HomeMy WebLinkAboutEvans Island A Proposal 1987.NEW
002
Alaska Energy Authority
LIBRAI.Y COPY
Evans Island
Hydroelectric Study.e
A Proposal
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Evans Island Hydroelectric Study: A Proposal
Mt. Energy was invited to visit Evans Island during September of
1987 to evaluate possible hydroelectric developments on the
Island. Prior to the visit various documents were supplied
pertaining to potential hydroelectric development, included in
the appendix of this proposal, which suggested that some
attention had been given to the concept but that very little hard
data was available to reach a reasonable, informed decision about
future development. This report and proposal will, hopefully, lay
the foundation for a study which would answer the primary
questions involved in hydroelectric development: how much power
is realistically available and how much will it actually cost to
produce the power?
These questions cannot be answered by consulting topographical
maps, attempting to evaluate "comparable" drainages, or
estimating costs based on formulas not specific to the sites in
question. Studies of this sort have value but will consistently
mislead the research and bring any conclusions into serious
question. It is the opinion of Mt. Energy that only by examining
the drainages potentially suitable for hydroelectric development
in detail, on the ground, using suitable hydrologic data, can an
informed development decision be made. This is no easy task, nor
should such a study be undertaken without proper consideration of
cost versus potential results. A study is always a risk: one may
end up with results one does not want or like. On the other hand,
relying on overly conservative evaluations based on little or no
field data can skew decisions very much the wrong way and kill
viable projects before they can be properly evaluated.
The decision to undertake a feasibility study on Evans Island
should rest on several factors: studies and data currently
available, analysis of topographical data, field observations,
consideration of current and proposed hydroelectric facilities,
the potential need for power and the potential benefits of
hydroelectric power. Some of these issues require subjective
analysis and will involve an informed "guess". However, the sum
total of answers to these questions will give substantive
direction to those who must decide whether to study or not.
Evans Island Hydroelectric Study: A Proposal -2-
It is the opinion of Mt. Energy that Evans Island has significant
potential for hydroelectric development and that this power can
be placed on line at a cost which will enable residents and
businesses to discontinue reliance on diesel power. Furthermore,
a study, as outlined below, can be expected to produce results
which will support hydroelectric development.
Current Available Data and Topographical Information:
Evans Island has an annual rainfall of approximately 160 inches
per year (Corps of Engineers, see appendix). It also has a fairly
precipitous range of mountains running lengthwise down the middle
of the island. By consulting topographic maps of the island, it
is apparent that at least 6 watercourses (excluding those already
developed by New Chenega Village for potable water or the
hydroelectric facility presently serving the San Juan Hatchery)
merit reconnaissance study with a strong probability that three
will warrant feasibility study.
At present there are no available detailed hydrologic studies of
any drainage on Evans Island. There are projections of waters
potentially available for diversion to hydroelectric generation
prepared by the Corps of Engineers (see appendix) for one
drainage, in Section 22, which predict sufficient flows for hydro
development. While the Corps study identifies four other
drainages worthy of note on Evans Island, they did not publish
flow projections for them. The methodology employed in the Corps
report included no field data collection or site-specific project
budgeting, thereby diminishing the usefulness of their
conclusions. The estimate in the Corps report for construction of
the Sec. 22 site (#5) appears considerably off the mark after
field observation of the Island.
The Public Health Service generated a projected hydrograph for
Anderson Creek at its mouth, the creek which supplies New Chenega
Village with water (see appendix). A yearly average flow past the
diversion dam on Anderson Creek was developed by Shannon &
Wilson, Inc., consulting engineers for the State of Alaska Dam
Safety Program (see appendix), but the methodology employed in
developing the projection was not discussed in their report.
All the above noted data suggest flows are available for
hydroelectric development in the drainages observed. None of the
data is conclusive nor sufficient for determining the feasibility
of extensive hydroelectric development. However, the data
strongly supports studying the watercourses on Evans Island,
since preliminary evidence is positive for hydroelectric
development wherever it has been sought. There is little more
that one could ask for at this stage of study.
Evans Island Hydroelectric Study: A Proposal -3-
Field Observations:
Topographically speaking, Evans Island is in the highest possible
category for potential hydroelectric development. With mountains
rising to approximately 1500 feet stretching nearly the entire
length of the Island and enjoying 160 inches of rainfall per
year, it would be very surprising if there were not several good
possibilities for hydroelectric facilities. The-r5sue appears to
be not whether power is available, but where,how much, and when.
During the visit to Evans Island by Mt. Energy, it was possible
to see the basic layout of the Island, a couple of typical
drainages in the Sawmill Bay area, and the rock types, foliage,
and wildlife patterns of these drainages. A very notable fact is
the steepness of the mountains and the proliferation of drainages
coming off them. From the coastal area near New Chenega Village,
it was possible to see extremely steep cascading streams
"falling" off the mountains. Needless to say, this gladdens the
heart of a hydroelectric developer.
There is an extremely viable and large anadromous fishery which
extensively utilizes the lower gradient areas of the creeks in
question. There is no doubt that any proposed hydroelectric
project will be required to accommodate the fish and guarantee no
impact on their spawning, rearing, or passage within the creek.
The nature of Evans Island --steep mountains draining quickly
into the Ocean fairly well precludes the possibility of
negative impacts by hydroelectric facilities. They will likely
be sited well above spawning areas because of their basic run-of-
river design, which involves steep stream gradients that preclude
use by anadromous fish. Quite clearly, extensive environmental
evaluation will be required prior to selecting a hydroelectric
development plan for the Island.
Current and Proposed Hydroelectric Facilities:
At present the San Juan Hatchery, located at the southern end of
Sawmill Bay 2.5 miles from New Chenega Village, is powered, at
least in part, by an existing 60kw hydroelectric facility. There
is good reason to assume production records will be available for
the proposed study from this facility. All that is presently
known about this plant is that it is operational and running at
the capacity of the stream. Even this data has not been
confirmed. Of course, a detailed report on this facility and its
operation will be part of the feasibility study proposed herein.
A second hydroelectric facility,
retrofit to the water system
30kw, is
presently
being
used
proposed as a
by New Chenega
Evans Island Hydroelectric Study: A Proposal -4-
Village. At this time, no decision has been made regarding
placement of the retrofit facility.
Needs and Benefits of Potential Hydroelectric Development:
At present New Chenega Village is dependent on diesel powered
electrical generation costing approximately $.50 per kilowatt
hour (KWH). At this rate, growth of the Village and its economic
base can be expected to be greatly inhibited. Discussions with
the Village IRA council members and the North Pacific Rim
Association, which serves villages in the area, strongly suggest
that they view costly electricity as a major impediment to
growth. Economic planning for the Village includes expanded
Village services and support facilities for the fishing fleet
operating in the area. These goals are energy dependent and will
be impacted greatly by hydroelectric development, or the lack of
it.
Assuming normal costs of development, hydroelectric power will be
delivered at a rate between approximately $.02 to $.05 per kwh to
residents of Evans Island. These costs are projections and could
change depending on results of the proposed study. More than
likely, transmission line expense will determine overall kwh cost
of delivery. Should cost per kwh fall in the above range, as
expected, benefits of hydroelectric development are obvious. A
secondary benefit could be the sale of electrical power to the
San Juan hatchery facility, which has been reported to want more
power for expansion.
Feasibility Study Methodology:
The methodology proposed to study Evans Island for potential
hydroelectric development will include three phases:
reconnaissance, detailed hydrological and environmental studies
of selected sites, and analysis of data collected. At the
conclusion of the study a complete report will be prepared
covering all phases of the study.
The reconnaissance level of study will require an initial aerial
survey of all drainages on the Island, walking those drainages
ranked potentially suitable for development by following them up-
stream from their mouth, gathering observations on elevations,
water flow, and environmental matters, and identifying
transmission line issues. This level of study is designed
primarily to eliminate those drainages not worthy of extended
study and secondarily to estimate the potential of those
drainages remaining in the study. As noted in the proposed
Evans Island Hydroelectric Study: A Proposal -5-
budget, this work will involve 6 days of field work with one day
of preparation and one follow-up day of analysis.
The hydrological and environmental studies will be initiated
immediately after suitable drainages are identified. These
studies are separate and not dependent on one another.
The hydrological study will require placement of temporary weirs
in those watercourses selected and equipment necessary to collect
water flow data and precipitation information. The equipment,
Stevens' Telemark II recorders with transmitting capability, will
send cumulative daily readings to a central receiving station
located conveniently and within line-of-site of the transmitting
weirs. At the receiving station a PC computer will store the
collected data from all reporting stations on disk. These disks
will be removed monthly, sent to Mt. Energy offices and prepared
for analysis.
Concurrent with hydrological studies, environmental studies will
be made on those drainages fitted with weirs. The concerns of
this study will be to assess anadromous fish habitat (spawning
and rearing areas, size and timing of runs etc.), as well as
plants and wildlife in the drainages and what potential impact
hydroelectric development may have on them. Furthermore, the
study will examine watercourses to determine optimum water levels
required to maintain suitable habitat for anadromous fish in
preparation for negotiations with wildlife agencies. Finally,
environmental assessments of transmission line routes will be
made with statements on potential impacts and mitigation
procedures necessary for these routes.
The hydrological study will run for one year. The environmental
study field work will be completed concurrent with weir
installation. Assuming that the studies are begun in the Spring
of 1988, by late fall of that year a preliminary analysis of
findings will be initiated. All of the environmental papers and
such will be prepared and flow duration curves will be prepared
for the months covered by the water study. Preliminary
conclusions can then be drawn, and possible applications for
permitting will be initiated at that time. The final completed
feasibility study, attendant reports and recommendations will be
ready for distribution within 13 months after initiation of the
study.
Listed in the budget below are not only line item expenses, but
categories of work to be completed in every area of study.
Obviously, if Mt. Energy is commissioned to do the work, a
detailed list of all expectations will accompany any contract
concerning the job. It is hoped that the budget below is
comprehensive and clear.
Evans Island Hydroelectric Study: A Proposal
Recon: 4 round trip Medford-New Chenega
Travel time (l/2 time 4 people)
8 days crew (l-prep/6-field/l-analysis)
8 days support labor
6 ea. crew drainage drop & pick-up boat trips
4 hours air survey
Per diem expenses @ $40
2 days Environmental liaison in Anchorage
+ $75 per diem
Field Study: 3 unit installations
3 remote data collection units I l receiving
l round trip Mdfrd-New Chenega and travel time
l collection station shack (Unit & labor)
9 days weir installation (three units)
9 ea. boat pick up and delivery to each drainage
l day helicopter (weir material drops)
l day collection station setup
2 days environmental liaison in Anchorage
+ $75 per diem
6 days environmental field work
16 per diem @ $40
10 days support labor
Data Collection:
12 days monthly collection of disks & expenses
12 days (3 days/yr/unit maintenance check)
Shipping costs
Administration
Data preparation
Data Analysis and Feasibility Report:
Environmental Analysis: 10 days
Environmental assessment for each drainage
Agency liaison
Feasibility report
Report review
-6-
$3,000
690
4, 720
800
600
800
1,280
450
15,500
850
2,400
4,860
900
3,000
440
450
900
2,640
1,000
1,440
1,440
156
240
456
1,500
Engineering Report: 15 days 3,000
Hydrological analysis--flow duration curves
Report on potential power, each site & system
Site ranking
Preliminary design --top ranked sites
Transmission line report & route ranking
Project map(s)
Preliminary budget preparation
Feasibility report
Report review
Evans Island Hydroelectric Study: A Proposal
Feasibility Study: 15 days
Study administration
Power needs analysis (present & future)
Site ranking
Budget preparation for top ranked sites
Economic analysis
Agency interface
Permit study and application outlines
Hatchery interconnection study
Development plan re surplus power
Feasibility report
Report review
Drafting:
Report Preparation and Printing (25 copies)
Contingency (10%)
Contracting (15%)
Total
-7-
4,800
1,250
690
6,025
9,038
$75,315
Completion of the proposed study as described above will
definitively determine the potential for hydroelectric
development on Evans Island, including how much power can be
expected, how much it will cost, the difficulties involved in
licensing (if there are any), preliminary design of the project,
the cost of delivering the power, and what can be done with the
power. The body of the report will also serve as the basis for
all applications which will be required.
Mt. Energy is pleased to have
proposal and is ready to carry
soon as it is authorized.
the opportunity to prepare this
out the study expeditiously as
APPENDIX
1. Annual hydrograph -Anderson Creek
2. New Chenega hydroelectric assesment-Corps of Engineers Report
3. Crab Bay Dam No. 4, Evans Island -Safety Inspection Report
4. Turbine description and cost estimate
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Month
Annual Hldrofjrapb a± Ncntih o~ Anderson Creek
Tht!. ..shoJed area represef"'T The. pori/en ~f t"•t"•l -l!loeu
wh,·<:."' ,·s ret:r;u.,'t-~ .ft:>r rJ..e Che..,e~Q B•y ~--V"ter .,v.pplf (o.o?. C~$).,
6.0 NEW CHENEGA
6.1 COMMUNITY DESCRIPTION
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1' ec•::; 1 1.H>c
New Chenega would be a new community {now in the planning stage)
located on Evans Island in the Prince William Sound. The village, to
be built by the Chugach Native Corporation, is intended to replace the
original Chenega Village located on Chenega Island, which was destroyed
in the 1964 earthquake. Many of the prospective residents are second
generation Chenega survivors relocating primarily from Anchorage and
Valdez. Plans for the community include 21 families by the fall of
1982, an elementary school, village store, floating dock to accomodate
300 boats, and community hall. The houses would be provided by HUD and
wood stoves are incorporated into the home plans. The population is
expected to grow and plans exist for 10 additional lots.
Families will support themselves economically from fishing, a fuel
depot that would be constructed on the floating dock, and the existing
fish hatchery, which will employ approximately three persons. There
are three abandoned canneries but there are no plans to revitalize them
by the New Chenega IRA Villge Council due to limited funds.
The Village Council is interested in developing a reliable source of
electrical energy, preferably a renewable resource. The Council is
planning to purchase 2 -75 kW diesel generators but intends to use
them for backup power. The San Juan Aquaculture Corporation has a
60 kW hYdropower facility behind the hatchery. The plant is operating
at full capacity, however, and would not be able to meet the community
needs except, possibly, at irregular intervals of time.
A study of future energy requirements of New Chenega was conducted
through the Alternative Energy Technical Assistance Program (AETAP)ll.
Po\ter projections were made based on a review of existing data sources
and original calculations by AETAP. Total electrical energy
requirements were projected to be 154,075 kWh/year for the residential,
commercial, and institutional sectors, and 217,671 Ulh/year to include
the additional requirements from the community center, which would
contain a laundromat. These calculations correspond with Ebasco•s
electrical energy projections for years 1983-1986.
6.2 SITE SELECTION
Several potential hYdro development sites appear to be located close to
the proposed New Chenega village on Evans Island. The four most likely
sites all possess small headwater lakes and were all overflown during
the field inspection. Site 04, located a quarter mile west of and some
200 feet above the San Juan Aquaculture facilities appears, however, to
be already fully developed, judging both from conversations with
personnel and from field observations.
1/ New Chenega Alternative Energy Plan, undated.
6-1
The site located one quarter mile south of Guguak Bay (on the west side
of the island} \<tas previously identified by others. but was not
inc 1 uded in this screening. It seems to. be the 1 east attractive of the
remaining sites because the head avilable is only about 100 feet.
Site 03, three miles northeast from Crab Bay, offers about 600 feet of
gross head, connecting a small lake to the seashore in somewhat less
than a mile. A small, triangular-shaped, 20 foot high dam with a
30 foot crest length could plug the gully, cut in sedimentary rock. By
cutting a trench through a narrow rock ledge downstream of the lake,
six to eight feet of storage within the lake would be utilized by this
small dam. This project also possesses an attractive site for its
powerhouse, on rock ledges near the water's edge.
Site 05, on 11 Section 22 Lake", appears, however, to be slightly more
attractive because its penstock and transmission line are one third
shorter than for Site 03, while the head is the same. A 100-foot long
and 15-foot high concrete dam would be seated directly on bedrock at
the outlet of the lake and would raise its storage elevation by
approximately five feet. This site appears to be that preferred by the
Corps of Engineers on page 12 of its 1976 Trip Report. The bedrock,
according to USGS Map T-1150, is greenstones and sedimentary rocks.
The likelihood that a basalt.sill forms the rock barrier at the outlet
of the lake could not be confirmed.
6-2
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NOTE: TOPOGRAPHY FROM U.S. G. S.-SEWARD
ALASKA 1 I: 250,000
LEGEND
'Y DAM SITE
• POWERHOOSE
0 SITE NO
-----PENSTOCK
---TRANSMISSION LINE
--WATERSHED
·-·-· .. --........... :-----···· ...... ··-··-... .
5 0 5
E3 E3 t=i
SCALE IN MILES
REGIONAL INVENTORY a RECONNAISSANCE STUO't'
SMALL HYDROPOWER PROJECTS
SOUTHCENTRAL ALASKA
HYDROPOWER SITES IDENTIFIED
IN PREUMINARY SCREENING
NEW CHENEGA
DEPARTMENT OF THE ARMY
ALASKA DISTRICT CORPS OF ENGINEERS
Hydropower Potential
Installed
Capacity
Site No. ( kW)
5 98
Demographic Characteristics
SUt1MARY DATA SHEET
DETAILED INVESTIGATIONS
NEW CHENEGA, ALASKA
Cost of
Installed Al ternaji ve
Cost Power_/
( $1000) (mi 11 s/kWh)
2,597 466
1981 Population: 94 (by autumn of 1982)
Cost of
ftfdropower
(mills/kWh)
720
1981 Number of Households: 21 (by autumn of 1982)
Economic Base
Fisheries (planned)
ll 5 Percent Fuel Escalation, Capital Cost Excluded.
Benefit/Cost
Ratio
0.65
See Appendix C (Table C-8)) for example of method of computation of cost of
alternative power.
f;·EGlfjrJAL IrJVErJTORY & RECOtHJAISAi'JCE STU[tY-SMALL HY[tF:OF·ijWER F·ROJECTS
'fEAR
·eo
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
20t)2
2003
.. 2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
.2026
2027
2028 ·-")-.v-..,
. -,
ALAS~A DISTRICT -CORPS OF ENGINEERS
LOAD FORECAST -NEW CHENEGA
KILOWATT-HOURS PER YEAR
LOW MEDIUM HIGH
o.
42708.
85416.
128124.
170832.
213540.
256247.
298955.
341663.
384371.
427079.
444941.
462802.
480664.
498525.
516387.
534248.
552110.
569971.
587833.
605694.
621152.
636610.
652069.
667527.
682985.
698443.
713901.
729360.
744818.
760276.
769227.
778178.
787129.
796080.
805030.
813981.
622932.
831883.
840834.
849785.
860626.
871466.
882307.
893148.
903988.
914829.
925670.
936511.
947351.
958192.
o.
42708.
85416.
128124.
170832.
213540.
256247.
298955.
341663.
384371.
427079.
459758.
492437.
525116.
557795.
590475.
623154.
655833.
688512.
721191.
753870.
788904.
823937.
858971.
894004 •
929038.
964071.
999105.
1034138.
1069172.
1104205.
1118677.
1133150.
1147622.
1162095.
1176567.
1191039.
12ii5512.
1219984.
1234456.
1248929.
1266178.
1283426.
1300675.
1317924.
1335172.
1352421.
1369669.
1386918.
1404167.
1421415.
o.
42708.
85416.
128124.
170832.
213540.
256247.
298955.
341663.
384371.
427079.
474576.
522073.
569569.
617066.
664563.
712,i60.
759557.
807054.
854551).
902047.
956656.
1011265.
1065873.
1120482.
1175091.
1229700.
1284308.
1338917.
1393526.
1448135.
1468129.
1488123·
1508116.
1528110.
1548104.
1568098.
1588091.
1608085.
1628079.
1648073.
1671729.
1695386.
1719042.
1742699.
1766355.
1790011 •
1813668.
1837324.
1860980.
1884637 •
Ai'WIJAL PEAt~ I•EHArHI-Kc·
LOW MEDIUM HIGH .
o.
15.
29.
44.
59.
73.
88.
102.
117.
132.
146.
152.
158.
165.
171.
177.
183.
189.
195.
2\j 1.
207.
213.
218.
229.
234.
239.
244.
250.
255.
26t).
263.
266.
270.
273.
276.
279.
285.
288.
291.
295.
298.
302.
306.
310.
313.
317.
321.
324.
328.
o.
15·
29.
44.
5¥.
73.
88.
102.
117.
132.
146.
157.
169.
18t).
191.
202.
213.
225.
236.
247.
258.
270.
294.
306.
318.
330.
342.
354.
366.
378.
383.
388.
393.
398.
403.
4i)8.
413.
418.
423.
428.
434.
440.
445.
451.
457.
4.->3.
469.
475.
481.
487.
o.
15.
44.
59.
73.
5f1.
FJ2. -
117.
132.
146.
163.
179.
195.
211.
228.
2£l4.
2.::,\j.
.! / •:"l.
293.
31)9.
328.
346.
365.
384.
402.
421.
440.
459.
477.
4¥6.
5ti3.
510.
5i6.
523.
530.
537.
544.
55 L,
558.
564.
573.
581.
589.
597.
605.
613.
621.
629.
637~
645~
.. -
NEW CHENEGA SITE 5
SIGNIFICANT DATA
DETAILED RECONNAISSANtE INVESTIGATIONS
1. LOCATION (diversion)
Stream: Unnamed (Section 22 lake)
Section 22, Township 15, Ran~e BE, Seward Meridian
Community Served: Crab Bay {New Chenega)
Distance: 1.7 mf Direction (community to site):
Map: USGS, Seward (A-3), Alaska
2. HYDROLOGY
Ora i nage Area:
Estimated Mean Streamflow:
Estimated Mean Annual Precipitation:
3. DIVERSION DAM
Type:
Height:
Crest Elevation:
Vol urne:
4. SPIllWAY
Type:
Opening Height:
Width:
Crest Elevation:
5. WATERCONOUCTOR
Type:
Diameter:
length:
6. POWER STATION
Number of Units:
Turbine Type:
Tailwater Elevation:
Rated Net Head:
Installed Capacity:
Maximum Flow:
Minimum flow (single unit):
7. ACCESS
length:
8. TRANSMISSION LINE
Voltage/Phase:
Terrain:.!/ Rolling {1.25)
Total length:
9. ENERGY
Plant Factor:
Average Annual Energy Production:
Method of Energy Computation:
10. ENVIRONMENTAL CONSTRAINTS: Unknown
1/ Terrain Cost Factors Shown in Parentheses.
0.5
4.0
160
sq mi
cfs
in
Northwest
large Concrete Gravity
15 ft
625 fmsl
340 cu yd
Concrete Ogee
2.5 ft
18 ft
622.5 fmsl
Steel Penstock
12 in
3300 ft
1
Pelton
10 fmsl
604 ft
98 kW
2.4 cfs
0.48 cfs
0.6
14.4
2.2
2.2
47
403
mi
kV/1 phase
mi
mi
percent
MWh
Plant Factor Program
' ...
.. ..
~,.
NE/SC ALASKA SMALL HYDRO RECONNAISANCE STUDY
PLANT FACTOR PROGRAM
CUMt·tUtl I TY: NEW CHENEGA
SITE NU~1BE R: 5
NET HEAU (FT): 604.
DESIGN CAPACITY (KW): 98.
MI NIMUt1 OPEI<ATING FLOW (I UNIT) (CFS): 0.48
LUAU SHAPE FACTORS: 0.50 0.75 1.60 2.00
HOUR FACTORS: 16.00 15.00 13.00 3.00
MONTH (#DAYS/MO.) AVERAGE POTENTIAL
MONTHLY HYDROELECTRIC
FLOW ENERGY
(CFS) GENERATION (KWH)
JANi.JAI<Y 1.44 43949.
FEBRUARY 1.10 30323.
MARCH 0.95 28994.
API<I L 1.30 38396.
MAY 4.57 72912.
JUNE 10.20 70560.
JULY 8.33 72912.
AUGUST 5.55 72912.
SEPT£MBEH 5.30 70560.
OCTOBER 4.07 72912 •.
NOVEMBEH 3.32 70560.
DECEI~oER 1.94 59209.
TOTAL 704200.
PLANT FACTUR(l997): 0.46
PLANT FACTOR(LIFE CYCLE): 0.47
PERCENT ENERGY USAI.ilE
OF AVEKAGE DEMAND HYURO
ANNUAL ENEKGY . ENEHGY
(KWH)
10.00 55211. 28407.
9.50 52450. 2004~.
9.00 49690. 19157.
9.00 49690. 24939.
8.00 44169. 42241.
5.50 30366. 30366.
5.50 30366. 30366.
6.00 33127. 33127.
8.00 44169. 41901.
9.00 49690. 43635.
10.00 55211. 42821.
10.50 57971. 36903.
552109. 393905.
HYDROPOWER COST DATA -DETAILED RECONNAISSANCE INVESTIGATIONS
Community: New Chenega
Site: 5
Stream: Unnamed (Section 22 Lake)
ITEM
1. Darn (including intake and spillway)
2. Penstock
3. Powerhouse and Equipment
-Turbines and Generators
-Misc. Mechanical and Electrical
-Structure
-Valves and Bifurcations
4. Switchyard
5. Access
6. Transmission
TOTAL DIRECT CONSTRUCTION COSTS
7. Construction Facilities and Equipment,
Camp, Mobilization, and Demobilization
TOTAL INDIRECT CONSTRUCTION COSTS AT 20 PERCENT
SUBTOTAl
Geographic Factor a
SUBTOTAL
Contingency at 25 percent
SUBTOTAL
Engineering and Administration at 15 percent
TOTAL CONSTRUCTION COST
Interest During Construction at 9.5 percent
TOTAL PROJECT COST
Cost per kW Installed Capacity
ANNUAL COSTS
Annuity at 7-5/8 percent (A/P = 0.07823)
Operations and Maf ntenance Cost at 1. 5 percent
TOTAL ANtlUAL COSTS
Cost per kWh
Benefit-Cost Ratio
COST
J 107,000
~ 89,000
~ 67,000
' 149,000
~ 30,000
. ~ 6,000
J 99,000
' 9,000
~ 69,000
~ 625,000
s 125,000
~ 700,000,_./
2.2
s 1,650,000
J 413,000
~ 2,063,000
s 309,000
s 2,372,000
' 225,000
~ 2, 597,000
~ 26,500
~ 203,200
~ 70,000
~ 273,200
~ 0. 72
0.65
c
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( ._
f",E,_.iONAL .INVENTORY~~ F:ECONNAI:::ANCE ::::rUDY-:::MALL th'DROPOt.lfR PRO.Jt;CT:::
YEAF'
19S4
1 ·~~:::6
1':;87
19:::9
1990
1 ·;1·~11
1992
19'~1 :3
1994
1':;-195
1991;.
1'~97
2000
2001
2002
zoo:;:
2004
2005
200(:.
2007
2008
2009
2010
2011
2t)12
201 :;:
2014
2015
201/:..
2017
201:::
2019
2020
2021
2(•22
2024
2(»25
2(127
2(t28
2(J2~'
ALASKA DISTRICT -CORPS OF ENGINEFRS
DETAILED RECONNAISSANCE INVESTIGATIONS
COST OF HYDROPOWER -BENEFIT COST RATIO
NEW CHENEGA
:;:ITE NO. 5
KWH/YEAR
170::::45.
24:3044.
272477.
2·~~·~:;::3::::.
:;:2:321;..4.
345609.
:35422·?.
::::75!570.
:3:32010.
~::::7~1 8(J.
:~:·;t:;:·~f)5.
402::::51.
406705.
4()•;,:=:~:~;.,.
412'::1:3':i.
415854.
418~·21.
4212::::9.
42:~::::57.
426475.
429094.
431712.
434244.
436442.
437542.
43'51622.
4 403'3/:3.
4411~.5.
441:?.13.
442256.
442:.:.·::/9.
443222.
44:3738.
444247.
444740.
4452:34.
445727.
446221.
446714.
4471(:.7.
CAPITAL
2044:::::::.
20448::::.
2044:?.:?..
2(J44:3:::.
204488.
20448:3.
20448:3.
204488.
2044:38.
20448:3.
2044:3:3.
2044!38.
2044:3:::.
2(>4488.
204488.
2044:::::::.
2044:38.
2(>4 4:;::=:.
2044:::8.
204488.
21)448:3.
204488.
2044:::8.
2(144:3:::.
20448:3.
2(>44E:r::.
2t)44:=:::;.
2044:3:3.
2044:38.
204488.
2044e::::.
20448:3.
2()44~:C::c.
2(>44:3:3.
2(>44::::=:.
2()44!3:3.
2044:38.
2044:38.
204 4::::::.
$/KWH S/t(WH
TOTALs NOND I SC D I :::c
274488. 1.611 1.201
27448:?.. 1.311 O.'i'08
2744:38.
2744:2:8.
2744~::::.
2744::::3.
2744:38.
27448:3.
2744:::8.
:;;:74488.
274488.
2744:::8.
27 44::::::.
27448:3.
27 44::::::.
27 44::::::.
2744t::::.
274488.
2744::::3.
2744:::8.
274488.
27448:3.
2744:::8.
274488.
27448:3.
274488.
274488.
2744::::3.
274488.
274488.
27448:3.
274 4:.?.8.
2744::::8.
274488.
274488.
1. 129
1. (107
(1.917
o. :349
\). 794
0.775
o. 75'~/
0.745
0.731
0.719
0.7(17
(l' .t./=17
0. t:.:::=:.::
0. ,;.::: 1
0.675
0.670
0.665
0.660
0.656
€). c.52
o. t.48
0.644
(l. tAO
0.636
0.632
0.631
0. ~.29
0.627
O.l:.26
(1.624
0.623
c). 622
(1. ~.21
0./:.21
0.727
C) •• ~.(12
0. 50'?
0.4'38
l). ~!81
o. :,;:LJ.5
1).:314
I). 2::::7
0.261
0.239
o. 21:3
0.200
0. 1:::::::
0.169
o. 155
0.143
0.132
0.122
0.112
0. 104
0. (1·~6
o. 08';:'1
0.082
0.075
0.07()
0.065
0.060
0.056
0.051
o. (14:3
0.044
0.041
(1. o:::::::
o. o::::5
20::::0 4 4 T'5'=12.
20448:3.
204 4:::::3.
0 ~< M
70000.
7000(1.
7(11)00.
700(1(1.
7(1!)(1(1.
70000.
70000.
70000.
70000.
71)(1(1(1.
70000 •.
70000.
70000.
700(10.
70(1(1(1.
7(1(1(1(1.
70000.
70000.
70000.
70000.
7000(1.
70000.
7(1(1(1(1.
70000.
70000.
70000.
70006.
70000.
70000.
70000.
70000.
70000.
70000.
700(10.
70000.
7(11)(1(1.
70000.
70000.
70000.
70000.
70(l(H).
70000.
7(1(1(10~
70000.
70000.
70•)00.
70000.
274488. (1.620 0.033
274488. 0.619 0.030
~74488. 0.619 0.078
274488. 0.618 0.026
274488. 0.617 (1.024
274488. 0.617 0.023
274488. 0.616 0.021
274488. 0.615 0.019
274488. 0.614 0.018
274488. 0.614 0.017
274488. 0.613 0.016
AVERAGE COST (1.717 (1.188
BENEFIT-COST RATIO C5% FUEL COST ESCALATION>: 0.65
':24
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·•·~ DAM
·.·: .. ·,-'· .·· ....•. y~:: .. ·.·~ _________ PE_Ns_r_OCK _______ --1
· •• "11111111111 TRANSMISSION LINE .... -------------------1
· · ·. :• . ·. • POWERHOUSe .... -------------------1
... [ .. 1·\£; ~~ ~-:.· :::· ';:· ,' :'.,._ J DRAINAGE BAS IN
REGIONAL INVENTORY & RECONNAISSANCE STUDY
SMAU HYDROPOWER PROJECTS
SOUTHCENTRAL ALASKA
NEW CHENEGA SITE 05
CONCEPTUAL LAYOUT
SECTION 22 LAKE
DEPARTMENT OF THE ARMY
ALASKA DISTRICT
CORPS OF ENGINEERS
NEW CHENEGA
TOWNSITE
.$awmill
~-..
CONSULTANTS
William L. Shannon, P.E.
Stanley D. Wilson. P.E. 55111
SHANNON & WILSON, INC.
Geotechnical Consultants
5621 Arctic Blvd., Suite B • Anchorage, Alaska 99518 • Telephone (9(ln 561·2120
April 1, 1986
State of Alaska
Department of Natural Resources
Division of Land and Water Management
555 Cordova Street: Box 7-005
Anchorage, Alaska 99510
Attention: Mr. Kyle J. Cherry, P.E.
RE: PERIODIC SAFETY INSPECTION REPORT, CRAB BAY DAM NO. 4
CHENEGA VILLAGE, EVANS ISLAND, ALASKA
Gentlemen:
A-216
We are pleased to submit herewith our final inspection report for
crab Bay Dam No. 4. This is generally a new dam that was discovered
during our inspection visit to Crab Bay Dam No. 3. Based on our conver-
sations, it was mutually decided to prepare a Phase I report on this dam
instead of the older dam because of the new dams greater importance to
the village. This dam is classified by the Department of Natural
Resources as non-jurisdictional.
Mr. Fred Brown of our office and Mr. craig Freas from Tryck Nyman &
Hayes visited the above referenced site on September 23, 1985, and
performed the periodic inspection. In additional to this report, video
cassette recordings were taken at the dam in VHS format and were later
edited and narrated. These recordings are attached as additional
support information for this dam.
We have appreciated the opportunity to be of service to you.
Sincerely,
SHANNON & WILSON, INC.
By: :t ..,..,.,UP .Bnm,._J
Fred R. Brown, P.E.
Senior Associate
FRB/slt
Sea tile SPOkane
R. Brown, Jr .• P.E.
Manager
Porlla~d Falrbanka St. Louie Anchorage
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Title Sheet
CRAB BAY DAM NO. 4
Non-Jurisdictional Dam
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0 0 Alaska, LOngitude 149 l'W and Latitude 60 4.2'N, Unnamed Creek
Owned by the Chenega Native Association
Size Classification:
Hazard Classification:
Small
Low
Inspectors: Fred R. Brown, P.E.
Approved By:
Geotechnical Engineer
Craig Freas, P.E.
Civil/Structural Engineer
J~R.~
Fred R. Brown, P.E.
Shannon & Wilson, Inc.
Anchorage Manager
Review Board: Kyle J. Cherry, P.E.
Approved By:
State Dam Safety Engineer
Kenneth B. Hunt
Dam Safety Engineer
Carol Larson
Hydrologist
Alaska Department of Natural Resources
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EXECUTIVE SUMMARY
On December 2, 1977, President Carter initiated a National Dam
Safety Program by directing the Corps of Engineers to administer a
program of inspection of all dams classified as high hazard potential by
reason of their location. The National Dam Safety Program was completed
in 1982. It was intended that each state would thereafter accept
responsibility for non-federal dams located within their jurisdiction.
In July 1966, Governor William Egan signed Alaska Statute AS 46.15
"Water Use Act" under which the Alaska State Dam Safety Program has been
initiated.
Under AS 46.15, Crab Bay Dam No. 4 was inspected for the first time
on September 23, 1985, by Shannon & Wilson under contract to the State
of Alaska, Department of Natural Resources, Division of Land and Water
Management. The dam, constructed in 1984, is an 8-foot high 12-inch
wide reinforced concrete wall embedded within a rock foundation. Wood
plank inserts in the center of the dam form the spillway and provide for
reservoir level adjustments. The dam is designed for overtopping,
however, under extreme flood conditions it is possible that the plank
cat-walk, stairs or water supply piping may be damaged and could require
replacement or repair. The reservoir volume and the height of the dam
classify it as a small size dam. Because of the small reservoir, dam
failure would pose no safety or economic hazards other than temporary
loss of water supply. Although this latter condition may create an
inconvenience to the villagers, it is not considered serious as there is
typically year around water flow in the creek. No major industry
activity is occuring in the village at this time. The dam is therefore
classified as having a low hazard potential. The dam appears to be well
maintained and no critical deficiencies were found. No remedial treat-
ment or suggested changes appear warranted.
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EXECUTIVE SUMMARY
TABLE OF CONTENTS
CRAB BAY DAM NO. 4
PFOJECT DATA
1. INTRODUCTION
1.1 Authority
1.2 Purpose and Scope
1.3 Inspection Team
2. PROJECT DESCRIPTION
2.1 Location
TABLE OF CONTENTS
2.2 Size and Hazard Potential Classification
2. 3 Purpose of Dam
2.4 Construction History
2.5 Geology, Seismicity and Climate
2.6 Basin Description
2.7 Description of Project
2.8 Operation and Maintenance
3. FIELD INSPECTION
3.1 Reservoir Area
3.2 Dam
3.3 Abutments
3.4 Outlet Works
3. 5 Spillway
3.6 Downstream Channel
3.7 Instrumentation
4. HYDROLOGY
4.1 Spillway Design Flood (SDF)
4.2 Methodology
5. HYDRAULICS
5.1 Methodolgy
5.2 Spillway Capacity
5.3 Outlet Capacity
5.4 Results
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1
1
1
2
2
2
3
4
4
5
7
8
9
10
10
11
12
12
12
13
13
13
13
13
14
14
15
15
15
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• • • • • • • ••
• • • • • • • •
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TABLE OF CONTENTS (Cont 1 d)
6. STRUCTURAL STABILITY
7 . PRIOR REPORTS
e. CONCLUSIONS
8.1 conclusions
8.2 Recommendations
REFERENCES
LIST OF FIGURES
Fiqure Number
1
2
3
4
5
6
APPENDIX A
Location & Vicinity Map
Aerial Photo
Dam Plan Elevation & Section
Epicenter Map
Geologic Setting
Seismicity Map
APPENDICES
Photographs taken September 23, 1985
A-216
Page
16
16
16
16
17
18
APPENDIX B Corps of Engineers Forms & Visual :Inspection Checklist
APPENDIX C Hydraulic Analyses Computer Output
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CRAB BA V DAM NO. 4
--
SHANNON • WILSON, INC.
Geotechnlcel Coneultanta
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PROJECT DATA
CRAB BAY DAM NO. 4
GENERAL
Name ••
Location ••
Year Built • •
Purpose • • • •
I.D. Number ••••
Hazard Classification. •
Size Classification. •
Owner. . . . • . . . .
DAM
'!YPe • • • • • • • •
Crest Length •
Crest Width ••
Crest Elevation. •
Height • • • • . • •
SPILLWAY
'lYPe • .
Location •
Side Slopes. •
Crest Elevation ••
Bottom Width • • • •
!Jength . • . . . . .. • •
Discharge Capacity at Dam Crest ••
Stop Timbers in • • • • • •
Stop Timbers at El. 248' {normal)
Stop Timbers out
OUTLET WORKS
'!YPe • • • • • • • •
Location • • • • • •
Invert Elevation .
Size . . . . . . . . . . . . . .
I.£nqth . . • . • • • • • · · • •
Outlet Type ••.•••••••
Discharge Capacity at Dam Crest. .
v
Crab Bay Dam No. 4
Evans Island, Alaska
1984
Water Supply
None {non-jurisdictional)
Low
Small
Chenega Native Association
Evans Island, Alaska
Gail Evanoff {907)573-5114
Chuck Totenosf " 573-5111
Reinforced Concrete Wall
19 ft.
1 ft.
252 ft.
7.5 ft.
Ungated Overflow Chute w/
Timber Inserts
Center of Dam
Vertical Dam Walls
Variable w/Timber (max.
4'4" below crest)
1 ft.
4 ft.
0 cfs
110 cfs
135 cfs
Steel Pipe w/ shear gate
Below edge of spillway
245.5 ft.
12 in.
3 ft.
12" pipe free discharge
15 cfs
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RESERVOIR
Normal Maximum Water Surface Elevation
Water Surface Elevation at Dam Crest •
Maximum Storage Volume at Dam crest. •
Maximum Storage Area at Dam Crest .••
Storage Volume at Spillway Crest • • •
Surface Area at Spillway Crest ••••
HYDROLOGIC DATA
Drainage Area • • • • • •
Average Annual Discharge
Flood of Record • • •
Projected Design Flow •
Return Period . • • •
vi
Approx. 250 ft.
252 ft.
<1-acre-ft.
<1 acre
< 1-acr,-ft.
600 ft
0.37 mi 2
3.2 cfs
None recorded
385 cfs
100 years
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1.1 Authority
CRAB BAY DAM NO. 4
EVANS ISLAND, ALASKA
1. ·INTRODUCTION
A-216
Inspection authority is Alaska Statute AS 46.15 "Water Use Act"
signed by Governor William Egan on July 1, 1966. Inspection procedures
and criteria for a Phase I Inspection are set. forth in the "Recommended
Guidelines for Safety Inspection of Dams" Appendix D, Volume I, u.s.
Army Corps of Engineers report to the u.s. Congress on National Program
of Inspection of Dams, dated May 1975, and published under Title 33CFR
Part 222.
1.2 Pu;pose and Scope
The purpose of the Alaska Dam Safety Program, Periodic Dam Safety
Inspections is to assemble information and records on existing
non-federal dams located within the State of Alaska and t.o insure
continued public confidence in the integrity and safety of these impor-
tant structures.
The scope of the report is to compile results of a visual in-
spection of Crab Bay Dam No. 4 and an examination of currently available
information relating to design, construction and performance history of
the project. Potential risk to upstream and downstream residents is
evaluated and preliminary spillway adequacy and structural assessments
are made. Finally, adequacy of existing records and documents relating
to the project are discussed and recommendations for additional studies
and/or remedial actions are made .
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1.3 Inspection Team
The inspection of Crab Bay Dam No. 4 was conducted on September 23,
1985, by Fred R. Brown, P.E. of Shannon & Wilson, Inc., and Craig Freas,
P.E. of Tryck Nyman & Hayes. Mr. Fred Brown is a 20 year employee of
Shannon & Wilson and the Anchorage office manager. He served as the
project manager with a strong background in geotechnical engineering.
Mr. Craig Freas is a 5 year employee of Tryck Nyman & Hayes and a
partner in the firm. He accompanied Mr. Brown on the dam inspections
and provided the civil/structural input on this dam. Mr. Tony Leonard,
P.E. hydraulics engineer with Tryck Nyman & Hayes, provided the hydrau-
lics input on this project.
The inspection team traveled to Evans Island by float plane charter
and landed at Crab Bay. They walked through the village and up the hill
to the dam site for the inspection. Mr. Jim Crum of the Public Health
Service was subsequently visited in Anchorage. He is a representative
of the dam 1 s designer and provided "as-built" drawings of the dam, a
plan map of the village and stream flow calculations used to design the
dam. Permission to visit the dam was obtained by telephone from Mr.
Chuck Totenosf (573-5111) and Ms. Gail Evanoff (573-5114), both
residents of Chenega. The courtesies extended by Mr. Crum and the
people of Chenega are gratefully acknowledged.
2. PROJECT DESCRIPTION
2.1 Location
Crab Bay Dam No. 4 is located on an unnamed creek, approximately
2500 feet north of the new Chenega Village and an equal distance west of
Crab Bay on Evans Island in Prince William Sound. fobr~ specifically,
the dam has coordinates of longitude 148°1' W and latitude 60°4.2 1 N.
As shown in Figure 1, the dam and watershed area are situated about 250
feet (MSL} directly upslope of the new village. The creek below the dam
flows in a narrow rock gorge for about 600 feet where grade change is
rapid with steep running water and several local water falls approaching
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10 feet or more. Change in elevation in this area is estimated to be in
the order of 100 feet or more. The creek shown in Figure 2, then bends
to the south, flows over the old 10 foot high cannery dam (Crab Bay Dam
No. 3) and gradually flows north of the new village and into Sawmill
Bay. Access to the dam is by way of a newly constructed unpaved road
which leads up the hill and ends at the dam's right abutment.
The dam was designed by the U.S. Public Health Service and is now
owned and operated by the Chenega Native Association. It has been
defined as a non-jurisdictional dam by the Department of Natural
Resources.
2.2 Size and Hazard Potential Classification
2. 2.1 Size Classification -The height of Crab Bay Dam is about
7. 5 or 8 feet on the downstream side and the reservoir has a maximum
storage capacity of less than a half acre foot. The size classification
is determined by the height of the dam or the maximum storage capacity,
which ever gives the larger size category. A small size dam is from 25
to 40 feet in height or from 50 to 1000 acre feet of maximum storage
capacity. Even through Crab Bay Dam No. 4 is smaller than the minimum
criteria above, it will be considered in the small size category, the
minimum defined size category.
2.2.2 Hazard Potential Classification The hazard potential
classification of the dam is determined based on loss of life consid-
erations and the resulting economic impacts in the event of a dam
failure. Because of the small size of the reservoir and the configura-
tion of the downstream channel, a dam failure would likely not cause
flooding of the village and loss of life. Further, it is unlikely that
the flood wave would leave the stream channe'l and therefore downstream
damage would be negligible. The only economic loss would be a temporary
loss of the village water supply. Since there is currently no industry
in the village that would be seriously impacted by the loss of water,
only a small impact other than costs associated with reconstructing or
repairing the dam would occur if the dam failed. The impact would
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mainly be a temporary inconvenience to the residents. Additionally,
some health problems may result if the dam is out of service for an
extended period of time. With an average of 140 inches of annual
precipitation in this area, it is likely that the village will not lack
for water for domestic purposes. Using this rational, the dam is judged
to have a low hazard potential.
2. 3 Purpose of Dam
Crab Bay Dam No. 4 was designed by the u.s. Public Health Service
and constructed in 1984 as a part of a complete new water supply system
for the new Chenega Village. The entire water supply system, shown in
Figure 2 included the dam, an access road, a 50,000 gallon tank, a
treatment plant, and associated arctic water supply pipeline from the
dam to the village.
2.4 Construction History
An as built plan, elevation and section for Crab Bay Dam No. 4 was
prepared by the u.s. Department of Health & Human Services and is
attached as Figure 3. Dates on this sheet and on Figure 2 suggest that
the dam and water supply system was designed in the fall and winter of
1983 and 84 and construction was carried out and completed in late
September and October of 1984.
The original village was destroyed in 1964 from a tidal wave that
followed the Great Alaska Earthquake. Many of the residents were killed
after which the remaining villagers scattered throughout southern
Alaska. In about 1982, state funding was obtained to reconstruct the
village to allow the natives to return to a village environment and
their former way of life. From this funding, a complete new village
including approximately 21 new homes was designed and constructed along
with support systems such as the water supply system described above.
With the exception of a few older homes, most of the facilities are less
than two years old. The dam's facilities as well as most of the village
• • • • • • • • • • • •
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therefore are new and in good condition.
required .
2.5 Geology, Seismicity and Climate
2.5.1 Regional Geology
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Little maintenance has been
Evans Island is located in Prince William Sound approximately 105
miles southeast of Anchorage. Crab Bay Dam sits above Chenega Village
on the western coast of Evans Island and is underlain by interbedded
slate and graywacke, or metamorphosed silts and silty sands. Moffit
(1954) described these rocks as slightly metamorphosed sedimentary
deposits probably of late Mesozoic age and mapped the geology of the
area as shown in Figure 4. The rocks to the west of the dam, within the
watershed area, consist of pillow lavas which are typically volcanic
flows which are extruded along the ocean floor .
The island is located within the Kenai l-buntains Fore Arc Ridge
which is composed of slabs of ocean floor deposits overlying oceanic
crust that have been intermittently sheared off when topographical
irregularities entered the fore arc trench. This setting is shown in
Figure 5. As the Pacific plate moves northwestward, sediment is
accumulated on the ocean floor from eroding continental margins such as
along the west coast of southeast Alaska. The Pacific plate acts as a
conveyor belt delivering these sediments to the fore arc trench where
the deposits are either carried into the subduction zone or are stripped
off and become accreted to the fore arc ridge (Plafker and others,
1976). The compressive forces involved in the convergence of an
ocean-continental margin have deformed the rocks resulting in complex
faulting and folding with northeast trenches parallel to the major
faults in the region (Condon & Cass, 1958). Upli;~_ within the area has
e'!]?osed the sediments as well as the underlying basaltic crust to
considerable erosion by streams and glacial scouring with only minor
deposition occurring .
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2. 5. 2 Site Geology -The dam is located in a narrow stream cut
rock gorge at an elevation of about 250 feet above Sawmill Bay to the
south. At the dam site, the gorge slopes forming the rock abutments are
steep and drop abruptly about 30 to 40 feet across an eo to 100-foot
wide section.
Bedrock exposed at the dam and in the stream channel immediately
downstream consists of thinly bedded slate or shale. This shale is
typically gray in color, moderately hard, and brittle and has steeply
dipped foliation at 50 degrees or more to the east with bedding planes
parallel to the creek. From exposed road cuts, it appears that the rock
is soft enough that it can probably be ripped in part because of its
brittle and high angle thin bedding characteristics.
The surface soils in the hills on either side of the dam and
reservoir are mostly peats and muskegs overlying the bedrock. This
organic mat was likely created as a result of poor local drainage of the
bedrock and high annual precipitation. The peats are probably up to 4
feet thick locally in the watershed area and are known to be at least 9
feet thick locally within the village proper.
The islands shape, as shown in Figure 1, is irregular and is due to
structural features; faults, folds, and differential erosion. Although
not observed at the dam site, glacially derived soils consisting of
sands and gravel are probably locally smeared over parts of the bedrock
and lie below the organic surface mat. We understand that the Alaska
Department of Transportation and Public Facilities identified one
granular source for local road construction in the village. The
quantity, however, was insufficient for this work and crushed rock had
to be used over part of the area.
2.5.3 Seismicity-Prince William Sound is located in the Aleutian
Arc Seismic Zone which extends westward from the Copper Valley, north-
east of Valdez, Alaska approximately 2500 miles along the Aleutian
Islands. The zone maintains a width of nearly 200 miles. The Depart-
ment of Commerce publication (1966) describes the Aleutian Seismic Zone
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as one of the most active in the world with nine recorded earthquakes of
Richter Magnitude, 8.0 or greater from 1899 to the present. A seis-
micity map of past earthquakes is presented as Figure 6 .
Evans Island, in the southwestern portion of the sound is clas-
sified in Seismic Zone 4. The primary cause of earthquakes in south-
central Alaska is the stress imposed on the region by the relative
movements of the Pacific and the North American lithospheric plates at
their common boundary as shown in Figure 5. In the Prince William Sound
area, this boundary appears as a large underthrust fault, or subduction
zone, called the Benioff Zone. This zone passes beneath the Evans
Island area at a depth of about 8 miles and is the source of most of the
seismic activity in the area. Although no known earthquake epicenters
have been recorded on the island since 1899 over 15 earthquakes with
magnitudes of 6 or better have been recorded within a 100 mile radius of
the island. No major faults are known to exist on the narrow island;
however, traces of probable faults or shear zones have been interpreted
from linear features (USGS, 1958).
2.5.4 Climate -The climate of Prince William Sound and particu-
larly Evans Island is maritime in nature. As shown in Table 1, mean
annual precipitation is about 160 inches and does not vary significantly
on a month-to-month basis. It generally peaks in September and remains
fairly high into December. It is generally lowest in June and the
spring months, generally about half of what it is in the fall.
Mean annual temperature is about 40°. A climatological station
(precipitation and temperature) was established at Crab Bay in 1975. A
summary of average conditions by months is attached as Table 1.
2.6 Basin Description
The drainage basin, shown in Figure 1, is about 0.37 square miles
and has a southeast exposure.
upslope of Chenega Village.
The basin is remote and lies directly
The fan shaped watershed topography is
steep and rises from elevation 250 feet at the dam site to a surrounding
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ridge which has a maximum peak elevation of about 1700 feet. The steep
slopes within the upper reaches of the basin approach 1 on 1. Because
the basin and ridges are largely comprised of bedrock the slopes are
generally stable and are not likely a potential landslide hazard.
As indicated previously the slopes are wet and covered with a heavy
growth of trees. There are also open areas on the slopes which have a
muskeg environment in part because of the generally poor drainage of
peats and the underlying bedrock.
The creek upstream of the small reservoir is confined and the water
has a relatively high velocity. The combined high velocities and thick
vegetation causes organic debris (leaves and branches) to be washed down
the creek into the reservoir where it settles out and accumulates in the
reservoir bottom. This debris will need to be cleaned out periodically.
We understand that the 12" sluice gate is opened periodically to drain
the reservoir and flush out this debris.
There are no known developments in this remote ~atershed area.
Below the dam, the water in the creek passes through a steeply cut
rock gorge. It then flows over a 10-foot high log crib dam, passes
through the village and empties into Sawmill Bay approximately 0.6 miles
below the dam. The drop in elevation from the dam to the bay is about
250 feet. Homes lie on the east side of the creek but are elevated
about 5 to 10 feet (or more) higher than the creek.
2.7 Description of Project
The dam is a reinforced concrete vertical wall structure approxi-
mately 7.5 feet high and 19 feet long across the crest. D~mensions and
locations of the key features of this dam are depicted in Figure 3. The
wall is keyed into bedrock along the foundation and in both abutments.
The abutment rock along the upstream face has been grouted. An 8" iron
channel covers the dam crest providing increased erosion protection
during overtopping and support for the cat walk.
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The spillway is an ungated overflow notch cut in the center of the
concrete dam. It has a steel lined opening 4 feet wide by 4.3' high.
Redwood tongue and groove boards inserted in the spillway bottom allow
for height control of the reservoir. A steel plate splash guard pro-
tects the adjacent water supply intake pipe and valve from the spilling
water. This detail is shown in Figure 3. The overflowing water hits a
splash pad consisting of large rocks.
The outlet structures are a horizontal intake screen and gate valve
for the water supply system and a gate valve and pipe for draining or
flushing the reservoir. The locations of these facilities are shown in
Figure 3. The water supply intake consists of a 5-foot long, 8-inch
diameter stainless steel screen connected to piping to carry water
through the dam, past a 4-inch gate valve and into a 4-inch arctic pipe
to carry the water to the treatment building. The downslope alignment
of the arctic pipe is shown in Figure 2. The other outlet is a 12-inch
diameter shear gate at the upstream face of the dam connected to a
12-inch steel pipe which discharges water directly into the downstream
channel.
An 18 to 20-foot high stairway is needed to reach the dam within
the narrow steep sided gorge. These steps approach the dam from the
upstream right abutment and provide direct access to the dam crest and
the cat walk and hand railing which pass over the dam.
2.8 gperation and Maintenance
Because the dam is relatively new, little if any maintenance
appears to have been carried out or has been needed. From our in-
spection, we observed that the upstream creek flows rapidly into the
small reservoir, and causes organic debris to collect in the reservoir
bottom. Mr. Jim Crum of the Public Health Service indicated that this
was recognized by the designers. Periodic opening of the 12-inch gate
valve quickly drains the reservoir and partially flushes out this
debris.
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Except for normal maintenance, little long term maintenance to keep
the dam and water supply system in good working condition is foreseen.
The dam is designed to accommodate periodic overtopping. Under extreme
flooding conditions, it is possible that the cat walk, the stairs or the
downstream arctic pipe may be damaged by moving debris, excessive water
flows or local rock erosion. If such conditions occur they will need to
be repaired. Based on the generally sound appearance of the dam, it is
likely that such repairs will be rare.
3. FIELD INSPECTION
The field inspection of Crab Bay Dam No. 4 was conducted on Sep-
tember 23, 1985, by Messrs. Fred Brown and Craig Freas. The two team
members landed at the Chenega Bay dock via charter plane from Anchorage
and then walked through the village up the access road leading to the
dam. They inspected the dam and reservoir area for signs of defi-
ciencies. As a part of this effort, the standard visual inspection
checklist was completed. The dam and reservoir were then photographed
from different locations as well as documented on a video cassette
recorder. Select color photographs are incorporated in Appendix A. The
video cassette tapes were later edited, narrated and are submitted as a
part of the inspection effort.
Following a visit to the site, Mr. Jim crum, representative for the
u.s. Public Health Service in Anchorage, was contacted. Mr. Crum, one
of the designers of the dam, provided "as built" drawings of the dam and
answered many questions.
3.1 Reservoir Area
The reservoir is small and is within a narrow section of the rock
gorge where the slopes are steep and covered with a thick veneer of
muskeg, grass, moss and other wet organics. Even with the steep slopes,
the moss cover suggests little signs of instability or slope failure.
If the slopes should fail, material movement would be small, consisting
of local muskeg. Additionally, the dam is designed to accommodate
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routine overtopping. Therefore the reservoir slopes and their stability
are nqt judged to have an adverse impact that would influence the long
term performance of the dam.
The steep slopes and high hydraulic gradients in the basin, how-
ever, will cause rapid runoff and peak flows which will carry greater
than normal organic debris to the reservoir. The condition is not
considered a safety hazard but rather a maintenance problem requiring
periodic flushing of the reservoir to maintain the reservoir's storage
capacity. Large debris in the form of logs or stumps could, however,
serve as a ram possibly damaging the weaker elements in the dam
requiring repair in unusual cases.
3.2 Dam
Crab Bay Dam No. 4 is located across a narrow section of a steep
stream cut rock gorge. The dam is small, new and retains only a small
quantity of water (less than 1/2-acre-feet). The concrete dam, shown in
the introductory photograph, ~pears to be structurally sound and well
keyed into the unweathered slate or shale rock foundation materials. No
seepage that would suggest adverse performance was observed in or around
the abutments or below the foundation rock.
Because of the dam's newness, the pipes, valves, gates, spillway,
cat walk and other features are in excellent condition. The splash pad
of large rocks below the spillway was intact. Evidence of erosion of
the foundation or the abutments that would endanger the stability of the
dam was not observed.
In summary the concrete dam appears to be sound and in good condi-
tion as there are no signs of distress commonly associated with dams
that are marginally stable or unstable. No evidence of settlement,
differential movement, seepage, concrete cracking or spalling or other
structural distress could be found.
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3. 3 Abutments
Both abutments as well as the foundation for the dam consist of
bedrock. The dam appears to be keyed and qrouted within the rock
foundation. As indicated previously, leakage at the rock/concrete
interface or through the rock abutments was not observed. Abutment
deterioration from normal weathering effects, primarily freezing and
thawing, was not apparent.
3.4 Outlet Works
Crab Bay Dam No. 4 has two manually operated gates or valves for
control of water flow through the dam. Both appear to be in excellent
condition. To keep these valves operational, it would be prudent as a
part of routine maintenance to open and close them periodically (at
least annually) •
3. 5 Spillway
At the time of the inspection, water was flowing over timber plank
stops keepinq the reservoir level roughly 18 inches to 2 feet below the
crest. This condition is shown in Photographs 1 and 2 in Appendix A.
The water was striking the rock splash pad roughly two feet behind the
toe of the dam. There is no evidence of excessive erosion or under-
mining of the foundation in this area. Also the downstream water supply
conduit is protected from the splashing water with a steel splash wall.
The tongue and groove wood planks appear tight allowing little, if
any, seepage between the planks. The planks can be removed for reser-
voir level adjustments either by direct removal or by opening the sheer
gate, drawing down the level in the reservoir and then .removing them
under dry conditions. The latter procedure is easily accomplished,
because of the reservoir's small size.
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3.6 Downstream Channel
The discharge from the spillway runs down the deep gorge for about
600 to 800 feet. It then bends 90 degrees, flows over an old crib dam
and down a less confined but large channel until it reaches Chenega
Village and finally Sawmill Bay. The drainage path is shown in Figure
2. Because of the basin's steep rock slopes; rapid runoff, high flows
and dam overtopping are probably a common occurrence during periods of
heavy rainfall or rapid snowmelt. Surface features do not suggest that
downstream bank overflows and terrain flooding are common. The bends
should attenuate flood waves and dam failure will not greatly influence
the flood surge as the storage capacity of the dam is so small. For
these reasons, the water is not likely to overtop the banks of the
channel under floor or dam failure conditions. The dam therefore is
assigned a low hazard classification.
3.7 Instrumentation
Monitoring instrumentation has not been installed at Crab Bay Dam
No. 4.
4. HYDROLOGY
4.1 Spillway Design Flood (SDF)
The SDF for a dam with a size classification of "small" and a
hazard classification of "low" is recommended to have a frequency of
50-100 years. The SDF for Crab Bay Dam No. 4 was generated for a 100-
year storm which had a duration of 24 hours.
4.2 Methodology
The inflow hydrograph was dete~ined by applying the 100 year storm
to a synthetic unit hydrograph. A Snyder unitgraph was developed.
Basin lag time was estimated to be 1.0 hour; the peaking coefficient was
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0. 4. Time distribution of rainfall was per EM 1110-2-1411 criteria
(Corps of Engineers, 1985). An area adjustment was not made.
The most severe storms in this area typically occur from September
through November (USWB, TP47). Climatological data is limited, but
average daily temperatures in October normally are in the mid to high
30's; snow cover averages 12-18 inches.
The storm was assumed to occur when the ground is covered with
snow. Snowmelt runoff will go into depression storage. Initial
abstractions attributed to the vegetation cover were taken to be 0.5
inches. Uniform losses where estimated to be 0.1 inches-per-hour.
A regression equation developed with a Log Pearson Type III analy-
sis which predicts the peak flow for the 100 year flood for this stream
was used to assess the results of the synthetic unit hydrograph approach
(u.s. Dept. of Agriculture, Forest Service -Region 10). With this
equation, the peak plus 100 year flow at the 90 percent confidence level
was estimated to be 290 cfs. The unit hydrograph approach yielded a
peak ordinate on the inflow hydrograph of 385 cfs. For the hydraulic
analysis of the spillway, the higher value (385 cfs) was used.
5. HYDRAULIC EVALUATION
5.1 Methodology
The hydraulic analysis of this dam was accomplished with the Dam
Safety Analysis Program provided in the u.s. Army Corps of Engineers
HEC-1 Flood Hydrograph package. Reservoir routing was by the Modified
Puls routing technique wherein the flood hydrograph is routed through
lake storage. Since the lake is small, travel time of the flood wave to
the outlet was assumed to be negligible.
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5.2 Spillway Capacity
Spillway capacity was computed by considering the spillway as a
sharp-crested weir. The equation Q=CLHl. 5 was used. L= spillway
length • 4 feet. H a height of water above the spillway crest • 4 feet
with the planks in the normal position. The weir coefficient c-3.47.
Using these terms, the discharge capacity of the spi~lway before over-
topping begins is 110 cfs.
5.3 Outlet Capacity
The analysis was performed with the 12 inch diameter outlet closed.
If this outlet was open and flowing freely, it would have a discharge
capacity of approximately 15 cfs when the water level is at the dam
crest.
5.4 Results
The storm was assumed to begin when the lake level was at the crest
of the dam. Overtopping would occur for a flood with a magnitude of
approximately 25 percent of the SDF. Maximum depth over the dam would
be approximately 2. 5 feet for 100 percent of the SDF. Copies of the
input data and output results are attached at the end of Appendix c .
Downstream effects were analyzed where the channel enters Sawmill
Bay. A channel with a 10-foot wide bottom, 1:1 side slopes, average
slope of 8 percent and a Manning's "n" of 0. 05 was examined. At 100
percent of the SDF, the water level in the channel would rise by less
than 3 feet.
The results of this analysis indicate that bank ov~rtopping would
not occur. However, Crab Bay Dam No. 3 (AK 00168), the old crib dam
less than 1,000 feet from Crab Bay Dam No. 4, would be inundated and may
fail under the conditions of the SDF. Failure of this crib dam would
introduce an abnormal amount of large debris into the stream.
debris could block the channel and cause local downstream flooding.
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6. STRUCTURAL STABILITY
The dam appears to be well built, structurally sound and, based on
the high assumed ~esign stream flows is designed to withstand
overtopping. Structural deficiencies or signs of distress that would
indicate marginal or adverse long term stability were not observed.
7. PRIOR REPORTS
The u.s. Department of Health and Human Services, Public Health
Services were the designers of this new dam. Mr. Jim Crum of the Public
Health Service, Anchorage, Alaska provided the following information, a
large part of which has been used in completing this inspection report •
1. Stream Flow Calculataions of Chenega Bay Stream Flow using the
"Water Resources Atlas", USDA Forest Service Region 10, April
1979.
2. Figures 2 and 3 in this report •
Other documents were not available regarding the design or con-
struction of this dam. More detailed historical information is,
however, in the Public Health Service's files.
8. CONCLUSIONS AND RECOMMENDATIONS
From this inspection and evaluation of Crab Bay Dam No. 4, the
inspection team presents the following conclusions and recommendations.
8.1 Conclusions
1. The dam was constructed in 1984 and appears to be well de-
signed, structurally sound and in excellent condition. No
deficiencies were found that would impair the safe operation
of the dam.
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2.
3.
4.
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Because the reservoir is small, dam failure would not cause
loss of life nor significant economic loss. It therefore is
assigned a low hazard classification.
Under infrequent flood conditions, the dam is designed to
accommodate overtopping. Under these conditions damage to
some support facilities could occur from flood forces and or
moving debris.
The reservoir can be cleaned of debris by periodically opening
the 12-inch shear gate and flushing the debris downstream.
Recommendations
1. The dam is in excellent condition and no corrective measures
are considered necessary.
2.
3.
A minimal monitoring and maintenance program is recommended to
document the long term performance of the dam and confirm the
parameters used to design the dam. Dates with the following
events should be recorded as a part of the long term files:
a)
b)
c)
d)
e)
Normal flows (monthly) -water depth in spillway
Dam overtopping & height of overtopping
Reservoir flushin9
Valve or gate exercising (at least annually)
Other repairs, maintenance, or observations that may be an
indicator of changing performance (i.e. cracks, spalling,
displacements, erosion, seepage, etc.)
Logs, stumps or other large loose debris should not be allowed
to collect against the upstream dam face.
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REFERENCES
Beilanan, H.M., 1974, "Preliminary Geologic Map of the Southeast Quadrant
of Alaska". u.s.G.s. Misc. Field Studies, Map MF 616, Scale
1:1,000,000.
Beilanan H.M., Holloway, c.o., and MacKevett, E.M., Jr., 1977,
"Generalized Geologic Map of The Eastern Part of Southern Alaska:"
u.s.G.s. Open-File Report 77-169, Scale 1:1,000,000
Condon, W.H., and cass, J.T., "1958 Map of A Part of the Prince William
Sound Area, Alaska", showing linear geologic features as shown on
aerial photographs: u.s.G.S. Map I-273, scale 1:125,000.
Espinosa, A.F., 1984, "Seismicity of Alaska and the Aleutian Islands",
1960-1983: u.s.G.S. Open-File Report 84-376, scale 1:12,500,000.
Leet, D.L., Judson, s., and Kauffman, M.E. 1978, "Seismicity of Alaska
and Aleutian Islands: in Physical Geology": Prentice-Hall, Inc., p.
147-153.
Meyers, H., 1976, A historical summary of earthquake epicenters in and
near Alaska: NOAA Tech. Memo., EDS, NGSDC-1, p. 32-42.
Moffit, F.H., 1954, "Geology of the Prince William Sound Region,
Alaska," u.s.G.s. Bulletin 989-E.
Plafker, G., Jones, O.L., and Pessagno, E.A., Jr., 1976, "A Cretaceous
Accretionary Flysch and Melange Terrain along the Gulf of Alaska
Margin": u.s.G.s. Circular 751-B, P. 41-43.
Updike, R.G., Dearborn, L.L., Ulery, C.A., and Weir, J.L., 1984, "Guide
to the Engineering Geology of the Anchorage Area": Alaska Geological
Society.
u.s. Army Corps of Engineers, 1985, "HTC-1 Flood Hydrograph Package"
users Manual.
u.s. Department of Agriculture, Forest Service Region 10, Juneau, Alaska
"Water Resources Atlas," 1979.
u.s. Department of commerce, Environmental Science Services
Administration. "The Prince William Sound, Alaska, Earthquake of
1964 and Aftershocks." Vol. 1, u.s. Government Printing Office,
Washington, D.c., 1966.
u.s. Department of Commerce, Weather Bureau, 1963, "Probable Maximum
Precipitation and Rainfall-Frequency Data forAlaska": TP No. 47.
18
• • • II 'II. II Ill • --• .. -• ---WI'.._ ---
TABLE 1
ARCTIC
ALASKA CLIMATE CENTER
ENVIRONMENTAL INFQRMATIOR A~D DATA CENTER, UNIVERSITY OF ALASKA
t~~AT¥86E 60 4N
147 59W
CLIMATOLOGICAL SUMMARY
MEANS AND EXTRERES FOR PERIOD 1975•1979 CRAB BAY
ELEVATION 70 FEET
----·-----------------------------------------------------·------------------------------------------------------------------· I T E M P E R A T U R E 10 E G • F I I P R E C I P I T A T I 0 N T 0 T A L S C I N C H E 51 1
·---------------·---------------------·---------------·------·-----·--·-----·--·--·--------------------------·----------·· MEANS I EXTREMES I MEAN NUMBER : MEAN ;~REATIYRIGRjATIYRIDAI SNOW, SLEET IMEAN • OAYSI
I : OF UAYS : :MONTH: :OA LYI I I l I •-----•----•·---•-···•--•-·•····•·-~-•-------•-------• Z I I ; 1 •••••••·····•··•·····•··•··•·-·•···•···• I OLY I DLY: MO : REtiYRIOYI RECITR:OY: MAX I MIN I : : : : I I HEANl MAX :YR:GREATIYRIDA:o1Dio50:1.01
: ~AX : MIN: : ~I : : : Low: : •···•···•···•··-• : : I I : : :MONTH; :DEPTH: : : • : • : • : : : : : : : : : : : 70•: 32•: 32-: 0·: : : : : I : I : : : : : : : :
MO
----·-----·----·----·-··-·--·--··---·--·--·---·---·---·---·------·-----·--·-----·--·--·-----·-----·--·-----·--·--·---·---·---· JAN I 35o3 27o1 3lo21 44• 77 25-0 75 011 0 7 22 0 l6o04 29o55 77 3o31 77 04: 26o8 5lo0 79 60o0 79 30 16 12 7:
: : I l
35o2 24o0 29o61 46 77 04 • 9+ 79 101 0 8 24 . 0 15o26 26o82 77 3e10 77 011 40o6 116o0 75 60o0 79 28 16 10 51
I I : I MAR : 37o8 25o7 3lo81 51 75 28 10 75 22: 0 2 26 0 l2o26 17o34 78 2o65 78 12: 40 0 7 63o0 77 7lo0 76 31 17 11 4:
I I I : I APR : 43o5 29o0 36o31 59• 76 29 10 76 06: 0 0 23 0 l0o89 16o17 76 2o86 76 261 17o2 3lo0 75 74o0 76 05 14 8 4:
: . I I I
MAT I 48o8 34.9 4lo81 67 78 21 25+ 77 11 0 0 9 0 12o71 16o75 78 2.62 78 071 60 0 0 75 01 18 9
I I I
JUN I 57o1 42o0 49o6 73+ 77 30 32 77 03 0 0 0 0 3o72 4o35 78 1o36 77 171 9 3
I I
JUL I 62o7 47o3 55o0 81 75 08 41 76 06 5 0 0 · 0 3o63 6o74 78 Oo75 77 231 7 1
FE IS
.
5j
0
0
AUG i 63o2 47 0 7 55.5 79+ 77 21 18• 77 31 3 0 1 0 8.67 11.11 76 2 0 65 77 081 12 6
l I I SE~ I 57o1 43ol 50ol 68+ 77 02 31 76 29 0 0 0 01 1Ro81 31o42 76 3o70 78 141 18 12 8
• I f QCl i 46o6 35.0 40o8 '&• 77 05 13+ 76 28 0 1 11 o: 26o34 36o14 77 5o57 78 08. 8o6 18o0 76 11o0 76 30 23 14 10 . • I • ~OV j 37o7 27.3 32o5 504 76 13 15• 77 251 0 3 25 0: 16.61 42.11 76 5o73 76 30i 18o5 40e0 75 22.0 75 15 16 10
I I I I I
DEC l 33o4 24o1 Z8o8 43+ 76 25· 5 75 06l 0 10 27 0: 15o52 21o56 78 1o95 76 111 44o0 56e0 75 38o0 78 27 22
: I : : •
4
7
9 4
----·---------------·---·----·------------·---------------·---------------------------·--------------------------·-----------· · JUL JAN NOV NOV FEB APR
YEAR 46o6 34o0 40~3: 81 ~5 08 0 75 011 8 31 168 01160o46 42o11 76 5 0 73 76 761196 0 5 116 0 0 75 74.0 76 051188 105 58 .
-
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'". ,!'i--~~,-•• .. : .. · ..... '. '" . -. -· ~ i
-
SEWARD (A-3) QUADRANGLE
t 0 t
eiie-------SCALE -UIL£8
2 a
......
31
·.
Alaska
Crab Bay Dam No. 4
Evans Island, Alaska
LOCA TJON. & VICINITY MAP
April, 1986 A-216
FIG. 1 SHANNON A WILSON, INC.
Geotechnlul COiliiUitantl
I
I
I
I
I
I
I
I
I
I
I
I
r
I
------------·-· --
U. S. o.pa.._nt of Heahh 8 H~man Suvic:ll
Public Heahh S.mce
Indian Heahh s.Mce
CHENEGA BAY, ALASKA
PUIOC LAW ... 121 PIOIICJ
PIOJICJ NO. ....,.,..
-'
.. _ ... -.......... .
U. S. Departmenl of Heallh 8 t+Jman SUvica
l'llblic Heahh Service
Indian Heallh Senice
CHENEGA BAY, ALASKA ....... ,.,,.
I'IJIUC LAW e.121 PIOJlCT
...an-
0·1
011 ,
• • • • •
I
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~ • .-•towooo-
COUII.I r a I
ELEVATION
!VIEWED FROM DOWN STREAM FACEJ
., •• ITllt.. tox --
WILID
ltl[l II'LAPI WAU. --..
PLACa LAIG« lOCKS ______.-·
FOil Sf'\.ASM PAD
11:• TUal:
w;• LON.
1!" FLA•if---
~ ... ,.
-ULMIIOT -,.,.Q..d!TY
4• I t•
-----Qf'f:IOING
PLAN VIEW
sc.ou· •·. r
-----qy COCIIIETI' liTO CIIIZI< OUooML ,.-... ...... _,0 -""TDIW.
+---sTEEL ti<ANIII:L ITYI'I
,..,
, ..
I
,.. .....• ,~ ...... lt<llll
U.t.. -MU D '"*"I
-, ...
.... ~-'RI T' C.Offi.OCII
'• .... '"" "--v ... zoiTI:Il.'" -r-..............
SECTION
~ I"•C'
CAT WALK FOUNDATION
_ ... _
I I II ~OU811
CUT 11'11Utlt
CAT WALK
u. s. Oeportmeftt of Heoltll a H!.tman Services
l'loblic Ktoltll s.mc.
Indian Heoltll Senic:a
CHENEGA BAY, ALASKA
l"" -........ IU'o'ATIQIC .... JKTIQIC
I'UIUC LAW 111-IJI NOJECT
--C-4
:J.N.IITATION fACil.ITlU CONSTIUCTIOH llllAHOt
[INIIIONW£NTAL HUI..nt IRAHCH
41A.&JCA UU II All ..... M.Aol.ft ..a ..:a --. ...........
···--~-........
FIG. 3
• •• •
~$.
:.-.··oanaw'
a 0 I 10 ------------..
#'1. •• ·~
. . ... : .. .l ..
~ .. . ..
1
~··:· •..
. .
: ; .
pt Bazil-
I
l
8 -..... _ ,.,.,.. ............ ·~ .... " .... ~ .. --.......... -. ...... ::, ...................... ~-
GJ -.......... ,._ __ _
= ;.. .:.·=~.:=:-= --
• ............
Crab Bay Dam No. 4
Evans Island, Alaska
GEOLOGIC MAP
Ap r I I , 1986 A-216-
SHANNON & WILSON, INC.
Geotechnicel Conauhents FIG. 4 ~
!
I
• • Iii.-.
,
. ....
i!>,~
~'~
(j) m
0 r-
0
(j)
0
en m
-4
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: : : ~· ... : : ·. : : : : : :-.. ;-.: ·. ·. : "::: : . , ~"'"~" ~· .. A . . . . . . . . . . .. . . . . r:I''IJ~~
.. : : .... : :-. : .. ·. . . . . ~' •I ... ..,.. .K s ... • • • • • . rr.":;1 .O':JII"); . .# ,r
•.•• ::: .•. ·~· l::::;,::j -v-. ·~ y·-'~'qyt.J~:I-<c-" ~ Ba ... D a 9';~<c• /i
Ccnlnental Cruat
North Amartcan Plate
10~ 20 .eo 80 Mlea
~ I
Hortzcntaland Vertical Scale -. .
-oltoOvwtylng . . .fl' ~ Fano.An; Tronch 8,_.-. ;,-:/ Depo•~• . ~
Ocean Bat*\ Depoelta
llliffi} Ocearic Cruat
c=J . Paclftc Plate
Generalized block diagram illustrating the geologic characteristics
of the sudduction. zone beneath sou them Alaska
•
...
----··· Fa~ dott&d Where ccnceelacs"-
.. UK:atlan of. eartquake epbjnter8 With Ria~· of e.O:
and SJ'e&ter OCCUTing from "189& to i&74 -· . · -· '
~j8.5
7.5
8.0
8.5
. .:· ...
UaCJlltude Scale
CD --en __..._ __ -:-------~ ...
~·o ·
0 .J .
Crab Bay Dam No. 4
E~ans Island, Alaska
SEISMICITY MAP
Ap.ri 1 . 1986
SHANNON • WILSON. INC.
Geotechnlul ConiUitantl
... ,._., .....
....
0
Cll
• • • •
• • •
• a
• • • • •
Appendix A
Photographs of Dam
Taken September 23, 1985
1. UPSTREAM FACE
2. DOWNSTREAM FACE
A-1 SHANNON a WILION. INC.
Geotechnicel Con1Uit8fttl
•
·~ 'J~
• • • • •
~
• •
=I
~
·------· .. ··~--..... .,... ~~~,==--------
3. DOWNSTREAM CHANNEL AND WATER SUPPLY LINE
SHANNON & WILSON , INC.
•
4. RESERVOIR
• •
SHANNON 8o WILSON. INC.
Geotechnical Conaultenta A-3
• • • •
I
-
I
I
I
.Appendix B
'Corps of Engineers
Inventory Forms &
Visual Inspection Checklist
r • •
PART I -INVENTORY OF DAMS IN THE UI·UTEO STATES Rill (PURSUANT TO PUBl.IC l.AI' 92-)67)
S.o rovetltt aide lor inslructiona.
Ill 131 141 lSI 161 171 (I) 191
DIVISION COUHTY N.ul!
FORM ...,.I'~OV£0
OMI NO. 4,_110421
REOUIIIEMENTS CONTROl SYMIOL
DADI-CWE-17
ItO)
L.t.TITUO£
(Nottll)
(Ill
LONC<ITUO£
(ll't>af)
Ill .. IDENTITY ...
"( .. NU .. IIER
"' I jl J,.,,,.,,
A\K Ill\
[Ill
REPORT DATE
IDEHTifiCATIOH I I 1J j'J _j.j J vw\ ~ \ \"'w I --·'----L-\ ... .1~ ...... 1-~--i ... t 1 l t:J I 0 •• •• 00 U -·'--1--1--1--lui-.LLLLLJ .. LLLLI .Li. LLL .I J I LL\ ' I j I ' I -l' J• •! ••• I •n I I - 1 . i ~ ... L_L_ ... L.L _ .. C. uL~L-i __ L. __
lUI ll4J
POPULAR H.t.ll( N ..... £ Of IMf'OUNOilENT
IO~~~~~~~:~~QH I_ 1-I u.l .. f. .. I ... 1, .. l.,.f,., 1~ .. 1 ,,..[ ,.,.) ::J ..,J,.,.j'\,.1 ,._..hO ... ful•~l '!>&I'MIII :J ... 1.-.l,nJ .. J ,Jv;(.,.J._J-1~1. o L.J .. Ju (_..Ja..r. l.ni .. aJ.u.J IU\lc of-.J._,J,. .. J • .Juinlc.. la.6J..,_,...f: o C ,.J., -al.c .. laa.l.ul.c.,l.._.[U,i .. ,.J,..h,.l,..l,..l._,.j ... ,.Jnf .... I ..... L:J
IISJ 1161 ll7J
IIIVER OR $Til! All
LOCATI~
Ill) (2ll (231 12-'l 125)
nATISTICS
REIURU
ENG 1 ~~~ n 4474
Ill I
NE.t.IIUT OOWHSTIIEAil
CITY • TOWH • VtL.LAC<!
(261 1171 (27AJ
IMI'OUNDING CAI'.t.Ct TIU
111)
IUMARU
,._,IMII .... flllllll
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!:, !:.~,:: ll7FJ
1191
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(MU)
1101
I'OI'ULUION
•
-----... -• • • • • • • • • • w·:•
STATISTICS
MISC. DATA.
MISC. DATA
fCOfttiftut'd)
MISC. DATA.
(ContiftUt'd)
REMARKS
f(IIIM
lNQ t OIC n
w PART II -INVENTORY OF DAMS IH THE UNITED STATES
(l'fJIISViJIT 70 PfJBUC LAW P2-:J67}
(19) llO) (31) (31)
.. ..
"
(33)
"II.LWAY
(46)
(49)
s .. ,.,..,. .. aid. lor inatnt<:li..,a.
(34)
VOLUME OP DAM
.(CY)
(SO)
(35] (36] (37) (31) (39)
P'OWU CArACITY
(47}
IMGINIUIMG 8Y
(St)
(40)
111 ..
1'0111111 AI'I'IIOVID .. ID!IITITY
<( IIUIIIII!II OIIIIIINO • ........:t1 .. ...
lllOUIIIBIENTI CONTIIOI. l'fMIQ. • lz •l•l•I•T'
DAEN~l-17 I 1 n1
(41 J (41) (43) (44] (4SI
NAVIGATION LDCU
(41)
CDNSTIIUCTION IY
(Sl)
I ---~
'""'·-··-·· I --···--··--·---I I ---·-·-1 ... ~···--.. ·-·--{~· ;,:
(53) (54] (SS)
.:
IN$1'l!CTION aY AUTMOIIITY 1'011 INSI'ICTIOM ··: "':.··
InventorY No. N/A
Sheet _1__ of __s__
VISUAL INSPECTION CHECXLIST
1.
2.
).
4.
s.
Name of Dam: Crab Bay Dam #4
Inventory No.: Non-Jurisdictional
Hazard Category: Low
Size Classification:Small
Owner: Chenega Native Association
Evans Island, Alaska
Gail Evanoff (907)573-5114
Chuck Totenosf (907)573-5111
6. Date Inspected: 9-23-85
7. Pool Elevation: 252 Feet
8. Tailvater Elevation: 250 Feet (app1
9. Purpose of Dam: Water Supply
10. Veather:cool & Cloudy, 550F
Directions: Hark an ·x· in the ·yEs· or ·No· column.
If item does not apply, vrite ·N/A• in iREHARKs· column.
Use •other Comments• space to amplify ~EMARXs·.
ITEM YES NO REMARKS
RESERVOIR
1. Any Upstream Development? ~i.;:~;r Inventory No.:
2. Any Upstream Impoundments?
3. Shoreline Slide Potential? f-~X;t,. Minor rock soalJina
4. Significant Sedimentation? ~~.'~?:f. Some J eaves & branch~s
S. Anv Trash Boolll?
6. Any Ice Boom?
7. Operating Procedure Changes?
~ ~DOU--~N~S~~~~-C~~~~~---------------------r----~----~----------------------------1
1. CHANNEL
a. Eroding or Backcutting?
b. Sloughing?
c. Obstructions?
d. Bridging?
2. DOWNSTREAM FLOODPLAIN
a. Occupied Housing?
b. Farminst?
c. Recreation Areas?
d. Changed Hazard Potential?
e. Nev Developmenc? X ~ • .;,.t;"f Bui 1 t in con iunct ion with dam
INSTRUMENTATION None
1. Are there ir;t'J-A~}
a. Pi e:r:ometers? ~~
b. Weirs? 4~!
Co Settlement Pine? ~~
d. Observation Yells? l~*.$
e. Other? -~~
2. Are readings
•· Available? 1-7~~""7
b. Plotted? ,J.Y;~~
C• Taken Periodicall_y? ;.tn:·;r
•• • • • •
•
ITEM
CONCRETE DAMS
1. CREST
a. Any Settlement?
b. Any Misalignment?
e. Any Crac:ldng?
d. Any Deterioration?
e. Exposed Reinforcement?
f. Adequate Freeboard?
2. UPSTREAM FACE
•• Spa lUnd
b. Cracking?
c. Erosion?
d. De terloration?
e. Exposed Reinforeement 1
f. Displacements?
It· Loss of Joint Fillers?
h. Silt Depoait Upstream?
3. DOUNSTREAH FACE
a. Soallintr'!'
b • CracltinR?
c. Erosion'
d. Deterioration?
e. F__rno~ed Rt!lnforcement?
f lnsn.,.r-tinn Gallerv?
p l"nnnA.,.tlon Dr a ins"
h t:,., ''"'"'"tfon Drains Flov!ntr?
f_ c:,.,.nJia,. frnm .Tnfnt~' .. c: ... ,.n.ailll frnfft f.f ft T.f 011"!11'
4 ..tR '-llnJIN ~l,.TON r.ON"""A~ .. 'F'rnn•,.A J\pdrnr1r1'
b 'P'rn .. tnn'P
r Vf c.-hl,. ni •n, .... .., • .,,..!1.,
d ~,.,.nJ1117f! frmfl Contllct'~ ,. Rofl!'l nr SnrfniP!I Dovn~t:re.!uzt'~
• • • • • •
Other Comm~ta: Dam is in exce 11 en t cond i t ion
lnweniCHy Ho. ---"N...._/"'A,__ ___ _
ShHt __ 2....___ or 5
YES NO IIIEMAIIIKS
TYPE: Buttr~c;c;
tql lnnn 1 1 wiliP
,.,.--:;,.~f.il---
·=·~·"'.;'!
~~~+-··
.;:.;~~
··~-~~~.~
;·~-t.··i.·-: Fetch: Az:
;.~'"'
~:w~
~it~t.;t•
~~~H;·
..~.,Nt-·-.
,~_.-"'
;ot.~~
~~:;·· ..;, ••• lro. ....
!:~-~~~ fl.,.c:;,innaM fnr n .. rinnir fl 1<:h'nn
·~
~~f>l
~~~
tO~,-'
.~·~~~
~ji~:
k.'iHiili!~ X
~,.;·'t'::f:? l{
X
!;:'-~.x;··~
''il'~~:·
!'..j:;ii,.:,.
.~·.<+~.
.£i~-"
;.::.:::t ~·
£~ ... ~
,
• • • • • •
I
' ' •
. .
lnwentory No. _...:..N;..;../,;.,;A _____ _
ShMI ---~3 __ ot~5'----
rnu YES NO REMARKS
SPILLYAYS TYPE• Direct _Overflow throuah
Weir
}. CREST TYPF.: Wood o lanks
a. Any Settlemen~:s? r..+:'.~:':'-:'
b. Any Hisalbnments? "•l rl'; • t"' ·~"
r:. Anv Crack!ntr? 1~·': !.:::'
d. AllY Deterioration? ~~ ~~.:
e. fxoosed Reinforcement" ~~ t-:"...-!0
f Rrosfon" ~~~
2 Sill" DP.noa!r: flnAt:'rf>am't :l*ttt·
2 s ]{U!.. ultl!:S TYPE: Fho;.hhn~rnJIO.
Jill He~hani t':lll F.tmi nment Onerable" ~;';m NonP
b. Ar_e_ Gatf>s Maintained?
... t ,-. ... -..
t!. Will Flashboards Trio Automat!call Y1 ~~~ X
d. Are Sl:anc:hfon§ Triooable" ~~;,
e Ar,. t':JJ~t"P!I RemotelY Controlled" X
] CH rrl': TYPE: Non,.-flj rPrt" 0\ll:~rfl,.,.,
a AnY CrJ111"1cfnp'P ~~1~"'
b. AnY' Deterioration" ~~~':i;.
t'. Ero!l!on" '~~"'""
d fxoosed Refnfn •n,.., ~~::¥ -,c::,.,.nl!IO>fll ar t.ff"r T.inf>ll or Jotnt:s't ~·~4'~
4 FNFRCY Of'\1\TPATOR'C:: TYPE: None Direct discharoe in .. Anv J"lpr,.r1 nr• rf nn't ~·.&:~~ channel
h Frn•fnn't ~~
t! F:rnn!IIPd Rf'fnf', lt" ~~';::
lj MFTAJ. APPfrR"rF'NAN~~ None
• CP--· t f L'tft., ;~;
h, 'Rl"fOAk~O>III>'P ~~'-'
#" S~nrl'! An ... '---,-. ... 't :~.w>l-"'.;
" ~"',..,.NCY SPif fUAV TYPE: Nnn ...
Jl .Lt............ r.r.. .... -., W:\~~~!;•
h. r, ................ ..,. • .-h t'"h.-nn .. 1'f ~4.~-~·jf
t" . Frnd1hlfll tlnun•rr~AIIt rh,.nn"'!lf ,~, .. .;:, .. ~ .. ..,...tfhla 'IP!.••• 'Plu•f ~~~.!·~
.. StAble SfAa Sll'll.,.,..'t t~ .. ~:::;
. . .
lnYentory No. _:.,:;NI:....:A:,.:.._ _____ _
Sheet __ 4...___ ol __ 5 __
ITEM YES NO REMARKS
LOU LEVEL OUTLET TYPE: Stee I pipe with shear Qate
1. CATES
a. Hechanlcal Equ1P12JeRt Operable? ~r.:~~"":~:'
b. Are Cates Remotely Controlled 7 X
C• Are Cates Maintained? ,, t·~· ·, New
2. CONCRETE CONDUITS N/A
a. Any Crackina-! ~:z~~~~ ~·,.
b. Any Deterioration 7 ~..:_~$~--~"#
C• Erosion? !"::~-,_,
d. Exposed Re !nforcing? ~'\;~\.'.'·
e. Are .Joints Displaced? ~~~~~--
f. Are .Joints l.eakin2? -!:?~2::
3. METAL CONDUITS 12 11 oioe -36 11 lono
•• Is Metal Corroded? ··:.-x . ~-·.h New
b. Is Conduit Cracked"" ~~;x .. ~.
c. Are .Joints O!solaced? ~'\:.1(.:::-
d. Are .Joints Leakin~r? '·~-~v~.
4 !:.l't ~1\.Gi' DISSIPATORS NonP
a Anv Deterioration"" ~~~:£~:!'
b • .Erosion"" ~~:i
c Exoosed Refnfo '"!Rt"l' ~~.(· ....
5. METAL A.I:".I:"UKl.r;NANCES Shear gate -Whee) has been
a. Corrosion" · -i"'X· 'i: • removed probably to prevent
b Br!!!!aka2e' 11>,;,"i'X .• unauthorized operation.
c Serttre Anl"hnra£elll"l' iJ'.;'K:r~·
Other Comments:
•
•
• •
JTEM
INTAKES
1. EQUIPMENT
a. Trash Racks?
b. Trash Rake?
c. Mechanical Equipment Operable?
d • Intake Cates?
e. Are Racks and Cates Maintained?
f. Are Cate Operators Operable?
2. CONCRETE SURFACES
a. Any Crackina?
b. Any Deterioration?
C• Erosion?
d. Ex nosed Reinforcement?
e. Are Joints Displaced?
f. Are Joints Leakina?
3. CONCRETE CONDUITS
a. Any Crackin2?
b. Any De terior a cion?
c. Erosion?
d • Ex nosed Reinforcement?
e. Are Joints Displaced?
f. Are Joints Leakind
4. METAL CONDUITS
.11. Is Ker:al Corroded?
b. Is Conduit Cracked?
c. Are Joints D1 solaced?
d. Art!! Joints Leakin2!
5. KETAL APPl"""'"",., .. 'NCES
a. Corrosion?
b • Breakape'7
t"' ~f>rnrtl!. An~hor.1UP't!!S.,
6 PENSTt'lr.JrC:
a. Material Deteriorated?
b. Jolnr:s Lea1cintr?
~. Sunoorr:s Adeauate?
d. Anchor Blocks Stable"
lnwentory No. ---'-'N.L../.._,A _____ _
ShHI 5 oi_S"---
YES NO REMARKS
\Jp)) ~rr&> .. n ~ P'n'nn
X
X
"';':":X,£: Valves
X
-~~~::.;t _Hew_
~·~· ,........ 'f ··.··"" ~ .
~nnP
~~:#:):~}
t~~.·~t~::
~·'*' ~~-r
~~A~::
·;·*~~:;,_
lllr-n.c
~'ti~~-C~
~~~~
~~lir"l;::~~··
-~l~~:Y.:··i
S'fi.~;~.
::-;;_~!+"·'..:
~~·~,
·~t~:
~1(k-''
}A~~·)·,
ii$.~.pif-:
t'"~-yX-;
:)t-.)r,:'!'{:
TYPE !iATERIAL: Arctic Pioe
")':"~~x~~·-=
-~ix. ·
;tt"?X !.i
-~;~,~~~i • • • Other Comments: Dam is new (constructed in 198~) by the Public Health Service. It was
constructed of concrete tied into slate rock abutments on both sides .
Appears to be in excellent condition . • •
• • • • • •
II
APPENDIX C
HYDRAULIC ANALYSES
COMPUTER OUTPUT
• •
• •
• •
• •
• •
I.
I
..
I .
---IC -IC '« -IC -IC -« -IC
-t( -IC
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-«: ... -IC
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-« w ~ E -IC
-t( C)-I .... -t(
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X :X
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X .X xxxxx
X _, X
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~ ~ I~ x><xxxxx
xxxxxxx
X I
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X I xxxxxxx
. ' I
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SUI111AkY 01:' IJAH O'JERtOPfi 1Nil7TiiEACH ANAL 'I'S IS FOR STATION [tAli
AN 1 ............... --------·-ELEVA! !UN
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DEPTH STORAGE
OVER DAH At:-l'T
. ---&-.00 . . . ... o-.
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DURATION !111~ U~ Tli1E OP
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••
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HEC-1 INPUT PAGE
tli'II: .ID •.......• 1 ........ ~, •••••• J ••••••• 4 ••••••• ::> ........ 6 ••••••• 7 •....... ~J ........ ~ ........ 10
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l ., ...
Ill
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ID
KEHAl ~~NNlN~ULA ~b79.0
DAM SAFETY ANALYSIS
'3
~
5
I~
IT
Ill
Jk
s
5
I:'LUW
., Ia{ INFLOW
a ·-···---£lA-o.a?-
g 8F -1.0
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11 · -·LU 0. 5
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·13-· .... --
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15
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17
18
19
20
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1(0 5
RS 1
SV 0.06
St 247.7
ss 24tJ.O
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ANALY~l~ U~ CkA~ ~AY UAM Nu. t
0 0 300
• :10 . --.. S~ • 50 .~;::.
lNFLO~ TO CRA9 SAY DAM NO. A
-.O::i
1.0
.1
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2.0
0 NU
CRAB·&AY··llAH NO.4-
I: LEV 24?.?
0.14 ·--0.20
2:):.! 255
4.0 3.0 1.5
14.5 a.o 1.5
66
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-----------------
75 100
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KM ~OIJTI:i OUTFI.OW !'JWH RESERVOIR TO CREBI( I!>T -VII.l.:IAGS· ·----··--· ·-·------· -----·-· --·--------
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PEAK FLOW AND STA~E <END-OF-PE~IOD> SU~MARY FOR MULtiPLE PLAN-~ATIO ECONOMIC COMPUTATIONS
FLOWS IN CUBIC FtET PER SECOND, AREA IN SQUARE MILES
OPERATION STATION
... ----·. ---·
HYDROGRAP'H AT INFLOW
JcOUTtD TO DAH
-·' ·---·--· -·
ROUTED TO RCH1
• ······--··-··-·-TIH!··tO PEAK IN HOURS ·--·---·-------------------
RATIOS APP~IED TO FLOWS -~ ---····----
AREA f>LAN RATIO 1 RAllO ~
0.20 0.3::, __ .... _ ... _, _______ .. _ .. _
0.37 1 FLOW . ·n. l:J::i.
'II HE l6.btl lE>.~l'
0,37 1 fLUW ·n. 13:).
TIME 16.::.11 lE>.::Sl! -------·----..
0.31
i
AA PEAK STAGES !H FEET A*
1 STAU£. 251.4:i
---TIME 16.~8
1 fLOW 'l7.
·-:r I"z:----·--te ;e:t
252.56
1G.::it3
1::4.
. 16•6?-
AA PEAK STAGES IN F££I *A
1 STAtiE ·15.92 16.2<.1
TIME. 1&.67 16.67
RA!IO 3 RATIO 4 RATIO 5 RATIO (;
o.::.o 0.6:.. o.uo l.OO
~~~. ;.!:)0, ;30:.1. 385.
16.5(; 1Eo.5t: 16.!:.tf 16.513
. ·~·-. -. -
1'3;.1. ~~0. JO:.J. 395.
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KENAI PE~NIN3ULA 46?9.0
DAM SA~ETY ANALYSIS
ANALY~IS Of CRAD BAY DAM NO. 4
5 10 OUTPUT CONTROL VARIA~LES
···-·-· -----tPI<NT · ·-· ·· -5-PklHt -i:€1NTkOL
IPLOT 0 PLOT CONtROL
QSCAL O. HYVkOOkA~H ~LOT S~ALE
l! HYDROORAPH TIME PATA
NMIN ~ KlNUT~~ lN COM~UTATION INTERVAL
----·IDIITE-------1 ---0·-STt\Rt-l~Q ·IIAH--· ·
ITIHE 0000 tTAMliNU TIME
NQ 300 NUH&ER OF HYDROGRAPH ORDINATE~
HD~ATE 2· 0 ·ENUlNI DATE (
NDTIME 0055 .tNDING TIMt I
---· --·----·--··CUHI"UT"A'l' lON-·INT UVAL -....,....-c)-M)8-+IOUR-S -!
TOTAL TIME BASt 24.92 HOURS I.
f
I
I
ENrJL IS I+ tiN H'~ · · · -
DRAINAij£ AREA SQUARE MlLES
PRECIPITATION DEPTH INCHES
·--···------t£Na!H-;--!t;!Yt\tlOH ····FEET-------··---...:::::
. FLOW CUBIC FEET PER SECONP
STOkAGE VOLUME ACkE-FEET
--· SURf'~f AlE A ACRES -· ·· ··
TEMPEkATUk£ D~Ok~ES FAHR~NHEIT 1
JP ·----MUI;H-PCAN ·GPTi:OH---·-·---· -----· · --
NPLAN 1 NUHlll::k 01' !'LMIS
JR----------·MUi.t·f-RAHO DPTIDtol
. 14 I{Q
RATIO~ Of RUNOFF
0.20 0.35 0.50 0.6~ o.eo ·---------------··----··--. ··-------·-----....... .
OUTPUT CONTROL VARIA~LES
I~RNT 5
· ·· · -IPI,OT 0
QSCAL O.
I'RlNT CONTROL
PLOt-CONTROL
HYVkO~kA~H ~LOT StALE
1.00
-···
*.H WARN INI.J··***-MOM:HED ~I:ILS R9l!TING KAY -BE NUHSR--lGALI.Y · UN:>IA9L.IO EOR UUtJ:t.~W~~tWa:::N ~ilU" tO ;n, iQi •
/ ·-----
THE ROUTED HYDROGRAPH SHOULD PE EXAMINED FOR OSCILLATIONS UR OUTFLOWS GREATER THAN PEAK INFLOWS.
THIS CAN BE CORRECTED ~y DECREABINO THE TI"E INTERVAL OR INC~EASING S~ORAGE (USE A LONGER REACH.> --. ----~· ·------·------
CANYON INDUSTRIES, INC.
SPECIALIZING IN SMALL WATER WHEELS
October 9, 1987
Mr. Jack Goldwausser
Mountain Energy, Inc.
P. 0. Box 421
Cave Junction, OR 97523
Dear Jack,
5346 Mosquito lake Rood
DEMING, WASHINGTON 98244
(206) 592-5552 or (206) 592-2235
Thanks for the call on Wednesday, and for the opportunity to offer prices
on equipment for your Evan's Island Project. Based on a design flow of 3
CFS at 180 feet effective head, we would recommend a double needle nozzle
Pelton type turbine. With such a low head we'll need to use a belt drive
speed increaser from turbine speed of 800+ RPM to the 1800 RPM synchronous
generator speed.
We've included turbine, double needle nozzles, inlet bifurcation, KATO 1800
RPM generator, voltage regulator, and hydraulic system in the budget estimate
of $24,700.00. If you prefer single phase generation, there will be an additional
cost of $700.00 for the generator.
Hope this is adequate information at this time, and I'll look forward to
discussing the project with you.
Si•u:·
Daniel A. New
DAN/mm