HomeMy WebLinkAboutGunnuk Creek Hydroelectric Project Reconnaissance Report - Sep 2015 - REF Grant 7071025Gunnuk Creek
Hydroelectric Project
Reconnaissance Report
Prepared for:
Inside Passage Electric Cooperative
P.O. Box 210149
Auke Bay, AK 99821
Prepared by:
F)l
HDR Alaska, Inc.
2525 C Street
Anchorage, Alaska 99503
September 20I5
Gunnuk Creek Hydroelectric Project
Reconnaissance Report
Table of Contents
ExecutiveSummary....................................................................................................................................3
1 Introduction........................................................................................................................................
4
1.1 Site Visit....................................................................................................................................4
2 Background Information...................................................................................................................5
2.1 Existing Development ..................
... 5
2.1.1 Hatchery .......................................................................................................................
5
2.1.2 Water Supply Dam.......................................................................................................
5
2.1.3 Water Supply Intake.....................................................................................................
6
2.2 Previous Studies........................................................................................................................ 6
2.3 Fish Resources...........................................................................................................................7
2.4 Water Rights..............................................................................................................................
8
2.5 Land Ownership........................................................................................................................ 8
3 Hydrology..........................................................................................................................................10
3.1 Existing Data...........................................................................................................................10
3.2 Streamflow Extension.............................................................................................................11
3.3 Flow Duration.........................................................................................................................
12
4 Project Alternatives..........................................................................................................................13
4.1 Alternative 1 — Expansion/Rehabilitation of Existing Hydroelectric Project ..........................
13
4.2 Alternative 2 — Mid -Basin Run -of -river Project.....................................................................
16
4.3 Alternative 3 —Storage Project................................................................................................
17
5 Permitting/Licensing.......................................................................................................................19
6 Energy Generation...........................................................................................................................
20
6.1 Assumptions............................................................................................................................
20
6.2 Results............................................................................................ ...............21
6.3 Sensitivity Analysis.................................................................................................................22
7 Cost Estimates..................................................................................................................................
22
SEconomic Evaluation.......................................................................................................................
23
9 Conclusions and Recommendations...............................................................................................
24
Appendix A — Geotechnical Reconnaissance Report
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Gunnuk Creek Hydroelectric Project
Reconnaissance Report
Executive Summary
The Inside Passage Electric Cooperative (IPEC) received a State of Alaska Renewable Energy
Fund Grant to perform a reconnaissance study of the hydroelectric potential in the Gunnuk Creek
drainage basin, near Kake, AK. Currently all of Kake's electrical energy is supplied by diesel
generation. A new hydroelectric project on Gunnuk Creek could provide the community with a
source of renewable energy.
This study looked at three possible options for developing hydropower. Of these, only one has
significant potential. The preferred project would be an expansion and rehabilitation of an
existing hydroelectric project (7kW) that makes use of the existing water supply dam and
hatchery facilities. Costs and construction risks are minimized because the dam and intake
facility have already been constructed, and no new transmission lines or access roads are
required.
The new project would have an installed capacity of 500 kW and would produce approximately
1,600 MWh annually, or 55% of Kake's average annual requirements. The project would save
an estimated 6.2 million gallons of diesel fuel over its 50 year design life. The estimated
development cost is $5.5M and has a corresponding benefit/cost ratio of 3.2. Additional benefits
of the project would be increased reliability of the water supply to the hatchery should it re -open
and the reduction of 62,400 tons of harmful CO2 emissions over its life.
It is estimated that the project could become fully operational within 15-24 months. The next
steps in project development are:
- Initiate discussions with ADF&G regarding requirements for instream flow in the bypass
reach.
- Develop joint use agreement with the State of Alaska for the use of the hatchery water
supply and powerhouse site. Replacement of the pipeline and stabilization of the route
has the added benefit of increasing the reliability of the hatchery water supply.
- Initiate discussions with the Southeast Alaska Land Trust to confirm project is consistent
with the conservation easement that is in place.
- Final design of the project to include surveying the plan and profile of the pipeline route,
soils exploration along pipeline route and preparation of design plans and specifications.
Page 3
Gunnuk Creek Hydroelectric Project
Reconnaissance Report
1 Introduction
The Inside Passage Electric Cooperative (IPEC) contracted with HDR Alaska, Inc. to evaluate
the potential of developing a hydroelectric project on Gunnuk Creek to service the village of
Kake, Alaska. Kake is located on Kupreanof Island approximately 100 air miles southwest of
Juneau and 40 miles northwest of Petersburg. It lies at approximately 56' 58' N latitude and
133' 56' W longitude and is nestled in the Tongass National Forest.
The scope of work defined for this project included:
• Data collection and review of previous studies;
• Field reconnaissance;
• Evaluation of hydrology and collection of streamflow data;
* Development of conceptual project layouts;
• Estimation of energy production and project costs;
• Permit and licensing assessment;
• Preparation of this reconnaissance report.
This report should be considered a high-level overview intended to identify projects which
demonstrate a basic measure of feasibility and to eliminate projects that have evident fatal flaws
from an engineering or environmental perspective; this report also provides information to
enable IPEC to determine the economic feasibility of a project and to pursue funding for future
phases of the project.
1.1 Site Visit
A visual field reconnaissance was conducted on June 25, 2014 by a senior project engineer and a
geotechnical engineer. The field reconnaissance consisted of an aerial flight of the Gunnuk Creek
drainage via a helicopter chartered from Juneau. The purpose of the reconnaissance was to begin
to evaluate the feasibility of constructing a small hydroelectric project to service the community
of Kake, and to identify locations of project features. Specific objectives of the aerial
reconnaissance were to:
• Identify potential area for diversion/intake construction.
• Assess possible powerhouse locations.
• Assess suitability for buried- or above ground penstock
• Review site access for construction and operations and maintenance.
• Review route for potential transmission line and tie in locations.
The reconnaissance throughout Gunnuk Creek focused on two areas that had been identified as
potential project locations: middle Gunnuk Creek for a run -of -river project, and in upper Gunnuk
Creek for a dam/storage project. A separate geotechnical report memorandum included in
Appendix A describes the field reconnaissance and provides an overview map of the two areas
visited.
An additional site visit was made January 13, 2015 to assess the lower portion of Gunnuk Creek
and consisted of an inspection of the water supply dam and existing penstock route to the
hatchery.
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Gunnuk Creek Hydroelectric Project
Reconnaissance Report
2 Background Information
2.1 Existing Development
Existing development in the Gunnuk Creek basin is described below.
2. L I Hatchery
A fish hatchery is located approximately 2000 ft. upstream of the mouth of Gunnuk Creek on the
west bank. The hatchery was constructed in the late 1970's and produced pink, chum and coho
salmon until 2013. Water was diverted from the water supply dam (described below) and
conveyed to the hatchery through a 2,150-foot-long, 10-in diameter HDPE pipeline. A 7 kW
hydroelectric generator is housed in a powerhouse just upstream of the hatchery and acts as a
pressure reducing valve.
In 2013 the hatchery operation became insolvent and went into bankruptcy. The facilities are
now owned by the State of Alaska and the hatchery is not operational. The Northern Southeast
Regional Aquaculture Association (NSRAA) is the most likely candidate to acquire the hatchery
and resume operations.
Figure 1- Gunnuk Creek Hatchery (NSRAA photo)
2.1.2 Water Supply Dam
The City of Kake has long taken its water supply from Gunnuk Creek. In July 2000 the City's
timber crib water supply dam was breached by a log during a flood. Through a Congressional
authorization the U.S. Corps of Engineers was directed to construct a new water supply dam.
The dam was also to include provisions for future hydropower expansion. Construction of the
new dam was started in 2005 and completed in 2007. The dam is readily accessed from existing
roads.
The dam is a concrete gravity structure and forms a 2.1 acre reservoir. The spillway is at
elevation 89.0 frnsl and is 42-feet wide. Between the two spillway bays is a low level outlet for
flushing sediment deposits during high flows. The intake includes trashracks, fish screens with
automatic cleaners and provisions for both water supply and hydroelectric pipeline connections.
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Gunnuk Creek Hydroelectric Project
Reconnaissance Report
Figure 2 - Existing Dam on Gunnuk Creek
2.1.3 Water Supply Intake
When the original timber crib water supply darn failed, the City established a temporary water
supply intake in Alpine Lake, high within the Gunnuk Creels basin. Upon completion of the new
water supply dam, the City used the facilities to pump water uphill to their water storage tank.
Excessive pumping costs prompted the City to revert back to the Alpine Lake system which runs
by gravity. That system is still in use today.
2.2 Previous Studies
The potential for hydroelectric power in Kake, and specifically within Gunnuk Creek, has been
the subject of previous assessments, including:
• Preliminary Appraisal Report, Hydroelectric Potential for Angoon, Craig, Hoonah, Hydaburg,
Kake, Kasaan, Klawock, Klukwan, Pelican, and Yakutat, Prepared by Robert W. Retherford
Associates, Anchorage Alaska for the Alaska Power Authority, 1977.
• Tyee-Kake Intertie Project, Detailed Feasibility Analysis, Final Report volume I Prepared by
EBASCO Services Incorporated for the Alaska Power Authority, March 1984.
• Evaluation of the Hydroelectric Potential Near Selected Sealaska Communities; Prepared by
Alaska Power & Telephone, 2005.
• Gunnuk Hydro Reconnaissance Report 1 /1512014, Prepared by Christensen et al. 2014.
Retherford's preferred development would utilize two earth filled dams and a 14,500 AF
reservoir in the upper basin, a 2800 foot -long penstock and a 1.8 MW powerhouse located near
tidewater. In 1979 the Retherford concept was reviewed by Harza Engineering for the Alaska
Power Authority and subsequently dropped in favor of the Cathedral Falls project. More
recently Gunnuk Creek has been looked at by the Sealaska Corporation and Christensen
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Gunnuk Creek Hydroelectric Project
Reconnaissance Report
Associates. Given the estimated size of the impoundment darns necessary, the 1977 plan has
been largely dismissed as uneconomical.
The 1984 EBASCO report discusses the potential for a run of the river project at Gunnuk Creek
to meet some of Kake's energy needs. The 1984 arrangement would utilize the original water
supply dam and follow the route of the previous wood stave penstock and water line to the fish
hatchery.
In 2005, the Sealaska Corporation conducted a feasibility study to determine the potential
sustainability of small hydroelectric projects on Southeast Alaska native lands. The report
presents potential modifications to previous hydroelectric project layouts for both the Gunnuk
Creek and Catherdal Falls drainages. The 2005 report discusses the potential of a powerhouse
being sited at the hatchery for maximum generation (-500 kW), as well as a smaller project (25-
50 kW) that would be sited in the vicinity of the existing dam. The 2005 report did not evaluate
cost but did recommend a detailed feasibility study be conducted.
The most recent reconnaissance -level investigation of the hydropower potential around Kake
identifies a two -phased approach for small hydroelectric projects. The reconnaissance report,
based on field and desk studies, was initially completed in 2013 and revised in January 20141
(Christensen et al. 2014). Phase 1 is described as a run -of -the -river design estimated to meet
more than half of Kake's annual electrical load. The study identifies the top of the canyon,
located approximately 2.7 miles inland of Kake, as a potentially feasible intake site (elevation
330 feet above mean sea level (MSL). This layout would require, at minimum, a 10-ft high
impoundment structure and approximately 2.75 mile penstock. Phase l was identified as the
most cost-effective approach.
The recent study evaluated an additional project to supplement Phase I production during the
low flow periods. Phase 2 would create a 141 acre reservoir to cover low flow periods so that the
project could meet the remainder of Kake's annual electrical load. Under Phase 2, a 50-ft by 350-
ft dam would be required to create the reservoir. Christensen estimated the annual mean flows to
the reservoir as 13.5 cfs, and identifies the presence of an out -of -basin stream that could
potentially provide an additional 9 cfs to the project. The study recommends that additional
stream gaging, land -based surveys for design work and a more detailed cost -benefit analysis be
completed for Phase 2.
Complete references can be found on the Alaska Energy Data Inventory website
www.akener invento .or .
2.3 Fish Resources
The Alaska Department of Fish and Game (ADF&G) Anadromous Waters Catalog (AWC)
identifies Gunnuk Creek (AWC code: 109-42-10040) as providing habitat for pink salmon
(Oncorhynchus gorbuscha), chum salmon (O. keta), coho salmon (O. kisutch), and steelhead (O.
mykiss) from its mouth to a point about one mile upstream from tidal influence, at the base of the
Gunnuk Creek dam (ADl~&G 2014a). The dam prevents the upstream migration of fish. Neither
' The 1/15/2014 study was conducted by staff from the Sustainable Southeast Partnership, the Kake Community
Catalyst, and the Southeast Alaska Conservation Council.
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Gunnuk Creek Hydroelectric Project
Reconnaissance Report
the AWC nor the ADF&G Alaska Freshwater Fish Inventory (AFFI) provides fisheries
information for Gunnuk Creek or its tributary streams upstream of the dam (ADF&G 2010b).
While no fish distribution data were available, the presence of resident forms of Dolly Varden
(Salvelinus malma) and/or cutthroat trout (O. clarki) upstream of the falls is probable.
2.4 Water Rights
Water from the Gunnuk Creek drainage is the primary source of drinking water for the residents
of Kake. The City of Kake has a certificate of appropriation (ADL 43611) for up to 5 cfs from
Gunnuk Creek with the point of diversion at the Gunnuk Creek dam. Current water consumption
is estimated at less than I cfs (0.65 MGD). The intake is located at Alpine Lake which is high up
within the Gunnuk Creek basin.
The City of Kake also has a permitted water right (LAS 11970) for 12 cfs for the purpose of
hydroelectric generation. This permit was granted 06/02/1989 and has never been perfected. A
stipulation of this permit is that the first 11 cfs of flow must remain in Gunnuk Creek to support
downstream habitat.
Additionally, the Kake Nonprofit Fisheries Corporation has two water rights totaling 2.5 cfs
(ADL 102406, LAS 118/75) with the point of diversion being the Gunnuk Creek dam. The
hatchery also has a seasonal appropriation to withdraw 2.5 cfs at the hatchery but this would not
affect any hydroelectric alternative. With the hatchery currently closed, it is unclear how long
these water right permits could remain in affect.
2.5 Land Ownership
The majority of lands in the Gunnuk Creek watershed are owned by Seaiaska Regional
Corporation, followed closely by the Kake Tribal Corporation. Other land owners include the
state of Alaska, the United States Forest Service (USFS) and the City of Kake as shown in Figure
3.
Page 8
KAKE LAND EXCHANGE - 2000
L.. + f�
Gunnuk Creek Hydroelectric Project
Reconnaissance Report
Current Land Ownership
Swte w Alaska
. City of K4ke
.. - Kake Tribal Cc>,gnofion
sealaska Cnrpowinn
e USDA Forest Service (USFS)
&change Lands
Kake Trihal (KTC) Lands
❑KTC land to City of Kakr
Anal - 1430
KTC land - Cor s"don
Em=cnt to SEAL Tmi
Actea - 1127
USFS Lando
Jemiy Ctmk • Land Sekctcd
by the Stair ofAlaxka io KTC
Acres - 1389
0
z
SM1alnka Caiporanon -
ir'atural lirsouxes lkpartm�nt
Figure 3 - Gunnuk Creek Land Ownership
Conservation easements have been granted to the Southeast Alaska Land Trust for large ,parcels
of land throughout the Gunnuk Creek drainage. The Lower Gunnuk Creek Watershed Protection
Project was a result of petitioning in 1995 by the people of Kake to protect the integrity of
Gunnuk Creek. Under the agreement and aided by federal legislation, land was conveyed to the
City of Kake. Subsequently, conservation easements were attached to those lands and to the
remaining Kake Tribal Corporation land within the watershed. Conservation easements include
an approximate 1,120-acre parcel in the lower reaches of the Gunnuk Creek drainage, and a
1,430-acre parcel farther upstream. While ownership of the Gunnuk Creek hatchery assets was
recently transferred to the state of Alaska, the land is located within the easement boundaries.
Per the terms of the conservation easement,
"Maintenance, renovation or replacement of water lines and power lines and
electrical utilities on the Property is allowed. The construction and maintenance
of dams and power lines and electrical utilities within the watershed is allowed.
Any plans for construction, remodeling or reconstruction of waterlines, dams or
power lines shall be submitted to SEAL Trust for review and approval to ensure
that they are consistent with the Purpose and Conservation Values. "
This provision included in the easement would seem to indicate that new development could be
allowed on lands covered by the easement. However, a legal opinion on this matter would be
needed. Such an opinion is beyond the scope of this report.
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Gunnuk Creek Hydroelectric Project
Reconnaissance Report
3 Hydrology
Gunnuk Creek has a drainage basin of approximately 16 mi2 on Kupreanof Island in Southeast
Alaska. Much of the basin is composed of relatively broad valley floors between hills ranging in
elevation up to 2,200 ft. The basin includes a small lake, and no glaciers. About 2 mi. above the
mouth of the creek, it enters a steep narrow canyon for a mile before emptying onto a fan -like
coastal plain where it flows through Kake.
3.1 Existing Data
The U.S. Geological Survey (USGS) operated a continuous strearagage (15087565) on Gunnuk
Creek from September, 2005 through September, 2008. From September 1, 2005 to September 1,
2007, the gage was located about '/ mile downstream from a dam on Gunnuk Creek used for
public and fish hatchery water supply. The drainage area for this gage is 15.4 mi2. Control for the
stage -discharge rating was a natural cobble riffle (USGS Station Analysis, from the files of the
Alaska Science Center, Water Year 2007). On September 1, 2007, the streamgage was moved to
just upstream of the dam, using the dam spillway as the stage -discharge control (USGS Station
Analysis, from the files of the Alaska Science Center, Water Year 2008). The average annual
flow during the recording period was 97 cfs. The average monthly flows for this gage are shown
in Figure 4.
180 -
H 160
w
u
140
,Q 120
T
100
C
8�
m 60
A
40
a
20
0
Gunnuk Creek Hydrology
Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep
Figure 4 - Gunnuk Creep Average Monthly Flow, WY 2005-2008
At both locations, winter temperatures occasionally form ice on the stream., causing backwater
that affects the stage -discharge rating. During these periods, mean daily discharge was estimated
from nearby streamgages. Freezing temperatures throughout the basin result in extreme low
flow at times in the winter. However, low flow periods can occur in any season. Mean daily
discharge was less than 10 W/sec at least once in every month except September, April, and
May. High flows in Southeast Alaska are commonly caused by fall and winter storms. Spring
snowmelt can cause periods of higher than average flow in April and May, but that rarely
produces high peak flows.
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Gunnuk Creek Hydroelectric Project
Reconnaissance Report
The Environmental Assessment prepared for the replacement of the City's water supply dam
references flow data collected from the hatchery during operations and cites an average annual
flow of 68.1 cfs. We were unable to obtain this data in order to review what was being measured
or how the data was obtained. Therefore, it is not used as part of this report.
3.2 Streamflow Extension
Three years of continuous site specific streamflow data is unusually good in remote Alaska, but
still might not be adequate to assess the long-term streamflow characteristics. In Alaska, seasonal
streamflow trends are affected by the Pacific Decadal Oscillation (PDO) (Mantua and others,
1997; Neal and others, 2002; Hodgkins, 2009). During positive, or warm, phases of the PDO,
streamflow tends to be higher in winter -spring and lower in June, and during negative, or cool,
phases of the PDO, streamflow tends to be lower in winter -spring and higher in June. Shifts in
the PDO occurred in 1925 (negative to positive), 1947 (positive to negative), 1977 (negative to
positive), and likely in 2006 or 2007 (positive to negative) (JISAO, 2014). Therefore, the
streamflow data collected during 2005-2008, spanning a phase shift of the PDO, may provide a
fair estimate of streamflow during longer periods.
Some of the streamgages in Southeast Alaska have longer records and can be used to extend the
streamflow records at the Gunnuk Creek by statistical methods. Streamflow analysis techniques
are used to extend records from a short -record station by use of regression with stations with
longer records when the concurrent records from the stations are well correlated (Curran, 2012).
Records from 14 USGS strearngaging stations with concurrent records with Gunnuk Creek were
compared with the streamflow record at Gunnuk Creek. Streamgaging stations with records that
were not concurrent with Gunnuk Creek, streams with regulated flow, or streamgages with
relatively short records were not considered. Two stations stand out as having better correlations
with Gunnuk Creek than the others, Staney Creek and Old Tom Creek. The Staney Creek
streamflow record was collected at 2 different sites, 15081500 Staney Creek near Craig (Lat.
55°48'57", Lon. 133°07'58" NAD27, 51.6 mi) and 15081497 Staney Creek near Klawock (Lat.
55°48'05", Lon. 133°06'31" NAD27, 50.6 mi2), but the records are considered equivalent
(USGS, 2014).
Gunnuk Creek daily mean discharge was regressed against Old Tom Creek and Staney Creek
(combined) daily mean discharge. Both stations yielded statistically significant regressions
(Table 1). OId Tom Creek has one of the longest records of any streamgage in Alaska, which is
advantageous for record extension. However, when a regression of Gunnuk Creek on Old Tom
Creek was computed and the residuals were examined, residuals from Old Tom Creek showed
considerable scatter at lower discharges compared to the residuals from the Staney Creek
regression. This indicates that although the overall regression is robust, the regression of Gunnuk
Creek against Old Tom Creek likely introduces more error at lower discharges than the
regression of Gunnuk Creek against Staney Creek. The regression of Gunnuk Creek against
Staney Creek is slightly more significant, and the scatter of residuals is greatest at larger
discharge when strearnflow is not as critical to determining feasibility of a low -head or run -of -
the -river facility. The best -fit equation is:
log(Y) = 0.931 *log(X) - 0.512
where Y=Gunnuk Creek estimated daily mean discharge and X=Staney Creek daily mean
discharge.
Page 11
Gunnuk Creek Hydroelectric Project
Reconnaissance Revort
Table 1 - Gunnuk Creek Gage Correlations
USGS
Location
Drainage
Datum of
Correlation
Station
Station
(lat/long
Area
Gage
Period of Record
Coefficient
Name
NA.D27)
(mi)
(approximate)
(r2)
(feet)
Staney
15081497
Creek near
55048'0511/
50.6
50
9/1/1989
Current
Klawock
133006'31"
(2014)
0.6396
Staney
15081500
Creek near
55°48'57"/
ii
51.6
2
10/1/1964
9/30/1981
Crai
133°0T58"
Old Tom
15085100
Creek near
55023'44"/
5.9
10
7/1/1949
Current
0.4988
Kasann
132°24'25"
(2014)
Figure 5 shows the comparison of measured discharge with the discharge predicted by the
regression of Gunnuk Creek against Staney Creek for the overlapping period of record.
1000D — --
---Gunnuk Creek predicted discharge...
—Gunnuk Creek measured discharge...
1000
U
N
M
a-+
al oa
to
L
ru
r,
U
V)
Q
10
1 `-
9/1/2005 3/20/2006 10/6/2006 4/24/2007 11/10/2007 5/28/2008
Figure 5 - Staney Creek Correlation
3.3 Flow Duration
To determine flow duration characteristics from the Gunnuk Creek extended data, mean daily
discharge data were sorted, ranked, and the time that a given flow was equaled or exceeded
Page 12
Gunnuk Creek Hydroelectric Project
Reconnaissance Report
computed by dividing the rank by the total number of observations plus 1, expressed in percent.
A flow duration table from the extended record at Gunnuk Creek is presented in Table 2.
Table 2 - Gunnuk Creek Flow Exceedance Data
Percent Exceedance
1% 2% 5% 10% 20% 30% 50% 70% 80% 90% 95% 98% 99%
October 808 625 427 296 199 144 81 50 38 25 17 12 9.4
November 708 589 376 247 153 107 62 37 28 18 13 9.0 7.1
December 693 537 372 254 151 98 52 31 22 13 9.4 7.2 5.7
January 683 487 297 197 115 79 41 22 16 9.9 6.5 3.7 3.0
February 507 364 239 167 104 69 38 23 17 11 7.3 4.2 3.5
March 365 286 201 136 87 62 37 22 17 11 8.7 7.1 5.5
April 441 330 210 157 92 71 49 35 28 22 19 15 12
May 302 241 168 120 84 65 43 27 21 14 11 7.8 6.8
June 157 127 82 64 45 35 23 14 11 7.8 5.2 4.1 3.8
July 192 139 84 57 33 24 16 10 8.4 6.7 4.9 3.8 2.8
August 304 220 136 79 49 32 17 10 7.9 5.2 4.0 2.9 2.4
September 713 532 342 227 127 83 44 24 18 11 7.1 3.3 2.6
4 Project Alternatives
4.1 Alternative 1 - Expansion/Rehabilitation of Existing Hydroelectric Project
This alternative is an expansion/rehabilitation of the existing hydroelectric facilities on Gunnuk
Creek. This alternative would utilize the existing water supply dam and intake works located on
Gunnuk Creek. A new 2,100 foot -long 54-inch diameter steel penstock would connect from the
existing outlet works in the dam and would replace the existing 10-inch diameter HDPE
penstock/hatchery supply pipe.
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Gunnuk Creek Hydroelectric Project
Reconnaissance Report
COAI(i1W.1101/ AM Rr11EF J 1MCUVM
vALNf INiH ?MLAnM G VALVE
OOYlNSififAM LACE (OFfSrT FOP PPOIEGTgH)
�OF 04W
49'
E
POLYURI
TNR£AO-O-LET— I I!I I —I f ICI I I —I
(SEC NOTE s)
f�
_ _ I I —III— COATING (Y
46' 0 O.I. PIPE
OLE
CL"
Sfi' MIN. —1 4 \ F q I FF � SMHFEII Pn'E. S 76 E
10' 0 f3DPE PIPE
I' \\_ ,TfOM of to -INCH PPr sK4u ac YA%
%ATERMOP OYP) J 1/2-INCH WCNEP THAN MIDI SVNFACE
or 6a-mw FSPE.
48' TO 1 O" TRANSITION DETAIL
T � NOT TO SCALE -
Figure 6 - Existing outlet works in dam
The new penstock would follow the same route as the existing penstock. Areas of bank erosion
along the existing penstock route would be stabilized.
A new 22' x 36' powerhouse would be constructed adjacent to the existing hatchery building.
The powerhouse would use the foundation of the existing Coho building. The functionality of
the backup water supply for the hatchery through the foundation would remain in place. The
new powerhouse would contain a single crossflow-type hydroelectric turbine with an installed
capacity of 500 W.
2 IPEC has indicated a target installed capacity of 500 M
Page 14
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STAIRS d D=
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rST£FL GRATE
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ARFA =
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Gunnuk Creek Hydroelectric Project
Reconnaissance Report
T81-
EEL GRATE
STAIRS WiTN ff 11 x IO ' HYDRO
MMD RAILS / gOILDINC
STDRAGF / WOOD FRAME ON
STORAGE CONCRFIF SLAB
PILE5X8£R
A
y
GRAVEL
AREA 7 .+r
NCR£
DIV£RSh
,, BLDcxs
NEW POWERF OUSE
LOCATION i'
Figure 7 - New powerhouse location at hatchery
Access to the intake and powerhouse would be through existing roads and interconnection would
be via the existing overhead electrical supply to the hatchery.
There is not a way of creating enough storage to allow for seasonal regulation so the project
would operate in a near run -of -the -river mode. Operational flexibility on a daily basis could be
enhanced by adding a small amount of working storage behind the dam. This could be
accomplished by adding inflatable gates in the spillway bays. The technical considerations of
this option would need to be further investigated during final project design.
Key project parameters are presented in Table 3 below.
Table 3 - Alt. X Project Parameters
Headwater, ft
89
Tailwater, ft
20
Gross Head, ft
69
Net Head, ft
60
Design Flow, cfs
130
Capacity, M
500
Drainage Area, miz
15.4
Avg, Inflow, cfs
97
Active Storage, AF
0
Page 15
Gunnuk Creek Hydroelectric Project
Reconnaissance Report
4.2 Alternative 2 — Mid -Basin Run -of -river Project
Alternative 2 is a run -of -river project located approximately in the middle of the Gunnuk Creek
drainage basin and is similar in nature to the Phase 1 project identified in the Christensen report.
Diversion of Gunnuk Creek would occur just downstream of the confluence of two forks at about
elevation 300, approximately 2.7 miles upstream from tidewater. At the point of diversion, the
drainage area is estimated to be 10.6 mil. The facilities would be comprised of a simple
diversion structure, are intake, a sluiceway capable of releasing incremental flows and a spillway.
Water would be conveyed to the powerhouse via a 36-inch diameter 10,000-foot-long steel
penstock. The powerhouse would be located around elevation 100 and would be a simple
concrete reinforced structure that would contain a single Turgo-type turbine, synchronous
generator and associated switchgear and controls. The installed capacity would be 500 kW.
Access to the powerhouse site would be with a new 0.25 mile road beginning near the existing
water tank. Transmission would be via an overhead pole line following the access road. The
general location of features is shown in Figure 8.
light dF �► `' ;
Car
Figure 8 - Alternative 2 Conceptual Project Layout
Key project parameters are presented in Table 4.
Page 16
Gunnuk Creek Hydroelectric Project
Reconnaissance Report
Table 4 - Alt. 2 Project Parameters
Headwater, ft
300
Tailwater, ft
100
Gross Head, ft
200
Net Head, ft
170
Design Flow, cfs
46
Capacity, M
500
Drainage Area, mil
10.6
Avg. Inflow, cfs
65
Active Storage, AF
0
4.3 Alternative 3 —Storage Project
Alternative 3 is a storage project located approximately in the middle of the Gunnuk Creek
drainage basin and is similar in nature to the Phase 2 project identified in the Christensen report
with the notable difference being that the reservoir would be located on the adjacent sub -basin.
Diversion of Gunnuk Creek would occur at about elevation 450, approximately 3.9 miles from
tidewater. At the point of diversion, the drainage area is estimated to be 5.7 me. The facilities
would be comprised of a 50-foot-high, 900-foot-long concrete faced rock fill dam, an intake, and
a spillway. It is assumed that an approximate 10-15-foot-high, 700-foot-long saddle dike would
also be required. The reservoir created would have a surface area of approximately 500 acres
and a usable storage volume of 7,500 acre-feet.
Water would be conveyed to the powerhouse via a 40-inch diameter 4,000-foot-long steel
penstock. The powerhouse would be located around elevation 300 and would be a simple
concrete reinforced structure that would contain a single Francis -type turbine, synchronous
generator and associated switchgear and controls. Since this is a storage project, the installed
capacity has been set at 1,000 kW to accommodate future load growth. Access to the site would
be with 1.0 miles of new road extending from the existing road system. Transmission would be
via a 3-mile-long overhead pole line following the existing roads in the area. The general
location of features is shown in Figure 9.
Page 17
Gunnuk Creek Hydroelectric Project
Reconnaissance Renort
J1
9�0
Figure 9 - Alt. 3 Conceptual Project Layout
Key project parameters are presented in Table 5.
Table 5 - Project Parameters
Headwater, max. ft
500
Headwater, min. ft
470
Tailwater, ft
300
Gross Head, ft
200
Net Head, ft
174
Design Flow, cfs
85
Capacity, M
1,000
Drainage Area, miz
5.7
Avg. Inflow, cfs
36
Active Storage, AF
7,500
Page 18
Gunnuk Creek Hydroelectric Project
Reconnaissance Report
5 Permitting/Licensing
Typically hydroelectric projects are regulated under Federal Energy Regulatory Commission
(FERC) guidelines. The jurisdiction granted to FERC to issue licenses and exemptions was
established by Section 23(b) of the Federal Power Act of (1976) 3, which:
"... requires that waterpower projects be licensed if they are located on
navigable waters of the United States, occupy any part of the public lands or
reservations of the United States, use surplus water or waterpower from a
Federal Government dam, or, if constructed after August 26, 1935 are located
on any part of a non -navigable water subject to Congress' Jurisdiction under
the Commerce Clause and affect the interests of the interstate or foreign
commerce. "
Any proposed Gunnuk Creek hydroelectric project would appear to lack the specific criteria that
would necessitate any license or exemption from FERC because the project:
1. does not involve any waterbody having known current or historic navigational uses such
as the passage of people or goods, and so is located on non -navigable waters,
2. will not use surplus water or water power from a federal dam,
3. will be located on non -navigable waters and is not subject to the authority of Congress
under the Commerce Clause, or
4. will not occupy lands or reservations of the United States.
The opinion that a FERC license would not be required for a Gunnuk Creek hydropower project
is based on the lack of FERC jurisdiction and not on an exemption granted by that agency.
Consultation with FERC will need to be done to verify and document that this project is not
under FERC jurisdiction.
The following permits would likely be required for the proposed project:
• Alaska Department of Fish and Game (ADF&G) Division of Habitat Title 16 Fish
Habitat Permit
• US Army Corps of Engineers Section 404 permit
• Alaska Department of Natural Resources (ADNR) Water Rights Permit
3 Section 23(b), 16 USC subpart 817.
Page 19
Gunnuk Creek Hydroelectric Project
Reconnaissance Report
6 Energy Generation
Energy generation for Alternatives 1 and 2 was estimated using HDR's proprietary software
"Hydroelectric Evaluation Program" (HEP). HEP has been specifically designed to model run -
of -river operations. HEP uses tabulated daily flows, turbine and generator efficiencies, friction
coefficients and physical parameters to simulate energy production through a period of
streamflow record. Turbine and generator efficiencies are determined from tables. Output from
HEP consists of effective capacity rating of the unit(s), simulated production in MWh, percent
operating time and overall plant factor.
Energy generation for Alternative 3 was estimated using a reservoir simulation model. The
model uses average monthly flow data and stage/storage characteristics to optimize dispatch
using inflows and storage to maximize energy generation. Outputs from the model include
estimated monthly generation and pool elevations.
6.1 Assumptions
The following were key assumptions used in modeling energy production:
• USGS gage number 15087565 data was used for the energy analysis. Long term
synthesized stream data was used for the sensitivity analysis.
For the alternatives with storage, a water -to -wire efficiency was assumed at 85%. For the
generating equipment likely to be used at this project, turbine efficiencies can vary
greatly depending on the flow. However, at this level of study a constant level of
efficiency was considered appropriate because the storage would allow for optimized
dispatch. The reservoir was assumed to start 75% full on October I" and was constrained
to return to the starting elevation at the end of September to maintain year-to-year
continuity. This was determined to be the best operating strategy to maximize the use of
fall runoff.
• Tailwater elevation was assumed to remain constant over all flows. In practice, it would
likely vary slightly; however, not enough data were available to refine this assumption.
• For daily simulations, head loss was calculated using the daily flow and water
conveyance system parameters. For monthly simulations, head loss was assumed to
average 7%.
• Losses for station service and transformers were estimated to reduce gross generation by
2%.
• For Alt. 1 it is assumed that minimum instream flows will be as requested by ADF&G in
the Environmental Assessment prepared for the construction of the new water supply
dam. Alt. 2 and 3 are above the anadromous barrier and have short bypass reaches. As
such, a minimum instream flow of 5 cfs has been assumed. Table 6 shows the minimum
instream flows used in modeling.
Page 20
Gunnuk Creek Hydroelectric Project
Reconnaissance Report
Table 6 - Minimum Instream Flows
MIF, cfs
Aft. 1 Alts.2&3
Oct
20 5
Nov
20 5
Dec
15 5
Jan
15 5
Feb
15 5
Mar
15 5
Apr
20 5
May
20 5
Jun
15 5
Jul
10 5
Aug
10 5
Sep
15 5
6.2 Results
An estimate of the annual average generation potential for each of the alternatives is presented in
Table 7 below. The usable energy from a new hydroelectric project is a measure of how well
the generation from the project matches up with the load on a seasonal basis. Energy generation
in Kake for the period 2000-2014 has averaged 2,860 N1Wb/year and has varied seasonally as
shown in Figure 10. For this analysis, the generation from the various alternatives was
compared to the five-year monthly average of system load to estimate usable energy.
400,000
350,000
300,000
250,000
200,000
150,000
100,000
Kake Energy Usage
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Figure 10 - Kake Energy Usage
Page 21
2014
2013
— 2012
2011
2010
Gunnuk Creek Hydroelectric Project
Reconnaissance Report
Table 7 - Average Annual Generation
Alternative
Capacity
Avg. Annual Energy
Usable Annual
Energy
(kW)
(MWh)
(MWh)
I — Existing Dam
Soo
1,620
1,620
2 — New R.O.R
500
2,590
2,400
3 — New Storage
1,000
4,150
2,860
6.3 Sensitivity Analysis
To assess the suitability of using the short-term hydrological record from USGS gage number
15087565 for energy modeling, energy generation was also estimated by integrating the flow
duration data for the synthesized long-term flow record (Table 2). Using this approach, the
synthesized data produced annual energy estimates of 88%, 96% and 84% for Alternatives 1, 2
and 3 respectively. This indicates that the expected long term energy generation from the
alternatives could be slightly less than presented in Table 7. However, due to the coarseness of
the synthetic flow duration data and the strength of the correlation coefficient, the results are
inconclusive.
The minimum instream flow assumption for Alt. 1 was based upon ADF&G comments made
during the consultation process for the new dam. However, the City's water right has a
minimum instream flow requirement of I 1 cfs continually. If this assumption was made, the
average annual generation estimate for Alt. I would increase by 100,000 kVVWyear.
7 Cost Estimates
An opinion of probable construction costs was derived for each of the alternatives presented
above. The approach used was to develop base work units and unit prices and then apply these
units and prices consistently to the various alternatives. Vendor budgetary quotes and recent
construction cost information was used to estimate equipment and materials. This approach
allowed a common platform from which to establish priority amongst the alternatives, although
slight differences do exist. It should also be noted that the project sizes for the various
alternatives may not be the true optimum. For example, future refinement may determine that
the design flow for the turbine should be slightly greater or smaller than what was assumed. A
sensitivity analysis performed as part of the energy generation estimating process indicated
assumed values were appropriate.
Although future refinement of the estimated unit costs or generation estimates may affect the
final benefit/cost evaluation, it should not affect the ranking of the alternatives amongst
themselves.
The following assumptions were used in the cost estimate:
Page 22
Gunnuk Creek Hydroelectric Project
Reconnaissance Report
• Indirect construction costs associated with engineering, construction management,
licensing, permitting and the owner's internal costs were added to the direct construction
cost estimate as percentages.
-- Design engineering was assumed to be 10% of the total direct construction costs.
- The Owner's General Administration and Overhead of the design and
construction was assumed to be 1 % of the total direct construction costs.
Construction management was assumed to be 10% of the total direct construction
costs.
• A contingency of 30% was added to the total of the direct construction costs to reflect
uncertainties of layout and design that wouldn't be resolved until later in the development
process. For alternative 1 the contingency was reduced to 20% reflective of the existing
development and the knowledge of the alternative.
Table 8 presents the results of the reconnaissance level cost estimates for the three alternatives
considered.
Table 8 - Summary of Costs
Alt.1
Alt.2
Alt.3
Total Direct Construction Costs
$3,761,000
$11,812,000
$24,507,000
Contingency
$752,000
$3,544,000
$7,352,000
Engineering
$376,000
$1,181,000
$2,451,000
Licensing & permitting compliance
$38,000
$118,000
$245,000
Owner's General Administration & overhead
$38,000
$118,000
$245,000
Construction Management
$376,000
$1,181,000
$2,451,000
Subtotal
$5,341,000
$17,955,000
$37,250,000
Interest During Construction
$124,000
$887,000
$1,841,000
Total
$5,465,000
$18,842,000
$39,091,000
8 Economic Evaluation
A detailed economic evaluation was not included in the scope of this work. However, in order to
provide a conceptual view of the economics, an evaluation was made using the State of Alaska's
Renewable Energy Fund Round 9 evaluation worksheet. The analysis assumed the "diesel off'
scenario. The capital cost was assumed to be equally distributed over two years for Alts. 1 & 2
and three years for Alt. 3. Diesel efficiency was assumed to be 13.0 kNAWgallon reflective of the
current diesel generation efficiency.
The table below provides the benefit/cost ratio of the alternatives for two energy generation
scenarios.
Page 23
Gunnuk Creek Hydroelectric Project
Reconnaissance Report
Table 9 - Benefit/Cost Summary
Alt.1 Alt.2 Alt.3
Max. Energy Generation 3.13 1.34 .97
Usable Energy Generation 3.13 1.22 .60
9 Conclusions and Recommendations
A small run -of -river hydroelectric project making use of the existing water supply dam
(Alt. 1) is the best development option for Gunnuk Creek at this time. Costs are
minimized because the dam and intake facility have already been constructed, and no
new transmission lines or access roads are required. Re -use of the foundation of the
Coho building at the hatchery reduces excavation and in -water work risk. It is the best
understood of all the alternatives considered and therefore there is higher confidence in
the analysis.
It is estimated that the project could become fully operational with 18-24 months. The
next steps in project development are:
- Initiate discussions with ADF&G regarding requirements for instream flow in the
bypass reach.
- Develop joint use agreement with the State of Alaska for the use of the hatchery
water supply and powerhouse site. Replacement of the pipeline and stabilization
of the route has the added benefit of increasing the reliability of the hatchery
water supply.
- Initiate discussions with the Southeast Alaska Land Trust to confirm project is
consistent with the conservation easement that is in place.
- Final design of the project to include surveying the plan and profile of the pipeline
route, soils exploration along pipeline route and preparation of design plans and
specifications.
+ A mid -basin run -of -river project (Alt. 2) appears to have some initial economic merit
however there is a lot of uncertainty about its development. The concept presented here
should be viewed as "what might a new run -of -river project look like" rather than a strict
project definition. Alternative 2 is based upon limited topographic information and site
evaluation. The largest uncertainty lays in the definition of the penstock route. It is
presumed that there would be great difficulty in getting the penstock out of the incised
channel which would allow it to follow an overland route. It may be possible to partly
alleviate this problem by moving the intake upstream to a higher elevation but this would
come with increased cost and would significantly decrease the drainage area. In order
to begin to address these questions, a detailed feasibility study would need to be
conducted.
+ A new storage project (Alt. 3) could meet all of Kake's needs now and for sometime into
the future, but the high cost of developing seasonal storage makes it cost prohibitive.
Like Alternative 2, Alternative 3 is based upon limited topographic information and site
Page 24
Gunnuk Creek Hydroelectric Project
Reconnaissance Report
evaluation. There are many technical issues that would need to be evaluated and
overcome before making a determination if the site is even suitable for a dam.
Page 25
Gunnuk Creek Hydroelectric Project
Reconnaissance Report
Appendix A
Geotechnical Reconnaissance Report
Golder
- Associates
August 25, 2014
Paul Berkshire, PE
HDR Alaska, Inc.
2525 C Street, Suite 305
Anchorage, AK 99503-2632
1406769
RE: GEOTECHNICAL RECONNAISSANCE, GUNNUK CREEK HYDROELECTRIC PROJECT
Dear Paul:
In response to your request, Golder Associates Inc. (Golder) made a preliminary geotechnical
reconnaissance of the Gunnuk Creek watershed as part of a potential hydroelectric project near Kake,
Alaska. This reconnaissance was made by Bob Dugan of Golder in the company of Paul Berkshire of
HDR on June 25, 2014.
The purpose of the reconnaissance was to assess the general geologic conditions and identify potential
sites that might be suitable for a hydroelectric dam and related facilities.
1.0 METHODOLOGY
1.1 Review of Existing Information
The reconnaissance was preceded by the review of existing geologic mapping by the U.S. Geological
Survey (Gehrels and Berg, 1992) (Muffler, 1976) and reports provided by HDR that included a Preliminary
Appraisal Report for Hydroelectric Potential (Alaska Power Authority,1977) prepared by Robert W.
Retherford Associates and a Hydropower Reconnaissance Report (PCE, 2013) by PCE. The PCE report
concluded that hydropower options near Kake are limited due to relatively gentle topography and
regionally low precipitation, The 1977 report stated that a suitable storage basin existed at approximately
stream mile 3.5 of Gunnuk Creek requiring two earth -filled dams on the two forks of the stream.
We also reviewed document by the Alaska State Dam Engineer (Cobb, 2003). This report addresses the
failure of the timber dam in 2000 and the concrete dam that was constructed on Gunnuk Creek at the 125
foot elevation, This new dam replaced the failed timber dam at the same location. This report notes that
upstream erosion tends to fill the reservoir with sediment and debris, requiring significant maintenance.
1.2 Site Reconnaissance
For the reconnaissance in Kake we met with Peter Bibbs of the Inside Passage Electric Cooperative
(IPEC), Adam Davis, a Kake resident and Community Catalyst, and Bob Christensen of Sustainable
Southeast. It is our understanding that IPEC is in the early stages of identifying a potential new
hydroelectric darn site. The reconnaissance included an aerial inspection of Gunnuk Creek watershed,
landing and inspection of a local quarry located approximately 3 miles upstream of the outlet, and ground
inspection of an area upstream of the quarry where various tributaries converged. The project vicinity and
area with various features are shown in Figures 1 and 2.
1.3 Image Interpretation
Several types of imagery and remote sensing data were used to gain understanding of the
terrain. Imagery types included NASA Landsat satellite imagery dated between 2000-2002, 1m satellite
RGB imagery dated June, 2006, from USGS High Resolution State Orthoimagery for the Southeastern
Gunnuk Creek Hydroelectnc Project
Golder Associates Inc.
2121 Abbott Road, Suite 100
Anchorage, AK 99607 USA
Tel: (907) 344-6001 Fax: (907) 344-6011 www.goider.com =
Golder Associates: Operations in Africa, Asia, Australasia, Europe, North America and South America
Golder, Golder Associates and the GA globe design are trademarks of Golder Associates Corporation
Paul Berkshire August 25, 2014
MDR Alaska, Inc. 2 1406769
Areas, Alaska, published 2011, and color aerial photographs. 30-meter elevation data was also used to
create hillshade images, and in 3-D analyses of the site. The elevation data used was acquired by the
Shuttle Radar Topography Mission (SRTM) using Interferomic C-band Spaceborne Imaging Radar, dated
February 2000, and published and distributed by of NASA, NGA and the USGS. Recent USGS
topographic maps, 1:63,360 scale USGS Topographic maps; Petersburg D-6, AK (1995), and Sumdum
A-6, AK (1994) were also acquired and used for the analyses.
These datasets were reviewed in both a 2-D and 3-D perspectives using software programs including
Giobalmapper 15 and OT Modeler.
2.0 GENERAL SITE CONDITIONS
The Gunnuk Creek watershed is underlain by the Cannery Formation which is composed of a thick
sequence of Permian/Devonian-age sedimentary and volcanic rocks. These units include fine-grained
tuffaceous argillite and graywacke plus subordinate chert, limestone, and andesitic volcanic rocks. The
Cannery Formation is known to be intensely deformed by both complex folding and faulting and the rocks
are typically highly fractured (Muffler, 1967). The rock appears to have undergone low—grade
metamorphism. The region was intensely glaciated during the Pleistocene which scoured the bedrock.
Glacially -derived unconsolidated materials mantle the bedrock including glacio-marine deposits at lower
elevations.
The Gunnuk Creek watershed and adjacent areas are traversed by a series of parallel east -west trending
lineaments interpreted to be inactive faults. The spacing of the lineaments typically range from 0.26 to
0.5 miles, as shown in Figure 3. These lineaments have formed small linear depressions which are
occupied by tributaries of Gunnuk Creek. Gunnuk Creek both follows and cuts across several of these
lineaments at a sub -perpendicular angle between Alpine Lake and the outlet at Kake.
The ground surface is heavily vegetated so exposures of the bedrock and mineral soils are limited. The
area has been extensively logged and a logging road provides access to Alpine Lake and other portions
of the watershed. Bedrock consisting of a highly fractured argillite with thin quartz veins is exposed in a
quarry approximately 3.5 miles inland of the coast near Gunnuk Creek, as shown in Figure 4. It is also
exposed under the bridge that spans the creek upstream of the quarry, as shown in Figure 5. The
exposures in the quarry and under the bridge both have steeply dipping bedding. Most of the upper
reaches of the Gunnuk Creek floodplain appear to be relatively broad and flat with meandering channels
suggesting that several feet, or more, of sediments and organic materials overlie the bedrock in the valley
bottoms. By contrast, much of the 2.5 miles of the creek closest to the outlet is characterized by more
deeply -incised, narrow, and linear channels.
3.0 POTENTIAL DAM SITES
Identifying potential sites for a hydroelectric dam on Gunnuk Creek is challenging due the masking of the
terrain by heavy vegetation and the lack of high -resolution bare -earth imagery. The best options for
further investigation from a geologic standpoint appear to be Sites 1 and 2 identified in Figures 2 and 3.
These sites seem to offer the best chance for limiting the length of the dam and encountering shallow
bedrock on the channel bottom and valley sidewalls. They also appear to provide for more reservoir area
and hydraulic head than other locations. Depending on the height of the dam at Site 1, a second dam
may be necessary on an adjacent tributary to the north to contain or expand the reservoir.
A third potential site would be coincident with the bridge immediately upstream of the quarry. Bedrock is
visible in the steam under the bridge indicating that shallow bedrock may extend the length of the dam
and thus limit the removal of surficial sediments for a dam keyed into bedrock. A potential problem with
this site is the length of the dam. Based on SRTM 30m data, a 10 foot high dam would be approximately
400 feet long and a 15 foot high dam would be approximately 550 feet long.
Dw Golder
Gunnuk creek Hydroelectric Project Associates
Paul Berkshire August 25, 2014
HDR Alaska, Inc. 3 1406769
4.0 RECOMMENDATIONS
Going forward, we recommend that a detailed LiDAR survey be conducted. The survey area should
include the entire watershed, if funding allows, but at a minimum it should include the vicinity of Sites 1
and 2. This would provide the data for bare -earth modeling of the ground surface and detailed contour
mapping. Currently, the 100 foot interval contours on the USGS mapping is the best available and it is
too vague for siting on the relatively gentle terrain.
If these sites meet the criteria for reservoir size and head then they should be investigated in the field to
determine the specific geologic conditions and to optimize the dam location within the vicinity of the
identified site. While the geology of the Cannery Formation that underlies the area is complex and
contains several different lithologies, there were no obvious fatal flaws observed in the rock that could
preclude construction of a dam keyed into bedrock.
We appreciate to opportunity to work with you on this project. Please contact us with any questions.
GOLDER ASSOCIATES INC.
Robert G. Dugan, CPG
Principal Engineering Geologi6t
RGDIMRMImlp
Attachments: References
Figure 1 Vicinity Map
Figure 2 Project Location Map
Figure 3 Hillshade Map
Figures 4 and 5 Bedrock Photographs
Mark R. Musial, PE
Principal and Geotechnical Practice/Program
Leader
Gunnuk Creek Hytlroeleclnc Project
lifts
Golder
Associates
REFERENCES
Cobb, Charles, F. 2003. The Kake Darn Failure: Community and Engineering Response; written by the
State Dam Engineer.
Gehrels, G.E. and Berg, N.C. 1992. Geologic Map of Southeast Alaska, Map 1-1867, published by U.S.
Geological Survey.
Muffler, J.P. 1967. Stratigraphy of the Keku Islets and Neighboring Parts of Kuiu and Kupreanof Islands
Southeastern Alaska: U.S. Geological Survey Bulletin 1241-C, 58p., 1 Sheet, 1:63,360 scale.
Robert W. Retherford Associates. 1977. Preliminary Appraisal Report — Hydroelectric Potential (for
Kake), State of Alaska Power Authority.
Inside Passage Electric. 2013. Hydropower Reconnaissance Report for Kake, Alaska.
Gunnuk Creek H,vdroelecinc Project
99 Golder
Associates
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