems conceivable that minor
vertical and horizontal adjustments during tectonic activity could occur
along them without producing long continuous faults but rather short
scarps with small displacement (4.6 m, 15 ft). Thus, uplift and
deformation could be accomplished by small vertical and horizontal
movements along a myriad of joints. In some places, joint sets are so
numerous that the Tertiary granodiorites superficially resemble columnar
basalt (such as in T31N, R3E, S17). In many places both fresh scarps
and graben-like structures appear to be controlled by these joints while
in other places, fresh scarps parallel the shear zones.
In addition to providing planes of weakness for minor tectonic
movements, the joint sets will also partly control landsliding and rock
20
falls.
2. Fresh scarps are conspicuously abundant in the general area.
None of these can be unequivocally ascribed to active faulting but local
minor vertical adjustments of the order of 1.5 to 3 m (5 to 10 ft)
cannot be excluded for some of them. Others are best attributed to
slumping, solifluction, soil creep, and 1ands1ip.
a. Solifluction and slump scarps. Fresh scarps near VABM Wind us
are a good example of scarps produced by slumping and solifluction.
They are fresh and unvegetated with reliefs to about 4.6 m (15 ft).
They appear to be the result of recent movement by solifluction because
segmented traces of scarps to the south of VABM Windus trend parallel to
the topographic contours, a few of them occur on the northeast side of
the Windus hill, and trees downslope have a variety of orientations.
Judging from the tilted trees, movement has occurred within the last 40
to 50 years. Numerous springs were observed during the overflight and
polygons are present 2.5 km (1.5 miles) west of VABM Windus.
Additional places where the fresh scarps can be attributed to
solifluction and slumping are listed in Table 3.
b. Other scarps. A variety of other types of scarps are present
(Table 4) and some of these need special discussion. In general, fresh
appearing scarps face in southerly directions. A group of such scarps
near the Watana damsite deserve special comment because detailed
geologic studies and aerial observations reveal nearly vertical shear
zones that trend northwest (Glen Greely, Corps of Engineers, personal
commun., 1978) and the traces of nearby fresh scarps also trend in
northwesterly directions. These scarps appear to be of two types which
are unrelated to the shear zones. The first type (item 2, Table 4) is
21
Table 3. Location of selected examples of scarps in the
Taleetna Mountains Quadrangle.
Number Township Range Section
1-C-l T 30 N R 11 E 1, 2, 11, 13, 14
2. VABM Windus C-2 T 31 N R 10 E 26 through 30
33 through 36
3. C-2 T 30 N R 10 E 22
4. C-2 T 30 N R 9 E 15, 16
5. C-2 T 30 N R 8 E 3, 9, 15, 14
6. C-2 T 29 N R 1 E 19, 20, 21,. 28, 29
7. D-2 T 33 N R 10 E 22
8. D-3 T 22 S R 4 W 21, 28, 29, 31, 33
9. D-3 T 33 N R 5 E 19, 20, 25, 26, 27, 34
10. Watana Site D-4 T 32 N R 5 E 21
11-D-4 T 33 N R 4 E 28, 29, 31
12. D-4 T 33 N R 3 E 27, 28, 34, 36
13. D-4 T 32 N R 4 E 29, 32
22
Table 4. Selected examples of landforms with steep
scarp-like surfaces.
Feature
Fresh appearing
L Meander scars/cut banks
2. Meander scars/thaw lake
shores
3. Thaw lake shores
4. A1 tiplanation scarps
S. Landslide
6. Eskers
7. Moraines
8. Kames and Kettles
Old appearing
9. Glac ial Scour
10. Old River channels
LocationY
(D-3) T33N R6E 519
(D-3) T32N R5E 514
(C-2) T30N R9E S 7,8
(C-5) T29N R1E 521
(D-4) T32N RSE 529,528
(C-l) T30N RIlE, R12E,
524,2S
(C-1) T30N R12E 59,16,17
(C-3) T30N RSE 524
(C-3) T30N R7E 519
(C-4) T30N RSE 530
(D-2) T 31N R8E 59,16,17
(C-4) T30N RSE 55,8,17
(D-3) T225 RSW 536
(D-3 ) T225 R4W 530
(C-3) T30N R8E 85,6,7,8
Healy Quad. T205 R1W
54,S,6
(C-4) T30N R2E 524
(C-1) T30N RIlE 523
(D-4) T31N R3E 57,8,17
(C-2) T31N R9E 52S,36
(C-2) T30N R10E 511
(D-S) T32N R2E 533
Contents
In Deadman Creek
Near Watana damsite
Near Watana damsite
Close to 5usitna River
Lateral
End
Lateral
JlLetter designations refer to 1:63,360 scale topographic maps of
the Talkeetna Mountains.
23
believed to be due to the combined effects of ancient streams and thaw
lakes. Excavation of the materials in one of the scarps revealed it is
underlain by bedded, pebbly to cobbly fine-to medium-grained sands
deposited by streams. The complex array of the scarps suggest that th~y
are former meander scars. Additionally, many of the scarps partly
surround thaw lakes and bouldery beds of former thaw lakes. Although
fresh scarps in the area tend to face southwest, some vegetated ones
that face in north to northeast directions are present. Thus, we
attribute this type of scarp to the combined action of ancient lakes and
streams and to recent thawing and freezing.
The second type (item 5, Table 4) is classified as a landslide
because the hummocky surface of southwest facing scarps and benches are
confined to a small area and are consistent with soil movement toward
the southwest. The landslide is not related to the shear zones because
sediments comprise the material of the slide and no bedrock occurs in
it. Freezing and thawing may have been the major cause of movments
producing these scarps and benches but we have classed them as
landslides because of the relatively large amount of movement.
24
The origin of some fresh scarps is unclear and the relatively large
abundance of scarps might be partly the result of mild tectonic activity
and seismic shaking. Many scarps, both fresh and old, are aligned
parallel to local joint directions (C-5, T31N, R1E, S34, 35; and C-5,
T31N, R2E, S33) and could represent the results of local tectonic
adjustments. The fresh scarps associated with joint sets and slumping
are clearly recent as shown by their lack of vegetation and tilted
trees. Seismic waves may be partly responsible for these recent
movements.
2. Older Scarps. Older vegetated and lichen covered scarps are
similar to the fresh scarps, but here, two additional types have been
observed:. graben-like structures in bedrock and old river channels.
The graben-like structures (item 10, Table 4) are generally short in
length (a fraction of a km) and shallow. Their lengths trend westerly
which is the general direction of glacial movement in the area. Because
of the short length, orientation, and graben-like form, we attribute
them to glacial plucking and scouring. Old river channels also occur
(item 9, Table 4). These old channels are arcuate graben-like landforms
subparallel to the present course of the Susitna River.
3. Landslides. Although not particularly abundant throughout the
Devils Canyon and Watana area, landslides have occurred in the past and
new ones may occur in the future. We noted several large landslides
along the Susitna River in the proposed Devils Canyon and Watana
reservoir sites. The evidence for old landslides is straightforward.
Those composed chiefly of rock occur as isolated blocks (or hills)
downslope of arcuate SCars with about the same aerial dimensions as the
25
block. Two such slides were observed and are listed in Table 5 (items
1 and 2). Landslides in unconsolidated sediments, such as alluvium and
glacial till, form hummocky surfaces of scarps, terraces, and ridges
(item 3, Table 5).
Identification of potential landslides using geomorphic evidence
from overflights is problematical and the number of potential landslides
listed in Table 5 could either be an overestimate or an underestimate of
the potential landslides in the Devils Canyon and Watana reservoir
areas. We have, however, listed them to indicate the potential for
future landsliding in the area. Also, those listed do not include
possible landsliding of bedrock and unconsolidated sediments once they
become saturated with water during reservoir filling.
It was not within our charter to map in detail the abutments of the
proposed Watana damsite as Kachadoorian (1974) did at the proposed
Devils Canyon damsite. Therefore, the abutments of the Watana site
should be thoroughly examined for possible potential landslides.
4. Permafrost. Permanently frozen ground or permafrost is present
in the proposed dam and reservoir areas. During our overflights
numerous ice wedge polygons were noted, some of which are listed in
Table 6. We also noted slumping of surficial· debris on permafrost in
the Susitna River canyon at about altitude 580 m (1,900 ft) (T31N, R4E,
S21), about 11 km (7 miles) downstream of the proposed Watana damsite.
Permafrost was also reported in the surficial deposits during drilling
at the proposed Vee Canyon damsite (Anon., 1962) about 65 km (40 miles)
upstream of the Watana site and in unconsolidated sediments and bedrock
of the left abutment of the proposed Watana damsite (Corps of Engineers,
personal commun., 1978).
26
Table 5. Locations of old landslides and potential landslides.
LocationJ'
Old Landslides
.1. (0-3) T32N R6E 5-28 (5E 1/4)
2. (0-4) T32N R4E 5-33 (NE 1/2)
& S34 (NW 1/4)
3. (0-4) T32N R5E 5-28 (NW 1/4)
& 5-29 (NE 1/4)
Potential Landslides
4. (0-3) T32N R6E S-32 (N 1/2)
5. (0-4) T31N R2E 5-12 (E 1/2)
6. (C-2) T31N R9E 5-26 (5 1/2)
Comments
Block of rocks is several
hundred feet across.
Block of rocks is several
hundred feet across.
North of Watana damsite,
slide material is alluvium
and fill.
Weakly developed scarp at
549 m (1800 ft).
Weakly developed scarp at
366 m (1200 ft).
Top of mass at 610 m
(2000 ft).
YLetter designations refer to 1:63,360 scale topographic maps of the
Talkeetna Mountains Quadrangle.
27
Table 6. Locations where patterned ground was observed.
LocationJl
(D-4) T32N R5E S28
(C-2) T31N RI0E S28,33
(C-2 ) T30N R9E S10,15
(C-4 ) T30N R5E S 7.8
(C-4 ) T29N R4E S2
(C-5) T30N RIW S3
(C-5) T30N RIE S19
~Letter designations refer to 1:63,360 scale topographic maps of the
Talkeetna Mountains Quadrangle.
28
In order to evaluate the permafrost-related geotechnical problems
in the proposed Devils Canyon and Watana dam and reservoir sites, a
detailed study of the nature, character, and distribution of permafrost
should be made. Of particular importance is the permafrost that
underlies the left abutment of the proposed Watana damsite.
5. Tjll. alluvium. and Tertiary sediments. Locally, poorly
consolidated tills, alluvium, and Tertiary sediments occur at water
levels that are lower than the planned altitudes of the filled
reservoirs of the two dams (Devils Canyon: 442 m (1,450 ft); Watana 666
m (2,185 ft). Wetting of the materials and thawing of ice in them will
cause weakening of the materials and may cause subsequent slumping, mud
slides, and other mass movements. This problem is more probable for the
Watana reservoir than it is for the Devils Canyon reservoir. For the
Devils Canyon reservoir, the frequency of outcrops of rock below
altitudes of 442 m (1,450 ft) is striking along the entire length of the
Susitna River valley that would be occupied by the reservoir. Tills
appear to occur above about 610 m (2,000 ft) but some alluvial fans
would be innundated.
For the Watana reservoir, the occurrence of till and sediments
begins within 3 km (about 2 miles) upstream of the proposed damsite.
Here, tills and sediments overlie bedrock and the contact between them
is near 579 to 610 m (1,900 to 2,000 ft). The amount of bedrock exposed
along the Susitna River upstream of the planned damsite is impressive
but at altitudes near 610 m (2,000 ft) and higher, tills and other
sediments are conspicuous. Eskers occur upstream at an altitude of
549 m (1,800 ft). Alluvium and talus are also common below 671 m
(2,200 ft) along the river.
29
Both tills and Tertiary fluviatile sediments that would be
inundated by the reservoir occur in Watana Creek. Some of the
fluviatile Tertiary sediments are clays which, when wetted, become very
weak and may even disaggregate.
30
First Order Leveling Observations
The results of first order leveling are included here because
(1) the traverse passes across the zone of Cretaceous to recent shearing'
and faulting in the Chulitna River valley (Table 1, number 16) and
across the Denali fault (Lahr and Kachadoorian, 1975), and (2) because
the l~veling was accomplished before and after the Alaskan earthquake of
1964. Comparisons of the first order altitudes, mea,sured in the summers
of 1922 and 1965 along The Alaska Railway from Sunshine to McKinley Park
(Rappleye, 1930; Anon., 1973) reveal that differences in altitudes of
bench marks measured in the two surveys cannot be attributed to faults
with large displacements. These altitudes, which are tabulated in Table
7, are everywhere within 0.21 m (0.7 ft) of one another. According to
Thomas Taylor of the Topographic Division of the Geological Survey in
Anchorage. Alaska, differences in excess of 0.30 m (1 ft) would probably
exceed the uncertainties in altitude changes of some benchmarks due to
frost heaving. A tentative analysis of the data indicate, however, that
there may be a systematic change in altitudes between the two surveys.
The data indicate that there appears to be some tilting, 'of the order of
a foot (0.3 m) with the south side down between Sunshine on the south to
Yanert to the north. Because we do not know which of the benchmarks are
in unconsolidated sediment and subject to frost heaving and which are
not, we do not believe an analysis of the data can permit us to state
that there has been any active faulting between 1922 and 1965.
Because of the differences in altitudes detected during the first-
order leveling, we believe the Vertical Angle Bench Marks should be
remeasured in order to detect possible displacements with the Devils
Canyon and Watana damsite areas subsequent to the initial surveys.
31
Table 7. First-Order leveling from the vicinity of Sunshine to McKinley Park.
Altitude (in feet)Y
Station Designation 1922 1965 Difference
J-2 Sunshine 285.895 285.219 -0.676
M-2 Talkeetna 346.259 345.675 -0.584
0-2 Chase 411.239 410.718 -0.521
U-2 Curry 543.358 543.004 -0.354
V-2 Sherman 587.200 586.908 -0.292
X-2 Gold Creek 691.764 691.610 -0.154
Z-2 Canyon 856.173 856.015 -0.158
A-3 Canyon 1044.555 1044.417 -0.138
E-3 Hurricane Gulch 1629.974 1629.951 -0.023
F-3 Honolulu 1495.322 1495.381 +0.059
K-3 Colorado 2063.090 2063.247 +0.157
L-3 Broadpass 2059.569 2059.720 +0.151
P-3 Cantwell 2246.373 2246.547 +0.174
S-3 Windy 2076.036 2076.285 +0.249
T-3 Windy 1996.873 1996.974 +0.101
U-3 Carlo 1956.367 1956.627 +0.260
V-3 Yanert 1950.357 1950.678 +0.321
W-3 Yanert 1950.574 1950.905 +0.331
Y-3 McKinley Park 171 7.201 171 7.382 +0.181
~Altttude reported in feet because First-Orderleveling recorded in feet.
The conversion factor is 0.3048 meters/foot.
-indicates decrease in altitude from 1922 to 1965.
+ indicates increase in altitude from 1922 to 1965.
32
Additional Observations
Although it may not be within our charter, we would like to comment
about the sediment load in the glacially fed Susitna River. Of
.
particular interest here is the rate at Which the Watana reservoir might
be filled by the suspended load and the bed load of the river. Our
estimates of the time to fill the reservoir using nominal values of the
rates and suspended load (Anon., 1974b), are near one or two thousand
years. However, suspended and bed loads of glacially fed streams are
highly variable. Thus, we feel that there may be insufficient detailed
data to provide an adequate estimate of the lifetime of the dam and that
such data should be gathered and analyzed to insure that there is an
adequate lifetime for the Watana dam.
During our aerial and ground observations, we found no evidence for
recent volcanism. Scoriaceous rocks do occur in the Tertiary sediments
of Watana Creek but these are the result of heating by subsurface
burning of the lignite beds in the distant past.
Henry Moore noted evidence for icing on or near the left abutment
of the proposed Watana damsite. Such icing was verified by Glen Greely,
Corps of Engineers (personal comm., 1978). We do not know the source of
water for this icing. Therefore, we recommend that the left abutment be
thoroughly investigated to determine the source and location of the
water relative to the proposed dam.
We detected some lineaments in the active outwash plain of the West
Fork Glacier. These lineaments occur about 5 km (3 miles) south of the
present terminus of the glacier and are about 97 km (60 miles) northeast
of the proposed Watana damsite. The lineaments are interpreted to be
33
sand dikes that developed during seismic shaking from an earthquake.
The age of the sand dikes is unknown but they are considered to be
relatively young because they are well preserved and occur 1n the active
outwash plain of the West Fork Glacier. Lack of time did not permit ~s
to make an extensive investigation of the area to adequately determine
the extent and distribution of the sand dikes.
34
Seismic Activity
The Devils Canyon and Watana damsite area lies within a region
characterized by a high rate of seismic activity that is the result of
tectonic interaction between the Pacific and North American lithospheric
plates. The Pacific plate is being thrust to the northwest beneath the
North American plate (Lahr and Kachadoorian, 1975). The earthquakes
affecting this region are generally of three types: (1) shallow (depth
less than about 50 km) earthquakes (such as the 1964 Alaska earthquake)
which occur on the surface of contact between the Pacific and North
American plates to accommodate their relative motion; (2) shallow
earthquakes which occur within the North American plate (including
Alaska) in response to the stresses produced by interaction with the
Pacific plate; and (3) deeper earthquakes (depths from 50 to 200 km)
that occur within the portion of the Pacific plate that has been thrust
beneath Alaska. These latter earthquakes define a region called the
Benioff zone. Earthquakes which are occurring in the region of the
proposed damsites are of the types described in the last two categories,
although earthquakes of all three types are capable of producing strong
ground shaking at the proposed sites.
Lahr and Kachadoorian (1975) reviewed the seismic data available
from the U.S.G.S. (formerly N.O.A.A.) Earthquake Data File for the
period 1900 to February 1975. Using only the more reliable earthquake
locations, they showed that the depth of earthquakes in the region of
the proposed reservoirs range from less than 10 km to greater than
175 km. The depth to the Benioff zone directly beneath the proposed
damsites is about 50 km to 80 km. Distribution of epicenters of shallow
35
earthquakes, according to presently available data, is too scattered to
reliably associate them with individual faults.
For design purposes there are two questions of major importance.
First, are there potential active faults or other zones of weakness
beneath the proposed structures which could cause direct structural
damage during an earthquake? Second, what are the spatial, temporal,
and magnitude distributions of earthquakes in the region and as a
result, what accelerations will the proposed structures probably
experience during their lifetime?
The process of identifying active faults on the basis of earthquake
locations is limited by the accuracy to which the locations can be
determined. as well as by the smallest magnitude earthquake that can be
recorded. These two parameters are highly dependent upon the number and
distribution of seismograph stations used in determining a location. A
regional seismograph network did not exist in southern Alaska before
1967. Prior to that time, the accuracy of epicentral coordinates was
50 km or more, errors in depth were on the order of 100 km or more, and
the smallest magnitude events that had been detected were about 4 1/2 on
the Richter scale. Since 1967, routine locations for earthquakes as
small in magnitude as about 3 have been determined with accuracies of
10-15 km in epicenter and about 25 km in depth. Since 1971 the U.S.G.S.
has operated a network of seismic stations in southern Alaska. The
distribution of earthquake hypocenters and magnitudes detemined using
this network generally confirms the conclusions reached by Lahr and
Kachadoorian (1975). Recent U.S.G.S. data allow more precise resolution
of the depth to the top of the Benioff zone and of the extent of shallow
crustal activity. The distribution of the epicenters of the shallow
36
earthquakes does not show a strong correlation with mapped faults,
although the current accuracy to which these epicenters are determined
does not preclude the possibility that the earthquakes are occurring
along mapped or as yet unknown faults. To obtain the number of
accurately located earthquakes necessary to resolve this question it
will be necessary to establish a local network of seismic stations in
the r'egion of the proposed damsites.
The tectonics of the region are too poorly known at this time to
make a reliable prediction for the distribution of events that may
strongly shake the damsites. Certainly the Benioff zone activity will
continue as will the shallow regional activity. In addition, the Denali
fault, which lies less than 80 km north of the proposed damsites, is a
major strike-slip fault with geologic evidence for a 3 cm/yr average
Holocene slip. This fault could sustain a magnitude 8.0 event.
In addition to the naturally occurring earthquake activity in the
region, there is also the hazard that filling of a reservoir may trigger
potentially damaging earthquakes (as large as magnitude 6 or greater) in
the immediate vicinity of the damsites (Lahr and Kachadoorian, 1975).
Continuous monitoring by a local network of seismic stations in the
region beginning well in advance of filling the reservoirs would allow
the level of natural ambient seismicity to be determined. Unless the
natural level is well established, an important opportunity to study
this phenomena will be lost, and possibly unwarranted conclusions
concerning induced seismicity may be made in the future.
37
SUMMARY
Our geologic reconnaissance of the proposed Devils Canyon and
Watana damsites and reservoir areas, Susitna River, Alaska, did not
uncover evidence for recent or active faulting along any of the known
and inferred faults. Recent movement of surficial deposits has occurred
as the result of mass wasting processes that have produced scarps and
downslope movement of surficial debris. It is possible that some fresh
scarps may have been triggered or produced by seismic shaking and minor
displacements of bedrock along joints.
Lands1iding into the Susitna River has occurred in the past and
future 1ands1iding appears probable. Additionally, the occurrence of
poorly consolidated glacial debris, alluvium, and Tertiary sediments at
altitudes below the proposed reservoir water levels, especially at the
Watana Dam reservoir, may slump and slide into the reservoirs. Some of
these sediments contain permafrost and may be ice-rich which increases
the probability of slumping and sliding when they are thawed by the
water impounded behind the dams.
The proposed Devils Canyon and Watana dams are located in a region
of high seismicity. The tectonic framework of the region is not well
understood because of the lack of local seismic monitoring stations.
Our present knowledge of the region indicates that hypocenters of earthquakes
in the region of the proposed dams ranges in depth from less than 10 km
to greater than 175 km. We are unable at this time to reliably predict the
location and magnitude of future crustal earthquakes that could effect
the proposed structures.
38
RECOMMENDATIONS
The conclusions presented in this report are based on a
reconnaissance study of the proposed Devils Canyon and Watana dam and
reservoir sites, and, therefore, should be considered to be preliminary.
A thorough evaluation of the geotechnical problems of the proposed dam
and reservoir sites will require more data. It will be necessary to
(1) map the Healy, Alaska, Quadrangle, at a scale of 1:250,000, from the
Talkteena Mountains Quadrangle to the Denali Fault, about 80 km
(48 miles) north of the damsites, (2) map the proposed Devils Canyon and
Watana damsites at an appropriate scale to determine the bedrock
structure and distribution of unconsolidated sediments overlying the
bedrock, (3) map the reservoir sites at a scale of 1:63,360 in order to
(a) establish the type and distribution of unconsolidated sediments and
bedrock, (b) locate additional potential landslide areas, and
(c) determine the nature and distribution of permafrost, (4) initiate a
seismic monitoring program of the dam and reservoir areas, (5) continue
the active fault study, (6) redetermine the altitudes of the Vertical
Angle Benchmarks, and (7) collect detailed data on the suspended loads
and bed loads of the Susitna River in order to determine if the
reservoir filling rates are acceptable.
39
REFERENCES CITED
Anon., 1962, Engineering Geology of the Vee Canyon Damsite: Bureau of
Reclamation unpublished report 37, p.4, Appendices.
Anon., 1973a, Vertical Control Data: National Geodetic Survey,
U.S. Department of Commerce, National Oceanic and Atmospheric
Administration, National Ocean Survey.
Anon., 1974a, Annual Report 1973: Division of Geologic and
Geophysical Survey, Department of National Reserve, State of
Alaska, 59 p.
Anon., 1974b, Water Resources Data for Alaska, Part 1, Surface Water
Records, Part 2, Water Quality Records: U.S. Geological Survey,
299 p.
Beikman, Helen M., 1974, Preliminary Geologic Map of the Southeast
Quadrant of Alaska: U.S. Geological Survey Miscellaneous Field
Studies Map 612, 2 sheets.
Csejtey, B~la, Jr., Nelson, W. H., Jones, D. L., Siberling, N. J.,
Dean, R. M., Morris, M. S., Lamphere, M. A., Smith, J. G., and
Silberman, M. L., 1978, Reconnaissance Geologic Map and
Geochronology, Talkeetna Mountains Quadrangle, northern part of
Anchorage Quadrangle, and southwest corner of Healy Quadrangle,
Alaska: U.S. Geological Survey Open-file Report 78-558-A.
40
Gedney, Larry and Shapiro, Lewis, 1975, Structural Lineaments,
Seismicity, and Geology of the Talkeetna Mountains Area, Alaska:
Geophysical Institute, University of Alaska, Fairbanks, Alaska;
18 p., 5 plates. Report prepared for the U.S. Army Corps of
Engineers (N.A.S.A. Contract NAS 5-20803, NASA Grant NGL 02-001-
092 and U.S.G.S. Contract 14-08-0001-14857).
f~chadoorian, Reuben, 1974, Geology of the nevils Canyon damsite,
Alaska, U.S. Geological Survey Open-file Report 74-40, 17 p.
Lahr, John C. and Kachadoorian, Reuben, 1975, Preliminary geologic and
seismic evaluation of the proposed Devils Canyon and Watana
Reservoir areas, Susitna River. Alaska: Informal report to the
U.S. Army Corps of Engineers, 24 p.
PAwA, Troy L., 1974, Quaternary geology of Alaska: U.S. Geological
Survey Professional Paper 835, 145 p., 3 plates.
Rappleye, Howard S., 1930, First-order leveling in Alaska: U.S.
Department of Commerce, Coast and Geodetic Survey Special
Publication 169, p.
Smith, Thomas E., Bundtzan, Thomas K., and Trible, Thomas C., 1975,
Stratabound copper-gold occurrence, Northern Talkeetna Mountains,
Alaska: Alaska Division of Geologic and Geophysical Surveys,
Miscellaneous Paper 3, 7 p.
Reed, B. L. and Nelson, S. W., 1977, Geologic map of the Talkeetna
Quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field
Studies Map MF-870-A.
41
Turner, D. L. and Smith, T. E., 1974, Geochronology and generalized
geology of the Central Alaska Range, Clearwater Mountain, and
Northern Talkeetna Mountains: Alaska Division of Geological and
Geophysical Surveys, Open-file Report 72, 11 p., 1 map.
Turner, D. L., Smith, T. E., and Forbes, R. B., 1974, Geochronology
and offset along the Denali Fault Syst (abs.), in Abstracts with
programs 70th Annual Meeting, Cordillerian Section, Geological
Society of America, v. 6, no. 3, p. 268-269.
42
EXHIBIT 0-3
Earthquake Assessment of the Susitna Project
EARTHQUAKE ASSESSMENT AT THE
SUSITNA PROJECT, ALASKA
by
E. L. Krinitzsky
Geotechnical Laboratory
U. S. Army Engineer Waterways Experiment Station
Vicksburg, Mississippi 39180
10 November 1978
CONTENTS
PART I: INTRODUCTION . . • • • . , . . • . .
PART 11: PROCEDURE;S FOR ASSIGNING EARTHQUAKE MOTIONS
PART III: EARTHQUAKE EVALUATION
PAR'I' IV: INTERPRE'l'ED PEAK MOTIONS
An Earthquake Originating at the Denali Fault
A Local Floating Earthquake with Fault Breakage
that does not Occur at the Damsites
An Earthquake at the Damsites
PART V: ASSOCIATED MOTIONS . . . .
Induced Seismicity from Reservoir Loading
Water Waves from Earthquake Shaking
Earthquake-Induced Landslides .....
Tectonic Strain and Overstressed Conditions in Rock
PART VI: CONCLUSIONS
PAWl' VII: REFERENCES.
nGURES
1
2
11
17
19
21
PART I: INTRODUCTION
1. The following sections of this report will assess the possible
occurrence of earthquakes at the dam sites and the motions that are likely
to be associated with earthquake activity.
2. The assessments are preliminary since the investigations on which
they are based were done on a reconnaissance level and are necessarily
incomplete.
1
PART II: PROCEDURES FOR ASSIGNING EARTHQUAKE ~OTIONS
J. Earthquake,; are associated with faults. Tectonism causes
differential movements in the earth's crust. The rock is subjected to
strain and the buildup of stresses. Relief then may come abruptly as
slippaGe ulong a fault. When occurs, the adjacent rocks may re-
bou.nd elastically with vibratory motions. The shaking consti-
tutes tne earthquake.
1+. Earthquakes may be asswned to result from movement exis-
ting faults rather than from rock rupture that produces :lew faults.
While new faults cannot be eliminated entirely, information extending
through geological time and the ubiquitous occurrence of faults
that for practical purposes earthquakes can be considered to be associated
with along existing faults.
). Since faults are found everywhere, the engineering is
faced with the problem of determining which faults are active, or subject
to movement, and which are inactive. Of faults that are active, movement
can be occurring steadily and slowly by creep and without earthquakes.
The engineering geologist must determine which are the "capable" faults,
capable meaning that they can generate earthquakes.
6. Corps ot' Engineers criteria for a capable fault (see ER 1110-2-
1806 of 30 April 19'7'7) are as rollows:
a. Movement at or near the ground surface at least once within
the past 35,000 years.
b. Macro-seismicity (3.5 magnitude or greater) instrumentally
determined with records of sufficient precision to demonstrate a direct
relationship with the fault.
c. A structural relationship to a capable fault such that move-
ment on one fault could be reasonably expected to cause movement on the
other.
7. 'I'he geological investigation of faults uses all of the techni-
ques that are available: aerial and satellite imagery, inspection from
2
overflights, low sun angle photography, reviews of regional and local
geology, geophysical surveys, details of geomorphology and relevant in-
formation from the seismic history.
8. For a careful investigation of a construction site, the field
evidence may be checked further by borings, geophysical profiles, trenches,
and stripping.
9. Monitoring programs for corroborative evidence may include strain
gages, leveling points, geodimeter readings, and microearthquake monitoring.
10. Often, it is desirable to make a critical restudy of historic
earthquake events using the original documentation in newspapers, diaries,
etc. Relocation of epicenters may result and they may accord better with
geologic information and possibly with specific faults. The maximum
intensities of events may be subject to revision also.
11. The direction of future movement on an active fault is predict-
able since the past is a very good guide to the future. However, second-
ary and tertiary faults may have motions that are different from that of
a major fault. Where such data are available, one can readily guard
against the effects of fault movement under a structure simply by moving
the structure.
12. Once a fault is identified as capable of generating earthquakes,
and its dimensions are ascertained, the next factor to determine is the
worst earthquake that the fault will produce. Toward this end, there are
a number of relationships and assumptions that involve the size of fault-
ing, or dimension of maximum movement, with the maximum earthquake that
might reasonably be expected. The data are best for major strike-slip
faults. The dispersion of data is much greater for normal and thrust
faults. However, the variants in field conditions can be enveloped with
a reasonable degree of dependability. Relationships between fault length
and earthquake magnitude have been summarized for Corps use in a report
by Slemmons (1977).
13. Though major active faults and major centers of earthquakes can
be accounted for, small faults may be missed in any investigation so that
often a floating earthquake of appropriate size may be provided in order
to account for them.
3
14. The earthquakes that are thus determined can be expressed in
terms of magnitude* but they need also to be expressed in Modified
Mercalli (MIvI) interisity in order to relate to historic earthquake effects.
The 1\11\1 scale is shown in Table 1.
Table 1
MODIFIED MERCALLI INTENSITY SCALE OF 1931
(Abridged)
1. Not felt except by a very few under especially favorable
circumstances.
II. Felt only by a few persons at rest, especially on upper
floors of buildings. Delicately suspended objects may
swing.
III. Felt quite noticeably indoors, especially on upper floors
of buildings, but many people do not recognize it as an
earthquake. Standing motor cars may rock slightly.
Vibration like passing of truck. Duration estimated.
IV. During the day felt indoors by many, outdoors by few. At
night some awakened. Dishes, windows, doors disturbed;
walls made cracking sound. Sensation like heavy truck
striking building. Standing motor cars rocked noticeably.
V. Felt by nearly everyone; many awakened. Some dishes, win-
dows, etc., broken; a few instances of cracked plaster;
unstable objects overturned. Disturbance of' trees, poles
and other tall objects sometimes noticed. Pendulum clocks
may stop.
VI. Felt by all; many frightened and run outdoors. Some heavy
furniture moved; a few instances of fallen plaster or
damaged chimneys. Damage slight.
* Magnitude (Richter scale) is calculated from a standard earthquake,
one which provides a maximum trace amplitude of one micrometer on a
Wood-Anderson torsion seismograph at a distance of 100 km. Magnitude
is the 10glO of the ratio of the amplitude of any earthquake at the
standard distance to that of the standard earthquake. Though the
scale is open-ended, the largest earthquake may be at a limit of mag-
nitude 8.7. Each full numeral step in the scale (2 to 3, for example)
represents an energy increase of about times.
4
VII. ~yerybody runs outdoors. Damage negligible in buildings of
good design and construction; slight to moderate in well-
built ordinary structures; considerable in poorly built or
badly designed structures; some chimneys broken. Noticed
by persons driving motor cars.
VIII. Damage slight in specially designed structures; considerable
in ordinary substantial buildings with partial collapse; .
great in poorly built structures. Panel walls thrown out
of frame structures. Fall of chimneys, factory stacks,
columns, monuments, walls. Heavy furniture overturned.
Sand and mud ejected in small amounts. Changes in well
water. Disturbed persons driving motor cars.
IX. Damage considerable in specially designed structures; well-
designed frame structures thrown out of plumb; great in sub-
stantial buildings, with partial collapse. Buildings
shifted off foundations. Ground cracked conspicuously.
Underground pipes broken.
X. Some well-built wooden structures destroyed; most masonry
and frame structures destroyed with foundations; ground
badly cracked. Rails bent. Landslides considerable from
river banks and steep slopes. Shifted sand and mud.
Water splashed (slopped) over banks.
XI. Few, if any (masonry), structures remain standing. Bridges
destroyed. Broad fissures in ground. Underground pipe
lines completely out of service. Earth slumps and land
slips in soft ground. Rails bent greatly.
XII. Damage total. Waves seen on ground surfaces. Lines of
sight and level distorted. Objects thrown upward into
the air.
15. Thus, a fault can be judged for its capacity to generate earth-
quakes and the maximum event it might produce expressed both in magnitude
and intensity. The intensity can be attenuated from a source to a site.
16. Predicting the time of the maximum earthquake is of interest
for other purposes but is of no interest for the design of a major
5
structure such as a dam. A dam has to be designed on the basis of the
maximum earthquake without regard for its time of occurrence or its
interval of recurrence, since a maximum earthquake may come at any time.
Cost-risk benefits can be sought for appurtenant structures which, if
faiLed, pose no hazard to life. For these lesser structures, probabilities
may be used in order to select smaller events that will then serve as
operational basis eartnquakes. Arbitrarily lower numbers, such as a
fraction of the motions for the maximum earthquake, can be equally
suitable.
17. The foregoing considerations bring us to the point where motions
must be selected to define the effects of earthquakes on a dam. These
motions should be conservative so that the designs developed for a dam
are safe for any eventuality. The motions are in the following categories;
a. Those that cause relative displacement in the foundation
and consequently displacements in the dam, and
b. Those that induce unacceptable strains in a dam or lique-
fR.etiun if it is an earth structure.
18. The examination of a major dam for the effects of earthquake
shaking requires a dynamic analysis. If there are potentials for strain
beneath the structure, earth fill may be specified as the construction
material. For an earth dam it is essential to provide appropriate time
hiBtories of earthquake motion. The time histories are needed because
the material is nonlinearly elastic. Each cycle of shaking may impart
an effect on the material and the effects are cumulative. Thus, the
time histories must be as realistic as possible in simulating the maxi-
mum earthquake.
19. In order to generate time histories, a synthesis may be made
of motions recorded during earthquakes in order to develop peak motions
(aceeleration, velocity, displacement, duration and predominant period).
In Corps of Engineers practice, the time histories are developed first
and response spectra are made from the time histories.
20. Any large collection of strong motion records has a tremendous
spread in the values for earthquake motions. There are many CaUses:
6
differences in fault mechanism and fault shape, rock types and config-
uration, refraction and reflection of waves, superposition and buildup
of waves, or diminution, etc. Such factors contribute to an infinity
of differences in the resulting motions. The accelerations for Modified
Mercalli Intensity V range from 0.01 g to 0.61 g, a spread of 60 times.
Mean values, in such circumstances, have no real significance.
21. The solution is to work with a large body of strong motion
records and to provide envelopes that encompass the spread in the data.
22. Specific parameters, such as a given fault type plus some
specified distance from epicenter, tend to restrict the number of records
available to only a very few. They may have less spread. However, if
there were more records, even for those limited conditions, there is every
reason to believe there would be more spread. It is best not to be
. restrictive but t.o envelope a wide variety of conditions.
23. An extensive statistical analysis of strong motion data from
the western United States in terms of intensity was made by Trifunac and
Brady (191). Their analyses included acceleration, velocity and dis-
placement, and they distinguished vertical and horizontal components of
motion. They showed the mean value for each intensity level and the
mean with one standard deviation. The latter provides a measure of the
dispersion. A problem arises with the sparseness of data for the higher
intensities beginning with MM VIII. There are no data for MM IX, and
one record for MM X. 'l'he latter is the Pacoima record with its peak
horizontal acceleration of 1.25 g.
2 tl. 'rhe same western United States data uniformly processed at
the California Institute of Technology were used in studies made at the
Waterways Experiment Station (see Krinitzsky and Chang, 1977) to find
means for assigning motions for dynamic analyses of dams. The values
were expressed in MM intensity.
25. The CIT data were separated by Krinitzsky and Chang (1977) into
"near field" and "far field."
26. In the near field, complicated reflection and refraction of
waves occur in the subsurface with resonance effects and a large range
7
i~ the scale of ground motions. Intense ground motions and high-frequency
components of motion are present. In the far field the wave patterns are
orderly; the oscillations in wave forms are more muted and more predict-
able; and frequencies are lower.
27. The distance from epicenter to the limits of the near field,
and beginning of the far field, vary with the magnitude of the earthquake,
consequently with the maximum epicentral intensity, and with the region
in which the earthquake occurs. Usually, the intensity in the near
field attenuates linearly ~nd rapidly; in the far field, the rate of
attenuation for intensity becomes smaller.
28. Limits of the near field are as follows:
MM
Richter Maximum Radius of
Magnitude Intensity Near Field
M 10 KM
5.0 VI 5
5.5 VII 15
6.0 Vln 25
6.5 IX 35
r(.o X 40
7.5 XI 45
2Y. Figures 1 and 2 show the relation between MM intensity and
acceleration for near field and far field, respectively. Figures 3 and
4 show intensity versus velocity, near and far field, and Figures 5 and
6 for displacement, near and far field. The motions are horizontal.
Vertical components of motion are taken to be two-thirds the horizontal.
The spread of data were divided into equal 10 percent increments between
50 percent, taken at the median line, and 100 percent, taken along a line
which approximates the limit of observed data. The curves for these
increments are suitable for obtaining peak motions at levels selected
either at the maximum or at lesser levels determined by decisions on the
seismic risk that is acceptable.
30. Figures 1 to 6 also show the mean-plus-one standard deviation
for the respective intensity levels. Figure 1 shows that mean plus a
drops as the intensity increases from MM VII to VIII. The drop-off is
8
not from lesser motions but simply from a decrease in the quantity of
data. The projection of the 10 percent lines attempts to compensate for
thi:> Jack of datu.
31. No distinction was made between data from soil and rock since
the values overlap too greatly to provide useful comparison. The Figures 1
to G are intended to provide peak components of ground motion on bedrock
at the surface.
3;!. rl'he nlean-plus-a values show that the data points are concen-
trated far below the 100-percent line. In effect, the 70-to 80-percent
band brackets an upper boundary for the great body of da.ta. Peak motions
at this level are conservative for nearly all designs. However, if at a
site there was a cupable fault seen at the ground surface, then the
100-percent motion, or even a higher value, might be appropriate.
33. The next element in developing a time history of motion is the
duration. Duration was taken as the bracketed time interval in which
the acceleration is greater than 0.05 g.
34. Some examinations of the data are appropriate. Figure 7 shows
near field durations in terms of earthquake magnitude. There is a large
dispersion with distinctly higher peak values for soil as compared to
rock. Peak durations increase steeply with increase of earthquake mag-
nitude. The same data are shown in Figure 8 by local MM intensity.
Again, soil shows greater peak durations than rock. However, the slope
of the peak duration for rock does not increase as steeply with greater
intensity as it does for magnitude. The discrepancy results from incom-
pleteness of data and the inexactness that is inherent in intensity and a
difference in the comparability of the scales. Figure 8 provides conserva-
tive upper limits for duration to be used with 14M intensities in the near
field.
3 r: ).
Far field durations are shown in Figure 9.
The earthquake records selected for use or for rescaling may be
either actual strong motion records or synthetic ones designed for speci-
fied geological settings. They should be for field conditions that are
analogous to those for the site under study. They should be for com-
parable types of faults, comparable geology (whether crystalline rocks,
9
sedimentary basin, etc.), and similar distances from causative faults.
Records should be selected also with predominant periods that may cor-
respond to periods of engineering works that are being evaluated.
36. The time histories developed from rescaling earthquake records
are preferable for such structures as earth dams since the structures
are nonlinearly elastic and actual earthquake records are both more
realistic and have fewer motions than the synthetic ones. For concrete
portions of a structure, the necessary response spectra can be made from
the time history or it can be obtained independently following the guide-
lines of the Nuclear Regulatory Commission.
31. The scaling for large motions (in the region of 1 g) presents
a problem because there is only one record (Pacoima, San Fernando earth-
quake of 1971) and the rescaling of lesser records to this level may
produce unrealistic motions. Instead of straight scaling, high-frequency
motions may be added to lower earthquakes in combination with a process
of scaling. Multiple records should be examined. Strong motion records
should be selected that require as little rescaling as possible. Chang
(1978) provided a first step toward cataloging earthquakes in a manner
that will facilitate their selection for scaling. If a record has to be
scaled as much as 4x, the record should be discarded.
38. The spectral composition and predominant period of a record is
site dependent (whether soil or rock) and is dependent also on distance
from source. Here again judgments must be made not on a few records but
by envelopes of extensive collections of data. Some guidance is pro~
vided in compilations by Chang and Krinitzsky (1977).
10
PART III: EARTHQUAKE EVALUATION
39. A geological reconnaissance of the general area in which the
Devils Canyon and Watana damsites are located was performed for this study
by Drs. Reuben Kachadoorian and Henry J. Moore of the U.S. Geological
Survey. Their study entitled "Preliminary Report of the Recent Geology
of the Proposed Devils Canyon and Watana Damsites, Susitna River,
Alaska," is included in the present overall report.
40. Drs. Kachadoorian and Moore were charged primarily with the
task of investigating the area for the presence of absence of active
faults. In addition, observations were made on the seismicity of the
area and on the possibilities of landslides into the potential lakes.
41. Prior to the work done by Drs. Kachadoorian and Moore, a study
has been made for the Corps of Engineers by Gedney and Shapiro (1975)
of lineations interpretable for this area from Landsat and Slar imagery.
The lineations were presented along with the seismic history and the
general geology.
42. Gedney and Shapiro show a large number of lineations including
ones that trend along the Susitna Valley and pass through the Devils
Canyon and Watana damsites. Lineations may be caused by faults but they
may be caused also by processes that have no relation to tectonism. In
no case can a lineation be accepted as a fault unless confirmation is
found on the ground by a process that is called "ground truthing."
Thus the work by Kachadoorian and Moore was an important step in vali-
dating the earlier work. The judgments concerning faults should be
those of the latter work.
43. Kachadoorian and Moore report a group of 16 faults. For the
most part, these faults are identified by stratigraphic evidence. There
11
was no surface evidence of recent movement along any of these faults;
consequently, the faults were tentatively judged to be inactive. How-
ever, confirmation of this judgment will require more detailed field
work. The nearest known active fualt is the Denali fault, 80 km away,
with the capacity to produce magnitufe B.O earthquakes.
44. Gedney and Shapiro generally found no relation between seismic
events in the region and faults. However, for the Susitna fault (Fault
No.8 of Kachadoorian and Moore), Gedney and Shapiro associated two
earthquakes of 1 October 1972 and 5 February 1974 (magnitudes 4.7 and
5.0 respectively). Gedney and Shapiro reported no associated breakage
along the Susitna fault but these events gave suitable fault plane
solutions indicating right-lateral offset. Kachadoorian and Moore
question the reliability of associating these earthquakes with the mapped
fault. Kachadoorian and Moore found no relation between seismicity and
mapped faults, however they point out that a closer grid of seismometers
may uncover such relationships.
45. In summary:
a. No faults of important regional extent were found to be
present at the damsites.
b. Major faults in the region were reconnoitered and no evi-
dence was found of recent movement.
c. The region is one of relatively high seismicity, however,
no association was established between seismic events and specific faults.
d. The nearest positive capability for an earthquake is along
the Denali faault, approximately 80 km distant, where a maximum magnitude
of 8.0 can be expected.
e. Except for the conclusions concerning the Denali fault, the
work done so far is preliminary. More work is needed.
12
PART IV: INTERPRETED PEAK MOTIONS
46. On the basis of the present incomplete geological and seismo-
logical information, earthquake motions at the damsites must be postu-
lated by making certain conservative assumptions.
47. Potential earthquakes are as follows:
a. An earthquake originating at the Denali fault. The maxi-
mum magnitude is 8.0 in accordance with assumptions made by the U.S.
Geological Survey in their Trans-Alaska Pipeline Study (see Page, et at,
1972). The earthquake is attenuated 80 km to the Devils Canyon and
Watana damsites. Using the Krinitzsky-Chang (1977) attenuation for
western United States, the event will produce a MM intensity of IX at
these sites. The motions are far field. It is conservative to base
the motions on the 70 percent spread level of the charts of Figures 2,
4, and 6 since that level encompasses over 95 percent of the data in the
velocities (see Figure 4). The duration is taken for rock from Figure 9.
The corresponding peak motions are acceleration, velocity, displacement,
and duration are tabulated in Table 2.
TABLE 2
PEAK EARTHQUAKE MOTIONS AT DEVILS CANYON AND WATANA DAMSITES
Site
Earthquake Intensity
Source Magnitude Field MM
Denali fault 8.0 Far IX
Local floating
event 7.0 Near X
* Vertical motion may be taken as two-thirds
13
Accel.
g
0.28
0.68
Peak Motions (hor.*)
on Bedrock at Surface
Vel. Displ. Duration
em/sec em sec
40 22 10
68 30 12
of horizontal.
b. A local floating earthquake with fault breakage that does
not occur at the damsites. The inconclusive nature of the geologic-
seismologic studies requires that a floating earthquake be assigned.
The earthquake may occur anywhere in the general vicinities of the dam-
sites but not immediately under the dams themselves. The elimination
of an earthquake beneath the dams is based ont hework of Kachadoorian
and Moore for this study in which they identify no appropriate faults.
The magnitude of the floating earthquake is 7.0. This magnitude is in
accordance with the earthquake used for this area in the Trans-Alaska
Pipeline Study of Page, et al (1972). The magnitude accords satisfac-
torily with the possible fault lengths presented by Kachadoorian and
Moore, which are on the order of a hundred or more km. Such faults
correspond to magnitude 7 earthquakes according to available worldwide
data presented by Slemmons (1977) in his Figure 27. Since the near
field for an earthquake of this size extends 40 km from the source, and
Kachadoorian and Moore have located major fault trends within 3 to 15 km
of the dams, the motions at the dams must be taken as near field. It is
conservative to use the 70-percent spread lines of the moitons in Figures
1, 3, and 5 since that level envelopes all but a few extreme values. The
duration for bedrock at the surface is taken from Figure 8. The peak
motions are tabulated in Table 2.
c. An earthquake at the damsites. On the basis of present
information, an earthquake from a major fault rupture at the damsite is
not expected to occur. However, it is understood that present informa-
tion may be subject to revision when further studies are made.
14
48. The motions in Table 2 of this report were developed somewhat
differently from those of the USGS Trans-Alaska Pipeline Study (Page, et
aI, 1972). The floating earthquake for the near field but not at the site
has no equivalent in the USGS analysis. The USGS values are for earth-
quakes that occur at a site. Also, the USGS peaks were reduced from
what they might be by a filtering that they applied to the Pacoima record
of the 1971 San Fernando earthquake. Their objective was to provide
motions for a quasi-static analysis of the pipeline in which the input
was restricted to a range of 2 to 8 Hz. Their resulting magnitude 7 at
a site has values that are higher than ours (1.05 vs 0.68g) in acceleration,
higher in velocity (120 vs 68 em/sec) and higher in displacement (55 vs
45 em). The durations also are greatly different. The USGS duration is
25 sec against 12 sec for ours. The difference is that their duration
includes soils whereas ours is for bedrock alone.
49. Predominant period and records for rescaling are not recommended
at this point since specification of types of faulting and distance from
faulting are yet to be made.
50. The operating basis earthquake, which is lesser earthquake
than that taken for the design of the dam, may be tested with peak
motions that begin at half those of the maximum earthquakes.
15
PART V: ASSOCIATED MOTIONS
51. Reservoir loading has in some cases induced significant earth-
quakes and earthquakes have triggered landslides and caused water waves
or seiches. Also, in regions of tectonism there may be problems during
excavation from overstressed conditions in rock.
Induced seismicity from reservoir loading
52. A few large reservoirs in the world have induced appreciable
earthquakes. Simpson (1976) has provided a summary and critical review.
The reservoir is a triggering agent. It does not cause earthquakes
greater than the ones that may be expected from the normal tectonism.
The maximum earthquakes will be the ones used in design. An induced
earthquake, if such should occur, would not be greater though it may
occur at a different time. Further, the worldwide experience, according
to Simpson (1976), suggests that induced effects may be highest in regions
of low to moderate natural seismicity. In areas of high levels of natural
seismicity, as in Alaska, the stress changes induced by the reservoir are
small compared to natural variations. Thus, induced seismicity should
not add any input to design. Nonetheless, observations relating to
induced seismicity made before and after reservoir filling are appro-
priate and will be valuable on a research level.
Water waves from earthquake shaking
53. Water waves produced by earthquake shaking, under certain cir-
cumstances, may be a factor though hardly comparable to the effects of
large landslides and ordinarily not more severe than wind effects. The
effects are dependent on the spectral composition of the horizontal
ground motions, the shape and size of the reservoir, and the duration
of shaking. If a resonance is developed there may be significant resul-
ting wave amplitudes. Lee and Hwang (1977), in assessing this problem,
suggest that wave heights of half the amplitude of horizontal ground
motions are possible but they do not assess resonance. In practice,
protection against the effects of landslides will probably more than
adequately provide protection against water waves as well.
16
~;arthquake-induced lancisli(ies
511. Landslides are a pronounced feature at the sites of major
earthquake;;. Kachadoorian and Moore have noted appreciable landslides
in the Susitna Valley. These, and others that may be judged to be present
as potential hazards, should be evaluated. The worst known potential
slides can be monitored and remedial measures can be specified, including
the removal of the potential slide material.
J:). The problem when dealing with a maj or earthquake is that one
cannot be sure that slides that might be generated have been anticipated.
Given sufficient topocraphic relief and large masses of loose or frac-
tured material, one should take into account major slides for which no
prevention can be specified. Developments along the borders of the
reservoir, the freeboard of the dam, etc., should be planned so that
possible disasters are avoided.
56. Studies of the effects of landslides into reservoirs may be
either theoretical, using a numerical model (see Raney and Butler, 1975),
or they may be empirical. The latter is perhaps the most practical
approach. They involve using undistorted hydraulic models (cf Davidson
and Whalin, 197h). For both methods, the slide geometry, volume, velo-
city and reservoir configuration are essentials. Field investigations
where actual landslides have occurred may aid in developing estimates
of velocities (see Banks and Strohm, 197h). The procedures will produce
assessments of wave heights and wave runups.
Tectonic strain and overstressed conditions in rock
57. A totally unknown set of conditions are those that relate to
tectonic strain and resulting possible overstressing in the rock. Re-
sidual stresses from the movements of active faults can affect the making
of excavations and the stability of the structure. At present there are
no data. It is anticipated that field measurements relating to stresses
and the buildup of strain will be made as part of any continuing
investigations.
17
PART VI: CONCLUSIONS
58. The geological-seismological investigations to date were
made on reconnaissance levels. The Devils Canyon and Watana damsites
are in a region of high seismicity and major faults. However, no move-
ments were found on the faults that might be indicative of earthquakes.
Also, no seismic activity was identified as associated with these faults,
though the data suffers from inexactness in the accuracy of locations.
No active faults were found at the damsites. Active faults of appreciable
length are required if large earthquakes are to be generated in close
proximity of the proposed structures.
59. The area was provided with a floating earthquake of magnitude
7 placed at a short distance from the damsites. The magnitude 7 is in
conformity with general fault lengths in this area and with worldwide
experiences between such faults and resulting earthquakes. However,
further field studies will be made to determine conclusively whether
or not there are faults closer to the sites with possible more severe
motions. An earthquake of magnitude 8 from the Denali fault at a distance
of 80 km was evaluated by attenuating the event to the damsites.
60. Peak motions were assigned for the earthquakes following the
practices of the Corps of Engineers. The magnitude 7 earthquake near
the damsites has motions that are: acceleration 0.68 g, velocity 68
em/sec, displacement 30 em, and duration 12 sec. An earthquake at the
Denali fault attenuated to the sites provides motions of 0.28 g, 40 cm/
sec, 22 em, and 10 sec.
61. A closer specification of which sets of peak motions to apply
and the appropriate time histories will await further field studies.
18
()2. Possible induced seismicity from reservoir loading is not a
factor needing additional design but is accounted for in the existing
motions. However, water waves from possible earthquake-triggered land-
Glide!J and possible overstressed conditions in rock pose problems for
which at present there is a paucity of data and a need for further
evaluation.
19
L1. Simpson, David W. (1976), Seismicity Changes Associated with
Reservoir Loading, Elsevier, Engineering Geology, 10:123-150.
1;2. ~.acmlTlons, David B. (191'7), Faults and Earthquake Magnitude, State-
of-the-Art for Assessing Earthquake Hazards in the United States,
Report 6, Waterways Experiment Station, Vicksburg, Mississippi,
129 pp plus Appendix, 37 pp.
13. 'J'rifunac, M. D. and A. G. Brady (1975), On the Correlation of
Seismic Intensity Scales with the Peaks of Recorded Strong Ground
Motion, B. Seism. Soc. Am., Vol 65, No.1, pp 139-162.
21
EXHIBIT 0-4
Procedure for Estimating Borehole Spacing and
Thaw Water Pumping Requirements for Artificially
Thawing the Bedrock Permafrost at the Watana
Oamsite.
Technical Note
PROCEDURE FOR ESTIMATING BOREHOLE SPACING
AND THAW-WATER PUMPING REQUIREMENTS
FOR ARTIFICIALLY THAWING THE BEDROCK PERMAFROST
AT THE WATANA DAM SITE
F. H. Sayles'
October 1978
Corps of Engineers, U.S. Army
COLD REGIONS RESEARCH fu~D ENGINEERING I.ABORATORY
Hanover, New Hampshire
Introduction
The procedure outlined in this note for estimating the time to
artificially thaw permafrost bedrock assumes that water will be pumped
into a pattern of boreholes drilled to the bottom of the permafrost
zone. The water would flow down a feed pipe to the bottom of the bore-
hole and back up the annulus between the outside of the feed pipe and
the wall of the borehole. During the upward flow, heat from the water
would flow radially through the borehole wall to melt the existing ice
and raise the temperature of the surrounding rock. During the first stage
of this thawing process a series of essentially vertical parallel thawed
cylinders would be formed~ the diameter of which would grow with time
until the surface of adjacent cylinders touched. Upon touching a fluted
wall would exist which then will thicken as additional heat is supplied
by the thaw-water in the boreholes until either the desired wall thickness is
attained or a thermal equilibrium is established. Once the desired wall
thickness is reached, the rate of thaw-water flow (i.e., pumping) can be
reduced to establish thermal equilibrium. To avoid freezing back the bed-
rock it may be necessary to continu~ pumping water until grouting is
initiated or until it is unnecessary to maintain the wall in a thawed
condition. If the permafrost is at 32°F at the Watana dam site, it probably
would not be necessary to use maintenance pumping since freeze-back would
be quite slow.
The purpose of this note is to furnish procedures for establishing a
drilling pattern; estimating the time to thaw a 20 ft. wide zone of rock
permafrost along the alignment of the Watana Dam; and estimating the
thaw-water pumping requirements for the thawing operation.
Assumptions
The graphs used in this procedure were developed using the thermal
computational methods outlined in the paper, "Thermal ,and Rheological
Computations for Artificially Frozen Ground Construction," which is
attached as Appendix B. The assumed rock properties and thermal conditions
are listed in Appendix A. Graphs in figures I and 2 were developed for
l~ inch diameter boreholes. Use of larger diameter boreholes would reduce
the thawing time (e.g., a 3 inch diameter borehole will reduce the thaw time
by less than 10%).
It should be emphasized that this procedure assumes a uniform distribution
of ice in the bedrock with an overall ice saturated porosity of l~% and that
it is quite probable that some of the rock will contain much larger volumes qf
ice. At locations where large volumes of ice do exist, the thawing would be
much slower than predicted by Figure 1. More accurate predictions of the
thawing times can be made when details of the amount and location of the ice-
filled cracks are determined. The temperature of the permafrost bedrock at
the dam site has not been established precisely. In this note, bedrock
temperature is assumed to be 32 0 F with all water frozen.
To control the thawing process during construction, it is essential to
monitor the bedrock temperature at several locations both horizontally and
vertically. Good temperature and pumping records will assist in improving
the thawing operations as the work progresses and will provide data for
refining the procedure for predicting subsequent thawing times and pumping
2
requirements.
Procedure
(1) From the curves on Figure 1 choose a borehole arrangement (i.e.,
single row or two rows of boreholes) and spacing. The choice would be
based on the time available for thawing, the temperature of the available
thaw-water and the economic trade-offs between additional holes vs heating
the water and pumping water.
(2) After selecting the borehole spacing, enter the graph on Figure
2 using the borehole spacing and thaw-water temperature chosen in (1) to
obtain a time at which the thawing cylinders will just touch each other.
This time (t r ) is given in days on the abscissa.
(3) Using (t r ) from (2), enter the abscissa of the graph on Figure
3 and obtain an estimate of the number of gallons per minute (GPM) that
must be supplied to each borehole for the thaw-water temperature selected.
Note that this is the thaw-water flow required when the thawed cylinders just
touch. This is more than that required to continue thawing until the wall
obtains its full width but it is a conservative average value to use in
estimating. The maximum flow rate is required at the start of pumping.
Theoretically it is infinite but in practice it is close to the values
shown at time zero on Figure 3. Therefore, after the first few days of
pumping, the pumping capacity can be reduced, e.g., one or more of the pumps
can be used somewhere else. The curves on this graph are based on the
temperature gradient or temperature loss shown on the graph. rf sufficient
3
flow is not supplied to the boreholes, the temperature gradient will rise
and the time r~quired to thaw will increase.
(4) After the rate of flow for each borehole is estimated, the
velocity of the thaw-water flow in the feed pipes and the annulus between
the outside of the feed pipe and the borehole wall should be computed to
determine if either the velocity or pressure drop is excessive.
(5) The total rate of flow for determining the size and number of
pumps is determined by summing up the number of boreholes that are used
for thawing at one time.
It might be noted that if water is artificially heated, there will be a
large energy loss if the overflow from the borehole is not captured and
reused.
Ponding of water in a location where the sun can warm it is one way to
get higher thaw-water temperatures than would be obtained by taking water directly
from the river.
4
APPENDIX A
ASSL~ED ROCK PROPERTIES AND THERMAL VALUES
ROCK PROPERTIES
Uniform porosity
Specific Gravity
Dry Unit Weight
Ice Saturate
THERMAL VALUES
Volumetric Specific Heat
Unfrozen Rock
Frozen Rock
1.5%
2.68
165 lb/ft 3
Conductivity for Unfrozen Rock
Latent Heat of Ice Saturated Rock
33.9 BTU/ft 3
33.4 BTU/ft 3
1.6 BTU/hr. ft. OF
124 BTU/ft3
EXHIBIT 0-5
U.S. Geologicaly Survey Reconnaissance Geologic Map
and Geochronology, Talkeetna Mountains Quadrangle,
Northern Part of Anchorage Quadrangle, and South-
western Portion of Healy Quadrangle, Alaska.
UNITED STATES DEPARTMENT OF THE INTERIOR
GEOLOGICAL SURVEY
RECONNAISSANCE GEOLOGIC MAP AND GEOCHRONOLOGY, TALKEETNA MOUNTAINS
QUADRANGLE, NORTHERN PART OF ANCHORAGE QUADRANGLE, AND SOUTHWEST
CORNER OF HEALY QUADRANGLE, ALASKA
By
Bela Csejtey, Jr., W. H. Nelson, D. L. Jones, N. J. Silberling,
R. M. Dean, M. S. Morris, M. A. Lanphere, J. G. Smith,
and M. L. Silberman
Description of map units, Structure, Tectonics, Reference list,
and tables to accompany ~pen-file Report
This report is preliminary and has
not been edited or reviewed for
conformity with Geological Survey
standards and nomenclature
DESCRIPTION OF MAP UNIT&
SEDIMENTARY AND VOLCANIC ROCKS
Qs SURFICIAL DEPOSITS, UNDIFFERENTIATED (Quaternary)--Glacial and
alluvial deposits, chiefly unconsolidated gravel, sand, and
clay.
Tv VOLCANIC ROCKS, UNDIFFERENTIATED (Paleocene to Miocene, uppermost
part may be as young as Pleistocene)--Over 1,500-m-thick sequence
of felsic to mafic subaerial volcanic rocks and related shallow
intrusives. Lower part of sequence consists of small stocks,
irregular dikes, lenticular flows, and thick layers of pyro-
clastic rocks; made up dominantly of medium-to fine-grained,
generally medium-gray quartz latite, rhyolite, and latite. A
few dikes and intercalated flows of brown andesite are also pres-
ent. Rocks of the lower part of the sequence, occurring mostly
in the upper Talkeetna River area, are interpreted to be vent
facies deposits and near vent deposits of stratovolcanos. The
upper part of the sequence consists of gently dipping brown ande-
site and basalt flows interlayered with minor amounts of tuffs.
A few lenses of fluviatile conglomerate are also present. Locally,
at Yellowjacket Creek for instance, the feeder dikes of the mafic
flows make up more than half the volume of the underlying
country rocks. According to E. M. MacKevett, Jr. (oral commun.,
1975), the andesite and basalt flows are lithologically identi-
cal to the basal andesites of the Wrangell Lava in eastern Alaska.
Contact between the dominantly felsic lower part and mafic
upper part of the sequence is gradational through intertongu~
ing of the two rock types. The three samples for potassium-
argon age determinations (map numbers 7, 8, 13 in table 1),
indicating Paleocene and Eocene ages, were obtained from ande-
site flows near the middle of this sequence.
Tim HYPABYSSAL MAFIC INTRUSIVES (Paleocene to Miocene, youngest rocks
may be Pleistocene)--Small stocks and irregular dikes of dio-
rite porphyry, diabase, and basalt. They probably are the sub-
volcanic equivalents of the andesite and basalt flows of unit Tv.
Tif HYPABYSSAL FELSIC INTRUSIVES (Paleocene to Miocene, some rocks
may be as young as Pleistocene}--Small stocks and irregular
dikes of rhyolite, quartz latite, and latite. Lithologically,
they are identical to, and thus probably correlative with the
felsic subvolcanic rocks of unit Tv.
Ttw TSADAKA (Miocene) AND vHSHBONE (Paleocene and Eocene) FORMATIONS,
UNDIVIDED--Tsadaka Formation, occurring only at Wishbone Hill,
consists of cobble-boulder conglomerate with thin interbeds of
sandstone, siltstonei and shale; about 200 m thick. The Wish-
bone Formation, which unconformably underlies the Tsadaka, com-
prises well-indurated fluviatile conglomerate with thick inter-
beds of sandstone, siltstone, and claystone; about 600 to 900
m thick (Detterman and others, 1976; Barnes, 1962). The present
map unit also includes over 150 111 of fluviatile conglomerate
2
and coaly sandstone (unit Tf of Grantz, 1960a, b) in the east-
ern Talkeetna Mountains.
Tc CHICKALOON FORMATION {Paleocene)--Well-indurated, continental,
dominantly fluviatile sequence of massive feldspathic sandstone,
siltstone, claystone, and conglomerate, containing numerous beds
of bituminous coal; over 1,500 m thick (Barnes, 1962).
Tsu SEDIMENTARY ROCKS, UNDIFFERENTIATED {Tertiary)--Fluviatile con-
glomerate, sandstone, and claystone with a few thin interbeds
of lignitic coal. Lithologically, these rocks look similar to
the Tertiary sedimentary rocks of the southern Talkeetna Moun-
tains, but lack of fossil evidence does not permit more defini-
tive correlation. The largest exposure of these rocks is along
Watana Creek, and, according to Smith (1974a), the sequence is
over 160 m thick. Lithologically, it resembles the Paleocene
Chickaloon Formation of the Matanuska Valley.
PLUTONIC AND METAMORPHIC ROCKS
Tgd TERTIARY GRANODIORITE (Eocene)--Contains hornblende and biotite.
This granodiorite is part of a small pluton along the northern
edge of the map area. Turner and Smith (1974) report an Eocene
age for this pluton, determined by the potassium-argon method
on biotite (48.8~1.5 m.y.) and on hornblende (44.8~1.3 m.y.)
from a sample just north of the present map area.
Thgd BIOTITE-HORNBLENDE GRANODIORITE (Paleocene, in part may be Eocene)--
Rocks of this unit occur in one large and several smaller,
3
poorly exposed plutons in the western and northern Talkeetna
Mountains. All of the plutons were forcibly intruded in the
epizone of Buddington (1959). Granodiorite is the dominant
rock, but locally it grades into adamellite (= granite with
plagioclase and alkali feldspar in approximately equal propor-
tions), tonalite, and quartz diorite. All these rocks are
medium to dark gray, medium grained, generally structureless,
and have granitic to seriate textures. In all of them. horn-
blende is the chief mafic mineral. Biotite-and hornblende-
rich xenoliths of reconstituted country rock are common in
every pluton. The lithologic compositions and available age
determinations (see table 1) indicate that these granitic rocks
are the plutonic equivalents of some of the felsic rocks in the
lower portion of unit Tv.
Tbgd BIOTITE GRANODIORITE (Paleocene, in part may be Eocene)--Biotite
granodiorite and adamellite in approximately equal proportions.
Biotite is the chief mafic mineral, hornblende is occasionally
present. Color is light to medium gray, grain size is from
medium to coarse, texture is granitic to seriate. Very faint
flow structures have developed only locally. These rocks occur
in shallow, forcibly emplaced epizonal plutons in the north-
western Talkeetna Mountains. Aplitic and pegmatitic dikes are
common in all the plutons. Just north of the map area, these
plutonic rocks grade into felsic volcanic rocks. Potassium-
4
argon age determinations (see table 1) indicate that the bio-
tite granodiorite and adamellite of the present unit are essen-
tially of the same age as the biotite-hornblende granodiorite
(unit Thgd). Thus, the rocks of these two units, in view of
their spatial proximity, probably are the products of differen-
tiation of the same parent magma, either in situ or at some
deeper levels in the Earth's crust. The biotite granodiorite
intrusives are also considered to be the plutonic equivalents
of some of the felsic volcanic rocks in the lower portion of
unit Tv.
Tsmg SCHIST, MIGMATITE, AND GRANITE {Paleocene intrusive and metamor-
phic ages)--Undifferentiated terrane of andalusite and (or)
sillimanite-bearing pelitic schist, lit-par-lit type migmatite,
and small granitic bodies with moderately to well-developed
flow foliation. These rocks occur in approximately equal pro-
portions, and the contacts between them are generally gradational,
as is the contact between the schist and its unmetamorphosed
pelitic rock equivalents (unit Kag) outside the present map
unit.
The pelitic schist is medium to dark gray, medium grained,
has well-developed but wavy foliation, and contains lit-par-1it
type granitic injections in greatly varying amounts. Rock-
forming minerals of the schist include biotite (pleochroism
Nz = dark reddish brown, Nx = pale brown), quartz, plagioclase,
5
minor K-feldspar, muscovite, garnet, and sillimanite which
locally coexists with andalusite.
The lit-par-lit type granitic injections within the schist
are medium gray, medium grained, and consist of feldspar, quartz,
and biotite.
The rocks of the small, granitic bodies range in composi-
tion from biotite adamellite to biotite-hornblende granodiorite.
They are medium gray and medium grained, generally have grani-
tic textures, and, in addition to the flow foliation, locally
display flow banding of felsic and mafic minerals. These grani-
tic bodies appear to be the source of the lit-par-lit intrusions.
The proximity of the schist to the small granitic bodies,
the occurrence of the lit-par-lit injections, and the presence
of andalusite in the schist indicate that the schist is the
result of contact metamorphism. Perhaps this metamorphism took
place in the roof zone of a large pluton, the cupolas of which
may be the small granitic bodies.
TKt TONALITE (Upper Cretaceous and Lower Paleocene)--Dominantly biotite-
hornblende tonalite, locally grades into quartz diorite. The
tonalite is medium gray, coarse to medium grained, has a grani-
tic texture and a fairly well-developed primary foliation. It
occurs in a large, possibly composite, batholith, approximately
75 to 61 m.y. old (see table 1), which was emplaced in the epi-
zone and mesozone of Buddington (1959). The tonalite is described
in more detail in Csejtey (1974).
6
TKa ADAMELLITE (Upper Cretaceous and Lower Paleocene)--Occurs in a
large epizonal pluton in the southwestern part of the map area.
The dominant rock type is adamellite but locally includes gran-
odiorite. 8iotite is the chief mafic mineral, muscovite occurs
in subordinate amounts. The typical adamellite is medium to
light gray, medium to coarse grained, its texture ranges from
granitic to seriate. The adamellite appears to be intrusive
into the tonalite (unit TKt). but concordant potassium-argon
ages on one sample (map no. 24~ table 1) indicate the adamellite
to be essentially the same age as the tonalite. These rocks
apparently are comagmatic.
TKgr GRANITIC ROCKS, UNDIVIDED (Cretaceous and (or) Tertiary)--These
rocks of uncertain age occur in four smaller epizonal plutons
of granodiorite and tonalite. Their color is medium to dark
gray, grain size is medium, texture is granitic. Mafic minerals
are hornblende and (or) biotite. The largest of these plutons,
in the northeast corner of the map area, is reported by Smith
and others (1975) to be of Cretaceous age.
TKlg LEUCOGABBRO (Cretaceous and (or) Tertiary)--Small, poorly exposed
intrusive of uncertain age in west-central part of map area,
essentially consisting of plagioclase (around An70 and about
80 percent of volume), and pale-green hornblende. The leuco-
gabbro is medium to light gray, coarse to medium grained, with
a granitic to seriate texture.
7
SOUTHEASTERN TALKEETNA MOUNTAINS
Sedimentary and volcanic rocks
Kar ARKOSE RIDGE FORMATION (Cretaceous)--Arkosic sandstone, conglom-
erate, graywacke, siltstone, and shale (Detterman and others,
1976; Grantz and Wolfe, 1961). Clastic components consist
chiefly of granitic and metamorphic rock fragments, quartz,
feldspar, and biotite, indicating a dominantly plutonic and,
to a lesser extent, metamorphic provenance (G. R. Winkler, oral
commun., 1977). Numerous plant fragments suggest a dominantly
terrestrial origin. Recent field and petrographic studies
~sejtey and others, 1977) indicate that this formation is of
Cretaceous age. A pre-Tertiary age is also indicated by a
potassium-argon age determination on biotite (map no. 37, table
1). The biotite was separated from a sample of graywacke with
secondary biotite, obtained from near the tonalite pluton (unit
TKt). The formation rests unconformably on Jurassic granitic
and metamorphic rocks and is as much as 700 m thick. In this
report the Arkose Ridge is considered to be a dominantly non-
marine facies of the Cretaceous Matanuska Formation.
Km MATANUSKA FORMATION (Lower and Upper Cretaceous)--Well-indurated
shale, siltstone, sandstone, graywacke, with subordinate con-
glomerate interbeds; occurs along the southern edge of the map
area, mostly in the Matanuska Valley. These rocks, having a
total thickness in excess of 1,200 m, are generally dark gray
8
and thinly bedded, and for the most part were deposited in a
marine environment of moderate to shallow depths. Some of the
sandstone beds contain fragmentary plant remains. Age of the
formation ranges from Maestrichtian at the top to Albian at
the base (Grantz, 1964). The formation rests with a pronounced
angular unconformity on Lower Cretaceous and older strata. In
part, the MatanlJska Forniation correlates with the Kennicott,
the Shulze, the Chititna, and the MacCall Ridge Formations of
the southern \~rangell r10untains (Jones, 1967).
Ksu SEDIMENTARY ROCKS, UNDIVIDED (Lower Cretaceous)--A shallow water
marine sequence of thinly bedded calcareous sandstone, siltstone,
claystone, minor conglomerate, and thick-bedded to massive
clastic limestone; interpreted as a continental shelf-type
deposit; Over 100 m thick. These strata occur in the south-
eastern Talkeetna Mountains, and they have been previously mapped
and dated by Grantz (1960a, b). The present undivided unit
includes Grantz' units Ks, Kc, and the Nelchina Limestone. The
contact between these strata and the underlying Jurassic Naknek
Formation (unit In) is a slightly angular unconformity. The
Nelchina Limestone correlates with the Berg Creek Formation of
the southern Wrangell Mountains (E. M. MacKevett, Jr., oral
conunun., 1977).
In NAKNEK FORMATION (Upper Jurassic)--Shallow water marine, thin to
thick bedded, intercalated strata of fossiliferous gray
9
siltstone, shale, sandstone, and conglomerate; over 1,400 m
thick. Previously mapped and dated by Grantz (1960a, b). The
Naknek Formation is restricted to the southeastern Talkeetna
Mountains, lacks any contemporaneous volcanic material, and
appears to have been deposited in a continental shelf environ-
ment. Its contact with the underlying Chinitna Formation is a
very slightly angular unconformity. The Naknek correlates with
the Root Glacier Formation of the southern Wrangell. Mountains
(E. M. MacKevett, Jr., oral commun., 1977).
Jct CHINITNA FORMATION (Upper Jurassic) AND TUXEDNI GROUP (Middle
Jurassic), UNDIVIDED--The Chinitna Formation consists of a shal-
low marine, intercalated sequence of dark-gray shale, siltstone,
and subordinate-graywacke; contains numerous large limestone
concretions; it is as much as 600 m thick. The Tuxedni Group
unconformably underlies the Chinitna,and consists of shallow
marine, well-indurated, thinly to thickly bedded graywacke,
sandstone, and massive conglomerate in its lower part, and thinly
to thickly bedded dark siltstone and shale in its upper part.
The Tuxedni is about 300 to 400 m thick. Both the Chinitna
and Tuxedni have been previously mapped and dated by Grantz
(1960a, b; 1961a, b), by Grantz and others (1963), and by Detter-
man and others (1976). Both formations occur in the southeast-
ern part of the map area, are devoid of coeval volcanic
material. and are interpreted to have been deposited in a
10
continental shelf environment. The contact between the Tuxedni
Group and the underlying Talkeetna Formation (unit Jtk) is a
major angular unconformity. The Chinitna and Tuxedni are partly
correlative with the Nizina Mountain Formation of the southern
Wrangell Mountains (E. M. MacKevett, Jr., oral commun., 1977).
Jtk TALKEETNA FORMATION (Lower Jurassic)--Andesitic flows, flow brec-
cia, tuff, and agglomerate; subordinate interbeds of sandstone,
siltstone, and limestone (mapped separate1y as unit Jls), espe-
cially in upper part of the formation. A dominantly shallow
marine sequence, about 1,000 to 2,000 m thick (Grantz, 1960a, b;
1961a, b; Grantz and others, 1963; Detterman and others, 1976).
This formation occurs only in the southeastern half of the mapped
area and its base is nowhere exposed. The occurrence of marble
(units Jmb and Jmbr) within the plutonic and metamorphic rocks
just northwest of the Talkeetna Formation outcrop area suggests
that the formation is underlain by volcanogenic rocks of Triassic
(unit lRv) and of Paleozoic age (unit Pzv).
Jls LIMESTONE (Lower Jurassic)--Light-to dark-gray, fine-to mediurn-
grained unfoss1liferous limestone; near granitic rocks recry-
stallized to medium-to coarse-grained marble. Forms discontin-
uous lenticular bodies, as much as 30 m thick, within Talkeetna
Formation.
11
Plutonic and metamorphic rocks
Kum SERPENTINIZED ULTRAMAFIC ROCKS (Lower and (or) Upper Cretaceous)--
These rocks occur in small, tectonically emplaced, discordant
bodies (protrusions) within the probably Lower to Middle Juras-
sic pelitic schist (unit Jps) near Willow Creek. They are
medium greenish gray to black in color, and are composed of
aphanitic masses of serpentine, talc, minor amounts of actinolite-
tremolite, chlorite, and opaque minerals. Relict textures were
nowhere observed, and all these bodies are strongly sheared.
Semiquantitative spectrographic analyses indicate chromium con-
tents to be between 1,000 and 5,000 ppm and nickel between 1,000
and 2,000 ppm (analyses by D. F. Siems and J. M. Motooka, 1973).
Fire assay analyses of ten samples show both platinum and pal-
ladium contents to range from 0.0 ppm to 0.030 ppm (analyses
by R. R. Carlson, 1973). However, the average platinum to pal-
ladium ratio is only about three to one. Potassium-argon age
determinations on actinolite-tremolite from two samples yielded
early Late Cretaceous minimum ages (map nos. 32,36, table 1).
These minimum ages coincide in time with a middle to Late Cre-
taceous period of intense, alpine-type orogenic deformation
(see Structure and Tectonics sections) of the Talkeetna Moun-
tains region. Thus, the serpentinite bodies, whose original
age is unknown, are assumed to have been emplaced during this
orogeny.
12
Jtr TRONDHJEMITE (Upper Jurassic)--Forms a discordant, northeast-
trending, elongate, epizona1 pluton of fairly uniform lithology
in the central Talkeetna Mountains. Large portions of the pluton
have been sheared and saussuritized. Typically, the trondhjemite
is light gray, medium to coarse grained with a granitic texture.
A faint flow foliation is locally developed. Major rock form-
ing minerals are plagioclase (oligoclase to sodic andesine),
quartz, K-fe1dspar (between 0 to 10 percent of volume), and
biotite, with subordinate amounts of muscovite, and opaque min-
erals. Color index ranges from 3 to 9. Average oxide percent-
ages, by weight, of seven trondhjemite analyses are: Si0 2 -
70.30, A1 203 -16.74, K20 -1.27, Na 20 -5.07, CaO -3.33.
Potassium-argon age determinations (map nos. 21,22,26,31,
table 1) from the southern part of the pluton show considerable
variation in age, which is attributed to resetting. However,
three age determinations from the northern half of the pluton
(map nos. 10,11,14, table 1), including concordant ages on
a mineral pair of muscovite and biotite, yielded very similar num-
bers indicating the emplacement of the trondhjemite pluton between
145 to 150 m.y. ago. The trondhjemite is the youngest member
of a group of Jurassic plutonic and metamorphic rocks in the
Talkeetna Mountains.
Jgd GRANODIORITE (Middle to Upper Jurassic)--Dominant1y granodiorite
but includes minor amounts of tonalite and quartz diorite.
13
These epizonal plutonic rocks, underlying considerable areas
in the central and eastern Talkeetna Mountains, were probably
emplaced as multiple intrusion of consanguineous magmas. They
are medium to dark gray, medium grained, and in undeformed rocks
the texture is granitic. Mafic minerals are hornblende and
biotite in various proportions. Along the northwestern border
of its exposure area, the granodiorite and related rocks have
been cataclastically deformed, resulting in a pronounced north-
east-trending secondary foliation and, to a lesser degree,
lineation. The width of the deformed zone varies from about
2 km to 25 km. Isotopic age determinations (map numbers 15-17,
27, tables 1, 2) from four separate localities indicate that
emplacement, probably multiple intrusions, took place approxi-
mately 150 and 175 m.y. ago. While the Upper Jurassic trond-
hjemite intrudes the granodiorite, the granodiorite itself
intrudes the Talkeetna Formation of Lower Jurassic age (Grantz
and others, 1963).
Jgdm MIGMATITIC BORDER ZONE OF GRANODIORITE (Middle to Upper Jurassic)--
Forms a terrane of poorly exposed, intricately intermixed con-
tact schist, amphibolite, and small dikes and veinlets of gran-
odiorite; all of these rock types occur in approximately equal
proportions.
The contact schist is dark to medium gray, medium grained;
rock-forming minerals are quartz, biotite, and subordinate
plagioclase.
14
The amphibolite is dark gray, medium grained, and consists
of hornblende and plagioclase; megascopic schistosity is seldom
conspicuous.
The granodiorite is the same as that of unit Jgd; most of
the veinlets have been intruded along foliation planes.
The metamorphic rocks of this unit were probably derived
from either the Talkeetna Formation (unit Jtk) or from the upper
Paleozoic volcanogenic sequence (unit Pzv), or possibly in part
from the Upper Triassic basaltic sequence (unit TRv).
Jmrb MARBLE (Middle to Upper Jurassic metamorphic age)--Contact meta-
morphosed marble bed more than 40 m thick within migmatitic
border zone (unit Jgdm). The marble is poorly exposed and
occurs only along John Creek, a tributary of upper Kosina Creek.
The rock is white, coarse to medium grained, and contains num-
erous porphyroblastic crystals of andradite garnet and diopside.
The marble was derived from a limestone bed, probably within
the upper Paleozoic volcanogenic sequence (unit Pzv) or pos-
sibly within the Upper Triassic basaltic sequence (unit lRv).
~qd QUARTZ DIORITE (Lower to Middle Jurassic)--Epizonal intrusive in
the southern Talkeetna Mountains. Dominantly quartz diorite
but also includes diorite and tonalite. Large portions of this
rock have been sheared and intensively altered. The fresh
quartz diorite is medium to dark greenish gray, medium to coarse
grained, and has a granitic texture. Rock-forming minerals are
plagioclase (andesine), quartz, hornblende, subordinate biotite
15
and K-feldspar. Where altered, the quartz diorite consists of
mineral aggregates of epidote, chlorite, and sericite, as well
as some remnants of the primary minerals. The age of the
quartz diorite is probably late Early Jurassic or early Middle
Jurassic because it intrudes the Talkeetna Formation and is
intruded by the Middle to Upper Jurassic granodiorite of unit
Jgd.
Jam AMPHIBOLITE (Lower to Middle Jurassic metamorphic age)--Forms a
metamorphic terrane consisting dominantly of amphibolite but
includes subordinate amounts of greenschist and foliated diorite.
This metamorphic terrane also includes several interbeds of
coarsely crystalline marble which are mapped and described separ-
ately (unit Jmb).
The amphibolite is generally dark greenish gray, medium
to coarse grained, but fine-grained varieties also occur. Foli-
ation and lineation are generally poorly developed, and segre-
gation layering is rare. Major rock-forming minerals are. in
approximately equal proportions, anhedral to euhedral hornblende
(Z = dark green to brownish green, occasionally bluish green)
and anhedral, generally twinned plagioclase ranging from labra-
dorite to calcic andesine. Accessory minerals are quartz,
garnet, sphene, apatite, opaques, occasional epidote, and, in
some of the rocks, shreds of biotite.
The greenschist is dark greenish gray, fine to medium grained,
with a moderately well-developed schistosity. Major minerals
16
are actinolite, untwinned plagioclase (probably albite), epidote,
chlorite, quartz, and opaques. Some of the actinolite-like
amphibole may actually be aluminous hornblende, thus some of
these rocks may be transitional to amphibolite.
The foliated diorite is very similar .to the amphibolite in
appearance. It is dark greenish gray, medium to coarse grained,
with a generally well-developed shear foliation. A remnant
granitic texture is always discernible in thin section. Rock-
forming minerals are hornblende, twinned and occasionally zoned
plagioclase (andesine to sadic labradorite), with subordinate
amounts of chlorite and epidote, minor quartz and biotite, and
opaques.
All of the above rocks, as well as the quartz diorite of
unit Jqd, apparently are the earliest products of a Jurassic
plutonic and metamorphic event which appears to have started
in the Talkeetna Mountains in late Early Jurassic time after
the deposition of the Talkeetna Formation (unit Jtk). A potas-
sium-argon age determination on hornblende of a diorite or
amphibolite sample (map no. 5, table 1) from the northeast part
of the map area yielded an age of 176.6 m.y. (Turner and Smith,
1974), suggesting an Early to Middle Jurassic age for the amphi-
bolite and associated rocks. The quartz diorite of unit Jqd in
the southern Talkeetna Mountains is probably correlative with
the sheared diorite of the amphibolite terrane.
17
The metamorphic rocks of the amphibolite terrane probably
were derived from any or all of the following dominantly basic
volcanic formations: Talkeetna Formation (unit Jtk), upper
Paleozoic volcanogenic sequence (unit Pzv), or the Upper Trias-
sic basaltic sequence (unit lRv). The pods of greenschist,
intercalated with the amphibolite, suggest that the metamor-
phism in the amphibolite terrane was not of uniform intensity.
Jmb MARBLE (Lower to Middle Jurassic metamorphic age)--White, medium-
to coarse-grained marble. It occurs in massive interbeds, as
much as 30 m thick, within the amphibolite terrane of unit Jam.
The marble contains subordinate amounts of garnet and diopside.
Its parent rock was a limestone bed, probably within the Tal-
keetna Formation (unit Jtk) or within the upper Paleozoic vol-
canogenic sequence (unit Pzv), or, least likely, within the
Upper Triassic basaltic sequence (unit lRv).
Jmi AMPHIBOLITE AND QUARTZ DIORITE (Lower to Middle Jurassic meta-
morphic and plutonic ages)--Forms a terrane of intricately
intermixed amphibolite and quartz diorite in about equal amounts
in the southern Talkeetna Mountains.
The amphibolite ;s very similar to the amphibolite of unit
Jam, thus the two amphibolites are considered to be correlative,
and no description ;s given here. One difference is that segre-
tion layering of mafic and felsic components is more prevalent
in the amphibolite of unit Jm;. A thin wedge of biotite-quartz-
feldspar gneiss, probably derived from a nonvolcanic clastic
18
interbed, is intercalated with the amphibolite along -lower
Granite Creek (Detterman and others, 1976; Travis Hudson, oral
commun., 1978).
The quartz diorite is petrographically identical to the
quartz diorite in adjacent unit Jqd (see rock description there),
and the two rocks are considered to be correlative. The quartz
diorite of the present unit is generally more altered than that
of unit Jqd.
Jgs GREENSTONE (Probably Lower to Middle Jurassic metamorphic age)--
The basic metavolcanic rocks of this unit form small, isolated
hills along the eastern edge of the map area near the Susitna
River. The typical greenstone is a dark greenish gray, fine
grained, generally structureless rock. Original rock-forming
minerals were pyroxene, amphibole, and plagioclase (andesine to
labradorite) which more or less altered to chlorite, epidote,
serpentine, calcite, and minor sericite and quartz. The prox-
imity of the amphibolite terrane (unit Jam) strongly suggests
that the metavolcanic greenstones of the present unit represent
a low-grade facies of the same metamorphism which produced the
amphibolite. The relative position of the greenstone within
the northeasterly structural trend of the Talkeetna Mountains
suggests that the greenstone was probably derived from the
Talkeetna Formation (unit Jtk) or, possibly, from either the
upper Paleozoic volcanogenic sequence (unit Pzv) or the Upper
Triassic basaltic sequence (unit lRv).
19
Jps PELITIC MICA SCHIST (Probably Lower to Middle Jurassic metamor-
phic age)--This rock occurs only in the southwestern corner of
the map area near the headwaters of Willow Creek. The schist
is medium to dark gray, medium grained, with uniform lithology
throughout its exposure area. Its ubiquitous mineral consti-
tuents are quartz, muscovite, albite, chlorite, chloritized
crystals of garnet and subordinate biotite. Very thin laminae
of carbonaceous material occur sparsely. Small open folds and
crenulations form an incipient slip cleavage at a large angle
I
to the primary schistosity. Numerous thin veins and stringers
of hydrothermal quartz occur throughout the schist. Detailed
petrographic descriptions of the mica schist are given in Ray
(1954) .
The present mineralogy of the schist is indicative of the
greenschist metamorphic facies of Turner (1968). However, it is
probably retrograde from higher metamorphism, possibly the amphi-
bolite facies. Evidence for this is the chloritized garnet and
biotite crystals and the sparse mineral outlines consisting of
chlorite which probably are pseudomorphs after hornblende.
The age of the schist is imperfectly known, but, based on
regional geologic interpretations, the primary metamorphism is
considered to be Early to Middle Jurassic in age. Thus, the
schist and the amphibolite of unit Jam are interpreted to be
the products of the same metamorphism. The retrograde metamor-
phism is assumed to be of middle to Late Cretaceous in age and
20
related to an al pine-type oro'geny in the Talkeetna Mountains at
that time. However. the Late Cretaceous Arkose Ridge Formation,
which lies unconfonnably on the schist, has not been affected
by this retrograde metamorphism. The three potassium-argon age
determinations, measured on muscovite from the schist (map nos.
33-35, table 1), yielded obviously reset Paleocene ages.
The parent rock of the schist is unknown because no pelitic
rocks of comparable thickness (the schist is at least several
hundred meters thick) are known to occur in the pre-Middle
Jurassic rocks of the Ta 1 keetna t1ountains.
Jpmu PLUTONIC AND METAMORPHIC ROCKS, UNDIFFERENTIATED (Lower to Upper
Jurassic plutonic and metamorphic ages)--This unit consists of
an intricately intermixed mosaic of most of the previously dis-
cussed Jurassic metamorphic and plutonic rocks (units Jtr, Jgd,
Jgdm, Jqd, Jam, Jgs, and Jps). Within the terrane of the pres-
ent unit, the exposure area of an individual rock type is not
more than a few square kilometers. Two rock types, amphybolite
and sheared quartz diorite, comprise approximately 60 percent
of the terrane. Next in importance are sheared granodiorite
and associated migmatites. Subordinate amounts of pelitic mica
schist and greenstone also occur. Numerous apophyses of trond-
hjemite, as much as several meters thick. occur along the east-
ern edge of the terrane adjacent to the large trondhjemite
pluton (unit Jtr). All of these rocks are lithologically very
21
similar to their correlative map units, and they will not be
described here. At two localities, the sheared granodiorite
(unit Jgd) was mapped separately to show the proximity of
sheared Jurassic granitic rocks to the Late Cretaceous and
early Paleocene unsheared tonalite (unit TKt).
NORTHWESTERN TALKEETNA MOUNTAINS AND UPPER CHULITNA RIVER AREA
Sedimentary and volcanic rocks; rocks of each column occur in separ-
ate fault blocks.
Central and northern Talkeetna Mountains
~v BASALTIC METAVOLCANIC ROCKS (Upper Triassic)--This shallow water
marine unit consists of amygdaloidal metabasalt flows with very
subordinate amounts of thin interbeds of metachert, argillite,
metavolcaniclastic rocks, and marble (Smith and others, 1975).
Rocks of this unit have been mapped only in the northeast por-
tion of the map area. However, small blocks of the basaltic
rocks may occur within the complexly deformed late Paleozoic
volcanogenic sequence (unit Pzv) toward the southwest. The
basaltic rocks rest with angular unconformity on the late Paleo-
zoic volcanics (unit Pzv); the top of the basalts is unexposed.
The minimal thickness of the basaltic metavolcanic rocks is
800 m.
The individual metabasalt flows are as much as 10 m thick,and,
according to Smith and others (1975), display columnar jointing
and locally pillow structures. The typical metabasalt is dark
22
greenish gray, fine grained, and generally contains numerous
amygdules. Thin sections show the metabasalts to consist of
labrodorite, augite, and opaques in an intergranular or sub-
ophitic texture. Secondary minerals are chlorite, epidote,
clinozoisite, very subordinate allanite, sericite, and possibly
some kaolin. The amygdules consist of chlorite, silica, and
zeolites. The present mineralogy is probably the result of
deuteric alteration and low-grade regional metamorphism which
apparently did not reach the intensity of the greenschist facies
of Turner (1968).
From a marble interbed in upper Watana Creek (locality 1,
table 3), T. E. Smith (unpub. data, 1974) collected fossil speci-
mens which were identified and interpreted by K. M. Nichols and
N. J. Si1berling to be Halobia cf. H. symmetrica Smith. indicat-
ing a latest Karnian or early Norian age. Previously, Smith
(1974a) and Smith and others (1975) have correlated the basaltic
metavolcanic rocks of the present unit with the Amphitheater
Group of the central Alaska Range. Accordingly, the fossils
collected by T. E. Smith suggest that the Amphitheater Group
is younger than,and thus not correlative with the lithologically
very similar Nikolai Greenstone of pre-late Karnian age in
eastern Alaska (Jones and others. 1977).
Pzv BASALTIC TO ANDESITIC METAVOLCANOGENIC ROCKS (Pennsylvanian(?)
and Early Permian)--Rocks of this unit occur in a northeast-
trending belt across the center of the Talkeetna Mountains, and
23
they form an interlayered heterogeneous, dominantly marine
sequence over 5,000 m thick. The base of the sequence is
nowhere exposed, and the contact with the overlying Triassic
metabasalts is an angular unconformity. The metavolcanogenic
sequence consists dominantly of metamorphosed flows and tuffs
of basaltic to andesitic composition, and of coarse-to fine-
grained metavolcaniclastic rocks with clasts composed chiefly
of mafic volcanic rocks. Mudstone, bioclastic marble (mapped
and described separately as unit Pls), and dark-gray to black
phyllite are subordinate. The various rock types of the sequence
form conformable but lenticular units of limited areal extent.
The crudely layered and poorly sorted metavolcaniclastic units
have thicknesses in excess of 1,000 m, and the thickness of the
phyllites ranges from a few meters to several hundred meters.
The whole sequence has been tightly folded and complexly faulted,
and the rocks have been regionally metamorphosed into mineral
assemblages mostly of the greenschist and the prehnite-pumpel-
lyite facies, but locally along Tsisi Creek of the amphybolite
facies of Turner (1968). Detailed petrographic descriptions
of these rocks were given by Csejtey (1974).
The age of the metamorphism ;s uncertain. The most inten-
sive metamorphism in the mapped area probably took place in
Early to Middle Jurassic time, contemporaneously with the
development of the amphibolite terrane (unit Jam). Subsequent
24
but less severe metamorphism, primarily shearing, occurred
probably in middle to Late Cretaceous time during the alpine-
type orogenic deformation of the Talkeetna Mountains (see
discussions in Structure and Tectonics sections).
The composition and lithologic character of the metavol-
canogenic sequence strongly suggest that this sequence is a
remnant of a complex volcanic arc system (Csejtey, 1974, 1976).
Fossil evidence (see description of unit Pls) from a marble
interbed near the top of the sequence indicates an Early Per-
mian age. However, because of the considerable thickness of
the sequence, its lowermost portion may be as old as Late
Pennsylvanian.
Pls MARBLE (Pennsylvanian(?) and Early Permian)--Forms lenticular
interbeds, as much as a few tens of meters thick, within the
basaltic to andesitic late Paleozoic metavolcanogenic sequence
(unit Pzv). Most of the rock is light gray to white, medium
to coarse grained, thick-bedded to massive marble, but some less
metamorphosed varieties also occur. Still discernible organic
remains and bedding features indicate that the marble inter-
beds were derived from bioclastic limestone which probably was
deposited by high energy currents on shallow banks of limited
areal extent. A number of the marble interbeds contain poorly
preserved and generically unidentifiable crinoid columnals,
brachiopods, bryozoans, and rarely corals (see table 3) of
25
late Paleozoic or probable late Paleozoic ages. However, one
of the marble interbeds near the top of the sequence (locality
8, table 3) yielded well-preserved brachiopods and crinoid
columnals which were identified and interpreted by J. T. Dutro,
Jr. (Csejtey, 1976) to be late Early Permian, that is, late
Leonardian to early Guadalupian in age. The regional correla-
tion of these rocks and that of the late Paleozoic metavo1cano-
genic sequence (unit Pzv) has been previously discussed by
Csejtey (1976).
Northern Watana Creek area
Js SEDIMENTARY AND VOLCANIC ROCKS, UNDIVIDED (Upper Jurassic)--These
rocks only occur in a small, apparently tectonic sliver along
the northern edge of the map area. They comprise a section of
intercalated argillite and graywacke, pebble conglomerate, and
flows and dikes of andesitic to 1atitic feldspar porphyry. Some
of these rocks are sheared but some, mostly the pebble conglom-
erates, are not sheared.
The argillite and fine-grained graywacke are thinly to mod-
erately thickly bedded and generally are dark gray. However,
dark-greenish-gray varieties also occur, suggesting the presence
of volcanic ash or fine-grained tuffaceous material. The con-
glomerates are massive, and the well-rounded to subrounded peb-
bles consist chiefly of unmetamorphosed andesite, latite, and
26
subordinate amounts of dacite. A minority of the pebbles are
composed of dark-gray argillite and white quartz. The feldspar
porphyry is dark gray, with flow alined phenocrysts of zoned
andesine and oligoclase as much as 1 cm long, and some horn-
blende and biotite, in -an aphanitic matrix.
An argillite bed at the top of the 5,053-ft hill in the
Healy A-2 quadrangle, just north of the present map area,
yie1ded well-preserved fossils of Buchia rugosa (Fischer),
indicating a Late Jurassic age for these rocks (D. L. Jones,
oral commun., 1977). On the basis of lithology and age, the
rocks of the present unit are considered to be the westernmost
occurrence of the Gravina-Nutzotin terrane of Berg and others
(1972) .
Northwest Talkeetna Mountains
Kag ARGILLITE AND LITHIC GRAYWACKE {Lower Cretaceous)--These rocks
occur in a monotonous, intensely deformed flyschlike turbidite
sequence, probably severa1 thousand meters thick, in the north-
west part of the mapped area, north of the Talkeetna thrust
fault. The-whole sequence has been compressed into tight and
isoclinal folds and probably has been complexly faulted as well.
The rocks are highly indurated, and many are sheared and per-
vasively cleaved as a result of low-grade dynamometamorphism,
the intensity of which is only locally as high as the lowermost
portion of the greenschist metamorphic facies of Turner (1968).
27
t
Most of the cleavage is probably axial plane cleavage. Neither
the base nor the top of the sequence is exposed and, because of
the intense deformation, even its minimal thickness is only an
estimate.
The argillite is dark gray or black. Commonly it contains
small grains of detrital mica as much as 1 mm in diameter.
Because of the dynamometamorphism, in large areas the argillite
is actually a slate or fine-grained phyllite. Thin sections
show that some of the argillites are derived from very fine
grained siltstone and that they contain considerable carbona-
ceous material.
The typical lithic graywacke is dark to medium gray, fine
to medium grained, and occurs intercalated with the argillite
in graded beds ranging in thickness from laminae to about 1.5 m.
The individual graywacke beds are not uniformly distributed
throughout the whole sequences of which they comprise about 30
to 40 percent by volumes but tend to be clustered in zones 1
to 5 m thick. Thin sections of graywacke samples show them to
be composed of angular or subrounded detrital grains of lithic
fragments~ quartz, moderately fresh plagioclase, and some,
generally altered s mica in a very fine grained matrix; euhedral
opaque grains~ probably authigenic pyrite, are present in most
thin sections. The lithic fragments consist in various propor-
tions of little altered, fine-grained to aphanitic volcanic
rocks of mafic to intermediate composition; fine-grained, weakly
foliated low-grade metamorphic rocks; chert; and some fine-
28
· grained unmetamorphosed sedimentary rocks possibly of intrafor-
mational origin. No carbonate grains were seen. The matrix
constitutes about 20 to 30 percent of the rock by volume, gen-
erally contains some secondary sericite and chlorite, and, in
the more metamorphosed rocks, biotite and possibly some
amphibole.
Analyses of paleocurrent features. such as small-scale
cross-stratification. found in several exposures near the west-
ern edge of the mapped area, suggest that depositional currents
came from the east or northeast (A. T. Ovenshine. oral commun.,
1974).
Because fossils are extremely sparse. the exact age of the
argillite and lithic graywacke sequence is imperfectly known.
A poor specimen of Inoceramus Sp. of Cretaceous age was found
just west of the map area between the Chulitna and Susitna Rivers,
and a block of Buchia-bearing limestone of Valanginian age was
found in float near Caribou Pass in the Healy quadrangle north
of the mapped area (D. L. Jones, oral commun., 1978).
Northwestern Talkeetna Mountains
lRvs METABASALT AND SLATE (Upper Triassic)--Shallow water marine,
interbedded sequence of amygdaloidal metabasalt flows and slate,
found only in two allochthonous klippen near the northwest cor-
ner of the mapped area. The sequence is tightly folded, along
with the underlying Cretaceous rocks (unit Kag), and ;s slightly
metamorphosed and unevenly sheared. The basalt and slate are
29
intercalated in approximately equal proportions in individual
units as much as 15 m thick.
The metabasalt is dark greenish gray, aphanitic, with num-
erous amygdules. In thin sections the primary minerals are
twinned labradorite, augite, and opaques which probably are,
for the most part, ilmenite. Secondary minerals are chlorite
(much of it after glass), epidote, clinozo;site, minor zoisite,
calcite, leucoxene, very minor sericite, very fine grained
felty amphibole (probably uralite after augite), and possibly
some very subordinate albite. The original texture was inter-
sertal and subophitic. The amygdules consist of chlorite, zeo-
lites (primarily prehnite), quartz, and some feldspar.
The slate is dark gray to black. Thin sections show that
some of the rock is fine-grained metasiltstone. All of the
rocks contain considerable carbonaceous material and some amounts
of fine-grained, secondary sericite. Secondary biotite ;s pre-
sent in some of the slates.
The secondary mineral assemblages suggest that, in addi-
tion to deuteric alteration, the metabasalt and slate sequence
underwent very low grade regional metamorphism.
The metabasalt and slate sequence has been dated in the
Healy quadrangle, north of the present map area, near the East
Fork of the Chulitna River where D. L. Jones and N. J. Silberling
(oral commun., 1977) found upper Norian fossils of Monotis sub-
circularis and Heterostridium sp. in slightly metamorphosed
30
argillaceous beds. Thus. the age of the present sequence is
similar to. and the lithology of its basalt is identical to,
that of the Upper Triassic metabasaltic sequence (unit IRv)
in the northeast Talkeetna Mountains. These two rock sequences
may represent different facies, brought closer by thrusting.
of the same geologic terrane.
Upper Chulitna River area
DSga GRAYWACKE, ARGILLITE, AND SHALE (Silurian(?) to Middle Devonian)
--These rocks occur in an apparently allochthonous tectonic
block along the western side of the Chulitna Valley and com-
prise a poorly and inaccessibly exposed, complexly deformed
and sheared sequence. As a result, the sequence is poorly known;
it was briefly examined in outcrop only along Long Creek. There
the component rocks are medium to dark gray, sheared and tightly
folded with vertical dips, and occur intercalated in beds as
much as 1 m thick. The graywackes are fine grained and appear
to contain some volcanogenic detritus. Reconnaissance field
checking by D. L. Jones (oral commun., 1977) further to the
north indicates that the sequence also includes some chert,
cherty tuff. and phyllite.
In Long Creek, two fossiliferous limestone beds (mapped
and described separately as unit DSls) were found; they prob-
ably are in depositional contact with, and thus date. the envel~
oping unfossi1iferous clastic rocks. It is possible, however,
that some of the limestone contacts are tectonic and that some
31
of the enveloping rocks are of a different age.
DSls LIMESTONE (Silurian(?) to Middle Devonian)--Mass;ve to thick-
bedded. medium-gray. fine-grained, moderately sheared bioclastic
limestone. probably formed in patch reefs. It occurs at three
separate localities, in apparent depositional interbeds as much
as 20 m thick, within fine-grained clastic rocks (unit DSga).
Of the two limestone beds in Long Creek. one yielded fossils
of Devonian, probably Middle Devonian, age, the other of Silurian
or Devonian age (map nos. 12. 13, respectively, table 3). The
fossils also indicate shallow marine deposition. The types
of fossils and the characteristics of the host limestones and
the enveloping clastic rocks suggest deposition along an ancient
continental margin. These continental margin-type deposits
crop out only about 6 km to the southeast of Upper Devonian
ophiolitic rocks (unit Dbs) that are indicative of ocean floor
deposition. The proximity of these rocks that are close in age
but different in depositional environment is additional evidence
for large-scale Alpine-type orogenic deformation in south-
central Alaska (Csejtey and others, 1977; Jones and others.
1978).
Upper Chulitna River area
Jta CRYSTAL TUFF, ARGILLITE, CHERT, GRAYWACKE, AND LIMESTONE (Lower
to Upper Jurass;c)--Sha1low to moderately deep marine sequence.
tightly folded and internally faulted, at least several thou-
sand meters thick. These rocks are interpreted to occur in a
32
thrust block along the western slope of the upper Chulitna
Valley. Four-fifths of the sequence is comprised of the mas-
sive, cliff-forming crystal tuff, while the remaining rocks
form only a narrow outcrop belt along the western margin of
the map unit. The contact between these two groups of rocks
may be tectonic.
The crystal tuff is light to dark gray~ locally with a
greenish tint, and weathers to various shades of brown. It is
massive with obscure rhythmic laminations and thin bedding.
The tuff is composed of abundant small feldspar crystals
(albite?) set in a very fine grained matrix of devitrified vol-
canic glass in which some shards can be recognized. Sparse
but unidentifiable fragments of radiolaria were also found.
A thin interbed of volcaniclastic sandstone yielded the follow-
ing fossils: Arctoasteroceras jeletskyi Frebo1d, Paltechioceras
(Orthechioceras?) sp., and Weyla sp. (Jones and others, 1978;
fossil locality in Silber1ing and others, 1978). According to
R. W. Imlay (written commun. to D. L. Jones, 1976), these fos-
sils indicate a late Sinemurian age.
The argillite, chert, graywacke, and limestone occur inter-
bedded in various proportions in individual units as much as
several tens of meters thick. The argillite and chert are dark
gray to black; the graywacke is medium to dark gray, very fine
33
to medium grained, locally with graded bedding. The limestone
is medium gray, generally phosphatic, in part sandy, locally
is associated with limy siltstone and conglomerate; forms
blocks and lenticular beds as much as several kilometers in
extent. Some of the chert beds yielded radiolaria of
late Kimmeridgian or early Tithonian age (Late Jurassic), and
at five different localities, the limy rocks yielded Early
Jurassic ammonite faunas of early Sinemurian age (Jones and
others, 1978; fossil localities in Silberling and others, 1978).
Probably these Lower and Upper Jurassic rocks originally formed
a coherent stratigraphic sequence which subsequently was dis-
rupted by folding and faulting.
Ohio Creek area
Dsb SERPENTINITE, BASALT, CHERT, AND GABBRO (Upper Devonian)--Tecton-
ically intermixed assemblage that forms a northeast-trending
belt of apparent thrust slivers in the northwest corner of the
mapped area. Sheared serpentinite is the most abundant rock
type; the remaining component rocks occur in various proportions
in lenticular and podiform tectonic blocks as much as several
hundred meters in extent. Many chert lenses occur intercalated
with basalt flows which locally show poorly preserved pillow
structures. Rocks of this map unit have been previously de-
scribed and interpreted as a dismembered ophiolite assemblage
by Clark and others (1972) and by Jones and others (1978).
34
The serpentinite is dark gray to dark greenish gray,
always sheared, and consists almost entirely of clinochrysotile
and lizardite with subordinate brucite, talc, and chromite.
Sparse relict olivine crystals and a bastite texture suggest
that the serpentinite originally was a pyroxene-olivine ultra-
mafic rock.
Basalt is dark gray, aphanitic to fine grained with a few
phenocrysts, as much as 4 mm in maximum dimension, of altered
plagioclase, pyroxene, and olivine. The rock is locally vesic-
ular or amygdaloidal and generally is fragmental; many of the
fragments are palagonite. Some of the vesicles and amygdules
are concentrated along spherical surfaces which may be parts
of pillow structures. Depositionally intercalated marine chert
beds further indicate that the basalts were formed as submarine
flows.
The chert is generally red, but reddish-brown and greenish-
gray varieties also occur. It is commonly in beds a few milli-
meters to a few centimeters in thickness, and contains abundant
radiolaria.
The gabbro is medium to dark greenish gray, fine to coarse
grained, and ;s composed of altered plagioclase, pyroxene,
olivine, and opaques. Compositional layering, interpreted to
be cumulate textures, is common, and the layers range in thick-
ness from a few millimeters to a few centimeters. The best
35
exposed gabbro occurs in a lens about 100 m thick and about 1
km long on the ridge north of the unnamed northern branch of
Shotgun Creek.
Age determinations of radiolaria and conodonts in chert
samples from eight separate localities reliably indicate a Late
Devonian (Famennian) age for the ophiolitic rocks (Jones and
others, 1978; Silberling and others, 1978).
Long Creek area
1Rr RED BEDS (probably Upper Triassic)--Red sandstone, siltstone,
argillite, and conglomerate similar to the red beds of unit
J1Rrs. Clasts of gabbro, serpentinite, and fossiliferous Per-
mian(?) limestone are present in these rocks but have not been
identified in rocks of unit J1Rs. Also, a thin conglomerate
bed containing angular clasts of rhyolite is locally present at
the base. These rocks lie with depositional unconformity on
late Paleozoic, possibly Triassic, and older strata in the map
area. Just north of the map area, the red beds rest on Lower
Triassic limestone (Jones and others, 1978). The red beds lack
fossils and, therefore, have not been dated, but they are assumed
to be equivalent in age to the Upper Triassic red beds of unit
J1Rrs (Jones and others, 1978).
pzsv VOLCANOGENIC AND SEDIMENTARY ROCKS, UNDIVIDED (Upper Devonian to
Lower Perrnian)--Heterogeneous intercalated sequence of green;sh-
gray to black tuffaceous chert, lesser amounts of maroon volcanic
36
mudstone, breccia composed largely of basaltic detritus, lami-
nated flyschlike graywacke and shale, and large lenses of 1ight-
gray, thick-bedded limestone. Fossils from the thick-bedded
limestone are Early Permian in age; brachiopods from the con-
glomerate are also of Early Permian age; and fossils from the
chert are Devonian and Carboniferous, but some poorly preserved
fossils may possibly, though not likely, be as young as Triassic
(Jones and others, 1978). The stratigraphic and structural
relations between these diverse rocks are obscured by abundant
folds and poor exposures. A detailed discussion of these rocks
is given by Jones and others (1978), and fossil localities are
shown in Silberling and others (1978).
Ohio Creek area
J1Rs RED AND BROWN SEDIMENTARY ROCKS AND BASALT, UNDIVIDED {Upper
Triassic and Lower Jurassic)--The basal part of this unit con-
sists of a red-colored sequence 9f sandstone, siltstone, argil-
lite, and conglomerate, with a few thin interbeds of brown fos-
siliferous sandstone, pink to light-gray dense limestone, and
intercalated massive basalt flows. This red bed sequence grades
upward into highly fossiliferous brown sandstone, which in turn
grades upward into brownish-gray siltstone with yellowish-brown
limy concretions.
Clasts in the red beds are dominantly basalt grains and
37
pebbles which probably were derived from basalt flows of unit
lRlb that lies unconformably below the red beds and from massive
basalt flows within the red bed sequence. Subordinate amounts
of the clasts consist of white, in part foliated, metaquartzite
pebbles; flakes of white mica which, along with the metaquartz-
ite, must have been derived from an unidentified siliceous
metamorphic terrane; and red radiolarmnchert pebbles and grains,
which probably were derived from the ophiolitic rocks of unit
Dsb. No other clasts that can be identified as coming from
the ophiolitic rocks have been recognized.
Fossils from the limestone and the overlying brown sand-
stone are of Upper Triassic age, and those from the yellowish-
brown limy concretions are of Upper Triassic and Lower Juras-
sic age.
Detailed discussions of both the red and brown beds are
given by Jones and others (1978), and fossil localities are
shown in Silberling and others (1978).
lRlb LIMESTONE AND BASALT (Upper Triassic)--Interlayered sequence of
limestone, partly recrystallized to marble, and flows of altered
amygdaloidal basalt. Individual units are as much as several
tens of meters thick. These rocks occur in a complexly faulted
zone in the northwest corner of the mapped area.
The limestone is medium gray, massive to thick bedded,
but locally it has altered to fine-to medium-grained marble.
38
It contains sparse fragments of poorly preserved corals and
thick-shelled Megalodontid{?) bivalves up to 20 cm in length.
A single specimen of Spondylospira sp.~ in conjunction with
the Megalodontid bivalves, suggests a Norian age for the sequence
(Jones and others t 1978; fossil localities shown in Si1berling
and others, 1978).
The amygdaloida1 basalt is dark gray to greenish gray,
aphanitic, with numerous amygdu1es. Locally, it displays wel1-
developed pillow structures. Primary rock-forming minerals are
fine-grained labradorite, titanium-rich augite, and opaques in
an originally interserta1 or subophitic texture. The original
mineral assemblage has been more or less altered to an aggre-
gate of chlorite (much of it after glass), epidote, calcite,
sericite~ and some zeolite, probably prehnite. The amygdu1es
consist of chlorite, calcite, prehnite, and minor quartz. Most
of the secondary minerals are probably the result of deuteric
alteration, but some might be the product of very low-grade
regional metamorphism. Fifteen chemical analyses of least
altered basalt samples indicate that the basalts are somewhat
low in silica (normalized Si0 2 contents average 46.7 percent
by weight, ranging from 43.7 to 48.7 percent)~ high in alkalis
(normalized Na 20 contents average 3.06 percent by weight, rang-
ing from 1.3 to 5.2 percent; and normalized K20 contents aver-
age 0.47 weight percent, ranging from 0.07 to 1.5 percent),
39
and are high in titanium (normalized Ti0 2 contents average 3.8
weight percent, ranging from 2.5 to 5.0 percent). The chemistry
and mineralogy suggest that these basalts had alkali affinities
prior to alteration.
The fossils and the lithologies of the limestones and the
basalts indicate shallow water marine deposition. The probable
alkali affinity of the basalts further suggests that they either
were part of an ocean island shield volcano, perhaps associated
with a barrier reef, or that they were formed on a continental
margin.
Upper Copeland Creek area
KJs ARGILLITE, CHERT, SANDSTONE, AND LIMESTONE (Upper Jurassic and
Lower Cretaceous)--This unit consists of dark-gray argillite,
dark-gray to greenish-gray bedded chert, thick-bedded sandstone,
thin-bedded gray sandstone, and rare thin beds of shelly lime-
stone. Both Upper Jurassic and Lower Cretaceous radiolarias
were obtained from the chert. The thick-bedded sandstone con-
tains abundant fragments of Inoceramus sp. of Hauterivian to
Barremian age, and some of the 1 imestone beds contain Buchi,a
sublaevis of Valanginian age. Some of the thin-bedded sandstone
contains abundant detrital white mica and may be as young as
A"lbian (mid-Cretaceous). Thicknesses and the stratigraphic
relations within these rocks and with adjacent rocks are unknown
40
because of complex folding and faulting and poor exposures. A
more detailed discussion of these rocks is given by Jones and
others (1978). and fossil localities are shown in Silberling
and others (1978).
41
Structure
The rocks of the Talkeetna Mountains region have undergone complex
and intense thrusting, folding, faulting, shearing, and differential
uplifting with associated regional metamorphism and plutonism. At least
three major periods of deformation are recognized: a period of intense
metamorphism, plutonism, and uplifting in the late Early to Middle
Jurassic, the plutonic phase of which persisted into Late Jurassic; a
middle to Late Cretaceous alpine-type orogeny, the most intense and impor-
tant of the three; and a period of normal and high-angle reverse faulting
and minor folding in the middle Tertiary, possibly extending into the
Quaternary.
Most of the structural features in the Talkeetna Mountains region
are the result of the Cretaceous orogeny which produced a pronounced
northeast-southwest-trending structural grain of the region. The verg-
ence of this structural grain is steeply to moderately toward the north-
west, but across the Chulitna Valley in the northwest part of the map
area, it abruptly reverses toward the southeast with steep attitudes.
This Cretaceous deformation ;s most intense in the central and northwest-
ern part of the map area, and it rapidly decreases toward the southeast.
The complex fault pattern along and near the southern edge of the Tal-
keetna Mountains is part of the late Cenozoic Castle Mountain-Caribou
fault systems, consisting chiefly of high-angle reverse and normal faults
of probably local significance.
Evidence for the Jurassic deformation is provided by the post-
Talkeetna Formation major unconformity and the apparently coeval regional
42
metamorphism. up to the amphibolite grade. and associated plutonic rocks
(all the Lower to Middle Jurassic metamorphic and plutonic units). The
higher crustal level manifestation of this Jurassic tectonic event was
regional uplift and cons~quent rapid denudation of the intruded epizonal
plutons.
Complex folding produced by the Cretaceous orogeny is especially
pronounced in the areas northwest of the belt of Jurassic metamorphic
and plutonic rocks. The folds are chiefly tight or isoclinal, with ampli-
tudes of several hundred to several thousand meters. The limbs are gener-
ally sheared out or faulted out. As a result. no individual beds can be
traced in the field for more than a few kilometers. Many of the large
folds, especially in the Cretaceous argillites and graywackes (unit Kag).
have a well-developed axial plane slaty cleavage. Fine-grained sericite
and biotite are commonly developed along these cleavages. The folding
must have taken place in several episodes during the orogeny because thrust
faults not only truncate folds within both the upper and lower plates but
are themselves folded. The folded thrusts are especially evident in the
Chulitna area where, in contrast to the regional northwest vergence, the
axial planes of the folds steeply dip toward the northwest.
Most prominent of the Cretaceous faults is the Talkeetna thrust which
has placed Paleozoic, Triassic. and, locally, Jurassic rocks over Creta-
ceous sedimentary rocks across the whole map area. The thrust is gener-
ally poorly exposed except near the Lower Talkeetna River. There it
43
dips steeply toward the southeast. Another thrust, the one delineating
the klippe of rocks of unit TRvs, has been sharply folded. The thrusts
in the northwest corner of the map area are very complex, also have been
intensely folded, and are more numerous than could be shown on the present
map. A number of them are not fully understood, and thus their subsurface
configuration is speculative. It is certain, however, that these thrusts
stack and bring together on top of the Kag unit a wide variety of rock
sequences of different ages and depositional environment. The root zone
of all the thrusts in the northwest half of the map area is herein inter-
preted to be the Talkeetna thrust (see cross section).
Another Cretaceous feature is an intense shear zone, locally as much
as 25 kin wide, trending across the Talkeetna Mountains, parallel to, but
southeast of the Talkeetna thrust. Although not supported by any evi-
dence, it is possible that the shear zone marks a thrust zone of signi-
ficant displacement. (The center of this shear zone is shown as a postu-
lated thrust on the map.) The dips in the zone are generally southeasterly.
The shearing is penetrative, and its most spectacular result is that por-
tions of all the Jurassic plutonic rocks, including the Upper Jurassic
trondhjemite, have been transformed to catacl astic gnei ss. The 75 to
61 m.y. old Upper Cretaceous and lower Paleocene tonalite pluton (unit
TKt) truncates this shear zone and is not affected by it.
The age of the 'Cretaceous orogeny, or at least its major phase, is
rather well bracketed by stratigraphic evidence. The youngest rocks
involved are the Cretaceous argillites and graywackes (unit Kag) which
44
are as young as Valanginian or possibly even younger in age. A maximum
upper age bracket is provided by the late Paleocene granitic plutons,which
are structurally unaffected, and intrude the already folded and faulted
country rocks in the northwest half of the map area. Two of the Creta-
ceous thrusts, including the Talkeetna thrust, are actually intruded by
these plutons. A slightly older upper age bracket is provided by the pre-
viously discussed 61 to 75 m.y. old tonalite pluton (unit TKt) that cuts
and is unaffected by the prominent shear zone in the central Ta1keetnas.
Thus, the most important orogenic deformation in the Talkeetna Mountains
region must have taken place during middle to Late Cretaceous time. Such
an age assignment for the orogeny is further supported by potassium-argon
age determinations of 88 and 91 m.y. for the serpentinite protrusions in
the southwest corner of the map area (unit Kum).
The dominant features of the middle Tertiary to Quaternary deforma-
tion are the already mentioned Castle Mountain-Caribou fault systems,
along which the southern Talkeetna Mountains have been uplifted locally
as much as 2.800 m (Detterman and others, 1976). The only other features
of this Cenozoic deformation recognized within the map area are the two
poorly exposed normal faults in the Chulitna River valley (see map and
cross section). In addition to field observations, the existence of these
faults is also supported by gravity data (R. L. Mor;n, oral commun., 1977;
N. B. Harris, oral commun., 1977). No other Cenozoic faults, or any other
faults with obvious Recent movement, were observed within the map area.
45
Tectonics
The Talkeetna Mountains and adjacent areas are part of the dominantly
allochthonous terrane of southern Alaska. Previously, this terrane has
been interpreted to have developed by accretion of allochthonous conti-
nental blocks to the ancient North American plate (Richter and Jones,
1973; Csejtey, 1974) in late Mesozoic time (Csejtey, 1976; Jones and others,
1978). Although the exact number or even the extent of these allochthonous
blocks is still imperfectly known, they appear to have moved northward
considerable distances prior to their collision with the North American
plate. For one of the blocks in eastern Alaska (Wrangellia of Jones and
others, 1977), a probable northward movement of several thousand kilometers
has been shown by Hillhouse (1977). The results of the present investi-
gations and those of Jones and others (1978) not only lend credence to
the accretionary concept of southern Alaska but also provide additional
evidence for the time, method, and direction of emplacement.
One of the keys to the tectonic history of the Talkeetna Mountains
reg1on, and to southern Alaska as well, is the occurrence of the tecton-
ically emplaced diverse rock packages in the Chulitna area in the north-
west part of the map area. Most of the Triassic and Jurassic rocks there,
especially the Triassic red beds, do not occur anywhere else in Alaska,
and the fossil faunas and lithologic characteristics of these Mesozoic
rocks strongly suggest deposition in warm water at low paleolatitudes
(Jones and others, 1978). Furthermore, the pre-middle Cretaceous rocks
above the Talkeetna thrust, above the root zone of the Chulitna faults,
46
are either structurally part of the allochthonous Wrangellia terrane of
Jones and others (1977) or belong to a different terrane lying south (that
is outboard) of Wrangellia. Thus, all available evidence strongly indi-
cates that. with the exception of unit Kag, all pre-middle Cretaceous
rocks of the Talkeetna Mountains region are allochthonous, and, after
the collision of their parent continental blocks with the middle Creta-
ceous North American continent, they were thrust upon, that is obducted
onto the margin of the continent. In turn, the middle Cretaceous Alaskan
margin of the continental North American plate itself probably developed
by still earlier accretions (D. L. Jones, oral commun., 1977). The dis-
tance the allochthonous rocks of the Talkeetna Mountains region were
thruste~beyond the edge of the continent is not known with certainty,
but it must be at least several hundred kilometers. In accordance with
the present obduction concept. all the tectonic and depositional rock
assemblages normally associated with the continental upper plate of a
subducting system, especially trench deposits and volcanic arc rocks, are
now hidden by the overthrust rock masses. Possibly the small tectonic
sliver of Upper Jurassic sedimentary and volcanic rocks (unit Js) along
the Talkeetna thrust ;s the only exposed ,remnant of these hidden assem-
blages. As shown on the cross section, the main thrust along which most
movement presumably occurred is the Talkeetna thrust, and all other thrusts
northwest of it are interpreted to be slivers below it.
The northeast-southwest-trending compressional structural features.
that is the folding and thrusting. indicate a general northwestward
47
tectonic transport. This is further supported by the sharp character of
the suture zone in eastern Alaska, along which the allochthonous rocks
of southern Alaska, especially the Wrangellia terrane, are in contact
with the pre-middle Cretaceous North American continent. This suture
zone in eastern Alaska trends northwesterly and is devoid of the struc-
tural complexities of the Chulitna area. This part of the suture, the
part southeast of Paxson, which also coincides with the middle Tertiary
to Holocene Denali fault, is thus interpreted to have been a transform or
a wrench fault. In contrast, the great variety of tectonically juxta-
posed rock packages in the Chul itna area may be the result of "bulldozingll
by a large continental block drifting toward the northwest.
The age of this orogenic period of continental collision and sub-
sequent obduction is indicated by the age of its structural features,
which are discussed in the Structure section, to be middle to Late Creta-
ceous.
In summary, southern Alaska is interpreted to have developed geologi-
cally by the accretion of an 'indeterminate number of northwestward drift-
ing continental blocks to the North American continent. After collision,
at least parts of these blocks were thrust several hundred kilometers
onto the North American continent in middle to Late Cretaceous time. The
resulting structural features are truly alpine in character and compare
favorably with the classic structures of the Alps in their grandeur and
complexity.
48
A corollary of the present tectonic interpretation of southern Alaska
is that the present Denali fault, a middle Tertiary and younger feature
(Richter and Jones, 1973), has not played a significant role in the tec-
tonic development of southern Alaska. The eastern, that is strike-slip
portion of the Denali fault (Csejtey, 1976), may not have more than a few
tens of kilometers of total movement.
An interesting, but still unresolved, tectonic problem in the Tal-
keetna Mountains region is the shallow depth of the present Benioff zone
(Lahr, 1975). The 50-km contour (below sea level) for the upper surface
of the Benioff zone strikes northeasterly and ;s approximately below the
Jurassic trondhjemite batholith (unit Jtr). The 100-km contour, also
striking northeasterly, is located approximately under the northwest corner
of the map area. According to plate tectonic concepts, in conjunction with
a subducting system, the top of the undergoing slab should descend at
least 100 km below sea level for magma generation. It appears that in
the Talkeetna Mountains region there is not enough thickness of upper plate
for magma to form. For the Jurassic and older igneous rocks the problem
can be explained that these rocks are allochthonous and have been tecton-
ically cut off and transported away from their roots. However, for the
Upper Cretaceous and younger igneous rocks, this mechanism cannot be
invoked. Two explanations are possible. First, that the present shallow
position of the Benioff zone is a relatively recent phenomenon achieved
by shearing and cutting away of the base of the upper plate by the down-
going slab. Perhaps the development of the present Denali fault and
49
other middle Tertiary and younger faults of southern Alaska could be
related to this process. The other possibility is that all the Upper
Cretaceous and younger igneous rocks of the Talkeetna Mountains region
were formed in a thin upper plate by exceptionally high heat flow of
unknown origin and mechanism (atectonic anatexis by Reed and Lanphere.
1974).
50
References cited
Anderson, R. E., 1969, Geology and geochemistry of the Diana Lakes area,
western Talkeetna Mountains, Alaska: Alaska Oiv. Mines and Geology
Geol. Rept. 34, 27 p.
Barnes, F. F., 1962, Geologic map of lower Matanuska Valley, Alaska:
U.S. Geo1. Survey Misc. Geol. Inv. Map I-359.
Berg, H. C., Jones, O. L., and Richter, O. H., 1972, Gravina-Nutzotin
belt-~Tectonic significance of an upper Mesozoic sedimentary and
volcanic sequence in southern and southeastern Alaska, in
Geological Survey research 1972: U.S. Geol. Survey Prof. Paper
800-0, p. 01-024.
Buddington, A. F., 1959, Granite emplacement with special reference to
North America: Geo1. Soc. America Bull., v. 70, p. 671-747.
Clark, A. L., Clark, S. H. B., and Hawley, C. C., 1972, Significance
of upper Paleozoic oceanic crust in the Upper Chulitna district,
west-central Alaska Range, in Geological Survey research 1972:
U.S. Geol. Survey Prof. Paper 800-C, p. C95-Cl01.
Csejtey, Bela, Jr., 1974, Reconnaissance geologic investigations in the
Talkeetna Mountains, Alaska: U.S. Geo1. Survey Open-file Rept.
74-147, 48 p.
1976, Tectonic implications of a late Paleozoic volcanic arc in --
the Talkeetna Mountains, south-central Alaska: Geology, v. 4,
p. 49-52.
51
Csejtey, 8~la, Jr., Nelson, W. H., Eberlein. G. D., Lanphere, M. A.,
and Smith, J. G., 1977, New data concerning age of the Arkose
Ridge Formation, south-central Alaska, ~ 8lean, K. M., ed., The
United States Geological Survey in Alaska: Accomplishments during
1976: U.S. Geo1. Survey Circ. 751-B, p. B62-864.
Oetterman, R. L., Plafker, George, Tysda1, R. G., Hudson, Travis, 1976,
Geology and surface features along part of the Talkeetna segment
of the Castle Mountains-Caribou fault system, Alaska: U.S. Geol.
Survey Map MF-738.
Oetterman, R. L., Reed, B. L., and Lanphere, M. A., 1965, Jurassic
plutonism in the Cook Inlet region, Alaska, ~ Geological Survey
research, 1965: U.S. Geol. Survey Prof. Paper 525-0, p. 016-021.
Evernden, J. F., Curtis, G. H., Obradovich, J. D., and Kistler, R. W.,
1961. On the evaluation of glauconite and illite for dating sedi-
mentary rocks by the potassium-argon method: Geochim. et Cosmochim.
Acta, v. 23, p. 78-99.
Grantz, Arthur, 1960a. Geologic map of the Talkeetna Mountains A-l
quadrangle and the south third of the Talkeetna Mountains B~l
quadrangle, Alaska: U.S. Geol. Survey Misc. Geol. Inv. Map 1-314,
scale 1:48,000.
______ 960b, Geologic map of the Talkeetna Mountains A-2 quadrangle,
Alaska and the contiguous area to the north and northwest: U.S.
Geol. Survey Misc. Geol. Inv. Map 1-313, scale 1:48,000.
52
Grantz. Arthur. 1961a, Geologic map of the north two-thirds of Anchorage
0-1 quadrangle, Alaska: U.S. Geo1. Survey Misc. Geol. Inv. Map
1-343. scale 1:48,000.
__ 196"lb. Geologic map and cross sections of the Anchorage 0-2 quad-
rangle and northernmost part of the Anchorage 0-3 quadrangle.
Alaska: U.S. Geo1. Survey Misc. Geol. Inv. Map 1-342. scale
1 :48.000.
1964. Stratigraphic reconnaissance of the Matanuska Formation in --
the Matanuska Valley. Alaska: U.S. Geol. Survey Bull. 1181-1.
33 p.
Grantz. Arthur. Thomas. Herman. Stern, T. W .• and Sheffey. N. B., 1963,
Potassium-argon and lead-alpha ages for stratigraphically bracketed
plutonic rocks in the Talkeetna Mountains. Alaska, ~ U.S. Geo-
logical Survey Research 1963: U.S. Geo1. Survey Prof. Paper 475-B,
p. 856-B59.
Grantz, Arthur, and Wolfe, J. A .• 1961, Age of Arkose Ridge Formation,
south-central Alaska: Am. Assoc. Petroleum Geologists Bull., v.
45, p. 1762-1765.
Hillhouse. J. W., 1977, Paleomagnetism of the Triassic Nikolai Green-
stone, McCarthy quadrangle, Alaska: Canadian Jour. Earth Sci.,
v. 14, p. 2578-2592.
Jones. O. L., 1967. Cretaceous ammonites from the lower part of the
Matanuska Formation, southern Alaska: U.S. Geol. Survey Prof.
Paper 547, 49 p.
53
Jones, D. L., Silberling, N. J., Csejtey, Bela, Jr., Nelson, W. H.,
and Blome, C. D., 1978, Age and structural significance of the
Chulitna ophiolite and adjoining rocks, south-central Alaska:
U.S. Geol. Survey Prof. Paper. (in press).
Jones, D. L., Silberling, N. J., and Hillhouse, John, 1977, Wrangellia
--A displaced terrane in northwestern North America: Canadian
Jour. Earth Sci., v. 14, p. 2565-2577.
Lahr, J. C., 1975, Detailed seismic investigation of Pacific-North
American plate interaction in southern Alaska: New York City,
Columbia Univ., Ph.D. thesis, 141 p.
Ray, R. G., 1954, Geology and ore deposits of the Willow Creek mining
district, Alaska: U.S. Geol. Survey Bull. 1004, 86 p.
Reed, B. L., and Lanphere, M. A., 1974, Chemical variations across the
Alaska-Aleutian Range batholith: U.S. Geol. Survey Jour. Research,
v. 2, p. 343-352.
Richter, D. H., and Jones, D. L., 1973, Structure and stratigraphy of
eastern Alaska Range, Alaska: Am. Assoc. Petroleum Geologists Mem.
19, p. 408-420.
Rose, A. W., 1967, Geology of an area on the upper Talkeetna River,
Talkeetna Mountains quadrangle, Alaska: Alaska Div. Mines and
Minerals Geol. Rept. 32, 7 p.
I Silberling, N. J., Jones, D. L., Csejtey, Bela, Jr., and Nelson, W. H.,
1978, Interpretive bedrock geologic map of part of the Upper Chulitna
district (Healy A-6 quadrangle), Alaska Range, Alaska: U.S. Geol.
Survey Open-file Rept.
54
Smi~h, T. E., 1974a, Newly discovered Tertiary sedimentary basin near
Denali: Alaska Div. Geol. and Geophys. Surveys Ann. Rept., 1973,
p. 19.
______ 1 974b, Regional geology of the Susitna-MacLaren River area: Alaska
Div. Geol. and Geophys. Surveys Ann. Rept., 1973, p. 3-6.
Smith, T. E., Bundtzen, T. K., and Trible, T. C., 1975, Stratabound
copper-gold occurrence, northern Talkeetna Mountains, Alaska:
Alaska Div. Geo1. and Geophys. Surveys Misc. Paper 3, 7 p.
Turner, D. L., and Smith, T. E., 1974, Geochronology and generalized
geology of the central Alaska Range, Clearwater Mountains, and
northern Talkeetna Mountains: Alaska Div. Geo1. and Geophys.
Surveys Open-file Rept. 72, 11 p.
Turner, F. J., 1968, Metamorphic petrology, mineralogical and field
aspects: New York, McGraw-Hill, 403 p.
55
T.~I. I.--rot ••• lua-.c,oo .,. dot.ratoatloo. tro. tho
'hlk .. tno HouDtoln. ~uadr.n,l. .od tho aorthoro part of
tho o\llcho tal. 'l.uoduolle, o\taolt.
~O Calcuhtod
laO· o\rrod ., ....
~ HAp Locatloo • hld ••• loclt Illaarol (.,ol,ht totd (.Hllo" •
00. Lit. (HI Loo,. (W) t,,1 d.tod ,orCOllt) .t , .... , l.ferlRcl
1. 62°,,· SO" lUoU'"'' 7,.C,92 Gulllri Ilotttl 7.'4(21 6.ZI' 0.49 51.St.I.1 Tbtl uport
(.dl.dUnl
2. uo,,'n" U80 U'U" 15;l.CrU6 GUliod tor tto Itotltl 9.08UI I.S&3 0." 5"'1::.1.1 Thta uport
), nOu'za" IUoU'SO" u-I-n Grandlortu atotitl SS.ltl,1 Turllir .. d
Satth (1.741
4. 102°",'46" 14,°,.'20" Uo\Cr2 Groottl Itottu .... (2) 6.910 0.11 S6.)tl, I Tbtl u,ort
(odo .. UIU)
S. 'lOU·) .... 141°11'10" UASU.O Dtorttl oc lIornbllodl U6.6iS.1 Tur .. r ..d
1.,.,lb01l,. S.lth (19141
... 102°])')0" 14.°24'14" JUCr
'
Grantt. alottel S.)S (2) 4,461 0.60 n.6:!:.1.1 Tht. uPOrt
<.1l (ad ••• llttl)
0'1
61°28'11" ° 1. 149 29')0" lU5jHO gdlttu Hornblend. O.US(ll 0.4071 0.56 SO.4t.l •O TIlt. u,on
UOlS'24" ° •• 141 53'40" lU5jUII Andnttl Whot. rock 2.U8t.0.04S( 4) 1.1)7 0.)4 st.lt.1 ., TI>1o re,on
9. 61°11'28" 141°11')4" 13;1.C1 l0, QulCU Blotlt. I.U(Z) '1.19 0.91 1":t.4 .) TIIU uport
dtorlr.
Hornblende 0.590(2) 1.]65 0.61 U4!.4.6 TIlt • .. port
10. 61"10'4)" lUo U']'" llUU15 Trondbjo.lu 110ttu UI. st.4.1 Turoor ond
Salth (1914)
II. UO)4'H" 141 0 4l'U" nUelS6 Troodhj •• ttl Ilottu 146. st.4.) Turnlr .nd
Salth (1974)
11. nOIl'U" 149"46'n" 7l;l.Cr IOI Toodle. Ilotlu 1.48(2) 6.181 0.81 ,..8t.I ,6 Thh report
Il. ° n ,,'sa" 141° 4)'26" UUjS26 And .. teo Wholo Rock 0.84)(2) 0.6941 0.11 S6.l:t,2., TIIh repon
14. nOI9'Ol" 141°10'0." 6tAU Troodhj •• ttl Itott,. 6,21(21 1l.)J 0.91 14l:t,4. J TIl II uport
Ku.covlt. 9. nu) 1l.4g 0.91 IUt.4 ,4 TIlle uport
U. 61°21'12" 141°49'18" SUedt'" Granodtorlte atotlto 114 Grallll .,ul
oth ... (19631
Bornbt.ad. IUt.6 •0 Dott .. _ .... 4
otho .. (196))
See footnotes It end of tlbl.
T.ble l.-·Continued
itO Cal" .. luad
"2°-toGA,,: Arc.d .......
CQ-l~:l~ 'I1f..--
tUner"l {wel,ht total (aUl1on. Loc.tlon lidd 110. locll of ,.au) Iduao"e Kap dated puceot) nQ, Lat. (II) \.001' {WI t,pe '1'''. -----_.
11. 112"U' ~OM U80 0lo')5M S901Gd12. Q ... uu Ilotlta In ,,,.r,,de.. aDd
dlorl ... ntb .... (1961)
Il"tlta l1Gt,6 Oac.t.aIWA,4 804
otlleu (1'.165)
ILnUn 161 Crace I &Ad
otha .. (1961)
ll"rDblenil" 16lt.6 Oattaraa..an .. nd
othara (l9QU
18. 62"09'00" 149°11'10" lUC,1I1 Quarto UotlU 9.]] 9.201 O,J9 U.lt.l c.eju,. 191,
dlodLe
lIornbI. n4 .. 1.041(2) 9.869 o.n 64.6t,1 C .. jte,. 1914
19. 61"08'4/0" 149°18')0" 1:u.C,121 Too.Ute BLotlte 9.10 9.0H 0.11 6(o.4:!:.1 c..Jt." 1914
Hornblende 0.182(%) 0.1)11 0.18 h.)!'.2 Ca.Ju" 1914
(J1 ZO. 62%' 21" 1480 S9'44" JUCJ9S CranO<llor Lre
"-...I
!lotl ... 9.64(2) a.l0~ O.,}" 61.1!'.1., ttlLa rap">"t
Hornb&.n .... 1t I.OH( 2) 1.011 0.88 H.lt.2 •1 'I'M. r.~ort
21. 62°04'SI" IUoU'S8" 1)AC ll14 TrondhJemtte IIl0tlt. 9.10(2) 9.64) 0.88 67 .&±:,2.0 tb.la caport
22. 62"04'49" IUolO' 29" llACyllS t'C'oodllj •• U. MLUJCov1,. 9.91(2) 19.98 0.9) Int."'O 'nih ceport
1I0Ht .. 9,62(2) 14.", o,n ".41.].0 Thl. raport
2). 102°04']8" 1490 l1'I4 M llAC,94 TOAaUta alotlta 9.46(2) 8.S91 0.81 ,,,It.I ., tbla raporc
1I0CClb lend .. 0.1110(2) 0.8669 0.11 ".Gt,I •• tb.l. report
24. 61
o
S9'IS" 0 149 U'OO" lUCyllS GraaodlorLta MU:lcovlte 10.64(2) 10.21 0.12 61.2t.2 •O tbl. repoC't
IIhltU. 9.1>8(2) 9.02S O.bl 6i.0!'.2.0 tb.h ceport
2S. 61o i6'lI" 148°ill']8" n"C,91 Q ...... U Itotlt. a.l0(2) S.~1I4 0.83 61.4;t2.0 tbla report
dtorlu
Ilotnbl"nd .. 0.918(2) 0.9669 0.12 n.&±:,2.1 'nita repon
26. 61°Sb'"'' 14ao~I'04" JUCyl~b TroAdllJellUe Huat:ovLte ].4b(2) 6.080 0.b9 l2\l:t.l.9 fbl. rap...""t
21. ol"i\l')l" 14aQ u.'li" 1UCyl~9 Gr.-nodloc Lt. alotita 8.01>(2) 20.44 0.89 ",a!'.s .0 tilL. t.pyre.
~8 • ~lu49"l6n 149"14')0" GO.IG.40 t..."n411cd notnDl.!n~w:t O.lH(!) O.IUB 1).14 1l.1;t2,2 till. r.putt
See footnotes at en~ of table
Table 2.--Lead-alpha age determinations on zircon from southeastern part of
Talkeetna Mountains quadrangle, Alaska
f>1ap Location Apparent
no. Lat.(N} Long. (W) Field no. Rock type age (m.y.) References
15 62°21' 2211 147°49'18" 59AGzM58 Granodiorite 165+20 Grantz and others (1973)
16 62°21'1 ]'I 147°49'12" 59AGzM57 Granodiorite 125+15 Grantz and others (1973 )
DEPARTMENT Of THE INTERIOR
UNITED STATES GEOLOGICAL SURVEY
"_."H'''~'''' 0"" ...... ""' ....
~ ... =-.---"~-="': ,''''''
INl)fX TO GEOLOGIC ,MAPPING
RECONNAISSANCE GEOLOGIC MAP ANO GEOCHRONOLOGY, TALKEETNII MOUNTAINS QUAORIINGLf.
NORTHERN PART OF ANCHORAGE QUADRANGLE. AND SOUTHWEST CORNER Of HEIILY QUADRANGLE. ALASKA
&,10 Cui*.y, Jr" W.H. N.h •• , D,L. jail ••• N.J $llb.di".,
•. M. D.ol\, M.S. Marrl,. M.A, lOllphu •. 1.0, S",lth.
alld M, l. SllbuMOIl
1978
C(mRElATIOH 01" WAP VI'OITS
E);PLANAnON Of MAP SVMaotS
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~------\--;;t--~--
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<bt~ """"" e""' .. I .... ij ;~di" .. n "Pl~(_ ,I" """"" 1' .. .;(h",
of 4h~I.~t ",,,,,,,.",,,,,,,,,, j'l't''':~ coln:_. hr..-,I '.m, •• "n.
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~
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.......... t_, -'"O"'P"-, fltN _r .. MI , .... k~l~tod
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OPEN FILE REPORT
78-558A
SECTION E
ENVIRONMENTAL ASSESSMENT
SECTION E
ENVIRONMENTAL ASSESSMENT
TABLE OF CONTENTS
Item P~
INTRODUCTION E-l
SUMMARY OF CHANGES E-2
ENVIRONMENTAL SETTING E-3
Biological Characteristics E-3
Mamma 1 s -Moose E-3
Cultural Characteristics E-3
Archeological Resources E-3
ENVIRONMENTAL IMPACTS OF THE DEVIL CANYON -WATANA
HYDROPOWER PLAN E-5
Mammals -~1oose E-5
Archeological Resources E-6
Section 404(b) Evaluation E-6
Executive Order 11988 (Flood Plain) Evaluation E-6
RELATIONSHIP OF THE PROPOSED DEVELOPMENT TO LAND USE PLANS E-8
LITERATURE CITED E-10
i
INTRODUCTION
In the almost 4 years since the original environmental assessment
(EA) was prepared, much new information has been made available through
the efforts of various Federal and State agencies. Some of the infor-
mation would result in minor changes in the EA if incorporated. These
minor changes would not substantially alter the reader's perception
of the proposed project or its environmental impacts. Such information
has therefore not been incorporated in this supplement. Some of the
new information, however, could substantially alter the reader's per-
ception of the proposed project or its environmental impacts. This
type of new information has been summarized in this supplement. It
should be noted, however, that the information obtained to date ;s only
preliminary and lacks needed details and that additional biological and
social information remains to be gathered in the future in order to
complete an adequate and meaningful assessment of environmental impacts.
E-l
SUMMARY OF CHANGES
There is new biological information related to moose. In general,
moose occupy the upper Susitna River basin to a greater degree than
previously thought.
Also, archeological studies conducted by the Alaska District have
resulted in archeological finds of potentially significant cultural value.
As a result of this new information, the potential for additional
environmental impacts has been recognized, and the importance of pre-
viously identified impacts has been reevaluated. Impacts to moose will
probably be far more significant than previously believed. Impacts on
archeological resources could be potentially significant if not properly
mitigated.
A discussion of the recognition of the need for a Section 404(b)
evaluation has been added to address the requirements of the Federal
Water Pollution Control Act and the Clean Water Act. An evaluation of
flood plain considerations as per Executive Order 11988 has also been
added.
Land use is in a constant state of change because of the Alaska
Native Claims Settlement Act, the Federal Land Policy and Management
Act, and various other regulations related to wilderness. A short
update on these land use considerations has been added.
E-2
ENVIRONMENTAL SETTING
BIOLOGICAL CHARACTERISTICS
Mammals -Moose
Moose range throughout the entire Susitna River basin, and their
numbers in the basin have fluctuated widely since the early 1900's.
The population reached a peak in the early 1960's, then began a decline
that has continued to the present time. Factors contributing to the
decline have included loss of productive browse habitat as a result of
effective fire suppression over the past two decades, a rapid increase
in predator populations following cessation of control efforts in the
mid-1950's, and a number of severe winters with deep accumulations of
snow.
The preliminary movement data gathered thus far by the Alaska
Department of Fish and Game (ADF&G) indicate that moose from several
surround"ing areas migrate across or util ize the portion of the upper
Susitna River basin adjacent to the river during some portion of the
year. ADF&G recorded observations of 2,037 moose during the fall 1977
counts. Studies indicate that an observer generally sees between 43 to
68 percent of the moose in an area during an aerial survey. USing 50
percent to extrapolate roughly, the resident population using the upper
Susitna basin probably falls between 4,000 and 5,000 moose. This is a
substantial increase when compared with 1973 figures which estimated
the upper bas"in population at approximately 1,800 animals. This wide
diversity in population estimates can be attributed to better research
techniques and improved population estimating methods.
Present information indicates that moose depend heavily upon the
river bottom and adjacent areas for winter habitat and calving areas,
both above and below the Watana and Devil Canyon damsites. Increasing
snow depths above timberline trigger moose migrations to the wintering
areas in the lowlands. Additional observations of moose during normal
and severe winter conditions are necessary to determine the importance
of the area as critical winter range.
CULTURAL CHARACTERISTICS
Archeological Resources
An archeological reconnaissance was conducted by the Corps of
Engineers in 1978 for the purpose of clearing specific sites within
the project area so that geological investigations could be conducted.
Four sites were found in the Watana damsite area which range in age
E-3
from 3,700 to 12,000 years old. These sites, generally located on top
of small knolls, were probably associated with the hunting activities
of primitive man. No base camps or kill sites were found but they
must also exist. The number of sites found shows that the potential
for other finds is extremely high and indicates that prehistoric use
of the area appears to have been considerable. At the present time,
the sites found have not been nominated for inclusion on the National
Reg; ster.
E-4
ENVIRONMENTAL IMPACTS OF THE DEVIL CANYON -WATANA HYDROPOWER PLAN
MAMMALS -MOOSE
According to ADF&G surveys conducted ;n 1977, construction of the
Watana dam would have a highly detrimental effect on moose populations
in that inundation of the lower, spruce-covered reaches of the Watana
Creek valley, which are probably critical moose habitat, would sub-
stantially reduce the carrying capacity of the area. In addition, con-
struction of the Devil Canyon dam would also adversely impact moose
populations and substantially reduce the carrying capacity of a major
portion of the Devil Creek drainages. The Devil Canyon impacts are
not expected to be as significant as the Watana impacts because of the
marginal habitat and limited moose populations in the Devil Canyon area.
Present information indicates moose depend heavily upon the river
bottoms and adjacent areas for winter habitat both above and below
the Watana and Devil Canyon damsites. Lack of adequate wintering
areas in the lower Susitna valley below the Devil Canyon damsite has
been a major limiting factor to moose population growth in the past.
Most existing winter range is along the major rivers where periodic
flooding has caused rechanneling of the main stream, allowing riparian
willow to colonize the dry streambeds. Regulating the flow of water
from the dam at Devil Canyon may have a highly detrimental effect on
growth of riparian vegetation downstream to the mouth of the Susitna.
It is possible that maintaining a steady flow of 8,000 to 10,000 cubic
feet per second from the Devil Canyon dam would effectively prevent
the flooding activity that presently occurs periodically. This could
create a short-term abundance of winter range along the riverbanks that
might last 30 or more years. The net long-term effect could well be a
negative one, however, as it is suspected that the present natural
flooding activity of the Susitna River produces favorable conditions
for browse production. Without the annual floods. these riparian areas
could become mature stands of hardwoods after 25 or 30 years and pro-
vide little or no winter forage. Research on riparian vegetation
habitat types and associated moose usage downstream of dam construction
is essential to determine potential impacts on moose populations.
Construction of the Devil Canyon dam would flood approximately
7.500 acres. The riverbanks along this portion of the river are
generally steep and provide marginal moose habitat. Since water levels
in the Devil Canyon reservoir will remain fairly constant, low mor-
tality rates associated with ice shelving and steep mudbanks would be
expected.
E-5
Construction of the Watana dam would result in the flooding of
approximately 43,000 acres along Watana Creek and the Susitna River.
Approximately 35,000 acres sustain moderate to heavy utilization by
moose during an average winter. Data gathered by ADF&G indicate that
moose from several surrounding areas of the Susitna basin migrate
across or utilize this portion of the river during some period of the
year. Effects of the construction of the Watana dam on moose popula-
tions could be substantial. The resident nonmigratory segment of the
population could be eliminated. Migratory moose could also be sub-
stantially effected in that the reservoir could be an effective
barrier to migrations during some seasons. Due to large fluctuating
water levels, ice shelving and steep mud banks could be expected to
cause high mortality among moose, especially calves.
This discussion of impacts on moose populations within the upper
Susitna River basin is substantially different from the discussion
contained in the 1976 Interim Feasibility Report, which predicted
that the proposed project "would affect only a small percentage of the
upper Susitna moose population." The newly gathered information has
resulted in the reevaluation of previously identified impacts and the
recognition that additional impacts potentially exist which may be
important.
ARCHEOLOGICAL RESOURCES
An archeological reconnaissance conducted by the Corps of Engineers
in 1978 resulted in the finding of several previously unknown archeo-
logical sites in the Watana damsite area. This reconnaissance indicates
that the potential for other finds is extremely high. Intensive archeo-
logical surveys will be conducted during the project feasibility analysis
to conform with cultural resource regulations. If the project is
determined to be feasible, a program will be conducted to salvage
archeological sites which will be impacted by the project.
SECTION 404(b} EVALUATION
To date a Section 404(b} evaluation (Discharge of Dredged or Fill
Materials into Waters of the United States) under the Federal Water
Pollution Control Act of 1972 (Public Law 92-500) as ammended has not
been performed. A 404(b} evaluation will be performed with data
gathered during the project feasibility analysis.
EXECUTIVE ORDER 11988 (FLOOD PLAIN) EVALUATION
In compliance with Executive Order 11988 the items under Paragraph
8 of General Procedures have been considered as follows:
E-6
1. The project ;s designed to impound water behind two dams in
the natural channel of the river. The basic conditions of this hydro-
power project present no economically feasible alternatives.
2. The construction of the project will cause only minor induced
development in the immediate area since the product (energy) will be
transmitted to existing population centers far removed from the project
site.
3. The natural and beneficial values of the flood plain will be
disrupted only at the site of the reservoir and powerplant. Revegeta-
tion programs will be adopted to restore slopes along construction sites
and roadways.
4. As the project progresses from its initial phase to the design
and construction phases, there will be a continuing evaluation and
dialogue with local interests and concerned agencies who will have
constant input to the study.
E-7
RELATIONSHIP OF THE PROPOSED DEVELOPMENT TO LAND USE PLANS
Lands within the upper Susitna River basin are essentially in large
block ownership with the majority under the control of the Department
of the Interior, Bureau of Land Management (BLM). These lands are
generally in their natural state and undeveloped with improvements or
land access routes. Air transportation is the primary means of access
to and within the area. There are some scattered small parcels of land
in private ownership as homestead sites or mining claims. Many of
these private parcels have no developed overland access. For the most
part, development in the area is concentrated along the established
transportation routes such as the Parks Highway and the Alaska Railroad
on the west and the Denali Highway on the north.
Because of the absence of roads and other development in the basin,
the area is subject to Section 603 of P.L. 94-579, "The Federal Land
Policy and Management Act of 1976." This section provides for the
protection and study by BLM of roadless areas of public land containing
5,000 or more acres. The intent is the protection of potential wilder-
ness area values pending a determination of the ultimate classification
and use of such lands. During the allotted 15 year study period, any
use of the lands is subject to BLM authorization and must be conducted
" ..• in a manner so as not to impair the suitability of such areas for
preservation as wilderness ... ". Consequently, any development or con-
struction in the area would be precluded pending a determination and
classification by BLM.
Most of the public lands in the basin have been selected by Native
corporations under the Alaska Native Claims Settlement Act (ANCSA),
as amended of 18 December 1971. These selected lands remain under the
jurisdiction of BLM pending final conveyance of fee simple title to
the various Native corporations. Any use of these lands prior to
conveyance of title is subject to specific permission from BLM with
the concurrence of the various concerned Native groups.
The gross land area required (lands which must be acquired) for
containment of the proposed Devil Canyon and Watana reservoirs is
approximately 157,440 acres. Of this land, 67,200 acres are to be
conveyed to the Cook Inlet Region, Incorporated (CIRI) for later
reconveyance to various village corporations. This transfer of lands
is directed by a 1976 amendment to ANCSA, P.L. 94-456 and will include
both the surface and subsurface interests. This transfer also includes
lands within Power Site Classification No. 443 which was established
in 1958 for potential future development of the Susitna River for hydro-
electric power production.
E-8
In addition to the lands discussed above, as many as 53,760 acres
have been selected for conveyance to satisfy any deficiencies that may
exist in total acreage entitlements under ANCSA. These "deficiency"
selections in the area have a selection priority of nine (9) and, in
all probability, will not be conveyed to CIRI on behalf of the village
corporations. These lands have, however, been overselected by CIRI
for its own benefit and could conceivably be conveyed to CIRI. A
portion of these lands south of the Susitna River (24,686 acres) has
been made available for selection by the State of Alaska pursuant to
the agreement titled "Terms and Conditions for Land Consolidation and
Management in the Cook Inlet Area" (Cook Inlet Land Swap Agreement).
The State's right to select these lands for conveyance is superior to
that of CIRI but is inferior to valid village corporation selections.
Since the village corporation selections are priority nine (9) it is
probable that the State could receive the title to the lands.
The remaining area within the proposed reservoir boundaries (36,480
acres) is controlled by BLM and has been withdrawn from appropriation
for either study and classification or for selection by CIRI as a
IIdeficiencyll selection area. Again, this "deficiency" selection ;s
an excess, or overselection, to make lands available for satisfaction
of total acreage entitlements. Conveyance of any portion of such
selected lands is limited.to fulfillment of acreage entitlements and
is indeterminable at this time. As discussed above, the State of
Alaska will have a right to select a portion of this area south of
the Susitna River (5,120 acres), and such a selection would be superior
to that of CIRI.
E-9
LITERATURE CITED
Bacon, Glenn. Archeology in the Upper Susitna River Basin 1978. Army
Corps of Engineers, Alaska District, 1978.
Riis, James C., and Nancy V. Friese. IIFisheries and Habitat Investi-
gations of the Susitna River-~A Preliminary Study of Potential
Impacts of the Devils Canyon and Watana Hydroelectric Projects,"
Pre1iminar~ Environmental Assessment of Hydroelectric Development
on the Susltna River. Alaska Department of Fish and Game for the
U.S. Fish and Wildlife Service, March 1978.
Taylor, Kenton P. and Warren B. Ballard. IIMoose Movements and Habitat
Use Along the Upper Susitna River--A Preliminary Study of Petential
Impact of the Devils Canyon Hydroelectric Project," Preliminary
Environmental Assessment of Hydroelectric Development on the
Susitna River. Alaska Department of Fish and Game for the U.S.
Fish and Wildlife Service, March 1978.
U.S. Army Corps of Engineers, Alaska District.
Susitna Hydropower Feasibility Analysis.
or Alaska, June 1978.
E-10
Plan of Study for
Prepared for the State
SECTION F
RECREATIONAL ASSESSMENT
None of the OMB comments were directed at the
recreational aspects of the project. Therefore,
no additional recreation studies were undertaken.