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SUSITNA HYDROELECTRIC PROJECT
FEDERAL ENERGY REGULATORY COMMISSION
LICENSE APPLICATION
EXHIBIT F
SUPPORTING DESIGN REPORT
(PRELIMINARY)
FEBRUARY 1983
1 ALASKA POWER AUTHORITY __--J
SUSITNA HYDROELECTRIC PROJECT
EXHIB IT F
SUPPORTING DESIGN REPORT (PRELIMINARY)
TABLE OF CONTENTS
GENE RA L .•00 •••••••••••••••••II •••••••••0 •••D •••••e _•••••Go lit _••••••••••
pale
F-
1 PROJECT PARAMETERS F-l-l
APPENDIX FA -Watana Emergency Spi 11 way ..•.•...........••.•..••...•FA-1
APPENDIX FB -Watana and Devil Canyon Embankment Stability Analyses.FB-1
APPENDIX FC -Summary of PMF and Spillway Design Flood Analyses ..•.FC-1
Lis t of Tab 1es i
List of Figures ii
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2 -PRO",lECT DESIGN DATA ••••••••••••.••••..•••••••••••••••••••••••••
2.1 -Topographi ca 1 Data .e _•••••••••••••••••••••••••••••••••••
2•2 -Hyd r 0 log i cal 0 at a 110 ••••••••••••
2.3 -Meteorological Data .,0 ••••••••••••
2.4 -Reservoir Data .."~O •••I!l •••••••••
2.5 -Tailwater Elevations O ••~•••••••••••••~•••D •••••••••••
2.6 -Design Floods .
3 -CIVIL DESIGN CRITERIA .•....•.••..••..•.••..••••••••....•..••...
3.1 -Governing Codes and Standards •.•••.••...•..•••.....•....
3.2 -Design Loads .
3.3 -Stability 8 •••••••••••••••••••••••••••••
3.4 -Material Properties 0 ••••••0 ••••••••••••••••••••••
4 -GEOTECHNICAL DESIGN CRITERIA ••....•....•......••....•..........
4.1 -Watana .,III •••Ci ••
4.2 -Devil Canyon .,0 ••••••
5 -HYDRAULIC DESIGN CRITERIA .......•..•....•..•......••.•....•....
5.1 -River Flows ~DD •••III •••••0 •••
5.2 -Design Flows "'".
5.3 -Reservoir Levels "'.~.
5.4 -Reservoir Operating Rule .•..........•..•.•..............
5.5 -Reservoir Parameters "'.0 ••••••111.
5.6 -Freeboard .
5.7 -Criteria .
6 -EQUIPMENT DESIGN CODES AND STANDARDS .
6.1 -Des;gn Codes and Standards .•..•....•..•.•..•..•••..•...•
6.2 General Criteria 0 •••••111
6.3 -Diversion Structures and Emergency Release Facilities ••.
6.4 -Main Spillway .
6.5 -Outlet Facilities ~..o ••
6.6 -Power Intake III .,•••••
6.7 --Powerhouse "
6.8 -Tailrace Tunnels DCi •
F-2-1
F-2-1
F-2-1
F-2-1
F-2-1
F-2-1
F-2-1
F-3-1
F-3-1
F-3-1
F-3-6
F-3-9
F-4-1
F-4-1
F-4-11
F-5-1
F-5-1
F~5-1
F-5-1
F-5-2
F-5-2
F-5-2
F-5-2
F-6-1
F-6-1
F-6-2
F-6-4
F-6-5
F-6-6
F-6-7
F-6-8
F-6-10
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LIST OF TABLES
F.l Pre-Project Flow at Watana (cfs)
F.2 Pre-Project Flow at Devil Canyon (cfs)
F.3 Typical NOAA Climate Data Record
F.4 Summary of Climatological Data·
F.5 Recorded Air Temperatures at Talkeetna and Summit in of
;
LIST OF FIGURES
F.l
F.2
F.3
F.4
F.5
Area and Capacity Curves -Watana Reservoir
Area and Capacity Curves -Devil Canyon Reservoir
Watana Tai lwater Rat i n9
Devil Canyon Tailwater Rating (Tailrace to Portage Creek)
Mean Response Spectra at the Devil Canyon Site for
Safety Evaluation Earthquake
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I
GENERAL
This document sets out the principal project parameters and design cri-
teri a for the Watana and Devil Canyon hydroelectric projects and wi 11
form the basis of the detailed engineering design.It has been pre-
pared to satisfy the requirements of Section 4.41(g)(3)of the FERC
Regulations which specify the submission of supporting information.
The purpose of this information is to demonstrate that proposed struc-
tures are safe and adequate to fulfill their stated functions.
The report has been prepared as a main report with five reference vol-
umes attached.This report has been collected as a design criteria
document containing a summary of project parameters,design criteria,
and codes and standards.The volumes included as reference volumes are
independent reports produced as part of the feas i bil ity and pre-l i cense
application preliminary design efforts.These volumes contain the de-
tailed information necessary for review and independent evaluation of
the project features.
The reports attached for direct reference are:
-1980-81 Geotechnical Report;3 Volumes and 1982 Supplemental Geotech-
nical Report (1);
-Feasibility Report,Volume 5,Appendix 8,Design Development Studies
(2);
-Final Report on Seismic Studies,February 1982 (3);
-Regional Flood Studies,December 1981 (4);
-Feasibility Report,Volume 4,Appendix A,Hydrological Studies (5);
and
-Feasibility Report,Volume 6,Appendix C,Cost Estimate (6).
The report and reference volumes include information in addition to
that required in the regulations.For clarity,the following cross-
reference has been included.This reference directs the reader to the
relevant portion of a reference volume for a specific topic.
F-l
Topic
Site Suitability Investigations
-Previous Investigations
-Regional Geology
-Results of Geotechnical
Investigations
Reservoir Rim Stability
Boring Logs,Geology Reports
Laboratory Test Reports
Borrow Areas
Required Quantities of
Construction Materials
Stability and Stress Analyses
for Watana Dam
Bas'is for Seismic Loading
Basis for Spillway Design Flood
Basis for Probable Maximum Flood
WATANA
Direct Reference
(1),Volume 1,Section 3
(1),Vo lume 1,Section 4
(1),Volume 1,Section 6
(1),Volume 1,Appendix K
(1),Volume 1,Appendices
Band D
(1),Volume 1,Section 6,
Appendix F
(6)
(2),Volume 5,Appendix B6
(3 )
(4),(5)Appendix A3
(5)Appendix A2
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Topi c
DEVIL CANYON
Direct Reference
Site Suitability Investigations
Reservoir Rim Stability
Boring Logs,Geology Reports,
Laboratory Test Reports
Borrow Areas
Required Quantities of
Construction Materials
Devil Canyon Stress Analyses
Stability of Abutment Slopes
Basis for Seismic Loading
Basis for Spillway Design Flood
Basis for Probable Maximum Flood
F-2
(1),Volume 1,Section 7
(1),Volume 1,Appendix K
(1),Volume 1,Appendi~es
C and E
(1),Volume 1,Section 7,
Appendix G
(6)
(2),Appendix B5
(2),Appendix 85 Attachment 1
(3)
(4),(5)Appendi x A3
(5),Appendix A2
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1 -PROJECT PARAMETERS
,.,.,.
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1 -PROJECT PARM1ETERS
Item
River Flows
Average flow (over 32 yrs
of record)
Probable maximum flood
inflow
Maximum flood inflow with
return period of 1:10,000
yrs
Maximum flood inflow with
return period of 1:25 yrs
Maximum flood inflow with
return period of 1:50 yrs
(unrouted)
Normal maximum operating
level
Average TWL
Minimum operating level
Area of reservoir at
maximum operating level
Reservoir live storage
Watan a
7,990 cfs
326,000 cfs
156,000 cfs
76,000 cfs
87,000 cfs
2,185 ft MSL
1,455 ft MSL
2,065 ft MSL
38,000 acres
3.74 x 10 6
acre ft
F-1-1
Devi 1 Canyon
9,080 cfs
346,000 cfs (routed
through Watana)
362,000 cfs (unrouted)
161,000 cfs (unrouted)
165,000 cfs (after
routing through
Watana)
(increase attributed
to the assumed overlap
of Watana peak outflow
and peak flow from
intermediate catchment)
37,800 cfs
85,000 cfs (unrouted)
39,000 cfs (after
routing through
Watana)
98,000 cfs (unrouted)
1,455 ft MSL
850 ft MSL
1,405 ft MSL
7,800 acres
0.35 x 10 6
acre ft
Item
Reservoir total storage
Dam
Type
Crest elevation
Crest length
Height
Cut-off and foundation
treatment
Upstream slope
Downstream slope
Crest wi dth
Sadd le Dam
Type
Crest Elevati on
Crest Length
Height
Cut-off and Foundation
Treatment
Upstream Slope
Downstream Slope
Crest Wi dth
Watana
9.47 x 10 6
acre ft
Rockfill
2,210 ft MSL at
center
2,207 ft MS L at
abutments
4,100 ft
885 ft above
foundation at
core
Core founded on
rock,grout
curtai n and down
stream drains
1V:2.4H
1 V:2H
35 ft
None
F-1-2
Devi 1 Can on
1.9 x 10 6
acre ft
Concrete arch
1,463 ft MSL (+3 ft
parapet wall)
1,650 ft (arch dam
including
thrust blocks)
646 ft above
foundati on
Founded on rock,grout
curtain and downstream
drains
20 ft
Earth/Rockfi 11
1472 ft MSL
950 ft
245 ft
Core founded on rock,
grout curtain and
downstream drains.
IV:2.4H
1V:2H
35 ft
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em
Diversion
a ana anyon
-Cofferdam types
Cut-off and foundat ion
Upstream cofferdam crest
elevation
Downstream cofferdam crest
elevat ion
Maximum pool level during
construction
Water passages
Outlet structures
Diversion capacity
Final closure
Rockfill
Founded on all u-
vium with slurry
trench to rock
1,545 ft MSL
1,472 ft MSL
1,536 ft MSL
2 concrete-lined
tunnels,38 ft
dia.
Low-level struc-
ture with high
head slide
closure gates
80,500 cfs
Mass concrete
plugs in line
with dam grout
curtai n
Rockfi 11
Founded on alluvium
with grout curtain
947 ft MSL
898 ft MSL
944 ft MSL
1 concrete-l i ned
tunnel,30 ft dia.
Low-level structure
with high head slide
closure gates
39,000 cfs
Mass concrete plugs
in line with dam
grout curtain
.....
Releases during impounding 6,000 cfs maximu
via regulating
gates in
diversion plug
Emergency Reservoir
Drawdown
6,000 cfs maximum
via low-level fixed
cone valves
Low level outlet Fixed cone valves
tunnel
....,
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Maximum capacity 30,000 cfs
F-1-3
38,500 cfs
em atana anyon
Outlet Facilities
-capacity 24,000 cfs 38,500 cfs
-control struc.Fixed cone valves Fixed cone valves
-energy dissip.Six 78"dia.3-90"dia.,four 102"
fixed cone valve dia.fixed cone valves
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Spi llway
Desi gn Floods
Mai n Spi llway
-capacity
Passes pmf pre-
serving integrit
of dam
Passes routed
1:1O,000-yr floo
(156,000 cfs)
with no damage
structures
120,000 cfs
Passes pmf preserving
integrity of dam
Passes routed
1:10,000-yr flood
(165,000 cfs)with
no damage to
structures
123,000 cfs -
-control struc.Gated ogee crests Gated agee crests
-energy dissip.Flip Bucket Flip Bucket
-crest elev,2,148 ft MSL 1,404 ft MSL
-gate sizes 3 -49 ft H x 3 -56 ft H x 30 ft W
36 ft W -
Emergency Spillway
-capacity
-type
-crest elev.
-chute wi dth
120,000 cfs
Fuse plug
2200/2201.5
310/200
F-1-4
150,000 cfs
Fuse plug
1464/1465.5
200
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Power Intake
Type
Number of intakes
Draw-off requirements
Drawdown
Maximum discharge/unit
Penstocks
Type
Number of penstocks
Watana
Massive concrete
structure
embedded in rock
6
Multi-level
120 ft
Concrete-lined
rock tunnels with
downstream steel
1i ner ...
6
eVl Canyon
Massive concrete
structure embedded
in rock
4
Multi-level
50 ft
3,670 cfs
Concrete-lined rock
tunnels with down-
stream steel liner
4
Di ameter
Powerhouse
Cavern size
17 ft conc/15 ft 20 ft conc/15 ft steel
steel
455 ft x 74 ft x 360 ft x 74 ft x
126 ft 126 ft
Separate gallery Separate gallery
.....
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Type
Transformer area
Control room &
administration
Underground
Surface*
Underground
Underground
Access
Power Plant
-vehicle
-personnel
Rock tunnel
El evator from
surface
Rock tunnel
El evator from
surface
Number of units
Nominal unit output**
6 4
170 MW at 659 ft 150 MW at 542 ft
net head net head
F-I-5
Item
Turbines
Rated net head
Rated full gate output
Rated discharge
Station output @ rated hea
-best gate
-full gate
Generator
Type
Watana
680 ft
250,000 hp
3,490 ft 3/s
936 MW
1,098 MW
Vertical
synchronous
Devi 1 Canyon
590 ft
205,000 hp
3,680 ft3/s
510 MW
600 MW
Vert ical
synchronous -
Rated output (60°C)190 MVA air-167 MVA air-cooled
cooled
218 MVA 210 MVA
0.9 0.9
15 kV +5%15 kV +5%
Overload (80°C)
Power factor
Voltage
Frequency
Speed,rpm
Tr ansformers
Tailrace
Water passages
Elevation of water
passages
Surge
Tailwater elevations
60 Hz
225 rpm
9 x 145 MVA
15/345 kV,singl
phase
Two 34 ft dia.
concrete-lined
tunnels
Below minimum
t ai 1water
Single surge
chamber
See Fig.F.3
60 Hz
225 rpm
12 x 70 MVA
15/345 kV.single
phase
One 38 ft dia.con-
crete-lined tunnel
Below minimum tail-
water
Single surge chamber
See Fig.F.4
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*Area control center for both Watana and Devil Canyon plants.
**Based on a minimum reservoir level in peak demand month (December).
F-I-6
,~2 -PROJECT DESIGN DATA
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2 -PROJECT DESIGN DATA
2.1 -Topographical Data
The topography of the site is based on aerial survey mapping reduced to
a scale of 1 inch:200 feet.Contours are at 5-foot intervals.
2.2 -Hydrological Data
The hydrological data are based on records taken over a period of 30
years,supplemented by 2 years of records at site.Streamflows and
respective drainage areas are extrapolated and adjusted to give a
representative pattern of flows at the damsite.Flows are shown in
Tables F.1 and F.2 .
2.3 -Meteorological Data
Historical records of precipitation,temperature,and other climatic
parameters are collected by NOAA at several stations in the study area.
However,there were no stations located within the basin until the es-
tablishment of weather stations as part of this study.Consequently,
no long-term weather records are available near the damsites.The
closest stations with long-term records are at Ta"'keetna and Summit.
Data from these stations are given in Tables F.3 to F.5.
2.4 -Reservoir Data
Reservoir elevation,area and volume curves for Watana and Devil Canyon
are given in Figures F.1 and F.2.
2.5 -Tailwater Elevations
Tailwater elevations plotted against flows are given in Figures F.3 and
F.4.
2.6 -Design Floods
An analysis of major historical floods indicated that snowmelt contri-
butes a major part of the floods.The Probable Maximum Flood (PMF)was
therefore assumed to occur during the snowmelt season.Snowmelt was
assumed to start on June 3 based on the adopted temperature sequence.
The Probable Maximum Precipitation (PMP)of 8.7 inches above the Watana
Dam site was used in the PMF analysis.The average PMP above Devil
Canyon was 8.8 inches.
The PMF was derived through use of the Streamflow Synthesis and Reser-
voir Regulation (SSARR)watershed model.The PMF hydrograph was
synthesized assuming an initial base flow of approximately 7,000 cfs
F-2-1
and moist antecedent soil conditions.The analysis gave peak inflows
of 326,000 cfs at Watana and 362,000 cfs at Devil Canyon.The PMF
hydrograph is shown on Figure F.4A.-
The PMF was routed through Watana
293,000 cfs.This flood routing
Canyon reservoir to 346,000 cfs.
Canyon reservoir was 345,000 cfs.
reserv ior and the peak outflow was
reduced the peak inflow to Devil
The routed peak outflow from Devil
The 10,000-year flood peak inflows are estimated to be 156,000 cfs at
Watana,and 161,000 cfs (unrouted)and 165,000 cfs (routed)at Devil
Canyon.The increase in the routed 10,OOO-year peak flow over the
natural flood resulted because of the assumption of synchronization of
routed fl ood peak and peak from the i nterven i ng area between the two
developments.
The develoment of the PlVlF and Spillway design floods are presented in
Appendix FC.
F-2-2
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3 -CIVIL DESIGN CRITERIA
3 -CIVIL DESIGN CRITERIA
3.1 -Governing Codes and Standards
Where specific standards and design criteria are not covered in these
criteria,the following codes and standards shall apply:
(a)General
-American National Standards Institute,ANSI A58.1;
-Uniform Building Code (UBC);
-Alaska State Building Construction Code;and
-Occupational Safety and Health Administration Standards (OSHA).
(b)Concrete
-American Concrete Institute -ACI Standard 318 (for reinforced
concrete)
-American Concrete Institute -ACI Standard 301
-American Concrete Institute -ACI Standard 207 (for mass con-
crete)
(c)Structural Steel
-American Institute of Steel Construction,Steel Construction
Manual.
3.2 -Design Loads
(a)Dead Loads:
Mass concrete
Reinforced concrete
Steel
Water
Silt -vertical
-hori zontal
Backfill (all dams)
-dry
-saturated
-submerged
145 lbs/ft3 (143 lbs/ft3 when
lbs/ft 3
checking stability)
150
490 lbs/ft 3
62.5 lbs/ft 3
120 lbs/ft3
85 lbs/ft3
115 lbs/ft 3 )
130 1bs/ft3 ) -Provisional
70 lbs/ft 3)
.-
(b)Backfi 11 Loads
The lateral earth pressure against vertical faces of structures
with horizontal backfill will be computed using the equivalent
fluid pressures calculated from:
p =kwH
F-3-1
Where:
p =unit pressure
k =pressure coefficient
w =unit weight of fill
H =height of fill
For structures free to deflect or rotate about the base the pres-
sure coeffi ci ent will be computed from Rank i ne I s theory,which
is:
kA =tan 2 (45-0/2)
Where 0 =angle of internal friction (degrees).
For structures restrained from bending or rotation,the at-rest
pressure coefficient will be used:
ko =1 -sin 0
Coulomb1s theory will be used for computing lateral earth pres-
sures on wall surfaces with slopes flatter than 10V:1H or with
.sloping baCkfill steeper than 1V:4H.
Where vehicular traffic can run adjacent to the face,a surcharge
loading of 500 lbs/ft 2 should be applied.
(c)Snow and Ice Loads
Special consideration shall be given to prevent accumulation of
ice loading due to spray in the final design.
Snow load .0 ••••••••••••••••••••••••••••••••••60 lbs/ft 2
(d)Powerhouse Floor Loads
-I
Generator Hall
Machine Shop
Swi tchgear Room
Service Bay
Control Room
Transformer Gallery
Offices and Stairs
-1000 lbs/ft2
500 lbs/ft2
-300 lbs/ft 2
-1500 1bs/ft 2 or 90 ki p concentrated
load in designated areas
-200 lbs/ft2
-300 lbs/ft 2
100 lbs/ft 2
F-3-2
(f)
(e)Crane Loads
The following percentages shall apply to the powerhouse crane and
the power intake crane.The minimum deflection to span ratio of
crane support beams shall be 1:1000.
Vertical impact -25 percent of static wheel load
Lateral load -10 percent of crane capacity,trolley,hook,
and lifting beam distributed equally be-
tween rails.
Longitudinal load -10 percent of static wheel loads.
Spillway Deck Loads
Area designated for service 500 lbs/ft2
Other areas 200 lbs/ft2
(g)Hydraulic Loads
All structures shall be designed for full lateral water pressures
where applicable,plus full hydrodynamic and uplift forces.
(i)Uplift
r-Upl ift pressures shall be taken as equivalent to the full
head of water on a foundation or structure where no head
"differential exists across the structure.Safety factors
in accordance wi th normal cond it ions wi 11 app 1y.Where a
head differential exists across a structure,uplift forces
shall be calculated as follows.
-For water-retaining concrete structures provided with
drainage galleries and drain holes deep into the founda-
tions,uplift shall be considered across the complete
rock/concrete interface varying 1 inearly from H1 at the
upstream heel to (Hl -H2)+H2 at the drains to
H2 at the toe.3
Where H1 =static head upstream
H2 =static head downstream.
Safety factors in accordance with normal conditions will
apply with drains operative.
Where there are no pressure re 1 i ef drai ns,normal up 1i ft
shall be assumed to vary linearly from headwater at the
upstream face to tailwater at the downstream face.Safety
factors in accord ance wi th normal cond it ions wi 11 app 1y.
The latter uplift condition shall also apply for the ex-
treme uplift where drains are to be provided but are
assumed to be ineffective in reducing uplift.Safety fac-
F-3-3
tors in accordance with extreme conditions will then
apply.
All owab 1e tens i 1e strength at the rock-concrete i nterf ace
shall be zero.If under earthquake loading conditions a
crack is considered to develop at the upstream heel,the
uplift pressure shall be taken as equal to the normal dis-
tribution as described above over 100 percent of the base
area.
Under PMF condit ions where cracking at the upstream heel
develops,upl ift shall be considered to be equal to full
headwater within the full depth of the crack,reducing to
the values at the line of drains and downstream toe as pro-
portioned above.
Apron and chute slabs and slab walls against rock shall be
designed against uplift resulting from sudden changes in
water level.
Uplift from centrifugal forces shall be considered where
contraction joints occur on the concave floor of chutes.
Toe curve pressures on the interior face of training walls
at concave chute surfaces shall be calculated in accordance
with Plate 21 of Hydraulic Design of Spillways EM 1110-2-
1603 by U.S.Army Corps of Engineers.
Hydraulic loads due to earthquakes are given in the follow-
ing section on seismic loads.
(h)Seismic Loads
See Reference No.3.
The largest mean peak horizontal ground acceleration that could
affect the sites is 0.5g with a duration of 6 seconds.
(i)Watana
Design of critical concrete structures wi 11 use an 80th
percentile response spectrum from the "Safe Evaluation
Earthquake"(SEE)with a 10 percent damping ratio scaled
down by a factor of 80 percent.
(ii)Arch Dam at Devil Canyon
The arch dam is to be checked under sei smi c load i ng by
dynamic analysis based on trial load method and the ADSAS
program developed by the Department of the Interior.
F-3-4
-
The arch dam wi 11 be designed for a base ground accelera-
tion of 0.8 x SEE =0.57g.
Arch dam system damping ratio -0.10 of critical*.
Acceleration response spectrum -See Figure F.5.
For final design,a time-history finite element analysis
will be carried out.
-Concrete Retaining Structures (other than arch dam)
Mass concrete retaining structures wi 11 be designed for
0.8 x SEE using static analysis.
-Other Major Structures
Non-reservoir retaining major structures will be designed
for the 100/1I0-year return earthquake corresponding to
0.2g.
-Hydrodynamic Pressure
The hydrodynamic pressure due to horizontal earthquake on
water-retaining surfaces shall be computed using the
theory of Westergaard for the dynamic change in pres-
sure:
1/2
P =a.51.25 (hy)lbs/ft 2
Where h =total height of structure (ft)
y =depth below reservoir surface (ft)
a =ground acceleration/acceleration due to gra-
vity
The distribution of pressure is parabolic;hence,the
total force and moment at a section y ft below water
level are given by:
F =2/3.P.y
M =0.4.F.y
*This damping ratio is similar to ones used at Swan Lake,
El Cajon and Salinas dams.
F-3-5
(i)Temperature and Thermal Loads
Expansion and contraction resulting from temperature changes,
moisture changes,creep in component materials,"and movement
resulting from differential settlement are combined with other
forces and loadings for maximum unfavorable effects.
The maximum and minimum air temperatures are:
Maxi mum
M;n ;mu nl Qo It "1;10 0 It &G
(j)Horizontal Ice Loads
The follow-ing horizontal ice load shall be considered to act at
mid-depth of a 4 foot-thick ice cover at the water surface.
On the upstream gates ...••.••.••••••10.0 kips/lin ft
Excessive ice buildup on trashracks,gates,gate guides,and
support structures shall be prevented by heating such equipment.
3.3 -Stability
(a)Loads and Forces
The following loads and forces shall be used in stability analysis
for concrete gravity structures in the loading cases given in Sec-
t i on 3.3(d):
-Dead load or self weight;
-Live load;
-Hydrostatic uplift;
-Earth pressure;
-Water pressure;and
-Earthquake loads.
(b)Computations
The following values shall be computed at the foundation level and
at selected intermediate levels within each structure or element
of a structure to ensure adequate stabi lity and economy of design
within these design criteria:
-Stress at upstream face (parallel to slope);
-Stress at downstream face (parallel to slope);
-Location of resultant force;
F-3-6
"""
-Sliding factor;
-Shear friction factor;
-Flotation factor of safety;and
-Overturning factor.
(i)Sliding Stability Analysis
The normal analysis of sliding has been used,relating the
resistance to sliding along a horizontal or gently sloping
plane to the dri ving force or hori zonta 1 load.The factor
of safety F is the ratio of the resisting forces to the
driving forces.The following "shear friction"formula
shall be used (1):
F =(V-U)tan ~+cA
Pw
(1)
Where,for a horizontal potential failure plane:
v =total vertical force
U =total vertical uplift force acting on the failure planeo=angle of friction along plane
c =unit cohesion along plane
A =area of potential sliding plane
Pw =total horizontal thrust
(c)Limiting Criteria,Safety Factors
(i)Concrete Gravity Structures
Safety Factor
Load Conditions Sliding
Normal 3 within
concrete
4 withi n
rock
Overturning*Flotation
Resultant 1.5
within the
center third**
Compression
3 on compres si ve
strength of
concrete
4 on compressive
strength of rock
Unusual
(including
1:100-yr
earthquake
load case)
2.5 wi t hin 1.3
concrete
3.5 within
rock
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1.3 2.5 on compres-
i ve strength of
concrete
3.5 on compres-
sive strength
rock
Flotation CompressionLoadConditions
Unusual (inc.
100-year
return earth-
quate &PMF
load case)
Extreme
(including
0.8 x safety
evaluation
earthquake)for
arch dam and
reservoir
retaining
structures only
Sliding Overturning
2 withi n 1.1
concrete
2.7 within
rock
1.0 1.0
1.1
1.0
2.0 on compres-
i ve strength of
concrete
2.7 on compres-
sive strength of
rock
1.0
-
-i
Note:*Opinions differ on the use of overturning safety factors.
Acres policy is to retain this familiar concept~particularly in regard
to unusual and extreme loadings where cracking may occur~in order to
provide a measure of the relative safety of the structure.
**Safety factor implicitly greater than at least 1.5
(ii)Summary of Results
The resu lts of the above load condit ions for the reservoi r
retai ni ng concrete gravity structures have been summari zed on
the Exhibit F Plates as follows:
Watana Main spillway gate structure Plate F13
Devil Canyon arch dam thrust blocks Plate F46
Devil Canyon main spillway gate structure Plate F55
(d)Loading Cases
Among loading combinations to be considered at the final design
stage will be the following:
(i)Intake and Out let Structures
Case 1:
Case 2:
Concrete in place~site dewatered
Concrete in place~maximum water level outside
structure~inside of structure dewatered
(ii)Powerhouse Structure (Surface structures~if applicable)
Underground structures and individual elements of struc-
tures shall be analyzed for stability and stress consider-
ing all applicable loadings including water table in rock~
grouting pressure~and rock support systems.
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3.4 -Material Properties
Reinforced Concrete in all structures except the Arch Dam shall have a
compressive strength of 4,000 lb/in 2 at 28 days.The Arch Dam con-
crete shall have a compressive strength of 5,000 lb/in 2 at 365 days.
.....,
-Reinforcing Steel:
-Structural Steel:
-Penstock Steel Liner:
-Bolts,Nuts,and Washers:
ASTM A615 Grade 40 minimum
ASTM A36
ASTM A516 Grade 70
ASTM A325
-PVC water stops shall be provided in all water-retaining structures
as follows:
o In all expansion and contraction joints
o In all vertical construction joints communicating with dry inter-
ior spaces;and
o In all horizontal construction joints communicating with dry
interior spaces where the concrete thickness is less than 10 feet.
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4 -GEOTECHNICAL DESIGN CRITERIA
~,
4 -GEOTECHNICAL DESIGN CRITERIA
4.1 -Watana
(a)General
A detailed description of the geology and material properties for
the Watana site are provided in reference document "1980-81 Geo-
technical Report"and the "1982 Supplemental Geotechnical Report."
Design parameters,quantities,and estimates have been based on a
comprehensive evaluation of the site geotechnical conditions.
Where significant data remains to be obtained,conservative as-
sumptions have been made in development of foundation preparation,
treatment,material properties,and costs.The following tasks
set forth the design considerations,parameters,and criteria for
the Watana Dam and related structures.
(b)Dam Foundation Preparation and Treatment
(i)General
Rock foundations must meet the following criteria:
-The rock under the core must be nonerodib1e under the
seepage gradients;
-Core material must be prevented from moving down into the
foundation (e.g.,into cracks or joints);
-Contact between the core and rock surface must have per-
meability no higher than that of the core;and
-Any seepage through the foundation must be controlled and
discharged to avoid buildup of excessive seepage pres-
sures under the structures.
(ii)Excavation Under the Core,Filters,and Shells
The core,filter,and shell portions of the dam will be
founded on sound rock or concrete.All talus on the
slopes,river alluvium,and weathered rock in the valley
bottom and on the abutments wi 11 be removed.Estimated
core foundation rock slopes will be on the average of 1H:2V
below Elevation 1800 and 1H:1V above Elevation 1800.The
cross cut slopes will be 1H:10V.Dental excavation over
and above normal excavation will be performed in intensely
sheared and altered zones.Under the core and filter,den-
t a1 concrete wi 11 be placed as appropri ate to prov i de a
regular surface for fill placement.
F-4-1
(i i i)Grouting
Grouting will be performed as necessary to improve founda-
tion and abutment rock conditions for load bearing,mater-
ial piping,and seepage considerations.
-Consolidation Grouting
The rock under the core and adj acent upstream and down-
stream filters will be consolidation grouted to provide a
zone of relatively impermeable rock under the entire con-
tact.Consolidation grouting would impede relief of
seepage,so it will not be performed under the downstream
blanket filter.Consolidation grouting will be performed
on a 10 foot by 10 foot grid of approximately 30 foot
deep holes.Consolidation grouting will be performed as
required under the spillway and other appurtenant struc-
tures,as well as at the tunnel portals and in any frac-
t ured zones encountered underground wh i ch cou 1d be st a-
bilized by this method.
-Curtain Grouting
Curtain grouting will be performed beneath the dam found-
ation to a maximum depth of 0.7H (where H is the maximum
reservoir hydrostatic head at a particular location above
the dam foundation)to a maximum depth of approximately
350 feet.Grouting will be carried out from a series of
underground gallaries which will also serve as a drainage
collector for a system of drilled drain holes.A double
row grout curtain is proposed.Primary grout holes will
be considered as exploratory holes and will be core
dri lled.Based on exploratory results,the depths and
spac.,ing of secondary holes will be decided.
All holes will be water-pressure tested.Grouting will
be carried out using split spacing with the primary holes
at 40-foot spacing.The secondary,tertiary,and quater-
nary holes will bring the final hole spacing to 5 feet if
required.
In area of permafrost,additional boreholes may be re-
quired to induce thawing,to be able to form an effective
curtain.Further grouting may be required when the full
thawing effect of the full reservoir has occurred.
Grout holes will be vertical and inclined at angles of 45
degrees to intersect the main joint sets.Additional
grouting will also be performed as required in sheared
and altered zones and poor qual ity rock if it has been
determined that they are potential avenues for seepage.
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'"'"
-
The dam grout curtain will also extend under the spillway
intake structure to a mi nimum depth of 200 feet.The
grout curtain will be stopped approximately 30 feet from
the diversion tunnels.Radial grouting will be carried
out from the diversion tunnels along the length of the
concrete closure plugs to intersect with the grout holes
from the surface and form a continuous cutoff,of seepage
from the reservoir or the diversion tunnel sections up-
stream of the grout curtain.
-Contact Grouting
Contact grouting will be performed on concrete structures
in contact with rock and behind all tunnel linings and
tunnel plugs.
(iv)Drainage
Three-inch diameter drain holes will be drilled from the
"galleries beneath the dam foundation and abutments to in-
tersect seepage water and to provide pressure relief.Fil-
ters may be required in some of the drain holes to prevent
washout of fine material.
A grid of drainage holes will be provided around the under-
ground caverns to depths generally in excess of the deepest
rock bolt.Seepage will be collected by pipes or channels
and directed into the powerhouse drainage system.
A11 rock cuts wi 11 have surface drainage trenches at the
crest to prevent small rocks and soi 1 from bei ng washed
down the cut,and to reduce the amount of water to be chan-
ne 1ed away at the base of the cut.Pressure re 1i ef ho 1es
will be drilled into the face and base of cuts as necessary
to relieve areas of high ground water pressure.
(v)Intake Structure
The intake structure will be founded on sound,unweathered
rock..Although consoli dat i on grout i ng is not expected to
be necessary due to the excavation depth.it will be per-
formed if required.
Under rapid drawdown conditions,water pressure could
bui ld up behind structures cast ag·ainst rock.Therefore,
drainage will be provided through all concrete/rock inter-
faces that could experience these conditions.
Rock excavation faces are anticipated to be stable at very
steep slopes.Further data will be required in the area
for detailed stability analysis and design of protective
support systems.
F-4-3
(vi)Spillway
The spillway will be founded entirely on rock.The grout-
ing and drainage curtains in the dam foundation and under
the thrust block will extend under the spillway control
structure to reduce seepage and uplift pressures.
A drainage grouting gallery will be formed in the concrete
rollway of the control structure.This gallery will be
similar in size to the·rock tunnel beneath the dam and con-
structed as far upstream as possible to achieve a reduction
in water pressure over the largest possible area of the
foundat ion.
The spillway chute concrete/rock contact will be well
drained to prevent uplift pressures.Since,however,these
drains will be subject to freezing,it is proposed that a
spi 11 way drainage gallery be constructed at a depth of at
1east 30 feet below the concrete spill way slab along the
entire length of the spillway.A fan of drain holes
drilled from the surface drains will drain into the drain-
age gallery.The gallery will be approximately 10 feet by
10 feet in section.
The foundation for the entire spillway will be consolida-
tion grouted to a depth of 20 feet based on a grid of holes
spaced 10 feet by 20 feet.
Rock anchors will be installed in the spillway chute walls
to provide necessary support and fallout protection.
(vii)Relict Channel
Studies indicate the existence of a buried channel running
from the Susitna River gorge immediately upstream from the
proposed damsite to Tsusena Creek,a distance of about 1.5
miles.Along the buried channel thalweg,the highest bed-
rock surface is about 450 feet below reservoir level.The
maximum hydraulic gradient along the buried channel for the
edge of pool to Tsusena Creek will be approximately 9 per-
cent.
Potential problems imposed by the Relict Channel are:
Surface Flows -caused by settlement and resulting in a
breachlng of the reservoir rim.
-Subsurface Leakage -caused by low permeable material
that could result in the water loss and potential down-
stream piping.
-Permafrost -Increased thawing of permafrost in the rel-
~lct channel over time resulting in increased seepage.
F-4-4
-
-
-
-
"'"'"I
,~
Liquefaction -Filling of the reservoir resulting in sat-
uration of material in relict channel that could result
in liquefaction under seismic loading conditions causing
a breach of the reservoir rim.
Remedial measures considered for the relict channel are:
-Lowering of the reservoir level to provide adequate free-
board to eliminate potential of settlement and surface
flow.
-Placement of a downstream blanket to control the poten-
tial problem of piping.
-Long-term monitoring to determine rate of thaw of perma-
frost.
-Densification,in-place stabiliziation (i.e.,grouting),
or excavation and replacement of potentially liquifiable
materi al s.
Additional explorations are necessary to more closely def-
i ne the actual need and/or type of treatment necessary.
(c)Rock Slopes
(i)Design Methods
Since jointing is the prominent geologic structure,planar,
two-plane,and three-plane wedge failures were analyzed,
providing the basis for excavation and support details.
(ii)Factor of Safety
~Factors of safety employed in slope design for civil struc-
tures were:
Condition F.S.
Construction-temporary 1.1
Permanent 1.5
Extreme loading 1.0
(iii)Method of Analysis
Plane failures and two-plane wedge failures were analyzed
on an equal angle stereogram (Hendron,1971).No external
loads were included in these analyses.Analyses included
the four principal joint sets identified at the site.
r-
I
F-4-5
Jointing is believed to be the controlling geologic struc-
ture.Planes and wedges created by these joints were anal-
yzed.Design slopes were selected considering orientations
and inferred continuity of each joint set.The following
table summarizes recommended slopes for each generic orien-
t at i on...
Strike Dip Cut Slopes
N-S E 3.75V:1H
N-S W 4.0:1H
E-W N 3.75V:1H
NE-SW I~W 4V:1H
NE-SW SE 4V:1H
NW-SE NE 2.75V:1H
NW-SE SW 3V:1H
(d)Water Tunnel s
Two orientations are favorable for tunnels at Watana t 345°to 025°
and 070°to 090°.These two orientations cross the major dis-
continuities at high angles and subparallel minor ones.The least
favorable orientations are 045°to 065°and 100°to 160°t since
they parallel major joint sets and shear zones.Due to the site
configuration t the tunnels predominately follow the 070-090°
favorable trend.
(e)Penstocks
The penstock tunnels wi 11 be concrete 1 i ned over thei rent ire
lengths t with steel linings placed just upstream of the power-
house.Six penstocks,17-feet in diameter t are proposed.Pen-
stocks will be spaced 2.5 times the diameter,center to center.
The length of steel liner and support required will be dependent
on actual rock conditions.
(f)Caverns
As discussed above t the most favorable orientation for underground
structures are either 345°to 025°or 070°to 090°.The selected
orientation lies near the 345°trend.
Primary support in the powerhouse cavern will consist of rock
bolts in the crown having a working load of approximately 80kips.
The preferred rock bolt is a tensioned resin-anchored t resin-en-
capsulated rock bolt.Wall bolts will be similar to those des-
cribed above.
Rock bolts for other caverns with spaces between 40 feet and 80
feet will use the same capacitYt spacings,and percentages of
bolts as the powerhouses with bolt lengths equal to 1/3 of the
span for the crown and 1/10 of the wall height for walls.Shot-
crete sets,concrete,and wire fabric will be used as required.
Where shear zones intersect underground openings,more extensive
support will be required.
F-4-6
-
-
Drainage will be provided for walls and crowns to prevent seepage
pressures from affecting stability.Drain holes will be provided
extending into the rock a distance greater than the greatest rock
bolt length.
Caverns wi 11 be spaced a mi nimurn of 1.5 times the 1argest cavern
span.
(g)Watana Dam
(i)General
The mai n dam wi 11 consist of a compacted core protected by
fi ne and coarse fi lters on the upstream and downstream
slopes.The downstream outer shell will consist of allu-
vium gravel,and the upstream outer shell of cleaned,pro-
cessed alluvium gravel.The dam will be designed to pro-
~,vide a stable embankment under all conditions.
(ii)Design Criteria
To insure that the impervious core meets the earthquake re-
sistant design,the following design features will be in-
corporated into the main dam cross section:
-The core foundation contact will be widened near the ends
of the embankment to ensure seepage control during normal
operating conditions and any seismic event.
-Thick filter zones will be placed upstream and downstream
from the impervious core to prevent breaching of the core
from either post-construction settlement and cracking or
from any cracking resulting from a seismic event.
-The filters will be designed to be self-healing in case
of transverse cracks in the core resulting from either
post-construction settlement or a seismic event.
-The downstream filters will be designed to be capable of
handling any abnormal flows that could result from trans-
verse cracking at the core from post-construction settle-
ment or a seismic event.
-The proposed wi dth of the core wi 11 prevent arch i ng of
the core caused by transfer of load from the core to the
filter materials and shell.
i'
-Compacted river alluvium gravel will be used to construct
the downstream outer shell,and compacted c1 ean ri ver
alluvium gravel will be used to construct the upstream
outer shell to minimize settlement and displacement that
could be caused by a seismic event.
F-4-7
(iii)Freeboard and Static Settlement
The governing crest elevation excluding static and seismic
settlement is 2205 feet.
The expected seismic settlement of 0.5 percent of the
hei ght of the d am wi 11 be incorporated in the des i gn by lo-
cally steepening the slopes of the top of the dam to obtain
5 feet of additional freeboard at the maximum section and 2
feet of additional freeboard at the abutments.
(iv)Dam Cross Section
The typical cross section is shown in Plate F6.The imper-
vious core slopes will be 1.0 horizontal to 4.0 vertically
sloped upstream and downstream with a crest of 15 feet.
Minimum core foundation will be 50 feet requiring flaring
of the cross section at the left end of the embankment.
The upstream filter will have the following slopes:
-Fine filter zones will be 1.0 horizontal to 3.5 vertical
sloped upstream on the reservoir side.
Coarse filter zones will be 1.0 horizontal to 2.9 verti-
cal sloped upstream on the reservoir side.
The downstream filter zones will have the following
slopes:
-Fine filter zones will be 1.0 horizontal to 3.2 vertical
sloped downstream on the tailwater side.
-Coarse filter zone will be 1.0 horizontal to 2.7 vertical
sloped downstream on the tailwater side.
The upstream and downsteam filters are sized to provide
protection against possible leakage through transverse
cracks in the core that could occur as the result of
settlement or displacement during a seismic event.The
wide filter zones provide sufficient material for healing
of any cracks in the core and the size of the downstream
filter zones wi 11 ensure its capabi 1ity to handle any ab-
normal leakage flows.
F-4-8
-
-
-,I
-
r~
The shells of the dam will consist of compacted river allu-
vium gravels.To minimize pore pressure generation and to
ensure rapid dissipation during a seismic event,the satur-
ated upstream shell wi 11 consist of compacted clean river
alluvium gravels.This material will be processed to re-
move all fines less than ll2-inch size.The downstream
shell will consist of compacted unprocessed alluvium grav-
els since it wi 11 not be affected by pore pressure genera-
tion during a seismic event.
Slope protection on the upstream slope will consist of a
lO-foot zone of oversized material up to 36 inches in dia-
meter placed and compacted by suitable equipment.
The typical crest detail is shown in Plate F7.Because of
the narrowi ng of the dam crest,the fi lter zones wi 11 be
reduced in width and the upstream and downstream coarse
fi lter rep 1aced with carefu lly graded and se lected she 11
materials above Elevation 2170.A layer of filter fabric
is incorporated to protect the core material against damage
from frost penetration and dessication,and to act as a
coarse filter where required.
(v)Dam Material
-Core
The core material will be obtained from Borrow Site "0,"
which consists of a series of glacial tills separated by
alluvial and lacustrine materials.Processing and blend-
ing will be necessary to provide the required moisture
content and gradation and to remove any oversize mater-
ial.However,information to date indicates this can be
accomplished by selection of a vertical-face mining meth-
od and on-fill mixing and raking.
Material will be placed in 8-inch lifts at a maximum
moisture content of 3 percent above optimum moisture con-
tent,and compacted to 95 percent of the maximum density
obtained from the Modified Proctor Test (ASTM 0698).
-Fine and Coarse Filters
Fine and coarse filter material can be obtained from Bor-
row Sites E,I,and J.Borrow Site E is the preferred
primary borrow source for all the fi lter and alluvium
fill material in the dam.The material will require
processing to provide the proper gradations for the fine
and coarse filters.
F-4-9
-Alluvium Fill Material
The alluvium fi 11 can be obtained from Borrow Areas E,I,
and J.The upstream s-hell of the dam will be constructed
using processed river alluvium gravel with no more than 10
percent of the material less than 3/B-inch.The downstream
shell wi 11 be constructed using unprocessed alluvium fi 11
material,with mixing of a carefully controlled percentage
of waste work from excavations.
-Riprap Material
The riprap material (slope protection)will be obtained
from the oversize material from the various borrow areas,
Quarry A,and any other rock excavations.The riprap.
material will be placed on the entire upstream slope,and
in certain areas of the downstream slope of the dam as pro-
tection against wave overtopping and toe erosion.
(vii)Stability Analysis
Static and dynamic stabi lity analyses have been performed to
establish the upstream and downstream slopes of the Watana
Dam.A summary of the stability analyses is outlined in
Appendix FB.The analyses indicate stable slopes under all
conditions for a 2.40 horizontal to 1.0 vertical upstream
slope and a 2.0 horizontal to 1.0 vertical downstream slope.
Therefore,these slopes have been adopted for prel"iminary
design purposes unti 1 final design analysis and investiga-
tions show steeper slopes are stable.
(h)Watana Emergency Spillway Fuse Plug
The earthfill fuse plug,with a crest elevation of 2201.5,is locat-
ed in the upstream end of the unlined rock channel spillway.The
31.5 feet high fuse plug is designed to be eroded if overtopped by
the reservoir and since the crest is lower than the dam embankment,
the plug would be washed out prior to overtopping the main dam.
Details of the fuse plug design are presented in Appendix FA.
Static and dynamic stability analyses have been performed to estab-
lish the fuse plug embankment slopes.The studies indicate the
embankment slopes of 1:2.4 upstream and 1:1.5 downstream,are stable
under all conditions of loading.A summary of the stability
analyses is outlined in Appendix FB.The preliminary design is con-
sidered suitable for both operational stability and rapid failure if
overtopped.
F-4-10
-
4.2 -Devil Canyon
(a)Foundation Preparation and Treatment
-
(i )
(i i )
Mai n Dam
The enti re area under the dam wi 11 be excavated to sound,
fresh rock.In addition,the overburden 100 feet upstream
and downstream of the dam wi 11 be removed to enab le founda-
tion preparation.The overburden will be excavated to a
safe slope,generally 2H:lV.
Dental excavation of shear zones and weathered rock wi 11 be
performed.Such areas wi 11 be backfi lled with concrete as
necessary.Detached blocks of rocks will be removed or rock
bo lted and/or grouted.Rock overhangs wi 11 be trimmed and a
regular surface formed.
Grouting
-Consolidation Grouting
Consolidation grouting will be performed over the whole
area of the dam foundati on and wi 11 extend 100 feet up-
stream and downstream of the dam.
The consolidation holes will be at 10 feet spacing with
depth rangi ng from 30 to 70 feet.The ori entati on of the
consolidation holes wi 11 be such that they intersect the
majority of discontinuities.
-Curtain Grouting
The extent of curtain grouting is indicated in Plate F46.
The depth of the holes will be a maximum of 0.7H (where H
is the maximum head of water at that particular point of
the foundation)up to a maximum of 300 feet.On the right
bank,the grout curtain will extend under the thrust block
and spillway gate structure and beyond the powerhouse.The
curtain will be a minimum of 200 feet deep in this area to
ensure minimal seepage into the powerhouse cavern area.
The grout curtain will extend 100 feet below the excavated
foundation of the intake structure.
Since the underground powerhouse is to be unlined and
water pressures in the rock surrounding the powerhouse
wou ld cons i derab ly increase the rock support requi red,an
extensive grouting program coupled with a comprehensive
drainage scheme is proposed (Plate F46).
F-4-11
The grouting wi 11 be performed from tunnel galleries,the
general arrangement of which is shown in Plate F46.A maxi-
mum slope of 45 0 has been assumed for the inclined
galleries.
The 9rout galleries will be 10 feet by 10 feet,based on the
spac1ng of the grout and drainage curtains and the anticipat-
ed size of dri 11ing equipment.Although there is no indica-
tion of permafrost at the site to date,if permafrost is en-
countered,thawing will be carried out by circulation of wat-
er in the grout holes before grouting.
(iii)Drainage
-Dam
The grout galleries wi 11 be used for drainage.The drain-
age holes will be 3-inches in diameter and will follow a
slmilar arrangement to the grout curtain.
The drainage holes wi 11 be installed downstream from the
grout curtai n and generally extend 50 feet be 1ow the grout
holes.The spacing will be selected to ensure that the
maximum number of discontinuities are intersected.Extra
holes may be required in shear zones and in possible joint
planes.
Where possible,drainage holes will be drilled from the
galleries to prevent freezing.Where free draining of the
lowest grouting/drainage gallery is not possible,pumps
w'ill be provided to keep the lowest galleries free of
water.Access tunnels will be approximately 10 feet by 10
feet.Drainage holes will be drilled upward from the gall-
ery wherever possible to provide the most effective drain-
age system.Drainage curtains drilled from upper and lower
galleries wi 11 overlap by at least 10 feet.The drainage
curtain will be drilled from the gallery and inclined about
10 degrees downstream from the vertical.
-Caverns
Grouting in and around the powerhouse and transformer gall-
ery may be required to reduce excess seepage.Dra1nage
will be provided to relieve water pressure around the
caverns.
Drainage will be provided all around the caverns to a
depth generally in excess of the deepest rock bolt,and
seepage will be collected by pipes or channels and direct-
ed into the powerhouse drainage system.
Rock Guts
All cuts will have a surface drainage trench at the top to
prevent small rocks and soi 1 from washing down the cut.
Selective drilling of subhorizontal holes 1n the rock cuts
may be performed to release bui ld up of water pressure on
the faces of the rock cuts.
(:"-4-12
"""'I
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(iv)Intake Structure
The foundation for the intake structure wi 11 be on sound,
unweathered rock.Drai nage wi 11 be provi ded through the
concrete structure from the concrete/rock interface.
Rock excavation faces,against which the structural con-
crete is to be placed,should be approximately vertical.
Further stability analysis will be required when more in-
formation is available on joint shear strength,orienta-
tion,and structure location,but no stability or mass
structure shear weaknesses are expected to be found.
-
(v)Spi llway
The spillway will be founded entirely on rock.The grout-
ing and drainage curtains in the dam foundation and under
the thrust block will extend under the spi 11 way control
structure to reduce seepage under the structure and reduce
uplift pressures.
The drainage/grouting gallery will be formed in the con-
crete rollway of the control structure.This gallery will
be of similar size to the rock tunnel beneath the dam and
constructed as far upstream as possible to achieve a reduc-
tion in water pressure over the largest area of the founda-
tion.To minimize build up of ground water pressure be-
neath the spillway chute foundation,the concrete/rock con-
tact will be well drained.Steel anchor bars will also be
provided for increased stability.Preliminary calculations
indicate that these bars should be at 5-foot centers over
the foundation area.
Because of the susceptibility of the drains under the
spillway slab to freezing,a drainage gallery will be con-
structed at a minimum depth of 30 feet below the concrete
spillway slab,along the entire length of the spillway.A
fan of drain holes drilled from the surface drains will
drain into the drainage gallery.The gallery will be ap-
proximately 10 feet by 10 feet in size.The foundation for
the entire spillway will be consolidation grouted as re-q-
uired.The grouting will be to a depth of 20 feet based on
a grid of holes spaced 10 feet by 10 feet."Anchors will
also be provided from the spillway chute walls into rock.
F-4-13
(vi)Saddle Embankment Dam
-Foundation Excavation Preparation
All overburden beneath the proposed saddle dam will be
removed.The foundat ion area for the core and fi lters
will be excavated to sound rock,whil e the rockfil1
shells will be excavated to competent rock.The final
excavated foundation slopes will be no steeper than
1H:1V.The foundation will be regular in shape.Local
steep slopes and overhangs will be treated with concrete
or appropriately trimmed.
Dental excavation over and above normal excavation will
be performed in zones of intense shearing or alteration.
-Grouting
.Consolidation Grouting
The rock under the core,upstream fi lter,and down-
stream filter will be consolidation grouted to provide
a zone of relatively impermeable rock under the entire
contact.The consolidation grout holes will be drilled
on a 10 foot by 10 foot grid approximately 30 feet
deep .
.Curtain Grouting
The depth of grout holes beneath the dam will be 0.7 x
H,where H is the maximum head of water at that parti-
cular point on the foundation.The grout curtain will
have a minimum depth of 50 feet.
On the left abutment,the curtain will extend under the
fuse plug emergency spi 11 way and cont i nue 50 feet past
the spillway.
On the right side of the saddle dam,the curtain will
extend beneath the thrust block of the arch dam to meet
the main dam grout curtain.
The grouting will be carried out using the split spac-
ing method with primary holes at 40-foot spacing.
Using secondary,tertiary,and quaternary holes,it
will bring the spacing to 5 feet if required.A two-
row curtain will be required.The spacing between rows
will be 5 feet,with the holes in a staggered pattern.
F-4-14
-
-
-
.-
-
Grouting will be performed from a gallery running under
the dam along the center of the core.The gallery will
be a minimum of 50-foot depth into rock.Access on the
left side of the dam will be between the dam and emer-
gency spi 11 way;on the ri ght side access wi 11 be from
the main dam abutment drainage gallery.On the right
side,the gallery under the dam will slope at two per-
cent to connect with the abutment drainage gallery.
This arrangement allows free drainage of the gallery
into the main dam drainage system.The galleries will
be 10 feet by 10 feet in cross section.
Permafrost is not expected at the site,but isolated
frozen lenses may occur,in which case thawing will be
carried out prior to grouting.
-Drai nage
The grout gallery will also be used for drainage.The
drainage holes will be 3 inches in diameter and will fol-
low a similar arrangement to the grout curtain.The
drainage holes will be inclined downstream by 10 degrees
from tne vertical.
The drainage holes will be downstream from the grout cur-
tain and generally extend 50 feet deeper than the grout
holes.The spacing will be selected to ensure that the
maximum number of discontinuities are intersected and is
expected to be approximately 10 feet.Extra holes may be
required in the shear and fault zones.
(b)Rock Slopes and Foundation Design
....
(i )General Rock Slopes
Jointing was assumed as the controlling geologic structure
for rock slopes.Design slopes were selected considering
orientations and continuity of the joint set or sets in-
volved.Sets I and II were assumed to control while Sets
III and IV are localized,thus presenting minor problems.
Therefore,Sets I and II will be cut back to provide in-
trinsically stable slopes.Where Set III is present,flat-
ter slopes or heavy support may be required.Set IV joints
with 060°/40°NW orientation may present localized stabil-
ity problems.Other members of this set have shallow dips
and should not create problems .
F-4-15
-
The following table summari zes the slopes for each cut ori-
entat ion.
Strike Dip Cut Slopes
N-S E 4V:1H
N-S W 4V:1H
NE-SW SE 2V:1H
NE-SW NW 4V:IH
E-W N 4V:1H
E-W S 2V:IH
NW-SE NE 4V:1H
NW-SE SW 2.75V:IH ,..,
(ii)Devil Canyon Arch Dam
It is expected that the treated rock mass foundation modul-
us is in the range of 1x10 6 psi to 3x10 6 psi.However,
if the abutments do prove to be compressible,they may be
treated with pre-tensioned cable anchors,thrust blocks may
be used to distribute loads,or short adits can be driven
back to sound rock and backfi 11 ed with concrete to apply
loads deeper in the abutment.
(iii)Spillway and Intake Structure Foundations
The orientation of subhorizontal joints (Set IV)will con-
trol sliding stability of these structures.A better value
for shear strengths of these subhori zontal joi nts is re-
qui red before anchori ng requirements can be determi ned.
Anchors may not be required if these joints are rough and
irregular.No subhorizonta1 shear zones have been detected
so a friction angle of 35°was used in the sliding stabil-
ityana1ysis.
Design foundation bearing loads should be less than 5 ksf,
and the a110wab 1e beari ng load on "sound 11 rock wi 11 be
greater than 10 ksf,so foundation loads will not create
excessive differential deformations.These structures will
be founded on sound rock.
F-4-16
-
,-
(c)Tunnels and Penstocks
Orientations creating the least problems for the Devil Canyon site
tunnels are between 95 0 and 110 0 with an acceptable range of 90 0
to 120 0
•These tunnel orientations cross major shear zones at
high angles.Analysis of the jointing indicates that another
favorable orientation may be 175 0 to 185 0
•The primary tunnel or-
ientations follow a direction of 70 0 to 100 0
•
The penstock tunnels will be concrete-lined over their entire
lengths and steel linings will be included just upstream from the
powerhouse.These steel linings will be designed to withstand
full static and dynamic heads.Their lengths will be determined
when actual rock conditions are known.Contact grouting is re-
quired to insure good contact between the rock,concrete,and
stee 1.
Four penstocks of 20-foot di~leter are proposed.Penstock spacing
will be 2.5 times the diameter,center to center.If further
investigations prove excellent rock conditions in the penstock
area,spaci ngs may be reduced to twi ce the di ~leter.
-
-
-
-
(d)Caverns
( i )Support
Because of powerhouse sizes and shear zone spacings,sever-
al minor shear zones (less than 5-feet thick)may intersect
the powerhouse.These zones will require more than nominal
support.
The intersection of nearly vertical and horizontal joints
wi 11 create blocks in the crown requiring support.This
support will be provided by pattern bolting.A detailed
analysis will be performed when more specific geologic data
are available.
The crown rock bo lts recommended for pre 1imi nary des i gn
have a working load of approximately 80kips.The preferred
type is a tensioned,resin-anchored,and resin-encapsulated
rock bolt.Wall bolts will be similar to those described
in the tunneling section.
Rock bolts for other caverns in the powerhouse complex with
spans between 40 feet and 80 feet will use the same capac-
ity,spacings,and percentages of bolts as the powerhouse,
with bolt lengths equal to 1/3 of the span for the crown
and 1/10 of the wall height for walls.Shotcrete,sets,
concrete and wire fabric will be used as required.Caverns
with spans 1ess than 40 feet will be supported using the
tunnel criteria.
F-4-17
Where shear zones intersect underground openings,more ex-
tensive support may be required.Longer,higher-capacity
bolts,more closely spaced may be necessary.
(ii)Drainage
Drainage will be provided for the walls and crown to pre-
vent seepage from affecting their stability.Drain holes
will be provided,extending into the rock a distance equal
to the greatest rock bolt length or greater.Detailed
geology of the powerhouse area is required before the
drainage system can be fully designed.By selecting a good
to excellent rock body,grouting may be minimized.
(iii)Spacing
The rib spacing between the sides of caverns will be kept
to 1.5 times the largest cavern span.
(iv)Orientation
The most desirable orientation for caverns is either 090 0
to 120 0 or 175 0 to 185 0
•However,for definite orientation
and location,additional investigations and testing,using
borings and exploratory adits,are required.The selected
cavern orientation represents a compromise of rock support
and civil arrangement requirements.
(e)Devil Canyon Arch Dam
(i)Material and Thermal Properties
The materi al and thermal properties for the Devi 1 Canyon
arch dam are:
-unit weight of concrete -150 lb/ft3
-unit weight of water -62.4 lb/ft3
Static Properties
Concrete
ultimate uniaxial compressive
strength at 365 days 5000 ps i
allowable compressive stress ".~"••~~811o ••1250 psi
sustained modulus of elasticity GO •e ..110 ..Go <]I Q 3 x 106 psi
allowable tensile stress ••II ....0'"'OO"G"1IoIPOIt 325 psi
-Poisson1s rat 10 <lOO.OOCiOOlleItQlOO ••G"'.OCloClloIJO 0.2
F-4-18
-
-
....,
-Poisson's ratio 0.2
-
-
Rock
-ultimate compressive strength
allowable compressive stress
-static modulus of elasticity
20,000 psi
(unconfined)
5,000 psi
2 x 10 6 psi
-
-
Dynamic Properties
Concrete
uniaxial dynamic comrpessive
strength ..............•.............6,000 psi
-instantaneous modulus of
elasticity ..•..........•............5 x 10 6 psi
-allowable linear rapid loading
tens i 1e strength ...•................750 psi
-Poisson's ratio ............•........0.2
Rock
-properties assumed as for static conditions.
Thermal Properties
Concrete
-conductivity of concrete ...•..•.....1.52 Btu/ft/hr/oF
-specific heat ............•.....•...•0.22 Btu/lb/oF
-coefficient of thermal
expansion ...•....•......••..•..•..•.5.6xl0-6/ftjOF
-diffusivity ......•..•..•..•.••••....-0.046 ft 2/hr
(ii)General Parameters
The geometry of the dam is shown on Plate F42 and F43.
General criteria are as follows:
F-4-19
-normal maximum reservoir operating level ..Elevation 1455
-minimum reservoir operation level ..•..•..•Elevation 1405
-dam crest elevation ..•••......•...•.•.••..Elevation 1463
-minimum foundation level •.•..•..•~.•.....•Elevation 820
(iii)Stability Analysis
The arch dam has been analyzed for static loadings and
seismically-induced ground motion using the computer pro-
gram,(ADAS)developed by the USBR based on the trial load
method for three-dimensional structures and (SAPIV)for the
two-dimension crown cantilever.(See Ref.No.2,Appendix
B5).
The loads and conditions analyzed follow:
Static Loads
-self-weight of the dam;
hydrostatic pressure from the reservoir;
-temperature changes;and
-ice load.
Dynamic Loads Caused by Seismic Events
-(0.57g)seismic shaking of the dam;and
-hydrodynamic loads from the reservoir.
Loading Combination
(a)Usual Load Combination
This consists of groups of sustained loadings which can
occur simultaneously over the design life of the dam.
ULl Dam self wei ght +hydrostatic load with reservoir
at EL 1455;
UL2 Dam self weight +hydrostatic load with reservoir
at EL 1405;
UL3 -As ULl plus extreme winter temperature effects;
and,
UL4 -As UL2 plus extreme winter temperature effects.
(b)Extreme Load Combination
This consists of the combination of sustained loads
together with short-durati on loads caused by sei smi c
motion.
ELI -UL1 +extreme earthquake loading.
F-4-20
-
Resu lts
The results of the above loading combinations are repre-
sented on Plates F45A and F45B.The ice load condition
which is not shown in the above mentioned Plates when
applied to the ULl combination produced a maximum stress
increase of 12 psi in the arch stresses and 11 psi in the
cantilever stresses.
(f)Sad d 1eDam
,~
.-I
~.
(i )
(i i)
(iii)
Genera 1
The design philosophy for the saddle dam is essentially the
same as that for the main dam at Watana.The most signifi-
cant difference is the use of rockfi 11 in the shells in-
stead of the river gravels used at Watana.
Dam Cross Section
The central vertical core wi 11 be protected by fine and
coarse fi lters on both upstream and downstream s lopes and
supported by grave 1 and rockfi 11 she 11 s.The core wi 11
have a crest width of 15 feet and side slopes of 1H:4V to
provide a core thickness to dam height ratio slightly in
excess of 0.5.
The wi de fi lter zones wi 11 provi de suffi ci ent materi alto
seal any cracks which might occur in the core due to
settlement or as the result of seismic displacement.
The saturated sections of both she lls wi 11 be constructed
of compacted clean gravel or rockfill,processed to remove
fine material in order to minimize pore pressure generation
and ensure rapid dissipation during and after a seismic
event.Since pore pressures cannot develop in unsaturated
sections of the downstream shell,the material in that zone
wi 11 be unprocessed rockfi 11 from surface or underground
excavations.
Protection on the upstream slope will consist of a 10-foot
1ayer of ri prap.
Dam Materi a 1
No source of materi a 1 su itab le for the core of the sadd le
dam has been identified closer than the borrow areas at
Watana (Sites D and H).The current proposal is to use
Site D for core material for the saddle dam.The in-place
volume of core material is 306,000 cubic yards.
F-4-21
The fi lter materi a 1 wi 11 be obtai ned from the ri ver depos its
(Site G)immediately upstream of the main arch dam.This area
will also be exploited for concrete aggregates.The total vol-
ume available in Site G is estimated to be 6 million cubic
yards,while the concrete aggregate demand is some 2.7 million
cubic yards.The estimated volumes required for the dam are
228,OOO"and 181,000 cubic yards for the fine and coarse filters,
respectively.Surplus material from Site G will be used in the
upstream shell.The balanceof the shell material will be rock-
fill obtained primarily from the excavations for the spillways.
The total rockfi 11 required wi 11 be approximately 1.2 mi llion
cubic yards.The proportion of sound rock suitable for use in
the dam,which can be obtained from the excavations,cannot be
accurately assessed at this stage,but it is proposed to make up
any shortfall by deepening and extending the emergency spillway
cut.If,however,the excavated rock is found unsuitable for
construction material,that Quarry Site will be utilized as a
primary rock source.
(iv)Stability Analysis
Speci a 1 precaut ions have been taken to ensure stabi 1ity under
earthquake loading by the use of processed free draining gravel
and rockfi 11 in the saturated zones of the dam,the incorpora-
tion of very wide filter zones,and the removal of all unconsol-
idated natural material from beneath the dam.
Static and dynamic stability analyses of the upstream slopes of
the Watana dam,have confirmed stab le slopes under all condi-
tions for a 2.4H:1V upstream slope and a 2H:1V downstream slope
(see 4.1(g)(vii).However,further analyses will be required
for the Devil Canyon saddle dam.
(g)Devil Canyon Emergency Spillway Fuse Plug
The earthfill plug,with a crest elevation of 1465.5 is located in the
upstream end of the unlined rock channel spillway.The 31.5 feet high
fuse plug is designed to be eroded if overtopped by the reservoir and
since the crest is lower than the dam embankment,the plug would be
washed out prior to overtopping the main dam.
Details of the fuse plug for Watana Dam are outlined in Appendix FA.
The designs for Watana and Devil Canyon are identical.
Static and dynamic stability analyses have been performed to establish
the fuse plug embankment slopes.The studies indicate the embankment
slopes of 1:2.4 upstream and 1:1.5 downstream are stable under all
conditions of loading.A summary of the stability analyses is outlined
in Appendix FB.The preliminary design is considered suitable for both
operational stability and rapid failure if overtopped.
F-4-22
-
~.
5 -HYDRAULIC DESIGN CRITERIA
2193.5 ft MSL 1455 ft MSL
-I
-
5 -HYDRAULIC DESIGN CRITERIA
5.1 -River Flows
Average annual flow
Maximum average monthly flow (June)
Minimum average monthly flow (March)
5.2 -Design Flows
Probable Maximum Flood (Routed outflow):
Derived from SSARR watershed model.
Reservoirs assumed at normal maximum
operating level.
Project Design:
1:10,000-year flood inflow.Derived
from annual flood series frequency
analysis.Reservoirs assumed at normal
maximum operating level.
Environmental Criteria:
1:50-year flood (routed).Derived from
annual and summer flood series frequency
analysis with normal generation assumed.
Summer flood series controls design with
full reservoir conditions in August and
September.
Diversion Design:
1:50-year flood (routed)at Watana
1:25-year flood at Devil Canyon.Annual
flood series frequency analysis.Devil
Canyon diversion assumes normal power
operation and storage at Watana.
5.3 -Reservoir Levels
Normal Maximum Operating Level:
Minimum Reservoir Level:
Maximum Reservoir Level:"
PMF surcharge level
1:10,000-year surcharge level
F-5-1
Watana
7,990 cfs
42,800 cfs
570 cfs
293,000 cfs
156,000 cfs
31,000 cfs
80,500 cfs
2185 ft MSL
2065 ft MSL
2201 ft MSL
2201 ft MSL
Devi 1 Canyon
9080 cfs
47,800 cfs
660 cfs
345,000 cfs
(routed through
Watana
Reservoir)
165,000 cfs
(routed through
Wat an a
Reservoir)
39,000 cfs
39,000 cfs
1455 ft MSL
1405 ft MSL
1466 ft MSL
1466 ft MSL
...,
5.4 -Reservoir Operating Rule
1:50-year surcharge level (l:50-year
surcharge due to operating rule for
restricted discharges and reduced
nitrogen supersaturation.)
Reservoirs allowed to surcharge
before main spillway operation.
Outlet operational when Watana
reservoir level exceeds
Elevation 2185.5.
Watana
2193 ft MSL
Dev i 1 Canyon
1455 ft MSL
Allowable reservoir surcharge above
normal maximum operating level.
5.5 -Reservoir Parameters
8.5 ft
38,000 acres 7800 acres
3,740,000 acre-ft 350,000 acre-ft
9,470,000 acre-ft 1,090,000 acre-ft
Reservoir area at normal
maximum operating level.
Reservoir Live Storage:
(Storage between normal
maximum and minimum reservoir
levels)
Reservoir Total Storage:
(At normal maximum operating
leve 1)
5.6 -Freeboard (Hydraulic Considerations)
o ft
3 ft
8 ft
5ftAllowanceforwaveheightand
run up
Allowance for restricted
discharges and reduced nitrogen
supersaturation above normal
maximum operation level
5.7 -Criteria
(a)Spillways
(i)Capacity
Pass PMF while maintaining the integrity of the main
water retaining structures.Limited damage to water
passages is allowable.
-Pass routed 1:10 ,OOO-year flood with no damage.An out-
let facility for general operation with a main spillway
operated only for short duration is acceptable.
F-5-2
-Pass routed 1:50-year flood without elevating nitrogen
supersaturation levels above 116 percent.
(i i )"Chute
-Maximum velocity 90 ft/s without aeration.
(iii)Energy Dissipation
-Minimum radius of flip bucket greater than 7 x depth of
design flow.
Plunge Pool
(iv)Diversion
Minimum release during
impounding
(v)Reservoir Levels
Determined by downstream
flow constraints.Range
of 1000 to 19,000 cfs.
Normal maximum operating limit Maximum elevation of 2250
MSL at Watana.Level
should be as low as pos-
sible.Economic benefits
of any level over 2000 MSL
must be clearly demon-
strated.
Minimum operating level As close to normal maximum
as poss ib1e.Economi c
benefits of any level
lower than 2100 MSL must
be clearly demonstrated.
Average minimum operating level As close to 2150 MSL or
higher.Economi c benefi t
of any level lower than
2150 MSL must be clearly
demonstrated.
--
.....
(vi)Reservoi r Operat ion
Downstream discharge during
operat;on
F-5-3
On a daily basis,dis-
charge from tne most down-
stream structure should be
constant;thi s can be ac-
complished through base-
load operation or a
reregulation structure.
Reservoir operation should
provide flows consistent
with downstream flow
mitigation plan.
,~
6 -EQUIPMENT DESIGN CODES AND STANDARDS
-
IPi'l'I\!Ilil
6 -EQUIPMENT DESIGN CODES AND STANDARDS
6.1 -Design Codes and Standards
(a)Turbines
-ASME Boiler and Pressure Vessel Code,Section VIII,Pressure
Vessels;
-ANSI Standard B49.1;
-ANSI Standard B31.1 -Power Piping;
-AWS Standard 01.1 -Structural Welding Code;
-IEC Publication 193 lIInternational Code for Model Acceptance
Tests of Hydraulic Turbines ll
;and
IEC Publication 41 "International Code for Field Acceptance
Tests of Hydraulic Turbines,Storage Pumps and Pump-Turbines.
(b)Gate Equipment
-AISC Specjfication for Design,F~brication and Erection of
Structural Steel for Buildings;
-AWS 01.1 -Structural Welding Code;
ACI 318 -Building Code Requirements for Reinforced Concrete;
-ASME Boiler and Pressure Vessel Code,Section VIII,Pressure
Vessel s;*and
-ANSI Standard B31.1.*
(c)Valve Equipment
-ASME Boiler and Pressure Vessel Code,Section VIII,Pressure
Vessels.
(d)Crane Equipment
-CMAA Specification No.70 -Specifications for Electric Overhead
Travel ing Cranes;
-CMAA Specification No.74 -Specifications for Single Girder
Overhead Traveling Cranes;and
-OSHA Standards.
*Hydraulic hoist design.
F-6-1
(e)Elevators
-ANSI Standard A17.1;and
-State Building Codes.
(f)Mechanical Systems
-
-ANSI Standard B31.1
-AWS Standard Dl.1
-NFPA Standards
-ASME Boiler and Pressure Vessel Code,
Sections 2t 8 and 9
-API Standard 650 t Welded Steel Tanks
for Oi 1 Storage
-ANSI Standard D31.3 t Petroleum
Ref'ining Piping
-AWWA St and ard s
-Environmental Protection Agency
-ASHRAE Guide
-State Sui lding Codes
Applicable Systems**
It 2,3,4 t 6 t 7 -It 2,3t 4 t 5,6,7
3,5 t 8
3,4
5
5
6
6
8
6 t 2
6.2 -General Criteria
(a)Turbi nes
(i)Operation
The turbines will be capable of continuous operation at
speed-no-load and at any gate openi n9 between 100 percent
and 50 percent full gate output without objectionable sur-
ges in power t detrimental vibrations or objectionable nois-
es.The turbines will be designed for continuous operation
at maximum runaway speed.
(i i)Stresses
Stresses in turbine components under normal operating con-
ditions t including pressure rise on full load rejection,
will not exceed 1/3 of the yield strength for materials of
steel construction.For miscellaneous materials t stress
levels will not exceed the following:
**l.
2.
3.
4.
5.
6.
7.
8,
Service Water Systems
Domestic Water Systems
Fire Protection Systems
Compressed Air Systems
Oil Storage and Handling Systems
Drainage Systems
Dewatering Systems
Heating and Ventilating Systems
F-6-2
Cast iron 2000 1b/in 2 tension
10,000 lb/in2 compression
-Bronze bearings.............3000 lb/in 2
-Babbitt bearings 5001b/in2
On extreme loading conditions such as operation at runaway
speed,stress levels may be increased provided they do not
exceed 2/3 of the yield strength of the material.
-Critical Speed
The first critical speed in shaft bending for the com-
bined turbine and generator will be at least 125 percent
of the maximum runaway speed of the turbine.
Cavitation
The maximum metal loss (in 1b)due to cavitation pitting
during any BOOO-hour operating period will not exceed 0.1
times the discharge diameter of the runner (in ft).
(b)Gate Equipment
"""
(i )
(i 1)
Gates and Guides
For normal loading conditions including hydrostatic and
applicable hydrodynamic and lifting loads,stress levels on
structural components wi 11 not exceed those permitted in
the AISC Specification for Design,Fabrication and Erection
of Structural Steel for Buildings.Stresses in welded and
bolted connections will not exceed 90 percent of the values
permitted by the AISC Specification.For gates subjected
to dynami c loading,stresses in structural components and
in connect ions will be reduced a further 20 percent.For
crowned gate wheels on a flat track,hertz contact stresses
(compressive)will not exceed 250 times BHN (in lb/in2).
For flat wheels or rollers on a flat track,the load (in
lb)per inch width of roller contact will not exceed 1600
times the roller diameter.
On extreme loading conditions with the gate becoming jammed
on raising,stress levels may be increased by 33 percent.
A corrosion allowance of 1/16-inch will be allowed on all
gate components in contact with water.
Unless provision is made for forcing at gate down,the pre-
ponderance for all gates will be at least 15 percent assum-
ing static friction coefficient.
Hoi sts
Hydr au 1ic ho i sts wi 11 be des i gned in·accord ance wi th the
ASME Boiler and Pressure Vessel Code,with a rated capacity
of at least 140 percent of the calculated lifting loads and
a max i mum working pressure of 2000 1b/in2 .The cyl i nder
wi 11 also conform to the criteri a recommended by the Na-
tional Fluid Power Association.
F-6-3
For wire rope hoists,stresses will not exceed 1/3 of the
yield strength of the material for normal loading including
an allowance for impact.The load on wire rope will not
exceed 1/5 of the mi nimum breaking strength.For extreme
loading conditions with a gate becoming jammed,stress lev-
els may be increased provided they do not exceed 67 percent
of the yield strength of the material.For extreme loading
cond it ions,the load 0 n wi re rope wi 11 not exceed 80 per-
cent of the minimum breaking strength.
(c)Valves
Val ves wi 11 be des i gned in accord ance wi th the ASME 80 il er and
Pressure Vessel Code.For fixed cone valves,special attention
will be given to the prevention of vibration and cavitation.
(d)Trashracks
Trashracks will be designed with the allowable stresses permitted
in (b)above for gate equipment.Rack vibration will also be con-
sidered in the design.
(e)Cranes
Cranes will be designed in accordance with the applicable CMAA
Specification.For cranes which handle gates,a jammed gate con-
dition will be considered where stress levels and wire rope loads
will not exceed those permitted in (b)above for extreme loading
on wire rope hoists.
(f)Mechanical Systems
Full redundancy will be provided for pumps,strainers,and similar
equipment which are critical for generating unit operation.
6.3 -Diversion Structures and Emergency Release Facilities
(a)Diversion Control Gates
Fixed roller vertical lift gates will be provided at the intakes
to the diversion tunnels.The gates will be used for closure of
the diversion tunnels to permit plugging operations.The gates
wi 11 also be used to control flows as necessary when the water
level is below the gate opening lintel to prevent passage of ice
through the diversion tunnels.
The gates will have downstream skinplates and seals.Provision
will be made for gate and guide heating if the gates are used for
control during cold weather.The gates will be operated by fixed
hoists mounted in a tower and bridge structure.
The gates in the upper diversion tunnel at Watana wi 11 be removed
once tunnel plugging is complete.The gates for the other tunnels
will'have retractable rollers for transfer of hydrostatic loads to
the guides after diversion closure when the head increases as the
reservoir is impounded.
F-6-4
(b)High Pressure Sl ide Gates (Watana)
High pressure slide gates will be installed in the tunnel plugs in
the upper diversion tunnel at Watana.The slide gates will be
used for:
-Passing required releases during reservoir impoundment;and
-Emergency draining of the reservoirs throughout the life of the
plant.
(c)
The gates will be installed after initial closure of the diversion
tunnel.The arrangement will consist of three sets of three gates
in series.Each set will consist of two gates in an upstream plug
(one emergency and one operating gate)and one operating gate in a
downstream plug.The area between the plugs will act as an expan-
sion chamber to assist in energy dissipation.The gates will be
designed to operate at full or partial opening for heads up to the
low operating level of the outlet facilities.When closed,the
gates will withstand full reservoir level.The two operating
gates in series will be operated at equal openings at all times to
effectively balance the head across the gates.
Trashracks (Watana)
Course trashracks will be installed at the Watana upper diversion
tunnel at the same time the high pressure slide gates are in-
stalled.Provision for rack removftl is not considered necessary.
The criteria for the trashracks are as follows:
-
Maximum bar spacing 2/3 of the high pressure
slide gate width
Maximum velocity through racks (net)12 ft/s
Design differential level 40 ft (approximate)
(d)Diversion Tunnel Stoplogs
Stoplog guides and stoplogs will be provided at the downstream end
of the diversion tunnels to permit tunnel dewatering after diver-
sion closure for plugging operations.The stoplogs will be han-
dled by a mobile crane with a follower.
6.4 -Main Spillway
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(a)Spi 11 way Gates
The spillway gates will be fixed wheel vertical lift gates oper-
ated by a double drum wi re rope hoi st mounted on a tower and
bridge structure.The hoist housing will be enclosed and heated.
Prov is i on wi 11 be made for i nsta11 at i on of heaters in the gates
and guides.
F-6-5
(b)Stoplogs
A set of stoplog guides will be provided upstream from each spill-
way gate to permit inspection of the spillway gate guides or rais-
ing the spillway gate for maintenance without passing water over
the spi llway.
One set of stoplogs will be provided to be handled by ,a mobile
crane and follower.
6.5 -Outlet Facilities
(a)Fixed Cone Valves
Fixed cone valves will be used to pass normal discharges,other
than the flows through the powerhouse.The valves will also
assist in passing required release during reservoir impoundment.
At Watana,a single tunnel with a manifold and six valves will be
provided.Devil Canyon will have seven valves and individual con-
duits for each valve.
The valves will be selected within current experience with respect
to valve size and design head.In sizing the valve,the cylin-
drical gate opening will be assumed to be restricted to about 80
percent of its theoretical maximum to prevent possible vibration~
Each valve body will be heated for winter operation.A heated
valve gallery will be provided with crane equipment for servicing
and maintaining the valves.
(b)Ring Follower Gates
One ring follower gate will be provided immediately upstream from
each fixed cone valve to:
-Relieve the hydrostatic load on the valve when it is not in
operation;
-Permit inspection and maintenance of the valve;and
-Close under full flow conditions in the event of malfunction of
the valve.
The ring follower gate will be located within a heated enclosure
with suitable provision for servicing the equipment.
(c)Upstream Maintenance Gate
Provision will be made for installation of a gate at the upstream
entrance to the outlet tunnel.At Watana,fixed wheel gates will
be provided which can close under flowing water conditions.Bulk-
head type gates will be provided at Devil Canyon because of the
extremely high head.
F-6-6
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At Watana.because of the single tunnel.the gates will have fixed
hoists.A gantry crane will be used to handle the gates at Devil
Canyon.
(d)Ttashracks
Trashracks will be provided at the upstream end of the outlets.
Because the valves serve as the primary discharge facilities.con-
sideration will be given to making provision for rack removal.
The criteria for the trashracks will be as follows:
Maximum velocity (net)12 ft/s
Spacing 0.1 x valve size (approximate)
Design differential head 40 ft (approximate)
6.6 -Power Intake
(a)Trashracks
Trashracks wi 11 be install ed upstream from each intake openi ng.
Provision will be made for rack removal.
The criteria for the trashracks will be as follows:
~-
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Maximum velocity (based on gross area)5 ft/s (approx.)
Bar spacing maximum spacing not
to exceed minimum
distance between
runner blades
Design differential head 20 ft (approx.)
(b)Intake Gates
Fixed wheel or roller type vertical lift gates will be installed
at the entrance to each penstock.The gates will be used to per-
mit dewatering of the penstock and turbine water passages for tur-
bine inspection and maintenance and for closure in an emergency in
the event of loss of control of the turbine.
The gates will be operated by individual fixed hoists.
(c)Intake Bu1 khead Gates
Intake bulkhead gates will be provided for installation upstream
from the intake gates.The gates will be handled by a gantry
crane or overhead traveling crane.Sufficient gates for one in-
take opening at each project will be provided.
F-6-7
(ct)Water Level Shutters
Removable shutters will be installed in the intake at Watana and
Devil Canyon to permit drawing off water at selected elevations.
One set of shutters will be provided at each intake opening.The
shutters will be designed for approximately 15 feet of differen-
tial head.The arrangement will be such that a higher differen-
tial head will not occur.
5.7 -Powerhouse
(a)Turbines
The turbines wi 11 be vert ical shaft Franc is type directly con-
nected to synchronous generators.The turbines will have steel
spiral cases and concrete elbow draft tubes.
The turbine capacity will be established on the basis of the mlnl-
mum reservoir level in December (the peak demand month).At
Watana,the unit output in December with minimum reservoir level
wi 11 be 170 MW.At Devil Canyon,the output wi 11 be 150 MW with
minimum December reservoir level.
The preliminary turbine data have been established as follows:
-
Watana
Number ,..........6
Head (net)
-rat ed 680 ft
-maximum ...................•..725 ft
-minimum......................600 ft
Power at rated speed 250,000 hp
Synchronous speed 225 rpm
Specific Speed 32.4
Devi 1 Canyon
4
590 ft
603 ft
541 ft
225,000 hp
225 rpm
35.0
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The design or rated head of the turbines for both Watana and Devil
Canyon will be the weighted average operating (net)head.
The specific speed of the turbines will be selected within current
experience with respect to head.
(b)Powerhouse Cranes
The powerhouse cranes will be of the electric overhead traveling
type with main and auxiliary hoists.The cranes will be used
for:
-Installation of the turbines,generators,and other equipment;
and
-Dismantling and reinstallation of equipment during maintenance
overhaul once the station is in operation.
F-5-8
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Each station will have two cranes.The combined main hoist capa-
city of the two cranes will be at least equal to the weight of the
generator rotor plus lifting beams.
(c)Draft Tube Gates
Draft tube gate guides will be provided at the end of each.draft
tube to permit dewatering of the turbine water passages for in-
spection and maintenance of the turbines.
The draft tube gates will be of the bulkhead type handled by a
traveling gate crane.
(d)
(e)
Miscellaneous Mechanical Equipment
Miscellaneous mechanical equipment will include:
- A passenger elevator in the powerhouse;
-An access elevator from the surface to the powerhouse;
-"Alimak"type inspection hoists in the cable shafts;and
-Small motori zed or hand-operated monorai 1 hoi sts or·A-frames
provided where necessary for servicing miscellaneous equipment.
Mechanical Services
The mechanical services within the powerhouse will include:
-Station service water systems
·water supply
·cool ing water
·domestic water
-Fire protection
·fire protection water system
·sprinkler system
portable fire protection system
F-6-9
Compressed air system
service area system
tailwater depression air
governor air
circuit breaker air
-Oil storage and handling
·transformer oil system
·governor and lubricating oil system
-Drainage and dewatering system
clearwater drainage
·unit dewatering and filling system
·sanitary drainage system
-Heating and ventilating system
6.8 -Tai lrace Tunnels
(a)Stoplogs
Stoplog guides and stoplogs will be provided at the downstream end
of the tailrace tunnels to permit dewatering of the tunnels for
inspection and maintenance.The stoplogs will be handled by a
mobile crane with a follower.
At Watana,where there will be two tailrace tunnels,stoplog
guides and stoplogs will be provided for the tunnel intake (in the
surge chamber)to allow dewatering of one tailrace tunnel while
still permitting plant operations using the other tunnel.The
stoplogs will be handled by a traveling gate crane.
F-6-10
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APPENDIX FA
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APPENDIX FA -WATANA EMERGENCY SPILLWAY
1 -Selection of Spillway Design
1.1 -Introduction
The basic criteria for the Emergency Spillway are that it shall not
come into operation until the reservoir elevation reaches Elevation
2200 and that the capacity of the spillway shall be for the PMF routed
through the reservoir.In addition,there must be sufficient freeborad
on the main dam and rel ict channel saddle dam when the emergency sp;11-
way ;s passing the PMF as safeguard against overtopping the dam or
breaching the reservoir rim.
A number of alternative arrangements and designs were considered for
the Watana site.It was concluded that the most appropriate alterna-
tive,considering project economics,safety and operational reliabil-
ity,was to utilize two spillways.The gate-controlled service spill-
way would carry flows in excess of the capacity of the power plant and
all flows up to the critical reservoir level at Elevation 2200.The
emergency spillway would come into operation at that elevation and be
designed to carry the PMF.
The following alternative emergency spillway designs were considered:
-Uncontrolled open-cut channel;
-Gated spillway;and
-Open-cut channel with fuse plug.
These alternatives are discussed below.
1.2 -Uncontrolled Open-Cut Channel
An uncontrolled open-cut channel has the obvious advantage of security.
The only risks are cut slope slides into the channel but such material
would be removed by regular maintenance and,in any event,would be
unlikely to seriously impede PMF discharges.
However,to maintain the criteria stated above,the spillway sill would
have to be at Elevation 2200.To minimize the height of the main dam,
the depth over the sill at PMF flow would have to be as small as possi-
ble.At the same time,maximum reservoir level is limited by the
saddle elevation in the rel ict channel.An open cut channel to sat-
isfy both criteria would have to be very wide (in excess of 1000 feet),
would involve extensive excavation and would encroach into the relict
channel,where special measures would be necessary to ensure stability
of the spillway under PMF flows.
FA-1
Alternatively,the spillway sill cold be lowered to incorporate the
spillway cut in sound rock,but this could only be achieved by lowering
normal operating levels in the reservoir which would adversely affect
the project economics.
An uncontrolled open-cut spillway was,therefore,considered unsuitable
for the Watana site.
1.3 -Controlled Open Cut Spillway
To satisfy all criteri a requires that the emergency spi llway not come
into operation until the reservoir level reaches Elevation 2200 but
that once that level has been reached,the PMF flood will not result in
significant surcharging above that elevation.
Two methods of achi evi ng these requi rements were studi ed;a gated
spillway and a fuse plug.
(a)Gated Spillway
The gated spillway alternative was considered and costed and
proved to be significantly more expensive than a fuse plug in
construction and operating costs.Gates were considered less
desirable than either an open cut or a fuse plug from a safety,
re1 i abi 1ity and rnai ntenance standpoint.Mechanical gates would
require long-term maintenance and service throughout the project
lifetime.In addition,the gates would require operator action
and the effectiveness of the spillway could be jeopardized by
human error.
(b)Fuse Plug Closure
Fuse plug closure was considered most desirable from a rea1iabi1-
ity standpoint,both because it is a IIpassiveu system that does
not require operator action to function,and it does not have the
electrical and mechanical risks of failure of a gated installa-
tion.
From an initial cost standpoint,the fusep1ug spillway has a lower
cost than an open-cut spillway due to the greater flow depth,
wh i ch is ach i eved fo 11 owi ng wash-out of the plug,wi th resu 1t ant
order-of-magnitude reduction in channel excavation requirements.
The earth-fill fuse plug has significantly lower construction
costs than a gated installation.Annual maintenance costs for a
fuse plug in an open-cut spillway would be lowest,with mainten-
ance limited to minor repair of face materials,annual checks to
ensure the crest and pilot channel elevations are maintained,and
application of herbicides to prevent development of plant growth
on the downstream face of the plug.
FA-2
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Because the emergency spillway is never intended to be used
(reservoir operation is designed to safely pass all floods up to
the PMF event without emergency spillway use),the capital i zed
rep 1acement cost of the plug after use does not come into con-
sideration.
1.4 -Recommended Emergency Spillway
Based on the above discussions,the fuse plug spillway was determined
to be the most economic,safe and reliable design for the Watana
arrangement.
2 -FUSE PLUG DESIGN
The selected fuse plug design was the result .of four primary criteria:
-High seismic stability;
-High static stability;
-High resistance to failure by seepage;and
-Low resistance to failure by overtopping.
The fuse plug is primarily a dam,since under normal operating condi-
tions,the spillway approach channel will be flooded and there will be
up to 15 feet of water acting against the fuse plug.The selected
section (Exhibit F,Plate F18)was developed under the first three
criteri a along the same 1ines as the main dam,to ensure security
during annual pool fluctuations from base (Elevation 2170)to Elevation
2185,and flood surcharging to Elevation 2194.At Elevation 2194,with
design wave of 6 feet,the security of the structure was considered
adequate,but some form of floating breakwater may be advisable to
reduce wave action within the approach channel.
To insure rapid failure by overtopping,several variations were made in
the design from that of the main dam.The material in the downstream
shell is designated as select,washed and sorted gravel.Removal of
cohesive properties will ensure rapid erosion.The clean nature of
this material also serves to drain any seepage which may occur through
the core during normal operation.The core is inclined with the base
upstream to induce rapid collapse by undermining when the downstream
shell material is eroded when water overtops the plug.
The selected shell particle size was based on a requirement for rapid
erosion while still maintaining a pervious shell that will readily
drain precipitation and seepage and so minimize buildup of ice in the
interior of the pl ug.The crushed stone and riprap 1ayers were se-
1ected to provi de the necessary protect ion from erosion by rainfall,
snow-slump erosion,and reservoir wave and ice scouring .
FA-3
Thelllode of failure of the fuse plug is as follows:
-Flood filling of the pilot channel at Elevation 2200;
Headwall erosion at the downstream fine filter cap,resulting in
gullying of the fine filter;
-Progressive gullying of the downstream shell and filter;
-Failure of the core cap,either by gullying in the pilot channel area
or by underminng by washout of the downstream filters and shell.
(These failures could occur simultaneously but,if the core is
frozen,its failure would probably be the result of undermining);
and
-Progressive undermining failure of the core and filter due to washout
of the downstream shell when the whole plug is overtopped concurrent
with lateral erosion of the plug from the pilot channel area.
The riprap and upstream shell materi al are not expected to restrict
flow,because,by the time erosion extends to the upstream riprap
contact,a hydraulic head of 30 to 32 feet will be eroding the plug on
a gradient of approximately 25 percent.This slope will be ITOre than
adequate to erode all particle sizes in the plug and wash them out of
the spillway channel.
As protection against delayed erosion of the pilot channel,general
overflow of the plug will occur at Elevation 2200,causing general
gullying and washout of the downstream face.
3 -FUSE PLUG OPERATIONAL PROCEDURES
The following operational and maintenance procedures are anticipated to
provide added security to the fuse plug design:
-Routine maintenance to ensure crest elevation and pilot channel are
maintained in a clear,clean,level state and at the proper eleva-
t ions;
-Annual herbicide application to ensure no cohesive or deep-rooted
vegetation will grow on the fuse plug;
-Standard operational procedure to move excavation equipment to the
fuse plug at any time pool level exceeds a pre-set elevation.The
equipment waul d be standard project maintenance equi pment such as a
backhoe or dragline and would be used to accelerate crest breaching
or remove any blockages as necessary if the fuse plug were over-
topped;and
FA-4
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- A contingency plan for explosive demolition utilizing pre-placed
vertical pipe explosive chambers.The explosive demol ition would be
a part of the state emergency preparedness plan,and personnel and
explosives could be put on standby at the damsite if the combined
hydrologic,reservoir level and meteorologic conditions necessary for
a major (greater than 10,000 year flood)flood are present or
threaten.
4 -SUMMARY
In summary,it is considered that a fuse plug design is preferable to a
gated outlet fac il ity,in 1ieu of a vi able open-cut emergency spi 11 way
configuration.The design is considered to be suitable,at the pre-
1iminary design level,both for long-term operational stabil ity and
resistance to premature failure;and to assure rapid failure if over-
topped.The possibility of frozen moisture in the plug has been re-
duced by assuring an extremely free-draining material in the shells and
filters,so that aside from a thin surficial snow-filled layer,the
plug will be in a surface-saturated moisture condition at the worst,
and in most areas,dryer than that.This limited amount of moisture
will rapidly thaw under the effect of the overflowing water and is not
expected to significantly retard the progressive failure mechanism .
FA-5
TABLES
J ]1 j i J 1 I ~J 1 ~)~-l -~-~-1
TABLE F.1:PRE-PROJECT FLOW AT WATANA (CFS)
YEAR OCT NOV DEC JAN FEB ~R APR ~Y JUN JUL AUG SEP ANNUAL---
I 4719.9 2083.6 1168.9 815.1 641.7 569.1 680.1 8655.9 16432.1 19193.4 16913.6 7320.4 6648.1
2 3299.1 1107.3 906.2 808.0 673.0 619.8 130:2.2 11649.8 18517.9 19786.6 16478.0 17205.5 7733.7
3 4592.9 2170.1 1501.0 1274.5 841.0 735.0 803.9 4216.5 25773.4 22110.9 17356.3 11571.0 7776.1
4 6285.7 2756.8 1281.2 818.9 611.7 670.7 1382.0 15037.2 21469.8 17355.3 16681.6 11513.5 8035.2
5 4218.9 1599.6 1183.8 1087.8 803.1 638.2 942.6 11696.8 19476.7 16983.6 20420.6 9165.5 7400.4
6 3859.2 2051.1 1549.5 1388.3 1050.5 886.1 940.8 671 a.1 24881.4 23787.9 23537.0 13447.8 8719.3
7 410:2.3 1588.1 1038.6 816.9 754.8 694.4 718.3 12953.3 27171.8 25831.3 19153.4 13194.4 9051.0
8 4208.0 2276.6 07.0 1373.0 1189.0 935.0 945.1 10176.2 25275.0 19948.9 17317.7 14841.1 8381.0
9 6034.9 2935.9 2258.5 1480.6 1041.7 973.5 1265.4 9957.8 22087.8 19752.7 18843.1 5978.7 7769.4
10 3668.0 1729.5 1115.1 1081.0 949.0 694.0 885.7 10140.6 18329.6 20493.1 23940.4 12466.9 8011.0
11 5165.5 2213.5 167:2.3 1400.4 1138.9 961.1 1069.9 13044.2 13233.4 19506.1 19323.1 16085.,6 7954.0
12 6049.3 2327.8 1973.2 1779.9 1304.8 1331.0 1965.0 13637.9 22784.1 19839.8 19480.2 10146.2 860:2.9
13 4637.6 2263.4 1760.4 1608.9 1257.4 1176.8 1457.4 11333.5 36017.1 23443.7 19887.1 12746.2 9832.9
14 5560.1 2508.9 1708.9 1308.9 1184.7 883.6 776.6 15299.2 20663.4 28767.4 21011.4 10800.0 9277.7
15 5187.1 1789.1 1194.7 852.0 781.6 575.2 609.2 3578.8 42841.9 20082.8 14048.2 7524.2 8262.7
16 4759.4 2368.2 1070.3 863.0 772.7 807.3 1232.4 10966.0 21213.0 23235.9 17394.1 16225.6 8451.5
17 5221.2 1565.3 1203.6 1060.4 984.7 984.7 1338.4 7094.1 25939.6 16153.5 17390.9 9214.1 7374.4
18 3269.8 1202.2 1121.6 110:2.2 1031.3 889.5 849.7 12555.5 24711.9 21987.3 26104.5 13672.9 9095.7
19 4019.0 1934.3 1704.2 1617.6 1560.4 1560.4 1576.7 12826.7 25704.0 22082.8 14147.5 7163.6 8032.2
20 3135.0 1354.9 753.9 619.2 607.5 686.0 1261.6 9313.7 1396:2.1 14843.5 7771.9 60.0 491:2.3
21 2403.1 1020.9 709.3 636.2 602.1 624.1 986.4 9536.4 14399.0 18410.1 16263.8 7224.1 6114.6
22 3768.0 2496.4 1687.4 1097.1 777.4 717.1 813.7 2857.2 27612.8 21126.4 27446.6 12188.9 8588.5
23 4979.1 2587.0 1957.4 1570.9 1491.4 1366.0 1305.4 15973.1 27429.3 19820.3 17509.5 10955.7 8963.4
24 4301.2 1977.9 1246.5 1031.5 1000.2 873.9 914.1 7287.0 23859.3 16351.1 18016.1 8099.7 7112.0
25 3056.5 1354.7 931.6 786.4 689.9 627.3 871.9 12889.0 14780.6 15971.9 13523.7 9786.2 6313.7
26 3088.8 1474.4 1276.7 1215.8 1110.3 1041.4 1211.2 11672.2 26689.2 23430.4 15126.6 13075.3 840:2.7
27 5679.1 1601.1 876.2 757.8 743.2 690.7 1059.8 8938.8 19994.0 17015.3 18393.5 5711.5 6834.8
28 2973.5 1926.7 1687.5 1348.7 1202.9 1110.8 1203.4 8569.4 3135:2.8 19707.3 16807.3 10613.1 823:2.6
29 5793.9 2645.3 1979.7 1577.9 1267.7 1256.7 1408.4 11231.5 17277.2 18385.2 13412.1 7132.6 6992.2
30 3773.9 1944.9 1312.6 1136.8 1055.4 1101.2 1317.9 12369.3 22904.8 24911.7 16670.7 9096.7 8183.7
31 6150.0 3525.0 2032.0 1470.0 1233.0 1177.0 404.0 10140.0 00.0 26740.0 18000.0 11000.0 8907.9
32 6458.0 3297.0 1385.0 1147.0 971.0 889.0 1103.0 10406.0 17017.0 27840.0 31435.0 12026.0 9580.4
MAX 6458.0 3525.0 2258.5 1779.9 1560.4 1560.4 1965.0 15973.1 42841.9 28767.4 31435.0 17205.5 9832.9
MIN 2403.1 1020.9 709.3 619.2 602.1 569.1 609.2 2857.2 13233.4 14843.5 7771.9 4260.0 491:2.3
MEAN 4513.1 205:2.4 1404.8 1157.3 978.9 89a.3 1112.6 10397.6 22912.9 20778.0 18431.4 10670.4 7985.9
)1 )]1 j J 1 J -···1 --1 ---]
TABLE F.2:PRE-PROJECT FLOW AT DEVIL CANYON (CFS)
YEAR OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP ANNUAL---
i 5756.2 2404.7 1342.5 951.3 735.7 670.0 802.2 10490 18466.6 21363.4 18820.6 7950.8 7537.8
2 3652.0 1231.2 1030.8 905.7 767.5 697.1 1504.6 13218.5 19978.5 21575.9 18530.0 19799.1 8615.9
3 5221.7 2539.0 1757.5 1483.7 943.2 828.2 878.5 4989.5 30014.2 24861.7 19647.2 13441.1 8918.0
4 7517.6 3232.6 1550.4 999.6 745.6 766.7 1531.8 17756.3 25230.7 19184.0 19207.0 13926.4 9356.4
5 5109.3 1921.3 1387.1 1224.2 929.7 729.4 1130.6 15286.0 188.1 19154.1 24061.6 11579.1 866.9
6 4830.4 2506.8 1868.0 1649.1 1275.2 1023.6 1107.4 8390.1 28081.9 26212.8 24959.6 13989.2 9707.4
7 1647.9 1788.6 1206.6 921.7 893.1 852.3 867.3 15979.0 31137.1 29212.0 2609.8 16495.8 10608.2
8 5235.3 2773.8 1986.6 1583.2 1388.9 1105.4 1109.0 12473.6 28415.4 22109.6 19389.2 18029.0 9666.7
9 7434.5 359Q.4 2904.9 1792.0 1212.2 1085.7 1437.4 11849.2 24413.5 21763.1 21219.8 6986.8 8866.8
10 4402.8 1999"8 1370.9 1316.9 1179.1 877.9 1119.9 13900.9 21537.7 23390.4 28594.4 15329.6 9649.6
11 6060.7 2622.7 2011.5 1686.2 1340.2 1112.8 1217.8 14802.9 14709.8 21739.3 22066.1 18929.9 9004.4
12 7170.9 2759.9 2436.6 2212.0 1593.6 1638.9 2405.4 16030.7 27069.3 22880.6 21164.4 12218.6 10021.3
13 5459.4 2544.1 1978.7 1796.0 1413.4 1320.3 1613.4 12141.2 40679.7 24990.6 22241.8 14767.2 10946.5
14 6307.7 2696.0 1896.0 1496.0 1387.4 958.4 810.9 17697.6 24094.1 32388.4 22720.5 11777.2 10431.8
15 5998.3 2085.4 1387.1 978.0 900.2 663.8 696.5 4046.9 47816.4 21926.0 15585.8 8840.0 9250.7
16 5744.0 2645.1 1160.8 925.3 828.8 866.9 1214.4 12267.1 24110.3 26195.7 19789.3 18234.2 9555.5
17 6496.5 1907.8 1478.8 1478.4 1278.7 1187.4 1619.1 8734.0 30446.3 18536.2 20244.6 10844.3 8697.0
18 3844.0 1457.9 1364.9 1357.9 1268.3 1089.1 1053.7 14435.5 27796.4 25081.2 30293.0 15726.2 10460.4
19 4885.3 2203.5 1929.7 1851.2 1778.7 1778.7 1791.0 14982.4 29462.1 24871.0 16090.5 8225.9 9175.4
20 3576.7 1531.8 836.3 686.6 681.8 769.6 1421.3 10429.9 14950.7 15651.2 8483.6 4795.5 5352.1
21 2866.5 1145.7 810.0 756.9 708.7 721.8 1046.6 10721.6 1711809 21142.2 18652.8 8443.5 7063.9
22 4745.2 3081.8 2074.8 1318.8 943.6 866.8 986.2 3427.9 31031.0 22941.6 30315.9 13636.0 9657.2
23 5537.0 2912.3 2312.6 2036.1 1836.4 1 59.8 1565.5 19776.8 31929.8 21716.5 18654.1 11884~2 10199.0
24 4638.6 2154.8 1387.0 1139.8 1128.6 955.0 986.7 7896.4 26392.6 17571.8 19476.1 8726.0 7736.3
25 3491.4 1462.9 997.4 842.7 745.9 689.5 949.1 15004.6 16766.7 17790.0 15257.0 11370.1 7160.5
26 3506.8 1619.4 1486.5 1408.8 1342.2 1271.9 1456.7 14036.5 30302.6 26188.0 17031.6 15154.7 9609.6
27 7003.3 1853.0 1007.9 896.8 876.2 825.2 1261.2 11305.3 22813.6 18252.6 19297.7 6463.3 7705.5
28 3552.4 2391.7 2147.5 1657.4 1469.7 1361.0 1509.8 11211.9 35606.7 21740.5 18371.2 11916.1 9436.8
29 6936.3 3210.8 2371.4 1867.9 1525"0 1480.6 1597.1 11693.4 18416.8 20079.0 15326.5 8080.4 7765.1
30 4502.3 2324.3 1549.4 1304.1 1203.6 1164.7 1402.8 13334.0 24052.4 27462.8 19106.7 10172.4 9023,0
31 6900.0 3955.0 2279.0 1649.0 1383.0 1321.0 1575.0 11377.0 26255"0 30002.0 20196.0 12342.0 9994.5
32 7246.0 3699.0 1544.0 1287.0 1089.0 997.0 1238.0 11676.0 17741.0 31236.0 35270.0 12762.0 10577.9
MAX 7517.6 3955"0 2904.9 2212.0 1836.4 1178.7 2405"4 19776.8 47816.4 32388.4 35270.0 19799.1 10946.5
MIN 2866.5 1145"7 810.0 686.6 681.8 663.8 696.5 3427.9 14709.8 15651.2 8483.6 4795.5 5352.1
MEAN 5311.8 2382.9 1652.0 1351.9 1146.9 1041.8 1281.5 12230.2 259380 4 23100.9 20709.0 12276.3 9084.4
1 )1 }-""1!l
J J )
TAUlE F .J:
]
TYPICAL NUAA CLIt,lATE DATA HECOHD
1 J
Meteorological Data For 1976
Sr,lion:5U"MlT~ALASKi.5U""IT AlA'ORT S~d time \I":AlASKAN Uilludt:.1·ZO'"lo~tud.:149·01 ...Ell'Yalion Cgrotmdl:231'....Y••r:ill'........
T.mper.lult If AI!I ••ill't Nunnr of dlyl A,Vtf.gePrecipUlliooininch••hurnidil~.p4;1.W'od
0llllfCll diV_
Rn"".".r-;;....Il .;:,;;-i Iblion
8....65 IF
-1--I i
J .~T.mper.tur,-F ","","
Aller.gn E.u.meI W.UlI equiVII.n1 Snow.11;'pllI.it II SUnriw '0 sunset H mb
I I I l.M.xlmum Minimum
Manlh --r-~'l--1 -r;----lbl Ell.....
E E
5 .E ~II~'~'l 10 ~!~..i b 8&1&~.~~.~i 1 )f r Iz I ~j H h Ii 1 !Ii I-H f Hi:I!:1 I J I!11 140'e ~§!§I §rl A 100'HH l'"Iloc.t lim"ora lu 1:11 bli m.....%"....1\..",1\...D----~.
JoN '.0 _J.I 1.6 )'10 -26 •lUI 0 1.1l 1.1'II-I''••7 21.'II-I'67 70 H H ..U 30 6.0 II •16 U 7 0 I 0 19 JI 10fr'••1 -lO.4 -1.1 II ,-n II 191'0 1.11 0.10 •1'.6 ••1 ',6 6'"61 II 07 ZI 3.'11 ••7 6 0 0 0 U Z9 HNIA11.1 Z.Z 10.Z 3D 6 -I'II 1696 0 1.61 0.41 J-''1.1 '.7 )7,67 IS 01 n '.0 ••n II •0 0 0 II II UA'.)6.',..,a.6 II 10 -)U 1110 0 o.I'0.0'U ,..).1 Z6 61 ZO O'I'6.Z ••16 )Z 0 0 0 •30 Z.IV 0\1.t.19.6 )6.',.J 17 1 11.0 Z...1.'0 •'.1 Z.6 •69 17 Z.II 7.,,6 ZO 7 6 0 0 0 0 n 0
JUN 60 0 6 40.'·SO ••14 Z7 H •AlO 0 0."O.JO JO 0.0 0.0 69 II ZZ 17 6 ••6 •16 •o •0 0
,0 0 0
JUL 61.'4:1.'52.'16 II JJ 6 16.0 1.0'O.U Zi 0.0 0.0 '1 Z9 ZI Z7 '.1 )7 ZI I'0 0 I 4 0 0 0
'UG 61.'\1.1 SZ.J 71 I II ••3n 0 0,,96 O.ZO 1 0.0 0.0 10 ZO Z6 1 II 0 ,0 I 0
SIP 69.1 )1.1 40 ••,.••16 30 11.0 I."0.69 9 0.'0.1 10 76 n n I'7.6 J •II IJ 0 0 Z 0 0 17 0
Del 20 O.IZ
VIA'
Normals.Means,And Extremes -11IROUCH 19151
,
T.mpeJ.lur.'F Norm.1 Pret-ipiUlllon In inc.he.hu:~:~v~t.Wind r .....,nt.ll1'lbM'or dly.",V1f9
--Dtgf.'dlY.i i IlIlion
NDrIJl.1 bUI"""8 ••85 "F Will"equl"'llenl $now,Ie.P!l1~'"....._••Fatal ml"~~Sunri.&a ...."",t I:II I ~'IU"M~:~,..
-~--~._~--~a a il I I j ~11 I f J . .
$1%,,1 'IRa i b lbl EIoY,~E ~E~~~~~l!'~e ii&J 1&~E ~l II j III .r l!'j-~~~c ~Ii1 ~'"02 O.14 20 I"'i ~1"I 10 ..I .~t i a 1·1 ~..iii &t &t I 1.40'
j n H J h ~I ~j §h J ~~~i ~!j ~j ~!1..../1,....1 j ~11 ~~~~Is !~Bah.b ~:I;lill:lJ ~I bA ...~:,.~---._-~-
101 II U U),U J4 II "1 6 • , 1 7 7 7 7 7 ZO • • •......J4 Z
J 1.'-4.'1.6"1941 ..1971 19U 0 O.'H 1.11 .."0.0.....0.'0 I'".....I'"16.1 I9n 61 61 61 61 U.I HE ••01 1961 '.'IJ ,II ••0 • 0 10 II ZO 'ZI.'
F U.'-..6.6"'42 .,19'1 I6U 0 I.U 4.11 "I ,1110 Z.l.lUI""lUI ZI.O 19 ..16 11 "H II.'HE 61 07 ItH 7.0 6 ,17 10 ,0 I 0 Z6 21 II '11.'
M 1'.'1.0 II.Z 69 '61 U 1971 166'0 '.06 4."966 0.07 1961 1.61 IQU 19,1 19"11.1 1'46 16 16 7.n II~'HE ..10 1911 6.Z'6 \6 10 ,0 I 0 It JI I''I7.Z
A 12.'1401 n.'n '")0 19..IZH 0 0.61 6.",..0.06 94'0.11 1163 H.1 1970 '.1 1961 .0 11 6'11 7.6 HE JJ 01 1t71 7.Z'7 II 1 •0 I 0 II 10 I 9ZZ.'
M ".1 1901 n.6 16 960 HI•.,.u 0 O.ll Z.66 "..0.04 114'0.96 1146 17 ••1951 1.'1946 II 10 ..61 1'.7 W ZI 07 1969 1.'3 •It 1 Z • I •l U ••ZJoI
J ".0 19 ••49.0 II 1961 II 19'1 no 0 Z.U 6."I'"0."I94Z Z.U 1967 ••'Ill.1.1 1914 U 11 n 61 '.1 510 Z.ZZ 1970 '.z Z 6 ZZ IZ I Z 1 )0 Z 0 91 ••7.
J OO.Z H.'".0 '1 961 II 1110 ~OJ 0 J.O',.,.9B 1.11 .."I.',194..,7 1970 ••1 1'1019 11 61 7Z 7.'5W JO ZJ 1914 '.2 Z 7 ZZ II •Z I ,0 • 0 '1901
,".0 H.I ".6 '1 96.Zo'"'0'0 I.JO 6.33 "S 0.10 IIH Z.IO 1944 ••0 IU5 6.0 1911 II .,62 16 1.6SW JI ZZ 1911 1.3 Z 6 II II 0 •1 I 0 Z 0 nO.lsUol12.6 n.'lS "7 6'"H)0 Z.II 6.1)110"0.19 196.Z.Ol 1944 21".'IU'16.0 19"II U 19 H 1~'HE U ZJ IIlZ 7.'"10 16 Z • I • I I'0 916.1
a 10.~11.'14.0 19 '6'II 1975 1111 0 1.61 3.19 IUZ O.lZ 1961 1.14 1961 H.'1970 12.6 1'70 IJ II 16 II '.0 NE IS II 1910 1.6"ZI U 7 0 Z 0 II 10 Z 916.7
H ".1 ).1 ••1 u '6Z Z.194'161'0 1.11 6."9IZ 0.06 96)I.JO 196.n.1 1961 21 ••1910 ,.19 11 "II.)HE 19 U 1970 1.1 1 4 19 • ,0 I 0 21 30 U 'ZI.l
o 9.Z -).6 Z••6Z 969 U 1961 1915 0 I.ZO ••6)1.51 0.14 19"1.0.1967 '0.7 191.n ••191D 16 11 16 n 1Z~1 NE ..II 1970 ••,.,17 II 6 0 I 0)0)1 I'116.7
UH AN ~G fI U Nay F',MAR
VR 13.0 11.0 U.'19 961 ..I'll <161 0 10.06 6.70 'U ,910 Z.19 1911 "01 1961 ZI.O 196''1 16 .,"'.7 HE ••10 1911 7.Z 68 70 zn II.41 ,IZ •171 Ul 16 911.0
NOTE:Oue to h:u thlln full ttoo operation on •variable ec::hedule.manually rt!c:ot'ded .lemenu _-.:-.
fram beaken sequt!nces 1n incomplete records ~Dilly tempencu-.-:-e extreme.and pre~lplUtlon
tOta1l5 for poctlons of the record may be for other than ..calendar day.'l1le period of 'record
for lWII,e e!emenU I,for other than cOfuec:utlve yearl.
(a)Length of record,yean,through the
current year unhu otherwise nated.
b.sed an Janulry dUt.
(b)70·and above It All1hn ,tutons.
•Lus than ont hilt.
T TriCI.
NORAAlS ~Based on record for lhe 1941·1970 pettod.
DATE OF AA EXIR[Mf ~The IIO$t r~ceflt In cues of lIIuHlple
o(.currence.
PREVAILING WI"D OIRECTlOH -Record 'hrou.h 1963 .
WiNO O1AHTION -Numell15 Indtcate t~nS of deqr~~5 clod",h~
from true north.00 Indl,.tli ulm.
FAsTEST MilE NIHil -Speed 15 fUh$l oDur"'4.d l~lIlnutl waive
when the dtrectlon 1s In tens 0'degrees,.
:~~~~h~~~:~~a~9~O~~~Sro .~363~uary 1968 to date when available
fo["full )'eet'.
ro["the ~rJod 1~42-195l and January 1968 to dete when avaUable
for full )le..-r.
Dd d '-01 thh fit_tlon not avaUable for archiving nor
.,ubl,l":d(iou of sUIlmar)l effective October 1976.
)1 1 1 j )~._.]---]---1 ~_..._]1 )
TABLE F.4:SUMMARY OF CLIMATOLOGICAL DATA
MEAN MONTHLY PRECIPITATION (Inches)
STAT ION JAN FEB MAR APR MAY JUN JULY AUG SEPT OCT NOV DEC ANNUAL
Anchorage 0.84 0.56 0.56 0.56 0.59 1.07 2.07 2.32 2.37 1.43 1.02 i.07,
Big Delta 0.36 0.27 0.33 0.31 0.94 2.20 2.49 1.92 1.23 0.56 0.41 0.42 11.44
Fairbanks 0.60 0.53 0.48 0.33 0.65 1.42 1.90 2.19 1.08 0.73 0.66 0.65 11.22
Gulkana 0.58 0.47 0.34 0.22 0.63 1.34 1.84 1.58 1.72 0.88 0.75 0.76 11.11
Matanuska Agr.
Exp.Station 0.79 0.63 0.52 0.62 0.75 1.61 2.40 2.62 2.31 1.39 0.93 0.93 15.49
McKinley Park 0.68 0.61 0.60 0.38 0.82 2.51 ~25 2.48 1.43 0.42 0.90 0.96 15.54
Summit \'ISO 0.89 1.19 0.86 0.72 0.60 2.18 2.97 ~09 2.56 1.57 1.29 I.11 19.03
Talkeetna 1.63 1.79 1.54 1.12 1.46 2.17 3.48 4.89 4.52 2.54 1.79 1.71 28.64
MEAN MONTHLY TEMPERATURES (OF)
Anchorage 11.8 17.8 230 7 35.3 46.2 54.6 57.9 55.9 48.1 34.8 21.1 130 0
Big Delta -4.9 4.3 12.3 29.4 46.3 57.1 59.4 54.8 430 6 25.2 6.9 -4.2 27.5
Fal rbanks -11.9 -2.5 9.5 28.9 47.3 5!lo 0 60.7 55.4 44.4 25.2 2.8 -10.4 25.7
Gul kana -7.3 ~9 14.5 30.2 4~8 54.2 56.9 530 2 430 6 26.8 6.1 -5.I 26.8
Matanuska Agr.
Exp.Station !lo9 17.8 230 6 36.2 46.8 54.8 57.8 55.3 47.6 330 8 20.3 12.5 34.7
McKinley Park -2.7 4.8 11.5 26.4 40.8 51.5 54.2 50.2 40.8 230 0 8.9 -0.1(25.8
Summit wsO -0.6 5.5 9.7 230 5 37.5 48.7 52.1 48.7 39.6 230 0 9.8 300 25.0
Talkeetna 9.4 15.3 20.0 32.6 44.7 55.0 57.9 54.6 46.1 32.1 17.5 9.0 32.8
TABLE F.5:RECORDED AIR TEMPERATURES AT TALKEETNA AND SUMMIT IN of
TALKEETNA SUMMIT
bally Dally Monthly Dai Iy Dai ly Monthly
Month Max.Min.Average Max.MIn.Average
Jan 19.1 -0.4 9.4 5.7 -6.8 -0.6
Feb 25.8 4.7 15.3 12.5 -1.4 5.5
Mar 32.8 7.1 20.0 18,0 1.3 9.7
Apr 44.0 21.2 32.6 32.5 14.4 23.5
May 56.1 33.2 44.7 45.6 29.3 37.5
June 65.7 44.3 55.0 52.4 39.8 48,7
Jul 67.5 48,2 57.9 60.2 43.4 52.1
Aug 64.1 45.0 54.6 56.0 41.2 48,7
"...Sept 55.6 36.6 46.1 46.9 .32.2 39.6
f
I
Oct 40.6 23.6 32.1 29.4 16.5 23.0
Nov 26.1 8,8 17.5 15.6 4.0 9.8rDec18,0 -0.1 9.0 9.2 -3.3 3.0
!
Annua I Average 32.8 25.0
r-
F'
I
I~
,.-
FIGURES
_-l
RESERVOIR AREA (1000 ACRES)
2200
2100
2000
~
I&.-
I"'"~1900
I ~I
I ~
IIJ
..J
IIJ
IIJ 1800(.)
r-ifIa::
:)
0
r'"a::
~1700
C CAPACITY·~
1600
ISOO
o
1400
o 2 4 ••10
STORAGE CAPACITY (MILLION AC.FT.)
AREA AND CAPACITY CURVES
WATANA RESERVOIR
.WITHOUT RESERVOIR SILTATION FIGURE F.I
-
RESERVOIR AREA (1000 ACRES)
1600
8 7 6 5 4 a
I~00 ~-----4------I-----+-----+-----+-----1
1400
-.,.:...-1300
Z
I""'"0I
I ~
~
..J
!AI
1200
!AI
(,)
i!
II:
::;)
en
r-ca:1100
!AI
~
C
~,.....
1000
r~
900 ,......----+-----+-----+-----f------+----"""'"
STORAGE CAPACITY (1000 AC.FT.)
AREA AND CAPACITY CURVES
DEVI L CANYON RESERVOIR
.WITHOUT RESERVOIR SILTATION FIGURE F.2
a 20 40 80 10 100 120 140 160
DISCHARGE (eFS.lOs)
480
1475 l/
~V
/V
1470 /
/
~/I1485
VI
1480 /
V
J
1455 /
I ,~
II
.N01 .-1'10..1"
~
-I
i
-WATANA TAILWATER RATING
.,....
-
-!
FIGURE F.3
875
870
<f~8&5
-~......
f""~
~8&0
%
C!)
iii-%
I
!III
(!)
C
(!)855
r-
850
v V'"
~
V ~
/V
/I'
/
/v
/
/
v
o 20 ..0 10 eo 100 120 14K)1&0 180 200
DISCHARGE [CFS I fO a )
DEVIL CANYON
TAILWATER RATING
(TAILRACE TO PORTAGE CREEK)
FIGURE F.4
-.
rr-
-
-<
~.
'"'":,;
:0-
7 ~-
-j'
/...._.
/-I
I
i
I I(~..-
.1
-
"'
I
ul I )N;~I -
I I~)-
I I I
• 0 ::r,~~~I
!!Q.
c(
~-a:
"I I I Cl
~I i£=I ,I -0>-=-I I ,::r
-'I
......~I
,,'I ~=.J !-~0..-J-IA.
~:i I ~=-I I -IA.
I ::IE:-,I I
I I Q.-'-~'<
I I ~Z
=-I I I I ~,
I
--I
1 ______
I ~
:I I -:I !:
____I ;..
.~-
-
I
I \-..
I
I
-
I ..
1 I I t r I I r t I -....CO ........~..0 0 0 8 ....0 0 ..0 ........
..0 -'"..N •..•...!!:!~~sa .............'".........
\M)MClU.•.ll4l:)31M1 0001 1 [S~:)l MO''''
-J 1 j --1 J ]]1 -})r 1
M.I 1/4 LOC~L lYENli
l
DAMPING'0.10
..
10"-HIICINTILI
/
V -........~
/,\,
MUN
V -........100...r\.
/V/'"~\.
1/.,/V "'\
.---
'P-O.Tt
Iiii 0.111 "~,
"'''''~~
~~
-•-
•..
C)
z
2
~..a
III
.J
III
Co)
Co)..
.J..a
~
Co)
III
L•
I
o
0.01 0.01 0.01 0.1 0.1 0.1 0.1
PIIIIOD (IIC)
2 3 10
MEAN RESPONSE SPECTRA AT THE DEVI L CANYON SITE FOR
SAFETY EVALUATION EARTHQUAKE
FIGUREF.5
-
APPENDIX FB
-APPENDIX FB WATANA AND DEVIL CANYON EMBANKMENT STABILITY ANALYSES
1 -Preliminary Design
1.1 -General
Stability analyses for the Watana Main Dam and the Devi 1 Canyon Saddle
Dam embankments have been conducted in sufficient detai 1 to satisfy
project feas i bi 1ity.The fo llowi ng paragraphs summari ze these eva 1ua-
tions along with the spillway fuse plug embankments for both dams.
1.2 -Watana Main Dam and Devi 1 Canyon Saddle Dam
Although only the Watana main dam maximum cross-section has been
analyzed,the safety factors also apply to the Devil Canyon Saddle Dam,
which has the same configuration but a much lower height.The embank-
ment design (cross-section and foundation treatment)is essentially the
same for both embankments (figures FB-1 and FB-2).The quoted safety
factors derived from the ±830 foot high dam are conservative for
the ±150 high saddle dam.
a.Methodology
The static analyses were performed using the STABL computer program
developed to handle general slope stability problems by adaptation of
the Modified Bishop method,and FEADAM,a finite element program for
static analysis of earth and rockfill dams,to determine the initial
stresses in the dam during normal operating conditions.
The dynamic analyses were performed using the QUAD 4 finite element
program whi ch incorporates strai n -dependent shear modu lus and dampi ng
parameters.
b.Static Analysis
Case
Loading Conditions and Factors of Safety
Required
Minimum Factor
of Safety
Calculated Factor
of Safety
U/S Slope DIS Slope
Construction 1.3
Normal Maximum Operating 1.5
Maximum Reservoir Drawdown 1.0
Maximum Reservoir Level During PMF 1.3
c.Seismic Stability Evaluation
2.0
2.0
1.8
2.0
1.7
1.7
1.7
1.7
The safety factor evaluation of the embankment seismic stability was
based on a compari son of avai 1ab le shear strength to the earthquake
FB-l
induced shear stresses.A shear stress exceedance ratio was uti lized
to represent an indication of the embankment stabi lity.This ratio is
considered to represent a factor of safety against reaching a strain
level of 5 percent for a particular element within the dam cross sec-
tion.In this type analysis,a ratio less than 1.0 indicates satis-
factory performance.Experi ence on embankments,whi ch have been sub-
jected to earthquake loading indicates that if the strain within the
dam is less than 5 percent,the earthquake had 1itt le or no effect on
the stability of the dam.Experience also indicates that the integrity
of the dam is not compromi sed if the strain exceeds 5 percent at some
locations.The effect of larger strains depends on the extent and
1ocat i on of the occurence.Local i zed shear stress exceedance adjacent
to exteri or slopes or near the crest are to be expected and do not
indicate overall dam stability problems.
During the period of earthquake shaking very little dissipation of
excess pore pressures is expected in the impervious core;therefore,
the stability should be evaluated on the basis of undrained conditions.
In the case of the shells the analysis has utilized both drained and
undrained conditions.As there should be negligible build up of pore
pressures in these high permeability granular materials,stability
should be evaluated on the basis of drained conditions.Evaluations of
the plots of the drained and undrained shear stress exceedance for a
soft and stiff core on Figures FB-4, FB-5,FB-6 and FB-7 indicate only
limited zones of shear stress exceedance adjacent to the toe of the up-
,stream shell,near the crest and in the surface layer of the downstream
shell.These are localized zones indicating the dam is safe,as the
overall stability is not affected by the seismic action.
d.Conclusions
Static and dynamic analyses confirm the stability of the upstream and
downstream s lopes of the proposed cross -secti ons of the Watana dam
shown on Figure FB-1.The analyses indicate stable slopes under all
conditions for a 2.4 horizontal to 1.0 vertical upstream slope,and a
2.0 horizontal to 1.0 vertical downstream slope.
1.3 -Spillway Fuse Plug Embankments
The emergency spi llway fuse plug embankments uti lize exterior slopes
and fi 11 materi als simi lar to the dam embankments (Figure FB-l and
FB-2).
a.Methodology
The stabi lity studies for the fuse plug embankments have been carried
out using a computer programmed Morgenstern-Price method of analysis.
The static analyses have been investigated for loading conditions simu-
lating the construction case,normal maximum operation (steady seepage)
and maximum reservoir drawdown (sudden drawdown).The seismic analysis
utilized only the latter two cases.Newmark (reference 1),Makdisi,
and Seed (reference 2)methods were used in a simplified permanent
deformation analysis.
FB-2
b.Static Analysis
Loading Conditions and Factors of Safety
Case
Construction
Normal Maximum Operation
Rapid.Reservoir Drawdown
c.Seismic Stability Evaluation
Required
Minimum Factor
of Safety
1.3
1.5
1.0
Calculated Factor
of Safety
U/S Slope
1.75
2.10
2.28
Loading Conditions and Factors of Safety
(Pseudo -Static Analysis)
Case
Normal Maximum Operation
Rapid Reservoir Drawdown
Required
Minimum Factor
of Safety
1.0
1.0
Calculated Factor
of Safety
U/S Slope
1.04
1.19
d.Simplified Permanent Deformation Analyses
Loading Conditions and Crest Settlement
Resulting From Seismic Shaking
Cond it i on
(prior to earthquake)
Steady Seepage
Rapid Drawdown
e.Conclusions
Settlement (inches)
Newmark Makdisi &Seed
8.5 3.3
2.1 1.8
The calculated factors of safety indicate slope stability under static
loading conditions.A preliminary simplified embankment response
analysis carried out using the seismic safety evaluation earthquake
(maximum credible earthquake)as base excitation,indicate the embank-
ment is safe.
The anticipated effects on the fuse plug embankment caused by the
seismic safety evaluation earthquake are modest.The estimated perman-
ent displacement of the crest could be up to a maximum of 8.5 inches.
FB-3
-
References
1.Newmark,N.M.,"Effects of Earthquakes on Dams and Embankments",
Geotechnique,Volume XV,No.2,1965.
-
2.Makdisi,
i ng Dam
Journa'l
1978.
F.I.,and Seed,H.B.,"Simplified Procedure for Estimat-
and Embankments Earthquake Induced Deformat ions ",ASCE
Geotechnical Engineering Division,Volume 104,GT 7,
FB-4
J 1 }J 1 1 11 .-1 ---1 ----1 1 ~
NORMAL MAXIMUM
OPERATING LEVEL
EL.2185
""E"'"
2.4
d~·
FILTER •
'\PROCESSED ORAVEL FILL ~·,.•r
EL.1340
~,.....-_---.,;C:;.;.R;.;;;E;.;:;STE L.2205
~'.1 L GRAVEL FILL 7
NOTE:
FOR DETAILED CROSSECT10N SEE PLATE 9
IN VOLUME 3 OF FEASIBILITY REPORT,
WATANA DAM
MAXIMUM CROSS SECTION
o 20 40
~--1IIt-----I
SCALE IN FEET FIGURE FB - 1
I 1 J }i J J J -]»-]]J ]
NORMAL MAXIMUM OPERATING
LEVEL EL.1455
CHANGE OF SLOPE.
AT EL.1400
TOP OF SOUND ROCK
EL.1472
ORIGINAL GROUND
SURFACE J
CHANGE OF SLOPE
AT EL.1400
EL.1375
_>..<.-"
'--COARSE FILTER
FINE FILTER
DEVIL CANYON
SECTION THROUGH SADDLE DAM
AT MAXIMUM HEIGHT
Y 3P 6f
SCALE IN FEET
FIGURE FE -2
1 1 -1 J 1 J 1 ···1 1 E J 1
35.0'
EL.1434
CRUSHED STONE
OR GRAVEL 3/4'TO I V2"
CRUSHED STONE
OR GRAVEL #4
TO 3;4"
2.0'THICK
CONC.LINING
EL.2201.5 WATANAA:l 'J...EL.1465.5 DEVIL CANYON
4'1 10.0'14'
ROAD BRIDGE
CRUSHED STONE
OR GRAVEL *4
TO 3/4",
DEVIL CANYON AND WATANA
TYPICAL SECTION THROUGH FUSE PLUG
o 10 20•---::-I
SCALE IN FEET FIGURE FB - 3
SYMBOL A B C 0 E F G H I .J
VALUE 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
SYMBOL K L M N 0 P 0 R S
VALUE 1.1 1.2 1.3 1.4 1.5 2.0 4.0 6D 8.0
DYNAMIC RUN SOFT CORE
DRAINED SHEAR STRESS EXCEEDANCE (TAUdeff/TAUfd)
FlliJRE FE - 4 l.J
L.----.::-__~_~~~~~
SYMBOL A B C D E F G H I J
VALUE 0.1 0.2 0.3 '0.4 0.5 0.6 0.7 0.8 0.9 1.0
SYMBJL K L M N 0 P Q R S
VALUE 1.1 1.2 1.3 1.4 1.5 2.0 4.0 6.0 8.0
......
DYNAMIC RUN SOFT CORE
UNDRAINED SHEAR STRESS EXCEEOANCE (TAU d maxI TAUc)
FIGURE FE - 5 Ii]
SYMBOL A B C D E F G H I oJ
VALUE 0.1 0.2 O.~0.4 0.!5 0.6 0.7 0.8 0.9 1.0
SYMBOL K L M N 0 P Q R S
VALUE f.I 1.2·I.~1.4 1.!5 2.0 4.0 6.0 8.0
DYNAMIC RUN STIFF CORE
DRAINED SHEAR STRESS EXCEEDANCE (TAUdeff/TAUfd)
FIGURE FB - 6 iiJ
SYMBOL
VALUE
SYMBOL
VALUE
A B C D E F G H -I J
0.1 0.2 0.3 0.4 0.15 0.6 0.7 0.8 0.9 1.0
K L M N 0 P Q R S
1.1 1.2 1.3 1.4 1.15 2.0 4 •.0 6.0 8.0
DYNAMIC RUNSTfFF CORE
UNDRAINED··SHEARSTRESScEXCEEI)ANCE (TAUdmull/TAUc)
FIGURE FB-·7
....
-
APPENDIX FC
i",
APPENDIX FC -SUMMARY OF PMF AND SPILLWAY DESIGN FLOOD ANALYSES
Introduction
The inflow PMF peaks are estimated to be 326,000 cubic feet per second
(cfs)for Watana,and 346,000 cfs (routed through Watana)and 362,000
cfs (unrouted through Watana)for Devil Canyon.The 10,000-year flood
peaks are estimated to be 156,000 cfs at Watana,and 161,000 cfs
(unrouted)and 165,000 cfs (routed)at Devi 1 Canyon.The increase in
the routed 10,000-year peak flow over the natural flood resu lted be-
cause of the synchronization of routed flood peak and peak from the in-
tervening area between the two developments.The major work tasks per-
formed to deri ve the PMF and 10,OOO-year flood peaks are summari zed
below.Figures and tables are provided to supplement the summary.
Probable Maximum Flood (PMF)
1 -Calibration of SSARR Model
In the derivation of PMF,the rainfall-runoff relationships,snowmelt
criteri a and routing of runoff excess through watershed and channel
system,were defined by1(treamflow Synthes i sand Reservoi r Regu 1ati ons
(SSARR)watershed model-.
The model was cal-ibrated by U.S.Army Corps of Engineers
for the Susitna River basin above Gold Creek, a stream gaging
located about 12 miles downstream from the Devil Canyon damsite
FC-1).
(COE)~/
station
(Figure
.-
The model determines runoff excess from average basin precipitation,
snowme It,evapotranspi rat ion,deep perco 1ati on and soi 1 moi sture re-
plenishment,and uses flow separation techniques to temporarily store
this excess as surface storage,sub-surface storage and groundwater
storage to provide time delay effect.The ~lic routing scheme is pro-
vided in the User's Manual for the Model-.Figure FC-2 provides
a schematic representation of the basic elements of the SSARR model .
.!/U.S.Army Corps of Engineers,September 1972 (revised June
1975):Program Description and User Manual for SSARR Model,
Program 724-KJ-GOOI0,Portland,Oregon.
~/U.S.Army Corps of Engineers:Interim Feasibility Report,
South Central Rainbelt Area,Alaska,Appendix I,Part 1,
Section A,1975,and Supplemental Feasibility Report,1979.
FC-1
The dra"inage area of the basin above Susitna River at Gold Creek is
about 6.160 square miles (mi 2 ).The basin was divided in 13 rela-
tively homogeneous sub-basins.Flows from these sub-basins were com-
bined and routed downstream to derive the flows at specified locations
including those where observed flood hydrographs were available.
Figure FC-3 shows a schematic layout of the sub-basins.The figure
also shows the drainage area of each sub-basin.
The COE selected the spring floods of 1964 and 1972 and the summer
floods of 1967 and 1971 for the model calibration.The calibration was
performed by compari ng daily observed and s imu 1ated flood hydrographs
at four stream gaging stations -Susitna River at Gold Creek,near
Cantwe 11 and near Dena 1i,and Mac 1aren River near Paxson (see Fi gure
FC-3).Daily precipitation or snow h'ater equivalent data observed at
Summit,Trims Camp,Paxson,Gulkana or Gracious House (see Figure FC-l
for locations)were used.The relationships between parameters in the
model and initial values of the parameters voJere estimated initially
based on hydrologic characteristics of each sub-basin.The estimated
relationships and initial values were then progressively changed until
the simulated flows were within acceptable limits of observed flows.
Table 1 shows the comparsion of observed and simulated flood peaks.
The simulated and observed hydrographs are shown on Figure FC-4 through
FC-lO.The derived relationships between the model parameters are
shown on Figures FC-ll through FC-17.
The input data and calibration procedures used by the COE were reviewed
and a few discrepancies in data input were identified.The model cali-
bration was checked by removing these discrepancies.As a result,
re 1at i onsh ips between the parameters were revi sed in two cases (see
Figures FC-ll and FC-14)using the floods of August 1967 and June 1972
and corresponding daily rainfall data.It was'realized that the
initial values of the model parameters were not very sensitive except
,for a few days at the beginning of simulation period.The calibrated
relationships between the parameters were tested for their validity by
us i ng the 1971 flood.Fi gures FC-18 through FC-26 show the s imu 1ated
and observed hydrographs.Table 2 1i sts the curve numbers of the
parametric relationships and other pertinent data used for each
sub-basin.Elevation-area relationships for the sub-basins are given
in Table 3.
2 -Probable Maximum Precipitation (PMP)
The PMP's for the basins above Watana and Devil Canyon were estimated
from the analysis of the following six historic storms by storm
maximization:
August 22~28,1955
July 28 -August 3,1958
August 19-25,1959
August 9-17,1967
August 4-10,1971
July 25-31,1980
FC-2
-
-
-
-
-
r
Table 1
COE CALIBRATION RESULTS
Comparison of Simulated and Observed Maximum Daily Discharge
Obs erved Simulated Percent
Discharge Date Discharge Date Difference
A Susitna River at Gold Creek
May 19 to June 25,1964 85,900 Jun.7 80,500 Jun.5 -6.3
July 1 to August 31,1967 76,000 Aug.15 78,800 Aug.16 +3.7-May 6 to September 30,1971 66,300 Jun.12 53,000 Jun.11 -20.1
77,700 Aug.10 74,100 Aug.12 -4.6
May 2 to September 30,1972 70,700 Ju n.17 60,800 Jun.17 -14.0-26,400 Sep.14 32,300 Sep.15 +22.4
B Susitna River nr.Cantwell
May 19 to June 25,1964 49,100 Jun.7 51,100 Jun.4 -4.1
July 1 to August 31,1967 36,400 Aug.15 36,600 Aug.16 +0.1
May 6 to September 30,1971 24,000 Jun.23 32,600 Jun.23 -35.8
36,000 Aug.9 44,000 Aug.11 +22.2
May 2 to September 30,1972 37,600 Jun.17 37,800 Jun.17 +0.5
21,000 Sep.14 22,800 Sep.15 +8.6
C Susitna River nr.Denali
May 19 to June 25,1964 16,000 Jun.7 17,200 J.un.4 -7.5
July 1 to August 31,1967 No record 16,000 Aug.16
May 6 to September 30,1971 17,600 Jun 27 17,300 Jun ..24 -1.7
33,400 Aug.10 31,500 Aug.11 -5.7
IMay 2 to September 30,1972 14,700 Jun.16 20,300 Jun.17 +38.1
5,690 Sep.13"15,300 Sep.13 +16.9
D Maclaren River nr.Paxson
May 19 to June 25,1964 6,400 Jun.7 6,230 Jun.4 -2.7
July·l to August 31,1967 7,280 Aug.14 7,290 Aug.15 0
May 6 to September 30,1971 5,520 .Jun.25 5,430 Jun.25 -1.6
8,100 ·Aug.11 7,980 Aug.12 -1.5
May 2 to September 30,1972 6,680 Jun.16 7,780 Jun.16 -16.5
3,980 Sep.13 2,950 Sep.12 -25.9
Table 2
SUB-BASIN WATERSHED CHARACTERISTICS
INPUT fOR SSARR MODEL
Sub-basin Identi fication
Number 10 20 80 180 210 220 280 330 340 380 480 580 680------------------
Drainage area,mi 2 221 694 312 477 44 232 307 48 1047 735 1045 628 345
Number of Surface
Routing Phases 4 4 4 4 3 4 4 3 8 3 4 4 4
Surface Storage Time (hI' )6 8 3 3 6 5 3 15 10 3 8 8 8
Number of Sub-Surface
Routing Phases 4 4 4 4 3 4 4 1 8 4 4 4 4
Sub-Surface Storage Time
(hI')12 20 8 8 12 20 8 0 48 8 15 15 15
Number of Baseflow Routin~
Phases 4 5 5 5 3
5 5 1 8 4 5 5 5
Basenow Storage Time,24 156 156 156 24 156 156 0 200 96 156 156 156
(hr)
Baseflow Infiltration
Index Time (hI')100 100 100 100 100 75 100 100 100 100 100 100 100
Table No.for PPT Ys.KE
(figure FC-15)5001 5001 5001 5001 5001 5001 5001 5001 5001 5001 5001 5001 5001
Table No.QGEN vs.SCA
(Figure FC-16)6004 6006 6006 6006 6004 6006 6006 6006 6006 6006 6006 6006 6006
Table No.for Month vs ET
(Figure FC-14)4009 4008 4008 4008 4009 4008 4008 4008 4008 4008 4008 4008 400B
Table No.for SMI vs ROP
(Figure FC-ll)1015 1018 1018 1018 1015 1018 1018 1022 1021 1018 1020 1020 1020
Table No.for BII vs BFP
(Figure FC-12)2017 2011 2009 2009 2017 2012 2009 2009 2009 2009 2009 2009 2009
Maximum Percent of Runoff
to Baseflow 10 10 9 9 10 10 10 9 9 10 9 9 9
Table No.for RGS vs.RS
(Figure FC-D)3009 3008 3008 3008 3009 3003 3008 300B J008 3008 3008 3008 J008
Table No.for QGEN vs
MELTR (Figure FC-17)7011 7005 7010 7010 7009 7005 7010 7010 7010 7010 7005 7005 7005
Rain Freez.Temp.(oF)35 35 35 35 35 35 35 35 35 35 35 35 35
Base Temp.for Degree -
Day (oF)32 32 32 32 32 32 32 32 32 32 32 32 32
I ~\lapse Rate (oF/lOOO ft)3.3 3.3 3.31 3.3 3.3 3.3 3.3 3.3 3.3 3.3 3.3
-
--
-I
-
.....
....
Storm Isohyetal Pattern.Precipitation pattern in the Susitna basin is
greatly affected by orography.Therefore,it was necessary to develop
isohyetal patterns for each storm to define variation in precipitation
over the basin.This was done by isopercental technique discussed
below..
The isopercental technique requires a base isohyetal pattern,usually
mean annual or mean seasonal precipitation pattern.For the purpose of
these analyses,the isohyetal pattern of July 1980 storm was used as a
base map.The July 1980 storm pattern was well-defined because the
storm was recorded at a number of gages within and in the vicinity of
the basin.
The ratios of the total storm precipitation of a given storm to the
July 1980 storm were derived and plotted at each station where data
were available for both storms.Isopercental lines were drawn based on
these ratios.The ratios on these lines were then lTIultiplied by the
July 1980 pattern to yield values to draw isohyetal map for the given
storm.The resulting isohyetal patterns are shown on Figures FC-27
through FC-32 •
Storm Maximization.The maximization factor for each storm was deter-
mined as the ratio between the maximum precipitable water and the
precipitable water available during the storm.The maximum precipi-
table water was computed using 50-year return period maximum 12-hour
persisting dewpoint temperatures.These temperatures were derived from
dewpoint temperatures recorded at Anchorage for the months of May
through September.The actual storm dewpoint temperatures were derived
by examining the temperatures prior to the storm occurrence.The
maximization factors are listed in Table 4.
FC-3
Table 3
SUB-BASIN ELEVATION-AREA RELATIONSHIP
Sub-basin 10
Elevation,ft 2800 3000 4000 5000 6000 7000 8000 9000 13,820
Percent area below 0 4.5 17.7 35.9 61,1 84.B 96.1 99.8 99.9 -.
Sub-basin 20
Elevation,ft 2440 3000 4000 5000 6000 7000 8000 9000 10,000 13,820
Percent area below 0 27.7 53.2 81.3 92.8 97.1 98.4 98.9 99.8 99.9 ...,
Sub-bas in 80
Elevation,ft 2370 3000 4000 5000 6000 6100
Percent area below 0 35.9 74.4 97.1 99.7 99.9 -Sub-basin 180
Elevation,ft 2350 3000 4000 5000 6000 6200
,
"I
Percent area below 0 35.0 82.0 96.4 96.5 99.9
Sub-basin 210 ""'ll
Elevation,ft 3150 4000 5000 6000 7000 8000 8850
Percent area below 0 10.9 24.1 67.2 96.0 99.8 99.9
Sub-basin 220 .,
Elevation,ft 2860 3000 4000 5000 6000 7000 BODO 8850
Percent area below 0 8.2 50.5 80.1 94.9 98.6 99.8 99.9
Sub-basin 280 -Elevation,ft 2350 3000 4000 5000 5275
Percent area below 0 49.8 96.7 96.8 99.9
Sub-basin 330
Elevation,ft 2361 2363
Percent area below 0 99.9
Sub-basin 340
Elevation,ft 2100 3000 4000 5000 5275
Percent area below 0 68.7 95.2 99.8 99.9
Sub-bas in 380
Elevation,ft 1910 2000 3000 4000 5000 6000 7000 7770
Percent area below 0 2.0 15.6 49.1 78.4 96.0 99.8 99.9
Sub-basin 480
Elevation,ft 1450 2000 3000 4000 5000 6000 7000 7200
Percent area below 0 3.0 27.7 68.3 91.1 98.9 99.B 99.9
Sub-basin 580
Elevation,fE 910 1000 2000 3000 4000 5000 6000 6910
Percent area below 0 2.0 8.4 44.1 79.5 96.2 99.8 99.9
Sub-basin 680
Elevation,ft 677 1000 2000 3000 4000 5000 6000 60lB
Percent area below 0 3.2 26.1 51.0 80.9 97.1 99.8 99.9 -
-
TABLE 4
I~AXIMIZATION FACTORS
Storm Dewpoint Max.Dewpoint
at 1,000 mb at 1,000 mb
Precip.Precip.
Storm Temp.Water Temp.Water
(OF)(mm)(OF)(inch)
August 1955 47 18.3 59.5 34.1
Ju ly-August 1958 50 21.0 60.0 35.2
August 1959 48 18.9 59.5 34.1
August 1967 46 17.6 60.0 35.2
August 1971 49 19.9 60.0 35.2
Max.
Factor
1.86
1.66
1.80
2.00
1.77
r~
-I
PMP.Average percipitation over the basin above Watana was computed
uSlng the isohyetal pattern developed for six storms (Figure FC-27
through FC-32).These preci pitati on amounts were mu lti p 1i ed by the
maximization factors resulting in maximized total precipitation given
in Tab 1e 5.
TABLE 5
MAXIMIZED PRECIPITATION
Storm
August 1955
July-August 1958
August 1959
August 1967
August 1971
Maximized Total
Preci pitati on
7.03
4.96
6.82
12.54
9.04
The August 1967 storm resulted in the largest maximized precipitation
amount if it were to occur also in August.However,snowmelts in
August would be negligible compared to those in late spring and early
summer.Therefore,the storm was assumed to occur in June wi th a lower
maximization factor,est"imated to be 1.4.This provided an average
basin PMP of 8.7 inches above Watana site.The PMP for the basin above
Devil Canyon was computed by adding the sub-basin between the two sites
to 8.8 inches.
Temporal Precipitation Pattern.The August 1967 storm has a duration
of 10 days.Dai ly di stri buti on of bas in average preci pi tati on was
computed using dai ly storm precipitation observed at stations within
and surrounding the basin.This distribution was used for PMP.
The daily precipitation amounts were arranged sequentially so that
critical flood conditions are produced at the dam sites.This was done
FC-4
by assuming that the largest 24-hour precipitation occurs on the eighth
day of the PMP storm.The second 1 argest occurs on the seventh and
third largest on the ninth day.The entire pattern is shown in
Table 6.
TABLE 6
TEMPORAL PATTERN OF PMP
Daily Precipitation Ranking 11
11 111"is largest and "10 11 is smallest.
Storm Duration
10 9 8 7 6 4 2 1 3 5
-
Daily precipitation was further distributed into 50 percent 20 percent.
15 percent and 15 percent values for each respective 6-hour period.
The 6-hour precipitation was distributed in ascending order for each
day up to the ninth day.while the ninth and tenth day's 6-hourly
precipitation was distributed in descending order.Table 7 gives the
6-hourly distribution pattern for the PMP over the drainage basin above
l..Iatana.
3 -Snowmelt Criteria
An analysis of major historical floods indicated that snowmelt contri-
butes a major part of the floods.Therefore.to insure adequate
snowmelt contribution to the PMF.it was assumed that the snowpack is
unlimited for glacial sub-basins (10 and 210).The snowpack for other
sub-basins was estimated to be large enough to ensure a substantial
residual snowpack during the storm period.The estimates were based on
maximum recorded data at stations in and around the Susitna basin.
Table 8 gives the estimated initial snowpack for each sub-basin.
FC-5
,~
Day Hour PMP
(inch)
TABLE 7
6-HOURLY DISTRIBUTION PATTERN
Day Hour PMP
(inch)
Day Hour PMP
(inch)
7 6 .19
12 .19
18 .26
24 .65
8 6 .32
12 .32
18 .43
24 1.08
1 6
12
18
24
2 6
12
18
24
3 6
12
18
24
4 6
12
18
24
.00
.00
.01
.01
.04
.04
.04
.05
.13
.13
.13
.13
.10
.10
.15
.35
5 6
12
18
24
6 6
12
18
24
.12
.12
.16
.40
.16
.16
.21
.54
9
10
6
12
18
24
6
12
18
24
.59
.24
.17
.17
.40
.17
.12
.12
,fDIlU.
TABLE 8
INITIAL SNOWPACK FOR PMF
Sub-basin
10
20
80
180
210
220
280
Snowpack
(in.)
99
81
35
32
99
62
30
Sub-basin
330
340
380
480
580
680
Snowpack
(in.)
33
27
59
57
48
48
The temperature sequences prior to,during,and after PMP are shown on
Figure FC-33.Temperature through May are assumed at 32°F to ensure
the snowpack is ripening but yielding little or no snowmelt runoff;
following th'at,a sudden increase in temperature is assumed.This
temperature gradient is based on maximum one to seven day temperature
rises observed for the period of records at Anchorage and Talkeetna.
Durill9 the PI"1P storm,the temperatures are lowered.After the most
significant precipitation has fallen,temperatures are increased
again.
FC-6
4 -Occurrence of Snowmelt and PMP Storm
The snowmelt starts on June 3 based on the adapted temperature se-
quences (Figure FC-33).The PMP storm is assumed to occur between
June 8 and 17.This provides a 5-day period between start of PMP and
start of snowmelt.This time interval was considered adequate for com-
bination of.floods resulting from PMP and snowmelt.
5 -Antecedent Conditions
The amount of soil moisture present at the on-set of PMP and snowmelt
significantly controlled the amount of water available for runoff
including its distribution as surface,subsurface,and baseflow com-
ponents.Relatively moist soil conditions were assumed for each
sub-basin.Table 9 gives the initial values used for the model para-
meters.
6 -PMF
The calibrated relationships of the model parameters shown in Fig-
ures FC-11 through FC-17 and the initial values of parameters shown in
Table 9 were used to derive the PMF hydrographs at the dam sites.The
resulting inflow peaks are 326,000 cfs for Watana site and 362,000 cfs
for Devi1 Canyon site (without Watana).Figures FC-34 and FC-35 show
the inflow hydrographs at the two sites.
TABLE 9
IN IT IAL VALUES OF SSARR MODEL PARAMETERS
Baseflow Runoff
Sub-Soil Infl itration Sub-Base-
bas in Moisture Index Surface Surface flow
(in)(i n/day)(cfs)(cfs)(cfs)
10 8 .03 10·30 60
20 4 .03 10 50 60
80 4 .03 5 10 70
180 4 .03 7 10 108
210 8 .03 10 10 10
220 4 .03 10 10 60
280 4 .03 4 10 70
330 4 .03 18 0 0
340 4 .03 18 20 120
380 4 .03 8 20 130
480 4 .03 16 30 420
580 4 .03 5 10 260
680 4 .03 4 10 140
FC-7
-
7 -Design Floods
The main spillway of Watana and Devil Canyon developments are designed
to safely pass floods of lO~OOO-year return period.The estimated
flood peaks for lO~OOO-year flood are 156~000 cfs and 165,000 cfs,
respectively.Figures FC-34 and FC-35 also show the design flood hy-
drographs.In case of Devil Canyon development,the inflow hydrograph
is composed of flood outflow from Watana and the natural flood flows
from the intervening area between Watana and Devil Canyon.This is
based on the assumption that Watana dam will be constructed first.
The flood hydrographs were derived using 10~000-year flood peak (annual
series)and 1-,3-,7-~15-and 30-day flood volumes.The flood peak
and volumes frequency curves were developed for the Susitna River at
Gold Creek and transposed to the dam sites.The procedures used to
develop the frequency curves and tr~?sposition factors are discussed in
a report by R &M Consultants,Inc.-•
l/R &M Consultants,Inc.,December 1981.Regional Flood Study
Task 3,Hydro logy,prepared for Acres Ameri can Incorporated Anchor-
age,A1ask a.
FC-8
-
-
MCKINLEY
C PARK
OSUMMIT
TALKEETNAo
LEGEND
•STREAM GAGING STATION
o PERCIPITATION STATION
•DAM SITE
_.'-RIVER
---WATERSHED DIVIDE
SUSITNA RIVER BASIN
ABOVE GOLD CREEK
FIGURE FC-I
o
CLEAR WATER
TRIMS CAMPo
PAXSONo
GULKANAo
-ill
-
FIGURE FC-2
-II
-
-
-
~
Z
i=
::::)o
al:
TEMPERATUR
EVAPOTRANSPIRATION
C)
Z
i=
::::)o
al:
STREAMFLOW
SSARR WATERSHED MODEL
11 r 1 J 1 J 1 -1 1 1 -],1 1 »]i ]
c:=J flOUTING REACH
o BASIN OR SUB BASIN
o COLLECTION POINT
L:::.RESERVOIR
illQ!..Q
MACLAREN R.HR.PAXSON
NON ·GLACIAL
232 SO.III.
MACLAREN R.LOCAL ABOVE
SUSITNA CONFLUENCE
307 50.1.41.
...-.../,
I 2912 \MACLAREN R.NR.PAXSON-I I OBSERVED
'-I-'"
330
SUSITNA R.NR.DENALI
NON·GLACIAL
694 50.1.41.
/"'-',SUSITNA R.
....2910 )OBSERVED
'....._...&1
5U51TNA R.NR.DENALI
GLACIAL
221 SO 1.41.
OSHETNA
LOCAL
735 SO.MI.
_.........\.qOO
,,-\-{2915 r-
\J,_/
SUSITNA R.NR.CANTWELL
OBSERVED
4140 SO.MI.
WATANA AND DEADMAN CREEK
LOCAL
1045 SO.FT.
TSUSENA AND DEVIL CREEK
LOCAL
52B SO.III.
~2~
"\
'v-...
I \
I 2920 )
\......_/
SUSITNA RIVER AT GOLD CREEK
OBSERVED
6160 SO.III.
PORTAGE AND GOLD CREEK
LOCAL
345 50.111.
SUSITNA R.AT GOLD CREEK
CALCULATED
TYONE RIVER BASIN
1047 50.1.41.LAKE LOUISE AND SUSITNA LAKE
48 50.111.
REFERENCE'
U.S.ARIIY CORPS OF ENGINEERS INTERIII FEASIBILITY
REPORT.1175 APPENDIX I PART I
SCHEMATIC DIAGRAM OF SSARR COMPUTER MODEL
FIGURE FC-3 •i ~111
-.
.--.
j )1 1 -1 J 1 -1 I 1 I )
PAECIPITATlON
~IHettU
o
.~!:.;~
,;j;
'.'4·
...!
I,.!..
.,.!-
-......".,"-twINcrs
10 100,000
70 '0.000
ao 10.000
SO 70,000
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U.S ARMY CORPS OF ENGINEERS INTERIM FEASIBILITY
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US.ARMY CORPS OF ENGINEERS INTERIM FEASIBILITY
REPORT,197~APPENDIX I PART.I
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U S ARMY CORPS OF ENGINEERS INTERIM FEAS'BILITY
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U,S,ARMY CORPS OF ENGINEERS INTERIM FEASIBILITY
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US ARMY CORPS OF ENGINEERS INTERIM FEASIBILITY
REPORT,197~APPENDIX I PART I HYDROGRAPH SUSITNA RIVER NEAR DENALI,1972
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U.S.ARMY CORPS OF ENGINEERS INTERIM FEASIBILITY HYDROGRAPH;MACLAREN RIVER NEAR PAXSON 1964 1971
REPORT,197~APPENDIX I PART I • •
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REFERENCE HYus.ARt,lY CORPS OF ENGINEERS INTERIt,l FEASIBILllY DROGRAPH MACLAR EN RIVER NEAR PAXSON.1967,1972
REPORT.1975 APPENDIX I PART I
FIGURE FC-llJill~UU
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SOIL MOISTURE INDEX SMI (INS)
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BU-BASEFLOW INFILTRATION INDEX (INS/DAY)
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ACCUMULATED GENERATED RUNOFF
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TOTAL SEASONAL ACCUMULATED RUNOFF -QGEN t%}
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FIGURE Fe -17
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~SSARR MODEL CALIBRATION
SUSITNA RIVER AT GOLD CREEK 1967 FLOOD
~~~~(rFIGUREFe-18DATE
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DRAWN BV
DESIGNEDBV
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AUGUST
1064
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3129Z7
OBSERVED FLOW
211917
/~_...CALCULATED FLO
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....----"",-"f'...........;~",........,....
13 I!I
JULV
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DATE
CXoSIGNED BV
DRAWN BV
CH£O<ED8V
S SARR MODEL CALI BRATION
SUSITNA RIVER NEAR CANTWELL 1967 FLOOD
FIGURE Fe -19 :i~~f~i
,j ~I~
J J i 1 0)'I 1 -1 ]l J )1 1 -1
2
i!4ZZZD18
!
I
,08SERVED FLOW
I
IZ 14 16
AUGUST
10864ZZ7Z931
TIME IDAY)
DATE
Z~Z3ZI1913I~17
JULY
iI"'----...-
II97~
I
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8
~.6
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~,4
0
~
2
0
I 3
DESIGNED BY
DRAWN 8Y
CHECKED BY
SSA RR MODEL CALIBRATION
MACLAREN RIVER NEAR PAXSON 1967 FLOOD FIGURE Fe -20 l~~~f~!
.•!ll
)-J .,----
J ))1 1 '-'1 ))!I 1
:1''fI'I "1
1
'I I I ..I I'·I
FLOW
I,
I
I
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I
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........",-~
OBSERVED FLOW
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\ I "·1 I I \;'\;:/CALCULA1TED
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r •",~-',
I \•
I '
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60
M
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40
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~40.
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~3~•a
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30
2~
20
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10
~
SSARR MODEL CALIBRATION
SUSITNA RIVER AT GOLD CREEK 1972 FLOOD
•<I
DESIGHl:C IV
CIlAWN IY
OE:llUlIY
II .10 I~20
MAY
2~301 ~10 I~
JUNE
DATE
20 2~30 5 10 I~20
JUL1
2~30
FIGURE Fe -21 !~~~l~,J
"II
I ]1 --]--1 --)I 1 I 1 )J
,jJ
[)(s1GNEO fJ(
DRAWNfJ(
ct*:CK£Olv
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4~40
0
~.
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~
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0
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10
5
SSARR MODEL CALIBRATION
SUSITNA RIVER NEAR CANTWELL 1972 FLOOD
FIGURE Fe -22 ~~
1".1
1 1
r---------,
1 --1 'T 1 -1 j J J 1 1
:I''I"T'I I'I "I I'I I
oeSERVED FLOW
10
,
8
1
g 6
~.
VI 5...
~
~4...
3
2
'I
0
5 10 15 20 25 301 5 10 15
MAY JUNE
DATE
25 30
"\,,~CALCULATEO FLOW
I -"'''\
I \
I A.."I /'~~I
15 20
JULY
25 30
(L5IONf:O Wi
DIl,loWI;IV
CW£ClCfO n
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SSARR MODEL CALIBRATION
MACLAREN RIVER NEAR PAXSON 1972 FLOOD
FIGURE Fe -23
1'.1
]~-]-1 ]j )~J ))1 1 ',
1 I )]
. I 'I'~I I ~~:I I " •"F I "nj ~.,_.~
1"11'
FC-24 [~~
r'
SSARR MODEL VERIFICATION
SUSITNA RIVER AT GOLD CREEK 1971
i \II I
I I
I I :
I I I
I I !
, I
I ,,\
I !,I I IiII~,------~
I \~I
I \III I
I I ( I IIII
I f I I,\\I I I \--"CALCULATED FLOW
I I I I
,I I I \I II.A ..!I \
85
80
75
10
65
60
55
50
~45
~
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l.l-40
~
9...
35
30
25
20
15
I
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FIGURE FC-25 il~~~n:
302~
·--~---I
10 15 20
AUGUST
~30 I
T-
2~I~20
JULY
10~
DATE
302~20
SSARR MODEL VERIFICATION
SUSITNA RIVER NEAR CANTWELL 1971 FLOOD
10 I~
JUtlE
~3012~I~20
MAY
10
, H IIII,.~.._,,~""""I I \,,,,"CO"""0'I\~I I ~
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DRAWN IlY
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9
30 I251520
AUGUST
1052!lI!>20
JU~Y
10530
8
3
2
1
obi ~--('6 10 ,_____I I I I III1 I I I I I II I I 1I I I I I
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og 6
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OCSlGNEll oY
DAAWN BY
CIfj;KEQ BY
j,l,
DATE
SSARR MODEL VERIFICATION
MACLAREN RIVER NEAR PAXSON 1971 FLOOD
~----.
FIGURE Fe -26IJ~~[~J
I'~'
r'
-1 1 ]]J 1 J J 1 1 J ])j
@
\/;~,
~
..TALKEETNA
a4~
L[G[ND,
•PRfCIPITATlON LOCATION AND AMOV"l liN.I
Z~
_5 -IIOtIftT
•''1.
/'"-/----
(
.-J"'/
ISOHYETAL MAP STORM OF AUGUST 22-28,1955
TRIMS
•CAMP
•PAKSON
•GULKANA
Z46
FIGURE Fe -27 i~~~[~1
L ...~
1
1
-.'
,._--
I ~J .'~-J '-1 ~--J "--J ~l '--1 J ~1 }])J j J]
@
i
I
C~ULlTN"...-/
•RiVER 1'/LODGE ~
\"
•TALKEETNA
2.~1
~,
•PllECIPlTATIQN LOCATION 'AND AIoIOUNT UN IZ,~I '
-3_ISOHY£J
-I,
ISOHYETAL MAP STORM OF JULY 28 -AUGUST 3,1958
2,-
•PAXSON
•GULKANA
o.9~
FIGURE Fe -2_
L_
1'"11
..----..,.-.-
1'-)'1
------,,.----.
J'->1 .J 1 J 1 1 1 »J ]
@
e SUMMIT
L41
r,
CHULITNA ,-/
L~~~i~R,\~/
GOLD
CREEk
\""".....
/6
~
3eW PRECIPITATION LOCATION AND AMOUNT(IN)
_3-,ISOtfY[T
.~I'
----I
ISOHYETAL MAP SlORM OF AUGUST 19-25,1959
e PAXSON
e GULKANA
076
FIGURE FC-29 fi~-~m
Ir~J
~-.,
1 J •]'-J .1 I j 1 1 ]--J 1
@
i,
CHULITNA,,...1
RIVER.".I
LODGE ~'
t
________/1
•GULKANA
.34
,t·l·
~~~I PAECIPfTATlON LOCATION AND AMOUNT liN!FIGURE FC-30 I A~O[Q I
1-'-ISOHYn ISOHYETALMAPSTORM OF AUGUST 9-11,1967 LftUnJLI
dlt
1 )
@
).]J J 1 1 1
•GULKANA
0.47
1 --1
~:
4.~O PIlEClPlTATIQIl UXATIOH AND AMOUrrr 1II~1
-a-19OIft'lT
•i,l,
ISOHYETAL MAP STORM OF AUGUST 4 -10,1971
FIGURE Fe -31
,~~~[~
dJ
]1 -1 l'--I -1 J I i 1 1 --1 'i ]l ----1
ISOHYETAL MAP STORM OF JULY 25-31,1980
•.1
@
/
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~,
e PRECIPITATION LOCATION AND AMOUNT liN.)
l.41_3-ISOHYET
elSUMMIT
~
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",-.f
)'r
r-/---
(
-..J\.,l
.0
FIGURE Fe -32 •~.....--'
11.1
1 ---1 ---].-._]1 --1 ----,1 ]1 --j __J 1
35
----..<-.----------- -- -- --- -
30
25
PMP AND TEMPERATURE SEQUENCE
FIGURE Fe -33 ~3025201015
JUNE
301 5
DATE
251520
MAY
105
20 '!I,!!1 !!I !!!!
DRAWN BY
CHECKED BY
O£SIGNED BY
lIS5025IS20
TIME (DAYS)
10
PROBABLE MAXIMUM FLOOD
)
-----
.-.---,......_-1\\/OUTFLCM'
I ILl 1\NFLOW,I
!\;i;-'
r\
Ip'\"EMERGENCY SPILLWAY \I OPERATING \
~\
I \"-t-t r\I.\I
!r·····-·-·
I II
II/~~~A~7.'sLWAY
~POWERHOUJE AND OUTLET
.......J ~~~~~IE:"~~I~~\~~~~~:~---
0 II 10 15 20 2S 30 lIS
TIME (DAYS)
PROBABLE MAXIMUM FLOOD
....
.~
I--EME1GENCY JPIL~
-OPERATING \
I \
I \
\
I \j
f'~\
I
\...MAIN SPILLWAY,OUTLET FACILITIES,
8 .POWERHOUSE OPERATING
i
J !
I---'v i
i\-OUTLET FACILITIES
AT FULL CAPACITY
2202
120
40
280
21BI
360
2184 o
2200
2196
240
320
21BB
2196
BO
~160
..
"-
"200~
~
~2194;:
~
..2/92
E
~I 2190
lIS
3530
3029iii20
TIME (DAYS)
1-10,000 YEAR FLOOD
10 IS 20 2S
TIME (DAYS)
1'/0,000 YEAR FLOOD
10
)
A,
I ~'-OUTFLON
I ~
J \
/~INFLOW
V'-rTFLOW M"TCH~I:'-I,FLOW t-
lM'iDW~1
~:,,"".m~_I"_____-'OPERATING
POWERHOUSE AND
OUTLET FACILITIES AT
,FULL CAPACITY I
I POWERHOUSE ANDIOUTLETFACILITIES yERATIN,
(MATCHING INFLOW)
I:
~
.--L MAX.WSFL 2193-
II----INFLOW EXCbrolNG
OUTflllW CAPACITY
/-\MAIN SPILLWlv OPERJING
(MATCHING INFLOW)
/
V
~rUTLET FACILITIES ATFULLCAPACITY
POWERHOUSE AND OUTLET FACILITIES OPERATING
(MATCHING INFLON)
2200
120
21B4 o
2188
160
140
20
40
60
2202
2186
2198
160
.....
u 100
~
~80
..:.2/96;;
~
;:2194
~
~
..2192
§
Xl 2190
lIS
393D
302!liii20
TIME (DAYS)
I-50 YEAR FLOOD
(SUMMER)
10 15 20 25
TIME (O"YS)
.'50 YEAR FLOOD
(SUMMER)
10
~.WSEL-2193.0
1/,,!
I \
f\
/\
I~DUTlET F..CILITIES
1/'\f'POWER:::~L~::P~~T::TFACILITlES
OPERATING (M ..TCHING INFLOW)
/\
\
'...-INFLON
i\
/-~L ______w.rtL~~
Vl OUTLET FlICILITIES "'"AT FULL CAPACITY
V '\:.POWERHDUSE AND
DUTLET FACILITIES -OPEj"TINGI(MATYHING INFr)I___J
40
30
50
10
60
70
BO
2184 o
20
90
2168
2188
2190
2194
2\92
2196
2200
2198
2202
WATANA
I .HYDROLOGICAL DATA -SHEET I FIGURE Fe -34
!-I~~,RbERVOIJ
INFlOW I OUTFlOW
!~"\~
~V OUTFlOW
INFLOW-~
t EMERGENCY
SPIllWAY
OPENING'-...POWERHOUSE
ClOSED
.rClUTFlOW
MATCHING
TlOW
).r~~I),~~~~,e:ie ~
-J V rRATnlj
POWERHOUSE
302llIII1520
TIME IDAYS!
RESERVOIR ROUTING
I-SO YR.SUMMER FUlOlI
/INFLO -oUTFl
1/N~
I
V r'-.-.POWERHOUSE AND
OUTLET FACiliTIES
OPERATING
I
oo
10
3D
40
50
20~
s
~
l!530251520
TIMElOAYS)
10
r-..
I 1
II ,
INFl W.OUTFlOWY
1\
/'""'['..f .."r--.
_f;-I
:'--MAIN iPlllWAY jERATlj
I I"fOWERHOUSE AND
.OUTlET FActLiTtS
OPERAl'NG
60
40
80
120
180
leO
100
140
0
0
20
3530251520
TIME lOAYS)
10
240
320
80
40
280
360
120
~160
it
s
g 200
o
;(
30III152025
TI\I!E lDAYS)
RESERVOIR ROUTING
I-SO YR.SUMMER FLOOD
I
lr POWER~OUSE AJO
/g~:~il::ClLtT1ESr
'(MAJ.WSEL-I458
1452
1460
1454
1450 o
g 1458
I!1456
iil
I
35302515'20
tIME (DAYS)
RESERVOiR ROUTING
1'10.000 YR.FlOOO
10
I
lir'WELoUSE,t luTLET FlclLiTIES NO
MAIN SPILlW rr OPERATING
!'--MAX.JSEL'1455
1452
1450 o
~1458
~
1458
1460
j::
!!>
~1454
~
I
3530251520
TIME (DAYS)
10
PROBABLE MAXIMUM FLOOD
I I RESE~OIR
ELEVATION
I
MAX.WSEl .r~~~.:t.CY-jut;OPERATING
"1..1 £r\oI\POWE~HOUSE~'lNG II'\'"0 \
0
1\~
0
I
1480
1460
1450
1410
1470
1420
1400
.;:
~1440
~.!1430
PROBABLE MAXIMUM FLOOD RESERVOIR ROUTING
I-10,000 YR.FLOOD
DEVI L CANYON
HYDROLOGICAL DATA -SHEET FIGURE Fe -35