HomeMy WebLinkAboutNew Chenega Village Hydroelectric Retrofit Proposal 1987NEW
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Alaska laergy Authority
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New Chenega Village
Hydroelectric Retrofit
Pro osal
DATE
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NEW CHENEGA Vlu.AGE
HYDROELECTRIC RETROFIT
PROPOSAL
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Mountain Energy, Inc.
New Chenega Village Hydroelectric Retrofit Proposal: October 1987
The following report will detail a proposal to retrofit a
hydroelectric generating facility to the existing water supply
system presently servicing New Chenega Village, Evans Island,
Alaska. This proposal is based on observations made during a
visit to the site September 9 and 10, 1987 and follow-up studies
based on data received from various sources which deal with
available water, the engineering of the present diversion dam and
other topics (see appendix). It is the conclusion of Mt. Energy,
Inc. that there exists sufficient energy potential in Anderson
Creek coupled with the existence of a good diversion in place to
warrant a retrofit with hydroelectric equipment and that the
energy derived from such a system will provide substantial relief
for the Village from expensive and potentially unreliable diesel
power.
This proposal is divided into five
decision to retrofit the present water
generating equipment: 1) field data,
economic analysis, 4) construction,
topics will be discussed in the body of
topics which impact the
system with hydroelectric
2) design and cost, 3)
5) agency issues. These
this proposal.
Three assumptions were made prior to developing this report: 1)
the head available to the project will be the differential
between the present diversion and the water treatment facility,
2) that the environmental concerns which may impact agency
approval vis a vis the project reach will not b~ an impediment
to proceeding with the job, and 3) that the hydro system will
operate as the backbone of electrical production for the Village
with additional power supplied, as needed, by auxiliary diesel
power plants.
-2-
Field Data
The following discussion will focus on aspects of the project
already in place and water data already in hand.
The present diversion is located approximately 250 ft. above sea
level and 180 ft. above a water treatment facility adjacent to
which the powerhouse would be located. The diversion is accessed
by a serviceable road, the probable penstock route, which has
held up very well over the years. The concrete and steel
diversion is approximately 20 ft. wide by 6 ft. tall by one foot
thick and is well situated between and embedded into rock walls
on both sides of the relatively narrow creek channel. After a few
years of service, it appears the dam is holding very well (see
Inspection and Safety Report on Crab Bay Dam No. 4, Evans Island,
by Shannon & Wilson et al (1966), engineers).
A discussion was held with the engineer of the present diversion,
Mr. Crum of the Alaska Public Health Service, to determine his
views on the possible retrofit as well as any potential impacts a
hydro system may have on New Chenega's water supply system. It is
fair to say that he saw no issues of concern vis a vis a hydro
retrofit as long as neither the integrity of the dam nor its
primary function, the intake of water for the village, was
negatively impacted. Proper concern for these issues will be made
and pose no problem for the proposed project. Mr. Crum suggested
several issues which should be of concern in designing the
retrofit which will be discussed under Design and Construction
sections of this proposal.
The diversion is presently fitted with a 12" steel sluice pipe
designed to help clean the small reservoir of debris and provide
added high water relief for the diversion. This pipe can be
adapted to accommodate a penstock for the hydro retrofit. The
present pipeline, used for water delivery, is located on the
opposite side of the creek from where the hydro penstock would be
located and will pose no problem vis a vis locating another pipe.
All in all, the present system is extremely well suited for its
present application and is certainly "stout'' enough to warrant
adaptation for hydroelectric purposes.
Evans Island receives approximately 160 inches of annual
rainfall, a relatively large amount. Much of the rainfall is
distributed over the traditional heavy flow months for the area,
May through December, but significant rainfall occurs in all
months. While no systematic hydrological study has been
commissioned to precisely determine average daily flows, there
are two currently available sources of hydrological data which
can be used to estimate potential energy production; a Public
-3-
Health Service hydrograph estimating water flows at the mouth of
Anderson Creek (see Annual Hydrograph at Mouth of Anderson Creek
in appendix), and estimated annual average flows over the
existing diversion developed by the engineering firm of Shannon &
Wilson et al (see appendix). Since the needs of the Village for
potable water are very modest (.02 cfs) and can be expected to
remain so, withdrawal for hydro will be the primary demand on
creek flows. Current design of the retrofit will require
preferential withdrawal for the Village water system. The issue
vis a vis detailed hydrological data is not whether a hydro
system will be productive or economical, since there is more than
enough data to support development of a system, but rather
exactly what size to design it. Sizing will be discussed under
Design.
Design and Cost
The design of the system at issue is fairly well determined by
the facts of the present water system installation. The diversion
is in, the road and probable penstock route is in, and the
location of the powerhouse seems apparent, next to the water
treatment facility which is also the terminus of the present
electrical distribution line and hence the best place to
interface the old and new generation equipment. Primary issues
involved in design are the modifications necessary at the
diversion to accommodate water withdrawals into the hydro system,
sizing and type of penstock, sizing and type of generation
equipment and controls, interface with present distribution
system, load management, and interface with diesel equipment.
The present diversion is equipped with a 12~ high water release
and sluice pipe. This can be readily adapted to accommodate water
withdrawals into the hydro system. A covered stilling chamber
will be built on the down stream side of the present diversion.
This chamber will be fitted with an intake structure for the
hydro penstock and will be fed by the present 12" sluice pipe.
The sluice function of the system will be maintained by creating
a "y" on the sluice pipe which will allow removal of silt or
small debris as the situation requires. The charging chamber will
be located so as to not block the present overflow notch in the
diversion, although stop boards will be fitted into the notch to
provide additional control of reservoir levels. This design will
have the benefit of not compromising the primary function of the
diversion, delivery of water to the village, in any way. That
function will be completed prtor to any waters being diverted to
hydro applications.
The stilling chamber will be fitted with a sensor which will
-4-
measure water levels in the chamber and report these levels to
the control module in the powerhouse thereby allowing for
modulation of flow at the turbine by means of a needle valve such
that water levels in the stilling chamber will not drop below the
level which guarantees proper intake into the system. This sensor
will be calibrated such that the head necessary over the intake
for the village water system will always be maintained at optimum
levels. Waters not necessary to either the water or hydro systems
will overflow the stilling chamber and return to the creek
channel.
A 10" steel pipe will carry water from the stilling chamber and
into the hydroelectric system. As soon as the penstock route
carries the pipe out of the creek area the penstock will change
to 10" PVC pipe which will be buried in the center or to one side
of the present access road and continue down to its terminus at
the powerhouse located next to the water treatment facility. The
pressure rating of the pipe will be graduated to accommodate
increased water pressures as the penstock goes down the hill.
Water will pass through the turbine system and continue back to
the stream area via buried culvert. At the point where penstock
waters are rejoined with those of the creek suitable anti-erosion
structures will be constructed to prevent any erosion of the
existing creek channel.
The hydrology available suggests that a withdrawal of 2-3 cfs
would be reasonable. At this level of withdrawal, the Village
could expect 22.5kw to 33.75kw. Assuming this level of
production, most of the Village's electrical requirements would
be served most of the time. In lieu of concise daily flow
measurements, it makes sense to size the plant to the larger size
and be prepared to "nozzle down'' as appropriate. This approach
would fit into the demand cycle of the Village which indicates at
least a 25% increase in electrical demand during Winter. The type
of turbine suitable for this project, impulse or more commonly
referred to as Pelton, has a very wide range of highly efficient
production over an enormous range of flows, consequently cutting
flow would not affect efficiency at lower flows. overall
efficiency at the turbine can be expected to be in the lower 80's
of the percentile range and will perform at that level from about
.5cfs to 3.5cfs. Turbine design at the larger size will not
materially affect project cost.
The control ''theory" which is employed in this system is that the
best use of stream flows diverted to electrical production is to
absolutely maximize the use of electrical power. That is, rather
than tailor production to need, i.e. reduce flows to the turbine
thereby cutting production as demand decreases or vice versa, the
system will run at the maximum output possible for any given flow
at any given time. The flow will be modulated only to guarantee
proper function in the penstock, not to control production.
Excess power, that which is not necessary to supply demand, will
-5-
be routed to heating facilities, an ice plant or whatever
electrically operated equipment that the Village would want and
which can be used on a standby basis. By using this type of
system maximum use will be derived from the equipment and it will
last longer.
Controls necessary for the system will require a primary control
package which will monitor aspects of electrical output and
provide relief should output parameters be exceeded, i.e. over
voltage etc., a flow control capability to bring the system in
balance with available water flows at the diversion, a minimum of
load management for the general "system to provide for use of
excess power during low demand situations, a variety of warning
devices to alert personnel if necessary, minimal load management
controls fitted to each building which will maximize hydro usage
and minimize diesel power requirements greatly, and
synchronization equipment necessary to "mix" hydro and diesel
generation equipment.
Interface of hydro generation with the present distribution
system will take place at the powerhouse located adjacent to the
water treatment facility. The interface will amount to switching
devices which allow disconnecting hydroelectric power in favor of
diesel should that become necessary for maintenance, repair or
low water.
There will be two load management systems required for the
system. The primary system will, in the most general of terms,
make a decision, at any given time, whether there is excess power
available, system-wide, to meet demand. Should excess power be
available, it will be directed to low priority, interruptible
loads. At times when demand increases, low priority loads will be
dropped in favor of the primary load: serving the needs of the
Village. This load management equipment will be located at the
powerhouse or any building where the low priority load(s) will be
used.
The second level of load management will be individual devices,
similar to the primary load management device discussed above,
located at each building where electricity is used. This
"manager" will have high and low priority loads wired such that
when the overall system approaches overload, as determined by
measuring current frequency, the low priority loads at each
station will be temporarily dropped. These ''drops" will continue
randomly throughout the Village as needed until overall demand
decreases, thereby reinstating power to the low priority loads,
or alarms will trigger the need for auxiliary diesel power. All
the decisions by all the controllers are being continuously made.
In most cases, changes in load distribution will never be
apparent to end users of electricity. This secondary level of
load management will be the key to minimizing diesel generation,
especially during high demand or low production.
-6-
The following budget was prepared based on estimates from
suppliers and previous hydroelectric installations. While this is
an estimated budget, Mt. Energy believes it represents a very
accurate picture of project costs and has a very high degree of
reliability.
Estimated Retrofit Budget
Item
Follow-up field observations and survey
Agency interface and permit preparation *
Engineering/design & supervision
Mobilization, equipment selection, and purchasing
Equipment transportation
Excavation & area preparation: Powerhouse,
penstock, diversion
Stilling chamber construction
Intake structure
Penstock, unit cost
Penstock installation
Valves, vacuum release, PVC to Steel,
pressure relief system
Water level sensor
Powerhouse: foundation, thrust wall,
12'xl5' steel building
Overhead crane
Turbine/Generator with flow control module
Hydraulic system (flow control)
Equipment installation
Powerhouse control panel
Transformers
Load management system
(powerhouse and 25 end-user units)
Diesel Interface
(transfer switch, "mixing" system)
Electrical installation (system-wide)
Construction Management-personnel transportation
Contingency (20%)
Contracting (15%)
Total
Cost
$4,000
1,000
6,000
1,500
4,500
2,000
2,300
750
11,528
1,500
1,350
3,000
6,000
2,500
25,400
1,350
1, 750
7,300
2,400
14,650
1,250
1,750
9,500
22,655
20,390
$156,323
'*This assumes 5 days office and field time with no particular
agency problems
This budget does not include provisions for us~ of excess
electricity at times when demand is less than production. It does
include the management system to allow for this possibility as
-7-
well as the ability to simply plug in whatever type of use may be
developed for interruptible power. i.e. an ice plant.
The control panel proposed is adaptable to automatic operation of
auxiliary diesel power should that be desired at a later time. It
is not recommended that automatic operation of auxiliary diesel
power be installed initially.
Economic Analysis
At present, diesel generated electricity is costing New Chenega
Village approximately $.50 per kilowatt hour (KWH) according to
Corps of Engineer estimates (1982). The development of a
hydroelectric facility as proposed above will allow the Village
to replace diesel generated electricity with hydroelectric which
will cost $.0153 per kwh assuming a 45% plant factor, 10%
financing at 20 years. If grants are utilized to fund the project,
per-kwh costs will be reduced to a ridiculously low level.
Obviously considerable savings will accrue by utilizing a
hydroelectric alternative to diesel. On a typical full production
day (24 hours at 30kw) the cost of generating electricity will be
approximately $11.00 at the hydro plant as opposed to $360.00
with diesel, using the Corps of Engineers data.
Typically, maintenance of hydroelectric facilities is very low. A
1% of installed cost per year maintenance budget should be
sufficient. If the maintenance budget were raised to 3% and
excess funds placed in a sinking fund for equipment replacement,
potential expenses long term would be properly managed.
The general economic life of facilities such as that proposed is
35-50 years, as far as lending institutions are concerned.
However, with proper maintenance the project can easily last as
long as anyone cares to operate it, certainly twice the life
lending institutions are allowed to consider.
Construction
Since the major civil works necessary to the proposed system are
already in place, minimal construction difficulties can be
anticipated. Evans Island, while remote, is near major
transportation routes and facilities along the southern coastal
area of Alaska. While weather will not pose a particular
difficulty in retrofitting the present structures, it would be
-8-
prudent to construct the instream structures as close to seasonal
low water times as possible. With the sluice pipe in place it
will be possible to re-route most water flows temporarily so
forms and other requirements necessary to construct the concrete
additions to the present diversion can be installed. This reality
allows for considerable flexibility in construction timing.
It is anticipated that the entire hydro system will be assembled
at Mt. Energy facilities and shipped at one time to New Chenega
Village by barge. A crew of required technicians will be sent to
the Village a short time before the barge is to arrive and will
prepare whatever civil works are necessary for installation of
the system. Other than the penstock, hydro equipment will be off-
loaded from the barge into the powerhouse and be immediately
installed. Separate crews will install the hardware, the pipeline
and modifications to the present distribution system
concurrently. Other than technical personnel brought by Mt.
Energy, it is anticipated that labor necessary for the project
will be hired from the Village.
Estimated construction time, on site, for the project is 4-5
weeks.
Agency Issues
The proposed retrofit described above will require permitting by
agencies of the State of Alaska, most importantly the Department
of Natural Resources (DNR) for water rights and the Department of
Fish and Game (DF&G) for certification that environmental issues
have been addressed. Since there are already two dams located on
Anderson Creek, the various agencies involved in permitting the
proposed retrofit will find it much easier to approve the
project.
There are no guarantees in the permitting process especially when
anadromous fish are involved, as in this case. The major issue
which will be raised by the agencies is what effect additional
water withdrawals in the project reach will have on anadromous
fish spawning areas and rearing ponds. After visiting the site,
it is the opinion of Mt. Energy that those areas necessary to
anadromous fish will not be affected by retrofitting the present
water system. Sufficient water will be maintained in the project
reach to support aquatic life there, but due to the gradient of
the creek there is little chance that spawning fish move far
enough upstream to enter the project reach. Considering these
facts, permits for constructing the project should be
forthcoming. If controversial issues arise, which is not
anticipated, this process will undoubtedly be the primary
impediment to a timely construction of the project.
-9-
There will be no Federal permits necessary for the project. The
electrical system fed by the project has no interstate impact, is
not on Federal lands and will not be connected to an existing
Utility grid.
This proposal is not intended to answer all questions and
concerns which may arise in considering whether to retrofit or
not. It is apparent, however, that considerable economic benefit
will be gained by New Chenega Village as a result of pursuing the
project. Mt. Energy has been very pleased to participate in
developing this proposal and is ready to move ahead towards
permitting and constructing the facility. It is not that often
that projects appear as reasonable and beneficial as this one
does.
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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6.0 NEW CHENEGA
6.1 COMMUNITY DESCRIPTION
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 nydropower 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\'Ier 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·residentfal,
commercial, and institutional sectors, and~ __ kWh/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. _ r· .
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6.2 SITE SELECTION
Several potential nydro development sites appear to be located close to
the proposed New Chenega village on Evans Island. The four most likely
sites a 11 possess small headwater 1 akes 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) was previously identified by others, but was not c~
included in this screening. It seems t~ be the least 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 "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
....
NOTE: TOPOGRAPHY FROM U. S. G. S.-SEWARD
ALASKA I I: 250.000
LEGEND
'Y DAM SITE
• POWERHOO!SE
Q SITE NO
---·-PENSTOCK
---TRANSMISSION LINE
--WATERSHED
-;
···~f
~------------~------~·~
5 0 5
E3 E3 t==i
SCALE IN MILES
REGIONAL INVENTORY a RECONNAISSANCE STUO't
SMALL HYDROPOWER PROJECTS
SOUTHCENTRAL ALASKA
HYDROPOWER SlTES 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 ternarve
Cost Power_/
( JlOOO) (mills/kWh)
2,597 466
1981 Population: 94 (by autumn of 1982)
Cost of
1-{ydropower
(mills/kWh)
720
1981 Nu~ber 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.
j;·E() ll)rJAL I rJVErHORY & RECGrHJA I SArJCE S TUC•Y -SMALL H't [t~:Qt:·OUER f'RO JEC TS
ALA5t~A iHSTRICT -CGRF'S OF ErJGINEERS
LOAD FORECAST -NEW CHENEGA
KILOWATT-HOURS PER YEAR
YEAR LOW MEDIUH HIGH
ArHWAL PEAt~ I•EHMW-K(
LOU MEDIUM HIGH
'80
.1.981
.Lv82
1983
1984
1985
1986
1987
1988
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1996
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2012
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157.
169.
180.
191.
202.
213.
225.
236.
247.
255.
270.
294.
306.
318.
330.
342.
354.
366.
378.
383.
388.
393.
398.
403.
4(:06.
413.
418.
423.
428.
434.
440.
445.
451.
457.
41)3.
469.
475.
461.
487.
o.
15.
44.
59.
73.
6:1.
1iJ2.
117.
132.
146.
163.
179.
195.
211.
228.
244.
26l).
.:276.
293.
3•)'f.
328.
346.
31)5.
384.
402.
421.
440.
459.
477.
4~6.
5,)3.
5iO.
5i.6.
523.
530.
537.
544.
551.
558.
564.
573.
551.
5119.
597.
6v5.
613.
621.
629.
637~
645~
NEW CHENEGA SITE 5
~ ! SIGNIFICANT DATA
DETAILED RECONNAISSANCE INVESTIGATIONS
1. LOCATION (diversion)
Stream: Unnamed (Section 22 Lake)
Section 22. Township 15, Ran{e SE, Seward Meridian
Community Served: Crab Bay New Chenega)
Distance: 1.7 mi Direction {community to site): Northwest Map: USGS, Seward {A-3), Alaska
2. HYDROLOGY
Ora i nage Area: 0.5 sq mi
Estimated Mean Streamflow: 4.0 cfs
Estimated Mean Annual Precipitation: 160 in 3. DIVERSION DAM
Type: Large Concrete Gravity Height: . 15 ft
Crest Elevation: 625 fmsl
Volume: 340 cu yd
4. SPILLWAY
Type: Concrete Ogee
Opening Height: 2.5 ft
Width: 18 ft
Crest Elevation: 622.5 fmsl
5. WATERCONDUCTOR
Type: Steel Penstock
Diameter: 12 in
.~ Length: 3300 ft
6. POWER STATION
Number of Units: 1
Turbine Type: Pelton
Tailwater Elevation: 10 fmsl Rated Net Head: 604 ft
Installed Capacity: 98 leW Maximum Flow: 2.4 cfs
Minimum Flow (single unit): 0.48 cfs 7. ACCESS
Length: 0.6 mi a. TRANSMISSION LINE
Vo 1 tage/ P,a se: 14.4 kY/1 phase
Terrain:.! Rolling { 1. 25) 2.2 mi
Total Length: 2.2 mi
9. ENERGY
Plant Factor: 47 percent
Average Annual Energy Production: 403 MWh
Method of Energy Computation: Plant Factor Program
10. ENVIRONMENTAL CONSTRAINTS: Unknown
Y Terrain Cost Factors Shown in Parentheses.
NE/SC ALASKA SMALL HYDRO RECOfiNAISANCE STUDY
PLANT FACTOR PROGRAM
COMMUNITY: NEW CHENEGA
SITE NUMBER: 5
NET HEAU (FT): 604.
DESIGN CAPACITY {KW): 98.
MINIMUM OPERATING FLOW (1 UNIT) (CFS): 0.48
LOAU SHAPE FACTORS: 0.50 0.75 1.60 2.00
HOUR FACTORS: 16.00 15.00 13.00 J.UO
MONTH (#DAYS/MO.} AVERAGE POTI::NTIAL PERCENT ENEJUiY USAI:iLE
MONTHLY HYOROELE CTI~ I C OF AVEHAGE DEMAND HYURO
FLOW ENERGY ANNUAL ENEKGY . ENEHGY
(CFS) GENERATION {KWH) {KWH)
JANUAkY 1.44 43949. 10.00 55211. 28407.
HBHUARY 1.10 30323. 9.50 52450. 2004!:1.
MAKCH 0.95 28994. 9.00 49690. 19157.
APRIL 1.30 38396. 9.00 49690. 24939.
MAY 4.57 72912. 8.00 44169. 42241.
JUNE 10.20 70560. 5.50 30366. 30366.
JULY 8.33 72912. 5.50 30366. 30366.
AUGUST 5.55 72912. 6.00 33127. 33127.
SEPTEMBER 5.30 70560. 8.00 44169. 41901.
OCTOBER 4.07 72912 •. 9.00 49690. 43635.
NOVEMBER 3.32 70560. 10.00 55211. 42821.
DECEMoER 1.94 59209. 10.50 57971. 36903.
TOTAL 704200. 552109. 393905.
PLANT FACTUR{l997): 0.46
PLANT FACTOR(LIFE CYCLE): 0.47
. '
HYDROPOWER COST DATA -DETAILED RECONNAISSANCE INVESTIGATIONS
Colllllun i ty: New Chenega c-
Site: 5
Stream: Unnamed (Section 22 Lake)
ITEM COST
1. Dam (including intake and spillway} J 107' 000
2. Penstock $ 89.DOO
3. Powerhouse and Equipment
-Turbines and Generators $ 67,000
-Misc. Mechanical and Electrical $ 149,000
-Structure J 30,000
-Valves and Bifurcations ·J 6,000
4. Switchyard J 99,000
5. Access $ 9,000
6. Transmission J 69,000
TOTAL DIRECT CONSTRUCTION COSTS $ 625,000
7. Construction Facilities and Equipment,
Camp, Mobilization, and Demobilization
TOTAL INDIRECT CONSTRUCTION COSTS AT 20 PERCENT J 125,000
SUBTOTAL $ 750,000
Geographic Factor ~ 2.2
SUBTOTAL J 1,650,000
Contingency at 25 percent J 413,000
SUBTOTAL $ 2,063,000
Engineering and Administration at 15 percent J 309.000
TOTAL CONSTRUCTION COST J 2,372,000
Interest During Construction at 9.5 percent J 225!000
TOTAL PROJECT COST J 2,597,000
Cost per kW Installed Capacity J 26,500
ANNUAL COSTS
Annuity at 7-5/8 percent ( A/P = 0.07823) J 203,200
Operations and Maintenance Cost at 1. 5 percent J 70,000
TOTAL ANtiUAL COSTS J 273,200 Q
' Cost per kWh J 0.72
Benefit-Cost Ratio 0.65
. ..
f
./
F-E•.· ( ONriL .INVENTORY ~~ F:ECONNA I:::ANCE STUDY -:::MALL t·h'DROPOt.lf:'R PRO.Jt· ( T :.;
ALASKA DISTRICT -CORPS OF ENGINE~RS
DETAILED RECONNAISSANCE INVESTIGATIONS
COST OF HYDROPOWER -B~NEFIT COST RATIO
YEA~·
19:34
1'~n::t:.
t·~-:::7
19!3'3"'
1'~1 90
19''i' 1
19'::1 2
1 ~~-~1 :3
1 '?.~'?.1 4
1'?.'"?./5
1996
l''i'97
1998
l''il';l•~l
2000
2001
2l)(l2
200:.::
2004
2005
2006
2007
200:3
2009
2010
2011
2(,12
201:3
2014
2015
2016
2017
2018
2019
2020
2021
2(l22
2l)2:::
2024
2t)25
2(12.::.
2027
2c)28
2(!29
NEW CHENEGA
~;ITE NO. 5
KWH/YEAR
170:345.
2(1'~1452.
24:~:044.
272477.
345t.09.
::;:7~·!570.
:382010.
:;::::7*:.18t).
::::·~::::·~(>5.
402:::51.
4(1r.:.705.
4€)':1:336·.
412'?.':.::·:;.
415854.
41:::6.21.
4212~:9.
4 2 :~::::57.
426475.
4290o;'l4.
431712.
434244.
435:343.
436442.
437542.
4::::8641.
43':1622.
4403']13.
44116.5.
441813.
442256.
442699.
443222.
443738.
444247.
444740.
4452:34.
445727.
446221.
44(:.714.
4471.::.7.
CAPITAL
2()44:3:3.
2t)44::::::.
2(l44:=::?..
204488.
2t)44:3:.::.
2044:3:?..
21)44:3:::.
204488.
2f)44E:~3.
204488.
20448:3.
:204488.
20448:3.
2044::::3.
2C•44:::e.
204488.
2044!38.
204488.
204488.
2044::::3.
2044:38.
2044:38.
204488.
204488.
204488.
204488.
2044:38.
2044:::8.
204488.
20448:3.
2()4488.
204488.
204488.
2044:38.
2()44::::::.
20448:3.
204488.
2044t3:3.
20448:3.
20448:3.
2044:38.
204488.
204488.
2044E::?..
204488.
202:(1 447592. 2t)44::::3.
AVERAGE COST
0 ~< M
70000.
70000.
7000(1.
7(1(11)(1.
70000.
70000.
70000.
70000.
71)(1(1(1.
70000.
70000 •.
70000.
70000.
70000.
70(1f)(l.
70000.
70000.
70000.
700(1(1.
70000.
70000.
70000.
70000.
70000.
7(1(H)(l.
70000.
701)€)6.
70000.
70000.
70000.
70000.
70000.
70000.
7(H)()(I.
700(10.
70000.
70000.
70€)(10.
70(100.
70000.
7(l(U)(l.
70000.
70000.
70000.
70000.
70•)(1(1.
70000.
TOTAL$
2744:::8.
2744:::8.
2744:?.8.
274488.
27 44::::::.
2744::::3.
2"744::C8.
:27448:3.
2744::::3.
~7448:3.
2744:38.
274488.
2744:?.:3.
2744:38.
2744:3:::.
27448:3.
274488.
2744:::8.
274488.
274488.
27448:3.
274488.
274488.
274488.
274488.
274488.
2744E::3.
274488.
274488.
274488.
274488.
274488.
2744:38.
274438.
274488.
2744E::3.
~744:38.
2744:38.
274488.
274488.
27448:3.
274488.
2744:38.
27448:::.
27448:?.1.
$/KWH $/KWH
NOND I :::C D I S:C
l • 611 1. 201
1. 311 0. ')08
1.12'? 0.727
1. (H)7 0. 602
o. 91 7 (1. 50'?
o. :::49 (1. 4'3:::
\).794 0.::::81
0.775 0.:::45
o. 759 o. :;:14
I). 7 45 0. 2:;,:"/
(1.731 0.261
(1.71';t 0.2:.::9
0.7(17 0.21f~
(1, .I:/':J7 o. 200
o. 681 0 • 1 (:. ·;:·
0.675 0.155
0.671) 0.143
0.665 (1.1:32
(l. t.t.(l 0. 122
0.656 0.112
0. t-52 l). 104
(1. 6-48 (1. (196
o. 644 0. 08':1
o. 64(1 o. 082
0.636 0.075
0.632 0.070
0.631 0.065
o. e·29 o. ot.o
0.627 0.056
o. 626·
0.624
c). 623
0.622
(1.621
0.1:.21
0.620
(1.619
0.619
0.61:3
0.617
0.617
0.616
().615
0.614
0.,;.14
0.6-13
0.717
0.051
o. 04:3
(1.(144
0.041
(1.0:38
!) • o:::s
0. 03:3
o. o:;:o
o. o:;-r:.:
0.026
0.024
0.023
0.021
0.019
0. 01 ::=
0.017
0.016
(1. 1:3:3
BENEFIT-COST RATIO C5% FUEL COST ESCALATION>: 0.65
-·
DAM
PENSTOCK
TRANSMISSION UNE
DRAINAGE BASIN
REGIONAL INVENTORY & RECOHHAJSSANCE STUDY
SMAU HYDROPOWER PROJEClS
SOUTHCENTRAL ALASKA
NEW CHENEGA SITE OS
CONCEPTUAL LAYOUT
SECTION 22 LAKE
DEPARTMENT OF THE ARMY
~~~~A -~s:r~·~r: ___ _
!.
;
CONSULTANTS
William L Shannon, P.E.
Stanley 0. Wilson, P.E. 5111
SHANNON & WILSON, INC.
Geotechnical Consultants
5621 Arctic Blvd., Suite B • Anchorage, Alaska 99518 • Tele~hone (90n 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 5
Bayes 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.
ay, :t~ .dzty,_,
Fred R. Brown, P.E.
Senior Associate
FRB/slt
Fllld R. Brown, Jr., P. E.
Manager
..
Title Sheet
CRAB BAY DAM NO. 4
Non-Jurisdictional Dam
A-216
Alaska, Longitude 148°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
i~R,~
Fred R. Brown, P.E.
Shannon 5 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 Resource&
A-216
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 claasified aa high hazard potential by
reason of their location. The National Dam Safety Program waa completed
in 1982. It waa intended that each state would thereafter accept
reaponaibility for non-federal dams located within their jurisdiction.
In July 1966, Governor William Egan aigned Alaska Statute AS 46.15
"Water Use Act• under which the Alaaka State Dam Safety Program has been
initiated.
under AS 46.15, Crab Bay Dam No. 4 waa inapected for the firat time
on September 23, 1985, by Shannon & Wilaon under contract to the State
of Alaska, Department of Natural Reaourcea, Division of Land and Water
Management. The dam, conatructed in 1984, ia an 8-foot high 12-inch
wide reinforced concrete wall embedded within a rock foundation. Wood
plank insert& in the center of the dam form the apillway and provide for
reservoir level adjuatmenta. The dam ia deaigned for overtopping,
however, under extreme flood condition& it ia possible that the plank
cat-walk, ataira or water a~ply piping may be d--.ged and could require
replacement or repair. The reservoir volume and the height of the dam
claasify it aa a ama.ll size dam. Because of the small reaervoir, dam
failure would poae no aafety or economic hazard& other than temporary
loaa of water a~ply. Although thia latter condition may create an
inconvenience to the villager&, it ia not considered aerioua as there ia
typically year around water flow in the creek. No major induatry
activity ia occuring in the village at thia time. The dam ia therefore
claaaified aa having a low hazard potential. The dam appears to be well
maintained and no critical deficienciea were found. No remedial treat-
ment or suggested change& appear warranted.
TABLE OF CONTENTS
EXECUTIVE SUMMARY
TABLE OF CONTENTS
CRAB BAY DAM NO. 4
PRJJECT DATA
1.
2.
3.
INTk>DUCTION
1.1 Authority
1.2 Purpose and Scope
1. 3 Inspection Team
PROJECT DESCRIPTION
2.1 Location
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
FIELD INSPECTION
3.1 Reservoir Area
3.2 Daa
3.3 Abutments
3.4 OUtlet Works
3.5 Spillway
3.6 Downstream Channel
3.7 Instrumentation
4. HYDROLOGY
5.
4.1 Spillway Design Flood (SDF)
4.2 Methodology
HYDBAULICS
5.1 Methodolgy
5.2 Spillway capacity
5.3 OUtlet C&f3City
5.4 Results
ll
i
ii
iv
v
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
A-216
A-216
TABLE OF CONTENTS (Cont' d)
Page
6. STRUCTURAL STABILITY 16
7. PRIOR REPORTS 16
a. CONCLUSIONS 16
8.1 Conclusions 16
8.2 Recommendations 17
REFERENCES 18
LIST OF FIGURES
Fiqure Number
1 LOcation 5 Vicinity Map
2 Aerial Photo
3 Dam Plan Elevation 5 Section
4 E,picenter Map
5 Geologic Setting
6 Seismicity Map
APPENDICES
APPENDIX A Photographs taken September 23, 1985
APPENDIX B OOr:pa of Engineers Forms 5 Visual Inspection Checklist
APPENDIX C Hydraulic Analyses Computer Output
Ill
CRAB BAY DAM NO. 4
aHANNON • WILaON. INC. G•••••n•••• c .......... ..
A-216
PROJECT DATA
CRAB BAY DAM NO. 4
A. GENERAL
B.
c.
Name ••
IDeation . . . . . . . . . . . • .
Year Built • • • • • • • • •
Purpose ••
I. D. N\DJ\ber • • • • • • • • • •
Hazard Classification. • • • •
Size Classification. • • •
Crab Bay Dam No. 4
Evans Island, Alaska
1984
Water Supply
None (non-jurisdictional)
Low
Small
Owner. • . • • • . . • • • • Chenega Native Association
Evans Island, Alaska
DAM
'I'ype • • • • • • • • . . . .
Crest Length •
Crest Width. •
. . . . . . .
Crest Elevation. • • • • • •
Height • • • • • • • • • •
SPILLWAY
Type ••
Location • • • • •
Side Slopes ••
Crest Elevation. •
Bottom Width • •
. . . . .
X.nqth • • • • • • • • • • •
. . . . .
. . . .
Discharge Capacity at Dam Crest. •
stop Timbers in • • . • • • • •
Stop Timbers at El. 248 1 (normal)
Stop Timbers out • • • • • • • •
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
D. OU'l'LE'l' WORKS
Type • • • • • • • • • • • • • • • • •
Location ••
Invert Elevation •
Size • • • • . . . . . .
X.nqth • • • • • • • • • •
Outlet Type •••••
Discharge capacity at Dam Crest ••
v
Steel Pipe w/ shear gate
Below edge of spillway
245.5 ft.
12 in.
3 ft.
12" pipe free discharge
15 cfs
E. RESERVOIR
F.
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
A-216
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 oams, dated May 1975, and published under Title 33CFR
Part 222.
1.2 PuEP?se 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 to insure
continued public confidence in the integrity and safety of these ~r
tant structures.
'l'be scope of the report is to coqj)ile results of a visual in-
spection of Crab Bay Daa 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.
A-216
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
Sba.nnon ' 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 eDlployee 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 d&lll site for the inspection. Mr. Jim CrUIIl of the Public Heal tb
Service was subsequently vbited in Anchorage. He is a representative
of the dam's designer and provided "as-built" drawings of the dam, a
plan map of the village and stream flow calculations used to desi9D 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 D&ll 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. Ml:lr, specifically,
the daa bas coordinates of longitude 148°1 • W and latitude 60° 4. 2 • N.
Aa shown in Fi9Ure 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
2
A-216
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 daJD 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 DaJD 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 saall size category, the
minimw. 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 channel 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 ilnpacted 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 pur.poaes. 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 co~lete new water supply system
for the new Chenega Village. The entire water supply system, shown in
Piqure 2 included the dam, an access road, a 50,000 gallon tank, a
treatment plant, and associated arctic water supply pipeline from the
daa 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 ' H\UII.&n Services and is
attached as Piqure 3. Dates on this sheet and on Piqure 2 suggest that
the daa 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 villaqe 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. Prom this funding, a complete new village
includinq approximately 21 new homes was desiqned and constructed along
with support systems such as the water supply system described above.
With the exception of a few older homes, moat of the facilities are less
than two years old. The dam's facilities as well as moat of the villaqe
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therefore are new and in good condition. Little maintenance bas been
required.
2.5 Geology. Seismicity and Climate
2.5.1 Regional Geology
Evans Island is located in Prince William Sound approximately lOS
miles southeast of Anchorage. Crab Bay Dam sits above Chenega Village
on the western coast of Evans Island and is underlain by interbedded
alate and graywacke, or metamorphosed silts and silty sands. Moffit
(1954) described these rocks as slightly metamorphosed aedimentary
deposita 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 ft)untaina Fore Arc Ridge
which is composed of slabs of ocean floor deposita overlying oceanic
crust that have been intendttently sheared off when topographical
irregularitiea 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 froa eroding continental margins such as
along the west coast of southeast Alaska. The Pacific plate acta as a
conveyor belt delivering these sediments to the fore arc trench where
the deposita are either carried into the subduction zone or are stripped
off and beCOIIIe 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 & caas, 1958). uplift within the area baa
exposed the sediments as well as the underlying basaltic crust to
considerable erosion by streams and glacial scouring with only minor
deposition occurring.
5
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2. 5. 2 Site Geology -The dam is located in a narrow stream cut.
rock 90r9e at an elevation of about 250 feet above Sawmill Bay to the
south. At the dam site, the gor9e slopes formin9 the rock abutments are
steep and drop abruptly about 30 to 40 feet across an 80 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 9ray in color, moderately hard, and brittle and has steeply
dipped foliation at 50 degrees or more to the east with beddin9 planes
parallel to the creek. From exposed road cuts, it appears that the rock
is soft enou9h that it can probably be ripped in part because of its
brittle and hi9h an9le thin beddin9 characteristics.
The surface soils in the hills on either side of the dam and
reservoir are mostly peats and muske9s overlyin9 the bedrock. This
or9anic mat was likely created as a result of poor local draina9e of the
bedrock and hi9h 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 villa9e proper.
The islands shape, as shown in Figure l, is irregular and is due to
structural features, faults, folds, and differential erosion. Althou9h
not observed at the dam site, 9lacially derived soils consistin9 of
sands and gravel are probably locally smeared over parts of the bedrock
and lie below the or9anic surface mat. We understand that the Alaska
Department of Transportation and Public Facilities identified one
granular source for local road construction in the villa9e. 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
6
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as one of the ~st 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
~vements of the Pacific and the North American lithospheric plates at
their common boundary as shown in Figure S. 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 ~st 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 islandJ
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 ~nths, generally about half of what it is in the fall.
0 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. The basin is remote and lies directly
upslope of Chenega Village. The fan shaped watershed topography is
steep and rises from elevation 250 feet at the dam site to a surrounding
7
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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 &mall 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 ~aterahed area.
Below the daa, 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 Saw.ill BAY approximately 0.6 miles
below the dam. The drop in elevation from the daa to the bay is about
250 feet. Homes lie on the east aide of the creek but are elevated
about 5 to 10 feet (or more) higher than the creek.
2.1 Description of Project
The daa 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 upstreaa face has been grouted. An 8" iron
channel covers the dam crest providing increased erosion protection
during overtopping and support for the cat walk.
8
!
.1
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The spillway is an ungated overflow notch cut in the center of the
concrete dam. It baa a steel lined opening 4 feet wide by 4. 3 • high.
Redwood tongue and groove boards inserted in the spillway bottom allow
for heiqht 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 Fiqure 3. The overflowing water hits a
splash pad consistinq of large rocks.
The outlet structures are a horizontal intake screen and gate valve
for the water supply system and a qate valve and pipe for draininq or
flushing the reservoir. The locations of these facilities are shown in
Fiqure 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 qate 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 Fiqure 2. The other outlet is a 12-inch
diameter shear qate 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 hiqh stairway is needed to reach the dam within
the narrow steep aided qorge. These steps approach the daa from the
upstream right abutment and provide direct access to the daa crest and
the cat walk and hand railinq which pass over the dam.
2.8 gperation and Maintenance
Because the daa 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 ~he reservoir
bottom. Mr. Jim erua of the Public Health Service indicated that this
was recognized by the desiqners. 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
tecorder. Select color photographs are incor;porated 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
··:lf the designers of the dam, provided •as built• drawings of the dam and
answered uny 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 signa o:.: instability or slope failure.
If the slopes should fail, material movement would be small, consisting
of local m:uskeg. Additionally, the dam is designed to accoiDIIIOdate
10
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routine overtopping. Therefore the reservoir slopes and their stability
.ue n~t judged to have an adverse impact that would influence the long
't:.erm performance of the dam.
The steep slopes and high hydraulic gradients in the basin, how-
•ner, will cause rapid runoff and peak flows which will carry greater
·t:.han normal organic debris to the reservoir. The condition is not
•:onsidered a safety hazard but rather a maintenance problem requiring
J?eriodic flushing of the reservoir to maintain the reservoir• s storage
':apacity. Large debris in the form of logs or stUDips could, however,
'Berve as a ram possibly damaging the weaker elements in the dam
requiring repair in unusual cases.
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
·~uantity 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
,aeepage 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
,,f large rocks below the spillway was intact. Evidence of erosion of
the foundation or the abutments that would endanger the stability of the
,aam was not observed.
In summary the concrete dam appears to be sound and in good condi-
tion as there are no signa of distress cOIIIDOnly associated with dama
that are marginally stable or unstable. No evidence of settlement,
differential movement, seepage, concrete crackin9 or &palling or other
structural distress could be found.
11
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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 grouted 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 keeping the reservoir level roughly 18 inches to 2 feet below the
crest. This condition is shown in Photographs l 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 saall size.
12
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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 co111110n. 'l'he 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 Oesiqn Flood (SDF)
The SDF for a dam with a size classification of •small• and a
hazard classification of •1ow• is recommended to have a frequency of
50-100 years. 'l'he SDF for Crab Bay Dam No. 4 was generated for a 100-
year storm which had a duration of 24 hours.
4.2 Methodology
'l'he inflow hydrograph was dete~ined by applying the 100 year storm
to a synthetic unit hydroqraph. A Snyder unitqraph was developed.
Basin laq time was estimated to be 1.0 bourJ 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). CU.matological 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
~as used to assess the results of the synthetic unit hydrograph approach
(U.S. Dept. of Agriculture, Forest Service -Region 10). With this
1aquation, the peak plus 100 year flow at the 90 percent confidence level
·~as estimated to be 290 cfs. The unit hydrograph approach yielded a
;!?eak ordinate on the inflow hydrograph of 385 cfa. For the hydraulic
.lnalysis of the spillway, the higher value (385 cfs) was used.
5. HYDRAULIC EVALUATION
::> .1 Metbodoloqy
The hydraulic analysis of this dam was accomplished with the Daa
:Safety Analysis Program provided in the u.s. Army Corps of Engineers
JtiEC-1 Flood Hydrograph package. Reservoir routing was by the Modified
JPuls routing technique wherein the flood hydrograph is routed through
lake storage. Since the lake is small, travel time of the 'flood wave to
·t.he outlet was assumed to be negligible •
...
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5.2 Spillway Capacity
Spillway capacity was computed by considerinq the spillway as a
sharp-crested weir. The equation Q-CLH 1 • 5 was used. L-spillway
lenqth • 4 feet. H • 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 beqins 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 cfa 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 (AJC 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. This
debris could block the channel and cause local downstream flooding.
IS
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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 co~leting 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 RECX>MMENDATIONS
Proa this inspection and evaluation of Crab Bay Dam No. 4, the
inspection team presents the following conclusions and recommendations.
B.l 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.
16
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2. 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.
3. Under infrequent flood conditions, the dam is designed to
a.ccolll'llOdate overtopping. Under these conditions damage to
some support facilities could occur from flood forces and or
moving debris.
\
4. The reservoir can be cleaned of debris by periodically opening
the 12-inch shear gate and flushing the debris downstream.
El. 2 Recommendations
1. The dam is in excellent condition and no corrective measures
are considered necessary.
2. 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) Noxmal flows (monthly) -water depth in spillway
b) Da.ll. overtopping ' height of overtopping
c) Reservoir flushing
d) Valve or gate exercising (at least annually)
e) Other repairs, maintenance, or observations that may be an
indicator of changing performance (i.e. cracks, spalling,
displacements, erosion, seepage, etc.)
3. Logs, stumps or other large loose debris should not be allowed
to collect against the upstream dam face.
17
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REFERENCES
Eleikma.n, 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.
!~eikman H.M., Holloway, c.D., 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.
l~spinosa, 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.
I..eet, D.L., Judson, s., and Kauffman, M.E. 1978, "Seismicity of Alaska
and Aleutian Islands: in Physical Geolo91": Prentice-Hall, Inc., p.
147-153.
)~yers, H., 1976, A historical summary of earthquake epicenters in and
near Alaska: NOAA Tech. Memo., EDS, NGSDC-1, p. 32-42.
~~ffit, F.H., 1954, "Geology of the Prince William Sound Region,
Alaska," u.s.G.s. Bulletin 989-E.
J>lafker, G., Jones, D.L., and Pessaqno, 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.
t~dike, 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.
IJ.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 Colllll8rce, Environmental Science Services
Administration. "The Prince Williaa Sound, Alaska, Earthquake of
1964 and Aftershocks. • Vol. 1, u.s. Government Printing Office,
Washington, o.c., 1966.
u.s. Department of CoDIDerce, Weather Bureau, 1963, "Probable Maximwn
Precipitation and Rainfall-Frequency Data forAlaska": TP No. 47.
18
TABLE 1
ALASKA CLIMATE CENTER
ARCTIC ENVIRONMENTAL INFORMATION A~D DATA CENTER. UHJYERSITY Of ALASKA
ta~AlVBfiE t21 ;~w MEANs AN~L~~~1WR~1•fah ~~=~auv 1975-1979 CRAB BAY
ELEVATION 10 FEET
--···-----------------------------------------------------·------------------------------------------------------------------· I T E M P E A A T U A E CO E G -FJ I P A E C J P J T A T J 0 N T 0 T A L S Cl H C H E St :
·---------·-----·---------------------·---------------·------·-----·--·-----·--·--·------------------------·-·----------~· MO : MEANS I EXTREMES I MEAN NUMBER : MEAN &6AEAT:YRJGREAT&YR:DAI SNOWt SLEET IHEAN f OAYS:
: I : Of L)AYS : :MONTH: IDAILYI I J I : ;·or;·:·oc;;·"a·:-ii~iviiovi-i£cii"~;;--"ii--;--"i"--; I I I I 1 i-MEANi-Mii-ivR;6R£iiiviioi;:io::;o:i:o:
I ~AX : MIN: I hi : l : LOWI I •···••••••••••·•• : I I I I : JHONTH& :OEPTH: : : • ; • : • 1 : : : I I : : I I ll0+13Z•Il2•l 0-: I I : I I I I : I : : : I : :
---··-----··-~-·----·----·--·--··---·--·--·---·---·---·---·------·-----·--·-----·--·--·-----·----··--·-----·--·--·---·---·---· JAN I 35.3 21.1 11.21 44• ll Z5-0 75 011 0 1 ZZ 01 16•0• Z9e55 ll 3.31 ll 04; Z6.1 51e0 79 60.0 79 JO; 16 1Z 7:
I I : I I : 1 FE~ I 35eZ Z4.0 29.61 46 ll 04. 9• 79 101 0 I 24 .01 15.Z6 Z6.12 7l Je10 ll 011 40e6 116.0 75 60.0 79 Zl: 16 10 51
I I I I I I I MAR : 31.1 25.7 31.11 51 75 Zl. 10 75 ZZI 0 Z Z6 01 U.Z6 ll.J4 ll 2.65 ll Ul 40.7 6).0 77 llaO 16 31: 11 11 4:
I I I : : I 1
APR I 43.5 Z9.0 36.31 5•• 76 29 10 76 061 0 0 23 01 10el9 16el7 76 2al6 16 Z61 17aZ lleO 75 74•0 76 05: 14 1 4: ; . I I I I • •
MAl I •1.1 34.9 41.1: 67 ll Zl ZS• 11 111 0 0 9 o: 1Z.71 16.75 ll 2.6Z ll Oll 60e0 75 Oli 11 9 5i
I I I I I : I JUN I 5lal 42a0 49a61 73• 11 JO JZ ll 011 0 0 0 01 3.72 4al5 ll 1a16 ll 111 : 9 J O:
I I I : I ; 1 JUL I 6Z.l 47.3 55.01 11 75 01 41 76 061 5 0 0 · 01 1.63 6a74 11 Oal5 ll 211 1 1 l 01
AU~ J 6J.z 47.7 5s.si 79• 11 zt 11• 11 11l 1 o 1 ol 1.67 11.11 76 2.65 11 oel i az 6 41
l I I I I I 1 SE~ I 57.1 43.1 50.11 61• ll OZ 31 76 291 0 0 0 01 11.11 l1.4Z 76 1.70 ll 141 •• • 11 lZ 1:
I I I I I I ~l I 46.6 35.0 40 •• 1 51• ~l 05 ll• 76 Zll 0 1 11 01 26el4 16.14 ll 5.57 ll 01 la6 11a0 16 11.0 76 JOi 23 14 101
I ; I I I • 1 ~ov 1 11.1 Zl.3 32.51 504 76 1J 15• ll 251 o 3 25 o: 16.61 42.11 76 5.73 76 301 11.5 4o.o 75 zz.o 75 lti 16 10 1 1 II : I I I ; 1
DEt ; Jle4 Z4.1 Zlell 41• l6 25 5 75 061 0 10 27 01 15.52 2le56 ll 1.95 76 111 44.0 56•0 75 llaO ll Zll 22 9 41
I I I I I ; 1
·---·--·-·----·-----·-·------·---~--------·--··-----------·---------------------------·--------------------------·-----------· • JUl JAN HOY NOV FEB APR
YEAR 46.6 l4e0 40.)1 ll ~5 01 0 75 011 I J1 161 Oll60e46 42e11 l6 S.lJ 76 l61l96a5 ll6e0 15 74.0 76 051111 105 51
-
•
SEWARD(A-3) QUADRANGLE
., 0 t se--......--
SCALE-ULE8
I a
.. .. -
" ~-31
Crab Bay Dam No. ~
Evans Island, Alaska
LOCA TJC:>N & VICNTY MAP
April, 1986 A-216
IHANNON a WILSON. INC. ,.. __ . _ _..._. __ . ~"---,.··----FIG. 1
II
u. s. o.,.a-... of Hea~~t~ a l+.llnOR Suvic11
l'l.!blic ...... s.r.ica
lndiaa Heallll Senic•
CHENEGA BAY. ALASKA --Te "**C LAW ... 121 I'ICUKT
I'IIO•Cl NO. -v·f••
-...-M II "'•lt:llt#•ll• ..... , .....
-I
,..,.., •tiON hoCNfln CONii'IUC"'IIN M.......OO
IIMIIOIIMIIfi'.IL llll:.t&.I'M lltMICH
........,.,..._ ....._.. ..... t ..
IG.2
u.s. o.,o-... of.._.... a ... ...,... s.nca
Ntlic .._.... SeMca
lndiaft .._.... SeMca
CHENEGA BAY, ALASKA __ ,.
I'IIIUC u.w ... ,. 1'110.0
--D4 -' .............
~· ~ •n•oo•-
OOUkl r • 1
CYIEWm FROM DOWN STREAM fACE)
114• ttii.L 101 --
~LIO
r Uri 'fM.WI
OL&ca L&aaa •ocu--
-IPLUM PAD
o-r fLAWIC-
IIICM,8J , •• r
--------~
4• I I•
PLAN VIEW
--
~..aca
-qy CDICIIn'l liTO CIIDJI -. ,._.. .. u .. -ro _ .... _
._....__ __ IJIR c:MA-~L lfYPI
, ..
...
\ r 1r r • ,,_. .u...a .-:
IIM.•WG.IInl-·
', ...
• &M ...__-'I'D ,. c:&•uxa
' .... ''"~' ""'-lt-D I'IUL 1'1'1 .-r-.....aca IGI.tll
SECTION
~ .....
CAT WALK FOUNDATION ---=====-=========-=~~ .,.
---
-------------
. ....... _
IM• I&&. 'f. l'tN ----......... ...
CAT WALK
• Tt
CHENEGA BAY. ALASKA
:1o1M • "'--IL&VA\'ICII .... -TIIIIIII
"'**C U.W ... 121 NOac'l'
--C•:t --
•
II
--~
FIG. 3
~$
..... ··oanaw 1 •.
a 0 I 10 ------aca-.•a..·
, l.: ..
1
..... •..
Pt Ba.til.
How
&
j
l
GJ --...... ~:::.:--;;:-::· ....... '>¥, ......... ---.,._. ---
lEJ .. .
EJ
___ ..... __ __
........... .._.....
• ----
Crab Bay Dam No. ~
Evans Island, Alaska
GEOLOGIC MAP
ji
i
!
II a w
~
ti
It u
• }~ e !a~
'"Oc . -Ill ... .. .
u
April, 1986 A-216--
IHANNON • WILSON. INC. FIG. 4
Geotechnlcel ContiUita._::n:_:t:_l --lL..-----'-_. _
"' C) ::r; ., . ,.
,o z ;z
"0 C) iz :·. m
0 ~~ r .-0 llf" ~~ Ci)
0 =z ..: ••
ll -(/) :z m r -4
-4 z ., Ci) C5 ~ •
01 ~
I "'
mn < ., a. a.
:J 0"
"' CD -a.
"'"' a. 0
:J a. 0.9 .. z >0 -. a.
Ul./1:!"
11:' a.
, t
t f •
• • •
t t
I
-.
Generalized block diagram illustrating the geologic characteristics
of the sudduction. zone beneath southern Alaska
CD --CJ) __..._-::-----~
.:V·o·
0 .J.
Crab· Bay Dam No. It
E~ans Island, Alaska
SEISMICITY MAP
1986
SHANNON • WILSON, INC.
G•ot•chnlcal Con•h•nU
. . en r.
....
0 w
Appendix A
Photographs of Dam
Taken September 23, 1985
1. UPSTREAM FACE
2. DOWNSTREAM FACE
~ '.
.
l ' " .. .,.
3. DOWNSTREAM CHANNEL AND WATER SUPPLY LINE
SHANNON • WILSON. INC. A-2
4. RESERVOIR
I SHANNON • WILSON, INC. A ..,.
\
.Appendix 8
'Corps of Engineers
Inventory Forms &
Visual Inspection Checklist
UATIUIC~
PA.RT I -INVENTORY OF DAMS IN THE UNITED STATES lhH (PURSlJilNT TO PUBt.IC L.AW 92-3671
.s .. , • .,., •• aid. lor U.attuct.lona.
111 Ill 1•1 lSI l'l (71 l&l
(lSI (161
! a ...
"'
• 't
2.1
MAMI
lUI
(171
RIVI!II OR STREAM
Ill I
liE MARIS
1111
FOIIM A,I'PROVEO
OMI NO. 41-110411
RfOUIIIfMENTS CONTROL IIYMIOL
OAEM-C:II£-17
\
(10)
LATITUDE
(Norii•J
.....
LOHCITUOt
(N'ntj
(191
Ill
... IOUHIH ... .. HU .. Bfll ... ..
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(121
R£POIH OAT(
1201
I I I llllllllllllllllll ·
:r.TATISTICS
MI$C. DATA
(Conliftvedl
MISC. DATA
(C..IiftVed)
REJU.RK$
hH
1»1 lJOI Ill) Ill]
N .. a:
PART II -INVENTORY OF DAMS IH THE UNITED STATES
IP'ILLWAT
(46)
(,.UIUIJAitT 10 I'IJIUC LAir U-l67J
s .. ,..... .. llitH 1M ieatrv~liana.
ISJ)
IJ.t)
VOLUMI OP DAM
-tel')
IMSP'ICTIOM IT
lstJ
I:UJ (l6) 117) (ll) (J9)
141)
1St)
IS4J
(40)
Ill ..
fa-N'f'IIOV£D 1-IDtMTITY
'"' MUM. II DIIIINO • .........at 1-...
aEOUI1181ENTI CONTIIOI.ITIIIOl. •_p •J-t•I•J'
DAEN~f-17 I I Ill
(41) (41) (43) (44) 1451
NAVIGATION LOCICS
/ 141)
COHSTIUCTIOH .T
151)
ISS)
I
~
Inventory No. N/A
Sheet _J___ of ~
VISUAL INSPECTION CHECXLIST
1. Name of Dam: Crab Bay Dam #q
2. Inventory No.: Non-Jurisdictional
). Hazard Category: Low
4. Size Clasaification:Small
S. 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 (a~
9. Purpose of Dam: Water Supply
10. Weather:cool & Cloudy, 550F
Directions: Mark an ·x· in the "YEs-or "No· column.
If item does not apply, vrite •NjA• tn -aEHARKs· column.
Use •other Comments• space to amplify -aEHARXS· •
I • ITEM YES NO REMARKS
._. ~=RE~S~E~R~V~o=m?===========================~==~====~========================~
3. Shoreline Slide Potential? t~~~~IMinor rock soallina
4. Sta-ntficant Sedimentation? ~~,~~ Somf! lt'!av .. ~ t.. nr;tnrh ... c:
f II ~~S~·~A~n~v~T~r~a~s~h_B~o~om~?~-----------------------~-~~~~-~~:,~~-~~-~-~~xL-~-------------------------------~
... 6. Anv Ice Boom! ~*-;;;.~t~ Y
7. OoeratinR Procedure ChanRes? r~·Ji&! ·
e. Nev De'lelopment 1 X ~~~e.~ Bu i It in coni unr t inn w i t h ti.-=tm
l.ll~~~~~~~~--------------------------~---i----~~Njo-ne--------------------------1 -r-
~~~~~------------------------~~;-----------------------------~
~~~~~~------------1~r-r---------------------~
~~~~~~------------~B-1----------------------~
!tl
.. ..
-~ ..
A
r,l
~
rl
rl
~
\ •
•
ITEM
CONCRETE DAMS
1. CREST
•• Any Settlement?
b. Any Misalignment 1
e. Any Craektng?
d. Any Deterioration 1
e. Exposed Reinforcement?
t. Adeqwate Freeboardt
2 .. UPSTR.EAM PACE ... Spa lUna?
b. Crac:kln__g?
c. Erosion?
d. De terioratioa?
e. Exposed Reinforcement 1
t. Di splacnents?
•• Loss of Joint Fillers?
h. Silt Depodt Upstream?
). DOWNSTREAM FACE
a. Soalltna"
b. CrackinJr?
~. Erosion'
d. Deterioration?
• ExDOsed Reinfo• .. ·-~nt?
f Tn11oeetfon CallerY?
• FoundAtion Drains"
h Foundation Dr'alns Plovintr!
f. c:,.,.nJur• from Jotnt.!l' .. S••oatre from r.t l r: 1.1 ne•" .
' A RlJ1'ME]Il1' I. IATJOif COH"" .. -
• P.rno!U!~.d ~l!d'l"f"lt"k'
h P''l"ft.cf ,.,.,.,
/!" Vi ••hl,. nf an,., ,,. •"
d S•~~""~"''• frl'l'fll Cont11et."
"" Bnfls ar Snrfn•• Dnvnlltream'
Other Comm.,.lc Dam is in exce 11 en t cond i t ion
··-·"'*··-.•r•-s• --·•••••ntr lltdcWL
ShHt __ 2 __ of 5
YES NO REMARKS
TYPE: Butt n~s s
]q• lana 1 1 widP-.. ., ... f"'~
·;.~f-"":
*""-~!-·•
..:]!:~*!'
•_;, .'11~ ~~-
;·i~ .. ·-' Feteh: Az:
')."'~;;
jt,;~~
~·~~~-~'~w
l• ... ~;-~ •
~~~
.;,~~..;:
~-~~--Dfll!iianprf far n~ariarfir fluc;.h'nn -
~~J'.i
~~~·t
·~~.--.~,n:, .. ~l\1
[~;~ . ..... 7"'A:.'-·•
y~ X
!¥:;;!..'&'::!!? ·x
X
F;:"-~.x;·
·~~i:•
'"-:i:'"Yi'fl'
,-;i ~.~.£~
£.:~11(
~~~~
~~-.:.
,
• ~
.~
.f!l
~ •
~
, .
n:EM
SPILUlAYS
1. CREST
a. AnY Settlements?
b. Anv Hlsalhnmenu?
c. JiDY Cra~lc.in•?
d. AnY Deterioration?
e ":x:nn•,.d 'R,.fn~or~ .. "'"'"""
f Ero!lion"
tl Silt ~noJtt t Otult:rea.m7
2 JN lKlJI. :S KUL~HIK I"::S
a. Mt~~rh.~anfra1 ~auinm,.nr nn,.r,.l\1•'
b Are Cate!l Mllintafned't
lnweniCHy No. __ N_/_A _____ _
ShMI --~3_ol_ .... s __
YO NO REMARKS
TYPE• Dire~t Overflow thrnunh
Weir
TYPP.: Woon olanks
~;!: ,.;,.. ... . ..
f-i·.~ ;;:;-.,~
,-~-~: ~ : ~ ~:
iit ~-· ...
I :(f. ~,..;~
-~ ~~
·rJe ;,Jt\-.
TYP!: F" 1 :ac:.hh.-.,. r...tJfO •
~'?Jm ~nn•
~J. • c. . Vlll Fl~tllhhn-"rd~ Trf n Ant'nmllf'f ~•t hrf X
d. Are St.&n~hlon~ Trinoable' lf~'l1:'~
I!! Ar .. r.;~~~ ,..,.,. R""'"" f"el, r.nn,.rn 11 """ X • 1. CHlJTE TYPE: ~ ........ -n: r.,.,. t-nv .... ~ln ..
• AnY r.rArftfnt11'9 ~~"'\~
b •. AllY. Deterioration" ~tro.
~ Ero!'lion' ,~~,:~
d. ~nn•u•d 'R,.fnforc."'m"'nt" ~~l~
"' It". ••• ~ l.f rr. J.tn .......... 1'<"lfrtf"•., ~t.'54l~ • ,. ' nr~~TP.tTnRC TYP!: None Dir:ect. discharae in
;Ill Anv n,..,.,.rfnr•rfnn" ~~~"':~ c-,:;anne J
h ,. ............. ., ··~.
~ F.-lrnn,,.•d 1t,.tnrnr~•..,•nt''t r•2;~ • 'i MP'Tll A rAN~C t;IO-;;-.; .. r,. .......... f tut" ·~~-_;
" 'Rr~•1ta~•• " .. • ,. c: ............. .1 ...... --........ 1-;~#V".;
" n.fP'R ~PTI.H.JAT TYPE: ~nn .. .. Ad .. An• ,.,.. l!Pa •• -., ~w-.~:,;.~
" ~1.JI!.aP .& ..... ,.. .......... r'h•n"•'" ~:~~!
,. i:rnd f hl;. "" ............ r.l\"'"'"'' f 'I"J"".; ..
d P'Pndf1.1a ...... 111u•f ~ ....
• ~tahl• Cfda ct ... -•9 ~~~·{;
"'""
' --
I
,_t,>.
' -·-·
I -
I -·
-I
I
''''"
I
I _,.,
.. I
I
.. .!
I '
ITEM
LOU LEVEL OUTLET
1. GATES
a. Mechanical Equipment Operable?
b. Are Cates Remotely Controlled?
C• Are Cates Maintained?
2. CONCRETE CONDUITS
a. Any Crackin~t?
b. Any Deterioracion?
c. Erosion?
d. Exoosed RelnforcinK?
e. Are .Jointa Displaced?
f. Are .Jo!nt:a Leakina?
]. KETAL CONDUITS
•· Is Metal Corroded?
b. Is Conduit Cracked"
c. Are Joints Dllllola~ed"
d. Are .Joints Leaking?
4 ,y DISSIPATORS
a Anv Y'J@t'fl!rfnr;~~t-fan'P
h •. P:rolllfon"
fl". F.xnnlllfl!d Rl!!'fnfor~,.,.~nt:'P
~~= KETAl APruK tr.nANC!!S
a. Corrosion"
h. 1l .............. ?
t" t:: ... .-.,re Anl"h..,raoo""!ll'
I
a
.,., Commentc
I
Inventory No. _N~/:...:A:..:-.. _____ _
Sheet __ 4:,..__ ot _ __.,_5 __
YES NO REMARKS
TYPE: Steel pipe with shear qate
P.H'X..,"'t'
X
~, J('._;" ·, New
HLA
'?=~~~t'_
._~~J.i.•~
ir' &;.;;::..'
ft"c~"'-'·
~~,...,
·~.~·.:!::
12 11 oioe -36 11 lana
~~·.h New
~~~-
:'S:Y!.'!-
~fit\'~.
NonP:
~~:;r:i-.:;;;.~
~;--'!-,•
~~-·,~.-
Shear gate -Wheel has been
·~-x.·;:' removed. probablv to orevent
~. unauthorized ooeration.
~~~:~t~"·
I .. ~
I
I ITEM
Poo INTAKES
I
'"~' 1. EQUIPMENT
I a. Trash Racks?
b. Trash Rake?
'" Co Mechanical Equipment Operable?
d. Intake Catea?
e. Are Racks and Gates Maintained!
f. Are Cate Operators Operable? I
,~, 2. CONCRETE SURFACES
a. AnY Crackina?
I b. Any Deterioration? I
·=.l c. Erosion?
I d. Ex nosed Reinforcement?
~ e. Are Joints Displaced?
,J f. Are Joints Leakintt? I
J. CONCRETE CONDUITS
a. AnY Crackintr?
I b. Anv Deterioration?
,_! c. Erosion?
d. Exoosed ReinforcerDent?
' e. Are Joint a Disolaced?
J f. Are Joints Leakind
I
I
I
4. METAL CONDUITS
I
I
I
I
I a. 1!1 Het:al rtrroded!
I b. Is Conduit Cracked? ..... c. Are .Join~• Dtsolaced?
d. Are Joint• ~..!akin~?
I 5. METAl Arr JK.l!!.riANCES
.J. a. Corrostoo9
b. Breaka~re9
I r ~il!'~ure An~horlltres9
I 6 PE
a. Material O.terlorated!
b .Joint:• U!&lrfn~f
I ~ Sunnnrf'!l Ad•nnat:~?
··~ d Anrh .. n• 1111nrlr• Stable?
I
I
lnwenlory No. ---UN"-/..wA _____ _
ShNt __ s...__ol 5
YES NO REMARKS
w ... 11 <:,..,. .... ,.. ~ Pininn -
X
X
·~rft.l!'t Valves
X
~~:{" NPW
~~~~-~-r-·
Nnn<~>
~:
i~.a:;
~~
~~
~-
i~~;;..
........ _~
~~-c.<
~~
In:".&."~;,
,;;;.t_~i
.:rt::~;~.
''~"i.:l+"';
Ht~•j,;
'~~~!'
'~!.<V :-:·
J'.'¥.6-";
,.,. .......
~-,._,.:
",$x~
d~ ... ~'!-'1:
TYPE ~TERlAL: Arctic Pioe
~~X,~'
.o.:.,-l}(_. ',~'
•1oXL.
~~~~fii~.~-
I c-... ., Comm•nlc Dam is new (constructed In 1984) by the Public Health Service. It was
constructed of concrete tied into sl~te rock abutments on both sides.
Appears to be in excellent condition.
I
APPENDIX C
HYDRAULIC ANALYSES
COMPUTER OUTPUT
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A THE HYDROLOGIC tNGINCCRfNG CCNTE~ A
.. ---..... -·--·-------;--------&~-~ti:t:Httt-ti!~£~------· "'*.
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CONTAINS MEW OPtiONS ON RL ANn BA RECORDS, AND ADDS THE HL iECORD. SEE JANUARY 1985 INPUT
DESCRif'TIOH PO~ NEW DEPINITIONti.
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RATIO KAXll'tUK
-----------OP-----RESERVOii
PKF W.S.BL~V
-thlle----2St. 4S..·-
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------e;-65 -·-2~!.63
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.. r • • _..,..,. p r r.r r p ~t~ ~ ~ ---·---__ .. ___ --~ -~
HEC-1 INl'UT
L 11'11: 1D ••••••• 1 ••••••• ~ •••••• • ~ • • ••••• 4 ••••••• ~ ••••••• c., •••••••• , ••••••• tl ••••••• ~ •••••• 1 0
1
:J
J
Ill· KENAl f't:NNlN!iULA ~~79.0
Ill DAM SAFETY ANALYSIS
ID ANAL\':.; l!i (It' CkAl1 IIAY _ ... -....... --·---· -----··--..
IT :5 0 0 300
ll) 5
Jk l:'l.OW .20 . ·:-.3~ .50
IJAH NO.
.~;:;,
~ ~K INFLOW INFLOW TO CRAB 8~Y UAM HO. ~
8 .. _,. ___ -IIA-l)c37-
9 BF -1.0
10 tK 12
11 · · ·LU · • 0. S
12 us 1.0
13·· ----
14
15
1&·
1?
18
19
20
. -· -t{l( •..
KO
RS
. ·-· SY ·
SE ss
· ST ·
KK
. lti"'M
5
1
0.06
;.!4'7.7
241:f.O
352
RCHl
-.o:s
1. 0
;,}
.40
2.0
0
... CRAB· BAY· ·DAM
ELEV 24?.?
o.H -0.20
::;4! 25~
4.0 3.0
14.5 a.o
NO 66
NO. 4 .
1. s
1.5
1 -------------
.oo . 1. 0-·----------.----
·----------------
75 10()
. -·-· ·---·---------------
.--· -----· -..... -··-----·-·. ---· ---
. . . . ---· -·-----· -------
···21---
~2
• 1(111 .. JcfJIJTI:i OUTFLOW !'ROM RESERVOIR TO CREBt{ AT -VULIACH). ·-
23
24
25
26
R9
fCC
RX
RY
zz
1 now -1
.o5 .os .o~
0 ~0 40
30 l~ ~0
:.:::oo .oa
UQ
25
100
30
\
--.......---....~---
'
OPERATION
HYDROGRAPH AT
ROUTtD TO
ROUTED tO
PEAK FLOW AND STAGE (END-OF-PEWIOD> SU"MARY fOR MULTIPLE PLAN-kATIO ECONOMIC COMPUTATIONS
FLOWS IN CU,IC FEET PER SECUHD, AREA IN SQUARE MILES
--··-----·-------TIME--TO PEAK IN HOURS -------------------------
STATION
INFLOW
.. --. --
DAH
AREA PLAN RATIO
0.20 ---------·---------
0.3? 1 ELllW . n.
ti11E 16.~0
0.3? 1 fLUW '1'1.
TIHE 16.~tl
RATIO!:
RATIO ... ...
0.3~
1:l~.
1&.~l'
13::i.
1&. ~(l
---..-------------------
RCH1 0.3?
~~ PEAK STAOES IN FEET A*
1 STA~~-251.45 252.56
--TIHE 16.~8 16.:S~
1 fLOW 'l?.
, ·-t tHe------16 ,;61
134.
"16•61'
i
U PEAK STAGES IN FEET U
. 1 UA~E ·15.92 16.:J'J
TIHE. 16.61 16.6?
APPL:lEil TO FLOWS -----·· -----
kA!IO 3 RATIO 4 RATIO :; RATIO f.
o.~o o.&!J o.uo 1.00 ------
1~0:. :.!::iO. JOU. 385.
16.5(; 16.5(; 1&.::,u 16.5F.I
1':1;.1, :.!:SO. JO:.J. 385.
lb.SO H.::,I.J 16.:;,t; 16.58
.... ··-···-·-----------------
::::.3.14
16.':)0
:.:~3.63
·16. ::itt
254.06 254.59.
16 ; 58 --· · Un S 9
192. 250. 30lJ. 385.
16--; ::i1t·---i fr:'ti1t-·--t116~.~:;Wttt---+l fr(l ~. 5!"rifl~.
16,6:':f . -16-,99--·11-.-14·---}7T46
16.:Sij 16.:S~ 1G.sa 16.58
5 IO
IT
~ENAI PE~NINSULA 4679.0
DAM SA~ETY ANALYSIS
ANALYSIS OF CRAB BAY DAH NO. 4
OUTPUT CONTROL VARIA~LES
-··--·-tf'I<NT-· --·· ·· -· 5-PICIH! -tUNti<OL·
IPLOT 0 PLOT CONTROL
OSCAL 0. HYUkO~kA~H ~LOT SLALE
HYDROGRAPH TI"E PATA
NMIN ~ l'tlNUT~~ lN CUH~UTATlUN INT£iVAL
·---· -----IDIITE-· ·-··-·1 -·-0·-&TIII·T-IffQ ·DAt-i--· ·
ITIHE 0000 ~TAkliNU TIME
NO 300 NUttiER OF HYDROORAPH ORDINATE~
Hlll•tfiTE 2 -0· ·· ENl• lNtt DttiTE
NDTIHt 0055 .tNDINO TIMt I
-·-----· ----·-·eotti"U!1tt lON-·INTUVAL -...,....-e-;-08--ttOUH-i
TOtAL TIHE BASE 24.92 HOURS I·
ENflL ISH-liN I-T~ . -I
llRAINAijE AREA SOUARE HlLES
~~EClPITATlUN DtPTH INCHES
·--···------t;£H8!tt;-!i:EY#tt ION-··-···· FEET-----·-··---~.'
. FLOW CUBIC FCET PER SECONf•
STORAU£ VOLUME ACkE-FEEt
--· !IUIU'A'tr: AltA IIICRE9 --· · ··· ··
TEHPEkATUkE D~Ok~E~ FAHR~NHEIT 1
JP ----i1Ul;!T,-PI:IIN··OPT!ON-----· ----· ------· .-·
NPLAN l NUH~~k U~ f'L~NS
JR ------·MtH.-!·1-RIIUO OPTIOH
14 t<O
RATIO~ Ot RUNOFF
0.20 0.3:5 0.50 0.6~ o.eo ------------· ···---·---· ·--------------· -·····--.
OUTPUT CONTROL VARIABLES
I~RNT 5
· ·-·-I PLOT 0
QSCAL 0.
~RINT CONTROL
PLUt·CONTROL ·
HYDkOUkA~H ~LOT SCALE
1.00
leU WARN ING--**""-MOHF-IED--f'YL6 ROUTING HAY -BE HU"Iiii·-ICAL&. Y · UN:iTA8LG FOR OUn'LUW~~tW5tN Yi'U. tO ~ U\li.
/ ·'---
THE ROUTED HYDROGRAPH SHOULD IE EXAMINED FOR OSCILLATIONS UR OUTFLOWS GREATER THAN PEAK INFLOWS.
THIS CAN IE CORRECTED BY DECREASING THE Tl"E INTERVAL OR INC)EASING S10RAGE CUSE A LONGER REACH.>
-------. ------------------
CANYON INDUSTRIES, INC.
SPECIALIZING IN SMALL WATER WHEELS
October 9, 1987
Mr. Jack Goldwausser
Mountain Energy, Inc.
P.O. 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
s~ 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. Sin;,
Daniel A. New
DAN/mm