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"RELOCATION OF HYDROELECTRIC PROJECT
AT ATKA, ALASKA"
Prepared for:
ALASKA POWER AUTHORITY
by:
NORTHERN TECHNICAL SERVICES
August, 1983
NORTHERN TECHNICAL SERVICES
ANCHORAGE, ALASKA
August 1, 1983
Alaska Power Authority
334 West 5th Avenue
Anchorage, Alaska 99501
NORTHERN TECHNICAL SERVICES
750 WEST 2ND AVENUE, SUITE 100 • ANCHORAGE, ALASKA 99501
(907) 276-4302
Attention: Ms. Margaret Lesniak
Re: Draft Report in Fulfillment of Contract Number CC-08-2266
Amendment No. 2, Relocation of Existing, Non-Functional
Hydroelectric Plant at Atka, Alaska
Dear Ms. Lesniak:
Please find attached a draft report on the feasibility of re-
locating the existing, non-functional hydroelectric generation
plant on Atka Island to a site on Chuniisax Creek.
In fulfillment of. the amendment contract between Northern
Technical Services and the Alaska. Power Authority, a reconnais-
sance survey of Chuniisax Creek was completed by personnel from
van Gulik & Associates, Inc. and Northern Technical Services and
a draft report prepared by van Gulik & ~ssociates, Inc.
There are several locations which satisfy the basic require-
ments, but one, with intake at Falls D, is clearly superior to
all the others in most respects. It requires the least in
additional materials and has the easiest access in terms of
moving the powerhouse equipment to the site. It appears
superior in terms of ease of contruction of the powerhouse
foundation and tailrace. Lastly, it meets what we understand to
be the optimum design characteristics of the turbine. It does,
however, place the powerhouse between the first and second falls
Ms. Margaret Lesniak
Page 2
within ~n area reached by some anadromous fish. The information
in your report on Aquatic Environment leads us to conclude the
impact would be minimal and we, therefore, suggest the project
be installed at that location.
Preliminary cost estimates are included. The lower estimate is
on the basis of the village constructing it utilizing its own
labor resources~ the other reflects the cost of labor if
contracted.
Should the concerned agencies conclude that reduction of the
flow in the upper third of the reach below Falls B would cause
unacceptable impact, the alternative is to place the intake at
Falls F with the power plant in the vicinity of Falls B. The
powerhouse location is less desirable and might require some
foundation exploration, and the pipeline length would be about
1,800 feet, nearly twice the length of the other. There is some
potential for impact on land-locked Dolly Varden.
Sincerely,
NORTHERN TECHNICAL SERVICES
William D. Pyle
Partner
WDP/pgh
082-011
Attachment
RELOCATION OF HYDROELECTRIC PROJECT AT ATKA, ALASKA
Reconnaissance of Chuniisxax Creek was accomplished on 8 and 9
June 1983 for the purpose of evaluating relocation of the existing,
non-functional hydro-electric plant to some site on that creek.
The existing turbine was designed to operate with a head of
103 feet and with a flow of 10 cubic feet per second (cfs),
generating 50 Iav at that flow. Levels were run to establish the
relative elevation of pertinent topographic features. Most
distances were obtained by stadia but some were chained as well to
check the stadia accuracy.
During the reconnaissance two flow measurements of the stream
were made; flows were in excess of 20 cubic feet per second. The
stream has more than enough water to satisfy the flow requirement
except perhaps for the driest part of the year which might occur in
some part of June and July and again in winter months when the
discharge might be limited by colder weather. It would appear that
for perhaps three months of the year the flow ~ight drop to about
10 cfs but during the remainder of the year would be in excess of
the design flow requirements of the turbine.
There are five site possibilities which can provide an
elevation difference in excess of the head of 103 feet for which
the turbine was designed. In four of these, the intake structure
would be located at the sixth falls upstream (Falls F) and
powerhouses located. at various sites downstream. One configuration
could develop a head in excess of the design head with an intake
structure located at the fourth upstream falls (Falls D). The
first four would require pipelines ranging in length from about
1,500 feet to about 1,800 feet. The fifth would require a pipeline
of about 950 feet.
Two-possibilities with an intake at Falls D could develop
about 81 feet and 88 feet of head with pipelines of about 500 feet
and 790 feet, respectively. These would produce power in the range
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of 30-35 KW. An eighth configuration, which provides considerably
less elevation differential but which would be an attractive option
for further analysis if a new turbine/generator/pipeline were to be
considered, would simply utilize all the head and flow available at
Falls D. The available head is about 35 feet and while sufficient
hydrologic information is not yet available to estimate the annual
power production, it would appear that 40 to 50 KW could be readily
developed. This site would be the simplest to develop of all sites
examined.
Fisheries
The following is based on an analysis of the aquatic
environment in Chuniisxax Creek performed in 1982.
Pink salmon represent the most significant anadromous fi~~
species in the creek. Their habitat is restricted to the stream
below the first falls (Falls A) and would not be affected by hydro
development.
Silver salmon were observed below Falls A and a few have been
reported to have surmounted that falls and reached the second. A
development with power plant located below Falls B would have some
small impact. Chum salmon were not observed in the stream but
villagers have reported that chum have been know to spawn there.
They are capable of surmounting the first falls, however, their
preferred spawning habitat is much the same as the pinks and hydro
development would consequently have little impact.
Dolly Varden trout inhabit the stream from the mouth to above
the area under consideration. Those above the second (Falls B) are
landlocked and would be impacted on somewhat depending on the
particular site configuration. They were observed throughout
the area up to the seventh falls and in the small streams tributary
to the main stream. Hydro development would likely have minimal
impact on this fish population.
Anadromous Dolly Varden would be affected by any development
with powerhouse located downstream of Falls B. The impact would
depend upon the amount of water diverted to the powerhouse as
compared to the total amount available and on the timing of
spawning in relation to the periods of low flow when the diversion
might result in the stream being significantly dewatered for a
short distance. The length of reach involved would be a maximum of
about 350 feet.
Description of Alternatives
The alternative most nearly matching the turbine design
parameters and requiring the least amount of new pipe (if any) for
the water conveyance would involve an intake at the elevation of
Falls D, a pipeline about 930 feet long placed in a generally
straight line (about 60 degrees east of south) , crossing the stream
to a powerhouse location on the left bank. This location would
place the tailrace about 300 feet downstream of the second falls
(Falls B) , roughly a third of the reach between the first and
second falls.
Installation at this site will develop the full potential the
existing power plant is capable of producing. It should have
minimal impact on fisheries. This site is the most advantageous of
possible sites on the stream from the standpoint of accessibility
for getting the generating equipment to the site. The unit can be
broken down into its smallest components, moved by skiff to a
location approximately 500 feet from the site and moved by some
vehicle such as Nodwell or winched and carried, in stages, over to
the site.
The point to which a line of levels was run is about 105 feet
below the elevation of the intake location. Between that point and
the elevation of the stream an additional 15 to 20 feet of head can
be obtained, depending on the location chosen for the powerhouse.
The turbine designer indicated that the generation with this
particular turbine would be optimum at about 125 feet, and this can
be approached at this location.
Some probing and test excavation would be necessary to
determine the bes·t location for the powerhouse foundation and the
tailrace.
Variations on this alternative would provide for the same
intake but with the powerhouse located on the right bank at Falls B
or downstream opposite the location described above. These would
provide about 80 to 88 feet of head, somewhat less than the design
head for this particular turbine.
The alternatives with intake located at Falls F could develop
about 110 feet if terminated at Falls B and in excess of 140 feet
of head if the powerhouse were located in the same place as
described above in the first alternative. These would require 1500
to 1800 feet of pipe. They offer no particular hydraulic
advantage. They present some additional construction difficulty
since material and equipment would have to be moved farther
upstream.· The location offering 140 feet of head is not practical
to develop using the existing turbine. Those alternatives with the
powerhouse at or near Falls B would have the least potential impact
on anadromous fish habitat.
Conclusions
The first alternative described above is ideally suited for
installation of the generating equipment and penstock material
presently located at Atka. The available head approaches the
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optimum for this particular turbine. There should be more than
enough flow available most of the time. The site requires the
least overland conveyance of the equipment and construction
supplies.
Should it be determined that this installation would cause
unacceptable adverse impact on anadromous fisheries as a
consequence of reducing the stream flow in the reach from Falls B
to the powerhouse location by the amount diverted for generation,
the most productive alternative would be to install the intake at
Falls F, and the powerhouse on the north bank of the stream near
Falls B. The conveyance pipeline could be located north of the
stream and would not require any crossing of Chuniisxax Creek. It
would need to be elevated slightly through a low area where it
would cross a small tributary stream. A minimum of 900 feet of
additional pipe would be required and to reduce head losses it
should be of a larger diameter than the 12" on hand. This larc;rer
diameter pipe would make· up the upstream half of the pipeline.
The suggested location and the alternate are shown on the
attached location map (Figure 1).
Transmission
The project would require about 4,000 feet of transmission
line to reach the central generating building in the village. It
should be buried and, to reduce line losses, include a step-up
transformer at the powerhouse and a step-down at the village. Step
up to 480 volts should be sufficient. The line should be three
wire with neutral; #4 - 5 kv should be sufficient.
Intake
The intake structure would be located just above the fall of
Falls D. Since there will be no attempt to regulate the stream
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flow with storage, a low over-flow diversion weir sufficient to
properly submerge the intake should suffice. Water will be flowing
over the weir most of the time. Because of this and the need to
securely anchor and form the intake, the weir and intake should be
of concrete. The intake should be screened and provided with a
gate for closure of the pipe. The slide gate installed at the
existing dam near the village can probably be adapted to the site.
Because of the likelihood of ice backup at the intake and possible
damage to the penstock, the short length of pipe from the weir to
the falls where the penstock leaves the stream should probably be
of polyethylene or corrugated metal pipe.
Powerhouse
The general configuration of the powerhouse at the existing
installation is satisfactory for a site on Chuniisxax Creek. The
precise location should be chosen with a view to maximizing t~~
head and minimizing the amount of concrete needed over rock for the
footing. Care should be exercised to insure the tailrace will not
erode. Some probing and hand test excavation will be needed in
order to select the most appropriate spot.
Pipeline
If the existing pipeline is ,carefully salvaged it should all
be usable at the new site. Some 800 feet is installed and about
140 feet of unused pipe is available.
The pipe from the intake to the point where it leaves the
stream at the falls should probably be polyethylene or HPC to
reduce possibility of ice damage to the pipe. PVC should be
satisfactory for the remainder. A relief valve should be installed
near the intake to permit dewatering of the pipe.
Two trestles would be required for support. The first would
be for the sake of hydraulic efficiency and would support the pipe
from the falls across a gully to a saddle about 250 feet away. The
average height would be about 15'. The alternative would be to
install the pipe on a curve rather than a straight line. About 80
to 100 feet of additional pipe with several elbows would be
required but the timber supports could be much simpler with the
pipe essentially following the contour around to the saddle. The
simpler approach is recommended.
The other trestle is unavoidable. It would cross Chuniisxax
Creek to the left bank powerhouse location. The pipe would
approach the creek bank at ground le~el then follow the steep bank
downward to the trestle at an elevation slightly higher than the
loc~tion chosen for the powerhouse on the other bank. The trestle
would support the pipe from the right bank to the powerhouse on the
other side. The construction should be perhaps a bit more
substantial than the supports constructed for the stream crossing
just below the dam at the existing installation because of the
possibility of icing.
In most respects, installation of the pipeline itself from
intake to powerhouse is not significantly different from the
existing installation at the site near the village.
Turbine/Generator
The existing equipment can be fully utilized on Chumiisxax
Creek. The suggested location provides about the optimum head for
this specific turbine and the stream should have adequate flow most
of the time.
In the intervening period since the equipment was acquired and
installed, a central generation system has been installed at the
village: and the hydro plant, which previously would have operated
independently, will now be operating in parallel with the diesel-
driven system. This interface needs careful attention. If this
installation proceeds, provision should be made for a visit to the
village by a representative of the vendor (Hydro-Watt} and the
installer of the diesel-driven system (Pacific Diesel} , to insure
that the speed controller and other equipment are correctly
installed and can be operated with assurance by the village. It is
particularly important that the speed control immersion units be
properly installed.
Construction/Installation
The villagers are likely fully capable of constructing the
weir and intake, installing the penstock, constructing the
powerhouse and installing the transmission line and step-up and
step-down transformers. they should be guided by a competent field
engineer in locating and at critical times in the construction of
the powerhouse and the weir and intake structure.
Consultation should be arranged with the vendor who supplied
the generation equipment to insure that the system is properly
integrated with the diesel-driven generation and that any
additional protective devices or equipment are considered and
installed as appropriate. For the hydro installation to be
efficient in displacing the use of diesel fuel, it should operate
as a dependable base load plant. Some care should be taken to
insure that it will do so.
MAJOR COST ITEMS
1. Power house (10 cy foundation@ 800 plus bldg) $12,000
2. Diversion & Intake (5 cy @ 800)
3. Penstock (Existing pipe.
Timbers & Labor@ SO/ft.)
4. Transmission Line and Transformers
(0.76 mi @ 90,000)
5. Mob/Demob
6. Contingencies @ 25%
(Possibly some additional pipe)
7. Consultation, Test & Startup
Engineering Assistance
$ 6,000
$10,000
Subtotal
4,000
47,500
68,400
131,900
100,000
231,900
60,000
(291 ,900)
Say $300,000
16,000
Total $316,000
Say $320,000
If villagers can construct project using own labor resources
with engineering assistance and consultation:
MAJOR COST ITEMS
1. Powerhouse (move existing powerhouse
plus 10 cy con)
2. Diversion & Intake
3. Penstock (assume 500 feet requires support
every 10 feet and materials @ 100 each support)
4. Transmission & Transformers (wire $3.5/ft.
Portland: assume $10 to Atka. Transformers 2
@ $2,000
5. Contingencies @ 20%
(Possibly some additional pipe)
6. Consultation, Test & Startup
Engineering Assistance
$ 6,000
$10,000
Subtotal
Total
$10,000
4,000
5,000
44,000
$63,000
14,000
77,000
16,000
$93,000