HomeMy WebLinkAboutGlacier Fork Reconnaissance Study 2013US Army Corps
of Engineers
Alaska District
Glacier Fork Reconnaissance Hydropower Study
Palmer, Alaska
March 2013
Table of Contents
1. Executive Summary .............................................................................................. 1
2. Introduction ............................................................................................................ 3
2.1. Purpose and Scope ........................................................................................................................ 3
2.2. Previous Studies ............................................................................................................................ 4
2.3. Accessibility ................................................................................................................................... 5
3. HydrologJT, Hydraulics and Power ................................................................... 5
3 .1. Study Area ..................................................................................................................................... 5
3.2. Topographic Data .......................................................................................................................... 6
3.3. Watershed Characteristics ............................................................................................................ 7
3.4. Climate and Hydrology .................................................................................................................. 7
3.4.1. Regional Climate ................................................................................................................... 7
3.4.2. Stream flow Patterns .... · ........................................................................................................ 9
3.4.3. Hydrologic Uncertainty ....................................................................................................... 15
4. Regional Geology ................................................................................................. 17
4.1. Regional Setting and Geomorphology ........................................................................................ 17
4.2. Geologic History .......................................................................................................................... 18
4.2.1. Geological Hazards .............................................................................................................. 19
4.2.1.1. Earthquake ...................................................................................................................... 19
4.2.1.1.
4.2.1.2.
Glacier Advance or Retreat ............................................................................................. 20
Glacier Fork Jokulhlaups ................................................................................................. 22
5. Sediment Management ...................................................................................... 24
5.1. Reservoir Sedimentation ............................................................................................................. 24
5.2. Sediment Erosion of Hydraulic Equipment ................................................................................. 28
6. Conceptual Alternatives Descriptions and Design Considerations .... 29
6.1. Alternative 1-Upper Glacier Fork Dam ..................................................................................... 29
6.1.1. Description of Project Components .................................................................................... 29
6.1.2. Site Specific Concerns and Risks and Feasibility ................................................................. 32
6.1.3. Conclusions ......................................................................................................................... 32
6.2. Alternative 2 -Lower Glacier Fork Dam ...................................................................................... 33
Page I i
6.2.1. Description of Project Components .................................................................................... 33
6.2.2. Project Specific Power Production Estimates ..................................................................... 35
6.2.3. Site Specific Concerns and Feasibility ................................................................................. 36
6.3. Alternative 3-Glacier Fork Run of River ..................................................................................... 37
6.3.1. Description of Project Components .................................................................................... 37
6.3.2. Project Specific Power Production Estimates ..................................................................... 41
6.3.3. Site specific concerns and risks ........................................................................................... 42
6.3.4. Project Costs ....................................................................................................................... 43
7. Glacier Fork Access ............................................................................................. 44
7.1. Road Design Criteria .................................................................................................................... 44
7.2. Preliminary Alignment Options ................................................................................................... 44
8. Envi.ronmenta.l ...................................................................................................... 46
8.1. Environmental Considerations .................................................................................................... 46
8.2. Environmental Requirements ..................................................................................................... 4 7
8.3. FERC Status/Jurisdiction .............................................................................................................. 48
9. Land Ownership ................................................................................................... 48
10. Economic Analysis ............................................................................................... 51
11. Conclusions and Recommendations ............................................................. 52
References .................................................................................................................... 53
Appendix A Utilization of the National Elevation Dataset
Appendix B Additional Geologic Information
Appendix C Power Integration Memorandum
Appendix D ROM Cost Estimate
Table of Figures
Figure 1. Project Area .................................................................................................................................... 4
Figure 2. Glacier Fork basin (Outlined in Red). USGS Gage (15280900) shown as a blue circle with
the two major sub-basins Metal Creek and Upper Glacier Fork shown ..................................... 6
Figure 3. Average, maximum and minimum air temperature for Palmer (WBAN 25331) ........................... 8
Figure 4. Precipitation at 5 nearby weather stations ................................................................................... 9
Page Iii
Figure 5. Measured discharge data for upper Glacier Fork (15280900). Data is provisional for WY
2012 .......................................................................................................................................... 10
Figure 6. USGS Stream gages used in this study with periods of record shown. A solid blue bar
indicates a continuous daily record; the dashed bars indicates seasonal operation .............. 11
Figure 7. Upper Glacier Fork concurrent summer (May 1-October 1) flows plotted against the
Knik (left), Matanuska (right). Data from WY 2011 is shown in blue and data from WY
2012 is shown in Red ................................................................................................................ 12
Figure 8. Top-Altitude distribution of precipitation as rain and snow, ice melt, snowmelt, and
runoff for a glacier in Southcentral Alaska (From Mayo and Trabant, 1979). Bottom-
Glaciated area versus elevation for each watershed ................................................................ 13
Figure 9. Comparison of measured and predicted average monthly flows for Glacier Fork ...................... 14
Figure 10. Upper Glacier Fork (blue) and Metal Creek (green) estimated mean monthly flows on
the left and percent exceedance on the right .......................................................................... 15
Figure 11. Comparison of the exceedance duration curves generated using Extended Upper
Glacier Fork discharge record (red) and Two years of measured stream gage data on
Upper Glacier Fork (blue) .......................................................................................................... 17
Figure 12. Regional Topographic Features Surrounding Glacier Fork of the Knik River. Excerpt
from Anchorage 1:250,000 Quadrangle Map, USGS 1985 revision .......................................... 18
Figure 13. Schematic showing conceptual formation of subduction zone, trench, accretionary
wedge at continental margin, Modified from Bradley and Miller (2003) and Connelly
(1978) ........................................................................................................................................ 19
Figure 14. USGS Map (-1950s) and aerial view of the Knik Glacier adjacent to Glacier Fork. The
red line indicates the approximate toe of the glacier as shown on the 2011 image.
The orange area identifies the low divide between Glacier Fork and Knik Drainages ............. 21
Figure 15. Glacier Dammed Lakes and Outburst Floods in Alaska from Post & Mayo, 1971
(modified) .................................................................................................................................. 23
Figure 16. Grasshopper Valley looking towards the Mt. Marcus Baker Glacier. Photograph taken
looking upstream ...................................................................................................................... 24
Figure 17. Glacier Fork outwash plain. Photograph taken looking downstream ....................................... 25
Figure 18. Deposited sediment at the lower end of the Glacier Fork canyon ............................................ 28
Figure 19. Canyon dam layout .................................................................................................................... 30
Figure 20. Canyon Dam Site, photograph taken looking downstream ....................................................... 31
Figure 21. Storage Elevation Curve for Canyon Dam Alternative ............................................................... 31
Figure 22. Alternative 1 distribution of monthly power generation .......................................................... 32
Figure 23. Lower Glacier Fork dam reservoir layout ................................................................................... 34
Figure 24. Lower Glacier Fork dam storage elevation curve ...................................................................... 34
Figure 25. Dam Profile with modifications based on site visit .................................................................... 35
Figure 26. Lower Glacier Fork distribution of monthly power generation ................................................. 36
Figure 27. Run of river conceptual layout ................................................................................................... 37
Figure 28. Plan view of intake works, de-sanding basin, tunnel and maintenance building ...................... 38
Page I iii
Figure 29. Location of intake control works structure. De-sanding basin would be located along
the right side of the photography. Overflow spillway would be excavated through the
rock on the left side of the photograph. Photograph taken looking upstream ........................ 39
Figure 30. Glacier Fork run-of-river tunnel and penstock profile with existing ground based on
the USGS NED shown ................................................................................................................ 40
Figure 31. Run-of-river distribution of monthly power generation ............................................................ 42
Figure 32. Typical Access Road Cross Section ............................................................................................. 44
Figure 33: Road Access Alternatives for Glacier Fork ................................................................................. 45
Figure 34. General land status map with the three access alternatives shown ......................................... 49
Figure 35. Knik River Public Use Area: Management Units (From KRPUA Management Plan) .................. 50
Page I iv
1. Executive Summary
The Alaska District, under the Corps of Engineers Planning Assistance to States program, performed a
reconnaissance study for hydropower generation on the Glacier Fork tributary of the Knik River in
Southcentral Alaska. The Glacier Fork watershed lies approximately 60 miles northeast of Anchorage,
Alaska in the Chugach Mountains within the much larger Knik River watershed.
Three different hydropower generation alternatives were examined to determine whether further pre-
feasibility studies are warranted. For each alternative, a concept design was developed with potential
annual power generation estimated and potential fatal flaws identified.
The most significant risks identified that apply to all alternatives considered are those risks associated
with Knik and Mt. Marcus Baker glaciers. These include:
• Formation and subsequent failure of a glacial dammed lake upstream from the project
area
• Continued retreat of the Knik Glacier allowing Glacier Fork to flow directly into the Knik
Glacier valley, thereby bypassing the downstream canyon and all alternatives
The three alternatives developed are listed below with key issues highlighted:
• Glacier Fork Canyon Dam-Alternative 1
o Based on regional sedimentation estimates, the small reservoir created would fill with
sediment in less than 10 years. This flaw precludes further study.
o Seasonal power generation during 4 summer months of the year with minimal power
produced during the remaining 8 winter months.
• lower Glacier Fork Dam-Alternative 2
o Based on regional sedimentation estimates, the small reservoir created would fill with
sediment in less than 50 years. A significant portion of the sediment would be bedload
material.
o A large 3,350-foot-long by 650-foot-tall gravity dam would be required. The estimated
cost for the large gravity dam project feature would be prohibitively expensive for this
medium sized hydropower project.
o Seasonal power generation during the four summer months with significantly less
power generated during the remaining eight winter months.
• Glacier Fork Run of River-Alternative 3
o High level of uncertainty associated with sediment erosion of hydropower equipment
and structures
o High project cost
o Seasonal power generation during 4 summer months of the year with minimal power
produced during the remaining 8 winter months
Page 11
Based upon the risks associated with any project located along Glacier Fork, the limited winter power
generation, and high costs associated with constructing a large dam or developing a run of river
alternative, no further study is recommended for hydropower generation on Glacier Fork.
Page I 2
2. Introduction
2.1. Purpose and Scope
The Regional Integrated Resource Plan (RIRP) prepared by the Alaska Energy Authority (AEA) identified
the Glacier Fork project as a potential new resource for the region. However, the project was newly
proposed and little technical information was available. The Glacier Fork project proposed in the RIRP
was a 75-Megawatt hydroelectric project generating an estimated 327,538 Megawatt hours annually
with a capital cost of $330 million dollars.
The Alaska Energy Authority requested the U.S. Army Corp of Engineers (USACE) to perform a
reconnaissance hydropower study of the Glacier Fork of the Knik River (referred to as Glacier Fork in this
report). This study was jointly funded by AEA and USACE through the Corps of Engineers Planning
Assistance to States cost share program. The purpose of this reconnaissance report is to determine
whether a project has sufficient promise to warrant more detailed study. This is accomplished by
developing conceptual alternatives, performing a preliminary economic analysis and indentifying critical
issues rather than formulating detailed approaches or solutions. Cost information was obtained from
generalized cost curves and data from similar projects. The results from this reconnaissance study can
be used as a basis to proceed, or not proceed, into a more detailed feasibility study.
A team consisting of engineers and environmental scientists prepared this report. The scope of work
included:
• A field reconnaissance
• Evaluation of the basin hydrology and energy production potential
• Examination of regional and site specific geology
• Development of several conceptual alternatives
• Estimates of energy production and facility costs
• Preparation of this reconnaissance report
This report provides an initial reconnaissance level review of several potential hydropower projects on
Glacier Fork and provides the information necessary to evaluate pursuing more detailed feasibility
studies.
Page I 3
Fleur• 1. Project Area
2.2. Previous Studies
There are no existing reports evaluating the hydropower potential of Glacier Fork. There is one study
that evaluated hydropower generation within the Knik River valley. A project report was developed in
the 1950's that evaluated the energy potential of the seasonally impounded lake George. There is no
discussion of Glacier Fork within the lake George hydropower reconna issance report (Hack, 1954).
limited information was provided by Glacier Fork Hydropower llC for inclusion in the RIRP; however, at
the time there was no hydrologic data available for Glacier Fork. Based on estimated flow conditions at
the site and limited storage, it was understood that Glacier Fork would offer limited system flexibility,
would not contribute significantly to the region's planning reserves, but could still contribute significant
renewable energy to the region.
Page 14
The RIRP (Black & Veatch, 2010) was an economic plan developed to guide future capital investment in
generation and transmission options for the region comprising the service areas of six interconnected
public utilities stretching from Fairbanks to Homer.
The RIRP recommended additional reconnaissance level effort to further define the hydropower
potential at Glacier Fork and look for potential'fatal flaws' for hydropower development at this location.
2.3.Accessibility
At the present time the only practicable access to the Glacier Fork basin (Figure 1) for reconnaissance
purposes is by helicopter. There is an unimproved four wheeler trail that begins from the existing road
system near Palmer and roughly follows an existing Revised Statute (RS) 2477 right-of-way along the
north side of the Knik River until it crosses Friday Creek and a prominent rock outcrop named Wolf
Point. The trail then transitions onto the more active Knik River braided plain and continues for another
6 miles to the mouth of the Glacier Fork Canyon. This trail then continues along the west rim of the
Glacier Fork canyon and into the Metal Creek drainage, providing access to several mining claims in the
area. Recreational users can gain access to the Knik Glacier and Upper Glacier Fork valley (also known as
Grasshopper Valley) by ferrying across Glacier Fork with portable boats and hiking overland into
Grasshopper Valley. There are also several unimproved landing strips located within the Upper Glacier
Fork basin.
Feasibility level studies would likely utilize helicopters for access to this area for most studies including
geotechnical borings.
Development of a hydropower site would require improved access, either through construction of an
all-season road or construction of a runway combined with a temporary winter road during
construction. Construction and service access to Glacier Fork is discussed in section 7.
3. Hydrology, Hydraulics and Power
3.1. Study Area
The study area for this hydropower reconnaissance report encompasses the Glacier Fork drainage,
which drains an area of approximately 327 square miles measured where the river flows into the Knik
Valley (Figure 2). The Glacier Fork watershed lies approximately 60 miles northeast of Anchorage, Alaska
in the Chugach Mountains within the much larger Knik River watershed. The Chugach Mountains extend
from southwest to northeast along the North Gulf of Alaska coastline in Southcentral Alaska. This
mountain range provides a significant barrier to precipitation, dividing the region into two climate
zones: the wetter maritime zone to the south of the mountain range and the drier transitional climate
zone to the north of the mountain range. The Glacier Fork basin is further subdivided into two main
watersheds: Metal Creek (92 square miles) and Upper Glacier Fork (232 square miles). These two
watersheds are shown in Figure 2.
Page I 5
Metal Creek
Watershed
Upper Glacier Fork
Watershed
4.5 9 Mile s
Fleur• 2. Glacier Fork basin (Outlined in Red). USGS Gace (15280900) shown as a blue circle with the two major sub-basins
Metal Creek and Upper Glacier Fork shown.
The climate of the Glacier Fork basin is sub-arctic, characterized by a short melt-season from late May
through October and large annual temperature variations . During the winter precipitation falls primarily
as snow; in the summer, precipitation falls mainly as rain but snow can occur year round at the highest
elevations. There are no weather stations within the Glacier Fork basin. The closest weather station with
a long-term record is the Palmer Airport Weather Station, located approximately 21 miles to the west at
an elevation of 220 feet above sea level.
3.2. Topographic Data
As with most of Alaska there is limited topographic data available for the Glacier Fork area. Data that is
available has been derived from the original USGS quadrangle topographic mapping in the 1950's and
1960's. This original mapping information has been incorporated digitally in the National Elevation
Dataset (NED), which is continually updated as new information becomes available. The 1 arc-second
NED coverage was utilized in this report to evaluate conceptual hydropower alternatives. The NED
dataset was compared with a dataset derived from light Detection and Ranging (LIDAR) dataset for an
area with similar topography that includes a deep canyon. The NED was found to provide a comparable
storage versus elevation curve and is considered suitable for use at this conceptual stage. This
comparison is shown in Appendix A.
Page I 6
3.3. Watershed Characteristics
The Glacier Fork watershed is on the north side of the Knik River, approximately 21 miles up the Knik
Valley from Palmer. Metal Creek lies just to the west of Glacier Fork and flows into it 1.5 miles upstream
from the downstream end of the Glacier Fork canyon. The Glacier Fork headwaters lie approximately 35
miles up valley on the flanks of Mt. Marcus Baker. The drainage area of Glacier Fork at the mouth of the
canyon is approximately 327 square miles with approximately 37 percent of this area covered by
glaciers. The watershed is largely undeveloped with several trails and improved landing strips
throughout the lower elevations near the Knik Glacier. The Mt. Marcus Baker Glacier is the largest
glacier and extends roughly 20 miles from the summit of Mt. Marcus Baker to its terminal moraine. The
USGS gaging station on Glacier Fork lies approximately 10 miles downstream from this terminal moraine
The Upper Glacier Fork basin is characterized by steep mountainous terrain, glaciers, and relatively little
soil cover. Elevations range from 800 feet to the summit of Mt. Marcus Baker at 13,176 feet with a basin
average elevation of 5,530 feet. Approximately 43 percent of the upper Glacier Fork basin is covered by
glaciers with several large valley glaciers extending off the flanks of Mt. Marcus Baker. The river begins
at the toe of the Mt. Marcus Baker Glacier and flows approximately 8 miles through Grasshopper Valley
before flowing through a deep bedrock canyon for 7 miles. Downstream from the canyon, the river
flows across a large un·vegetated glacial outwash fan before flowing into the main fork of the Knik River.
Watershed characteristics for these two tributaries as well as several nearby watersheds (Knik River,
Matanuska River, and Little Susitna River) with USGS gaging stations are provided in Table 1.
Table 1. Watenhed Characteristics.
USGS Gage Area Average Average Annual Glacier Area
Watershed Number Square Elevation Precipitation (square (feet) Inches (PRISM
Miles 2000) miles)
Glacier Fork N/A 327 5192 96 121 (37 %)
Upper Glacier Fork 15280900 232 5530 112 100 {43 %)
Metal Creek N/A 92 4344 40 21 (21 %}
Knik River 15281000 1219 3608 121 529 {43 %}
Matanuska River 15284000 2064 4256 26 286 {14 %)
Little Susitna 15290000 63 3647 48 3
3.4. Climate and Hydrology
3.4.1. Regional Climate
No weather stations are located within the Glacier Fork drainage basin. Precipitation and temperature
information can be characterized over the basin using regional information. The basin lies within the
Southcentral Alaska climate region and is influenced largely by the northern Pacific Ocean. Annual
Page I 7
precipitation within the region is very high towards the Gulf of Alaska and decreases towards the
northwest farther inland. Air temperatures are moderate due to this maritime influence.
Average annual precipitation estimates for the Glacier Fork sub-basins were developed from the 2000
Parameter-elevation Regressions on Independent Slopes Model (PRISM) dataset and are presented in
Table 1. The average annual precipitation for Upper Glacier Fork and Metal Creek is estimated to be 112
inches and 40 inches, respectively. This large difference in average annual precipitation calculated using
the PRISM data matches conclusions from a 1986 study (Mayo, 1986) that examined average
precipitation in the Knik River watershed using the equilibrium line altitudes (ELA) of the glaciers
throughout the Knik basin. The 1986 study concluded that there are strong variations in the ELA within
the Knik basin which corresponds to much higher runoff and precipitation occurring in the southern and
eastern areas of the Knik River basin.
The closest weather station to Glacier Fork is in Palmer (Station No. 025331) with 39 years of data. The
station is approximately 21 miles to the west at an elevation of approximately 200 feet above sea level.
Average, maximum, and minimum temperatures at this station are shown in Figure 3.
80
60
40
20
£ ..
I! 0 {!
-211
.4Q
oliO ,., lllr lily
Fleur• 3. Averaee, maximum and minimum air temperature for Palmer (WBAN 25331).
Several weather stations are in the adjacent Matanuska basin with long-term temperature and
precipitation records. Annual precipitation trends for the five stations with long-term records are shown
in Figure 4. The stations show that typically August and September produce the maximum precipitation
in this region.
Previous studies estimated that high flows on the Matanuska River are a result of both rainfall events
(51%) and snow and ice melt events (39%). Based on similarities in the two basins, Glacier Fork is likely
to respond similarly with high flows caused by either high temperatures and or rainfall events.
Page 18
3.5 ,
c-I ~ 3 1
N .!I 2.5
00 en
.-4
c 2 ..
0 ...
"' -a 1.5
~ a. 1 : t 0.5
~
0
Jan
-Palmer AP (025331)
-Lazy Mountain (505464)
-sutton 1W (508915)
-Tahneta Pass (508945)
-Palmer Job Corps (506870)
Feb Mar Apr May Jun Jul Aug Sep
Flcure 4. Precipitation at 5 nearby weather stations.
3.4.2. Stream flow Patte rns
Oct Nov Dec
The USGS installed a stream gage on Glacier Fork (referred to as Upper Glacier Fork in this report) in
October 2010. At the time of this report preparation, only provisional data was available for Water Year
(WY) 2012. The USGS continuous discharge data for Upper Glacier Fork are shown in Figure 5 with
monthly averages tabulated in Table 2. The discharge hydrograph for the Upper Glacier Fork drainage
indicates that from about the beginning of October until mid-April, flows steadily decrease. Rising
temperatures in May initiate snowmelt and the consequent runoff in the watershed. Annual peaks likely
occur in July and August when glacial melt and rainfall storm runoff coincide. Stream flow declines in
August and September as air temperatures cool and snow melt and ice melt decrease. Occasional peaks
are likely to occur in the fall as a result of storms.
The average annual flow for the Upper Glacier Fork gage WY 2011 and 2012 was 905 and 824 cubic feet
per second, respectively, with the highest average daily flow of 6,050 cfs occurring on September 23'
2012 and the lowest flow of 50 cfs on March 27, 2011.
Page I 9
Table 2. Upper Glacier Fork (15280900) averace monthly dlscharce (WY2011·2012)
Month Discharge
(cfst
January 72
February 61
March 51
April 83
May 534
June 2,429
July 3,130
August 2,199
September 1341
October 178
November 102
December 82
Annual 866
7,ooo...-------------------------------------.
1,000
5,000
4,000
~ • £3,000
2,000
1,000
0~~==~======~~----~----~~====~====~~~---r------~~
Oct
2010
Jan
I
Apr Jul
2011
Oct Jan
I
Apr Jul
2012
Fleur• 5. Measured dlscharc• data for upper Glacier Fork (15280900). Data Is provisional for WY 2012.
Oct
Generally, for hydropower analysis, a stream gage record should be extended if the available record is
less than 20 years. Nearby stream gage records on the Knik River (1528400), Matanuska River
(15284000), and Little Susitna River (1529000) were examined to extend the Upper Glacier Fork record
based on regression of concurrent discharge values. Figure 6 shows the chronological avai labi l ity of
USGS flow data for these nearby stream gaging stations.
Page 110
Glacier Fork
(15280900)
Matanuska
(15284000)
little Susitna
(15290000)
Knik
(15284000)
I
I
I
I I II
I
I .I IIIII Ill
1/1/1940 1/1/1950 1/1/1960 1/1/1970 1/1/1980 1/1/1990 1/1/2000 1/1/2010
Flcure 6. USGS Stream caces used In this study with periods of record shown. A solid blue bar Indicates a continuous dally
record; the dashed bars indicate s seasonal operation.
Simultaneous flows were examined for Upper Glacier Fork and each of the three longer term gage
records. A comparison of concurrent flows (May 1-30 September) between Glacier Fork, Knik River,
and Matanuska River are shown in Figure 7. Upper Glacier Fork discharge did not correlate well with the
Little Susitna River. All three watersheds are distinctly different with characteristics listed in Table 1.
Average annual runoff for the four watershed is show in Table 3.
Table 3. Watershed Runoff for WYZOll and WYZOlZ.
Drainage Average 2011 Annual 2012 Runoff Watershed Area Runoff Runoff (in) (Sq. Mi.) (in) (in)
Knik River 1
1219 78 84 78 (15281000)
Matanuska River1
2064 26 23 28 (15284000)
little Susitna 63 44 36 51 (15290000)
Upper Glacier Fork 232 51 53 49 (15280900)
1Gage is operated seasonally. Historic winter flows were utilized to calculate average annual values.
Page Ill
7000
6000
ii'5ooo
!.
-;4000 ...
:i 3ooo
i
'6 2000
1000
0
0 10000 20000 30000 40000 50000 60000 70000
Knik River (ds)
7000
6000
ii' 5000
:E. ... 4000
25 ... = 3000 ,.
II
'6 2000
1000
0
0
•
Y• 0.2213•
R'. 0 .6091
10000 20000 30000 40000
Matanuska River (ds)
50000
Fleur• 7. Upper Glacier Fork concurrent summer (May 1-October 1) flows plotted aealnst the Knlk (left), Matanuska (rleht).
Data from WY 201lls shown In blue and data from WY 2012 Is shown In Red.
Initially it was expected that the discharge in the Knik River would correlate better with Upper Glacier
Fork discharges, as Glacier Fork is a sub-basin of the Knik River. However, the Knik River is heavily
influenced by the increased maritime rainfall with a large percentage of glaciated terrain below 4,000
feet in elevation and a lower equilibrium line altitude. The Glacier Fork drainage is drier with a larger
percentage of glaciers at higher elevations similar to the Matanuska Watershed. Trabant and Mayo
describe the relationship between altitude and runoff for a glacier in Southcentral Alaska. This
relationship is shown in Figure 8. Most of the glacier runoff originates from glaciated areas below an
elevation of approximately 6,000 feet. The Knik watershed is more heavily glaciated at lower elevations
when compared with Upper Glacier Fork and the Matanuska River. Approximately 70 percent of the
glaciers within the Knik watershed lie below an elevation of 6,000 feet as opposed to only 50 percent for
the Matanuska and Glacier Fork basins. The Matanuska River correlated better to concurrent flows on
Glacier Fork in both magnitude and timing. Peak flows on the Knik River occur approximately 1 month
later than on the Matanuska and Glacier Fork rivers.
The liner regression relationship developed from concurrent flows in the Matanuska River and Upper
Glacier Fork was then used to extend the summer (May 1-October 1) Upper Glacier Fork record from
approximately two years to the same length as the Matanuska River, approximately 38 years. Figure 9
shows a comparison between the predicted and measured summer flows for WY 2011 and 2012. Winter
flows calculated using this regression equation yielded un-realistically high flows, which were on the
order of two to three times larger than were measured during the two winters of gaging.
Page 112
1-10,000
w w
LL
~
BASIN LOSSES BASIN GAINS
New firn
w g Basin losses-Total
1-
6 < 5,000
0
-20 -15 -10 ·5 0 5 10 15
WATER EQUIVALENT, IN FEET PER YEAR
14000
12000
10000
--Ql
Ql 8000 :t:.
6
i 6000 >
Ql
iij
--Knik
--Matanuska
2000
--Glacier Fork
0 ~·--·---,.----, --~---~-
0 100 200 300 400 500
Glacleted Area (sq. miles)
20
600
Fieure 8. Top-Altitude distribution of precipitation as rain and snow, Ice melt, snowmelt, and runoff for a &lacier In
Southcentral Alaska (From Mayo and Trabant, 1979). Bottom -Glaciated area versus elevation for each watershed.
Page 113
Hydropower generation in the winter (October 1-May 1) is critical for any project in Alaska . The
average winter runoff from the Upper Glacier Fork basin during the period of record was 6 percent of
the annual runoff. The period of record average winter runoff on the Matanuska and Knik rivers is 13
percent of the annual total runoff. Util izing either gage to estimate winter flows on Glacier Fork will
result in high estimates for winter flow. The average winter flows from two season of gaging were used
to extend the winter record as a more conservative and r ealistic estimate for this project. The lack of
winter flow on Upper Glacier Fork can be attributed to the high elevations within the basin. Other high
elevation glaciated basins produce very little runoff in the winter months. Average winter runoff from
the West Fork of the Eklutna River is 4 percent. This smaller basin has a similar average elevation and
percent of the watershed covered with glaciers as the Upper Glacier Fork Basin.
4000
3500
3000
.... 2500 'a -• ~2000
II .c
1.1 5 1500
1000
500
0
May-11 Jun-11 Jul-11 A ug-11 Se p-11 May-1 2 Jun-12 Jul-12 A ug-12 Sep-12
• Meas ured Flow • Predicte d Flo w
Fleur• 9. Comparison of measured and predicted averace monthly flows for Glacier Fork.
The extended Upper Glacier Fork discharge record was utilized to calculate average monthly flows and a
flow duration exceedance curve. These data are then utilized to estimate hydropower energy
production for each of the reconnaissance alternatives evaluated in this report.
In order to evaluate alternatives below the confluence with Metal Creek, average monthly discharge
from Metal Creek is also required. Discharge on Metal Creek was estimated by scaling the long-term
discharge record for the Little Susitna River with an adjustment made for both the differences in
drainage area and differences i n average annual precipitation. Figure 10 shows the estimated mean
monthly flows for both watersheds, as expected flows on Upper Glacier Fork are much larger and peak
later in the year than the smaller less glaciated Metal Creek Watershed .
Page 114
3,000 11,000
2,500 5,000
2,1111 .. 000
~1,500
I
1,1111
500
0
Jan --.lui 5ep -Percent EIICeedance
Figure 10. Upper Glacier Fork (blue) and Metal Creek (green) estimated mean monthly flows on the left and percent
exceedance on the right.
These estimated flows can be combined to estimate hydropower potential for alternatives located
downstream from the confluence of Glacier Fork and Metal Creek.
The 100-year stream flows (Table 4) for these basins were estimated using the USGS Regional
Regression Equations for Alaska.
Table 4. Estimated 100-Year Flood Flows.
Average Annual
Precipitation 100 Year Flow (CFS) Area (Sq. Mi.) (USGS 1986) (5-95% Confidence Limits)
(In)
Upper Glacier Fork 232 112 32,600
(15280900) (15,550-68,500)
Metal Creek 92 55 6,770
(3,360-13,600)
3.4.3. Hydrologic Uncertainty
Considering the short stream flow record on the upper Glacier Fork and lack of stream flow record at
points lower in the watershed, it is important to consider uncertainty and inter annual variability and
how representative the short 2-year stream gaging record will be of the long-term average annual
hydrograph.
Water year 2011 is the only year with a complete final set of discharge data available. Provisional data
was available for water year 2012. Regional data available from the Alaska Climate Research Center
indicates that the summer snowmelt season for 2011 was cooler than average for Southcentral Alaska.
This is consistent with a close long-term weather station, Lazy Mountain, which reported below average
temperatures during the summer (May-September) snowmelt season. Based on the closest first order
weather stations, precipitation was near normal in this region of Alaska. Precipitation data from the
Page 115
Natural Resource Conservation Service (NRCS) also indicates that precipitation to the south and east of
Glacier Fork (northern Cook Inlet-98%, Kenai Peninsula -102% and Western Gulf-100%) was average
for the 2011 water year. The N RCS data is based on a network of weather stations that tend to be at
much higher elevations and are instrumented to accurately measure precipitation that falls as snow.
Data was examined from the same sources for WY 2012 indicating that, in general, temperatures were
below average and precipitation above average for Southcentral Alaska. The seven closest Snotel sites
reported 133 percent of their average annual precipitation.
WY 2011 and WY 2012 average monthly discharges for the Matanuska River and Knik River are shown
below (Table 5) and compared with the long term gage averages.
Table 5. WY 2011 and 2012 ave race monthly flows for the Knik and Matanuska River. (values in cfs).
May June July August September Average
Mean 4,230 12,990 22,240 21,580 11,220 14,480
Knik River 2011 5,320 15,980 23,900 21,120 12,280 15,930
(+26%) (+23%) (7%) (-2%) (+9%) (+10%)
2012 3,630 13,010 19,320 17,910 19,450 14,850
(-14%) (0%) (-13%) (-17%) (+73%) (3%)
Mean 2,990 10,000 13,000 9,810 4,810 8,150
2011 3,175 8,142 11,400 8,345 3,490 6,940
Matanuska (+6%) (-19%) (-12%) (-15%) (-28%) (-15%)
River
2012 2,473 12,901 12,219 8,333 9,588 9,075
(-18%) (+29%) (-7%) (-15%) (+99%) (+11%)
Climate during WY 2011 was slightly cooler than average with an average amount of precipitation likely
in the Glacier Fork area. The climate during WY 2012 was cooler than normal with likely more
precipitation than normal in the Glacier Fork area. Overall, it appears that WY 2011 was roughly
"normal" with no extremes expected in terms of the quantity of runoff during this period. WY 2012 was
generally cooler than normal with above average precipitation.
The coefficient of variation is a commonly used metric to describe the inter-annual variability of stream
flow and can vary greatly between watersheds. Studies have found that inter annual variability is at a
minimum for catchments that are approximately 40 percent covered with glaciers and goes up as the
glacier cover increases or decreases from this value (Willis, 2005). The coefficient of variation for the
three nearby stream gages with long-term records is listed in Table 6.
Page I 16
Table 6. Coefficient of Variation for Lon& Term Stream caces.
Uttle Susitna Matanuska Knik River
River River
Percent 5% 14% 43% Glaciers
Coefficient of 0.24 0.16 0.14 Variation
The calculated coefficient of variation for these watersheds matches the trend that moderately glaciated
watersheds tend to be less variable than un-glaciated and slightly glaciated watersheds. Discharge for
the Upper Glacier Fork watershed (43% glaciated) is likely to show less variability from year to year than
similarly sized less glaciated watersheds.
Consider i ng the expected lack of annual variability, the alternative to extending the Glacier Fork record
through correlation would be to utilize the 2-year record "as-is" to develop design inflows. The two
methods produce similar results for this watershed and are shown in Figure 11. The extended record
was utilized in subsequent analysis for power generation estimates.
10,000-r---------------------------------,
9,000
a.ooo
7,000
6,000
:! ~ 5000 ll •
9.
.... 4.000
3,000
2,000
1,000
50 60 70 10 90 100
Percent EXCEEDANCE
Ficure 11. Comparison of the exceedance duration curves cenerated usinc Extended Upper Glacier Fork discharce record
(red) and Two years of measured stream cace data on Upper Glacier Fork (blue).
4. Regional Geology
4.1. Regional Setting and Geomorphology
Glacier Fork of the Knik River is located in the Chugach Mountains in Southcentral Alaska . The Chugach
Mountains are an accreted terrain of structurally complex metamorphic and igneous rocks bounded by
major faults (Bradley and Miller, 2003; Burns et al, 1991; Kusky, et al, 1997; Yehle and Schmoll, 1988).
The terrain in the Glacier Fork area is dominated by three geomorphologic features: mountains, glaciers,
Page 117
and the Knik Valley. The mountains in the immediate vicinity of Glacier Fork and Metal Creek are low,
with summit elevations that range from around 6,500 feet to more than 7,600 feet. Higher mountains
are present to the west with summits above 10,870 feet at Mt. Marcus Baker (Anchorage 1:250,000
Quadrangle Map, USGS 1985 revision). The higher mountains in the west produce numerous glaciers,
and many of those near the study area coalesce at the Knik Glacier. The Kn i k Glacier is the largest glacier
in the area and terminates near the mouth of Glacier Fork. The Knik Valley is a major topographic
feature characterized by a broad glacial valley with steep sides and a wide flat bottom formed by
deposition of extensive sand and gravel outwash sediments from the Knik Glacier. The elevation at the
mouth of Glacier Fork is approximately 250 to 275 feet above sea level. The Kn i k Valley trends to the
west-northwest where it converges with the Matanuska Valley and forms the Knik Arm.
Reure 12. Reeionai Topoeraphic Features Surroundinc Glacier Fork of the Knlk River. Excerpt from Anchoraee 1:250,000
Quadranele Map, USGS 1985 revision.
4.2. Geologic History
South central Alaska has had an active history of tectonic plate interaction that resulted in complex
geology and mountainous regions dissected by large fault systems. Plate subduction during the
Mesozoic Era produced a system consisting of volcanic island arc, subduction trench, and continental
plate volcanic range (Bradley and Miller, 2003; Burns et al, 1991). Marine sediments deposited on the
ocean floor along the subduction trench slope slid down the trench slope as turbidity currents and
Page 118
formed massive turbidite deposits. Continued subduction of the oceanic plate beneath the continental
plate compressed sed i ments at the bottom of the trench against the continental margin and formed an
accretionary wedge of sedimentary and metamorphic rocks (Bradley and Miller, 2003; Burns et al, 1991;
Kusky, et al, 1997; Yehle and Schmoll, 1988).
Abyssal plain
Mid-ocean ridge I
Accretionary
Outer trench wedge
Trench J
:\lagm:~tic
arc
Fleur• 13. Schematic showlnc conceptual formation of subduction zone, trench, accretionary wedc• at continental
marcln, Modified from Bradley and Miller (2003) and Connelly (1978).
Tectonic processes resulted in the formation of the Chugach Mountains from sediments accreted onto
the continental margin during the Cretaceous Period (Burns, et al, 1991; Kusky, et al, 1997). Volcanic
activity injected small igneous bodies into the accreted terrain during the Cretaceous and Paleogene
Periods (Burns, et al, 1991). The processes related to tectonic plate subduction have resulted in
accretion of oceanic material onto the continental plate, metamorphism of those sediments, the
building of mountain ranges, and extensive faulting (Burns, et al, 1991). The tectonic processes that built
the Chugach Mountains are still active in Southcentral Alaska and present a continued geologic hazard.
The region was extensively glaciated during the Pleistocene. During this time, the Knik Glacier extended
to coalesce with the Matanuska Glacier and other glaciers near Palmer (Yehle and Schmoll, 1988). The
glacier has since retreated to its present location in the Knik Valley. The Knik Valley was modified by
glaciation into a large U-shaped valley. Extensive outwash deposits filled the lower portions of the valley
as the glacier retreated. The Glacier Fork gorge adjacent to the Knik Glacier appears to be a relatively
recent drainage feature that was incised into rock.
The Mt. Marcus Baker Glacier within the Glacier Fork basin has been retreating and leaving the
Grasshopper Valley un-glaciated in recent times. Grasshopper Valley is a large U-shaped valley that is
filled with glacier outwash deposits.
4.2.1. Geological Hazards
4.2.1.1. Earthquake
Earthquakes are a significant geologic hazard for a dam at Glacier Fork . Large damaging earthquakes are
possible in the region (Haeussler et al, 2000). Associated with the earthquake hazard is ground motion
induced soil liquefaction, slope instability, facility structural damage, and nearby glacial lake break-out
flooding. Strong ground motions are capable of causing liquefaction in loose granular soils, especially in
the silt and sand size range. Coarser grained soils are less inclined to liquefy due to ground motions. A
Page 119
dam and penstock, constructed in sound rock, would not be affected by soil liquefaction. Access roads,
transmission towers, and other structures constructed in the Knik Valley alluvium may be at risk. If
possible, the powerhouse and outlet structure should be founded on rock. Concrete structures on rock
should be designed to resist strong motions. Appendix B provides some preliminary probabilities of a
large 6.5 to 7.5 magnitude earth quake occurring in the vicinity of Glacier Fork in the next 100 years.
Strong ground motions may induce localized rockfall and slope failure in susceptible slopes. Site
investigations during design and construction should identify slopes susceptible to failure. Nearby Lake
George has a history of break-out floods with the most recent flood occurring in 1967. Strong ground
motions could cause the moraine material that impounds the lake to fail and result in a break-out flood
that could damage access roads and transmission towers in the Knik Valley.
4.2.1.1. Glacier Advance or Retreat
A second major geologic hazard for a hydropower project at Glacier Fork is the Knik Glacier just to the
south of Glacier Fork. A glacial advance of the Knik Glacier could compromise facilities near the mouth of
the Glacier Fork canyon, transmission facilities, or other structures near the current glacier terminus. In
addition, a glacier advance could also cause the Knik Glacier to ride across Glacier Fork at the mouth of
Grasshopper Valley and potentially create an upstream uncontrolled glacial dammed lake. There would
essentially be no mitigation measures for a glacial advance. The current USGS mapping, based on 1950's
photography, shows the Knik Glacier impinging upon Glacier Fork just as it exits Grasshopper Valley.
A continued glacial retreat could allow Glacier Fork at the lower end of Grasshopper Valley to bypass the
Glacier Fork canyon and flow directly into the Knik Valley and down along the margins of the Knik River.
This would essentially eliminate inflow into a hydroelectric project constructed on Glacier Fork. A low
lying area approximately 4,500 feet long lies between two bedrock outcrops where the Knik Glacier
essentially buttresses Glacier Fork River through this reach, forcing it to flow to the northwest and into
the Glacier Fork canyon. A photograph of this location looking downstream is shown on the cover of this
report. Figure 14 shows a series of aerial imagery (1950,1979,1995, and 2011) with the extent of the
Knik Glacier lateral retreat since 1979 visible.
One potential mitigation strategy to prevent Glacier Fork from bypassing the downstream canyon might
be to construct a diversion dike. This dike would be built in the area of the low divide shown in the
bottom time series of Figure 14. This option should be viewed with caution as there may be no feasible
way to construct and maintain a diversion dike at this location. There is potential for this low area
between Glacier Fork and the Knik Glacier to contain frozen material and massive ice beneath visible
gravels.
Page I 20
Flcurel4. USGS Map ('"1950s) and aerial view of the Knlk Glacier adjacent to Glacier Fork. The red line indicates the
approximate toe of the ctacler as shown on the 20lllma,e. The orance area Identifies the low divide between Glacier Fork
and Knik Drainaces.
Page I 21
Recent data show that the Knik Glacier has been following the regional trend for glaciers in the western
Chugach and thinning at a rate of 2.1 feet per year between 1954 and 2006 (Berthier, Schiefer, Clarke,
Menounos, & Remy, 2010). However, the Harvard Glacier adjacent to the Glacier Fork watershed to the
east is gaining mass and advancing during the same period. Currently, the only glaciers in Alaska that are
significantly advancing are glaciers in coastal regions with a large accumulation areas located at higher
elevations (O'neel, 2012).
In addition to a glacier advance or retreat, there could be secondary impacts associated with changes in
upstream glaciers. Continued changes in climate could result in significant changes in melt water inflow
and sediment transport that could have adverse effects on hydropower.
4.2.1.2. Glacier Fork Jokulhlaups
Jokulhlaups, also known as glacial dammed lakes (GDL), form for several different reasons. The major
hazard presented by glacier damned lakes is flooding and sediment transport, which would occur as a
result of the ice dam failing. In many places GDL's fail annually, while in other cases the situations
change rapidly from year to year without a consistent annual pattern of GDL release. Often GDL's with
the greatest hazard are associated with ice free tributaries that are blocked off by an active valley glacier
downstream.
The USGS in 1971 inventoried glacial dammed lakes throughout Alaska (Post & Mayo, 1971) using the
best available topographic data combined with overhead and oblique aerial images.
Page I 22
E.
h
Glacier dammed lakes smaller than
0.1 square kilometers (0.04 square mile~~)
c::::>
Former glacier dammed lakes
<:::?
Possible future glacier dammed lakes
@
Location of lakes listed on table
Known glacier outburst flood courses
lnferTed glacier outbunt flood coUJ"IIeS
Flcure 15. Glacier Dammed Lakes and Outburst Floods In Alaska from Post & Mayo, 1971 (modified).
This report identified two large and five small (< 0.1 square mile) former GDL's in the Glacier Fork
drainage basin (Figure 15). They also identified one area adjacent to the Mt. Marcus Baker Glacier as a
potential area for a GDL in the future. A follow-up study by Wolfe in 2010 documented the transient
nature of GDL's. Within the Chugach Mountains, 64 GDL's mapped in 1971 were not apparent in satellite
imagery acquired between 2000 and 2012, and 35 new GDL locations were found in the newer images.
The area identified in 1971 as a possible future GDL (red arrow in Figure 15) was examined on a recent
satellite image. As the tributary glacier recedes, the Mt. Marcus Baker Glacier continues to span the
head of this valley, creating the potential for this ice free area to form a GDL if the much larger valley
glacier blocks water flowing from this tributary valley.
Formation of the glacial dammed lake upstream from a potential hydroelectric project on Glacier Fork
remains a possibility in the future given the current conditions. It would be difficult, if not impossible, to
define the probability of a GDL forming in this tributary during any given year.
Page I 23
5. Sediment Management
Glacier Fork is heavily glaciated and carries a high sediment load. Any hydropower facility construction
along Glacier Fork would need to consider reservoir sedimentation, erosion damage of machinery, and
bypassing sediment for a run-of-river project.
5.1. Reservoir Sedimentation
The Upper Glacier Fork drainage basin above the USGS stream gage is 43 percent glaciated, with the toe
of the Mt. Marcus Baker Glacier lying approximately 8 miles upstream from the alternatives examined in
this report. The upper reaches of Glacier Fork begin at the toe of the Mt. Marcus Baker Glacier and flow
through the outwash plains of Grasshopper Valley. As the Mt. Marcus Baker Glacier recedes, the river
erodes through the glacial outwash in Grasshopper Valley. At the downstream end of Grasshopper
Valley, there are several base level controlling bedrock outcrops upstream and downstream from the
area where the Knik Glacier impinges on the river. The river then spills through a series of canyons
before flowing out into the Knik Valley, depositing bedload material and creating an expansive outwash
plain (Figure 17).
Ficure 16. Grasshopper Valley looklnc towards the Mt. Marcus Baker Glacier. Photocraph taken looklnc upstream.
Page I 24
Flcure 17. Glacier Fork outwash plain. Photocraph taken looklnc downstream.
Sediment transport and sediment yield from the Glacier Fork basin poses a significant operation and
maintenance concern for any hydroelectric project utilizing this river. This would include both storage
projects and a run-of-river project. In general, rivers draining glacierized areas transport significantly
more sediment annually than non-glacial rivers under similar flow conditions. Usually, the sediment load
is transported during a limited part of the year with up to 95 percent transported during the melt
season. The total sediment discharge is divided into bedload discharge and suspended load discharge.
Suspended sediment consists of fine particles, usually clay, silt, and finer sands that are transported
while being held in suspension. The bedload consists of coarse sediment, usually sands, gravels, and
larger particles that are transported on or near the streambed. Typically, to calculate a river's total
sediment load, only the suspended sediment load is measured and the bedload is estimated, usually
within a range of 0 to 20 percent depending upon the river characteristics in non glaciated basins. In
glaciated basins the proportion of bedload will be higher in the upper reaches and decrease in the
downstream direction. Studies on bedload in glaciated basins have shown a significant variability in the
proportion of bedload volume without a consistent pattern. Recent studies on the Matanuska River
estimated the bedload at the terminus of the glacier to be equal to the measured suspended sediment
load (Farrell, et al., 2009). Based on the initial site reconnaissance at Glacier Fork, the proportion of total
sediment load transported as bedload will likely be similar to estimates for the Matanuska River at the
toe of the Matanuska Glacier. Downstream from the Glacier Fork canyon the proportion of bedload
likely decreases dramatically as bedload material is deposited on the outwash plain.
Page I 25
A common method for analyzing average annual sediment transport characteristics and sediment yield
is to develop a site specific relationship between suspended sediment discharge and water discharge,
which is then applied to mean daily flows to calculate the average annual sediment yield. It should be
noted that sediment discharge is not a simple function of water discharge; often the concentration of
smaller silt and clay sized particles is dependent upon availability and not upon the hydraulics of flow.
Rates of sediment transport have not been measured for Glacier Fork. In cases such as this, where little
or no data exist, a regional analysis can be useful to provide preliminary estimates of annual sediment
yields. However, this must be followed up with a more detailed method during feasibility studies.
The USGS (Parks & Madison, 1984) developed several regression equations to estimate sediment yield
from glacierized basins based on drainage area and the percent of the watershed that is glaciated. Two
separate relationships were developed, one for glaciated watersheds in maritime climate regions and a
relationship for glaciated watersheds in continental climate regions. These equations were based on a
limited dataset and may over predict sediment transport rates (Lawson D. E., 1993).
The two regional USGS regression equations (maritime and continental) were applied to Glacier Fork to
estimate average annual sediment yield. Results are shown in Table 7.
In addition to utilizing these regional equations, sediment transport relationships developed for the
West Fork of the Eklutna River were applied to Glacier Fork as a second method to estimate the volume
of sediment transported annually by Glacier Fork. The West Fork of Eklutna River is a smaller (25.4
square miles) watershed located approximately 20 miles to the southwest of Glacier Fork that is
approximately 40 to 50 percent glaciated. Stream discharge and sediment transport was characterized
for this watershed in the mid 1980's (Brabets, 1993). The average runoff from the West Fork is 61 inches
of water, slightly larger than the 51 inches of runoff measured from Glacier Fork (2011 and 2012
average). The average annual sediment yield for Glacier Fork utilizing the sediment discharge
relationship for West Fork of Eklutna River is also shown in Table 7.
The estimated rate of annual suspended sediment yield based on the regional regression equations from
the Glacier Fork basin is between 27 and 51 tons per day per square mile. As expected this estimate is
higher than measured transport rates on Knik River of 27 to 37 tons/day/mi2 reported in the 1984 USGS
study. The total sediment yield of between 32 and 61 tons/day/mi 2 is comparable with estimates for the
identical in size Matanuska Glacier Watershed (at the toe of the glacier), with total sediment load
estimates for this watershed of between 24 and 94 tons/day/mi 2 (Farrell, et al., 2009). Results from both
the regional regression equations and similar watershed analysis (West Fork of Eklutna) are shown in
Table 7.
Page I 26
Table 7. Upper Glacier Fork sediment yield estimate.
Average Daily Suspended Sediment Load (Tons)
Averaae Dally Bedload (Tons)
Total Daily Sediment Yield (Tons)
Regional Regression
Equations
Maritime Continental
11,700 6,200
2,345 1,240
14,045 7,440
West Fork
of Eklutna
Equation
7,700
350
8,050
Estimated Annual Volume (Acre-Ft)1 3, 700 1,950 1,900
1 Volume is based on an assumed density of 100 lbs/ft3 for bedload sediments and 70 lbs/ft3 for
suspended load.
Reservoir sedimentation results from the interaction between upstream sediment supply and the
reservoir trap efficiency. The life expectancy of a reservoir is usually calculated from the ratio of the
storage capacity to the mean annual sediment yield trapped in the reservoir. For large projects a typical
design life for the reservoir would be 100 or more years. This requires enough dead storage (storage
below the power intakes) to accommodate 100 years of sediment accumulation. The percentage of
sediment retained, or reservoir trap efficiency, can be estimated based on the ratio of annual inflow
volume to reservoir volume. Depending on the size of reservoir developed on Glacier Fork, reasonable
trap efficiencies would range from 50 percent to 95 percent.
The estimates for average annual sediment yield should be used with caution as these values are based
on regional equations and an extrapolated sediment discharge relationship from a nearby basin. A more
accurate estimate of the average annual sediment yield from the Glacier Fork basin would require
continuous suspended sediment sampling along with average daily discharge measurements. Suspended
sediment sampling could be accomplished relatively easily at the current USGS stream gage site.
Measurement of the bedload portion of transported sediment would be difficult at the USGS site due to
the high velocities and bedload grain sizes. Considering the size of material deposited downstream from
the Glacier Fork canyon (Figure 18), an accurate measurement of bedload is likely not possible using
traditional bedload sampling techniques.
Page I 27
Fleure 18. Deposited sediment •t the lower end of the Gl•cl•r Fork a.nyon.
5.2. Sediment Erosion of Hydraulic Equipment
Equipment used for hydroelectric power generation is susceptible to damage caused by abrasive
impacts of sediments. Recent experience in the Himalayas has shown that damage to underwater parts
is moderate to severe in practically all run-of-river projects constructed in this region despite the
provision of expensive desilting arrangements (Kaushish & Naidu, 2002, pg. 206). This experience with
hydropower projects on Nepalese rivers with high sediment loads has shown that complicated de-
sanding basins comprise a significant percentage of the project costs and are not always successful.
Generally, repairs are required to the hydropower turbines between 1 and 10 years after construction of
these projects depending on the severity of erosion.
One standard that has been utilized in India is to design desilting basins to exclude all sediment particles
greater than 0.2 mm from entering the hydropower machinery. In Russia a common standard is .25 mm;
however, operational experience with hydropower plants indicates that sediment damage to
hydropower machinery can occur if sediments sizes exceed 0.01 mm (Kaushish & Naidu, 2002, pg. 219).
The final design requires an economic comparison of constructing a larger, more expensive desanding
basin versus the cost of more frequent hydropower machinery repair.
Turbines are the most sensitive component to this abrasive wear. Often the maximum sediment particle
passing through the turbine is used to characterize the risk of turbine damage. However, there are a
number of factors that can influence the process of sediment erosion damage in hydro turbine
machinery. Equally important to sediment size can be sediment hardness. Particles with a Moh's
hardness of greater than 5 are harmful to hydraulic machinery. A list of key factors related to the
erosion of hydraulic equipment is listed below:
Page I 28
• Sediment
o Hardness
o Shape
o Size
o Concentration
• Hydraulic Design Conditions
o Flow rate
o Head
o Rotational speed
o Turbine materials
o Turbine geometry
Hydroelectric projects that include significant storage on Upper Glacier Fork would not require any
additional measures to prevent erosion of hydraulic equipment. However, for a run-of-river project,
erosion of hydraulic equipment will be significant unless an adequate sediment management plan is
developed for the project
Prior to or at the very early stages of any future feasibility study, the average annual sediment yield
should be estimated based on actual measurements on Glacier Fork. Transported sediment should be
characterized to better understand the properties listed above that are associated with erosion of
hydraulic equipment.
6. Conceptual Alternatives Descriptions and Design Considerations
In order to evaluate the feasibility of hydropower generation on Upper Glacier Fork, several conceptual
alternatives were developed. A description of each alternative is provided below with the major project
features listed. In addition to the features listed for each alternative, the following common project
features would be necessary:
• 21-mile-high voltage transmission line and grid integration equipment (described in
Appendix C).
• A 12 to 18-mile site access road to the downstream end of the Glacier Fork canyon.
6.1. Alternative 1 -Upper Glacier Fork Dam
6.1.1. Description of Project Components
The first alternative considered was previously identified in the 2010 Regional Integrated Resource Plan.
The formulation developed for this report varies slightly from the RIRP in dimensions, location, and
configuration. This alternative would consist of (1) a 600-foot-long by 270-foot-high concrete arch dam
forming a reservoir with 13,500 acre feet of storage and surface area of 190 acres at a water surface
elevation of 900 feet mean sea level (msl); (2) a 6,300-linear-foot concrete lined 12-foot-diameter tunnel
with vertical surge shaft; (3) a powerhouse with tail race containing three generating turbines with a
Page I 29
combined output of 80 Megawatts; (4) a 200-foot-long bridge across Glacier Fork and a 18,000-linear-
foot dam access road; and (5) appurtenant facilities.
Flcu,.. 19. Canyon dam layout.
The concrete arch dam would be located at a narrow point in the Glacier Fork canyon just upstream
from the confluence with Metal Creek with a crest elevation of 910 feet (Figure 19). This is based on a
maximum reservoir elevation of 900 feet; at elevations above this, water from the reservoir would spill
through a low saddle at the upper end of the reservoir and flow into the Knik Glacier valley. The US
Bureau of Reclamation Engineering Monograph No. 36 "Guide for Preliminary Design of Arch Dams" was
used to estimate the volume of concrete and a general plan for a double curvature arch dam. Estimated
dimensions of the dam include a 14-foot crest width and GO-foot thickness at the base with 800,000
cubic yards of concrete required for construction. The proposed area of this arch dam is shown in Figure
20, looking downstream towards the confluence of Metal Creek. Construction of a dam at this location
would require access to both sides of the canyon and an aerial cable system for construction spanning
the canyon . In addition to the permanent access road shown in Figure 19, a 13,000-linear-foot
temporary access road and a significant bridge across Metal Creek would be required to gain access to
the right side canyon wall and abutment.
Construction of a dam within this narrow, steep-sided canyon would be difficult and require access
roads to sides of the canyon and an aerial cableway. These items would add to the overall project cost.
Access roads required to reach both abutments would traverse steep+-30 degree slopes to reach the
dam site. Dewatering during construction would require an additional bypass tunnel
Page I 30
Fleur• 20. Canyon D11m Site, photocr•ph t11ken looklnc downstre11m.
The reservoir would be narrow, deep, and impound water for approximately 3.5 miles upstream. The
storage elevation curve generated from the best available data is shown in Figure 21. Limited storage is
available in the canyon below an elevation of 900 feet. Increasing the reservoir to an elevation of 1,000
feet msl would require a second saddle dam approximately 700 feet long and 100 feet high at the upper
end of the reservoir.
1,000
150
;:: 900
~ z
2 850 ..
! _, ... 800
Top of Dead Storage
750
700
10,000 20,000 30,000 40,000 50,000
Flcure 21. Storqe Elev11tlon Curve for Canyon D11m Altern11tlve.
Page I 31
The power intake would be constructed at an elevation of 850 feet, allowing for limited reservoir dead
storage during the life of the project. The penstock would consist of a concrete lined, horseshoe shaped
tunnel that would convey water through the Glacier Fork highlands, exiting adjacent to the powerhouse
and into a short steel penstock before entering each turbine. Three Francis turbines would be located
within the powerhouse, discharging into a tail race channel with a downstream weir designed to keep
the turbines submerged.
The powerhouse facilities would be on a 5-acre developed embankment with an approximately 17,500-
square-foot powerhouse situated on bedrock. The tail water elevation would be controlled by a
downstream weir at an elevation of 290 feet above sea level, providing an estimated gross head of 610
feet.
Power generation was estimated using the flow duration curve method with the plant size selected
based on the 20 percent exceedance point on the flow duration curve. The estimate power generation
for this alternative is 268,000 MWh with a monthly distribution shown in Figure 22 below.
70000
:i: 60000
31 ! 50000
~40000
GJ c
~ 30000
£
~ 20000 +----------------------
10000
0
Ficure 22. Alternative 1 distribution of monthly power ceneratlon.
6.1.2. Site Specific Concerns and Risks and Feasibility
Based on the estimated average inflow and reservoir capacity, this project would have a sediment trap
efficiency of approximately 60 percent. It is estimated that this small reservoir would fill with sediment
within 3 to 6 years, proving to be the fatal flaw for this conceptual alternative.
6.1.3. Conclusions
This conceptual alternative is not feasible due to rapid infilling of the relatively small reservoir created. A
rough order of magnitude cost estimate was not prepared.
Page I 32
6.2. Alternative 2 -Lower Glacier Fork Dam
6.2.1. Description of Project Components
In order to address the fatal flaw associated with a dam and reservoir farther up the Glacier Fork
canyon, a conceptual alternative was considered farther downstream along Glacier Fork (Figure 23),
which would maximize reservoir storage.
This alternative would consist of (1) a 3,350-foot-long by 600-foot tall roller compacted concrete dam
forming a reservoir with approximately 116,000 acre feet of storage and surface area of 870 acres at a
water surface elevation of 900 feet msl (figure 24); (2) penstock integral to the dam leading to a 4,100-
foot-long concrete lined 12-foot-diameter rock tunnel; (3) a powerhouse containing three generating
turbines with a combined output of 100 Megawatts; (4) tailrace with downstream weir to control the
tailwater elevation; (5) a 16,000-foot-long dam and powerhouse access road, and (7) appurtenant
facilities.
A large concrete or roller compacted concrete gravity dam would span the lower Glacier Fork valley just
upstream from where the river flows into the Knik Valley. The crest elevation would be set at 905 feet
with the full pool reservoir elevation at or near 900 feet above msl. A stepped overflow spillway section
would be provided to safely handle the inflow design flood.
A valley cross section at the proposed dam center line is show in Figure 25. This cross section is based
on USGS topographic data (NED), with the canyon section modified based on field measurements made
during the reconnaissance site visit.
Page I 33
5,000 10lXX) F .. t
II
I~
1 '7 --....!.----'-~-
Fieure 23. Lower Glacier Fork dam reHrvoir layout.
1,000
900
800
~
!::.
~ 700 1-
~
...,.j
L.L.I
600
500
50,000 100,000 150,000 200,000 250,000
STORAGE (ACRE-H)
Fleur• 24. Lower Glacier Fork dam storae• elevation curve.
Page I 34
1000
900
800
:E" 700 -c:
0 600 ';i
til > .!! w 500
400
-=-Modified
300
200
0 500 1000 1500 2000 2500 3000 3500
Distance Along Profile (ft)
Fleur• 25. Dam Profile with modifications based on site visit.
The impounded reservoir would provide a minimal amount of seasonal water storage and dead storage
for sediment. Dewatering during construction would be through a diversion tunnel.
6.2.2. Project Specific Power Production Estimates
A power production estimate was developed for this alternative using sequential routing of the
extended flow record for Glacier Fork and Metal Creek . Elevations are based on the best available USGS
digital elevation data with limited field checks using a handheld mapping grade GPS. The following
modeling assumptions were made in these calculations:
• Power plant size was selected based on the 20 percent exceedance point on the flow
duration curve.
• A plant outage factor of 2%.
• The project operates during the summer months as a run-of-river project at the
maximum pool elevation with significant spillage occurring between May 1st and
October 30th .
• Generation from May 1 to October 31 was maximized so that the reservoir was nearly
full on November 1 st each year.
• Tail water elevation is controlled by design of the tailrace and assumed to be constant.
• Environmental flow releases are assumed to be zero.
• A constant turbine efficiency of 87% and generator efficiency of 98% is assumed.
Page I 35
Gross Head (ft) 610
Net Head @ Max Flow (ft) 546
Maximum Plant Flow (cfs) 2500
Number of Units 3-Francis
Nameplate Capacity (MW) 100
Maximum Pool Elevation (feet) 900
Minimum Pool Elevation (ft) 800
Dead Storage (Acre-Ft) 50,000
Active Storage (Acre-Ft) 66,000
The estimated average annual energy production for this alternative is 298,000 MWh with an estimated
plant factor of 35 percent. The monthly distribution of power generation is shown in Figure 26. The
project would operate near the nameplate capacity from the end of May through the beginning of
September with significant spillage during this time period. This alternative would have the advantage of
providing a minimal amount of power during the winter months.
:;:
3:
~ 50000 +--------------
~
~ 40000 +--------------
1&.1
> ~ 30000
0
:::!:
20000
0
Ficure 26. Lo-r Gl•cier Fork distribution of monthly power cener•tlon.
6.2.3. Site Specific Concerns and Feasibility
While having a much larger storage capacity than the canyon dam alternative, the pri mary concern for
this alternative remains sedimentation of the reservoir. The expected reservoir life would still be
extremely short for a large dam project. It is estimated that the available dead storage would be
completely filled in between 15 and 30 years, with the entire reservoir filled within 35 to 65 years.
Page I 36
The largest single civil works project feature for this alternative would be the large gravity dam
constructed of either concrete or roller compacted concrete. A rough order of magnitude cost was
developed for a roller compacted concrete (RCC) dam using the recent unit costs developed for the
Susitna Watana Project (2009) of $110 per cubic yard for in place RCC. Approximately 3.6 million cubic
yards of concrete would be required to construct this large dam at a cost of roughly $400 million dollars.
Due to the large dam required and sedimentation concerns, this alternative was not carried forward.
6.3. Alternative 3-Glacier Fork Run of River
6.3.1. Description of Project Components
This alternative would consist of a run-of-river project with essentially no water storage (Figure 27). The
primary concern for this type of project would be sediment management to prevent erosion of the
hydropower machinery. The intake works would need to be designed to effectively manage the large
incoming sediment load. This alternative would consist of (1) a 100-foot-wide low head dam with three
25-foot-wide tainter gates; (2) 150-foot-long lateral weir with upstream gravel trap leading to a 650-
foot by 250-foot desanding basin with two downstream sluice gates; (3) a second 100-foot-long weir
leading to the power intake structure; (4) a 19, 760-linear-foot concrete lined 14-foot-diameter tunnel
and 1,000-linear-foot steel10-foot-diamter penstock; (5) a powerhouse with tail race containing five
turbines and generators with a combined output of 85 Megawatts; (6) a 35,000-foot-long road to access
the powerhouse and intake works; (7) a 200-foot-long bridge across Glacier Fork; (8) upstream 4,500-
foot-long diversion dike if required; and (9) appurtenant facilities.
9 10 II
Fi1ure 27. Run of river conceptual layout. 'Dog Leg' Channel
Page I 37
The intake works would consist of a low head dam with a concrete control works section spanning
Glacier Fork above the canyon in an area where the grade of the river is controlled by bedrock at an
elevation of approximately 1,000 feet above msl (Figure 28).
The concrete control structure would include three tainter gates to control the upstream headwater
elevation. This low head dam would raise the upstream water surface elevation by approximately 20
feet to provide additional head for flushing of the de-sanding basin. The upstream channel would quickly
adjust to this grade change and fill in with bed material, raising the bed level immediately upstream of
the control works, tapering farther upstream to eventually match the existing streambed.
A 175-foot-long uncontrolled auxiliary spillway would be excavated in the bedrock on the north side of
Glacier Fork with a downstream spillway and stilling basin. The spillway and control works would be
designed to safely pass the inflow design flood.
Fleure 28. Pl1n view of lnt1ke works, de-Andlne biSin, tunnel1nd m1inten•nce bulldlne.
Upstream from the dam, a 150-foot-long low lateral weir would lead to a large de-sanding basin,
measuring approximately 650 feet long by 250 feet wide and 15 feet deep. The basin would include two
large tainter gates at the downstream end with a tail race leading back to the river Figure 29.
Active sediment management would be required on a constant basis in the summer months to maintain
the effectiveness of the de-sanding basin. This active management would require coordinated operation
of the control works gates and downstream de-sanding basin gates to effectively provide flushing flows
through the de-sanding basin. During periodic flushing of the de-sanding basin, power generation would
be interrupted.
Pace I 38
Ficure 29. Location of intake control works structure. De-sandinc basin would be located alone the rlcht side of the
photocraphy. Overflow spillway would be excavated throuch the rock on the left side of the photocraph. Photocraph taken
lookinc upstream.
A second 100-foot-long lateral weir at the downstream end of the de-sanding basin would lead to a 14-
foot-diameter by 19,760-foot-long concrete lined tunnel. The tunnel profile is shown in Figure 30.
Page I 39
IT)
" < s. c;·
::>
2000
1800
1600
1400
1200
1000
800
600
400
200
0
Power House
£~
~; -f--f-
"---
8 +
0
0
0 +
0
0 0 + 0
N
.............
0 0 + 0
"'
STA -
El..Ev
/
-
1()+00. ~
310.(
0
0 + 0 ...
0
0 + 0
"'
Existing Ground p
~~ \ Intake
\ 'Dog Leg' Works
/',J' I Channel \ ;r-r-~ i'--/' \ ~
----
0
0 + 0
<0
-
0
0 +
0 ,._
f.---
0
0 + ill
f..---
0
0 + 0
"'
.12"
0 + 0
0
---
0 +
0
-
0 + 0
N
:--
0 + 0
"'
f.---
0 + 0 ...
~
0 + 0
"'
STA
ELE
-~~V"
K 195+ ;:~------88
0 0 + +
0 0 <0 ,._
/
10.10
0 +
0
"'
I l_j
0 + 0
"'
0 + ~
Flcure 30. Glacier Fork run-of-river tunnel and penstock profile with existlnc cround based on the USGS NED shown.
Flow through the tunnel would transition into a 1,000-foot-long by 10-foot-diameter steel penstock
leading to the powerhouse located at an elevation of 290 feet msl. The downstream end of the tunnel
would include an enlarged section of tunnel that would function as a rock and debris trap.
Based on the initial review of the area geology and site visit, the rock quality for tunnel construction is
likely within the range of poor to good quality. The surface of rock exposures at Glacier Fork suggest
very closely spaced planes of weakness that correlate to very low rock quality values. This, however,
could be a surface condition caused by weathering and frost wedging. The rock may be better at depth,
so bracketing the range of tunneling conditions is appropriate. It was assumed that a tunnel would
require both initial support and a concrete tunnel lining for final support. Given the length of the tunnel,
a tunnel boring machine would likely be used to excavate this power tunnel.
Flow through the steel penstock would be divided either through a set of series bifurcations or through
a single manifold branching into five separate penstocks. Five 17-Megawatt impulse turbines would be
located within an approximately 17,500-square-foot powerhouse situated on bedrock. Water would
flow through turbines and exit through a 700-foot-long excavated tail race channel. Turbine selection
would be based both on efficiency and ease of maintenance as it would be expected that turbine
runners would require periodic maintenance.
In addition to the hydropower project features, a 35,000-foot-long all season access road through
mountainous terrain would be required to reach the intake control works. A second project building
with attached workshop would be required at the intake works for maintenance personnel and
equipment.
Page I 40
Dewatering during construction would be accomplished by constructing a bypass channel through the
footprint of the de-sanding basin. A temporary diversion dam would allow the dewatering of the
control works reach. The bypass channel would be subsequently backfilled after the control works
structure is complete. The river would be routed through the control works while the de-sanding basin
was being constructed.
6.3.2. Project Specific Power Production Estimates
A power production estimate was developed with the extended flow record for Upper Glacier Fork using
flow duration curve method for this alternative. The extended Upper Glacier Fork record was developed
using flows at the USGS gage. This alternative includes a slightly smaller drainage area (-2%), however,
no adjustment was made to the extended flow record for this alternative. Elevations are based on the
best available USGS digital elevation data with limited field checks with a handheld mapping grade GPS.
The following modeling assumptions were made in these calculations:
• The project operates in a run-of-river mode throughout the year.
• Tail water elevation is assumed to be constant.
• Environmental flow releases are assumed to be zero.
• A constant turbine efficiency of 87 percent and generator efficiency of 98 percent is
assumed.
• Preliminary turbine sizing based on the 20 percent exceedance point on the exceedance
duration curve.
• Energy losses of 10 percent are estimated due to transformer losses and plant outages
required for regular flushing of the de-sanding basin.
Gross Head (ft) 710
Net Head @ Max Flow (ft) 618
Maximum Plant Flow (cfs) 1,916
Number of Units 5-lmpulse
Nameplate Capacity (MW) 85
Head Water Elevation (feet) 1,000
The estimated average annual energy production for this alternative is 272,000 MWh with an estimated
plant factor of 36 percent. The monthly distribution of power generation is shown in Figure 31. The
project would operate near the nameplate capacity for June, July, and August with significant spillage
during these months. During the winter months all flow could be utilized for limited power production.
Winter power production represents approximately 8 percent of the annual energy production.
Considering the relatively small amount of power produced in the winter months, it may be more cost
effective to idle the plant during these periods.
Page I 41
70000
60000
:c l 50000
~ 40000 cu c
"" > 30000
:E
OJ
~ 20000
10000 +-~~~-~~~-~~~~-
0
Ficure 31. Run-of-river distribution of monthly power ceneratlon.
To examine the sensitivity of this project to uncertainty in the project inflow, the extended flow record
was scaled by 75 percent and 125 percent. This results in power generation estimates ranging from
237,000 MWh (-13%) to 296,000 MWh (+9 %), respectively. Due to the low plant factor and significant
spillage during the summer months a 25 percent reduction in annual inflow would only result in a 13
percent reduction in average annual power generation.
6.3.3. Site specific concerns and risks
Considering the magnitude of estimated annual sediment yield, the main site specific concern for this
reconnaissance alternative is sediment management. The de-sanding basin would need to effectively
limit the size of sediment that enters the penstock and turbine machinery. The intake works must be
able to effectively pass both the suspended and bedload sediment past the intake works.
Suspended sediment sampling over several seasons would increase confidence in the successful design
of the de-sanding basing. Even with a properly operating de-sanding scheme at the intake works, there
would be erosion of equipment that would require heavy maintenance more frequently than is typical
for hydropower projects.
Reducing the risk associated with bedload material would, however, be more difficult during the design
phase. Even after completion of comprehensive sedimentation studies, the best estimate of bedload
material transported by Glacier Fork would likely be tied to the suspended sediment estimates with a
large margin of uncertainty. Management of bedload material would be through effective operation of
the intake works. Hydropower generation would be reduced or eliminated at times during flushing
operations.
Page I 42
Due to the significant amount of material transported as bedload, there would be significant wear of all
exposed surfaces at the upstream weir and control works. It is expected that exposed steel rails and
concrete would require periodic heavy maintenance to replace worn sections.
6.3.4. Project Costs
A rough order of magnitude cost estimate was prepared for this alternative and is detailed in Appendix
D and summarize in the table below. The bottom line cost for this alternative is $784 million. This
bottom line cost includes all project features shown in Table 8. Costs for land and land rights were not
included.
The following assumptions were used to develop the cost estimate:
• 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 either percentages or lump sum amounts.
• Owner's administration and overhead are not included.
Table 8. Glacier Fork Run of River ROM cost summary
Structures and Improvements
Reservoir, Dams and Waterways
Waterwheels, Turbines and Generators
Accessory Electrical/Mechanical Equipment
Roads and Bridges
Transmission Plant
Contingency
Engineering ,Environmental ,Regulatory
Construction Management
Administrative & Gen. Expenses
Interest Durin9 Construction
Subtotal
Subtotal
Subtotal
Total Project Cost
30%
3.0%
1.0%
2.5%
$
$
$
$
$
$
$
$
$
$
$
$
$
$
$
8,300,000
272,700,000
46,000,000
5,400,000
135,000,000
36,700,000
504,100,000
151,3001000
665,400,000
19,700,000
6,600,000
13,2001000
694,900,000
89,000,000
78319001000
Page I 43
7. Glacier Fork Access
7.1. Road Design Criteria
Using AASHTO's Guidelines for Geometric Design of Very Low-Volume Local Roads (ADT :s; 400), the
access road to Glacier Fork would be classified as a rural industrial/commercial access road. The design
traffic volume would be 100 vehicles per day or less, with a design speed of 30 mph. A road grade of 6
percent or less is recommended for roads with low-speed vehicle operation. The dimensions used for a
two-lane are shown in Table 9 below.
Table 9. Access Road Dimensions
Roadway Surface Unpaved
Roadway Width (including Shoulders) 24 feet
Bridge Width 27feet
Minimum Embankment Height 4 feet
Road Side Slopes 3:1
Geotextile Separation
The typical section for this project would consist of a two-lane road with a minimum width of 24 feet
(Figure 32). Side slopes would be 3 feet horizontal to 1 foot vertical for embankment stability and driver
safety. The embankment cross section is expected to vary based on foundation conditions. The typical
section within areas with a good foundation would consist of 4 feet of select type A material (AKDOT)
and a 12-inch crushed aggregate driving surface. Areas with poor foundation material would require a
separation Geotextile beneath the roadway section and additional layer of unclassified fill (select type C)
with a minimum thickness of 3 feet.
150' Right otway
I
12' 12' I
, .. y>---------'-,F~~
,_
Access Road ·-..... Seperat1on Geotext1le
Fi1ure 32. Typical Access Road Cross Section
Due to the braided nature of the Knik River, it is estimated that a significant portion of the access road
alignment would require erosion protection. This could be accomplished by placing a riprap erosion
protection revetment along the river bank in these locations or by constructing a system of spur dikes
that would redirect the Knik River channel away from the north banks of the river.
7.2. Preliminary Alignment Options
Several preliminary alignment options are shown in Figure 33 for access to a project at Glacier Fork.
Access alternatives are described in Table 10. Alignment option 1 would be the shortest but would
require a significant bridge across the Knik River and a causeway across the remainder of the Knik River
Page I 44
braided plain. Due to the unpredictable nature of this braided river, proximity to the Knik Glacier, and
costs associated with a large bridge, an alternative that provides access from the south side of the Knik
River is not preferred.
Two options are shown on the north side of the Knik River. Option 28 traverses around the north side of
the Jim and Swan lakes wetland complex. The second traverses a slightly higher terrace between the
river and wetlands complex shown in option2A. This follows the alignment of the existing RS 2477 right-
of-way and existing unimproved trail network. This option would likely require erosion protection in the
form of a riprap revetment.
Site Access
-1
-2A
28
Alternative
1
2A
28
Fleur• 33: Road Access Alternatives for Glacier Fork
Table 10. Access Alternatives
Length Bridge length Erosion Protection (Miles) (ft)
12.0 1-500' Revetment (SO% of length) 1-200'
1-150'
17.6 1-50' Revetment (80% of length)
1-100'
17.4 1-150' Revetment (400A, of length)
N
W-<1-E
Minor
Crossings
(Drainage Area
<4 Sq. Mi.)
10
13
18
Page I 45
Access alternative 2A was selected to develop rough order of magnitude costs for this reconnaissance
study. The power transmission line would likely follow the proposed access route to minimize costs.
Preliminary transmission line options corresponding to each access alternative are described in
Appendix C.
8. Environmental
8.1. Environmental Considerations
Salmon are anadromous, which means they migrate from saltwater to spawn in fresh water. Glacier
Fork Creek and Metal Creek are not listed in the Alaska Department of Fish and Game's Anadromous
Catalog. While the catalog does not include every anadromous stream in Alaska, the Knik River area is
well mapped, and it is simply likely that neither creek is anadromous. The characteristics of both creeks
make it unlikely that there is any use by fish at all. Both creeks are very fast moving, subject to wide
fluctuation in flows, sediment laden, and do not provide any off channel habitat for rearing. As they are
glacially fed and sediment laden, there is limited opportunity for invertebrate production and foraging
opportunities. As with any run-of-river hydropower project, the effects of changes in flow regime along
the bypass reach would need to be considered in detail. While these issues need to be properly
considered, it seems unlikely that they would be a major impediment during the permitting process
given the small scale of the project and the nature of the bypass reach habitat.
Fish common in the Knik River area include sockeye salmon (red), coho salmon (silver), and chum
salmon, though none of these fish are known to use Glacier Fork or Metal Creek at any life stage.
Resident species such as Dolly Varden and the slimy sculpin are also found throughout the Knik Valley.
The area is home to a wide variety of animals including big game, small game, and furbearers. Big game
animals found in the area include moose, black bear, brown bear, Dall sheep, and mountain goat. Some
examples of small game animals found in the area include hare, porcupine, shrew, and vole. Common
furbearing animals of the area include beaver, coyote, lynx, marmot, marten, mink, muskrat, red fox,
river otter, weasel, wolf, and wolverine. Some of the more recognized birds seen in the Public Use Area
(PUA) include trumpeter swans, ducks, eagles, ravens, owls, and a variety of raptors.
The Knik River area is home to a wide variety of different habitat types including glaciers, ice fields,
braided river channels, exposed shores, high elevation mountains, alpine and sub-alpine tundra, boreal
forests, creeks and floodplains, and a sprawling lake and wetland complex. Each of these habit types
help to influence the area's rich and diverse fish and wildlife populations.
Given the popularity of the Knik River PUA and the quality and diversity of habitat along potential road
alignments, access to the dam site might prove to be more of a challenge than the hydropower project
itself. A road already exists along the majority of the south side of the Knik River, but a bridge would be
necessary to reach the hydropower project site. This route might minimize the potential impacts to
habitat compared with other access scenarios, but the cost of a long bridge in the upper Knik River
Page I 46
region might be prohibitive. Along the north side of the Knik River, access is currently limited to an off-
road vehicle corridor that runs along the Knik River and through the wooded area along the bank. Access
along the north shore might be the most direct route. A road along the north shore of the Knik River
would likely be used by off-road vehicles and might increase overall traffic to the region and pressure on
fish and wildlife resources, while possibly decreasing habitat damage to the existing network of primitive
trails. Access is also possible along the base of the mountains on the north side of the Knik River valley.
The route along the mountains would keep the road away from the Knik River, but would place a road in
undeveloped land and increase the network of off-road trails through forested and wetland habitat.
Improved access to the Knik River PUA could have potential impacts to the area wildlife as a result of the
improved hunting access.
The most popular fishery in the PUA is Jim Creek. Large runs of silver salmon migrate up Jim Creek to
reach the streams of the lakes and wetlands complex. These lakes include Mud Lake, Jim Lake, Gull Lake,
Swan Lake, Leaf Lake, and Chain Lakes. The expansive lakes and wetlands provide ideal habitat for the
rearing of anadromous fish, but would not be directly impacted by a hydropower project at Glacier Fork
or Metal creeks.
8.2. Environmental Requirements
Public involvement would be a key component of the environmental permit process for a hydropower
project in the Knik River area given the importance of the area for a wide variety of recreational uses
and the value of fish and wildlife habitat. This would likely be accomplished through an environmental
impact statement. The following environmental requirements would also need to be met.
• Corps of Engineers (COE) Section 404 permit for wetland fill would be required for an access
road and all facilities that require discharge of fill material into waters or wetlands of the United
States
o Section 404 permit actions are subject to NEPA; therefore, the COE would issue a
Record of Decision in conjunction with the final permit action
• U.S. Environmental Protection Agency has review authority of the COE 404 permit decisions
• U.S. Fish and Wildlife Service Section 7 Endangered Species Act consultation regarding
threatened or endangered species that may be affected by this project
• Alaska Department of Fish and Game Fish Habitat permits (Title 16 Permit) would be required
for the stream crossings on the access road and for the dam and related infrastructure
• Alaska Department of Environmental Conservations Certificate of Reasonable Assurance for 401
permits and approval of a Storm Water Pollution Prevention Plan would be required for water
quality
• Alaska Department of Natural Resources Land Use permit or Upland Lease would be required
for the hydropower facilities and right-of-way authorization for the access road and power
transmission line
• Alaska Department of Natural Resources water right would be required for legal use of Glacier
Fork surface waters.
Page I 47
• Alaska Department of Natural Resources Certificate of Approval to Construct and a Certificate of
Approval to Operate a dam would be required for any dam that impounds 50 acre-feet of water
and is at least 10 feet high
• Alaska Department of Natural Resources in-stream flow certificate would be required for
specific downstream flow release requirements
• Clearance from the State Historic Preservation Officer would be required to ensure the project
will not significantly impact cultural and archaeological resources
• Authorization would be required to develop an access road and transmission lines across
Eklutna Incorporated selected lands
8.3. FERC Status/Jurisdiction
The Federal Energy Commission has jurisdiction over hydropower projects that meet any of the
following conditions:
• Is located on a navigable waterway
• Occupies lands of the United States
• Uses surplus water from a federal dam
• Is located on a Commerce Clause waterway/ post -1935 construction, and affects
interstate or foreign commerce
A hydropower project on Glacier Fork does not appear to meet any of the conditions listed above that
would establish FERC jurisdiction over the project. There is one exception that may apply to any project
located along Glacier Fork. Road access up the Knik Valley would require crossing lands of the United
States1 as described in the Land Ownership section of this report. The access alternatives cross Federal
lands managed by the Bureau of Land management. However, these parcels are in the process of
conveyance to the Eklutna Native Corporation and will become non-Federal lands in the future.
9. Land Ownership
A limited search of public land, private holdings/ and State/Federal mining claims was performed for the
Knik Valley. The results of this research are shown on Figure 34. Generally, all lands within the vicinity of
Glacier Fork and the reconnaissance alternatives identified are State lands with the exception of three
private parcels along lower Glacier Fork. This area is a historic mining area with numerous State mining
claims still in existence along lower Glacier Fork and Metal Creek. A State designated RS 2477 right-of-
way has been established along the historic Knik Glacier Trail.
The proposed hydropower access alternatives (shown) would cross a mixture of State and Federal land
(administered by the Bureau of Land Management). All Federal lands crossed by the access alternatives
have been selected by Eklutna Incorporated for conveyance under Alaska Native Indigenous Lands Claim
Act (ANILCA). The process to convey these lands is underway, and at some point in the future, these
Page I 48
lands will become property of Eklutna Inc. In addition to the ownerships identified, the entire area lies
within the Knik River Public Use Area (KRPUA).
Privotely Owned -BLM
BLM -Notove Selected
-Interim Conveyed
No!NePatentad
State Unci Oospoool -Municipal
State lllnd 0~1 -Cllhe< thon Minicipool
StatePatentad
State Tent.tivety Approved
Stole ond Notove Owned
D State Moning Claima
0 PRIVATE
-RS2•n Right of Woy
Fl1ure 34. General land status map with the three access alternatives shown.
s
The KRPUA was legislatively designated by the State of Alaska in 2006 and managed by the Alaska State
Department of Natural Resources. The area was established to:
• perpetuate and enhance general public recreation and public enjoyment of fish and wildlife
• protect and maintain migratory waterfowl nesting areas; habitats for moose, Dati sheep and
brown bear and other fish and wildlife habitat so that traditional public use of fish and
wildlife populations may continue
• provide an area for the public to enjoy the full spectrum of public uses, including
maintenance and enhancement of off-road motorized vehicle and non-motorized
recreational opportunities
• allow access for miners and private property owners
The various management units within the KRPUA are shown in Figure 35.
Page I 49
Knik River Public Use Area: Management Units
AS 41.23.110.Z30
Fleur• 35. Knik River Public Use Area: Manacement Units (From KRPUA Mana&ement Plan).
The management intent for the Grasshopper Valley and Metal Creek units is to manage for low levels of
public use and to enhance recreational opportunities while mitigating impacts of use on fish and wildlife
habitat and maintaining access to private lands and mining claims. The current management plan for the
KRPUA does not address hydroelectric power generation within the area. Hydropower development
would be evaluated by the Alaska Department of Natural Resources on a case by case basis to
determine the best use of this natural resource (DNR personal communication 2012).
An area of land along the south side of the Knik Valley is a designated National Natural Landmark .
Un ique to the Knik River are historic glacial lake outburst floods, which occurred from the early 1900's
through the mid 1960's. As a result of these outburst floods and through heavy lobbying efforts from
locals in the 1960's, Lake George was designated as a national natural landmark in 1967. While the
natural phenomenon that was used to establish this national natural landmark has not occurred since
1966, the area remains on the list of National Natural Landmarks. Federal agencies should cons i der the
unique properties of these nationally significant areas in completing compl iance under the National
Environmenta l Policy Act. National Natural Landmark designation is not a land withdrawal, does not
change the ownership of a site, and does not dictate use or act ivity.
Page I 50
The Alaska Lands Records Database was accessed to review the Glacier Fork area for existing water
rights. There are no existing or proposed water rights in the vicinity of Glacier Fork.
10. Economic Analysis
We have taken a life-cycle cost approach to determining potential economic feasibility of Glacier Fork
hydropower generation. Life cycle costs are the sum of all recurring and one-time (non-recurring) costs
over the full life span or a specified period of a good, service, structure, or system (Table 11). These
include purchase price, installation cost, operating costs, maintenance and upgrade costs, and remaining
(residual or salvage) value at the end of ownership or its useful life. The life-cycle cost of power
generation is typically used to determine economic feasibility for hydropower projects.
The following assumptions were used to determine life-cycle costs:
• The project period of analysis (life) is SO years.
• Project costs have been discounted to 2013 dollars using the Federal Fiscal Year 2013 discount
rate of 3. 75 percent.
• Operations and maintenance (O&M) costs are estimated at 1 percent of initial construction cost.
• Heavy turbine maintenance is required every 10 years with an estimated cost of $10 million.
• Annual road maintenance for 21 miles of new construction is estimated at $26,000 per mile
based on 2008 estimates for the Dalton Highway (which have been updated to 2012 dollars
using the Anchorage Consumer Price Index).
• Power generation is estimated at 272,000 MWh annually.
• Three separate financing mechanisms of 20 percent, SO percent, and 100 percent initial
investment are analyzed. Financing options used a 6 percent interest rate and 30-year period of
repayment.
• Return on investment has not been calculated as the project goals are not yet defined.
• Costs associated with railbelt grid upgrades that may be required are not included.
Table 11. Summary of inputs to calculations.
Category
First Costs
O&M (1 percent of construction costs)
Heavy Turbine Maintenance
Road maintenance (21 miles)
I Cost I Frequency
$ 783,900,000 one-time
5,040,000 annually
10,000,000 every 10 years
546,000 annually
The production cost per kWh ranges from $0.15 to $0.18 under the three different financing options.
Finance Option 3 has no financing so cost per kWh is lowest. This financing option would be plausible if
there were returns other than monetary envisioned for the project. These returns could be job creation,
reliability of power generation, or other objectives that would benefit the railbelt utilities and its
customers. Typically, however, there would be some repayment of the initial investment with interest to
Page I 51
the lender as Finance Options 1 and 2 show, which results in higher production costs per kWh (Table
12).
Table 12-Wholesale cost per kWh -three flnancin1 options
Financing Option Initial Investment Wholesale Cost per
kWh
Financing Option 1 (20% initial investment) $ 156,780,000 $ 0.18
Financing Option 2 (SO% initial investment) $ 391,950,000 $ 0.17
Financing Option 3 (100% initial investment) $ 783,900,000 $ 0.15
In all cases, the production costs for the Glacier Fork hydropower project are well above what is typically
seen for wholesale power along the Rail belt.
11. Conclusions and Recommendations
Two aspects of the Glacier Fork drainage are attractive from a hydropower perspective: significant
elevation loss over a relatively short distance and high summer flows. Three alternatives were examined
at the conceptual level to determine whether additional study of hydropower on Glacier Fork was worth
pursuing.
Within the three concepts the first two alternatives were eliminated due primarily to reservoir
sedimentation concerns. The third alternative developed was a run-of-river project with the intake
works above the Glacier Fork canyon and the power plant below the canyon. This 85 MW hydroelectric
project was estimated to produce 272,000 MWh annually with a total project cost of $784 million.
Both the risks and estimated cost to develop this alternative would be high. A hydropower project
located on Glacier Fork would:
• Effectively only produce power for 4 months of the year
• Would have a high life cycle cost per kilowatt hour
• Would have several high risk issues associated with:
o Glacial dam outburst flooding from upstream areas adjacent to the Mt. Marcus
Baker Glacier or from advance of the Knik Glacier.
o Retreat of the Knik Glacier resulting in loss of the hydropower resource to the
adjacent valley.
o Sediment erosion of power generating equipment.
Further study of medium scale hydropower alternatives along Glacier Fork is not recommended at this
time.
Page I 52
References
Berthier, E., Schiefer, E., Clarke, G., Menounos, B., & Remy, F. (2010, January lOth). Contribution of
Alaskan glaciers to sea-level rise derived from satellite imagery. Nature Geoscience Letters.
Bra bets, T. P. 1993. Glacier Runoff and Sediment Transport and Deposition Eklutna Lake Basin, Alaska
(WR192-4132). Anchorage: U.S. Geological Survey.
Bradley, D.C. and Kusky, T.M. 1989 "Kinematics of Late Faults Along Turnagain Arm, Mesozoic
Accretionary Complex, South Central Alaska", Geologic Studies in Alaska by the US Geological Survey,
1989.
Bradley, D. C., & Miller, M. L. 2003. Field Guide to South-Central Alaska's Accretionary Complex,
Anchorage to Seward. Alaska Geological Society.
Bunds, M.P. 2001. "Fault Strength and Transpressional Tectonics Along the Castle Mountain Strike-Slip
Fault, Southern Alaska", Vol. 113, No.7, Bulletin ofthe Geological Society of America.
Burns, L.E.; Pessel, G. H.; Little, T.A.; Palvis, T.L.; Newberry, R.J.; Winkler, G.R.; and Decker, J. 1991.
"Geology ofthe Northern Chugach Mountains, South Central Alaska", Professional Report No. 94,
Division of Geological and Geophysical Surveys, State of Alaska.
Connelly, William. 1978. "Uyak Complex, Kodiak Islands, Alaska: A Cretaceous subduction complex", Vol.
89, No.5, Bulletin ofthe Geological Society of America, pp755-769.
Daly, C. 2009. Annual Mean Precipitation for Alaska 1971-2000. Corvallis: PRISM Climate Group at
Oregon State University.
Farrell, C. R., Heismath, A. M., Lawson, D. E., Jorgensen, L. M., Evenson, E. B., Larson, G., et al. 2009.
Quantifying periglacal erosion: insights on a glacial sediment budget, Matanuska Glacier, Alaska. Earth
Surface Processes and Landforms , 2008-2022.
Gesch, D., Oimoen, M., Neson, S., Steuck, C., & Tyler, D. 2002. The National Elevation Dataset.
Photogrammetric Engineering and Remote Sensing, 68 (1), 5-11.
Goodman, R.E, 1989. "Introduction to Rock Mechanics", 2nd ed., John Wiley & Sons, New York.
Hack, R. C. 1954. Proposed Knik Glacier-Lake George Power Project (With Flood Control Benefits).
Portland.
Haeussler, P.J.; Bruhn, R.L.; and Pratt, T.L. 2000. "Potential Seismic Hazards and Tectonics of the Upper
Cook Inlet Basin, Alaska Based on Analysis of Pliocene and Younger Deformation", Vol. 112, No.9,
Bulletin ofthe Geological Society of America.
Kaushish, S. P., & Naidu, B. K. 2002. Proceedings of the 2nd International Conference on Silting Problems
in Hydropower Plants.
Page I 53
Kusky, T.M.; Bradley, D.C.; and Haeussler, P. 1997. "Progressive Deformation of the Chugach
Accretionary Complex, Alaska, During a Paleogene Ridge-Trench Encounter", Vol. 19, No. 2, pp 139-
157, Journal of Structural Geology, Elsevier, GB.
Lawson, D. E. 1993. Glaciohydrologic and Glaciohydraulic Effects on Runoff and Sediment Yield in
Glacerized Basins, Monograph 93-1. USACE Cold Regions Research & Engineering Laboratory.
Lawson, D. 2012. Personal Communication.
McGee, D.L., "Evacuation of Unnamed Glacial Lake Contributed to 1971 Matanuska Valley Flood", Vol.
23, No.5, Mines Bulletin, Division of Geological Survey, Department of Natural Resources, College, AK.
O'neel, S. 2012. Personal Communcation. United Geological Survey.
Parks, B., & Madison, R. J. 1984. Estimation of Selected Flow and Water-Quality Characteristics of
Alaskan Streams (WRI 84-4247). USGS.
Post, A., & Mayo, L. R. 1971. Glacier Dammed Lakes and Outburst Floods in Alaska, Hyd lnv. Atlas HA-
455. U.S. Geological Survey.
Trabant, D. C., & Mayo, L. R. 1985. Estimation and effects of internal accumulation of five glaciers in
Alaska. Annals of Glaciology, 6, 1130117.
U.S. Department of Agriculture, N. R. 2004. MATANUSKA RIVER EROSION ASSESSMENT.
U.S. Geological Survey. 1985 (rev). "Anchorage, Alaska 1:250,000 Topographic Quadrangle", Alaska
Topographic and Bathymetric Series
Willis, I. 2005. Hydrology of Glacierized Basins. In M. G. Anderson (Ed.), Encyclopedia of Hydrological
Sciences (pp. 2601-2631). Chichester: Wiley.
Winkler, G.R. 1992 "Geologic Map and Summary Geochronology of the Anchorage 1 oX 3° Quadrangle,
Southern Alaska, 1:250,000", Map 1-2283, Misc. Investigation Series, U.S. Geological Survey.
Yehle, L.A. and Schmoll, H.R. 1988 "Surficial Geology of the Anchorage B-7 SE Quadrangle, Alaska",
Open-File Report 88-381, U.S. Geological Survey, Denver, CO.
Page I 54
Appendix A: Utilization of the National Elevation Dataset.
In order to determine if the National Elevation Dataset (NED) was adequate for defining
reservoir storage parameters for the Glacier Fork canyon, an area with similar canyon
topography was used to compare elevation storage curves developed from both the NED and a
much more accurate LiDAR dataset. The Eklutna River, located approximately 27 miles
southeast of Glacier Fork, was used for the comparison. The river flows through a deep, steep-
walled canyon in this area similar to Glacier Fork and Metal Creek. Figure A. I shows the canyon
area of Eklutna River. The red polygon shows the limits of the elevation versus storage
calculations using both the NED (as shown in the topographic mapping) and the visible LiDAR
dataset.
t
\
,.. -
Figure A.l: Elevation-storage polygon over Eklutna canyon.
The two independently derived storage elevation curves for the area within the polygon are
shown in Figure A.2. These results indicate that the USGS NED dataset is suitable for
preliminary estimates of storage volume versus elevation for areas that include steep-walled
canyons. As would be expected at the lower elevations, analysis using the LiDAR dataset results
in more storage; however, as the area and storage volume increases with elevation the
differences between the much coarser USGS NED dataset and LiDAR data diminish. The
LiDAR dataset contains higher resolution topography within the base of the canyon resulting in
more storage at lower elevations.
700
600
;:::-500
.!:!:.
c 400
0
~ 300 --NED (1 Arc Sec)
> Cll 200 iOj --liDAR
100
0
0 10000 20000 30000 40000 50000 60000
Storace (AC-FT)
Figure A.2: Comparison of storage versus elevation curves developed from the USGS NED and LiDAR data sets.
Appendix 8: Additional Geologic Information
8.1 Source of Sedimentary Rocks
Ocean floor sediments along the subduction trench slid down the trench slope as turbidity
currents that resulted in deposits of clay, sand, and gravel. These sediment types were lithified
over time into argillite, greywacke, and pebble conglomerate, respectively, that were later
metamorphosed into other rock types (Bradley and Miller, 2003; Bums et al, 1991; and Kusky et
al, 1997).
8.2. Regional Rock Types
The Chugach Mountains are composed primarily of rocks of the McHugh Complex and the
Valdez Group. The majority of the range is formed from the Valdez Group. The Valdez Group
is an assemblage of Cretaceous age, low-grade metamorphic rocks including phyllite and schist
with minor occurrences of slate and igneous dikes (Bradley and Miller, 2003; Burns et al, 1991;
and Kusky et al, 1997) that have been folded and faulted to varying degrees. The Glacier Fork
site is situated within the Valdez Group.
8.3 Regional Faulting
The active tectonic history of Southcentral Alaska has resulted in development of a number of
major faults (Kusky et al, 1997). Six large faults are shown on the USGS geologic map of the
Anchorage 1 o x 3 o Quadrangle (Winkler, 1992). These are the Castle Mountain Fault, the
Caribou Fault (a splay from the Castle Mountain Fault), the Border Ranges Fault Zone, the Eagle
River Fault, the Placer River Fault, and the Contact Fault.
T A L K E E T N A
Figure 8.1.1 Map showing major faults and geologic terrains (Winkler, 1992)
All of these faults are of the strike-slip type except the Eagle River Fault, which is a thrust fault
(Bradley and Miller, 2003 ; Burns et al , 1991 ; and Kusky et al, 1997). In addition to the large
faults indicated above, there are numerous smaller faults mapped in the Border Ranges Fault
Zone, a much disrupted zone between the Castle Mountain Fault and the Eagle River Fault
(Burns et al , 1991 ; and Kusky et al, 1997). Innumerable small faults are present in the Chugach
Mountains and, due to the complex geologic history of the area and the remoteness of the
mountains , other faults may be present that have not yet been detected.
8.4. Regional Structures
The dominant regional geologic structures are faults, although anticlinal and synclinal folds are
shown on geologic maps (Burns et al, 1991 ; and Winkler, 1992). Mapped features indicate two
large structural trends . The dominant structural trend appears to arc north and east from the
Anchorage area. The Castle Mountain Fault, Border Ranges Fault Zone, and Eagle River Fault
trend north-northeast, gradually arcing eastward until the trend is east-west near Chickaloon. The
Knik Arm and the Matanuska Valley follow this trend and are likely controlled by faulting. The
less dominant trend is a series of parallel features that may affect conditions in the vicinity of
Glacier Fork. The southwest portion of Border Ranges Fault, Placer River Fault, Metal Creek
Valley, a series of anticlines and synclines in the Glacier Fork River-Metal Creek-Knik Glacier
area, and College Fiord are all parallel linear features that trend north-northeast to south-
southwest and appear to share some structural relationship. Examination of aerial photography
and topographic maps also indicates a distinct lineament along the Placer River Fault trending
north-northeast through the Metal Creek valley that suggests a potential structural relationship
between the two features . The USGS geologic map ofthe Anchorage 1° x 3° Quadrangle
(Winkler, 1992) shows an anticlinal structure superimposed on the Metal Creek valley . Further
research may be necessary to determine precise structural relationships and effect, if any, near
Glacier Fork.
'· •
Figure8.2. Geologic map of the region surrounding Glacier Fork. Major faults and geologic features are identified.
Modified from Winkler, 1992.
The US Geological Survey earthquake hazard website (http://earthquake.usgs.gov/hazards/)
provides deaggregation of seismic hazards displayed on the 2007 and 1998 USGS National
Seismic Hazard Mapping Project (NSHMP) of Alaska as well as the probabilities of earthquakes
of given magnitudes to occur. Research by Haeussler et al (2000) indicates a magnitude 6.0 to
greater than magnitude 7.0 earthquake may be possible in the region.
B.S. Site Geomorphology
The geomorphologic features evident in the Glacier Fork area are dominated by glaciation and
geologic structure. As mentioned previously, the Knik Glacier is the largest glacier in the area
and is responsible for the modification of the Knik Valley. The Knik Valley is a broad U-shaped
glaciated valley partially filled with sediments to form an outwash plain. The Knik River flows
westward from the Knik Glacier. The river is overloaded with sediment causing its flow to vary
from anastomosing to simple braided stream flow farther downstream. Glacier Fork of the Knik
River flows from Grasshopper Valley west-northwestward through a gorge incised between the
mountains to the north and a highland area to the south referred to in this report as the Glacier
Fork Highlands. The Knik Glacier has formed a number of other features identified on the
geomorphologic map shown in Figure. Rock foliation, jointing, folding, and possible faulting
have also been factors in development ofthe existing terrain.
Glacier Fork of the Knik River flows as a braided stream from Grasshopper Valley east of the
site toward the west-northwest, adjacent to the Knik Glacier lateral moraine and across glacio-
fluvial sediments. Glacier Fork has encroached into the lateral moraine between Grasshopper
Valley and the upstream end of Glacier Fork Gorge and is very close to the ice at this location.
At a rock outcrop near the upstream end of the proposed reservoir, a nick point has formed where
the stream plunges into a gorge incised into rock. From this point downstream to the mouth of
Glacier Fork, stream flow is confined to a single rock channel. Glacier Fork lies in an unusual
position between the mountains and a highland area adjacent to the Knik Glacier. The glacier
may have over-ridden this highland during the Pleistocene and forced melt water into or along
weaknesses in the rock formed by joints or faults. A steep narrow gorge was formed by erosion
of rock material along lithologic discontinuities, presumably from large melt water discharges
during the recession ofKnik Glacier. The specific discontinuity types associated with the
formation of the gorge are not known at this time but likely include joints, foliation, and possibly
fault segments. Relatively straight segments of the gorge align with local joint and foliation
orientations. There is another feature eroded into rock that appears to be controlled by joints or
other geologic structures. A linear, dog-leg shaped channel has been eroded into rock near the
upstream nick point on Glacier Fork. It extends from the Knik Glacier lateral moraine and
deepens as it approaches Glacier Fork. It appears on the map as two linear segments, one that
trends N30°E and the other Nl4°W.
Glacier Fork Gorge (B.3) is a narrow, steep-walled valley incised into Valdez Group
metamorphic rock with near-vertical walls along much of its length. The gorge appears to be
controlled to some extent by rock joint or fracture sets, although faults cannot be ruled out at this
time. The river has formed entrenched meanders along the length of the gorge. Along much of
the gorge length the valley walls are too steep to support vegetation and surficial mass wasting
processes move loose rock material down slope. There are three major nick points, which are
shown on the map (Figure B.4) as the upstream, middle and downstream nick points. Two views
of the upstream nick point are also shown on Figure B.S.
CIMG1081 .JPG
Figure 8.3. Gl•cier Fork Gorge our tbe upstrum end (left), vertic•l w•Us of tbe Gl•cler Fork Gorge.
US ArmY Corps of Engineers
Alasl<a District 2012
RECONNAISSANCE
GEOMORPHOLOGIC MAP
GLACIER FORK OF
THE KNIK RIVER AREA
AreaS ol G\ooe! FOO. QOI99 outlined
in b4ue a~e steep bare rod\ slopeS
CIMG1055.JPG
Figure B.5. Two views of tbe upstream nick point where Glacier Fork enters tbe gorge.
The Glacier Fork Highlands is a term used in this report as a convenient means to refer to the
highland area between Glacier Fork and the Knik Glacier. It is not a formally named feature.
The terrain of the highland area is rolling to steep hills with dense vegetation and sparse rock
outcrops. The USGS geologic map of the 1° x 3° Anchorage Quadrangle indicates the area of
the Glacier Fork Highlands as Quaternary surficial deposits (Qs) of glacial moraine and outwash
sediments . Low altitude aerial and ground examination prove that the highlands are entirely
Valdez Group metamorphic rock.
The Knik Glacier bounds the Glacier Fork Highlands on the south. It terminates a short distance
from the mouth of Glacier Fork. Distinct end and lateral moraines are present. The current end
moraine is likely a recessional moraine rather than a terminal moraine . Melt water is ponded
behind the end moraine and there is a wedge-shaped area between the end moraine, outwash
plain, and Glacier Fork Highland that is sparsely vegetated.
Metal Creek flows southward through an unusually linear V -shaped valley (Figure 8.6) that
converges with Glacier Fork a short distance upstream ofthe mouth of Glacier Fork (please refer
to Figure , Regional Topographic Features Surrounding Glacier Fork shown in the Regional
Geology section of this report). The valley appears to be structurally controlled and aligns with
the Placer River Fault to the south. A structural lineament can be inferred from the orientation
and alignment of the Placer River Fault, along the east edge of Mount Palmer, and through Metal
Creek. The geomorphologic map shows the inferred structural relationship as the Placer River
Fault lineament.
C IMG1031.JPG
Figure B.6. V Shaped linear valley of Metal Creek.
Grasshopper Valley is a relatively small glaciated valley northeast of the Glacier Fork Highlands
that appears to be the primary source for Glacier Fork.
The USGS geologic map (Winkler, 1992) indicates a series of folds in the immediate vicinity of
Glacier Fork. Two anticlines and one syncline are shown on the map with parallel north-
northeast trends. The aerial photograph base for the geomorphologic map suggests additional
linear trends that may be attributable to bedrock joint sets.
8.6. SITE GEOLOGY
8.6.1 Soil
The soil examined in the vicinity of Glacier Fork can be divided into glacio-fluvial sediments,
residual soils , and colluvial soils . Only the glacio-fluvial sediments in the Knik River valley
appear to have significant thickness. The residual and colluvial soils appear in most places to
form a relatively thin mantle a few feet thick over rock formations. The glacio-fluvial soils occur
in vast accumulations in the Knik valley and in small deposits in and along Glacier Fork that are
composed of varying gradations of sand, gravel, cobbles, and occasional small boulders
produced from Knik Glacier and transported a short distance by flowing water. The residual soils
consist of various combinations of silt, sand, and gravel fragments of partially decomposed rock
with locally abundant organic material that developed from the in-place weathering of rock with
little or no transport. The clay-size fraction of soils is anticipated to be negligible. The colluvial
soils form during normal slope forming and mass wasting processes where soil and weathered
rock move down slope due to gravity. Although flowing water is not a factor in transporting
colluvial sediments, ice formation within the soil can influence colluvial soil movement. The
colluvial soils were not accessible for close examination but appear to be composed of sand to
boulder-sized particles derived from weathered rock and rock falls on steep slopes.
8.6.2 Rock Types -Stratigraphy & Lithology
The Valdez Group (Kvs) is composed of Cretaceous low-grade metamorphic rocks. They were
predominantly derived from the metamorphosis of greywacke (dirty sandstone) and argillite
(claystone) (Bradley and Miller, 2003; and Burns et al, 1991; and Kusky et al, 1997). Phyllite
and schist (Figure B.7) are the dominant rock types exposed in the Glacier Fork area. The schist
in some areas appears to grade nearly to gneiss where mineral segregation has concentrated
quartz into layers. Igneous dikes (Figure B.8) were observed in the walls of the Glacier Fork
gorge but were not accessible for close examination. Felsic sills and dikes are reported in the
literature to be common in the Valdez Group but account for only a small percentage of the rock
and are generally less than 10 feet thick (Bums et al, 1991). The dikes observed at Glacier Fork
appeared to be 1 to 2 feet thick. Slate was observed in minor amounts near the mouth and near
the upstream end of Glacier Fork and a very minor occurrence of quartzite was observed at the
upper end of Glacier Fork. The rock exposed in the walls and on the slopes above Glacier Fork
were only slightly weathered and generally appeared to be sound. Rock weathering was more
pronounced on the upper slopes. The rock examined was moderately hard, meaning it could be
scratched with a knife. Heavy blows with a geologist pick generally produced a dent in the rock
less than 3/16-inch deep. Several blows with a geologist hammer were required to break hand
specimens for examination. Of the fresh rock specimens examined, phyllite was the easiest to
scratch, dent, and break. Slate was more resistant to scratch and dent tests than the phyllite but
less resistant than the schist. Some of the schist was very difficult to break into hand specimens.
CIMG1021 .JPG
N 61' 26' 36"
I ........ ~.~~
N 61' 26' 15"
CIMG1025JPG
,
Figure B.7. Example of phyllite on left and schist on right .
• \~ ..... '1,_
W 148• 2T 49"
N 6 1• 2 5' 14"
8.6.3 Structure
Figure B.S. Examples of possible igneous dikes.
14
f ..
The pertinent geologic structural features at the Glacier Fork site include foliation , joints, faults ,
and folds (Figure B.9). Foliation is the apparent layering in the rock due to mineral reorientation
developed during metamorphosis that may or may not be parallel to the bedding of the original
sedimentary rock. The joints are more or less linear lithologic discontinuities in the rock that
have experienced little or no movement along their length and generally occur in intersecting sets
of two or more. Faults, on the other hand , are discontinuities that have moved along their length
due to tectonic forces. Folds are generally large scale bends in the rock. Anticlines are convex
upward bends and synclines are convex downward bends of the rock caused by tectonic forces .
' j
KNIKVALLEY
METAt~EEK /
-Kvs "'-.. ;~
TQs ~ ..
' .PLA.'Cfi~ RIVER / F~L ·-1
: ~~, E ~~ .. / g /(,~' . .:./ ~
,I
KN IK GLACIER
K
II
I ,
'I 10 i
Figure 8.9. Detail of geologic map of Glacier Fork area. Note the inferred Placer River Fault Lineament was not shown
on the USGS map. The areas outlined in red at the Glacier Fork Highlands were found to be Valdez Group (Kvs) rock
rather than Quaternary surficial deposits (Qs). Modified from Winkler, 1992.
8.6.4 Foliation/Bedding
The foliation observed at the site often resembled relict bedding; however, in some outcrops,
foliation completely obscured the original bedding. Foliation and joint orientations were
measured at available outcrops in three general locations: the right abutment area of alternative
2, the mouth of Glacier Fork gorge, and an outcrop near the upstream end of the Glacier Fork
gorge. The number of measurement points proved to be inadequate to determine foliation trends
for the length of the site but does provide some indication of the potential range of orientations
that might be expected. The orientations varied widely between northwest and northeast
directions with inclinations between 22° and vertical. The spacing of foliation separations also
ranged widely from less than one inch to approximately one foot (Figure B.lO). The texture of
rock surfaces along the foliation varied primarily as a result of the constituent mineral crystal
stze.
CIMG 1 026 .JPG
Figure B.lO. Example offoUation.
8.6.5 Jointing and Fractures
There were two and often three intersecting joint sets at the locations where joint sets were
measured or observed. In addition to the joint sets, random fractures were sometimes evident.
The intersecting joint sets separate the rockmass into varying sized and shaped blocks. The
number of joint measurement points was inadequate to develop meaningful trends but does
provide an indication ofthe range of joint orientations that may be present at the site. Where the
primary or most prominent joint set was measured, the joints were oriented northwest to west-
northwest, inclined 47° to vertical. Primary joint spacing varied from as little as I inch to greater
than 4 feet. The secondary joint set was oriented between northeast and southeast and inclined
between 22° and 80° most often dipping to the northeast. Joint sets on larger scales are evident
in the walls ofthe gorge where large angular blocks are formed by more widely spaced joint sets.
The observed aperture of the joints appeared to vary widely, with some tightly closed and others
on weathered outcrops open more than an inch (Figures B. II and B.l2}.
CIMG1076.JPG
CIMG1012 .JPG
, 03"
N 61" 26' 20" N 61" 24' 09"
Figure 8.11. Very close joint spacing (left) and typical joint spacing (right).
CI MG0966.JPG CIMG1030.JPG
N 61" 26' 14" N 61" 26'15"
Figure 8.12. Large scale joint patterns.
B.6.6 Faults and Folds
No direct evidence of faults or folds on the scale observable from a helicopter, by examination of
rock outcrops, or from viewing rock exposures across Glacier Fork gorge was identified. The
literature describes faulting and folding in the general area, but no conclusive evidence of these
features was found during the brief site visits. There are a number of inaccessible rock
exposures observed from either the helicopter or from across the gorge that resembled rock faces
that had been sheared by movement along a fault; however, it was not possible to examine those
locations to determine the cause of their appearance. Minor deformation on the scale of a few
feet was observed in a few outcrops suggesting that folding-type deformation has occurred in the
area. There are several parallel folds indicated on the USGS geologic map that covers the
Glacier Fork area. An anticline is indicated along Metal Creek and another that runs through the
lower end of Grasshopper Valley. A syncline is indicated through the mountain peak north of
the upper end of the Glacier Fork gorge between the anticlines.
B.6. 7 Relative Rock Mass Properties
Rock mass strength is considered to be the combination of the strength characteristics of the rock
material and the resistance to movement along lithologic discontinuities such as joints and
fractures (Goodman, 1989). The rock material's response to compression and tension define the
rock strength characteristics, while surface roughness, discontinuity orientation, frequency (or
spacing), aperture, and persistence determine the strength of the discontinuity (Goodman, 1989).
Rock texture is an important factor in developing friction along a discontinuity such that friction
between rock blocks corresponds to the strength across joints and the development of rock mass
strength. Phyllite and slate foliation and joint wall surfaces are relatively smooth due to the size,
platy shape, and mineralogy of constituent mineral crystals. The schist has a very rough texture
due to the characteristics of its constituent minerals. Slope instability and the occurrence of
removable rock blocks in steep slopes are greatly controlled not only by the orientation, spacing,
and aperture of joints but also by the roughness of the wall rock along those joints. In this
instance, unweathered schist exposed in steep slopes may experience less slope instability than
similar slopes composed of either phyllite or slate.
The discontinuities are anticipated to be the controlling factor in development of rock mass
strength at the Glacier Fork site. Due to a number of intersecting discontinuity sets (foliation,
two to three joint sets, plus random fractures), the orientation, aperture, roughness, and
persistence observed at the site; the rock mass strength is anticipated to be much less than the
strength of an intact rock specimen. Care would need to be taken in the investigation and design
of facilities at this site to fully characterize the rock mass reaction to loading. The loading at any
given location may yield a favorable or adverse response from the rock mass depending on the
characteristics and orientation of the discontinuities at that location. Due to the variability
observed in the orientation, frequency, and condition of discontinuities in the area, measureable
rock mass strength variation across the site is anticipated. The removal of loose rock required for
construction and appropriate rock anchoring would likely reduce some of the rock mass strength
variability. Based on the brief reconnaissance of the site, the rock material and rock mass, if
properly prepared and treated, are anticipated to be capable of providing adequate bearing
capacity for construction of a dam, penstock, and power house.
B.6.8 Relative Permeability
The rock mass observed in Glacier Fork is anticipated to be permeable only along lithologic
discontinuities such as foliation, joints, and fractures. The rock itself has low permeability. The
discontinuities can be anticipated to be open near the surface and more tightly closed with
increasing depth and distance from valley walls. Grouting is anticipated to be effective in
controlling seepage. A grouting program should be anticipated to address dam abutments,
foundation, and penstock. Seepage from a reservoir along Glacier Fork is anticipated to be minor
relative to river inflows.
B. 7. Seismic Hazard Deaggregation
Figure B.13 below is the probabilistic seismic hazard deaggregation of data for an area with a
50-km (31-mile) radius of the Glacier Fork site. The figure graphically depicts the contribution
of potential earthquake sources to the overall site seismic hazard. The earthquake magnitude and
distance from the epicenter are on horizontal axes and the percent contribution to seismic hazard
is shown on the vertical axis. An M9 earthquake at a distance of 40 km from the site contributes
nearly 20 percent of the seismic hazard. Earthquakes with magnitudes 7.0 to 7.5 at about 40 km
distance each contribute approximately 12 percent of the seismic hazard. Earthquakes with
magnitudes from M5 to M6.5 cluster around 10 km from the site and contribute a collective 24
percent of the seismic hazard. Seismic hazards from other sources are depicted as small distant
contributors.
Figure B.14. is a geographical representation of the same seismic hazard deaggregation data
shown in Figure B.l3.
I
Prob. ~ismic H3UU'd lk~pti on
Obci~r_Fork 148.5030" W. 61.4352 N.
Pcol. Hoa1. Ground A«ee.>-11.}79} 1
Ann E><ft<lua Rm .-III-IE-DJ M•an Rnum Tun< 247} ~·n
Muntii..M.lo<J )7.7km. 7.21, Ul, 2.23
Modal ! llM.COI • 4~.3 km. 9.20, 1.4) from ptlll R.M btn
Modal tR..,M .r.•,. 4.!l ~ 9.:!0.1 to.:! •p•. fram peD. R..M.,I: b1n
Btnrur,.dl:tatls O.luR 10 . km.ddbM-0~. 0.1,....1.0
... -··
~<loiiPIMt<:....,
1 ~-a<...,Pllltc.~
Figure 8.13. Seismic hazard deaggregation for the Glacier Fork site. USGS National Earthquake Hazard Mapping
Project.
Glacier_Fo1k Gecpaphit Dew. Seilmic: Huard
for O.OO.s Spectral Acte~ 0 .57~ I!
PGA Eveodonc• Rnum Tim<: ~75 yeon
Ma:umum Scnxa' dn:tanr.x ll.2 lun. wha:c
"'"orrur IOIIltt bus'"'"' <O.OSt.conmbtaton
llrd hnn a:r pll'tmr Qaarma" flair IOCIIbens
S1R on rock. a"YCU.Jl' vt-?rtD In's tap )0 m
D2
88 83
f~ M
SB
84 eo
58
r---·-----------·----------~·--------~"'~----------·-----------·---,
•
•
. . . . . . " ..
• • B • .,.p ••
_...,. ..
. • krn
I I
I " ..
" -••
•
EE:Ii .m iJ .U•••• .. a.....-............... _... ....... , .... _......."1 .. ___ .., ..... .,.._ ..... ..
Figure 8.14. Seismic hazard deaggregation for the Glacier Fork site. The Glacier Fork site location is indicated by the
yeUow oval in the center ofthe figure. USGS National Earthquake Hazard Mapping Project.
Peak Horizontal Ground Acceleration (PHGA) or Peak Ground Acceleration (PGA) is a measure
of earthquake acceleration on the ground and an important input parameter for earthquake
engineering. It is not a measure of the total energy (magnitude, or size) of an earthquake, but
rather of how hard the earth shakes in a given geographic area (the intensity). The PHGA for the
Glacier Fork site was calculated by the USGS National Earthquake Hazard Mapping Project
website software and provided a PGA for the site at 0.5792g with a 2475 year exceedance return
time. This approximates the PGA for the maximum credible earthquake for the area.
Figures B.l5 through B.l7 depict the probability of a specified magnitude earthquake occurring
within I 00 years and within 50 km of the site. A probability range is mapped as a color that
indicates the specified magnitude earthquake probability for that shaded region . From these
figures , one can develop a better idea of the likelihood of a damaging earthquake occurring
during the service life of a dam on Glacier Fork.
Probability of earthquake with M > 6.5 \Mihln 100 years & 50 km
ProMblllly
100
090
080
060
0.50
0.40
0.30 025
020
015
012
010
008
006
004
003
0.02
O.Ql
000
11!11 XI1'.U ,1414~.10 !IO..,_._ ..... on__,_, ......... _....,........_ .. .,_._..., ______ ..._. • ....,._
Figure 8.15. Probability of magnitude 6.5 earthquake occurring within 50 km (31 miles) in the next 100 years. The
Glacier Fork site is shown as the small triangle in the center ofthe figure. USGS National Earthquake Hazard Mapping
Project.
Probability of earthquake with M > 7.0 within 100 years & 50 km
l'nlbMI!IIty
1.00
0.90
0.80
0 .60
050
0 .40
0 .30
025
020
015
0 12
010
008
006
004
0 .03
0 02
001
000
&D :0012..,. 'l9'..0 6o1 ] tQ~--ore•r .. .a,_ .. _____ .., .. _.,....., ____ , __ ~_..-
Figure 8.16. Probability of magnitude 7.0 earthquake occurring within 50 km (31 miles) in the next 100 yean. The
Glacier Fork site is shown as the small triangle in the center oftbe figure. USGS National Earthquake Hazard Mapping
Project.
Probability of earthquake with M > 7.5 within 100 years & 50 km
82"00 100
0.90
080
060
0.50
040
030
025
020
015
012
010
0.08
006
004
003
0 02
0.01
000
~1;..U 'tl't6ol~ N~--·0..-T_),_ .. ______ ., __ ....,.,_. _____ • ___ ............
Figure 8.17. Probability of magnitude 7.5 earthquake occurring within 50 km (31 miles) in the next 100 yean. The
Glacier Fork site is shown as the small triangle in the center of the figure. USGS National Earthquake Hazard Mapping
Project.
From Figures B.15 , B.16, and B.17 above, the probability of an earthquake with a magnitude of
6.5 to 7.5 occurring within 31 miles ofthe Glacier Fork in the next 100 years ranges from 90
percent to 30 percent. For an M6.5 earthquake in this area and time frame , the probability of
occurrence is shown to be between 80 and 90 percent. For the M7.0 earthquake, the probability
of occurrence is shown to be between 60 and 80 percent. And for the M7 .5 earthquake, the
probability of occurrence is shown to decrease to between 30 and 40 percent. The likelihood of a
large earthquake occurring within the service life of the facility as shown in these figures
demonstrates the need for facility design to withstand strong ground motions .
8.8. MATERIAL SOURCES
Knik River flows across an outwash plain formed of vast deposits of silt, sand, gravel, cobbles ,
and boulders deposited by the melt waters of the Knik Glacier (Figures B.l8-20). Particle sizes
exposed on the ground surface range from sand-size to 12-inch stones of igneous and
metamorphic rock. Particles tend to be sub-round to round. The bulk of the material on the
surface appears to be in the gravel to cobble size range although some segregation can be
expected due to fluvial and wind processes. Progressively fmer particle gradations are
anticipated downstream due to segregation inherent in fluvial processes. Fine sand and silt-sized
particles are likely to have been removed from the ground surface by wind action but are
anticipated to be present in the subsurface.
KNIK GLACIER
OUTWASH PLAIN
Figure 8.18. Upper end ofKoik Glacier outwash plain.
KNIK VAU.EY
OUTWASH PLAIN
Figure 8.19. Knik Valley and outwash plain.
Figure 8.20. Sediment deposition near the mouth of Glacier Fork.
Appendix C: Glacier Fork Power Integration
L ~R I ONE COMPANY ..£"I.A.. Many Solutions'"
To: File
From: Paul Berkshire, HDR Alaska
CC:
Date: December 31, 2012
Memo
Project: Glacier Fork Hydropower
Reconnaissance Study
Job No: 175692
Power Integration Memorandum
1.1 Background
The Glacier Fork hydroelectric project is a proposed 85 MW run-of-river facility with its
powerhouse located near the terminus of the Knik Glacier, approximately 20 miles east of
Palmer, AK. A Regional Integrated Resource Plan (RIRP) prepared by the Alaska Energy
Authority (AEA) identified the Glacier Fork project as a potential new resource for the region.
However, the project was newly proposed and little technical information was available.
Subsequent to the completion of the RIRP report, the AEA commissioned the U.S. Army Corps
of Engineers (USCOE) to perform a reconnaissance level assessment ofthe project.
1.2 Scope of Work
HDR Alaska, Inc. (HDR) was contracted by the USCOE (Agreement #:W911KB-10-D-0011) to
assist in the evaluation of the transmission line alternatives for the project. Specifically, HDR
was to determine the best location to interconnect with the existing railbelt grid, the preferred
route for the transmission line and a reconnaissance level cost estimate for the line and
interconnection.
1.3 Existing System
The existing railbelt grid is a transmission system stretching from Fairbanks to the Kenai
Peninsula. The primary voltage of the system is 115 kV. The nearest point of interconnection to
the grid would be in the Palmer, AK area, which is serviced by the Matanuska Electric
Association (MEA).
1.3.1 Discussions with MEA
HDR contacted Mr. Gary Kuhn at the MEA on October 15,2011 to discuss the potential project.
He indicated that the MEA has a residential distribution system that extends to Hunter Creek on
the south side of the Knik River. However, this system is of insufficient capacity to transmit the
power from the project.
1.3.1.1 Point of Interconnection
Subject to an interconnection and system study, the MEA indicated that the logical point of
interconnection would be to the 115 kV transmission line from the Eklutna hydroelectric project
at the existing Butte substation. The Butte substation is located at the intersection of the Old
HDR Alaska, Inc.
1
2525 C Street, SUite 305
Anchorage, AK 99503-2632 I Phone (907) 644-2000
Fax (907) 644-2022
www.hdnnc.com
I Page1of6
Glenn Highway and Plumley Road. The Butte substation has adequate physical room for
expansion. However, the Glacier Fork Project would require its own new facilities . Alternatively
a new substation could be built near the Old Glenn Highway bridge .
1.3.1.2 Substation Requirements
The MEA 's current standards are for substations to be designed in a ring-bus configuration .
1.3.1.3 230 kV Backbone
The RIRP and other long-range planning efforts have determined that the optimal configuration
for the railbelt grid would be to have the transmission system operating at 230 kV. The RIRP
identified multiple required upgrade projects , however based upon recent discussions between
the member utilities , the MEA indicated that upgrading the existing system to 230 kV was not a
near term priority.
1.4 Transmission Line
In order to develop reconnaissance level designs and cost estimates , the following assumptions
have been made:
• The transmission line would connect the proposed powerhouse to the Eklutna
transmission line.
• The transmission line would be 115 kV , single-circuit construction using tubular steel
guyed V and H-frame towers at an average spacing of800 feet with 795 ACSR conductor
and two 3/8" EHS shield wires.
• Preliminary planning study suggests that 795 ACSR "Drake " conductor would be
sufficient for this line . Using a power factor of 95 percent , losses would be acceptable at
less than 2 percent. A larger conductor would reduce losses even farther . These numbers
are preliminary and subject to change with further analysis.
• The transmission line would require a 150-foot-wide right-of-way (ROW).
HDR Alak1, Inc.
1
2525 C Street, sune 305
Anchorage, AK 99503-2632 I Phone (907) 644-2000
Fax (907) 644-2022
www.hdri nc .com
I Page2 of6
• The substation requirements would be based upon a ring-bus configuration and would be
the same for all route alternatives.
• At the generation end of the line it is assumed that the switchyard is included as part of
the overall generation plant development; as such these costs have not been estimated
here.
1.4.1 Corridor Options
Corridor options have been developed considering initial construction and inspection and
maintenance. Typically in Alaska, transmission lines located near road access are less expensive
to build and easier to operate and maintain. Therefore, the corridors considered generally try to
make the most use of existing and proposed roads. Proposed access routes are shown in the
following figure from the Glacier Fork Reconnaissance Hydropower Study. All transmission
line routes originate at the project powerhouse and terminate at a new substation along the
existing Eklutna 115 kV transmission line.
Preferred access to Glacier Fork is on the North Side of the River as shown in options 2A and 28.
Site Access
-1
-2A
28
Fleure 41: Road Ac:c:ess Alternetlves for Glec:ler Fork
Proposed Access Road Alternatives
1.4.1.1 Site Reconnaissance
N
W~E
On October 1, 2012 HDR engineers performed a helicopter aerial reconnaissance of three
possible routes along the Knik River. The routes and observations from powerhouse to
substation are presented below.
HDR Alllka, Inc:.
1
2525 C Street, Suite 305
Anchorage, AK 99503·2632 I Phone (907) 644-2000
Fax (907) 644-2022
www.hdrinc.com
I Pq3of6
1.4.1.2 Route Tl
Route T1 follows the north side of the Knik River outside of the flood plain of the river generally
along access route 2B. At a point directly east of the Butte substation the line would go west
across Gull Lake and then along Plumley Road to the substation. This route would be
approximately 21 miles long.
Aerial reconnaissance showed this route would primarily be a side-slope route along the toe of
generally steep terrain. The foundation conditions are assumed to be primarily bedrock. Due to
the steep terrain, the line would need to strategically span talus slopes and avalanche zones .
Portion of Route Tl looking west across Gull Lake
1.4.1.3 Route T2
Route T2 follows the north side of the Knik River along the side-slope for approximately 6 miles
and then across the flood plain, generally along access route 2A. Because the majority of this
route is over land created by glacial outwash, the geotechnical foundation conditions are
assumed to be poor. Additionally, due to poor geotechnical conditions , the Knik River is subject
to large scale meandering during flood events that would put additional design requirements on
the line. This route would be approximately 21 miles long .
HDR Alaka,lnc:.
1
2525 C S1reet, Suije 305
Anchorage, AI( 99503·2632 I Phone (907) 644-2000
Fax (907) 644-2022
www.hckinc.com
I Page4ol6
Portion of Route T1 and T2 looking northwest.
1.4.1.4 Route T3
Route T3 follows the north side of the Knik River along the side slope for approximately 4 miles
and then turns southward and crosses the Knik River to a point near Hunter Creek. Route T3
would generally parallel road access alternative 1 and would include a river crossing
approximately 3 miles long. From Hunter Creek, the route would generally follow the existing
road system to a point of interconnection near where the Old Glenn Highway crosses the Knik
River. This route would require substantial foundations where the line crosses the river. This
route would be approximately 21 miles long.
OUTWASH f'I.NN
HDR Alaakl, Inc.
KNIK VAI..l.f.'i
1
2525 C Street, Suite 305
Anchofage, AK 99503-2632 I Page5ol6
1.4.2 Cost Estimate
Since the routes are of similar lengths, the reconnaissance level cost estimate for any of the three
alternatives is summarized below.
Description
Powerhouse to Substation
Topographic Survey
Geotechnical Investigation
Ground Survey
(Land Ties, easement plats, crossing data)
Structure Staking for Construction
Line Construction (Material & Labor) -
Moderate terrain, road access
Substations
Powerhouse
Butte
Transformers
HOR Alaka, Inc.
Unit Cost Amount
MI 21 $10,000 $210,000
MI 21 $70,000 $1,470,000
MI 21 $15,000 $315,000
MI 21 $15,000 $315,000
MI 21 $1,200,000 $25,200,000
LS 1 $2,500,000 $2,500,000
LS 1 $4,000,000 $4,000,000
LS 1 $1,350,000 $1,350,000
Subtotal Transmission Facility
Contingency (30%)
Total Transmission Facility
$35,360,000
$10,700,000
$46,060,000
1
2525 C Street. Suite 305
Anchorage, AK 99503·2632 I Phone (907) 644-2000
Fax (907) 644-2022
www.hdrinc.com
I Page6of6
Appendix D: Rough Order of Magnitude Cost Estimate
Land and Land Rights
Structures and Improvements
Reservoir, Dams and Waterways
Waterwheels, Turbines and Generators
Accessory Electrical/Mechanical Equipment
Roads and Bridges
Transmission Plant
Contingency
Engineering ,Environmental ,Regulatory
Construction Management
Administrative & Gen. Expenses
Interest During Construction
GLACIER FORK HYDROELECTRIC PROJECT
Run-of-river Alternative
85MW
Subtotal
Subtotal
Subtotal
Total Project Cost
Not Included
$ 8,300,000
$ 272,700,000
$ 46,000,000
$ 5,400.000
$ 135,000,000
$ 36,700,000
$ 504,100,000
30% $ 151,300,000
$ 655,400,000
3.0% $ 19,700,000
1.0% $ 6,600,000
2.0% $ 13,200,000
$ 694,900,000
$ 89,000,000
$ 783,900,000
Structures and Improvements
Description Amount
Powerhouse
Power House (17,500 sq. ft) SF 17,500 $ 250 $ 4,375,000
Embankment Fill CY 41,782 $ 15 $ 626,736
Surface Coarse CY 7,500 $ 60 $ 450,000
Rock Excavation CY 4,500 $ 75 $ 337,500
Excavation CY 2,000 $ 25 $ 50,000
Clearing and Grubbing ACRE 6 $ 1,000 $ 6,000
Administration Building {1000 sq ft.) SF 1,000 $ 250 $ 250,000
Intake Maintenance Facilties (includes 200' x 300' embankment)
Intake Maintenance Building and Workshop (7,200 sq. ft) SF 7,200 $ 250 $ 1,800,000
Select Borrow CY 12,056 $ 15 $ 180,833
Surface Coarse CY 2,222 $ 60 $ 133,333
Structures and Improvements $ 8,209,403
Amount
Concrete Mass CY 6900 500 $ 3,450,000
Concrete Structural (incl. reinf.) CY 3600 1500 $ 5,400,000
Steel Rails {70 lb/yard) LBS 831600 2.5 $ 2,079,000
Tainter Gates {25' Wide) EA 3 750000 $ 2,250,000
Gate Hoists EA 3 250000 $ 750,000
Control Works Electrical LS 1 250000 $ 250,000
Control Works Mechanical LS 1 100000 $ 100,000
Dewatering During Construction LS 50000 $ 50,000
Dam Extension (Overflow Spillway)
Concrete Mass CY 10700 500 $ 5,350,000
Concrete Stuctural CY 1200 1500 $ 1,800,000
Rock Excavation CY 120000 75 $ 9,000,000
Desanding Basin and Intake
Concrete Structural {slab) CY 9500 1500 $ 14,250,000
Concrete Mass (Wing Walls) CY 7700 500 $ 3,850,000
Rock Excavation CY 176000 75 $ 13,200,000
Trash Racks LS 1 50000 $ 50,000
Power Tunnel Intake Control Gate LS 1 1000000 $ 1,000,000
Sluice Tainter Gates {20' wide) EACH 2 525000 $ 1,050,000
Bridge over sluiceway SF 1200 500 $ 600,000
Base Course CY 8600 30 $ 258,000
Tunnel
Tunnel Excavation CY 147100 500 $ 73,550,000
Rock Bolts EA 24700 1000 $ 24,700,000
Shotcrete CY 5000 750 $ 3,750,000
Concrete lining (Inc Reinforcing and overbreak) CY 34500 2250 $ 77,625,000
Steel Mesh SY 44200 100 $ 4,420,000
Portals EA 2 500000 $ 1,000,000
Steel Penstock
Steel Penstock (10' Dia x 1/2") LF 1000 9000 $ 9,000,000
Ball Valve EA 1 1500000 $ 1,500,000
Bifurcation Valves EA 5 750000 $ 3,750,000
Concrete Supports CY 400 1500 $ 600,000
Bifurcations EA 5 100000 $ 500,000
Concrete Structural (thrust block) CY 1000 1500 $ 1,500,000
TailRace
Excavation CY 20000 25 $ 500,000
Downstream Sill LS $
Riprap lining CY 5500 100 $ 550,000
Temporary Diversion Dam During Construction
Upstream Diversion Dam LS 1 5000000 $ 5,000,000
Reservoirs, Dams and Waterways $ 272,682,000
Turbines and Generators
Description Amount
17 MW Impulse Turbine/Generator Complete $ 8,500,000 $ 42,500,000
Tubine installation EACH 5 $ 500,000 $ 2,500,000
Startup and testing LS 1 $1,000,000 $ 1,000,000
Turbines and Generators $ 46,000,000
Description Amount
Governors/HPU 250,000 $ 1,250,000
Switchgear LS 1 $1,000,000 $ 1,000,000
Control System LS 1 $ 500,000 $ 500,000
Auxiliary Equipment & Materials LS 1 $ 1,000,000 $ 1,000,000
Powerhouse Bridge Crane LS 1 $ 400,000 $ 400,000
Gate Operators & controls EA 5 $ 250,000 $ 1,250,000
Accessory E-M Equipment $ 5,400,000
Description Amount
Glacier Fork Access Road (Common to All Alternatives)
DOT Select A CY 590,000 $ 30 $ 17,700,000
Embankment (DOT Select C) CY 240,000 $ 15 $ 3,600,000
Surface Coarse CY 90,000 $ 60 $ 5,400,000
Filter Fabric CY 960,000 $ 5 $ 4,800,000
36" CMP LF 7,000 $ 100 $ 700,000
Thaw Wire EACH 75 $ 5,000 $ 375,000
Clearing ACRE 230 $ 1,000 $ 230,000
Grubbing ACRE 90 $
Bridges SF 8,100 $ 500 $ 4,050,000
Access Road Erosion Protection
Riprap CY 500,000 $ 100 $ 50,000,000
Filter Stone CY 120,000 $ 30 $ 3,600,000
Revetment Fill (DOT Select C) CY 140,000 $ 15 $ 2,100,000
Excavation CY 460,000 $ 25 $ 11,500,000
Intake Works Access Road
Embankment (DOT Select C) CY 90,000 $ 15 $ 1,350,000
Surface Coarse CY 40,000 $ 60 $ 2,400,000
Rock Excavation CY 250,000 $ 75 $ 18,750,000
Filter Fabric SY 63,000 $ 5 $ 315,000
Clearing and Grubbing ACRE 80 $ 1,000 $ 80,000
Bridges SF 5,400 $ 500 $ 2,700,000
36" CMP LF 2,500 $ 100 $ 250,000
DOT Select A CY 168,000 $ 30 $ 5,040,000
Roads and Bridles $ 67,740,000
Erosion Protection $ 67,200,000
Transmission Facility
Description Amount
Powerhouse to Butte Substation
Topographic Survey Ml 21 $ 10,000 $ 210,000
Geotechnical Investigation Ml 21 $ 70,000 $ 1,470,000
Ground Survey (Land Ties, easement plats, crossing data) Ml 21 $ 15,000 $ 315,000
Structure Staking for Construction Ml 21 $ 15,000 $ 315,000
line Construction (Material & labor)-Moderate terrain, road access Ml 21 $1,200,000 $ 25,200,000
Powerhouse to Intake
Materials and Installation Ml 6.5 $ 200,000 $ 1,300,000
Substations
Powerhouse lS 1 $2,500,000 $ 2,500,000
Butte lS 1 $4,000,000 $ 4,000,000
Transformers LS $1,350,000 $ 1,350,000
Transmission Facility $ 36,660,000