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OFFICE OF ELECTRIC POWER REGULATION
FEDERAL ENERGY REGULATORY COMMISSION
MAY 1984
2-n
Table 2-2, Monthly Flow Requirements (cfs) at Gold Creek
Case
Month
A
Al
A2
C
C1
C2
D
Oct
5,000
5,000
5,000
5,000
5,000
5,000
5,000
Nov
5,000
5,000
5,000
5,000
5,000
5,000
5,000
Dec
5,000
5,000
5,000
5,000
5,000
5,000
5,000
Jan
5,000
5,000
5,000
5,000
5,000
5,000
5,000
Feb
5,000
5,000
5,000
5,000
5,000
5,000
5,000
Mar
5,000
5,000
5,000
5,000
5,000
5,000
5,000
Apr
5,000
5,000
5,000
5,000
5,000
5,000
5,000
May
4,060
5,000
5,000
6,000
6,000
6,000
6,000
Jun
4,000
5,000
5,000
6,000
6,000
6,000
6,000
Jul+'
4,000
5,100
5,320
6,480
6,530
6,920
7,260
Aug
6,000
8,000
10,000
12,000
14,060
16,000
19,000
SepTI
5,000
6,500
7,670
9,300
10,450
11,620
13,170
tt Derivation
of
transitional
flows:
Date
Case
Jul
Sep
A Al
A2
C
C1
C2
D
25
21
4,000
5,000
5,000
6,000
6,000
6,000
6,000
26
20
4,000
5,000
5,000
6,000
7,000
7,000
71500
19
19
4,000
5,000
5,000
7,000
8,000
8,500
9,000
18
18
4,000
5,000
6,000
8,000
9,000
10,000
10,500
17
17
4,000
5,000
7,000
9,000
10,000
11,500
12,000
16
16
4,000
6,000
8,000
10,000
11,000
13,000
14,000
15
15
5,000
7,000
9,000
11,000
12,500
14,500
- - - -
16,000
- - - -
- - -
Conversion:
- - -
- - - - - -
To convert
- - - - - -
cubic feet
- - - - -
per second
- - - - -
(cfs) to
- - - - - -
cubic meters
- -
per second
(m'is),
multiply by
0.0283.
Source: Application Exhibit E, Vol. 5, Chap. 2, Table E.2.34
2160
0 2120
>
W
N
W 2100
2080
0 N D J
1460
1450
1440
cr
0 1420
w
ui
(t 1410
1400
1390
0 N
F M A M J J A S
MONTHS
WATANA RESERVOIR
D J F M A M J J A S
MONTHS
DEVIL CANYON RESERVOIR
Figure 2-10. Reservoir Rule Curves --Watana and Devil Canyon.
[Source: Application Exhibit B, Fig. B.69]
2-23
trained and assigned to monitor storage and transfer of oil and fuel and to identify and clean
up spilled oil and other hazardous material. All personnel employed on the project, especially
field personnel, would be trained to respond to fuel spills in accordance with an approved
oil -spill contingency plan.
Vehicle accidents, although difficult to fully protect against, can be minimized by constructing
the roads with properly designed curves to accommodate winter driving conditions. The roads
would be provided with adequate signs; during the winter, difficult stretches would be regularly
cleared and sanded. In summer, dust would be controlled with water.
Discharge of camp effluents could result in increased levels of metals and nutrient loading.
Concrete batchinq plants release high alkaline effluents. Effluents would complywith ADE-/USED
effluent standards. The concrete batching effluent would be neutralized and treated prior to
discharge to avoid impacts related to pH and toxicity.
Adverse impacts associated with removing vegetation along streams are: (1) accelerated erosion
into the streams; (2) altered temperature regimes; and (3) operation of equipment in perennial
or ephemeral streambeds. Clearing would be scheduled as close to reservoir filling as is
feasible. Control methods would be employed wherever needed to minimize erosion to streams. To
the extent practicable, clearing would take place during the .,iinter. Cleared vegetation would
be dried for one season and burned in place.
The primary water quantity and water quality issues during filling and operation of the Watana
and Devil Canyon would be the maintenance of minimum downstream flows for fishery resources and
other instream flow needs, maintenance of an acceptable downstream thermal regime throughout the
year, and control of downstream gas supersaturation below the dams.
Selection of appropriate flow regime for reservoir operations consistent with power needs is
offered by the Applicant as a measure to avoid or minimize impacts. The Watana filling flow in
the period October to April would reflect inflow to the reservoir; during operation, flows
during this period would be 5,000 cfs (140 m Vs). Because slough overtopping is expected in
this period, with consequent temperature reduction in salmon incubation areas, the Applicant has
proposed to heighten upstream berms. From May to the last week of July, the target flow would
be 6,000 cfs (170 m /s) to allow mainstem fish movement. A brief flow peak proposed by the
Applicant for this time period (of a magnitude to be specified following additional biological
studies) would be generated to stimulate outmigration of juvenile salmon. During the last week
Of July, flows would be increased from 6,000 cfs to 12,000 cfs (170 to 340 m3/s), in increments
of 1000 cfs (28 m3/s) and maintained through mid -September to provide access by sockeye and chum
salmon to sloughs upstream of Talkeetna. To rectify anticipated difficulty with slough access,
even at 12,000 cfs (340 m3/s), the Applicant proposes to structurally modify the streambed
profiles of eight sloughs. To rectify decreases in intragravel flow caused by lowered river
elevations, the Applicant has suggested piping mainstem water, through the berm and releasing it
beneath the substrate. Compensation for anticipated loss of slough spawning habitat would be
accomplished by gravel cleaning in side channels, mainstem areas, and currently unused sloughs
in order to develop new spawning substrates. An estimated 432,315 ft2 (38,902 m2) of spawning
habitat would be created, which is 187,000 ft2 (16,830 m2) greater than the estimated slough
spawning habitat used by salmon upstream of Talkeetna in 1981 and 1982. As a last alternative
for compensation, the Applicant has indicated that a hatchery for chum salmon could be developed.
The Applicant has proposed using multi -level water intakes on hydropower generating facilities
at Watana and Devil Canyon dams as a measure to mitigate the unavoidable temperature changes
associated with creation of a reservoir. the multi -level intake strucutres would be used to
select temperatures within the stratified reservoir that most closely match the pre -project
thermal regime. This sytem would not be operative during reservoir filling.
The Applicant's plan for mitigating nitrogen supersaturation downstream of the dams is to install
fixed cone valves on the outlet facility. These fixed cone valves would be used during augmenta-
tion and excess flows. Nitrogen supersaturation of turbine flows would be mitigated by having
subsurface discharge to minimize air entrainment.
2. 1. 12. 3 Fisheries
The ADD]icant has provided a conceptual plan for nit gation of anticipated impacts to fishery
resources. Details of the plan a further resolut�on of the aquatic sources to be impacted
by the project.
The 4�cjec`i,:e of fisheries mitiga�ion planning for the project has heen to 1pFrcvide hab-'tat of
suft,cier�t quality and quantity to maintain ❑atural rep'roducinq populations" �rherever this 4
compatible,aith the hydroelectric project's power objectives. Artificial propagation is contem-
plated only as a last resort.
2-29
2,1.12.8 Visual Resources
The Applicant's visual resource mitigation plan is designed to reduce or' eliminate adverse
impacts due to project development. The emphasis of the plan is on (1) avoidance of critical
environments, including ongoing site refinements throughout the design phase, (2) use of best
development practices and site -sensitive engineering, and (3) rehabilitation. The Applicant has
identified four major categories of mitigation: (1) additional studies, (2) best development
practices, (3) creative engineering design, and (4) the use of form, line, color, and texture
(Exhibit E, Vol. 8, Chap. 8, p. E-8-47 ). Additional mi ti ative
at wo
visual resource impacts include vegetation impact miti
tion 2.1.12.4.1. gatgve techeiiquessderscribedldnrSercce
During the Phase II detailed design process, additional studies to resolve the visual impacts
would be performed by an interdisciplinary design team. Potential aesthetic impacts would be
further ameliorated through site -specific design ana is and development. b'isual resource
impacts would be mitigated through siting studies (e.g., avoidance of thav-susceptible areas)
and alternative solutions (e.g., project design changes). Additional measures that would be
implemented would include best development practices through construction techniques (e.g.,
construction equipment would be confined to gravel roads and construction zone areas), rehabili-
tation techniques (e.g., grading to contour and reseeding), and operation policies (e.g., restrict-
ing off -road vehicle use). Where project facilities would not be compatible with the surrounding
landscape character', creative engineering design measures would be taken (e.g., minimizing road
profile elevations to blend with existing natural contours). Finally, the use of form, line,
color, or texture could reduce visual impacts caused by project features (e.g., painting build-
ings an appropriate color to blend with the surrounding natural landscape).
2.1.12.9 Cultural Resources
The Applicant has recommended the investigation of all significant cultural resource sites
(i.e., those eligible for inclusion in the National Register of Historic Places) that would be
subject to unavoidable direct or indirect impacts resulting from project development. Preserva-
tion by avoidance (combined with a monitoring program) is recommended for significant sites that
would be exposed to potential impacts during either the construction or operation phases of the
project.
2.2 SUSITNA DEVELOPMENT ALTERNATIVES
2.2.1 Alternative Facility Designs
2.2.1.1 Applicant's Studies
The design of the proposed facilities at the Watana and Devil Canyon developments are the result
of detailed studies during which the design of each major component was evaluated relative to
increasingly refined criteria. The criteria for design included economics, environmental and
geotechnical constraints, load forecasts, and engineering considerations. A detailed discussion
of the various components and methodology for the screening and review of alternative general
arrangements of the components is presented in the Application (Exhibit B, Sec. 2). A summary
of these studies follows.
2.2.1.2 Alternative Watana Facilities
Main Dam. The Applicant selected tha Plpw/i i", f +k-
1 wdl,dnd dam crest based on consideration
of the value of the hydroelectric energy produced from the associa
and freeted reservoir, geotechnical
constraints on reservoir levels , board requirements. Three crest elevations were studied,
2240, 2190, and 2140 ft (682.8, 667.5 and 652.3 m). The dam type was selected based on a com-
parison of embankment, concrete arch, and concrete -faced rockfill dams for Watana. Comparison
criteria considered economics, availability of suitable construction materials, and expected
performance of the dam based on the seismic, climatic, and geotechnical conditions at each site.
Diversion Facilities. The topography of the site generall�� �,.
�aur�ng construction be accomplished usin d�eersion tunnel; dictates that diver<_ion of the river
9 n upstream and downstream coffer-
�ams protecting the main constructiun� area. A design flood
t .a
whir a currP�
i50 years was selected for the des. r� of the cot-erdams based on experience frequency of once
ence and practice with
ether major hydroelectric projects.
Concrete -lined and unlined rock tunnelswere compared. The reliabilit✓ of an unlined tunnel is
more dependent on rock conditions than is a lined tunnel, particularly given the extended period
during which the diversion scheme is required to operate. Based on these considerations, given
a considerably higher cost, together with the somewhat questionable feasibility of four unlined
tunnels with diameters approaching 50 ft (15 m) in the type of rock expected at the site, the aA
unlined tunnels were eliminated. The lined tunnel schemes examined were (1) pressure tunnel
with a free outlet, (2) pressure tunnel with a submerged outlet, and xh
9 (3) a free flow tunnel.
2-33
in the central area to carry project power from the Watana and Devil Canyon sites to the Willow -
Healy Intertie. One transmission corridor was then selected in each area, with the environ-
mental factors and technical and economic ratings being considered. Additionally, the choice of
the access route for the SUSitna development affected the choice of the transmission line corridor
in the central area.
The 'our corridors studied by the Applicant in the northern area varied in length from 85 to
115 mi (136 to 185 km). Only two route segments from Healy are practical because of topography,
with one along an existing transportation route being preferred.
The 15 corridors studied by the Applicant in the central area were reduced to seven because of
technical or economic unacceptability [i.e., mountain crossings over 4,000 ft (1,200 m)]. The
selection of the access route in September 1982 narrowed the corridors to four, all connecting
the Watana dam site, the Devil Canyon dam site, and the proposed Gold Creek substation on the
Intertie. The final selection amounted to a choice between two parallel corridor segments
connecting the two dam sites and two parallel corridor segments connecting the Devil Canyon site
with the Intertie substation. These four corridors are about 40 mi (64 km) long each.
The three corridors studied by the Applicant in the southern area included two connecting the
Willow substation and Point MacKenzie and one connecting Willow to Anchorage via Palmer. The
corridor via Palmer is the longest at 73 mi (117 km), but the preferred route from Willow to
Point MacKenzie via Red Shirt Lake is 38 mi (61 km) in length.
Figures 2-14 through 2-16 show routes of the proposed and alternative transmission -line segments
considered by the Applicant when selecting a preferred route.
2.2.4 Alternative Susitna Development Schemes
2.2.4.1 General
As indicated in Section 1.4.1, the FERC Staff has considered three alternative development
schemes for the Susitna River Basin: Watana I with Devil Canyon, Watana I with Modified High
Devil Canyon, and Watana I with a reregulating dam. The locations of these developments are
illustrated in Figure 2-17.
2.2.4.2 Watana I -Devil Canyon Development
Facilities. This development would be identical to the proposed project, with the exception
that Watana dam would be scaled down to have a crest elevation of 2,125 ft (648 m) and a normal
reservoir level of 2100 ft (640 m) [versus 2,210 ft (674 m) and 2,185 ft (666 m), respectively,
for the proposed dam].
Operation. This project would operate in the same manner as the proposed project, i.e., Watana I
would operate as a baseload plant until completion of Devil Canyon. After completion of Devil
Canyon, Watana I would operate as a peaking plant and Devil Canyon would be operated to maintain
a constant tailwater elevation at Watana I and to regulate Watana I discharges to meet downstream
fishery requirements.
2.2.4.3 Watana I -Modified High Devil Canyon Development
Facilities. The Watana I development would be as described in Section 2.2.4.2. The High Due vii
Canyon development would be located approximately at RM 157, or about 5 mi (8 km) upstream from
the proposed Devil Canyon site. The dam would be constructed of similar materials and designs
as the High Devil Canyon Dam studied by the Applicant (Exhibit B, Fig. B.9). It would be of
earth and rockfill construction with an impervious core, and a crest elevation of 1,495 ft
(456 m). It would have a normal maximum water surface elevation of 1,470 ft (448 m) and a
maximum height of approximately 595 ft (181 m). The south abutment spillway and north abutment
underground powerhouse would be similar in concept to High Devil Canyon.
Operation. This development would be ope,,ated in the same manner as the `�iatana i-Devil Canyon
Project.
f
{ 2.2.4.1 Niatana I-Reregulating Dam Development
( Facilities. This development woula incorporate a reregulating dam located approximately 16 mi
(24 km) downstream of Watana I. The Reregulating dam would be of earth and rockfill construc-
tion, with a crest elevation of 1,500 ft (457 m) and a maximum height of approximately 250 ft
(76 m). A spillway would be located on the northern abutment and a 200-MW powerhouse would be
downstream of the dam on the southern bank. This development would be similar in design to the
plan E3 of
Tunnel No. 3 Reregulation dam scheme considered by the Applicant in development