HomeMy WebLinkAboutScammon Bay Prelim Evaluation of Small Hydro Power Development at Scammon Bay, AK 1980DATE
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PRELIMINARY EVALUATION OF
SMALL HYDROELECTRIC POWER
DEVELOPMENT AT
SCAMMON BAY, ALASKA
ALASKA DISTRICT
CORPS OF ENGINEERS
DECEMBER 1980
SUMMARY
Scammon Bay is a village of approximately 200 people located on the Kun
River near the Bering Sea. The village currently derives all of its
electrical energy from diesel fired generation.
The Corps of Engineers was authorized by Congress to conduct
feasibility studies for the development of small hydroelectric power
facilities at isolated villages throughout Alaska. During the preparation
of the feasibility studies, the Alaska Power Authority requested an
evaluation of hydroelectric power at the community of Scammon Bay. This
preliminary analysis is in response to tnat request.
This report includes a preliminary engineering, economic, and financial
evaluation of possible development of hydroelectric power on a small
stream near Scammon Bay. The estimated cost is $1,010,000 and the project
woulo have a peak capacity of 150 killowatts. Based on financial criteria
estaolishea by the Alaska Power Autnority, (30 year pay-oack, 10 percent
financing) the project would produce energy for approximately 31¢/kWh
during the first year with very little increase in future years. Tnis
figure includes interest, amortization, operation, and maintenance. The
current figure for diesel fired generation is approximately 30¢/KWh, which
is expected to double in 10 years. Neither of these figures includes
administrative overhead, taxes or insurance.
Although hydroelectric generation is initially more expensive, by the
second year of operation it should prove to be less expensive than diesel
and by year 2000 hydroelectric power would be less than one fourth as
expensive as diesel. This is based on an assumed inflation rate of 7
percent and diesel fuel escalating at 3.5 percent above inflation.
INTRODUCTION
COMMUNITY PROFILE
GENERATION FACILITIES
ENERGY DEMAND
HYDROLOGY
DESIGN FEATURES
ENVIRONMENTAL IMPACTS
COST ESTIMATE
ECONOMIC ANALYSIS
FINANCIAL ANALYSIS
TABLE OF CONTENTS
Page Number
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INTRODUCTION
AUTHORIZATION
The Corps of Engineers• small hydropower study was authorized by
Congress in 1976. The small hydropower study was undertaken to determine
the feasibility of installing small hydroelectric systems in isolated
villages throughout Alaska. This feasibility study is being conducted as
part of that larger study.
SCOPE OF WORK
This report is limited in scope to the analysis of hydropower at
Scammon Bay. Other alternatives are currently being studied by the
AlasKa Power Authority. The information proviaed in this report is
preliminary; accurate measurements of the instream flow have only been
made since late July 1980. The proposed plan presented herein is oased
on the best information available; however, due to the limited data, the
conceptual design and resulting cost estimate are subject to change as
additional information becomes available during 1981. Project size may
be reduced if stream-flow is less than predicted.
BACKGROUND TO CURRENT STUDIES
In August 1979, the Alaska Power Administration, in conjunction with
the Alaska Village Electrical Cooperative (AVEC), visited 15 potential
hydropower sites located near villages served by AVEC. Of those sites
visited, Scammon Bay appeared to be the most feasible hydropower
project. As a result, the Alaska Power Administration recommended that
the Corps of Engineers pursue the feasibility evaluation under its small
hydropower authorization.
THE STUDY
The primary objective of this study is to determine the feasibility
of hydropower development at Scammon Bay and, if feasible, assist in
implementing the project at the earliest possiole date. The neea to
reduce the bush communities dependence on diesel fuel is imperative to
their future well being.
Federal funds to construct this project would require Congressional
authorization under existing regulations; however, Congress may change
this procedure and provide the Corps of Engineers a continuing authority
to build small hydropower projects. Pending legislation includes author-
ity which would allow projects up to 25,000 kW capacity to be constructed
by the Corps of Engineers. If this legislation passes, action could be
taken to construct economically feasible and environmentally acceptable
small hydropower projects in a timely manner.
COMMUNITY PROFILE
HISTORY
Scammon Bay is located to the north of the Askinuk Mountains in the·
Yukon-Kuskokwim Delta on the south bank of the Kun River, one mile from
the Bering Sea (Plate 1). In earlier times the village located at
Scammon Bay was known in Eskimo as "Mariak." The village was later named
after the nearby bay which honors Captain Charles M. Scammon, who served
with the Western Telegraph Expedition from 1856-1867. The name Scammon
Bay became commonly applied to tne village in 1951 when a post office of
that name was established.
SOCIO-ECONOMICS
Transportation
Scammon Bay is accessible by air, water, and winter trail. Transport
fuel and bulk supplies are barged to the community from June to
Septemoer. The Kun River serves approximately 60 privately owned noats,
providing transportation to fish and berry camps.
A 2,800-foot gravel airstrip north of the city enables daily
scheduled commercial air service. Principal air carriers include Sea
Airmotive, and Wien. Scammon Bay has approximately one mile of gravel
road for use by the few vehicles in town. Snowmachines, owned by nearly
every household in the community are the major form of transportation in
winter.
Fishing
The primary economic activity of Scammon Bay occurs during the
summer when most residents are involved in commercial fishing. As of
1978, the Yukon District had issued 40 gill net permits to Scammon Bay
residents. commercial species include salmon and to a lesser extent
herring. Herring are anticipated to become a larger portion of the cash
economy with the investment by the Alaska Renewable Resource Corporation
in the construction of approximately 10 herring fishing boats at Scammon
Bay. In addition to these commercial catches, non-cash landings include
whitefish, blackfish, needlefish, smelt, and tomcod.
Trade and Services
vear-rouna employment in the city is available through local
government and trade. In the trade sector, employers include the
airport, four minor stores and the general store. Some residents also
sell handmade grass baskets or ivory-carved jewelry and other handicrafts.
Government
Scammon Bay was incorporated as a second class city in 1967. The
seven member city council selects the town mayor and administrator. In
aoaition, the city ewploys a clerk, secretary/treasurer, police and
2
maintenence personnel. These positions are funded through the Comprehen-
sive Employment Training Act (CETA) program. Other government supported
employment sources include the Bureau of Indian Affairs school, the Rural
Parent-Child program, and seasonal firefighting for the Bureau of Land
Management.
Subsistence Activities
Income from the aforementioned activities is supplemented by
subsistence hunting and gathering and to some extent, assistance
payments. In addition to fish, residents of the area hunt walrus, seal,
geese, swans, cranes, ducks, loons, and ptarmigan. In the fall, various
types of berries such as blueberries, cranberries, and salmon berries are
harvested.
Population
In 1979 the population of Scammon Bay was 191. Census figures for
1970 show that the population is 100 percent native with median ages of
17.5 and 16.0 for males and females, respectively. Table 1 shows
population figures for Scammon Bay. The reported figures indicate an
annual growth rate of approximately 2 percent.
Year
1939
1950
1960
1970
1979
Employment Overview
TABLE 1
HISTORIC POPULATION OF SCAMMON BAY
Population
88
103
115
166
191
Table 2 shows employment in Scammon Bay for the year 1979.
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TABLE 2
SCAMMON BAY 1979 EMPLOYMENT BY INDUSTRY
Part Time Year Round
Gillnetting 40 _!/
BLM *
CETA 11
Airport l
BIA School 9
Retail 8
Parent-Child Program 2
Handicrafts *
TOTAL 40 31
Source:
Alaska Department of Community and Regional Affairs
1/ Based on number of gillnet permits only. Actual participation is
greater.
*Number Unknown
4
GENERATION FACILITIES
Prior to 1974 Scammon Bay was not associated with any formal
electric utility system. During this period most households either
utilized private generators or were not electrified. Like most bush
communities, the local Bureau of Indian Affairs (BIA) elementary school
had its own generating capacity. As a result of the informal system,
electric consumption records from this era are unavailable.
In 1974, Scammon Bay joined the Alaska Village Electric Cooperative
Inc. (AVEC), a nonprofit electric cooperative membership corporation.
AVEC is the State's largest single supplier of electricity to rural areas
and provides power to 48 communities throughout western Alaska. The
average population of AVEC supplied communities is approximately 300.
All AVEC power is diesel generated. The utility's diesel units at
Scammon Bay are summarized below.
1 -50 kW, 1,200 rpm, KATO (1971)
1 -75 kW, 1,200 rpm, KATO (1971)
50 kW
75 kW
125 kW
AVEC is currently in the process of modifying this capacity by
boosting each unit from 1,200 rpm to 1,800 rpm. The total capacity of
the system will thus be increased to about 175 kW (105 kW and 70 kW). In
addition to AVEC generation, the local BIA elementary school and high
school maintain standby generators. The specifications of these units
are summarized here.
High School
BIA School
1-100 kW,
1-35 kW,
1-25 kW,
Newage Stawford
Kohler
Kohler
100
35
25
160 kW
The recently acquired high school generator presently has very few
hours of operating time. The BIA units vary from 10 to 15 years in age.
Presently both schools are customers of AVEC, but the school generating
capacity is often needed for standby purposes.
5
ENERGY DEMAND
HISTORIC:
Since JOlnlng AVEC, Scammon Bay has participated in the cooperative's
record keeping system. Unfortunately, records were not kept dilligently
in the early years, resulting in incomplete and missing forms. In 1979
AVEC generation for Scammon Bay totaled 269,310 kWh with a peak load of
78 kW.
The total energy generation at Scammon Bay is unknown. The BIA's
generators are known to operate a significant proportion of the time, but
no records of output have ever been kept. For the purpose of this
report, it has been estimated that the BIA generator produces an
additional 15% above AVEC' generation. This would increase the combined
1979 AVEC and BIA energy generation to 309,700 kWh.
In adaition to the BIA school (three classrooms) and new high school
(6,500 sq. ft.), the community has a variety of public and residential
structures which comprise the electricity demand of Scammon Bay. AVEC
estimates that the recently constructed high school, will add approxi-
mately 35 kW to the system's peak demand. Public buildings include the
community center, the traditional council building, armory, clinic, post
office, Luther Aguchak Memorial Building, and two churches. Four stores,
several warehouses, a movie theater, and the AVEC building are also
located in the city. There are approximately 45 single family dwellings
in Scammon Bay; most are of wood-frame construction. Of these, 15 were
built in 1970 by th~ Alaska State Housing Authority. In all, about 60
structures are served by AVEC.
AVEC's total dependence upon diesel generation has resulted in ever
spiraling costs in recent years. Tne cooperative's base rate currently
stands at 40.8¢ per kWh. The extremely complicated accounting and
financing practices of this utility make the derivation of Scammon Bay's
generating costs difficult. The rate quoted above for instance, applies
to the first 75 kWh of residential use, a category many households fall
into. Consumption above this level is charged at about 75 percent of
this rate. Commercial rates, on the other hand, are 37.8¢ per kWh. All
rates include a 3.6¢ per kWh fuel surcharge. The fuel surcharge does not
fully reflect the fuel cost component of AVEC's rates. It is intended
strictly to anticipate rising fuel costs, thus protecting consumers
against abrupt rate increases.
The overall utility rates corresponding to these years are given in
Table 5. Rates for consumption above 75 kWh and commercial use have
remained roughly proportional to the present schedule.
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TABLE 5
AVEC RESIDENTIAL RATE 1975-1980 {75 kWh)
Year Rate (¢ per kWh)
1975 21.9
1976 22.8
1977 29.0
1978 34.2
1979 36.7
1980 40.8
For electrical generation, fuel prices have been the principal source
of rising costs. Tne average cost of diesel fuel delivered to AVEC
villages since 1973 is shown in Table 6.
Table 6
AVERAGE COST OF DELIVERED FUEL TO ALL AVEC VILLAGES 1973-80
Year cost ($/gal)
1973
1974
1975
1976
1977
1978
1979
1980
0.35
0.52
0.58
0.65
0. 72
0.78
0.97
1.33
Scammon Bay, which takes a small annual shipment relative to other
AVEC villages {20,000 gal.), experiences higher than average costs. The
price of diesel for Scammon Bay currently stands at $1.35 per gallon as
compared to $1.33 on a system wide basis. Regardless of this differen-
tial, Scammon Bay pays the same electrical rates as do other AVEC
villages.
FUTURE DEMAND
For this analsis a 1981 energy demand of 416,000 kWh is used. This
was derived by assurnming a 5 percent per year energy increase above
AVEC's 1979 generation plus an additional 15 percent generated by the BIA
generators. Additional generation to serve the high school is estimated
at 5 kW base load with an average demand of 25 kW during school hours.
This generated output is summerized in Table 7. ·
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Table 7
SUMMARY OF ESTIMATED 1981 GENERATION
(kWh)
AVEC *
BIA **
HIGH SCHOOL ***
TOTAL
* Estimated Community Need ** Estimated proportion generated by BIA
296,900
44,500
75,000
416,400
*** Estimated yearly High School load (served by AVEC or Standby)
No attempt has been made to project electrical energy needs beyond
1981. The on-going study being conducted by NORTEC for the Alaska Power
Authority should address these needs. Assumming future energy needs are
at least equivalent to the projected 1981 estimates, the proposed
hydropower project's feasibility should not be dependent on high future
energy forcasts.
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HYDROLOGY
Only one hydropower site is located close enough to Scammon Bay to be
potentially feasible for development at this time. This stream flows
through town and serves as the community water supply.
BASIN DESCRIPTION
The basin is within an area of maritime influence which is prevalent
over the Yukon-Kuskokwim Delta. Although the Askinuk Mountains are
adjacent to Scammon Bay, they are relatively small in height {1,000-2,000
foot) and create minor orographic changes in the climate. In general, the
area surrounding Scammon Bay is tundra covered, flat and marshy land with
oxbow lakes similar to other areas in the Yukon-Kuskokwim Delta.
STREAMFLOWS
The village has historically acquired its water supply from the creek
which flows from the Askinuk Mountains. In 1976 the Public Health Service
(PHS) built a corr1munity water system that treated the water with chlorine
and fluoride and installed a piping network. Although the village
utilizes a portion of the creek for water supply, there are no records of
the amount of streamflow which has actually occurred. During July 1980, a
water measurement structure (Parshall Flume) was installed to collect data
during the upcoming year and to verify the assumed streamflow values. As
this data becomes available, it will be possible to make final design
adjustments that may be warranted.
Based upon measured flows taken near the village and correlated to the
damsite, the discharge and energy estimates shown in Table 8 have been
made. The months of July, August, September, and October are actual
measured monthly average flows. The other monthly flows are based on the
current best estimates considering climatic conditions, known basin
characteristics, and conversations with the local villagers. Measurements
taken at the damsite and in town indicate that adequate residual flow will
be left for water supply purposes.
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TABLE 8
ESTIMATED MONTHLY ENERGY PRODUCTION
TIME DISCHARGE POWER ENERGY
(Months) (cfs) {kw) (kwh)
Oct 1. 50 46 34,000
Nov 1.25 38 27,000
Dec 1.00 30 22,000
Jan 1.00 30 22,000
Feb 0.80 24 16,000
Mar 1.00 30 22,000
Apr 2.00 61 44,000
May 10.00 *150 111,000
Jun 6.00 *150 108,000
Jul 2.00 61 45,000
Aug 2.00 61 45,000
Sep 1. 50 46 33,000
TOTAL 529,000
* Maximum capacity has been tentatively set at 150 I<W.
The project has been initially sized at 150 kW. With a single unit of
the type proposed, efficient operation will be possible over the range of
0.8 to 4.6 cfs. This should cover the majority of the flows availaole.
The turbine would only develop the installed capacity in May and June when
demand is relatively low, out any necessary size reduction during final
design should have little effect on the total usable energy output of the
project.
CLIMATE
The area has a maritime influence as indicated by its relatively
moderate temperatures and precipitation. The Askinuk Mountains have a
minor orographic influence on the climate at Scammon Bay such that the
various pressure systems approaching from the ocean or the Yukon-Kuskokwim
Delta would have a direct effect on the village. There are no glaciers at
the head of the stream which could effect the climate or the streamflow.
The nearest climatological station is located at Cape Romanzof Air
Force Station approximately 15 air miles away. Although Cape Romanzof is
at approximately the 435-foot elevation and has a Southwest exposure it
represents the best approximation of weather at Scammon Bay.
Temperature
Temperature data was collected from the "Climatological Data," National
Oceanic and Atmospheric Administration (NOAA) for the period of
1953-1978. Tne monthly maximums, minimums, and averages are illustrated
in Table A. The average temperature range during the summer and winter
respectively are 34° F to 49° F and between go to 31° F. Recorded
extremes are -26° F and 79° F.
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Preci itation
Precipitation data was also collected from NOAA records for the
period of 1953-1978. The monthly average, maximum, and maximum 24-hour
preciptiation are shown in Table A. The average monthly precipitation
ranges between 0.98 and 5.00 inches with an annual average of 25.45
inches. The maximum monthly precipitation for the period of record is
10.50 inches with the maximum 24-hour precipitation being 2.77 inches.
Snow
Snow pack data was collected from NOAA records for the same period as
temperature and precipitation. The average snowpack on the first of each
month with the standara deviation is illustrated in Table 9. Tne
standard deviation of the snowpack indicates that over the period of
record the snowpack nas varied considerably.
Wind
Wind data was obtained from the Arctic Environmental Information Data
Center through Mr. James Wise. It was also taken at Cape Romanzof AFS
and is illustrated in Table 10. The data indicates the prevailing wind
is from the northeast for all months of the year with the exception of
July and August when it is from the south-southwest. The mean annual
velocity is 15.6 mph while the maximum mean velocity for the year is 16.2
mph.
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TABLE 9
CAPE ROMANZOF
CLIMATOLOGICAL DATAl/
PRECIPITATION:l/ JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ANNUAL
AVERAGE 1.11 o. 98 1.25 . 9 7 1.28 2.13 2.95 5.00 4.62 2.39 1.56 1 • 21 25.45
MAX MONTH 4. 17 4.25 6.83 3.44 3.72 4.31 6.45 8.78 10.50 6.09 5.46 4. 14 10.50
MAX 24 HOUR o. 99 1. 15 1.20 0.90 o. 7 4 1.88 1.95 2. 77 2.09 1.34 1.97 1.30 2. 77
TEMPERATURE:
AVERAGE 12.9 9.7 13.5 20.7 34.4 43.3 49.2 49.2 43.7 31.1 22.6 12.8 28.6
MAXIMUM 49 48 46 60 63 72 79 73 63 60 43 48 79
MINIMUM -23 -26 -26 -12 3 25 31 33 23 4 -7 -23 -26
SNOW PACK: y
1-' AVERAGE 7.8 11.8 15.3 18.6 12.9 1.4 0.0 0.0 0.0 0. 1 2.9 5.9 N
STANDARD
0 EVIATION 6.8 9.7 14. 1 20.6 8.3 3.3 0.0 o.o 0.0 0.64 3.2 5.7
STATION INFORMATION: LATITUDE -61° 46' LONGITUDE -166° 03 1 ELEVATION -434 1
1/ From Climatological Data 1953 through 1978
2/ Rainfall in inches
}_/ Snow pack (including snow and sleet) on the ground. in inches, on the first of each month.
TABLE 10
CAPE ROMANZOF WIND DATA
(MPH)
SUBJECT JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ANNUAL
Prevailing
Wind, Mean
Velocity 19.2 20.2 1 7 .o 16.9 13.8 11.8 9.6 11.8 11.8 14.3 16.8 17.8 15.6
Direction NE NE NE NE NE NE ssw ssw NE NE NE NE NE
% Time 16.9 21.4 1 7. 1 15.2 18.0 12.6 14.7 13.0 16.6 19.7 18.6 21.3 16.2
Maximum
Mean
Velocity 21.0 20.2 17.9 18.0 14.5 12.9 11.4 11.8 14. 1 15.7 1 7. 4 18.7 16.2 ......
w
Direction NNE NE NNE NNE NNE NNE NNE ssw NNE NNE NNE ENE NNE
% Time 14.2 21.4 14.5 14.0 9.9 11.7 7.8 13.0 16.5 15.3 11.3 8.6 12.6
DESIGN FEATURES
Hydroelectric power would be developed from the spring fed stream,
which originates south of Scammon Bay and flows through the village (See
Plate 2). The stream flows from approximately elevation 800 to elevation
50, where it merges with the main channel of the Kun River. A small
reservoir would oe excavated upstream of a rock-fillea gabion dam which
would be constructed at elevation 596, about 3,500 feet from the town
proper. A penstock would run from the intake structure of the dam to an
aboveground powerhouse located near the village's school. An open
channel tailrace approximately 50 feet in length would be excavated from
the powerhouse to the main stream channel. Several viable alternatives
for the installation of the penstock and for the type of pipe to be used
are presented here. Further study of these alternatives will be
completed prior to final design of the Scammon Bay Hydropower Project.
WATERWAYS
An 8-foot high dam would be constructed from standard manufactured
galvanized steel gabions filled with rocks taken from the reservoir
excavation and from the stream itself (Plate 3). A cut-off wall would be
constructed of sack crete, at the center of the dam. This cut-off would
extend approximately 9 feet below the existing ground surface, and its
top would be flush with the top of the dam at elevation 600. The dam
would extend about 50 feet across the stream gully and would include a
spillway with a 10-foot long weir which is 3 feet lower than the top of
the dam.
A drop box type intake structure with a top elevation 596 would be
prefabricated of corrosion resistant steel, with a trashrack located
either on top or at the upper siaes of the box. The trashrack would be
made from a standard heavy duty steel grating. The bottom of the
reservoir would be sloped toward the stream to prevent rocks and other
debris from accumulating around the intake box. Reservoir excavation
woula be limited to elevations below 598 with a minimum of 1 on 3 slopes
for all embankments.
PENSTOCK
Two alternatives were studied for the installation of the 12-inch
diameter penstock and three types of pipe were considered for conveying
water from the reservoir to the powerhouse. For both alternatives, th~
invert of the penstock at the intake structure is at elevation 593, 4
feet below the minimum pool elevation 597, and 1 foot above the finished
bottom grade of the reservoir at elevation 592. A sluice gate would be
installed to regulate the flow through the penstock and for emergency
operation. The penstock would be placed on an average 13.5 percent slope
whether above or below ground construction is used. Under Alternative
No. l, the penstock would be buried about 2 feet below existing grade. A
trench would be excavated and backfilled as required. The penstock would
be anchored and supported as required. Penstock Alternative No. 2 would
consist of a partly buried pipe, about 100 feet in length near the dam,
14
and the rest would run aboveground, supported on piers and anchored as
required. The exposed portion of the penstock would be insulated for
thermal protection. A steel penstock is found more suitable for
aboveground installation because it would be more durable against natural
disaster or vandalism.
For both alternatives, the penstock would cross the stream at
approximately 550 feet downstream of the dam. The minimum working
pressure for the penstock would be at least 250 psi ana the thickness of
the shell would be 10 ga. minimum for steel and 0.1875 inch for
reinforced plastic pipes. Three viable options for the types of penstock
pipe were considered: a standard welded steel pipe; a spiral weld lock-
seam pipe; and a reinforced plastic mortar (RPM) pipe. Initial economic
evaluation indicated that the "RPM 11 pipe was the most inexpensive in
material ana handling costs. This particular pipe is also lightweight
and highly corrosion resistant; however, it is susceptible to vandalism
when installed aooveground. The final selection of the type of pipe
would be made at a later design stage. Therefore, in this analysis, all
three alternatives are being addressed for general feasibility. They
will be evaluated further, with more serious consideration and emphasis
on performance applications in Alaska. For cost estimating purposes,
buried spiral welded pipe was used.
POWER PLANT
The penstock would connect to a valve upstream of the turbine in the
valve room located within the powerhouse. The powerhouse would be
located at elevation 100, and would be built on concrete slab. The
finished floor elevation of the slab would be about 4 feet above the main
stream water level. Three sites for the powerhouse were con-
sidered but geological findings proved that two of the sites are not
suitable due to potential flooding and/or soil creep.
An open channel tailrace would be excavated below the powerhouse. A
small energy dissipater structure would be located at the ena as near as
possible to the mainstream channel to prevent erosion of the
embankments.
Powerhouse Oescri ion
The equipment would be housed in a small lO'xll' structure consisting
of a concrete draft tube and equipment floor slab. The structure will be
prefabricated steel rather than the concrete block and wood as shown in
Plate 4. Ventilation would be provided by a wall mounted fan. Double
doors for ease of equipment removal are proposed. The generator is not
intended to be fire protected. Plate 1 shows the transverse section and
plan of the powerhouse.
15
Turbine
The turbine would be a "standardized•• horizontal axis impulse or
Turgo impulse turbine with one or two nozzles, one of which would be
adjustable.
The turbine would operate at 1,800 rpm and would be directly coupled to
the generator shaft. A jet deflector would be provided for rapid diver-
sion of the water from the wheel at load rejection. A valve would
automatically close slowly to prevent overpressure in the penstock. The
turbine would be specified to discharge from 0.8 to 4.6 cfs while
operating at 460 feet net head.
Arrangements utilizing Francis Turbines and pumps operating as
turbines were also investigated; however, because of the wide flow
variation, multiple units would be required thereby increasing the cost
of the mechanical and electrical equipment. Also, the use of pumps as
turbines would result in lower average operating efficiencies. Prior to
the final selection of the turbine type, a review of applicable types
will be made. Shown on the drawings is a single jet Turgo Impulse
Turbine.
Generator
The generator would be a synchronous type, rated 150 kW (188 kVA at
0.8 p.f.) 1-Phase, 60Hz, 120/240 Volt, 1800 rpm, provided with a drip
proof guarded enclosure, and have a 80° c temperature rise (over 40° c
ambient) capable of 10 percent overload.
Excitation System
The excitation system would consist of a brushless (rotating
rectifier) exciter with a saturable transformer, automatic voltage
regulator. This system would be provided as part of the generator.
Generator Circuit Breaker
·The generator circuit breaker would be furnished as part of the
generator package.
Unit Control and Protective Equipment
The control and protective equipment would be furnished as part of
the generator package.
Station Service Equipment
The station service equipment would consist of a 120/240 volt
distribution panel to supply lighting, outlets, and other miscellaneous
loads.
Low Level Alarm
A low level alarm system at the intake structure would be utilized to
shut thetsystem down should water levels drop to a point where air may
enter the penstock.
16
Transmission System
The project power would be transmitted through a local distribution
system. The connection to the existing distribution system would be by
overhead line through a wall mounted weatherhead fitting.
17
ENVIRONMENTAL IMPACTS
Fish and wildlife resources would not be significantly affected by
sma l1 hydropower development on the stream running through Scammon Bay.
The small spring fed stream does not support resident or anadromous fish
and there are no wildlife species dependent on the project area.
Although waterfowl and shorebirds are abundant in the immediate area,
there are no known resting, nesting or feeding occurring in the area of
the proposed project's influence. The U.S. Fish and Wildlife Service
stated the greatest impact of the project could be erosion caused by
mechanized equipment moving on the steep slopes underlain by permafrost.
Removal of the thin protective vegetative layer could allow permafrost to
thaw resulting in ground subsidence and subsequent creation of deep
gullies from erosion. With construction occurring within the stream
gully where permafrost is not present, erosion would be minimal.
,
18 '
COST ESTIMATE
Two different schemes including above ground and buried penstocks
were considered for Scammon Bay. In all, three penstock materials were
considered for use: steel welded, spiral welded, and rmp {plastic) pipe.
The costs for the various schemes and alternatives ranged from a low of
$990,000 to a high of $1,250,000. Additional data and design is required
to determine the best alternative for the site before a final decision is
made. The cost estimate was based on a buried spiral welded penstock.
The following cost estimate does not include land acquisition which is
assumed to be local responsibility.
ITEM DESCRIPTION
MOB & PREP WORK
INTAKE WORKS
Reservoir Excavation
{common)
Intake Structure
stainless steel
drop box
{3' wide x 6'
long x 6' deep)
Trashrack
Std Steel Grating
18 SF
DAM AND SILL {50 FT)
Excavation
(common)
Concrete
Reinforcement
Gabion {rock)
(Std Manufacture)
6' long x 3'
wide x 1' deep
Backfi 11
{gravel)
Steel Gate
(std sluice gate)
12" dia.
{low head type)
PRELIMINARY COST ESTIMATE
QUANTITY
1
70
400
4l5
55
50
2,500
200 .
15
1
19
UNIT
LS
CY
LB
LB
CY
CY
LB
EA
CY
LS
UNIT PRICE
$
20.00
8.00
2.00
20.00
600.00
l. 30
200.00
20.00
TOTAL
$300,000
l, 400
3,200
830
1' 100
30,000
3,250
40,000
300
3,000
ITEM DESCRIPTION QUANTITY UNIT UNIT PRICE TOTAL
Riprap 15 CY 110.00 l '650
WATERWAYS
Penstock, 12"dia.
3,500 LF Spiral weld 61,250 LB l. 60 98,000
Ring stiffeners
exp. anchors,
anchor supports 4,288 LB 2.00 8,576
ANCHOR
& THRUST BLOCKS
Concrete 12 CY 600.00 7,200
Excavation
(common) 3,500 CY 5.00 17,500
Backfi 11
(common) 3,400 CY 3.00 10,200
POWER PLANT
Powerhouse LS 163,000
TAILRACE CHANNEL
Excavation {common) 45 CY 10.00 450
Riprap 15 CY 110.00 1, 650
TRANSMISSION LINE
{hook-up to exist
city line)
wood poles, cables
transformer, etc. l LS 30,000
SUB TOTAL COST = $721,306
20% Contigencies = 144,694
CONTRACT COST :;: $866,000
Engineering & Design = 70,000
Supervision & Adminis-
tration = 74,000
TOTAL PROJECT COST $1,010,000
20
ECONOMIC ANALYSIS
This evaluation is based exclusively on economic benefits that can be
derived from hydropower development. Evaluation of the Scammon Bay pro-
posal was accomplished by comparing the benefits to accompanying costs.
The benefit value of hydroelectric power is measurea by the cost of
providing the equivalent power from the most likely alternative source
{diesel). The evaluation has been conductea in accordance with methods
requested oy the Alaska Power Authority.
PROJECT COSTS
Interest During Construction
As the proposed development would oe constructed in one season~
interest during construction would not enter into project costs.
Annual Costs
The Alaska Power Authority has specified that under an inflation free
economic analysis a discount rate of 3 percent is appropriate. By
applying the capital recovery factor associated with a 3 percent interest
rate and a 50-year economic life, the investment cost can be transformed
into an average annual fixed cost. Adding operations, maintenance, and
replacement costs, a total annual cost is established for the purpose of
determining comparability and feasibility.
Operation, Maintenance, and Replacement Costs (OM&R)
An OM&R cost of $8,000 annually has oeen estimated for the Scammon
Bay hydropower project. This figure does not include AVEC's existing
charges.
Tot a 1 Ave rage Annu·a 1 Sys tern Costs
The average annual costs for the various plans of development are
based on a 3 percent annual interest rate and a 50 year economic life.
These costs also reflect transmission tie in facilities, access {but not
land aquisition), replacement costs, annual operation and maintenance,
ana other associated project costs.
PROJECT BENEFITS
The benefit value of hydroelectric power is measured by the cost of
providing the equivalent power from the most likely alternative source.
Diesel generation is currently the most likely alternative for Scammon
Bay.
21
Power Values
The project under examination would displace diesel currently
utilized for power generation. Thus, Scammon Bay's current power costs
(as can be best approximated) will be employed to access the costs of
continued diesel generation. As of 1980 AVEC's per kWh costs divided as
follows:
Fuel
0~
Depreciation
Taxes
Insurance
Interest
AVEC Generation cost per kWh
excluding administration and
transmission costs
16.93
12.66
.25
.04
.03
.06
29.97¢
As measured by the base rate~ administrative and transmission costs total
7.3¢ per kWh. Adding a fuel surcharge of 3.6¢ per kWh yields the
original rate of 40.8¢ per kWh. As mentioned, this rate applies only to
the first 75 kWh of residential use. Although industrial and larger
residential users enjoy lower rates, the base rate will be considered
representative of Scammon Bay's power costs.
Credit for Energy and Capacity
Opportunities 'exist for displacing energy which could alternatively
be produced by existing thermal plants. The value of thermal energy that
would be displaced is dependent on fuel costs and other variable costs.
Benefits for this project are based solely on displaced diesel fuel
costs. Savings resulting from reduced O&M expenses may occur but were
not possible to estimate at this time. Since only secondary energy would
be produced, the project cannot be assigned credit for capacity.
The total potential energy output of the selected project is
estimated at 529,000 kWh annually. This compares to an estimated demand
of 416,400 kWh for 1981. By examining seasonal demand and the streamflow
data appearing in the hydrology section of this analysis, it was
determined that approximately 300,000 kWh of hydropower is useable.
Although growing loads woula allow increasing proportions of hydropower
to be utilized, this preliminary report will assume 300,000 kWh of
useaole hydropower annually.
22
Fuel Cost Escalation
As mentioned in the passage concerning historical fuel prices, the
cost of this component of thermal power has consistently outstripped all
other costs over the past decade. Given the present outlook of continued
fuel price escalation, the Alaska Power Authority has requested that the
economic evaluation be based on increasing fuel costs. An annual (real)
growth rate of 3.5 percent in fuel prices over a period of 20 years was
specified. This variation has been implemented by adjusting the fuel
cost component (excluding fuel surcharge) of AVEC's base rate. The
projected per kWh diesel cost for each year of the project life was
discounted to the present at the appropriate rate. The resulting factors
were then summarized to develop a present worth factor. The effect is a
shift. in AVEC's fuel cost component from 16.9¢ per kWh to 27.9¢ per kWh.
Comparison of Annual Costs and Benefits
Based on criteria set forth by the Alaska Power Authority (discount
rate of 3 percent, fuel cost escalation of 3.5 percent, and a 50-year
economic life), the project would provide annual benefits of $84,000 at
an annual cost of $47,000.
23
FINANCIAL ANALYSIS
The 3 percent discount rate specified by APA does not take inflation
into account. The two major effects of inflation on capital investment
are, 1) the actual cost of funds will greatly exceed 3 percent, and 2)
investments with high fixed costs and low variable costs are more
"inflation proof". The Alaska Power Authority has therefore requested an
examination of the selected projects feasibility under a 7 percent annual
inflation rate, with 10 percent financing for 30 years and fuel cost
escalation of 10.5 percent for 20 years. The results of this analysis
are graphically displayed and are based upon the calculations shown
below. Note that the costs being compared are strictly generation
costs. Administrative and transmission costs, as well as taxes and
insurance, have been netted out of AVEC's current generation to draw an
even comparison with hydro.
Comparative $/kWh cost of Diesel and Hydro Generation at Scammon Bay for
Initial Year of Analysis
AVEC Cost of Diesel Generation
excluding fuel surcharge, adminis-
trative and transmission costs,
taxes, and insurance
Fuel
O&M
Interest & Depreciation
Estimated Cost of Hydro Generation
excluding fuel surcharge, adminis-
trative and transmission costs,
taxes, and insurance
Fuel
O&M
Interest & Depreciation {@ 10%)
24
16.9
12.7
.3
29.9
0
2.7
28.6
29.9¢
29.9¢
31.3¢
31.3 31.3¢
.
Unite. d States Army
Corps of Engineers
.. _ Servmg tht' Arm~
... &n·ing rtv-Noti()ft
Alaska District
Comparative Cost of
Hydro Vs. Diesel Power -
Assuming 7% Inflation
2.00r---.-------r------r-----r------,.----/---:..~/
/
END OFF .JEL COST
ESCALATION AT 3.5% _
.oo~---~----+---+----4--~-----+-
1981 1985 1990 1995
YEAR
25
2000 2005 2010
FIGURE 1
Based upon the previously outlined assumptions of inflation and fuel
cost escalation, the proposea project would oe less expensive than·diesel
by the end of the first year of operation. Although the analysis as shown
in the previous grapn indicates the relative costs of hydro versus diesel,
the total system cost should lie somewhere between the two graphs. This
is due to the inability of the hydrosystem to meet all system aemands
thereby forcing the use of diesel as a supplement.
26