HomeMy WebLinkAboutHydropower Development Potential of Kenney Lake, Alaska 1983KEN
001 DEPARTMENT OF THE ARMY
ALASKA DISTRICT CORPS OF ENGINEERS
POUCH 696
ANCHORAGE. ALASKA 99506
REPLY TO
ATTI[NTloN OF:
February 9,1984
Plan Formulation Section
Mr. Larry Crawford
Executive Director
Alaska Power Authority
335 West Fifth Avenue
Second Floor
Anchorage, Alaska 99501
Dear Mr. Crawford:
RECEIVED
i ~g lL: 1984
ALA.S:(:, PC'.'!~R !!JHlORITY
Enclosed for your -information is a copy of the Corps of
Eng i neers I 1 etter report on the hydropower deve 1 opment poten-
tial of Kenney Lake, Alaska. The project does not appear to be
economically feasible at this time.
If you have any questions, please contact Mr. Ron Maj, of
our Plan Formulation Section at 552-3461.
Sincerely,
IQ/ (nQL){)~ ~'~Rrf-r.1
Moore /
t"Cm...Chief, Engineering Divlsion
Enclosure
· ~. . .. ,
INTRODUCTION
Hydropower Development Potential
of
Kenney Lake, Alaska
October 1983
The evaluation of small hydroelectric systems was authorized by
a 1 October 1976 United States Senate Resolution, which directed the
U.S. Army Corps of Engineers to determine the feasibility of
installing small prepackaged hydroelectric units in isolated Alaskan
communities.
In 1982, a regional inventory for small hydropower projects in
Southcentral Alaska was completed for the Alaska District by Ebasco
Services Incorporated. This inventory analyzed more than 30 sites,
recommending nearly 20 for more detailed examination, including the
Kenney Lake site. The Kenney Lake site was one of six selected by
the Alaska District from this group for field reconnaissance and
additional analysis. Ebasco did not conduct any field
reconnaissance at the Kenney Lake site during the Southcentral
inventory.
During 9-11 August 1982, an interdisciplinary Alaska District
team cond~cted a field reconnaissance ofa potential s~all
"hydropm'ler project site near the small community of Kenney Lake in
the Tonsina River Valley. The potential site is located across the
Tonsina River from Kenney Lake on a small unnamed tributary south of
the Tonsina (see figure 1 and 2). This area is approximately 6
miles southwest (upstream) of the confluence of the Tonsina River
with the Copper River and approximately 30 miles southeast of
Glennallen.
Presently, the Copper Valley Electric Association (CVEA) serves
the Kenney Lake area. Based on the August 1983 edition of "Alaska
Electric Power Statistics" by the United States Department of
Energy, of the total installed nameplate capacity of 22,104 kW;
12,000 kW are produced by hydropower, 7,304 kW by diesel, and 2,800
kW by gas turbine. A total net generation of 35,941 MWh was
generated in 1982.
ENVIRONMENTAL SYNOPSIS
Principal identified environmental resources in the vicinity of
the site and the stream are Coho salmon, Chinook salmon, and Dolly
Varden. The lower reaches of the stream are used as rearing habitat
by juveniles of those species. Chinook salmon were observed
spawning at the juncture of the subject stream and the Tonsina
River. Juvenile salmon were collected upstream of observed spawning
sites. Ttle upstream extent of salmon spa\·ming, juvenile rearing
habitat, and resident Dolly Varden distribution (if any) was not
· ,
determined. The fish populations involved are believed to be small
and it appears that impacts to identified fish populations and
habitats could be mitigated to within acceptable limits, possibly
with minor adjustments to optimum project design and operating
regimes. The stream undoubtedly contributes macroinvertebrates,
algae, and other food-web components to the Tonsina River. Minor
losses of these organisms would occur from project operation, but
these losses could not be regarded as significant to other systems.
Moose, black bear, brown bear, and a variety of furbearers in
the canine, weasel, and rodent families occur in the area.
Reconnaissance-level biological surveys indicate that project
construction and operation would have little adverse effect on these
animals, provided that construction and operation access could be
achieved without road construction. If an access road were
required, significant project impacts and secondary impacts from
improved access would likely occur to local wildlife populations.
No endangered or threatened species were observed or identified
in a brief literature search. No cultural resource surveyor
inventory has been conducted.
HYDROLOGY
Description of the Area. The unnamed stream has a drainage area of
7.8 square miles. Waters~ed elevations range from about 2,400 to
6,000 feet msl. Significant snowpack exists in the higher
elevations (above 5,000 feet msl), especially on the north and west
slopes, but no glaciers exist in the study area. Stream slopes in
the area average about 650 feet per mile with a maximum slope of
about 860 feet per mile. Drainage area ground slopes range from
essentially horizontal to nearly vertical. The lower elevations are
covered by dense stands of willow, alder, and birch, while the
intermediate elevations are covered with tundra plants and, where
surface water is available, stands of alder. The higher elevations
are either bare or covered by tundra plants. The stream on which
the dam would be located consists of a series of cascades and
waterfalls from the headwater area to the proposed powerhouse
location. In general, the stream is about 12 feet wide with depths
of up to about 1.5 feet between cascades and up to about 4 feet in
the energy holes at the cascades. Site investigations indicate that
stream stage fluctuations have been very minor in the past and the
stream does not appear to have sediment problems above the damsite.
Design Flows. Stage and/or discharge data in the vicinity of Kenney
Lake, Alaska, are very limited. The only gaging stations which have
existed in the area are the Little Tonsina River near Tonsina (USGS
gage number 15207800, drainage area = 22.7 mi2), Squirrel Creek at
Tonsina (USGS gage number 15208100, drainage area = 70.5 mi2), and
Tonsina River (USGS gage number 15208000, drainage area = 420 m;2).
Of these three stations, only the Tonsina River at Tonsina gage is
presently in operation. The period of record mean annual flows for
each of these three streams is given in Table 1.
Water Year
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
Table 1
Mean Annual Flow (cfs/mi 2 )
Little Tonsina Rv.
(O.A. = 22.7 mi~l
0.99
0.79
1.44
1.45
2.81
1.09
Squirrel Crk.
(O.A. = 70.5 mi~)
0.51 -
0.38
0.62
0.31
0.28
0.38
0.59
0.47
0.35
0.49
Tonsina River
(O.A. = 420 mi~)
1.90 -
1.77
2.04
1.40
1. 51
1. 71
2.05
1. 35
1. 60
2.01
1. 58
2-.82
1. 58
1.80
2.31
The Tonsina River unit flows were obviously higher than those of
the other two stations, especially the Squirrel Creek station, but
they were not extremely different from the Little Tonsina River
flows. The preliminary design flows for the Kenney Lake hydropower
project were developed by multiplying the mean monthly Tonsina River
flows in cubic feet per second per square mile by the Kenney Lake
drainage area in square miles. This resulted in flows slightly·
higher than what would probably have occurred at the Kenney Lake
damsite.
ENERGY USE
Records for 1982 indicate that CVEA generated approximately
35,941 MWh. Currently, CVEA purchases energy generated by
hydropower from the Alaska Power Authority during the summer. This
time period corresponds with the time period in which the Kenney
Lake project would operate.
Energy Analysis. The HEC program "Hydur" was used to compute the
energy pl'oduction for a variety of project sizes. An overall plant
efficiency of 0.86, a design head of 800', and a minimum operational
capacity of 0.4 times the design capacity were used as part of the
"Hydur" input data. The results are summari zed below.
r-~-.-
Plant Size (kW)
300
700
1,500
2,000
4,000
Average Annual Energy (MWh)
1,470
2,696
5,153
5,561
6,709
Benefit Analysis. At this level of analysis, it was assumed that
the total average annual energy of the hydropower system less an 8
percent transmission loss would be equal to the usable energy. Two
categories of benefits were determined for each turbine size;
displaced existing hydropower and displaced transmission costs. An
existing hydropower generation cost of 3.6¢/kWh (Copper Valley
Electric Association, Inc.) combined with a transmission cost of 7.5
¢/KW results in a total energy displacement cost of 11.1¢/kWh.
Shown below are benefits derived for each of the turbine sizes.
Usable Displaced Displaced
Plant Size Energy Existing Transmission
(kW) (t~Wh ) Hldro~ower Cost Total
~O 1,350 49,000 $101,000 $150,000
700 2,480 $ 89,000 $186,000 $275,000
1,500 4,740 $171,000 $356,000 $527,000
2,000 5,120 $184,000 $384,000 $568,000
4,000 6,170 $222,000 $463,000 $685,000
Cost Analysis. A preliminary cost estimate was derived for each of
the project sizes. 'Shown is a summary of project features.
-
Plant Size Dam Height Penstock Di a.
(kW) (ft. ) ( in. )
300 11-14
700 12 18
1,500 13 26
2,000 14 30
4,000 16 48
The cost estimates included the following items: rockfill dam, a
4,900-foot steel penstock, a 5-mile access road to the powerhouse, 3
miles of transmission line, the powerhouse plus associated features,
intake structure, helicopter support during construction, site
. preparation, mob and demob, a 20 percent contingency, 12 percent for
E&D and S&A; and interest during construction based on a 2-year
construction period. This cost estimate does not include O&M
costs. Costs were amortized using an interest rate of 8 1/8 percent
and a 50-year project life. Shown below is a summary of the
estimated costs.
Plant Size (kW) First Cost Total Costs Annual Costs
300 $ 6,954,000 $ 7,516,000 $ 623,000
700 $ 7,507,000 $ 8, 114,000 $ 673,000
1,500 $ 8,717,000 $ 9,310,000 4 772,000
2,000 $ 9,202,000 $ 9,946,000 $ 824,000
4,.000 $12,568,000 $13,584,000 $1,126,000
EVALUATION
To derive the optimum project size and the net benefits, annual
costs were compared against annual benefits. In addition, a cost
per kWh was derived by dividing the project annual cost by the
project's equivalent usable energy. The results are summarized
be10 ... J.
Plant Size Annual Annual Benefit/Cost
(kW) Costs Benefits Net Benefit Ratio $/kl~h --300 $ 623,000 $150,000 -$473,000 0.24 $0.46
700 $ 673,000 $275,000 -$398,000 0.41 $0.27
1,500 $ 772,000 $527,000 -$245,000 0.68 $0.16
2,000 $ 824,000 $568,000 -$256,000 0.68 $0.16
4,000 $1,126,000 $685,000 -$441,000 0.61 $0.18
The above analysis indicates that none of the turbine sizes
evaluated is economically feasible. Plant sizes versus net benefits
were graphed to determine the optimum project and to determine if
any feasibi1e units exist within the range selected (Graph A). The
optimum project size was found to be a 1,500 kW system with a
benefit/cost ratio of 0.68 which would produce negative net benefits
of $245,000. .
CONCLUSIONS
The project would produce power during the warmer months so that
power could be fed into CVEA grid sup~lementing existing hydropower
generation. It appears that all pO't-ier produced by the hydropower
project could be used in the CVEA system. During the I·Jinter, no
power would be generated due to ice, and the power flow would be
from the CVEA diesel generators to the Kenney Lake area. It can be
concluded that, even witfl the optimistic assumptions made on the
streamflow estimates used in the above analysis, no feasible project
size exists.
RECO~lt'!ENDA nONS
It is recommended that no further Corps of Engineers studies of
hydropower development at Kenney Lake be undertaken at "this time.
DETAILED COST ESTIMATE (1,500 kW Plan)
ITEM/DESCR I PTION QUANT ITV UNIT UNIT PRICE TOTAL
MOB &. DEr~OB1/ 1. s. $1,600,000
DAM & INTAKE STRUCTURE
Excavation 820 c.y. 50 $ 41,000
Excavation, Rock (Spillway) 540 c.y. 50 27,000
Concrete, Dam 50 c.y. 800 40,000
Rockfi 11 800 c.y. 30 24,000
Steel, Rebar & Misc. 6,900 lbs. 2· 13,800
Intake 1 ea. 70,000 70,000
Total Dam and Intake Structure $ 215,800
PENSTOCK
26" dia. 1/4" Steel 5,000 1.f. 492..£/ $2,460,000
Concrete Supports 300 c.y. 800 240~000
Total Penstock $2,700,000
POWERHOUSE
Structure ea. 163,000 $ 163,000
Turbine Generator ea. 640,000 640,000
Accessory Electrical ea. 258,000 258,000
Auxilliary Sys. & Equip. ea. 39,000 39,000
Switchyard ea. 50,000 50,000
Tota 1 Pm·/erhouse $1,150,000
.. TRANSMISSION LINE
14.4 KV Line 3 mile 100,000 $ 300,000
Clearing 8.4 acres 5,000 42,000
Total Transmission Line $ 342,000
UNIMPRUVED DIRT ROAD
Access Road 8 mile 54,250 $ 434,000
48" CMP 54 lof. 98 5,300
Clearing 11.5 acres 5,000 57,500
Total UnilTIproved Dirt Road $ 496,800
SUBTOTAL $6,504,600
Contingency ( 20%) $1,300,900
Engineering & Design ( 8%) $ 520,000
Supervision & Administration ( 6%) $ 391,500
TOTAL FIRST COST $8,717,000
1/ includes site prep, helicopter support for 6 months, mob & demob.
2/ includes cost of steel, excavation, installation, bends
ANNUAL COSTS AND BENEFITS
Investment Cost (incl. IDC)
Interest and Amortization (8-1/8% @ 50 yrs)
Annual Benefits
Displaced Existing Hydropower
Displaced Transmission Cost
Total Annual Benefit
Benefit-Cost Ratio
Net Annual Benefit
Dam Height (ft.)
Penstock Length (ft.)
Pertinent Data Sheet
Penstock Diameter (in.)
Transmission Line Length (mile)
Access Road Length (mile)
Design head (ft.)
$9,310,000
772,000
$ 171,000
356,000
$ 527,000
0.68
-$245,000
13
4,900
26
3
5
800
To GlennaUen
\
\Copper Center
.....
rransLaSka
Pipeline
To Valdez
PROPOSED
SITE
Sea Ie
10 0
~-J--J ---Mile I
10
!
20
I
I :
Wrangell-Saint Elias National Park and Preserve
ALASKA DISTRICT
KENNEY LAKE
Figure 1
~~ h
. ..... ..... -..... ~:!~!£~I~~ ---Edgerton Hig way
........... ~ .-----= -• 1100~ __
Tonsina River ~~~-
Transmission
Line
Powerhouse
Penstock
Dam
2000:3000 4000 o 1000 ! FEET I
Figure 2
KENNY LAKE
Small Hydropower
o
-100
-0
0
0 -200 •
T-
{J} -
en
+" -300
'to-
Q)
C
Q)
CO -400
+"
Q) "Z m -500
G)Z
"""Z Q)m -g.<
l>1 »
"
o 3500 4000 500 1000 1500 2000 2500 3000
Unit Size [kW)
m
V~ldez and Copper River B~sin
Energy Usage Update
With Emphasis on Kenney Lake
Si~e the -Electrical Power for Valdez and the Copper River Basin-
study ~as completed in March 1981, significant chanQes have taken place
in the Valdez-Glennallen area. Factors influencinQ demand increases and
option~ to meet those increases have changed. The-cancellation of the
propos~d oil refinery by the Alaska Petrochemical Company (ALPETCO) has
great 1:, reduced demand over that previously estimated and the
instit~tiona1 problems associated with the proposed pressure reducing
turbin~ have appeared to all but eliminate that as a generating
a1te r n3tive. This is particularly true because the Prudhoe Bay field's
economic life will be ending in the mid-1990's and the prospect of
additional finds in the area are much bleaker with a dry hole at Mukluk
well in 1983.
Th·~ following briefly examines what has happened regarding energy
projEc~ions, the impact of Solomon GulCh, and conclusions on hydropower
in the area (Kenney Lake and Allison Lake).
Load FJrecast -Reality vs. Projections
Th2 load forecast deemed most likely in -E1ectri~1 Power for Valdez
and th~ Copper River Basin-indicated additional diesel generation may be
needed after the year 2000 (Figure C-2). This forecast was based on the
assumption that ALPETCO would build a refinery in Valdez. At the time
the report was being finalized, ground breaking had begun for the
project. Shortly thereafter ALPETCOcance11ed their plans to build the
refinery. It then appeared that Dow-Shell would go ahead with a
petrochemical complex at Valdez. However, due to the recent oil glut,
all plans have been put on hold indefinitely. Therefore, load growth has
been s~bstantia11y slower than originally assumed. The following table
summarizes the gross generation from the Solomon Gulch hydropower plant
and for diesel plants at Glennallen and Valdez.
Gross Generation (MWh)
Diesel 1/ Hydro 1/
Year Glennallen Valdez Solomon GulCh Total
1980 20,065 25,006 45,071
1001
",VI 19,598 26,750 46,348
1982 12,651 3,315 35,969 51,935
1983 12,205 3,801 36, 189 52,195
1/ Source: Copper Valley Electric Association
2/ Source: Operator at Solomon Gulch
4
The ~CtUll' 9f'nerat i on reportp( ~hove compllres wi th the "revi sed APA It and
the "low growth" scen~rios rerorted in "Electrical Power for Valdez and
the Copper River Basin" as fOllows.
Actual·, Revised APA % Difference Low Growth t: Difference
Year ~ GWh~ ~ GWh~ Actual vs. Estimated (GWh~ Actual vs. Estimllted
1980 45. 1 47.9 -5.8 47.9 -5.8
1981 46.3 52.0 -11.0 50.1 -7.6
1982 51.9 55.5 -6.5 52.5 -1. 1
1983 52.2 61.0 -14.4 55.0 -5. 1
As can be seen by the preceding summary, the actual demand has fallen
short of the 10\0: growth forecast by approximately 5 percent to date,
while falling over 14 percent behind the revised APA forecast, which was
considered "most lik.ely" at the time the report was published.
Based on the above and the assumption that Allison lake hydropower
will be the next addition, it appears that the time when additional
energy is neec!ec' to displace diesel in the sunmer months will be
significantly 1cter than 2000.
Solomon Gulch EnerQY Producticn
Since coming on line in J~~uary 1982, Solomon Gulch has contributed
significantly to decreasing the reliance on diesel fuel in the
Valdez-Glennallen area. For t~e first 2 years of operation, the system
has carried the entire utility's load from mid-May to late October. In
late October when Solomon Gulch stops spilling, the transmission line
from Valdez to Gelnnal1en is de-energized. From then until mid-May,
Glennallen is solely served by diesel-fired generators while Valdez is
served by a diesel-hydropower combination until late March or April when
the reservoir "bottoms ouL" Valdez is then served solely by diesel
until mid-May when runoff begins to fill the reservoir. According to Mr.
John Hunter, the operator at Solomon GulCh, the commencement of runoff is
so sudden ~nd fast that once t~e reservoir begins to fill, the
Valdez-G1enn~11en transmission is energized and Solomon can again carry
the full load. In the first 2 years of operation, the reservoir was
filled and began spilling on 19 July in 1982 and 11 July in 1983. It
continued to spill until 18 October 1982 ~nd 19 October 1983.
Although a detailed record of the inflows and spill Quantities were
not readily avai-!able, Mr. Hunter estimated that, based on the amount of
water available, Solomon Gulch could run at full capacity (12 MW) from
May to October with no impact on winter flows because of the large
quantity of water spilled. This compares to a current peak. demand (which
occurs in winter) of approxima~ely 9 MW. The peak. summer demand is
estimated to be about 2 MW les;.
5
Conclusion
Loads have not materialized as anticipated in tIP Valdez-Glennallen
area due primarily to the cancelled development of the ALPETCO oil
refinery. These reduced loads, combined with Solom)n Gulch's capability
to produce an abundance of energy during the summer months makes
development of a project that only produces energy in the summer months
(like Kenney Lake) unattractive in the Valdez-Glcnnlllen area. Any
benefits to be derived from displaced diesel fuel 1:1 the summer months
could not be claimed until possibly 2010 or later. Therefore, the
eva 1 u at i on of Kenney Lake (or any other sma 11 hydro;lower proj ect in the
area) should be measured against hydropower at Solo~on Gulch rather than
diesel.
A project with great reservoir requlation to di~place some of the
16 GWh annually that are still produced by dies€i generation is needed in
the Valdez-Glennallen area. Because the pressure reducing turbine no
longer appears feasible due to the institutional problems encountered to
date and the ever-Shortening life of Prudhoe Bay, tne most reasonable
alternative appears to be developmpn1 ~t Allison Lake, as previously
proposed.
15
'0 ---l
5
1
......
3: ....
~ -
FIGURE C-2 SOLOMON GULCH ALLISON LAKE
APA REVISED PROJECTION
ALLISON LAKE
SECONDARY-----
ENERGY
PROJECTED ENERGY
DEMAND FOR
THE YEAR 2000
so-: v-·~ ~r::\~ -.,,"""". ,.....,. . ';" ,.... .. ~ .. '=~=-~r;
o ~~--~~i-----,Ir-----rl----~I----~j----~ir-----rl~~~'----~l------rl--~~I----~
J F M A -M J J A SON 0
7-