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Prepared by:
SUSITNA HYOROELECTRIC PROJECT
FERC LICENSE APPLICATION
EXHIBIT A
FIRST DRAFT
SEPTEMBER 17, 1982
'----ALASKA PO\tVER AUTHORITY __ -.~
{iil DOCUMENT DISTRIBUTION RECORD Page
John D. Lawrence
Engineer Co-ordinator
Typist Co-ordinator
License Application Information
Type of Document
Number of copies bound ___ _
Distributed to Address
Alaska Power Authority
Name of Cliont
FERC License Application -Exhibits A & B
Title of Document First Draft
P5700 September 1982
Charge Number Month Year
Number
Distributed
Alaska Power Authority 334 West 5th Avenue -.j
John D. • awrence Acres Buffalo Copy #4
Phil Hoover II Columbia II #5
File Copy II II Office II ..
/16
File Copy II Anchorage 11 II 17
Jeff McBee ll Buffalo ll ll #8
Spare·Copy II II II II #9.
File Copy !I II II II Jl.l 0 rr
Total
Distributed · 10
For .each document• that you co-ordmate, compl:rte the distribution sheet in triplicate; attach a copy of the dOcument to it;
distribute. as follows:
First copy -Central l!iles
Second copy ..-Engineer Co-ordinator
Third copy -Secretarial Supervisor
• For distrttx.won of proposals, refer to Secretarial Manual
Form llSA
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Prepared by:
· A~lm
10
SUSITNA HYDROELECTRIC PROJECT
FERC LJCENSE APPLiCATION
=
EXHIBIT A
FIRST DRAFT
SEPTEMBER 17, 1982
..._ _ _,_ALASKA PO\AJER AUTHORITY __ ___,
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EXHIBIT A -PROJECT DESCRIPTION
Watana -Sect ions 1 -6
Devil Canyon -Sections 7 -11
LIST OF TABLES
LIST OF FIGURES
1 -PROJECT STRUCTURES -WATANA DEVELOPMENT
1.1 -General Arrangement
1.2 -Main Dam
(a) Typical Cross Section
(b) Crest Details and Freeboard
(c) Grouting and ·Pressure Relief System
(d) Instrumentation
1.3 -Diversion
(a} Tunnels
(b) Cofferdams
(c) Tunnel Pot .. tals and Gate Structures
(d) Final Closure and Reservoir Filling
1.4-Emergency Release Facilities
1. 5 -Out 1 et F ac i 1 it i es
(a) Approach Channel and Intake
(b) Intake Gates and Trashracks
(c) Shaft and Tunnel
(d) Discharge Structure
(e) Fixed-Cone Discharge Valves
(f) Ring Follower Gates
(g) Discharge Area
1.6 -Main Spillway
(a) Approach Channel and Control Structure
(b) Sp i 11 way Gates and Ston 1 ogs
(c) Spillway Chute
(d) Fi ip Bucket
1.7 -Emergency Spillway ~.
{a) Fuse Plug and Approach Channel
(b) Discharg& Channel
1.8 -Power Intake
(a) Intake Structure
(b) Approach Channel
(c) Mechanical Arrangement
1.9 -Penstocks
(a) Steel Liner
(b) Concrete Lining
(c) Grouting and Pressure Relief System
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TABLE OF CONTENTS (Continued)
1.10 -Powerhouse
(a) Access Tunnels and Shafts
(-b) Powerhouse Cavern
(c) Transformer Gallery
(d) Surge Chamber
(e) Grouting and Press~re Reiief System (f) Cable Shafts
(g) Draft Tube Tunne 1 s
1.11 -Tailrace
1.12 -Access Roads
1~13 -Site Facilities
{a) General
(b) Temporary Camp and Village
(c) Permanent Town
(d) Site Power and Utilities
(e) Contractor's Area
1.14 -Relict Channel
(a) Surface Flows
(b) Subsurface Flows
(c) Permafrost
(d) Liquefaction
2 -RESERVOIR DATA -WATANA
3 -TURBINES AND GENERATORS -WATANA
3.1 -Unit Capacity
3.2 -Turbines
3.3 -Generators
{a) Type and Rating
(~) Unit Dimensions
{c) Generator Excitation System
3.4 -Governor System
4 -TRANSMISSION LINES -FROM WATANA TO INTERTIE AND INTERTIE TO
ANCHORAGE/FAIRBANKS 4.1 -Transmission Requirements
4.2 -Description of Facilities
4.3 -Construction Staging
5 -APPURTENANT MECHANICAL AND ELECTRICAL EQUIPMENT -WATANA
5.1 -Miscellaneous Mechanical Equipment
(a) Powerhouse Cranes
{b) Draft Tube Gates
(c) Surge Chamber Gate Crane
(d) Miscellaneous Cranes and Hoists
(e) Elevators
(f) Power Plant Mechanical Service Systems
(g) Surface Facilities Mechanical Service Systems
(h) Machine Shop Facilities
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TABlE OF CONTENTi (Continued)
5.2 -Accessory Electrical Equipment
(a) Transformers and H.V. Connections
(b) Main Transformers
(c) Ganerator I so 1 ated Phase Bus
(d) Generator Circuit Breakers
(e) 345 kV Oil-Filled Cable
(f) Control Systems
(g) Station Service Auxiliary AC and DC Systems
(h) Grounding Sy~;tem
{i} Lighting System
(j) Conmunications
5.3 -Switchyard Structures and Equipment
(a.) Single Line Diagram
(b) Switchyard Equipment
(c) Switchyard Structures and Layout
6 ·-PROJECT LANDS
6.1 -Significant Land Policies Affecting the Study Area
6.2 -Present Land Ownership Trends
(a) Anchorage-lni 11 ow
{b) Willow -Talkeetna
(c) Talkeenta ~ Fairbanks
(~\ Unpcr su~1·tn-R~~,·n "'I I'"' '-..J ,a. ......... ••
6.3 -Land Status Methodology
~ -PROJECT STRUCTURES -DEVIL CANYON DEVELOPMENT
7.1 ·· General Arrangement
7.2 -Arch Dam
(a) Foundati01ns
~ (b) Arch Dam Geometry
(c) Thrust Blocks
7.3 -Saddle Dam
(a) Typical Cross Section
·(b) Crest De1ta i 1 s and Freeboard
(c) Groutin!J and Pressure Relief System
(d) Instrumtantation
7.4-Diversion
(a) General
(b) Cofferdams.
(c) Tunnel Portals and Gates
{d) Final Closure and Reservoir Filling
7.5 -Outlet Facilities
(a) Outlet
(b) Fixed-Cone Valves
(c) Ring Follower Gates
(d) Trashracks
(e) Bulkhead Gates
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TABLE OF CONTENTS (Continued)
7.6 -Main Spillway
(a) Approach Channel and Control Structure
(b) Spillway Chute
(c) Flip Bucket
(d) Plunge Pool
7 .] -Emergency Spillway
(a) Fuse Plug and Approach Channel
(b) Discharge Channel
7.8 -Devil Canyon Power Facilities
(a) Intake Structure
(b) Intake Gates
(c) Intake Bulkhead Gates
(d) Trashracks
(e) Intake Gantry Crane
7.9-Penstocks ,
(a) Steel Liner
(b) Concrete Liner
(c) Grouting and Pressure Relief System
7.10 -Powerhouse and Related Structures
(a) Access Tunnels and Shafts
(b) Powerhouse Cavern
(c) Transfonner Gallery
(d) Surge Chamber
(e) Draft Tube Tunnels
7.11 -Tailrace Tunnel
7.12 -Access Roads
7.13 -Site Facilities
(a) Temporary Camp and Village
(b) Site Power and Utilities
(c) Contractor's Area
8 -DEVIL CANYON RESERVOIR
9 -TURBINES AND GENERATORS -DEVIL CANYON
9.1 -Unit Capacity
9.2 -Turbines
9.3 -Generators
9.4 -Governor System
10 -TRANSMISSION LINES -DEVIL CANYON
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fABLE OF CONTENTS {Continued)
11 -APPURTENANT EQUIPMENT ... DEVIL CANYON
11.1 -Miscellaneous Mechanical Equipment
(a} Compensation Flow Pumps
(b) Powerhouse Cranes
(c) Draft Tube Gates
(d) Draft Tube Gate Crane
(e) Miscellaneous Cranes and Hoists
(f) Elevators
(g) Power P1 ant Mechanical Service Systems
(h) .surface Facilities Mechanical Service Systems
(i} Machine Shop Facilities
11.2 -Accessory Electrical Equipment
(a) General
(b) Transformers and HV Connections
{c) Main Transformers
(d) Generator Isolated Phase Bus
{e) 345 kV Oil-Fi11ed Cable
(f) Control Systems
(g) Station Service Auxiliary AC and DC Systems
(h) Other Accessory Electrical Systems
11.3 -Swi tchyard Structures and Equipment
(a) Single Line. Diagram
(b) Switchyard Equipment
(c) Swi tchyard Structures and Layout
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EXHIBIT A -PROJECT DESCRIPTION
LIST OF TABLES
Number
A.l
Tit'le -.--
Principal Project Parameter:s
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EXHIBIT A ~ PROJECT DESCRIPTION
LIST OF FIGURES
Nv.mber
A .. l
Title
Watana Reservoir Emergency Drawdown
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EXHIBIT A -PROJECT DESCRIPTION
The Susitna Hydroelectric project will comprise two major developments
on the Susitna River some 180 miles north and east of Anchorage,
Alaska. The first phase of the project will ·be the Watana Project
which will incorporate an earthfill dam, together with associated di-
version, spillway, and .power facilities. The second phase will include
the Devil Canyon concrete arch dam and associated facilities .
The description of the Watana project is presented in the following
Sections 1 through 6; the Devil Canyon project is described in Sections
7 through 12. Reference drawings will be found in Exhibit F.
1 -PROJECT STRUCTURES -WATANA DEVELOPMENT
1.1 -General Arrangement .
The Watana Dam will create, a reservoir approximately 48 miles long,
with a surface area of 38,000 acres, and a gross storage capacity of
9,500,000 acre-feet at elevation 2185, the normal maximum op1:rating
1 eve 1.
The maximum water surface elevation
2201. The minimLLrn operating 1eve1
providing a live storage during
arce-feet.
during flood conditions wi 11 be
of the reservoir wi 11 be 2045,
normal operation of 4,200,000
The dam wi 11 be an embankment structure with a central core. The
nominal crest elevation of the dam will be 2205, with a maximum height
of 885 feet above the foundation and a crest length of 4,100 feet. The
embankment crest will initially be constructed to elevation 2210 to
.allow for potential seismic settlement. The total volume of the struc-
ture will be approximately 62,000,000 cubic yards. During construc-
t ion, the river wi 11 be diverted through two concrete-1 ined diversion
tunnels, each 38 feet in diameter and 4100 feet long, on the north bank
of the river. ~
The power intake wi 11 be 1 ocated on the north bank with an approach
channel excavated in rock. The intake will be a concrete structure
with multi-level gates capable of operation over the full 140 feet
drawdown range. From the intaRe structure, six concrete-1 ined ·pen-
stocks, each 17 feet in diameter, will lead to an underground po\'t~r
house complex housing s1x Francis turbines with a rated capacity of 170
MW and six semi-umbrella type generators each rated at 190 MVA. The
generators will be capable of delivering 115 percent of rated MVA
continuously (195.5 MVA) without exceeding 80°C temperature rise.
Ac~ess to the powerhouse camp 1 ex wi 11 be by means of an un 1 ined access
tunnel and a road which will pass from the crest of the dam,. down the
south bank of the river valley and across the embankment near the down-
stream toe. Turbine discharge will flow through six draft tube tunnels
to a surge chamber downstream of the powerhouse. The surge chamber
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will discharge to the river through two 34-foot diameter concrete-lined
tailrace tunnels. A separate transformer ga 11 ery just upstream from
the powerhouse cavern wi 11 house nine single-phase 15/345 k v trans-
formers (three transformers per group of two genera tors) e The
transformers will be connected by three 345 kV single-phase, oil-filled
cables through two cable shafts to the switchyard at the surface.
Outlet facilities will also be located on the north bank to discharge
a11 flood flo\'IS of up to 33,000 cfs, the estimated 50ayear flood., The
upstream gate structure wi 11 be adjacent to the power intake and wi 11
convey flows through a 28 feet diameter concrete-lined tunnel to six
fixed-cone discharge valves downstream of the dam. These valves wi 11
be housed beneath the spillway flip bucket and will be used to dissi-
pate energy and eliminate undesirable nitrogen supersaturation in the
river downstream from the dam during spillway operations. The main
spillway will also be located on the north bank. This spillway will
consist of an upstream ogee control structure with three vertica 1
fixed-wheel gates and an inclined concrete chute and flip bucket de-
signed to pass a maximum discharge of 115,000 cfs. This spillway, to-
gether with the outlet facilities will thus be capable of discharging
the estimated 10,000-year flooda An emergency spillway· and fuse plug
on the right bank will provide sufficient additional capacity to permit
discharge of the Probab1 e Maxi mum Flood (PMF) without overtopping the
dam. Emergency reiease facilities will be located in one of the diver-
sion tunnels after closure to allow lowering of the reservoir over a
period of time to permit emergency inspection or repair of impoundment
structures. '
A local depression on the north rim of the reservoir-· upstream of the
dam will be closed by a low freeboard dike, crest elevation 2210.
Provision wi 11 be made for monitoring potential seepage through this
area and placement of approximate filter blankets at Tsusena Creek
downstream.
1.2 -Main Dam
The main dam at Watana will be located at mile 184 above the mouth of
the Susitna River, in a broad U-shaped valley approximately 2.5 miles
upstream of the Tsuse·na Creek confluence. The dam will be of compacted
earth and rockfi11 construction and will consist of a central imper-
vious core protected by fine and coarse filters upstream and down-
stream. The downstream outer she 11 wi 11 consist of rock fi 11 and
alluvial gravel underlain by a toe drain and filter; and the upstream
outer shell of clean alluvial gravel. A typical cross section is shown
on Plate 9 and is described below.
(a) Typica't Cross Section
The central core slopes are 1H:4V with a top width of 35 feete
The thickness of the core at any horizontal section will be
slightly more than 0. 5 times the head of water at that section.
Minimum core-foundation contact wi 11 be 50 feet~ requir-ing flaring
of the cross section at each end of the embankment.
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(b)
The upstream and downstream filter zones will increase in thick-
ness from 45 and 30 feet respective iy near the crest of the dam to
a maximum i.n excess of 100 feet at the filter foundation contact.
They are sized to provide protection against possible piping
through transverse cracks that caul d occur because of settlement
or resulting from internal displacement during a seismic event ..
The she 11 s of the dam wi 11 consist primarily of compacted a 11 uv i a 1
gravels. The saturated upstream shell wi 11 consist of compacted
clean alluvial gravels processed to remove fines so that not more
than 10 percent of the materials is less than 3/8-inch in size to
minimize pore pressure generation and ensure rapid dissipation
should seismic shaking occur. The do\vnstream shell will be un-
saturated and therefore wi 11 not be affected by pore pressure
generation during a seismic event. This wi 11 be· constructed with
compacted, unprocessed alluvial gravels, and rockfill from the
surface or underground excavations.
Protect1on against wave and ice action on the upstream slope will
consist of a 10-foot layer of riprap comprising quarried rock up
to 36 inches fn size.
The vo 1 ume of materia 1 required to construct the Watana Dam is
presently estimated as follows:
• Core material:
• Fine filter material:
• Coarse filter material:
• Gravel and rockfi11 material:
Crest Details and Freeboard
8,250,000 cubic yards
4,260,000 cubic yards
3,560,000 cubic yards
45,500,000 cubic yards
The typical crest detail is shown in Pla~:e 9. Because of the nar-
rowing at the dam crest, the filter zones are reduced in width and
the upstream and downstream coarse fi 1 ters are e 1 imi nated. A
1 ayer of fi 1 ter fabric is incorporated to protect the core mate-
rial from damage by frost penetration and dessication, and to act
as a coarse filter where required.
The nominal crest elevation of the ~latana Dam, after estimated
static and seismic settlement have taken place, will be 2205.
Allowances wi 11 be made during construction of the dam to a 11 ow
for static settlement of the fill following completion, settlement
on saturation of the upstream shell, and possible settlement
because of seismic shaking. () ·
An allowance will be made for settlement due to seismic loading of
up to 0. 5 percent of the height of the dam, or approximately 5
feet. The elevation at the center of the dam prior to any seismic
settlement \'li 11 therefore be 2210. At each abutment, the crest
elevation will be 2207, allowing for 2 feet of seismic settlement.
Under normal operating conditions, the minimum freeboard relative
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to the maximum operating pool elevation of 2185 will therefore be
20 feet, not including settlement allowances.
During construction of the dam, additional allowances will be made
for post-construction settlement of the dam under its own weight
and for the e/fects of saturation on the upstream gravel fill when
the reservoir· is first filled. These allowances will be provided
for in construction specifications and are consequently not shown
on the drawings at this time.. For initial cost estimating pur-
pos~s, 1 percent of the height of the dam has been a 11 owed, or
approximately 9 feet. The additional heig~t constructed into the
dam for these settlements will be accomplished by steepening both
slopes above approximately. Elevation 1850. These settlement
allowances are conservative. when compared with observed settle-
ments of similar structures. However, provision will be made dur-
ing construction for placement of additional fill at the crest
should settlements exceed these estimates •
The freeboard allowance of 20 feet is based on the worst con-
ceivab1e combination of flood, wave and run up water levels which
may occur after all settlement has taken place.
Ultimate security against overtopping of the main dam is provided
by the emergency spillway. Under normal operation this spillway
is sealed by a fuse p 1 ug dam across the entrance channe 1 ec This
p 1 ug is a grave 1 dam with a 1 owest crest e 1 ev-at ion of 2200 and
with strict design of the core, upstream face, and shell materials
to ensure that it will erode rapidly if overtopped, allowing f1ood
flows to be discharged freely through the emergency spillway. The
maximum reservoir level during .passage of the PMR is estimated as
2201.5 prior to erosion of the plug. The location and typical
cross section through the fuse plug are shown on Plate 20.
(c) Grouting and Pressure Relief System
A combination of consolidation grouting and cutoff curtain grout-
ing and installation of a downstream pressure relief (drainage)
system will be undertaken for the Watana dame
The curtain grouting and drilling for the pressure relief system
will be largely carried out from galleries in the rock foundation
in the abutments and beneath the dam. Detai 1 s of the grouting,
pressure relief and galleries are shown on Plate 10.
(d) Instrumentation
Instrumentation will be installed to provide monitoring of perfor-
mance of the dam and foundation during construction as well as
during operation. Instrunents for measuring internal vertical and
horizontal d i sp 1 acements, stresses and strains, and total and
fluid pressures, as well as surface monuments and markers will be
installed. Estimates of quantities of instrumentation have been
allowed for conservatively on the basis of currently available
geotechnical data for the site. These include: -
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-Piezometers
Piezometers are used to measure static pressure of fluid in the
pore spaces of soil, rockfill and in the rock foundation •
-Internal Vertical Movement Devices
• Cross-arm settlement devices as developed by the USBR.
• Various versions of the taut-wire devices which have been
developed to measure internal settlement.
• Hydraulic-settlement devices of various kinds.
-Internal Horizontal Movement Devices
• Taut-wire arrangements •
• Cross-arm devices.
• Inclinometers.
• Strain meterse
-Other Measuring Devices
• Stress meters.
• Surface monuments and alignment markers ..
• Seismographic records and seismoscopes.
• Flow meters to· record discharge--frpm dr·ainage and pressure
relief system.
1. 3 -Di verst on
{a) Tunnels
Diversion of the river flow during construction will be accom-
plished with two 38 foot diameter circular diversion tunnels. The
tunnels will be concrete-lined and 1 ocated on the north bank of
the river. The tunnels are 4,050 feet and 4,140 feet in length.
The diversion tunnels are shown in plan and profile on Plate llo
The tunne1 s are designed to pass a flood with a return frequency
of 1:50 years, equivalent to peak inflow of 81,100 cfs. Routing
effects are small and thus, at peak flow the tunnels will dis-
charge 80,500 cfs. The estimated maximum water surface elevation
upstream of the cofferdam for this discharge wi 11 be 1536 •
The upper tunnel (Tunnel No. 1) will be converted to the permanent
low level outlet after construction. A 1 ocal enlarging of the
tunnel diameter to 45 feet will accommodate the low level outlet
gates and expansion chamber.
(b) Cofferdams
The upstream cofferdam wi 11 be a zoned embankment founded on the
closure dam (see Plate 12). The closure dam wi11 be constructed
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to Elevation 1475 based on a low water elevation of 1470~ and will
consist of coarse material on the upstream side grading to finer
material on the downstream side. Provision has been made for a
cut-off through the river bed alluvium to bedrock to control
seepage during dam construction. The cement/bentonite slurry wall
cut-off and downstream pumping system is shown on Plate 12.
Above Elevation 1475 the cofferdam will be a zoned embankment con-
sisting of a central core, fine and coarse upstream and downstream
filters, and rock and/or gravel supporting shell zones with rip-
rap on the upstream face to resist ice action. This cofferdam
will provide a 9 foot freeboard for wave runup and ice
protection.
The downstream cofferdam wi 11 consist of only a closure dam con-
structed from approximate Elevation 1440 to 1472, and consisting
of coarse material on the downstream side grading to finer mater-
ial on the upstream side. Control of underseepage similar to that
for the upstream cofferdam will be required.
(c) Tunnel Portals and Gate Structures
A reinforced concrete gate structure wi 11 be 1 ocated at the up-
stream end of each tunnel, each housing two closure gates (see
Plate 13). ·
Each gate wi 11 be 38 foot high by 15 foot \'lide separated by a
center concrete pier. The g.ates will be of the fixed roller ver-
ti ca 1 1 ift type operated by a wire rope hoi st. The gate hoist
will be located in an enclosed, heated housing. Provision will be
made for heating the gates and gate guides. The gate in Tunnel
No. 1 will be designed to operate with the reservoir at Elevation
1540, a 50 foot operating head. The gate in Tunnel No. 2 wi11 be
designed to operate with the reservoir at Elevation 1540, a 120
foot operating head. The gate structures for each tunnel wi11 be
designated to :'lithstand· external (static) heads of 130 feet (No.
1) and 520 feet (No. 2), respectively. The downstream portals
wi 11 be reinforced concrete. structures with guides for stop logs.
(d) Final Closure and Reservoir Filling
As discussed above, the upper diversion tunnel (No. 1) wi 11 be
converted to a low level outlet or emergency release facility
during construction.
It is estimated one year will be required to construct and install
the permanent low level outlet in the existing tunnel. This will
require that the lower tunnel (No. 2) pass all flows during this
period. The main dam will, at this time, be at an elevation
suffic·ient to allow a 100 year recurrence interval flood (90!t000
cfs) to pass through Tunnel No. 2. This flow wi 11 result in a
reservoir elevation of 1625. During the construction of the low
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level outlet, the intake operating gate in the upper tunnel (No.
1) will be closed. Prior to commencing operation of the low level
outlet, coarse .trashracks. will be installed in the Tunnel No. 1
intake structure in the slots provided.
Upon commencing operation of the 1 ow 1 evel out 1 et, the 1 ower
tunnel (No. 2) will be closed with the intake gates, and
construction of the permanent p 1 ug and fi 11 i ng of the reservor
will commenceD
When the lower tunnel (No .. 2) is closed the main ·dam crest will
have reached an elevation sufficient to ·start filling the reser-
voir and still have adequate storage available to store a 250 year
recurrence period flood.
During the filling operation, the low level outlet will pass ave-
rage summer flows of up to 6,000 cfs and winter flows of up to 800
cfs. In case of a large flood occurring during the filling opera-
tion, the low level outlet would be opened to its maximum capacity
of 30,000 cfs until the reservoir pool was lowered to a safe
level.
The fi 11 ing of the reservoir is estimated to take 4 years to com-
plete to the full reservoir operating elevation of 2185. After 3
years of filling the reservoir will be at Elevation 2150 and will
allow_ operation of the powerplant to commence.
The filling sequence is based on the main dam elevation at any
time during construction and the capability of the reservoir stor-
age to absorb the inflow vo lt~me from a 250 year recurrence peri ad
flood without overtopping the main dam.
1.4 -Emergency Release Facilities
As discussed above~ the upper diversion Tunne 1 No. 1 wi 11 be converted
to a permanent low level outlet, or emergency release facility. Tnis
facility will be installed in two plugs9 separated by an expansion
chamber, and used to pass the required minimum discharge during the
reservoir filling period. They will also be used for draining the
reservoir in the event of an emergency.
The facility will have a capacity of 30,000 cfs at full reservo·ir pool
elevation. It will be capable of drawing the reservoir down in 14
months under average inflow conditions, initially in conjunction with
the main spillway and outlet facilities. The reservoir drawdown time
incorporating the low level is presented graphically in Figure A.1 for
various 11 start 11 times during the year.
Each plug will contain ~hree water passages in the configuration shown
in Plate 21. Each passage in the upstream plug wi 11 be provided with
two bonnetted type high pressure slide gates, the upstream gate serving
as a guard to the downstream gate. The downstream plug will also
contain three water passages, each with a. single gate.
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The 7. 5 feet by 11 •. 5 feet gates will be designed to withstand a total
static head of about 740 feet, but will be operated under a head of 600
feet or less.
During operation, the operating gate opening in the upstream plug will
be equal to the opening of the gate in the downstream plug, to effec-
tively ba 1 ance the head 1 asses across the gates. The maximum net
operating head across· a gate is not expected to exceed 340 feet.
Each gate will be equipped with a hydraulic cylinder operator designed
to raise or 1 O\t/er the gate against a maxi mum head of 560 feet. Th.ree
hydraulic units will be installed, one for the emergency gates., one for
the upstream operating gates and one for the do\'mStream operating
gates. Each gate will have an opening/closing time of 30 minutes. A
grease injection system will be installed in each gate to reduce
frictional forces when the gates are operated.
The design of the gate will be such that the hydraulic cylinder as well
as the cylinder pack j ng may be inspected and repaired without dewater-
ing the area around the gate. All gates may be locally · or remote ~,Y
operated.
To prevent concrete erosion, the conduits in each of the tunnel plugs
wi 11 be steei 1 i ned. An air vent will be i nsta 11 ed at the downstream
side of the gate in the downstream plug. Energy dissipation at the
downstream tunnel exit will be accomplished by means of a concrete flip
bucket placed in the exit channel (Plate 22).
1.5 -Outlet Facilities
The primary function of the outlet facilities will be to discharge
floods with recurrence frequencies of up to once in 50 years after they
have been routed through the Watana reservoir. The use of fixed cone
discharge valves will ensure that downstream erosion will be minimal
and the ai sso l ved nitrogen content in the discharges wi 11 be reduced
suffici-ently to avoid harmful effects on the downstream fish popula-
tion. A secondary function will be to provide the capability to
rapidly draw down the reservoir during an extreme emergency situation.
The facilities will be located on the north bank, and will consist of
a gate structure, pressure tunnel, and an energy di ssi pati on and con-
trol structure housing located beneath the spillway flip bucket.. This
structure wi 11 accommodate six fixed-cone valves which wi 11 discharge
into the river 105 feet below.
(a) Approach Channel and Intak~
The a~proach channel to the outlet facilities will be shared with
the po}'ler intake. The channe 1 wi 11 be 350 feet wide and excavated
to a maximum depth of approximately 150 feet in the bedrock with
an invert e 1 evati on of 2010. The gate structure wi 11 be founded
deep in the rock at the forebay end of the channel. The single
intake passage will have an invert elevation of 2012. It will be
divided upstream by a central concrete pier which wi 11 support
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steel trashracks located on the face of the structure, spanning
the openings to the water passage. The racks will be split into
panels mounted one above the other and run in vertical steel
guides installed at the upstream face. The trashrack p-anels can
be raised and lowered for cleaning and maintenance by a mobile
gantry crane located a.t deck level.
·Two fixed wheel gates will be located downstream of the racks~ be-
tween the pier and each of the sidewalls. These gates will be
operated by a mechanical hoist mounted above the deck of the
structurec The fixed whee 1 gates wi 11 not be used for flow con-
trol but will function as closure gates to isolate the downstream
tunnel and allow dewatering for maintenance of the tunnel or ring
gates located in the discharge structure. Stoplog guides will be
provided upstream of the two fix.ed wheel gates to permit dewater-
ing of the structure and access to the gate guides for
maintenance.
(b) Intake. Gates and Trashracks
The gates will be of the fixed wheel vertical lift type with down-
stream skinp1ate and seals .. The nominal gate size will be 18 feet
wide by 30 feet high. Each gate will be operated by a single drum
wire rope hoist mounted in an enclosed tower structure at the top
of the intake. The height of the tower structure wi 11 permit
ra1s1ng the gqtes to the intake deck for inspection and
maintenance.
The gates will be capable of being lowered either from a remote
control room or locally from the hoist area. Gate raising will be
from the hoist area onlyo ·
The trashracks wi 11 have a bar spacing of 7 inches, and will be
designed for a r~~aximum differential head of 40 feet. The maximum
net velocity through the racks will be 12 feet/s. Provision will
be made for monitoring the head 1 ass across the trashr,acks ..
(c) Shaft and Tunnel
Discharges will be conveyed from the upstream gate structure by a
concrete-1 ined ·tunnel terminating in a steel 1 iner and manifold.
The manifold will branch into six steel-lined tunnels which will
run through the main spillway flip bucket structure to the fixed
cone valves mounted in line with the downstream face.
The water passage wi 11 be 28 feet in diameter as far as the steel
manifold. The upstream concrete-lined portion will run a short
distance horizontally from the back of the intake structure before
dipping at an angle of 55° to a lower level tunne'i of similar
cross section. The lower tunnel wi 11 run at a 5% gradient to a
centerline elevation of 1560, approximately 450 feet upstream of
the f1ip bucket. At this point, the depth of overlying rock is
insufficient to withstand the 1 arge hydrostatic pressure which
will occur within the tunnel. Downstream of this point the tunnel
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will be steel lined. The steel liner will be 28 feet in diameter
and embedded in mass concrete filling the space between the iiner
and the surrounding rock. The area between the outside face of
the 1 i ner and the concrete will be contact grouted.
(d) Discharge Structure
The concrete discharge structure is sho\tm on P1 ate 17 e It wi 11
form a part of the flip bucket for the main spillway and will
house the fixed cone valves and individual upstream ring follower
gates. The valves will be set with a centerline elevation of 1560
and wi 11 discharge into the river approximately 105 feet be.l ow.
Openings . for the va 1 ves wi 11 be formed in the concrete and the
va 1 ves wi 11 be recessed within these openings sufficiently to
a 11 ow enc 1 osure for ease of rna i ntenance and heating of the move-
able valve sleeves. An access gallery upstream from the valves
wi 11 run the 1 ength of the discharge structure, and wi 11 termi na"te
in the access tunnel and access road on either side of the struc-
ture. Housing for the ring follower gates wi 11 be 1 ocated up-
stream from the fixed cone gate chambers. The ring follower gates
wi 11 operate in the stee 1 1 i ners and wi 11 serve to i so 1 ate the
discharge valves. Provision will be made for relatively easy
equipment maintenance a~d removal by means of a 25 ton service
crane, transfer trolley and individual 25 torr monorail hoists.
(e) Fixed Cone Discharqe Valves
Six 78-inch diameter fixed-cone discharge valves will be installed
at the downstream end of the outlet manifold, as shown on Plate
17. The valves will be opera.ted by two hydraulic cylinder opera-
tors. The valves .may be operated either locally or remotely.
(f) Ring Follower Gates
A ring follower gate will be installed upstream of each valve and
will be used:
-To permit inspection and maintenance of the fixed-cone valves;
-To relieve the hydrostatic pressure on the fixed-cone ·valves
when they are in the closed position; and
-To close against flowing water in the event of malfunction or
failure of the valves.
0
The ring follower gates will have a nominal diameter of 90 inches
and wi 11 be designed to ·w; thstand a t ota 1 static head of 630
feet.
The ring follow]r gates will be designed to be lowered under flow-
ing water cond~tions and raised under balanced head conditions. A
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operated by hydraulic cylinders from either a local or remote
1 ocati on.
(g) Discharge Are~
Inmediate1y downstream of the discharge structure, the rock wi 11
be excavated at a slope of 2H: 3V to a lower e 1 evati on of 1510.
face vli 11 be heavily reinforced by rock bo 1 ts and protected by a
concrete slab anchored to the face. The lower level wi 11 consist
of unlined rock extending to the river.
1. 6 -Main Spillway
The main spillway will provide discharge capability for floods exceed-
ing the capacity of the outlet facilities. The combined total capacity
of the main spillway and outlet facilities will be sufficient to pass
routed floods with a frequency of occurrence of up to once in 10~000
years.
The main spillways shown on Plate 14, will be located on the north pank
of the river and will consist of an approach channel, a gated agee
control structure, a concrete-lined chute, and a flip bucket.
The spillway is designed to discharge flows of up to 115,000 cfs with a
corresponding reservoir elevation of 2192. The total head dissipated
by the spillway is approximately 730 feet.
(a) Approach Channel and Control Structure
The approach channe 1 wi 11 be excavated to a maximum depth of
approximately 100 feet into rock. It is 1 ocated on the south s.ide
of the power intake and, in order to minimize its 1 ength, it is
partially integrated with the power approach channel upstream of
the intake structure.
The concrete control structure will be located at the end·of the
approach channel, adjacent to the right dam abutment in line with
the dam crest. Flows will be controlled by three 49 feet high by
36 feet wide vertical ·1ift gates, as shown on Plate 15. The
structure will be constt~ucted in individual monoliths separated by
construction joints. The main access route to the dam will pass.
across the roadway deck and along the dam crest.
Hydraulic model tests will be undertaken during the detailed
design stage· to confirm the precise geometry of the control
structure.
The ~ides of the approach channel wi 11 be excavated to 1H:4V
slopese Only localized rock bolting and shotcrete support are
required. The control structure will be founded deep in sound
rock and consolidation grouting is not anticipated. However,
minor shear or fracture zones passing through the foundation may
. require dental excavation, concrete backfill and/or consolidation
grouting. The slope of the contact surface between the dam core
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and the spillway control structure will be constructed at 1H:3V to
ensure sufficient contact stress and therefore prevent leakage.
The main dam grout curtain and drainage system wi 11 pass beneath
the structure. Access to the grouting tunnels will be via a ver-
tical shaft within the control structure side wall and a gallery
running through the agee weir.
(b) Spillway Gates and Stoplogs
The three spillway gates will be of the fixed wheel vertical lift
type operated by daub 1 e drum wire r op~ hoists 1 ocated in an en-
c 1 osed tower structure. The gate size is 36 feet wide by 49 feet
high, including freeboard allowance. The gates will have upstream
skinplates and will be totally enclosed to permit heating in the
event that winter operation is necessary. Provision will also be
made for heating the gate guides.
The height of the tower and bridge structure will permit raising
of the gates above the top of the spillway pier for gate inspec-
tion and maintenance.
An emergency engine wi 11 be provided to enab 1 e the gates to be
raised in the event of loss of power to the spillway gate hoist
motors.
Stop 1 og guides wi 11 be i nsta 11 ed upstream of each of the three
spillway gates. One set of stopl ogs wi 11 be provided to permit
servicing of the gate guides.
(c) Spillway Chute
The control structure will discharge down an ~nclined chute that
tapers slightly until a width of 80 feet is reached~ A constant
width of 80 feet is maintained over the remainder of its length ..
Convergence of the chute wa 11 s wi 11 be gradua 1 to minimize any
shock wave development.
The chute section will be rectangular in cross section, excavated
in rock, and 1 ined with concrete anchored to the rod<. An exten-
sive underdrai nage system is provided to ensure stabi 1 ity of the
structure. The dam grout curtain and drainage system will also
extend under the spillway controlestructure utilizing a gallery
through the mass concrete rollway. A system of box drains will be
constructed in the rock under the concrete slab in a herringbone
pattern at 20 feet spacing for the entire length of the spillway.
To avoid blockage of the system by freezing of the surface drains
a drainage gallery will be excavated at 30 feet deep over the en-
tire length of the spillway. Drain holes from the surface dra,ins
will intersect the gallery. Drainage holes drilled into the high
rock cuts will also ensure increased stability of excavatior:s.
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A series ·of four aeration galler·ies will be provided at intervals
down the chute to prevent cavitation damage of the concrete.
Details of these aeration devices are shown in Plate 16.
(d) Flip Bucket
The function of the flip bucket will be to direct the spillway
flow c 1 ear of the concrete structures and we 11 downstream into the
river be 1 ow. A mass concrete b 1 ock wi 11 form the fl i p bucket for
the main spillway. Detailed geometry of the bucket, as well as
dynamic pressures on the floor and walls of the structure, will be
confirmed by model studies.
1.7-Emergency Spillway
The emergency spillway will be located on the right side or the river
upstream of the main spillway and power intake structure (see Plate
20). The emergency spillway will consist of a long straight chute ex-
cavated in rock and leading in the direction of Tsusena Ct1 eek. An
erodible fuse plug, consisting of an impervious core .and fine gravel
materials, will be constructed at the upstream end. The plug will be
designed to wash away when overtopped, releasing flows of up to 160,000
cfs in excess of the combined main spillway and outlet facility capaci-
ties, thus preventing overtopping of the main dam under PMF
conditions.
(a) Fuse Plug and Approach Channel
The approach channe 1 to the fuse p 1 ug wi 11 be excavated in rock
and will have a width of 310 feet and invert elevation of 2170~
The main access road to the dam and powerhouse wi 11 cross the
channel by means of a bridge. The fuse plug will close the ap-
proach channe 1, and wi 11 have a maximum height of 31.5 feet with a
crest elevation of 2201.5. The plug will have a core up to 10
feet wide, steeply inclined in the upstream direction, with fine
fi 1 ter zones upstream and downstream. It wi 11 be supported on a
downstream erodible shell of crushed stone or gravel up to 1 .. 5
inches in diameter. The crest of the plug will be 10 feet wide
and will be traversed by a 1.5 foot deep pilot channel. The .prin-
ciple of the plug is based on erosion progressing rapidly downward
and laterally from the pilot channel as soon as water levels rise
above the channel invert.
{b) Discharge Channel
The rock channel downstream of the fuse plug will narrow to 200
feet and continue in a straight line over a distance of 5~000 feet
at gradients of 1 .. 5 percent to 5 percent in the direction of
Tsusena Creek. The flow will discharge into a small valley on the
west side of and separate from the area of the relict channel. It
is estimated that flows down the channel would continue for a
period of 20 days under PMF conditions. Some erosion in the
channel.would occur~ but the. integrity of the main dam would not
be impaired. The reservoir would be drawn down to· Elevation 2170.
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Reconstruction of the fuse plug would be required prior to
refilling of the reservoir.
1.8 -Power Intake
[Note: This section will undergo revision after resolution of the
design drawdown.]
(a) Intake Structure
The power intake will be a concrete structure located deep in the
rock on the right bank. Access to the structure will be by road
from the south side of the emergency spillway bridge.
In order to draw from the reservoir surface over a drawdown range
of 140 feet, four openings will be provided in the upstream con-
c~ete wall of the structure for each of the six independent power
intakes. The upper opening will always be open, but the lower
three openings can be closed off by sliding steel-shutters oper-
ated in a common guide. All openings will be protected by up-
stream trashracks. A heated boom wi 11 operate in guides upstream
of the racks fo 11 owing the water surface9 keeping the ratks ice
free •
A lower control gate will be provided in each intake unit. A
single upstream bulkhead gate will be provided for routine main-
tenance of the six intake gates. In an emergency, stopl ogs can be
installed on the upstream wall of the power intake for work on the
trashracks or shutter guides.
The overall base width of the intake will be 300 feet, prov·:ding a
minimum spacing of penstock tunnel excavations of 2.5 times the
excavated diameterQ
The upper level of the concrete structure will be set at Elevation
2200, corresponding to the max·imum anticipated flood level.. The
level of the lowest intake is governed by the vortex criterion for
flow into the penstock from the minimum reservoir level elevation
of 2045. The foundation ·of the structure_ will be approximately
200 feet be 1 ow existing ground 1 eve 1 and is expected to be in
sound rock.
Mechanical equipment will be housed in a steel-frame building on
the upper level of the concrete structure. The general arrange-
ment of the power intake is shown on Plate 26.
(b) Approach Channel
The overall width of the approach channel is governed by the com-
bined width of the power intake and the outlet facilities gate
structure, and will be approximately 350 feet. n~e length of the
channel will be 1,000 feet.
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The maximum flow in the intake approach channel wi 11 occur when
six machines are operating and the outlet facilities are discharg-
ing at maximum design capacity. With the reservoir drawn down to
e 1 evat ion 2045, the ve 1 ocity in the approach channe 1 will be
3., 5 ft/s, which will not cause any erosion problems., Velocities
of 10 ft/s may occur where the intake approach channel intersects
the approach channel to the mai_n spillway.
(c) Mechanical Arrangement
(i) Ice Boom
A heated boom will be installed in ·.uides immediately up-
stream of the trashracks for each of the six power intakese
The boom will .be operated by a movable hoist and will auto-
matically follow the reservoir level. The boom will serve
to mir,imize ice accumulation in the trashrack and intake
shutter area, and prevent thermal ice-loading on the trash-racks.
{ i i) Trashracks
Each of the six power intakes wi 11 have four sets of trash-
racks, one set in front of each intake opening. Each set
of trashracks will be in two sections to facilitate hand-
1 i ng by th-e intake service crane. Each set of trashracks
will cover an opening 30 feet wide by 24 feet high. The
trashracks wi 1·1 have a bar spacing of 6 inches and wi 11 be
designed for a maximum differential head of 20 feet.
{iii) Intake Shutters
Each of the six power intakes will have three intake shut-
ters which will serve to prevent flow through the openings
behind which the shutters will be installed. As the reser-
voir level drops, the sliding shutters will be removed as
necessary using the intake service crane.
Each of the shutters will be designed for a differential
head of 25 feet. The lowest shutter at each power intake
will incorporate a flap gate which, with 25 feet differen-
tial head across the shutter, wi 11 a 11 ow maximum turbine
flow through the gate. This will prevent failure of the
shutters in the event of accidental blocking uf all intake. openings.
The shutter guides will be heated to facilitate removal in
sub-freezing weather. In addition, a bubbler system wi 11
be provided in the intake behind the shutters to keep the
intake structure water surface free of ice.
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(iv) Intake Service Crane
A single, overhead, traveling-bridge type intake service
crane wi 11 L'e ·provided in the intake service bui 1 ding. The
crane will be used for:
-Servicing the ice ~~lkhead and ice bulkhead hoist;
Handling and cleaning t~e trashracks;
-Handling the intake shutters;
-Handling the intake bulkhead gates; and
-Servicing the intake gate and hoist.
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The overhead crane wi 11 have a daub 1 e point 1 ift and fo 1-
1 ewers for-handling the trashrack shutters and bulkhead
gates. The crane will be radio-controlled with a pendant
or cab contro·l for bac.t(up.
(v) Intake Bulkhead Gates
One set of intake bulkhead gates will be provided for c1os-
; ng any one of the six intake openings upstream from the
intake gates. The bulkhead gates will be used to permit
inspection and maintenance of the intake shutters and in-
take guides. The gates will be designed to withstand full
differential pressure.
(vi) Intake Gates
The intake gates will close a clear opening of 17 feet x 17
feet. They will be of the vertical fixed wheel lift type
with upstream seals and skinplate~ ·
Each gate wi 11 be operated by a hydraulic cylinder type
hoist. The length of a cylinder will allow withdrawal af
the gate from the water flows The intake service crane
\'lill be used to raise the gate above deck level for main-
tenance. The gates wi 11 normally be closed under balanced
flm'l conditions to permit dewatering of the penstock and
turbine water passages for inspection and maintenance of
the turbines. The gates will also be designed to close in
an emergency with full turbine flow conditions in the event
of loss of control of the turbine.
1.9 -Penstocks
The general arrangement of the penstocks is shown on Plates 23 and 25.
Six penstocks wi 11 be provided to convey water from the power intake to
the pmt~erhouse, one penstock for each generating unit. -Each penstock
will be a concrete lined rock tunnel, 17 feet internal diameter. The
mininum lining thickness will be 12 inches, which will be increased as
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appropriate to v1ithstand design interna~ pressures.. The lateral spac-
ing between penstocks will be 50 feet on centers at the intake and this
\~i 11 increase to 60 feet on centers at the power house. The difference
in lateral spacing will be taken out at the upper horizontal bend. The
inclined sections of the concrete-lined penstocks will be at 55° to the
horizontal.
The design static head on each penstock is 763 feet at centerline dis-
tributor level (Elevation 1422). An allowance of 35 percent has been
made f•Jr pressure rise in the penstock caused by hydraulic transients.
(a) Steel Liner
The rock immediately adJacent to the powerhouse cavern will be in-
capable of resisting the internal hydraulic forces within the pen-
stocks; Consequently, the first 50 feet of each penstock upstream
of the powerhouse will be reinforced by a steel liner designed to
resist. the maximum design head, without support from the sur-
rounding rock. Beyond this section the stee1 liner wiil be ex-
tended a further 150 feet, and support from the surrounding rock
wi 11 be assumed, up to a maximum of 50 percent of the design
pressure.
The steel liner will be surrounded by a concrete infill, with a
minimum thickness of 24 inches. The internal diameter of the
steel lining will be 15 feet. A steel transition will be provided
between the liner and the 17-foot diameter concrete-lined pen-.
stock.
(b} .foncrete Lining
The penstocks will be fully lined with concrete from the intake to
the steel 1 ined section, the thickness of 1 ining varying with the
external hydrostatic head. The internal diameter of the concrete
lined penstock will be 17 feet. The. minimum lining thickness will
be 12 inches.
(c) Grouting and Pressure Relief System
A comprehensive pressure relief system wi 11 protect the under-
ground caverns against seepage from the high pressure penstock.
The system will comprise small diameter boreholes set out to in-
tercept the jointing in the rock. A grouting and drainage g_allery
wi 11 be located upstream .of the transfonner gallery.
1.10 -Powerhouse
The underground powerhouse camp 1 ex wi 11 be constructed beneath the
north abutment of the dam.· This will require the excavation in rock of
three major caverns, the powerhouse, transformer gallery, and surge
chamber with interconnecting rock tunnels for the draft tubes and
isolated phase bus ducts.
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Unlined rock tunnels, with concrete inverts where appropriate, will be
provided for vehicular access to the three main rock caverns and the
penstock construction adit. Vertical shafts will be provided for
personnel access to the underground powerhouse, for cable ducts from
the transfonner gallery, for surge chamber venting and for the heating
and venti 1 ation system.
The general layout of the powerhouse complex is shown in plan and sec-
tion in Plates 27 and 28, and in isometric projection in Plate 24. The
transformer gallery will .be located on the upstream side of the power-
house cavern;· the surge chamber wi 11 be located on the downstream
side.
The draft tube gate gallery and crane will be located in the surge
chamber cavern, above the maximum anticipated surge level. Provision
will ·also be made in the surge chamber for tailrace tunnel intake stop-
logs, which will be handled by the saille crane.
(a) Access Tunnels and Shafts
Vehicular access to the underground facilities at Watana will be
provided by a single unlined rock tunnel from the north bank area
adjacent to the diversion tunnel portal .. The access tunnel wi11
cross over the d iv ersi on tunne 1 s and then descend at a uniform
gradient to the south end of the powerhouse cavern at generator
floor level, Elevation 1463. Separate branch tunnels from the
main tunnel will provide access to the transformer gallery at
Elevation 1507, the penstock construction adit at Elevation 1420~
and the surge chamber at Elevation 1500. The maximum gradient
will be 6.9 percent on the construction access tunnel and on the
permanent access tunnels.
The cross section of the access tunnel has a modified horseshoe
shape, 35 feet wide by 28 feet high. The access tunnel branch to
the surge chamber and draft tube ga 11 ery wi 11 have a reduced sec-
tion, consistent with the anticipated size of vehicle and loading
required.
The main access shaft wi 11 be at the north end of the powerhouse
cavern, providing personnel a.ccess from the surface control build-
ing by elevatcr. Access tunnels will be provided from this shaft
for pedestrian acce~s to the transformer gallery and the draft
tube gate gallery. ~levator access will also be provided to the
fire protection head tank, located approximately 250 feet above
powerhouse 1 evel. The main access shaft will be 20 feet in
internal diameter with a concrete lining of 9 to 18 inches.
(b) Powerhouse Cavern
The main powerhouse cavern is designed to accommodate six vertical
shaft Francis turbines, in line, with direct coupling to synch-
ronous generators. Each unit has a nominal output of 170 MW.
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The length of th~ cavern will allow for a unit spacing of 60 feet,
with a 110-foot 1 ong service bay at the south end for routine
maintenance and for construction erection. Vehicular access will
be by tunnel to the generator floor at the south end.of the cav-
ern; pedestrian access will be by elevator from the surface con-
trol building to the north end of the cavern. Multiple stairway
access points will be available from the main floor to each gal-
lery 1 eve 1. Access to the transformer ga 11 ery from the powerhouse
will be by tunnel ft"'om the main access shaft, or by stairway
through each of the isolated phase bus shafts. A service elevator
will be provided from the maintenance area on the main floor level
to the machine shop and·stores area on tht turbine floor level.
Hatches wi 11 be provided through a 11 main floors for i nsta 11 at ion
and maintenance of heavy equipment using the powerhouse cranes.
(c) Transformer Gallery
The transformers will be located underground in a separate gal-
lery, 120 feet upstream from the main powerhouse cavern, with
three connecting t~nnels for the isolated phase bus. There will
be nine single-phase transformers rated at 15/345 kV, 122 MVA,
installed in groups of three transformers for two generating
units. Generator circuit breakers will be installed in the
powerhouse on the lower generator floor level.
The transformer gallery is 45 feet wide, 40 feet high, and 414
feet 1 ong; the bus tunnels are 16 feet wide and 16 feet high.
High voltage cables will be taken to the surface by two cable
shafts, each with an internal diameter of 7.5 feet. Provision has
been made far i nsta 11 at ion of an inspection hoist in each shaft.
A spare transformer wi 11 be 1 ocated in the transformer gallery,
and a spare HV circuit will also be provided for imRroved re1ia-
bi1 ity. The station service auxi 1 iary transformers (2 MVA) and
the surface auxiliary transformer (7.5/10 MVA) will be located in
the bus tunnels. Generator excitation transformers will be
1 ocated in the powerhouse on the main fl oar.
Vehicle access to the transformer gallery will be the main power-
house access tunnel at the south end. Pedestrian access will be
from the main access shaft or through each of the three isolated
phase bus tunnels.
(d) Surge Chamber
A surge chamber will be provided 120 feet downstream from the
powerhouse cavern to control pressure fluctuations i.n the turbine
draft tubes and tailrace tunnels under transient load conditions,
and to pro vi de storage of water for the machine start-up sequencea
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The chamber will be common to all six draft tubes, and under nor-
mal operatiorJ will discharge equally to the two tailrace tunnels.
The overall surge chamber size is 360 feet long, 50 feet wide, and
145 feet high {including the draft tube gate gallery).
The draft tube gate gallery and crane will be. located in the same
cavern, above the maximum anticipated surge level. The crane has
also been designed to allow installation of tailrace tunnel intake
stoplogs for emergency closure of either tailrace tunnel.
The chamber will generally be an unlined rock excavation, with
1 oca 1 ized rock support as necessary for stabi 1 ity of the roof arch
and wa 11 s. The gate guides for the draft tube gates and tailrace
stopl ogs will be of reinforced concrete, anchored to the rock by
rockbolts.
Access to the draft tube gate gallery wi 11 be by an ad it from the
main access tunnel. This access wil"l be widened locally for stor-
age of tailrace tunnel intake stoplogs.
(e) Grouting -Pr'essure Relief System
Centro 1 of seepage in the powerhouse area wi 11 be achieved by a
grout curta in upstream of the transformer ga 11 ery and an arrange-
ment of drainage holes downstream of this curtain. In addition,
drain holes will be drilled from the caverns extending to a depth
greater than the rock anchors. Seepage water will be collected by
surface drainage channels and directed into the powerhouse drain-
age system.
(f) Cable Shafts
Cable shafts are 8.5 feet in excavated diameter. Although not
required for rock stability, a 6-inch thick concrete 1 ini ng has
been specified for convenience of installing hoist, stairway and
cable supports.
(g) Draft Tube Tunnels
The draft tube tunnels will be shaped to provide a transition to a
uniform hot"seshoe section of 19 feet diameter with a 2.5 feet
minimum thickness concrete lining. The initial rock support will
be concentrated at the junctions with the ·powerhouse and surge
ch~ber where the two free faces give greatest potential for block
i nstabi 1 ity.
1.11 -Tailrace
Two· tailrace pressure tunnels will be provided at Watana to carry water
from the surge chamber to the river. The tunnels will have a modified
horseshoe cross.;.section with a major internal dimension of 34 feet.
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The tunnels wi 11 be fully concrete-1 ined throughout, with a min1mum
concrete thickness of 12 inches and a length of 1,800 feet. The tail-
race tunne.ls will be arranged to discharge into the river between the
main dam and the main spillway.
The upstreant sections of the tailrace tunnels are on bearing 249° and
par a 11 e 1 the main access tunne 1 • Q The southern tunne 1 joins the 1 ower
diversion tunnel and utjl izes the diversion portal for the tailrace
outlet. The. northern tunnel changes direction at the downstream end to
bear 238° and the portal is situated between the diversion tunnel
portals and the spillway flip bucket. The tunnels are concrete-lined
for hydraulic considerations.
The downstrecm porta 1 of the northern tunne 1 is 1 ocated between the
spillway flip bucket and diversion tunnel portal. A rock berm will be
1 eft in place to the south of the portal to separate the outlet and
diversion tunnel channels.
The tailrace portals will be reinforced concrete structures designed to
reduce the outlet flow velocity, and hence the velocity head loss at
the exit to the river.
1.12 -Access Roads
To be added in October.
1.13 -Site Facilities
(a) General
The construction of the Watana development will require various
far:il ities to support the construction activities throughout the
entire construction period. Following construction, the operation
of the Watana hydroelectric development will require certain perm-
anent staff and facilities to support the permanent operation and
maintenance program.
The most significant item among the site facilities will be. a com-
bination camp and village that will be constructed and maintained
at the project site.. The camp/vi11age will be largely a self-
sufficient community housing 4,000 people during construction of
the project. After construction is complete, it is planned to
dismantle and demobilize most of the facility and to reclaim the
area.. The dismantled buildings and other items from the camp will
be used as much as possible during c;onstruction of the Devil
Canyon development. Other site facilities inc1ude contractors•
work areas, site power, services, and communications. Items such
as power and communications wi 11 be required for construction
operations independent of camp operations. The same will be true
regarding a hospital or first aid room.
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Permanent facilities required will include a permanent town or
small conmunity for approximately 130 staff members and their
families. Other permanent facilities will include a mafntenance
building for use during subsequent operation of the power plant.
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A conceptual plan for the permanent town is shown on Plate 38.
(b) Temporary Camp and Village
The proposed :ocation of the camp and village will be on the north
bank of the Susitna River between Deadman and Tsusena Creek,
approximately 2. 5 mi 1 es northeast of the Watana Dam. The north
side of the Susitna River was chosen because the main access will
be from the north and south-facing slopes can be used for siting
the structures. The location is shown in Plate 36.
The camp will consist of portable woodframe dormitories ;or bache-
lors with modular mess halls, recreational buildings, !.lank, post
office, fire station, warehouses, hospital, offices, etc. The
camp will be a single status camp for approximately 3,600 workers.
The village, accommodating approximately 350 families, will be
grouped around a service core containing a school, gymnasium~
stores, and recreation· area.
The vi 11 age and camp areas wi 11 be separated by approximately 1. 5
miles to provide a buffer zone between areas. The hospital wi11
serve both the main camp and village.
The camp location will separate living areas from the \t~ork areas.
by a mile or more and keep travel time to work to less than 15
minutes for most personnel.
The camp/village \vi 11 be constructed in -stages to accommodate the
peak work force. The facilities have been designed for the peak
work force plus 10 percent for turnover. The turnover will in-
clude allowances for overlap of workers and vacations. The con-
ceptua 1 1 ayouts for the camp and vi 11 age are presented on Plate 37·
and 38.
{i) Site Preparption
Both the camp and the vi 11 age areas wi 11 be c 1 eared and 1 n
select areas, filter fabric will be installed, and granular
material placed over it for building foundations. At the
village site, selected areas will be left with trees and
natural vegetation intact. Topsoil stripped from the
adjacent dam borrow area will be utilized to reclaim camp
and village sites. ·
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Both the main camp and the village site have been selected
to provide well-drained land with natural slopes of 2 to 3
percente
(ii) Facilities
Construction camp buildings will consist largely of
trailer-type factory-built modules assembled at site to
prov1de the various facilities required. The modules will
be fabricated complete with heating, lighting and plumbing
services, interior finishes, furnishings, and equipment ..
Larger structures such as the central utilities building,
warehouses and hospital wi 11 be pre-engineered, steel-
framed structures with m:tal cladding.
(c) Permanent Town
The permanent town will be located at the north end of the tempo-
rary village (see Plate 36) and be arranged around a small lake
for aesthetic purposes.
The permanent town wi 11 consist of permanently constructed bui 1 d-
ings. The-various buildings in the permanent town are listed
below:
-Single family dwellings;
-Multifamily dwellings;
-Hospital;
-School;
-Fire station;
- A town ce1'lter will be constructed and will contain the
following:
• a recreation center
~ a gymnasium and swimming pool
• a shopping center
The concept of building the permanent town at the beginning of the
construction period and using it as part of the temporary village
was considered. This concept was not adopted, since its intended
occupancy and use is a minimum of 10 years away, and the require-
ments and preferences of the potential long-term occupants cannot
be predicted with any degree of accuracy.
(d) Site.Power and Utilities
(i) Power
Electrical power will be required to maintain the camp/
village and construction activities. A temporary 138 kV
transmission line will be constructed along the Denali
access route for use during the construction phase. This
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line will draw power from the Will_ow-Healey intertie which
is currently under construct; on. After the Watana
development is complete and the 345 kV transmission line
supplying power to the Intertie from Watana is complete,
this temporary line will be removed.
During the first two years of construction (1985 and 1986)~
until the 138 kV line ·is complete, the power supply will
come from diesel generators. These generators wi 11 remain
on site after 1987 as standby power supply. The peak
demand during the peak camp population year is estimated at
13 MW for the camp/ vi 11 age and 7 MW for construction
requirements totaling 20 MW of peak demand. The
distribution system in the camp/village and construction area will be 4.16 kV.
Power for th2 permanent town wi 11 be supplied from the
station service system after the power plant is in opera-tion. -
(ii) Water
The water supply system will provide for potable water and
fire protection for the camp/vi 11 age and selected contrac-
tors
1
work areas. The estimated peak· population to be
served will be 4,720 {3,600 in the camp and 1,120 in the village) ..
The principal source of water will be Tsusena Creek, with a
back up system of we 11 s drawing on ground water. The wat;er
will be treated in accordance with the Environmental Pro-
tection Agency 1 s (EPA) primary and secondary requirements ..
A system of pumps and storage reservoirs will provide the
necessary system capacity. The distribution system will be
contained within uti1idors constructed using plywood box
sections integral with the permawalks. The distribution
and location of -major components of the water supply system
are presented in Plate 36. Detai 1 s of the uti 1 idors are presented in Plate 39.
(iii) Waste Water -·----
A waste water co 11 ect ion and treatment system wi 11 serve
the camp/village. One treatment plant will serve the
camp/village using gravity flow lines with lift stations
will be used to collect the waste water from all of the
camp and vi 1 i age faci 1 it i es. The n; n-camp" and "in-
village" collection systems will be run through the utili-
dors so that the call ection system wi 11 be protected from freezing.
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The chemical toilets located around the construction site
will be serviced by sewage trucks, which will discharge
directly into the sewage treatment plant. The sewage
treatment system wi 11 be a bi o 1 ogica 1 system with 1 agoons
designed to meet Alaskan .and EPA standards. The sewaye
p 1 ant wi 11 discharge its treated effluent through a force
main to Deadman Creek. All treated sludge wi 11 be disposed
in a solid waste sanitary landfill. ~
The location of the treatment plant is shown in Plate 37.
The location was selected to avoid unnecessary odors in the
camp as the winds are from the southeast on·ly 4 percent of
the time, which is considered minimal.
{e). Contractor • s Area
The onsite contractors will require office, shop, and general work
areas. Partial space required by the contractors for fabrication
shops, maintenance shops !t storage or warehouses, and work areas,
will be located between the main camp and the main access road.
1.14 -Relict Channel
A relict channel exists on the north bank of the reservoir approxi-
mately 2600 feet upstream of the dam. This channel runs from the
Susitna River gorge to Tsusena Creek, a distance of about 1.5 miles.
The surface elevation of the lowest saddle is approximately 2205, and
depths of up to 454 feet of glacial deposits have been identified.
This channe 1 represents a potentia 1 source of 1 eakage from the Watana
reservoir. Along the buried channel thalweg, the highest, or control-
ling b~drock surface is some 450 feet below reservoir level, while
a 1 ong the shortest 1 eakage path between the reservoir and Tsusena Creek
the highest rock surface is some 250 feet below reservoir level. The
maximum average hydraulic gradient along any flow path in the buried
channel from the edge of pool to Tsusena Creek is approximately 9 per-
cent, while the average gradient is believed to be less than 6 percent.
There is no indication of any existing water-level connection between
the Susitna River and Tsusena Creek. Tsusena Creek at the relict chan-
nel outlet area~ is at least 120 feet above the natural river level.
There are several surface lakes within the channel area, and some arte-
sian water is present in p 1 aces. Zones of permafrost have a 1 so been
identified throughout the channel area.
To preserve the integrity of the. rim of the Watana reservoir and to
control losses due to potential seepage, a number of remedial measures
will be undertaken. These measures are designed to deal with potential
problems which may arise due to settlement of the reservoir rim,
subsurface flows., permafrost and 1 iquefacti on during earthquakes.
(a) Surface F1ows
To eliminate the potenti.al problems associated with settlement and
breaching of a saddle dam allowing surface flows through the
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buried channel area, the maximum operating level of the reservoir
has been set at 2185 feet, leaving a natural saddle width of at
least 1,500 feet of ground above pool level at this elevation. A
freeboard dike with a crest elevation of 2210 will be constructed
to provide protection against extreme reservoir wave levels under
PMF conditions. The shortest distance between the toe of the dike,
and the edge of the Elevation 2185 reservoir pool is at least 450
feet, and under a PMF flood, the static: water level will jusl.:
reach the toe of the dike before the emergency fuse plug washes
out. The freeboard dike wi 11 consist of compacted granular
materia 1 p 1 aced on a prepared foundation from which a 11 surface
soils and organic materials will be remove!d.
{b) Subsurface Flows
The potential for progressive piping and erosion in the area of
discharge into the Tsusena Creek will be controlled by the place-
ment of properly graded granular materials to form a filter bl an-~
ket over any zones of emergence. Further field investigat~ions
will be carried out to fully define critical areas, and only such
areas will be treated. Continuous monitoring of the outlet area
will be undertaken for a 1engthy period after reservoir filling to
ensure that a state of equilibrium is established with respect to
permafrost and seepage gradients in the buried channel area.
If the permeability of the base alluvium is found to be excessive,
a provision will also be made to carry out grouting of the up-
stream alluvium at a natural narrow reach to reduce the total
1 eakage.
(c) Permafrost
Thawing of permafrost will occur, and may have an impact on sub-
surface flows and ground ~ett1ement. Although no specific reme-
dial work is foreseen at this time, flows, ground water elevJtion,
and ground surface elevation in the buried channel area will be
carefully and cant inuously monitored by means of appropriate in-
strumentation systems and any necessary maintenance work carried
out to maintain freeboard and control seepage discharge.
(d) Liquefaction
To guarantee the integrity of the reservoir rim through the.
channe 1 area requires that either:
-There is no potential for a liquefaction slide into the
reservoir, or
. -. If there is such potential, there is a sufficient volume of
stable material at the critical section that even if the up-
stream materials were to slide into the reservoir, the failure
zone cnuld not cut back to the reservoir rim.
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Any r·equirement of remedial treatment wi 11 depend on the 1 ocati on
and extent of critical zo·nes and could range from stabilization by
compaction (vibroflotation), grouting techniques (either cement,
colloidal or chemical grouting), or in the limit, removal of
material, and replacement with compacted nonsusceptable fill ..
Available geotechnical ir.formation indicates that the potential
for liquefaction realistically exists only in the upper 140 feet
of gl a cia 1 deposits in the relict channel. Further geotechnical
studies wi 11 be undertaken to fully . define the extent and charac-
teristics of these materials. Provisions will be made in design
for treatment to cover the worst conditions identified.. These
measures include:
-Densification
Layers within about 100 feet of the surface could be compacted
by vibroflotation techniques to eliminate the risk of liquefac-
tion and provide a stable zone by increasing the relative
density of the in-situ material.
-Stabi 1 izati on
Critical layers at any depth could be grouted, either with ce-
ment· for fine gravels and coarse sands or by chemical grouting
for fine sands and silts.
-Removal
This could range from the replacement of critical material near
the valley slopes with high-quality, processed material, which
would stabilize the toe of a potential slide and so.prevent the
i niti ati on of fai 1 ure that might otherwise cut back and cause
major failures, to the excavation, blending, and replacement of
large voluems of material to provide a stable zone.
The most positive solution to a worst case sce:nario is the re-
placement of the critical zone with material that would not lique-
fy. This would involve, in effect, the rearrangement of the in-
place materials to create an underground dam section constructed
of selected materials founded on the dense till layer beneath the
critical alluvium. Such an operation will requi1r-e the excavation
of a trench up to 135 feet deep with a surface width up to 1,000
feet. Selected materials would be compacted to form a central
stable zone while surplus and unsuitable materials would be placed
on both sides of this centra 1 11 dam" to complete bad< fi 11 i ng to
ground surface. The central zone would be designed to remain
stable in the event that all upstream material did slide into the
reservoir. Such a structure would be about 5,000 feet long, with
a total cut val ume of about 13 mi 11 ion cubic yards, of which 4-1/2
mi 11 ion cubic yards cou 1 d be used in the compacted center zone.
The cost of such work is estimated to be about $100 mi 11 ion.
Although this is considered an unlikely scenario, contingency
allowances VIi 11 be adequate to cover this cost.
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2 -RESERVOIR DATA -WATANA
The Watana reservoir, at normal operating level of 2185 feet (mean sea
level) will be approximately 48 miles long w.Jth a maximum width in the
order of 5 miles. The total water surface area at normal operating
level is 37,800 acres.
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3 -TURBINES AND GENERATORS -WATANA
3.1 -Unit Capacity
The Watana powerhouse wi 11 have six generating units with a nominal
capacity of 170 MW corresponding to the minimum December reservoir
level (elevation 2117) and a corresponding gross head of 662 feet on
the station.
The head on the plant wi 11 vary from 590 feet to approximately 735
feet.
The rated head for the turbine has been established at 680 feet, which
is the weighted average operating head on the station. The rated tur-
bine output is 250,000 hp (186.5 MW) at full gate.
The generator rating has been selected as 190 MVA with a 90 percert
power factor. The generators will be capable of a continuous 15 per-
cent overload allowing a unit output of 196 MW. At maximum reservoir
water level, the turbines will be operated below maximum output to
avoid overloading of the generators.
3. 2 -Turbines
The turbines will be of the vertical sha~t Francis type with steel
spiral casing and a concrete elbow-type draft tube. The draft tube
wi 11 comprise a single water passage without a center pier.
The rated output of the turbines will be 250,000 hp at 680 feet rated
net head. Maximum and minimum heads on the units will be 728 feet and
576 feet respectively. The full gate output of the turbines will be
about 275,000 hp at 728 feet net head and 195,000 hp at 576 feet net
heat. Overgating of the turbines may be possible, providing approxi-
mately 5 percent additional power; however, at high heads the turbine
output will be restricted to avoid overloading the generators. The
best efficiency point of the turbines will be established at the time
of preparation of bid documents for the generating equipment and will
be based on a de.~tailed analysis of the anticipated operating range of
the turbines. For pr·eliminary ·design purposes, the best efficiency
(best gate) output of the units has been asslJTled as 85 percent of the
full gate turbine output.
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The full gate' and best gate efficiencies of the turbines will be about
91 percent and 94 percent respectively at rated head. The efficiency
will be about 0.5 percent lower at maximum head and 1 percent lower at
minimum head.
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3.3 -Generators
(a) Type and Rating .
The six generators in the Watana powerhouse will be of the verti-
cal shaft, overhung type directly connected to the vertical
Francis turbines. The arrangement of the units is shown in Plates
27 and 28 and the single 1 ine diagram is shown in Plate 32.
The optimum arrangement at Watana wi 11 consist of two generators
per transformer bank, with each transformer bank comprising three
single-phase transformers. The generators will be connected to
the transformers by isolated phase bus through generator circuit
breakers directly connected to the isolated phase bus ducts.
Each generator will be provided with a high initial response
static excitation system. The units will be controlled from the W~tana surface control room, with 1 ocal control facility also pro-
vided at the powerhouse floor. Th~ units will be designed for
black st.~rt operation.
The generators are rated as fo 11 ows:
Rated Capacity:
Rated Power:
Rated Voltage:
Synchronous Speed:
Inertia Constant:
Transient Reactance:
Short Circuit Ratio:
Efficiency at Full Load:
190 MVA, 0. 9 power factor
170 MW
15 kV, 3 phase, 60 Hertz
225 rpm
3. 5 MW -sec/MVA o
28 percent (maximum)
1.1 (minimum)
98 percent (minimum)
The generators will be of the air-cooled type, with water-to-air
heat exchangers located on the stator periphery. The ratings
given above are for a temperature rise of the stator and rotor
windings not exceedi,ng 60°C with cooling air at 40°C.
The generators will be capable of delivering 115 percent of rated
MVA continuously ( 195.5 MW) at a voltage of +5 percent without
exceeding 80°C temperature rise in accordance with ANSI Standard
C50.10.
The generators ·will be capable of contirwous operation as synch-
ronous condensers when the turbine is unwatered, with an under-
excited reactive power rating of 140 MVAR and an overexcited rat-
ing of 110 MVAR. Each generator will be capable of energizing the
transmission system without risk of self-excitation.
The design. data of the generators stated above should be reviewed
during the detailed design stage for overall economi~: and techni-
cal design and performance requirements of the power plant and the
power system.
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(b)
The design data of the generators stated above should be
reviewed during the detai 1 ed design stage for overall eco-
nomic and technical design and performance requirements of
the power plant and the power system.
Unit Dimensions
Approximate dimensions and weights of the principal parts
of the generator are given below:
Stator pit di arneter:
Rotor diameter:
Rotor length (without shaft):
Rotor weight:
Tot a 1_ weight:
36 feet
22 feet
· 7 feet
385 tons
740 tons
It should be noted that these are approximate figures and
they wi 11 vary between manufacturers.
(c) Generator Excitation System
The generator wi 11 be provided with a high initial response
type static excitation system supplied with rectified exci-
tation power from transformers connected directly to the
generator terminals. The excitation system will be capable
of supplying 200 percent of rated excitation field (ceiling
voltage) with a generator terminal voltage of 70 p~rcent.
The power rectifiers will have a one-third spare capacity
to maintain generation even during failure of a complete
rectifier module.
The excitation system will be equipped with a fully static
voltage regulating system maintaining output from 30 per-
cent to 115 percent, within +0. 5 percent accuracy of the
voltage setting. Manual control will be possible at the
excitation board located on the powerhouse floor, although
the unit will nonnally be under remote control.
3.4 -Governor System
. The governor system which control the generating unit will include a
governor actuator and a governor p~m~p i ng unit . A sing 1 e system wi 11
be provided for each unit. The governor actuator will be the electric
hydraulic type and wi 11 be connected to the computerized station con-..
trol system.
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4 -TRANSMISSION LINES -FROM WATANA TO INTERTIE AND
INTERITE TO ANCHORAGE/FAIRBANKS
4.1 -Transmission Requirements
The project transmission facilities are required to provide a power
delivery system from the Susitna River Basin generating plants to the
major load centers in Anchorage and Fairbanks. This system will be
comprised of transmission lines, substations, a dispatch center, and
m~ans of communications. The selected system will ensure a reliable
and economic electrical power system, with components rated to allow a.
smooth transition through early project stages to the ultimate de-
veloped potential. The design is based on delivery of total power out-
put of Susitna to two substations at Anchorage and one at Fairbanks.
4.2 -Description of Facilities
The project transmission system will ultimately comprise the following
components:
Line Section
Watana to Dev i 1 ·Canyon
Devi 1 Canyon to Fa·irbanks
Devil Canyon to Willow
Willow to Knik Arm
Knik Arm Crossing
Knik Arm to University
Substation
Le gjh
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27
189
90
38
4
18
Number of
Circuits
• c.
3
3
3
2
Number and S i ze
Volta~e of Conductors
(kV -(kcmil)
345 2 by 954
345 2 by 954
345 2 by 954
345 2 by 954
345 Submarine cable
345 2 by 1351
Substations for this system will be located at each power site and also
at Ester (Fairbanks), Willow, Knik Arm (east shore), and University
(Anchorage). The Ester sub stat ion wi 11 provide a connection of Susitna
power to the Golden \Ialley Ele.ctric Association (GVEA) system and the
University substation to the Chugach Electric Association {CEA) and
Anchorage Municipal Light and Power (AMLP) systems. The segment of the
system between Willow and Healy will incorporate and include the inter-
tie which is curr.ently being constructed as a single 1 ine to be
operated initially at 138 kV and subsequently upgraded to 345 kV.
The selected route is shown in Figures 1 through 14.. [To be included
later].
The required right-of-\-vay will vary from 400 feet for 3 lines to 700
feet for 5 lines. The corridor and route selection process was based
on eva1uation of technical~ economic, and environental criteria and a
number of alternatives. Particular emphasis was placed on satisfying
regulatory and permit requirements., aesthetics and avo·idance of
deve 1 oped areas.
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The selected tower design consists of a hinged-guyed, two-legged steel
X-tower, similar to that used .for the intertie. Design features of
these towers include hinged connections between the leg members and
foundations and longitudinal guy systems which provide flexibility and
st.ability. These are important considerations in the unique soil and
climate conditions in this area of Alaska. The arrangement will result
in relatively smaller loads on the foundations. The recommended types
of foundations are the rock anchor and the pile foundation. The se-
lected design is considered to be, a sound compromise of real ibil ity,
durability, economy, and aesthetics.
4. 3 -Construction Sta~ing .
The initial development of Wataoa will require staged development of
transmission facilities to Fairbanks and Anchorage. The first stage is
shown in solid lines and includes the following:
Substations
Watana
Devil Canyon
Willow
Knik Arm
University (Anchorage)
Ester {Fairbanks)
Number of
Line Section Circuits
Wat an a to Dev i 1 Canyon 2
Devil Canyon to Willow 2
Willow to Kwik Arm 2
Knik Arm Crossing 2
Knik Arm to University 2
Devil Canyon to Fairbanks 2
The transmission will consist of two circuits from Watana to the lo,ad
centers. The conductor for the sections from Watana to Knik Arm, ~nd
Watana to Fairbanks will consist of bundled 2 x 954 kcmil, ACSR. The
section between Knik Arm and University wi 11 employ bundled 2 x 1351
kcmi 1 , ACSR. The submarine cab 1 e crossing wi 11 consist of two ctr-
cuits. The cable will be single conductor, 3.45 kV self-contained oil-
filled. For project purposes, the cable size will be 500 mm2. A
size of up to 1500 mm2 may be installed if duty requirements are
increased. For reliability, a spare cable wil~ be included on a
standby basis ..
The Matnuska Electric Association will be serviced from the Willow and
Kni k Arm sub stat ions vi a step down transformers to suit the local
voltage. Chugach Electric Association, Anchorage Municipal Light and
Power and Golden Valley Electric Association will be serviced through
the University substation in Anchorage and Ester substation at
Fairbanks.
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5 -APPURTENANT MECHANICAL AND ELECTRICAL EQUIPMENT -WATANA
5.1 -Miscellaneous Mechanical Equipment
(a) ~owerhouse Cranes
Two overhead traveling bridge type powerhouse cranes wi 11 be
installed in the powerhouse. The cranes wil1 be used for:
-Installation of turbines, generators, and other powerhouse
equipment; and
-Subsequent dismantling and reassembly of equipment during main-
tenance overhauls.
Each crane will have a main and auxiliary hoist. The combined
capacity of the main hoist for both cranes will be sufficient for
the heaviest equipment 1 ift, which wi 11 be the generator rotor~
plus an equalizing beam. A crane capacity of 205 tons has been
established. The auxiliary hoist capacity will be about 25 tons.
(b) Draft Tube Gates
Draft tube gates will be provided to permit dewatering of the tur-
bine water passages for inspection and maintenance of the tur-
bines. The draft tube gate openings (one opening per unit) will
be located in the surge chamber. The gates will be of the bulk-
head type, installed under balanced head conditions using the.
surge chamber crane. Four sets of gates have been assumed for the
six units, with each gate 20 feet wide by 10 feet high.
(c) Surge Chamber Gate Crane
A crane will be installed in the surge chamber for installation
and removal of the draft tube gates as well as the tailrace tunnel
intake stoplogs. The crane will either be a monorail (or twin
monorail) crane, a top running crane, or a gantry crane. The
crane wi 11 be about 30 tons in capacity, and will have a two point
1 ift.
· (d) Miscellaneous Cranes and Hoists
In. addition to the powerhouse cranes and surge chamber gate crane_,
the following cranes and hoists will be provided in the power
plant:
- A 5-ton monorail hoist in the transformer gallery for trans-
former maintenance;
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-A 4-tan monorail hoist in the circuit breaker gallery for han•a<~'·
ling the main circuit breakers;
-Small overhead jib or A-frame type hoists in the machine shop
for handling material; and
-A-frame or monorail hoists for handling miscellaneous small
equipment in the powerhouse.
( ~~) E 1 ev ators
Access and service elevators wi 11 be provided for the power plant
as follows:
-An access elevator from control buildings to powerhouse;
- A service elevator in the powerhouse service bay; and
-Inspection hoists in the cab 1 e shafts.
(f) Power Plant Mechanical Service Systems
The mechanical service systems for the power plant can be grouped
into six major categories:
( i) Station Water Systems
The station water systems will include the water intake~
cooling water systems, turbine seal water systems, and
domestic water systems.. The water intakes wi 11 supply
water for the various station water systems in ada·ition to
fire protection water.
(ii) Fire Protection System
The power plant fire protection system wi 11 consist of a
fire protection water system with fire hose stations
located throughout the powerhouse and transformer gallery;
sprinkler systems for the generators, transformers, and t~e
oil rooms; and portable fire extinguishers 1ocated in stra-
tegic areas of the powerhouse and transfonner gallery.
Fire hose stations will be provided on all floors of me
powerhouse, in the transformer gallery, and in the bus
tunnels.
(iii) Compressed Air Systems
Compressed air wi 11 be required in the powerhouse for the
following:
-Service air;
-Instrt.ment air;
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-Generator brakes;
-Draft tube water level depression;
-Air blast circuit breakers; and
-Governor accumulator tanks.
For the preliminary design, two compressed air systems have
been assumed: a 100-ps i g air system for service ah··, brake
air, and air for draft tube water level depression; and a
1, 000-psig hiHh-pressure air system for governor air and
circuit breaker air. For detailed p1 ant design, ·a separate
governor air system and circuit-breaker air system may be
·provided.
(iv) Oil Storage and ~andling
Facilities will be provided for replacing oil in the trans-
formers and for topping-up or replacing oil in the turbine
and generator bearings and the governor pumping system.
For preliminary design purposes, two oil rooms have been
included, one in the transformer gallery and one in the
powerhouse service bay.
(v) Drainage and Dewatering Systems
The drainage and dewatering systems will consist of:
-A unit dew~tering and filling system;
- A clear water discharge system; and
- A sanitary drainage system.
The. unit dewatering and filling systems will consist of two
sumps each with two . dewatering~ pumps and associ a ted pi ping
and valves from each of the units. To prevent station
flooding, the sump wi 11 be designed to withstand maximun
tailwater pressure. A valved draft tube drain line will
connect to a dewatering header running along the dewatering
gallery. The spiral case will be drained by a valved line
connecting the spiral case to the draft tube. Suitable
provisions wi 11 be necessary to insure that the spiral case
drain valve is not open when the. spiral case is pressurized
to headwater 1 evel. The dewatering pump discharge 1 ine
wi 11 discharge water into the surge chamber. The general
procedure for dewatering a unit wi 11 be to close the intake
gate, drain the penstock to tailwater level through ·the
unit, then install the draft tube gates open the draft tube
and_ spiral case drains to dewater the unit. Unless the
drainage gallery is bel ow the bottom of the draft tube
elbow, it will not be possible to completely dewater the
draft tube through the dewatering header. If necessary,
the remainder of the draft tube can be unwatered using a
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submersible pump lowered through the draft tube access
door. Unit filling to tailwater level will be accomplished
from the surge chamber through the dewatering pump dis-
charge line (with a bypass around the pumps) and then
through the draft tube and spiral case drain 1 ines. Ai-
ternatively, the unit can be filled to tailwater level
through the draft tube drain 1 ine from an adjacent unit;>
Filling the unit to headwater pressure will be accomplished
by ncracki ng 11 the intake gate and raising it about 2 to 4
inches.
(vi) Hel!!) ng, Venti 1 at ion, and Coo 1 i ng
The heating, ventilation, and cooling system for the under-
ground power plant will be designed primarily to maintain
suitable temperatures for equipment operation and to pro-
vide a safe and comfortab 1 e atmosphere for operating and
maintenance personnel.
The power plant will be located in mass rock which has a
constant year around temperature of about 40°F. Consider-
ing heat given off from ·the generators and other equipment,
the primary requirement will be for air cooling. Ini-
tially, some heating will be required to offset the heat
loss to the rock, but after the first few years of opera-
tion an equi 1 ibri ll1l wi 11 be reached with a powerhouse rock
surfac~ temperature of about 60 to 70°F.
(g) Surface Facilities Mechanical Service Systems
The mechanical services at the. control building on the surface
will include:
-A h_eating, ventilation, and air conditioning system for the con-
trol room;
-Domestic water and washroom facilities; and
- A ha 1 on type fire protection system for the contra 1 room.
Domestic water wi 11 be supplied from the powerhouse domestic ·water
system, with pumps located in the powerhouse and piping up through
the access shaft. Sanitary drainage from the control building
wi 11 drain to the sewage treatment plant in the powerhouse through
piping in the access tunnel.
The standby generator building will have the following services:
-A heating and ventilation system;
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-A fuel· oil system with buried fuel oil storage tanks outside the
building, and transfer pumps and a day tank within the building;
~d .
- A fire protection system of the carbon dioxide or hal on type.
(h) Machine Shop F aci 1 it i e.§_
A machine shop and tao 1 room wi 11 · be 1 oc atea in the powerhouse
service bay area with sufficient equipment to take care of a11
normal maintenance work at the plant, as well as machine shop \\Ork
for the larger components at Devil Canyon.
5.2 -Accessory Electrical Equipment
The accessory electrical equipment described in this section includes
the following:
• ~1a in generator step-up 15/345 k V transformer~s;
. Isolated phase bus connecting the generator and transfonners;
. Generator circuit breakers;
. 345 kV oil-filled cables from the transformer ter:11inals to the
switchyard;
. Control systems of the entire hydro plant complex; and
. Station service auxiliary AC and DC systems.
Other equipment and systems described include grounding, 1 ighting sys-
tem, and communications.
The main equipment and connections in the power plant are shown in the
single line diagram, Plate 32. The arrangement of equipment in the
powerhouse, transformer gallery, and cable shafts is shown on Plates 2.7
through 29. -
(a) Transformers and H. V. Connections
Nine single-phase transformers and one spare transfonner will be
located in the transfonner gallery. Each bank of three single-
phase transformers will be connected to two generators through
generator circuit breakers by isolated phase bus located in indi~
vidual bus tunnels. The HV terminals of the transformer will be
connected to the 345 kV switchyard by 345 kV single-phase oil-
filled cable installed in 700-footlong vertical shafts. 1Jlere
wiJl be two sets of~ three single-phase 345 kV. oil-filled cables
installed in eacTi~cable shaft. One set will be maintained as a
spare three phase cable circuit in the second cable shaft. These
cab 1 e shafts wi 11 a 1 so contain the contra 1 and power cab 1 es
between the powerhouse and the surface contra l room, as we 11 as
em~rgency p~·wer cables from the diesel generators at the surface
to the underground facilities.
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(b) Main Transformers
(c)
(d)
The nine single-phase transformers (three tr3nsformers per group
of two generators) and one spare. transfonner, wi 11 be of the t\\U
winding, oil-immersed, forced-oil water-cooled (FOW) type, with
rating and electric characteristics as follows:
145 MVA Rated capacity:
High voltage winding: 345 I 3 k V, Grounded Y
Basic insul·ation level (BIL)
of H.V. winding:
Low voltage winding:
Transformer impedance:
1300 kV
15 kV, Delta
15 percent
The temperature rise above air anbient temperature of 40oC is 55oC
for the windings for continuous operation at the rated kVA.
Fire walls wi~ 1 separate each single•phase transformer. Each
transformer will be provided with fog-spray water fire protection
equipment, automatically operated from heat detectors iocated on
the. transformer.
Generator Isolated Phase Bus
The iso 1 ated phase bus main connections will be located between
the generator, generator circuit breaker, and the transformer.
Tap-off connections wi 11 be made to the surge protection and
potential transformer cubicle, excitation transformers, and
station service transformers. Bus duct ratings are as follows:
Generator Transformer
Connection Connection
Rated current, amps 9, 000
Short circuit current
momentary, amps 240,000
Short circuit current,
sjfllmetrical , amps 150,000
Basic insulation level, kV (BIL) 150
18,000
240,000
150,000
150
The bus conductors will be designed for a temperature rise of 65~C
above 40°C ambient temperature.
Generator Circuit Breakers
The generator circuit breakers will be of the enclosed air circuit
breaker design suitable for mounting in line with the generator
isolated phase bus d.ucts. They are rated as follows:
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(f)
Rated Current: 9,000 Amps
Voltage: 23 k V c 1 ass, 3-phase, 60 Hertz
Breaking capacity,
s.}1Tlme..,rical, amps 150,000
The short circuit rating is tent at iv e· and wi 11 depend on deta i 1 ed
analysis in the design stage ..
345 kV 0 i 1-F i 11 ed Cab 1 e
The recommended 345 kV connection is a 345 kV oil-filled cable
system between the high voltage terminals of the transformer and
the surface switchyard. The cable will be installed in a vertical
cable shaft. Cables from two transformers will be installed in a
sing 1 e cab 1 e shaft.
The cable will be rated for a continuous maximun current of 800
amps .at 345 kV +5 percent. The maximum conductor temperature at
the maximun ratmg will be 70°C over a maximum cmbient of 35°C.
This rating will correspond to 115 percent of the generator over-
load rating. The normal operating rating of the cable will be 87
percent, with a corresponding lower conductor temperature which
will improve the overall performance and lower cable aging over
its project operating life. Depending on ·the anbient air tempera-
ture, a further overload anergency rating of about 10 to 20 per-
cent will be available during winter conditions.
The cables will be of single-core construction with oil flo¥1
through a central oil duct within the coppe!r conductor. Cables
will have an aluminum sheath and PVC oversheath. No cable joint-
i.ng will be required for the 700 to 800 feet length cable insta.1-
lation.
Contra 1 Systems
( i) Genera 1
A Susitna Area Control Center wi11 be located at Watana to
control both the Watana and the Devil Canyon power plants
as shown in Plate 34. TI1e contra 1 center wi 11 be 1 inked
through the supervisory system to the Central Dispatch
Centro 1 Center at Wi 11 ow as descr·ibed in Exhibit B,
Section (c) {3).
The supervisory control of the entire Alaska Railbelt sys-
tem wi 11 be done at the Central Di spa·~ch Center at Willow.
A high level of control automation wi·th the aid of digital
computers wi 11 be sought but not a complete computerized
direct digital control of the Watana and Devil Canyon power
plants. Independent operator controlled local-manual and
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local-auto operations will still be possible at Watana and
Devil Canyon power plants for testing/commissioning or dur-
ing energencies. The control system wi 11 be designed to
perform the following functions at both power plants:
-Start/stop and loading of units by operator;
-Load-frequency control of units;
-Reservoir/water flow control;
-Continuous monitoring and data logging;
-A1 arm ann unci at ion; and
-Man-machine communication through visual display units
(VDU) and console.
In addition, the computer system will be capable of re-
trieval of technical data, design criteria, equipment char-
acteristics and operating limitations, schematic diagrams,
and operating/ maintenance records of the unit.
The Susitna Area Control Center wi 11 be capable of com-
pletely independent control of the Central Dispatch Center
in case of system emergencies. Similarly it will be pos-
sible to operate the Susitna units in an energency situa-
tion from the Central Dispatch Center, although this should
be an unlikely operation considering the size, complexity,
and impact of the Susi tn a generati.ng plants on the s.ystem.
The Watana and Devil" Canyon plants will be capable of
"black startu operation in the event of a complet~ black
out or call apse of the power system. The control systems
of the two plants and the Susitna Area Control Center com-
plex will be supplied by a non-interruptible power supply.
(ii) Unit Control System
The unit control system wi 11 permit the operator to initi-
ate an entire sequence of actions by pushing onf~ button at
the control console, provided all pr·el iminary p,l ant condi-
tions have been first checked by the operator !J and system
security and unit commitment have been c1eared through the
central dispatch control supervisor. Unit control will be
designed to:
-Start a unit and synchronize it with the system;
-Load the un i t ;
-Stop a unit;
-Operate a unit as spinning reserve (runner in air with
water blown down in turbine and draft tube); and
-Operate as a synchronous condenser ( r·unner in air as
ab.o~e).
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(iii) Computer-Aided Control System
{iv)
( v)
The computer-aided control system at the Susitna Area Con-
trol Genter at Watana will provide for the following:
-Data acquisition and mon i to~ing of unit ( MW, MVAR, speed,
gate position, temperaturest\ etc.);
-Data acquisition and monitoring of reservoir headwater
and tailwater levels;
-Data acquisition and monitoring of electrical system
voltage and frequency;
-Load-frequency control;
-Unit start/stop control;
-Unit loading;
-Plant operation alarm and trip conditions (audible and
visual alarm on control board, full alarm details on VDU
on denand);
-General visual plant operation status on VDU and on giant
wall mimic diagram;
-Data logging, plant operation records;
-Plant abnormal operation or disturbance automatic recot'd-
ing; and
-Water management (reservoir control).
The block diagram of the computer-aided control system is
shown in Plate 34 ..
Locai Control and Relay Boards
Local boards wi 11 be provided at the powerhouse fl oar
equipped with local controls, alarms, and indications for
all unit control functions. These boards will be located
near each unit and will be utilized mainly during testing,
commissioning, and maintenance of the turbines and gener-
ators. It wi 11 also be uti 1 i zed as needed during anergen-
cies if there is a total fQil ure of the remote or computer-
aided contra 1 systems ..
:.. ::1d-F requency C ontro 1
~~----~~-------
The !~ad-frequency system will provide remote control of
the output of the genera tor at Watan a and Dev i 1 Canyon from
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(g)
the central dispatch control center through the supervisory
and computer-aided control system at Watana. The basic
method of 1 oad frequency contra 1 wi 11 use the plant error
(differential) signals from the load dispatch center and
will allocate these errors to the power plant generators
automatically thr.ough speed-level motors. Provision wlll
be made in the control system for the more advanced scheme
of a closed-loop control system with digital control to
control generator power.
The control system wi 11 -be designed to take into account
the digital nature of the controller-timed pulses as well
as the inherent time de1 ays caused by the speed-level motor
run-up and turbine-generator time-constants4
Statio, Service Auxiliary AC and OC Systems
(i) Auxi \ iary AC System .. _. -=--
The station· service system will be designed to achieve a
reliable and economic distribution system for the power
plant and switchyard, in 0rder to satisfy the 'following
requirements:
-Station service power at 480 volts will be obtained from
two 2, 000 k VA aux i 1 i ary transformers connected directly
to the generator circuit breaker outgoing leads of Units
1 and. 3;
-Surface auxiliary power at 34.5 kV will be supplied by
two separate 7. 5/10 MVA transformers connected to the
generator leads of Units 1 and 3;
-Station service power wi 11 be maintained even when all
the units are shut down and the generator circuit
breakers are open;
-100 percent standby transformer capacity will be avail-
able; ·
- A spa.re auxiliary transformer will be maintained, con-
nected to Unit 5; and
-"Black start11 capability will be provided for the power
plant in the event of total failure of the auxiliary
supply system, 500 kW emergency diesel generators wi11 be
automatically started up to supply the power plant and
switchyard with auxiliary power to the essential services
to enable startup of the generators.
The main ac auxiliary switchboard wi 11 be provided with two
bus sections separated by bus-.tie circuit breakers. Under
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(ii)
normal operating conditions, the station-service load is
divided and connected to each of the two end incoming
transformers. In the event of failure of one end supply~
the tie breakers \'lill close automatically. If both end
supplies fail, the emergency diesel generator will be auto-
matically connected to the station service bus.
Each unit will be provided with a unit auxiliary board sup-
plied by separate feeders from the two bus section feeder
from the two bus section of the main switchborad inter-
locked to prevent parallel operation. Separate ac switch-
boards will furnish the auxiliary power to essential and
general services in the power plant.
The unit auxiliary board will supply the auxiliaries neces-
sary for starting, running, and stopping the generating
unit. These supplies will include those to the governor
and oi 1 pressure system, bearing oi 1 pumps, cooling pumps
and fans, generator circuit breaker, excitation system, and
miscellaneous pumps and devices connected with unit opera-
tion.
The 34.5 kV sypply to the ·surface facilities will be dis-
tributed from a 34.5 kW switchboard located in the surface
control and administration building. Power supplies to the
switchyard, power intake, and spillway as well as the
lighting systems for the access roads and tunnels will be
obtained from the 34.5 kV switchboard.
The two 2000 kVA, 15000/480 volt stations service trans-
formers and the spare transformer will be of the 3-phase,
dry-type·, sealed gas-filled design. lrte two 7.5/10 MVA~
15/34.5 kV transformers will be of the 3-phase nil,..immersed
OA/FA type.
Emergency diesel generators, each rated 500 kW, will sep-
arately supply the 480 volt and 34.5 kV auxiliary switch-
boards during anergencieso Both diesel generators will be
located in t~e surface cont\"ol building.
An uninteruptible high secv.rity power supply will be pro-
vided for the computer contra 1 system I'
DC Auxiliary Station Service System -.
The de auxiliary system wi 11 sui.,">lY the protective relay-
ing, supervisory, alarm, contt c/:, tripping and indication
circuit in the power plant. The generator excitation sys-
tem wi 11 be ·started with "fl ashing 11 power from the de bat-
tery.. It will also supply the .energency 1 ighting system at
critical plant locations~
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(h) Grounding System
The power plant grounding system will consist of one mat under the
power plants one mat under the transformer gallery, risers, and
connection ground wires-. Grounding grids will also be included in
each powerhoust floor.
{i) Lighting System
The lighting system in the powerhouse will be supplied from 480/
208-120 volts 1 ighting transformers connected to the general ac
auxiliary station service system. An emergency 1 ighting system
wi 11 be provided at the power plant and at the control room at a 11
critical operating locations.
(j) Communications
The power plant will be furnished with an internal co~nunications
system, including an automatic telephone switchboard systen1e A
communication system will be provided at ~)l powerhouse floors and
galleries, transformer gallery, access tunnels and cable shafts,
and structures at the power intake, draft tube gate area, main
spillway, dam, outlet facilities~ and emergency release facil-
ities.
5.3 -Switchyard Structures and Eguipmen~
(a) Single Line Oiagr,~
A 11 breaker-and-a-half11 single 1 ine arrangement will be provided
for re 1 i abi 1 ity and security of the power system. Plate 33 s hO\'lS
the details of the switchyard single line diagram.
" (o) Switchyard Equipment
1:
The number of 345 k V circuit breakers is determined by the number
of elements to be switched such as lines or in-feeds from the
powerhouse. Each breaker wi 11 have two disconnect switches to
allow safe .maintenance.
The auxiliary power for the switchyard will be derived from the
generator bus via a 15 -34.5 kV transformer and 34 .. 5 kV cable.
The voltage wi 11 then be stepped down to 480 V for use in the
switchyard.
(c) Switchyard Structures and Layout
The switchyard layout wi 11 be. based on ct conventional outdoor type
design. The design adopted for this project will provide a two
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level bus arrangement. This design is commonly known as a low
station profi ·1 e.
The two l:evel bus arranganent is desirable because it is less
prone to extensive damage in case of an earthquake. It is also
easier to maintain low level busses.
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6 -PROJECT LANDS
The purpose of this section is to provide an overview of the results
obtained through the identification of the general land ownership
status within the Upper Susitna River aasin and the Anchorage-Fairbanks
Intertie Corridor.
6.1 -~ignificant ~and Policies Affecting the Study Area·
The Federal government remains the 1 argest 1 and owner in Alaska. How-
ever, this domination of ownership has been eroded with the passage of
the Alaska Statehood Act in 1959 and the Alaska Native Claims Settle-
ment Act in 1971. These Acts have placed in question the ultimate 1 and
ownership patterns of the State with competition for the land divided
among the Federal government, tne State of Alaska, and private Native
regional and vi11 age corporations •
With the enactment of the Statehood Act, the State of Alaska became
entitled to a total of 104.5 million ·acres. Section 6(b) of the Act
included 102.5 million acres of gener·al grant lands tote used at the
discretion of the State. In addition, certain federal lands were to be
held in trust for both public schools and for the University of Alaska.
Pub 1 ic Law 84-830, passed in 1956, provided for one mi 11 ion acres of
mentai health grant lands.
In 1978, the State legislature passed a law designed to convert the 1.2
million acres of land held as special trusts for funding public
schools, mental health programs, and the University of Alaska into gen-
eral grant 1 ands to be treated in . the ·same manner as other State-held
1 and. The plan wa~ to replace the 1 and with an annua 1 income, a per-
centage of the tot~.\1 receipts from the managenent of State . ·1 and~ in-
cluding oil royaltie:. However, the University of Alaska exe·rcised its
opt ion and t,urned down this trust and retains managenent over· the 1 ands
it holds title to.
The State of Alaska has granted 1 and entitl enents to the organized
Boroughs and Municipalities. As a result of this entitl~oent, both the
Matanuska-Susitna and North Star Boroughs have extensive land holdings ..
The Municipality of Anchorage has received it entitleJnent, which is
considerably less than that received by the Boroughs. ·
In response to increasing public pressure and changing laws, the State
1 egisl ature passed HB66 in 1979, charging the Department of Natural
Resources with the responsibi1 ity of disposing 100,000 acres of land
annually to private ownersh)'p. This land is disposed through four
methods: direct sale, hbmesites, remote parcels, and agricultural
rights. It is apparent from recent discussions between the Alaska
Power Authority and the State Division of Lands that the State Division
of Lands is severely encumbered by its requirement to annually dispose
of 100,000 acres of land to the public. ConsequentJy, necessary
regional and site considerations, e.g. proposed Intertie Corridor,
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relating to the disposal of these lands are frequently omitted from the
State's land disposal selection process.
With the passage of the Alaska Native Claims Settlanent Act (ANCSA) in
1971, the State of Alaska was no longer the sole entity selecting fed-
eral lands. Under the Act~ private Native regional and villaga corpor-
ations were entitled to select iands from the Federal government hold-
ings and from those 1 ands previously selected, but not patented to the
State of Alaska. To date, neither the State nor the Native Corpora-
tions has received its full entitlement under the Statehood Act and the
Alaska Native Claims Settlement Act.
6. 2 -Present Land Ownership Trends
(a) Anchorage-Will()_!!
This section contains a complex mixture of land ownership \vith the
extensive private ownership interspersed with large blocks of
State and Borough 1 ands. The State has reserved several areas for
public recreational use (Nancy Lake State Recreation area, Goose
Bay and Susitna Flats Game Refuge, and Chugach State Park). The
only large State land disposal within this area is the ?t.
MacKenzie Agricultural Project scheduled for spring 1981. The
holdings by the Federal government are dominated by military
reserves in the Anchorage area. '
( b) W i 11 ow-T a 1 k eet na
This area is characterized by numerous private holdings along the
Parks Highway. Large blocks of State, Native, and Borough 1 ands
dominate the remainder of the 1 and in this area. Numerous St.ate
1 and disposals have taken place and are proje~ted for this area_
(c) Talkeetna-Fairbanks
This section represe.nts an area of large blocks of State owr-;n:ed
land. Numerous private holdings are concentrated in scatter'~d
communities located along the Parks Highway. The most notable of
these are Cantwell, Healy, Clear, and Nenana. Ca.ntwell and Nenana
are both surrounded by 1 arge b1 ocks of Native 1 ands. Both the
Denali State Park and the Mt. McKinley National Park are located
in this section.
(d) Upper Susitna River Basin
The 1 and status in this area is relatively simple, due to the
1 arge amount of pub 1 ic 1 and managed by the Bureau of Land Manage-
ment. There are large blocks of private Native Village Corpora-
tion lands along th Susitna River. Other private holdings consist
of widely scattered remote parcels. The State has selected much
of the Federal 1 and in this area and is expected to receive
patent.
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6.3 -Land Status Methodology
The following sources were used to identify the ownership and other
interests wi_thin the Anchorage-Fairbanks Transmission Line Corridor and
Upper Sus i tn a Riv-er Basin :
Alaska Department of Natural Resources
Alaska Department of Transportation ·
Bureau of Land Managenent
Cook Inlet Region, Incs, Land Records Matanus~,a-Susitna Borough Tax Assessor Records
MunicipaJity of Ancr.orage Tax Assessor Records
North Star Borough Land Managenent Records
Within all areas researched, four general categories of 1 and own~rshi p;
i .. e., Federal, State 7 Borough, and Private, are depicted at a scale of
1 inch=l mile (1:63,360). However, please note that the land status
with·in the corridor continues to be quite fluid and subject to frequent
change. The most immediate change comes with the passage of the D-2
legislation. For exanple, those areas shown to be under a 204-C With-
drawal c1 assification wi 11 be incorporated into the National Park Sys-
temo While the boundaries of the 204-C Withdrawal areas may vary
slightly from that shown on the maps, they will not vary to a degree
that would significantly impact the overall land status p.attern.
Several areas and designations may cause some confusion and are cl ari-
fied as follows:
(a)
(b)
(c)
(d)
(e)
(f)
(g)
Private Land ciassification do not distinguish between individual
landowners (e.g. native corporations) or numerous landowners (e.g.
subdivisions).
Federal Lands in the vicinity of Healy have been leased by the
Alaska Railroad to private citizens.
Cantwell Townsite contains a mixed ownership pattern with Federal
Land interspetsed among numerous private parcels.
Native Allotments are designated as Federal Lands but may become
private as claims are approved.
Mineral Leases or Mining Claims are not shown on either State or
Feder a 1 Lands •
Leased parcels of five or 1ess acres are classified private, as
they can be expected to receive patent from the State in the near
future.
Lands in the Upper Susitna River Basin have previously been with-
drawn for the power project under several PLO's (PLO 5654, 2961,
and 3458).
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(h) Certain lands in the Susitna River area are shown as State Selec-
tion suspended. These 1 ands are also selected~ by the Village
Corporations and CIRI. The selections will likely be. approved and
transferred to the State if the August 31, 1976 agreement between
the Department of Interior, CIRI, and the Village Corporations is
implemented. It is also a matter involving litigation.
( i) It should be noted that University 1 ands are managed by the Board
of Regents and not under control by the Department of Natural
Resources ..
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7 -PROJECT STRUCTURES -DEVIL CANYON DEVELOPMENT
This section describes the various components of the Devil Canyon de-
velopment, including diversion~ facilities, emergency release facil i-
ties, main darn, primary outlet facilities, reservoir, main and emer-
gency spillway, saddle dam, the power intake, penstocks, and the power-
house complex, including turbines, generators, mechanical and electri-
cal equipment, switchyard structures, and equipment and project lands.
A summary of project parameters is in Table A.l.
A description of permanent and .temporary access and support facilities
is also included.
7.1 -General Arrangement
The Devil Canyon reservoir and surrounding area is shown on Plate 40 ..
The site layout in relation to main access facilities and camp facili-
ties is shown on Plate 72. A more detailed arrangement of the various
site structures is presented in Plate 41.
The Devil Canyon dam will form a reservoir approximateiy 26 miles long
with a surface area of 7, 800 acres and a gross storage capacity of
1,100,000 acre-feet at Elevation 1455, the normal maximum operating
level. The operating level of the Devil Canyon reservoir is controlled
by the tailwater level of the upstream Watana development.. The maximum
water surface elevation during flood conditions will be 1465a3. The
minimum operating level of the reservoir will be 1405, providing a live
storage during normal operation of 200,000 acre-feet.
The dam will be a thin arch concrete structure with a crest elevation
of 1463 and maximum height of 646 feet. The dam will be supported by
mass concrete thrust blocks on each abutment. On the south bank, the
lower bedrock surface will require the construction of a substantial
thrust block. Adjacent to this thrust block, an earth-and rockf11l
saddle dam will provide closure to the south bank. The saddle dam wi11
be a centra 1 core type genet" ally simi 1 ar in ercss section to the Watana
dam. The dam will have a nominal crest elevation of 1469 with an addi-
tional 3 feet of overbuild for potential seismic settlenent. The maxi-
mum height above foundation level of the dam is approximately 245
feet.
During construction, the river will be diverted by means of a single
30-foot-diameter concrete-lined diversion tunnel on the south bank of
the river.
A power intake, located on the north bank, will comprise an approa~h
channel excavated in rock leading to a reinforced concrete gate struc'-
ture. From the intake structure four 20-foot-di ameter concrete-1 ined
penstock tunnels will lead to an underground powerhouse complex housing
four 150 MW units with Francis· turbines semi-umbre11~ type generators
each rated at 180 MVA. Access to the powerhouse complex wi 11 be by
means of an unlined access tunnel approximately 3,200 feet long as \'Jell
as by a 950-foot deep vert i ca 1 access shaft. Turbine di.scharge ~Ji 11 be
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conducted to the ·river by means of a single 38-foot-diameter tailrace
tunne 1 1 eadi ng from a surge chamber downstream from the powerhouse
cavern. Compensation flow pumps at the power pi ant wi 11 ensure suit-
able flow in the river for environmental rr.akeup requirements between
the dam and tailrace tunnel outlet portal.. A separate transformer
gallery just upstream from the powerhouse cavern \<~ill house twelve
, single-phase 15/345-KV transformers. The transformers wi 11 be con-
nected by 345-KV; single phase, oil-filled cable through a cable shaft
to the switchyard at the surface.
Outlet facilities consisting of seven individual outlet conduits will
be located in the lower part of the main dam. These will be designed to
discharge a 11 flood flows of up· to 38,500 cfs, the estimated 50-year
flood. Each outlet conduit will have a fixed-cone valve similar to
those provided at Watana to dissipate energy and minimize undesirab 1 e
nitrogen supersaturation in the. flows downstream. The main spillway
wi 11 a 1 so pe 1 ocated on the north bank. As at Watana, this spi 1 h'lay
wi 11 consist of an upstream agee contra 1 structure with three vert i ca 1
fixed-wheel gates and an inclined concrete chute and flip bucket de-
signed to pass a maximum discharge of 126,000 cfs. This spillway)
together with the outlet facilities, will t.lus be capable of discharg-
ing the estimated 10,000-year flood. An emergency spillway and fuse_
plug on the south bank will provide sufficient additional capacity to-
permit discharge of the Pr~F without overtopping the darn.
7. 2 -Arch Dam
The· Devil Canyon Dam will be located at the Devil Canyon gorge, River
Mile 152, approximately 32 miles downstream from Watana. The arch dam
will be located at the upstream entrance of the canyon.
The dam will be a thin-arch concrete structure 646 feet high, with a
crest length-to-height ratio of approximately 2, and designed to with-
stand dynamic loadings from intense seismic shaking. The proposed
height of the dam is well within precedent.
(a) Foundations
Bedv"'ock is well exposed along the canyon walls and the ~rch dam
wi 11 be founded on sound bedrock. Approximately 20 to 40 feet of
weathered and/or loose rock will be removed beneath the dam foun-
dation. All bedrock irregularities will be smoothed out beneath
the foundation to eliminate high stress concentrations within the
concr'ete.. During excavation the rock. wi 11 also be trimmed, as far
as is practical, to increase the symmetry of the centerline pro-
file and provide a corl_lparatively uniform bearing stress distribu-
tion across the dam. Areas of deteriorated dikes and the 1 oca 1
areas of poorer qul aity rock wi 11 be excavated and supplemented
with dental concrete •
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The foundation will be consolidation grouted over its entire area$
and a double grout curtain up to 300 feet deep wi 11 run beneath
the dam and its adjacent structures as shown in Plate 51.. Grout-
ing will be done from a system of galleries which will run
through the dam and into the rock. Within the rock· these gal-
leries will also serve as collectors for. drainage holes which will
be drilled just downstream of the grout curtain and intercept any
seepage passing through the curtain.
(b) Arch Dam Geometry
The canyon is V-shaped below Elevation 1350. Sound bedrock does
not exist above this level on the left abutment and an artificial
abutment is provided up to the crest Elevation 1463 in the form of
a massive concrete thrust block designed to take the thrust from
the uppe,· arches of the dam. A corresponding block ·is formed on
the right abutment to provide as s}1llmetrical a profi1e. as possible
bordering the dam and giving a s}'Tllmetrical stress distribution
across the faces of the horizontal arches.
Two slight ridges are formed by the rock at both abutments. The
arch dam abuts the upstream side of these such that the plane of
the contact of the horizontal arches is generally normal to the
faces of the dam. An exception is in the lower portion of the dam
where the rock in the upstream corners is retained in order to
decrease the excavation.
The dam bears directly on the rock foundation over the entire
length of the contact surface. The bedrock at the foundation wi 11
be excavated to remove all '.;~athered material and further trimmed
to provide a smooth 1 ine t'l t.~e foundation, thus avoiding abrupt
changes in the darn profile ::·· J consequent stress concentrations.
The dam is a double. curvature structure with a copola shape of the
crown cantilever defined by vertical curves of approximately 1352
feet and 893 feet radius. The hori zonta 1 arches are based on a
two-center configuration with the arches prescribed by varying
radii moving along two pairs of center lines. The shorter ~adii
of the intrados face cause a broadening of the arches at the abut-
ment, thus reducing the contact stresses. The dam reference plane
is approximately central to the floor of the canyon and the two-
center configuration assigns longer radii to the arches on the
wider right side of the valley, thus providing comparable contact
areas and central angles on both sides of the .arches at the
concrete/rock interface. The longer radii will also allow the
thrust from the arches to be directed more into the abutment
rather than parallel to the river. The net effect of this two-
center layout will be to improve the symmetry of the arch stresses
across the dam.
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The crown cantilever ·is 643 feet high. It is 20 feet thick at the
crest and 90 feet at the base, a base width to height ratio of
0 .. 140. The radii of the dam axis at crest l eve 1 are 6 97 feet and
777 feet for the left and right sides of the dam, respectively.
The central angles vary between 53° at Elevation 1300 and 10° at
the base for the left side of the arch, and 57° to 10° for the
right side. The dam crest length is 1260 feet and the ratio of
crest length to height for the dam is 1~96 (thrust blocks not
incl~ded). The volume of concrete in the dam is approximately 1.3
x 10 cubic yards.
(c) Thrust Blocks
The thrust blocks are shown on Plate 50. The massive concrete
block on the left abutment is 113 feet high and 200 feet long. It
wi 11 be formed to take the thrust from the upper part of the dam
abo·.te the existing sound rock Jevel.. It will also serve as a
transition between the concrete dam and the adjacent roc fill
saddle dam. The inclined end face of the block will abut and seal
against the irnpervi ous saddle dam core and be enve 1 oped by the
supporting rock shell.
The 113 foot high, 125 foot long thrust block formed high on the
right abutment at the end of the dam, adjacent to the spillway
control structure, wi 11 transmit thrust from the dam through the
intake control structure and into the rock.
7.3 -Saddle Darn
The saddle dam at Devil Canyon, which is of similar configuration as
the main Watana dam, wi 11 be of earth and rock fi 11 construction and
will consist of a central compacted core protected by fine and coarse
filters upstream and downstream!) The downstream Oli-er shell will con-
sist of two zones: a lower· zone of clean pressed roc.;'.fi11 material and
an upper zone of unprocessed rockfi 11 materia 1. The upstream outer
shell will consist of cleaned and graded rockfill material. A typical
cross section is shown on Plate 53 and described below.
(a) Typical Cross Section
The central core slopes are 1H:4V with a top width of 35 feet.
The thickness of the core at any section will be slightly more
than 0. 5 times the head of water at that section. Minimum core-
foundation contact will be 50 feet, requiring flaring of the cross
sect ·jon at the abutments.
The upstream and downstrP;lrn filter zones wi 11 increase in thick-
ness from 45 and 30 feet, ,·espective 1y, near the crest of the dam
to a maximum of approximately _60 feet at the filter-foundationc
contact. They are sized to provide protection against possible
p·i ping· through· transverse cracks that caul d occur because of
settlement or resulting from internal displacement during a
seismic event.
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Protection against wave and ice act1on on the upstream slope will
consist of a 10-foot 1 ayer of riprap comprising quarried rock up
to 36 inches in size~
The estimated volume of material needed to construct the saddle
dam are approximately:
-core materia 1 :
-fine 'filter material:
-coarse filter material:
-rockfill material:
310,00C ~ubic yards
230,000 cubic yards
180~000 cubic yards
1,200,000 cubic yards
The saturated sections of both shells will be constructed of com-
pacted clean rockfill, processed to remove fine material in order
to minimize pore pressure generation and ensure rapid dissipation
during and after a seismic event. The lower section of the down-
stream shell, due to a unique combination of bedrock and topo-
graphic elevations, may become saturated by natura 1 runoff or dam
seepage. During design the cost of a major drainage system to
prevent this occurrence will be weighed against the added cost of
processing the materials for lower portion of the fill. Since
pore pressures cannot develop in the unsatured upper section of
the downstream she 11, the materia 1 in that zone wi 11 be unpro-
cessed rockfill from surface or underground excavations.
{b) Crest Details and Freeboard
A 3 foot high parapet will be constructed on the crest of the arch
dam to provide a freeboard of 11 feet.
The highest reservoir 1 eve 1 wi 11 be Elevation 1465.3 under PMF
conditions. At this elevation, the fuse plug in the emergency
spillway wi 11 have been breached and the reservoir 1 eve 1 wi 11 fa 11
to the spillway sill elevation of 1434. The normal maximum pool
elevation is 1455.
The ty!)ical crest detai 1 for the saddle dam is shown in ?1 ate 53.
Because of the narrowing of the dam crest, the filter zones are
reduced in width and the upstream and downstream coarse filters
are eliminated. A layer of fi 1 ter fabric is incorporated to
protect the core materia 1 from damage by ft,.ost penetration and
dessicaticn, and to act as a coarse filter where required.
A minimum saddle dam freeboard of three feet will be provided for
the PMF: hence, the nomina 1 crest of the saddle dam wi 11 be
Elevation 1469. In addition, an allowance of one percent of the
height of the dam will be made for potential settlement of the
r·ockfi·n shells under seismic loading. An allowance of one foot
has been made for settlement adjacent· to the abutments; hence, the
constr\J~cted crest elevations of the saddle dam wi 11 be 1470 at the
abutment~, rising in proportion to the total height of the dam to
Elevation 1472 at the maximum se~tion. Under normal operating
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conditions~ the freeboard will range from 15 feet at the abutments
to 17 feet at the center of the dam. Further allowances wi 11 be
made to compensate for static settlement of the dam after
completion due to its own weigtt and the effect of saturation of
the upstream shell, which will tend to produce additional
breakdown of the rock fi 11 at point contacts. Therefore, one
percent of the dam height will be allowed for such settlement,
giving a maximum crest elevation on completion of the construction
of 1475 at the maximum height, and 1471 at the abutments.
The allowances for post-construction settlement and seismic slump-
; ng wi 11 be achieved by steepening _both slopes of the dam above
Elevation 1400. These allowances are considered conservative,
(c) Grouting and Pressure Re 1 i ef System
(d}
The rock foundation will be improved by consolidation grouting
over the core contact area and by a grouted cutoff a 1 ong the
·centerline of the core. The cutoff at any location will extend to
a depth of a least 0.7 of the water head at that location as shown
on Plate 51.
A grouting and drainage tunnel will be excavated in bedrock
beneath the dam along the c~nterline of the core and wi11 connect
with a similar tunnel beneath the adjacent concrete arch dam and
thrust block. Pressure relief and drainage holes will be drilled
from this tunnel and seepage from the drainage system wi 11 b~e
discharged through the arch dam drainage system to ultimately exit
downstream below tailwater level.
Instrumentation
Instrumentation will be installed within all parts of the dam to
provide monitoring during construction as well as during opera-
tion. Instruments for measuring internal vertical and horizontal
displacements, stresses and strains, and tot a 1 and fluid pres-
sures, as well as surface monuments and markers similar to those
proposed for the Watana dam9 will be installed.
7.4 -Diversion
(a) Generai
Diversion of the river flow during consk~ct ion wi 11 be through a
single 30-foot-di ameter concrete-1 i nea diversion tunnel on the
south bank. The tunne 1 wi 11 have a horseshoe-shaped cross-
section and be 1,490 feet in length. The diversion tunnel plan
and profile is shown on Plate 54. ·
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The tunnel is designed to pass a flood with a return frequency of
1:25 years routed through the Watana Reservoir. The peak flow.
that the tunnel will discharge will be 37,800 cfs. The maximum
water surface elevation upstream of the cofferdam wi 11 be Eleva-
tion 944.. A rating curve is presented in Figure 13.1. ·
(b) Cofferdams
The upstream cofferdam will consist of a zoned embankment founded
on a closure dan (see PI ate 54). The closure dam wi 11 qe con-
structed to Elevation 915 based on a low water elevation of 910
and will consist of coarse material on the upstream side grading
to finer material on the downstream side. When the closure dam is
completed, a grout curtain or slurry wall cut-off will be con-
structed to minimize seepage into the main dam excavation. Final
details of this cut-off will be determined following further in-
vestigations to define the type and properties of river alluvium.
The abutment areas wi 11 be excavated to sound rock prior to
placement of any cofferdam material •
The cofferdam, from Elevation 915 to 947, wi 11 be a zoned embank-
ment consisting of a central core, fine and coarse upstream and
downstream filters, and rock and/or gravel shells with riprap on
the upstream face. The downstream cofferdam wi 11 be a similar
closure dam constructed from Elevation 860 to 895, with a cut-off
to bedrock.
The upstream cofferdam crest elevation will have a 3 foot fre.e-
board allowance for settlement and wave runup. Under the proposed
schedule, the Watana development will be operational when this
cofferdam is constructed. Thermal studies conducted show that
discharge from the Watana reservoir will be at 34°F when passing
through Devil Canyon. Therefore, an ice cover will not form U..liJ)-
stream of the cofferdam, and no freeboard allowance for ice wii11
be necessary.
(c) Tunnel Portals and Gates
A gated concrete intake structure will be located at the upstream
end of the tunne 1 (see ~·1 ate 55) . The porta 1 and gate will be
designed for an external pressure (static) head of 250 feet.
Two 30 feet high by 15 feet wide water passages will be formed in
the intake structure, separated by a central concrete pier. Gate
guides will be provided within the passages for the operation of
30-foot high by 15-foot wide fixed wheel closure/control gates.
Each gate, which will be operated by a wire rope hoist in an
enclosed housing, will be designed to operate wit.h a 75-foot oper-
ating head (Elevation 945).
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Stoplog guides will be installed in the diversion tunnel to permit
dewatering of the diversion tunnel for plugging operations. The
stoplogs will be in sections to faci1 itate relatively easy hand-
ling, with a mobile crane using a follower beam.
(d) Final Closure and Reservoir Fi!lin~
Upon completion of the Devil Canyon dam to a height sufficient to
allow ponding to a level above the outlet facilities~ the intake
gates will be partially closed, allowing for a discharge of mini-
mum envir·onmental flows while raising the upstream water level.
Once the level rises above the lower level of discharge valves,
the diversion gates will be permanently_ closed and discharge will
be through the 90-inch-di ameter fixed cone valves i.n the dam. The
diversion tunnel will be plugged with concrete and curtain grout-
ing performed around the plug. Construction will take approxi-
mately 1 year. During this time the reservoir will not be allowed
to rise above Elevation 1135.
The filling of the reservoir from this elevation. will take approx-
imately 2 to 3 weeks to operating Elevation 1455.
7.5-Outlet Facilities
The primary function of the outlet facilities is to provide for
discharge through the main dam, in conjunction with the power
f ac i 1 it i es, of routed floods with up to 1: 50 years recurrence
period at the Devil Canyon reservoir. This will require a total
discharge capacity of 38,500 cfs through the valves. The use of
fixed-cone valves will ensure that downstream erosion will be min-
imal and nitrogen supersaturation of the re)eases will be reduced
to acceptable levels, as in the case of the Watana development. A
further function of these releases is to provide an emergency
drawdown for the reservoir, should maintenance be necessa~y on the
main dam or low level submerged structures, and also to act ·as a
diversion facility during the latter part of the construction
period.
The outlet facilities will be located in the lower portion of the
main dam, as shown on Plate 52, and will consist of seven fixed-
cone discharge valves set in the lower part of the·arch dam.
(a) Outlet
The fixed-cone type discharge valves wi 11 be located at two eleva-
tions: the upper group, consisting of four 102-inch diameter
valves, will be set at Elevation 1050, and the lower group of
three 90-inch diameter valves will be set at Elevation 930. The
valves will be installed nearly radially (normal to the dam
center1 ine) with the points of impact of the issuing jets sta~~
gered as shown in Plate 52.
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The fixed-cone valves will be installed on individual conduits
passing through the dam, set close to the downstream face, and
protected by upstream ring follower gates located· in separate
chanbers within the dam. Provisions will be made for maintenance
and removal of the valves and gates. The gates and valves will be
1 inked by a 20-foot-high gallery running across the dam and into
the left abutment where access will be provided by means of aver-
tical shaft exiting through the thrust block. Although secondary
acces~ t'li 11 be provided vi a a simi 1 ar shaft from the north abut-
ment, primary access and installation are both from the south
side.
The valve and gate assemblies will be protected by individual
trashracks installed on the upstream face. The racks "will be
removable along guides running on the upstream dam face. The
racks will be raised by operating at deck 1eve1. Guides will be
installed for the installation of bulkhead gates~ if required, at
the upstream face. The bulkhead gates wi 11 be handled by a
travelling gantry crane located at the top of the dam.
(b) Fixed-Cone Valves
The 102-inch diameter valves operating at a gross head of 420 feet
and the 90-inch diameter valves operating at a head of 525 feet
have been se 1 ected to be wi th.i n current precedent cons ·i der i ng the
valve size and the static head on the valve. The valves will be
located in individually heated rooms and will be provided with
electric jacket heaters installed around the cylindrical sleeve of
each valve. The valves will be capable of year round operation,
although \t~inter operation is not contemplated. Normally, when the
valves are closed, the upstream ring follower gates will also be
closed to minimize leakage and freezing of water through the valve
seats.
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The valves ~."'i 11 be operated remotely by two hydraulic operators.
Operation of the valves will be from either Watana or by local
operation.
(c) Ring Follower Gates
Ring follower gates will be installed upstream of each va.l.ve.
The ring follower gates will have nominal diameters of 102 and 90
inches and will be of welded or cast steel construction. The
gates will be designed to withstand the total static head under
full reservoir.
The design and arrangement of the ring follower gates will be as
for Watana.
(d) Trashracks
A stee 1 trash rack \Ali 11 be i nsta 11 ed at the upstream entrance to
each water passage to prevent debris from being drawn into the
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discharge valves.
mately 9 inches.
across the racks.
B u 1 khead Gates
The bar spacing on the racks will be approxi-
Provision wi 11 be made for monitoring head loss
The bulkhead gates will be installed only under balanced head con-
ditions u~ing the gantry crane. The gates will be 13 feet and 11
feet square for the upper and lower valves, respectively.
Each gat.e will' be designed to withstand full differential head
under maximum reservoir water level. One gate for each valve size
has been assumed. The gates wi 11 be stored at the dam crest
1 evel.
A temporary cover will be placed in the bulkhead gate check at
trashrack level to prevent debris from getting behind the trash-
racks.
The bulkhead gates and trashracks will be handled by an electric
travelling gantry type crane located on the main dam crest at Ele-
vation 1468. The crane and lifting arrangement will have provi-
sion _for lowering a gate arcund the curved face of the dam.
7.6-Main Spillway
The main spillway at Devil Canyon will be located on the north
side of the canyon (see Plate 56). The upstream_ contrc1 struct\Jre
vli 11 be adjacent to the arch dam thrust b 1 ock and wi 11 discharge
down an inclined concrete-1 ined chute constructed on the steep
face of the canyon wall. The chute will terminate in a flip
bucket which will direct flows downstream and into the river.
The spillway will be designed to pass the 1:10,000 year Watana
routed flood in conjunction with the outlet facilities. The
spillway will have a design capacity of 125,000 cfs discharged
over a tot a 1 head drop of 550 feet. No surcharge wi 11 occur above
the normal maximum reservoir operating level of 1,455 feet during
passage of this flood.
(a) Approach Channel and Control Structure
The approach channel wi 11 be excavated to a depth of approximately
100 feet in the rock with a width of just over 130 feet and an
invert elevation of 1375.
The contra 1 structure, as shown in Plate 57, wi 11 be a three-bay
concrete structure set at the end of the channel. Each bay will
incorporate a 56-foot-high by 30-foot-wide gate on an agee-crested
weir and, in conjunction with the other gates, will control the
flows passing through the spillway. -The gates wi11 be fixed wheel
gates operated by individual rope hoists.
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(b)
(c)
A gallery is provided within the mass concrete weir from which
grouting can be carried out and dr-ain holes can be drilled as a
continuation of the grout curtain and drainage. beneath the main
dam.. The main access route wi 11 cross· the contra 1 structure deck
upstream of the gate tower and bridge structure.
Spillway Chute r
The spillway chute wi 11 be excavated in the steep north face of
the canyon for a distance of approximately 900 feet, terminating
at El ev ati on 1000. The chute wi 11 tape\,. uniform 1y over its length
from 122 feet at the· upstream end to 80 feet downstream. The
chute wi 11 be concrete-1 ined with invert and wall slabs anchored
to the rock. ·
The velocity at the 1 ower end of the chute wi 11 be approximately
150 ft/s. In order to prevent cavitation of the chute surfaces,
air will be introduced into the discharges. As at Watana, air
will be drawn in along the chute via an underlying aeration gal-
lery and offshoot ducts extending to the downstream side of a
raised step running transverse to the chute.
An extensive underdrainage system will be provided, similar to
that described for ~vatana, to ensure adequate underdrainage of the
spillway chute and stabi 1 ity of the structure.,. This system is
designed to prevent excessive uplift pressures due to reservoir
seepage under the contra 1 structure and from ground water and
seepage through construction joints from the high velocity flows
within the spillway itselfo
The dan grout curtain and drainage system wi 11 be extended under
the spi 11 way contra 1 structure uti 1 i zing a ga 11 ery through the
rollway .. A system of box drains-will be installed for the entire
length of the spillway under the concrete slab. To avoid blockage
of the system by freezing of the surface drains, a 30=foot deep
drainage gallery will also be constructed along the entire length
of the spillway.. Drain holes from the surface drains will inter-
sect the gallery.. To ensure adequate foundation quality f;or
anchorage, consolidation grouting will be undertaken to a depth of
20 feet. Drainage holes drilled into the base of the· high rock
cuts will ensure increased stability of the excavation.
Flip Bucket
The spillway chu_te will terminate in a mass concrete flip bucket
founded on sound rock at Elevation 970, approximately 100 feet
above the river. Detailed geometry of the curve of the flow sur~
face of the bucket will be confirmed by means of hydraulic model
tests. A grouting/drainage gallery will be provided within the
bucket. The jet issuirig from the bucket will be directed down-
stream and parallel to the river alignment.
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(d) Plunge Pool
The impact area of the issuing spillway discharJe will be limited
to the area of the river surface downstream to prevent excessive
erosion of the canyon walls. This wi 11 be done by appropriate
shaping of the ,flow surface of the flip bucket on the basis of
model studies. Over this impact area the alluvial material in the
riverbed will be excavated down to sound rock to provide a plunge
pool in which most of the inherent energy of the discharges will
be dissipated, although some energy will already have been dissi-
pated by friction in the chute, and in d-ispersion and friction
through the air.
7. 7 -Emergency Spfllway
The emergency spillway will be located on the south side of the
river south of the rockfi 11 saddle dam. It will be excavated
within the rock underlying the south side of the saddle and will
continue downstream for approximately 2,000 feet.
An erodible fuse plug, consisting of impervious material and fine
gravels, will be constructed at the upstream end of the spillway.
It will be designed to wash out when overtopped by the reservoir:t
releasing flows of up to 160,000 cfs in excess of the combined
main spillway and outlet capacities and thus preventing overtop-
ping of the main or saddle dams during the passage of the PMF.
(a) Fuse Plug and Approach Channel
The approach channel to the fuse plug will be excavated in the
rock and will have a width of 220 feet and an invert elevation of
1434. The channel wi 11 be crossed by the main access road to the
dam on a bridge consisting of concrete piers, precast beams, and
an in situ concrete bridge deck. The fuse plug will fill the
approach cha~nel and will have a maximum height of 31.5 feet with
a crest elevation of 1465.5. The plug will be located on top of a
fl atcrested concrete weir placed on an air excavated rock founda-
tione The plug \'Jill be traversed by a pilot channel with an
invert elevation of 1464a
(b) Discharge Channel
The channel will narrow downstream, leading into .a steep valley
tributary above the Sus i tna River. This channel wi 11 rapidly
erode under high flows but will serve the purpose of training the
initial flows in the direction of the valley and away from the
permanent project facilities. ·
7. 8 -Devi 1 Canyon Power F aci 1 it i es
(a) Intake Structure
The intake structure is located on the south side of the canyon
as shown on Plate 64 .. · Separate intakes are provided for each
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turbine. Reservoir levels will vary between Elevations 1455 and
1405. Each intake will be provided with a single intake gate, a
set of steel trashracks, and provision for placing bulkhead gates
upstream from the intake gate. A traveling gantry crane on the
intake deck at Elevation 1466 will service all four intakes. The
mechanical equipment is d~scribed in more detail below.
The intake will be located at the end of a 200-foot-long unlined
approach channe 1 • The overburden in this area is estimated to be
approximately 10 feet deep. The excavation for the intake struc-
ture wi 11 require four tunnel porta 1 s on 60 foot centers.. Ruck
pillars 32 feet wide and 38 feet deep will separate the portals.
(b) Intake Gates
Each of the four power intakes will have a single fixed whee 1
intake gate with a nominal operating size of 20-feet-wide by
25-feet-high. The gates will have an upstream skinpl ate and seal
and will be operated '··by hydraulic or wire rope hoists located in
heated enclosures immediately below deck level. The gates, which
will normally close under balanced head conditions to permit
dewatering of the penstock and turbine water passages for turbine
inspection and maintenance, will also be capaple of closing under
their own weight with full flow conditions and maximum reservoir
water level in the event of runaway of the turbines. A heated air
vent will be provided at the intake deck to satisfy air demand
requirements when the intake gate is closed with flowing water
conditions.
(c) Intake Bulkhead Gates
One set of intake bulkhead consisting of two gate sections will be
provided for closing the intake openings. The gate will be used
to permit inspection and maintenance of the intake gate and intake
gate guides. The gates will be raised and lowered under balanced
water conditions only.
(d) Trashracks
Each of the four intakes wi 11 have tra.shracks at the upstream
face. The trashrack wi 11 have a bar spacing of about 6 inches and
be designed for a maximum differential head of about 20 feet. Each
trashrack will be constructed in two sections for removal by means
of a follower suspended from the intake.gantry crane.
(e) Intake Gantry Crane
A 50-ton capacity (approximately) electrical traveling gantry
crane will be provided on the intake deck at Elevation 1466 for
handling the trashracks, and intake bulkhead gates and for servi-
cing the intake gate equipment.
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7.9 -Penstocks
The power plant will have four penstocks, one for each unit. The
maximum static head on each penstock wi 11 be 638 feet, as rHeasured
from normal maximum operating level (Elevation 1455) to centerline
distributor level {Elevation 817). An allowance of 35 percent has
been made for pressure rise in the penstock under transient condi-
tions, giving a maximum head of 861 feet •. ~laximum extreme head
(including transient loadings) corresponding to maximum reservoir
flood level will be 876 feet.
The penstock tunnels are fully concrete-1 ir,ed except for a 250-
foot section upstream of the powerhouse which is steel-lined. The
inclined sections of the concrete-lined penstocks will be at ss·
to the horizontal.
(a) Steel Liner
The. steel-lined penstock will be 15 feet in diameter. The first
50 feet of stee 1 liner immediate 1 y upstream of the powerhouse wi 11
be designed to resist the full internal pressure. The r·emainder
of the steel liner, extending another 200 feet upstream, will be
designed to partially resist the internal pressure together with
the rock. Beyond the steel 1 iner, the hydraulic loads are sup-
ported solely by the rock tunnel with a concrete liner.
The steel 1 iner is surrounded by a concrete infi 11 with a min imun
thickness of 24 inches. A tapered steel transition will be pro-
vided at the junction between the steel 1 iner .and the concrete
1 iner to increase the internal diameter from 15 feet to 20 feet""
(b) Concrete Liner
The thickness of the concrete 1 ining will vary with the design
head, with the minimum thickness of lining being 12 inches.
The internal diameter of the concrete liner is 20 feet.
(.c) Grouting and Pressut~e Relief Sys!em
A comprehensive pressure relief system will be installed to pro-
tect the underground caverns against seepage from the high pres-
sure penstocks and reservoirs. The system wi 11 consist of smal 1
diameter boreholes set out in an array to intercept the jointing
in the rock. Grouting round the penstocks wil1 also be under-
taken.
7.10-Powerhouse and Related Structures
The underground powerhouse camp 1 ex wi 11 be constructed in the
north side of< the canyon. This will require the excavation of
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three major caverns (powerhouse, transformer gallery and surge
chamber), with interconnecting rock tunnels for the draft tubes
and i so 1 a ted phase bus ducts.
An unlined rock tunnel will be constructed for vehicular access to
the three rna in rock caverns. A second l,Jnl i ned rock tunne 1 wi 11
provide access from the powerhouse to the foot of the arch dam.
Vertical shafts will be required for personnel access by elevator
to the underground powerhouse; for oil filled cable from the
transformer gallery; and for surge chamber venting.
The draft· tube gate gallery and cavern wi 11 be located in the
surge chamber cavern, above maximum design surge level.
The genera 1 1 ayout of the powerhouse camp 1 ex is shown on Plates
65, 56 and 67. The transformer gallery wi 11 be located upstream
of the powerhouse cavern and the surge chamber located downstream
of the powerhouse cavern. The spacing between the underground
caverns has been fixed so as to be at least 1. 5 times the main
span of the larger excavation.
(a) Access Tunnels and Shafts
The 3,000-foot long main access tunnel w111 connect the powerhouse
cavern at Elevati-on 858 with the canyon access road on the north
bank. A secondary access tunne 1 runs from the rna in powerhouse
access tunnel to the foot of the arch dam, for routine maintenance
of the fixed cone valves .. Branch tunnels from the secondarv
access tunnel will provide construction access to the lower sec:
tion of the penstocks at Elevation 820. Separate branch tunnels
from the main access tunnel give vehicle access to the transformer
gallery at Elevation 896 and the draft .tube gate gallery at Eleva-
tion 908. The maximum gradient on the· permanent access tunnel 1s
8 percent; the maximum gradient on the secondary access tunnel is
9 percent.
The cross section of the access tunnels, which is dictated by
requirements for construction plant, is modified horseshoe shape
35-feet wide by 28-feet high.
The main access shaft wi 11 be located at the north end of the
powerhouse cavern, providing personnel access by elevatn,Jfrom the
. surface. Horizontal tunnels will be provided from this shaft for
pedestrian access to the transformer gallery and the draft tube
gate gallery. At a higher level, access will also be available to
the fire protection head tank.
Access to the upstream grouting gallery will be from the transfor-
mer gallery main access tunnel, at a maximum gradient of 13.5
percent.
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The cross section of the access tunnels, which is dictated by re-
quirements for constr-uction plant, is a modified horseshoe shape
35-feet wide by 28-feet high.
The main access shaft will be located at the north end of the
powerhouse cavern, providing personnel access by elevator from the
surface. Horizontar tunnels will be provided from this shaft for
pedestrian access to the transformer gallery and the draft tube
gate gallery. At a higher level, access will also be available to
the fire protection head tank.
Access to the upstream grouting gallery will be from the transfor-
mer gallery main access tunnel, at a maximum gradient of 13.5
percent.
(b) Powerhouse Cavern
The main powerhouse cavern is designed to accommodate four verti-
c·al shaft Francis turbines, in line, with direct coupling to over-
hung generators. Each unit is rated at 150 MW at 575-foot net
heado
The unit spacing will be 60 feet with an additional 110-foot ser-
vice bay at the south end of the powerhouse for routine mainte-
nance and construction erectiono The control room will be located
at the north· end of the rna in powerhouse floor. The width of the
cavern will be sufficient for the physical size of the generator
plus galleries for piping, air-conditioning ducts, electrical
cables, and isolated phase bus. The overall size of the powe~
house cavern wi 11 be 74 feet wide, 360 feet long, and 133 feet
high.
Compensation flow of 500 cfs will be provided by two 1300 hp vert-
ical shaft mixed flow pumps, installed in a gallery" below the
service bay. Each pump is rated at 115,000 gpm at 35-foot head.
Water wi 11 be taken from the base of the surge chamber and pumped
1000 feet to the dam toe through a discharge pipe laid partly in
the secondary access tunnel and partly in a separate outlet
tunne1.
Multiple stairway access points will be available from the power-
house main floor to each gallery level. Access to the transformer
gallery from the powerhouse wi 11 be by a tunnel from the access
shaft or by a stairway through each of the four bus tunnels.
Access will also be available to the draft tube gate gallery by a
tunnel from the main access shaft.
A service elevator wi 11 be provided for access from the service
bay area on the main floor to the ·machine shop, and the dewatering
and drainage galleries on the lower floors. Hatches will be pro-
vided through a.ll main floors for installation and routine main-
tenance of pumps, valves and other heavy equir.ment using the main
powerhouse crane.
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(~) Transformer Gallery
The transformers will be located underground in a separate unlined
rock cavern, 120 feet upstream of the powerhouse cavern, with four
interconnecting tunnels for the isolated phase bus. There will be
12 single-phase transformers with· one group of three transformers
for each generating unit. Each transformer is rated at 13/345, 70
t4VA.. For increased reliability, one spare transformer and one
spare HV circuit will be provided. The station service transfor-
me~ .. s and the surface facilities transformers will be located in
the bus tunnels. Generator exc it at ion transformers wi 11 be loca-
ted on the main powerhouse floor. The overall size of the trans-
former gallery will be 43 feet wide, 40 feet high, and 421 feet
long; the bus tunnels will be 14 feet wide and 14 feet high.
High voltage cables will be taken to the surface in two 7.5 foot
interval diameter cable shafts, and provision will be made for an
inspection hoist in each shaft.
Vehicle access to the transformer gallery wi 11 be from the south
end vi a the main powerhouse access tunne 1. Personnel access wi 11
be from the main access shaft or through each of the four isolated
phase bus tunnels.
(d) Surge Chamber
(e)
A simple surge chamber will be constructed 120 feet downstream of
the powerhouse to control pressure fluctuations in the turbine
draft tubes and tailrace tunnel under transient load conditions,
and on machine start-up. The chamber wi 11 tie common to all four
draft tubes and the inlet pipe to the compensation flow pumps.
The overall size of the chamber will be 75 feet wide, 300 feet
long, and 188 feet high.
The draft tube gate gallery and crane wi 11 be located in the same
cavern, above the maximum anticipated surge level. Access to the
draft tube gate gallery will be by a rock tunnel from the· main
access tunnel. The tunnel will be widened locally for storage of
the draft tube gates. ,
The chamber will be an unlined rock excavation with localized rock
-support as necessary for stability of the roof arch and wa11s.
The guide blocks for the draft tube gates will be of reinforced
concrete anchored to the rock excavation by rock bolts.
Draft Tube Tunnels
The orientation of the draft tube tunnels will be 300°. The tun-
ne 1 s wi 11 be 23 f ee.t in diameter and stee 1 and concrete lined,
with the concrete having a thickness of about 2 feet.
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7.11 -Tailrace Tunnel
The tailrace pressure tunnel will convey power plant discharge
from the surge chamber to the river. The tunne 1 has a modified
horseshoe cross sect~on with an internal dimension of 38 feet, and
wi 11 be concrete 1 ined throughout with a minimum thickness of 12 ·
inches. The length of the tunnel is 6800 feet.
The tailrace portal site will be located at a prominent steep rock
face on the right bank of the river. The portal outlet is rectan-
gular in section, which reduces both the maximum outlet velocity
(8ft/s) as well as the velocity head losses~ Vertical stoplog
guides are provided for c 1 osure of the tunne 1 for tunne 1 inspec-
tion and/or maintenance.
7o12 -Access Roads
To be added in October.
7.13 -Site Facilities
The construction of the Devil Canyon development will require var-
ious facilities to support the construction activities throughout
the entire construction period. Following construction, the plan-
ned operation and maintenance of the development will be centered
at the Watana development; therefore, minimum facilities at the
site will be required to maintain the power facility.
As described for Watana, a camp and construction village will be
constructed and maintained at the project site. The· camp/village
will provide housing and living facilities for 2,300 people during
construction. Qther site facilities include contractor's work
areas, site power, services, and communi-cations.. Items such as
power and communications and hospital services will also be re-
quired for cons·cruction operations independent of camp operations.
Buildings used for the Watana development will be used where pos-
sible in the Devil Canyon development. Current planning calls for
dismantling and reclaiming the site after construction. Electric
power will be provided from the Watana development. Tre salvaged
build~ng modules used from the Watana camp/village will be retro-
fitted from fuel oil heating to electri_c heat.·
(a) Temporary Camp and Village
The proposed location of +:he camp/viilage is on the south bank of
the Susitna River between the damsite and Portage Creek, approxi-
mately 2. 5 mi 1 es southwest of the Dev i 1 Canyon dam (see Plate 72).
The south side of the Susitna was chosen because the main access
road in this area wi 11 be from the south. South-facing slopes
will be used for the camp/village location.
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The camp will consist of portable woodfrarne dormitories for single
status workers with modular mess halls, recreational buildings,
bank, post office, fire station, warehouses, hospital, offices,
etc. The camp will be a single status camp for approximately 1,780 workers.
The village, designed for approximately 170 families, will be
grouped around a ser·vice core containing a school, gymnasium~
stores, and recreation area.
The twa areas will be separated by approximately l/2 mile to oro-
vide a buffer zone between areas. The hospital wi 11 ser·ve both
the main camp and the village.
This camp loca~ion will be separated from the work areas by
approximately a mi 1 e. Travel time to the work area wi 11 generally
be less than 15 minutes~
The camp/village will be constructed in stages to accommodate the
peak work force as presented in Table 13.1. Table 13.1 also pre-
s.ents the camp/village facility design numbers. The facilities
have been designed for the peak work force plus 10 percent for 11
turnover 11
• The "turnover" includes provisions or buffers for
overlap of workers and vacations. The conceptual layouts for the
camp/village are presented in Plate~ 73 and 74.
Construction· camp buildings will consist largely of tra·iler-type
factory-built modules assembled at site to provide the various
facilities required. The modules wi 11 be. fabricated with heathlg,
lighting, and plumbing services, interior finishes, furnishings,
and equipment, Trailer modules will be supported on timber crib-
bing or blocking approximately two feet above grade.
larger structures, such as the central utilities building, g}m~
and warehouses, wi 11 be pre-engineered, steel-framed structures with metal cladding.
The various buildings in the camp are identified on Plate 73.
(b) Site Power and Utilities
(i) Power
A 345 kV transmission line from Watana and a substation
will -be in service during the constr~ction activities. Two
transformers will be installed at the substation to reduce
the line voltage to the desired voltage levels.. One of
these transformers wi 11 be the same used during the Watana
development.
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Power will be sold to the contractors by the Power Author-
; ty. The peak demand during construction is estimated at
20 MW for the camp/vi 11 age and 4 MW for construction re-
quirements for a total of 24 MW. The distribution system
for the camp/village wi 11 be 4.16 kV.
( i i} Water
The water supply system will serve the entire camp/village
and selected contractor's work areas. The water supply
system will provide for potable water and fire protection.
· The estimated peak popu 1 at ion to be served wi 11 be 2, 300
(1,780 in the camp and 520 in the village).
The principal sourre of water will be the Susitna River.
The water wi 11 be treated in accordance with the Environ ...
mental Protection Agency (EPA) primary and secondary re-
quirements.
(iii) Wastewater
One waste water collection and treatment system will serve
the camp/village. Gravity flow lines with lift stations
will be used to collect the wastewater from all of the camp
and village facilities. The 11 in-camp" and 11 invillage" col-
1 ect ion systems wi 11 be run through the permawa 1 ks and
utilidors so that the collection system will always be pro-
tected from the elements. ·
At the village, an aerated collection basin will be in-
stalled to collect the sewage. The sewage wili be pumped
from this collection basin through a force main to the
sewage treatment plant.
Chemical toilets located around the site will be serviced
by sewage trucks, which will discharge directly into, the
sewage treatment plant.
The sewage treatment system wi 11 be a biological system
with lagoons. The system w111 be designed to meet A1 ask an
state water 1 aw secondary treatment standards. The 1 agoons
and system will be modular to a11ow for growth and contrac-
tion of the camp/village.
The 1 ocat ion of the treatment p 1 ant is shown on Plates 72
and 73. The location was selecteo to avoid unnecessary
odors in the camp.
The sewage plant will discharge its treated effluent to the
Susitna River. All treated sludge will be dis~osed of in a
solid waste sanitary landfill .
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(c) Contractor's Area
The contractors on the site will require office, shop and general
work areas. Partial space required by the contractors for fabri-
cation shops, storage or warehouses, and work areas will be lo-
cated on the south side of the Susitna River near the owner/
manager's office.. Additional space required by the contractor
\tJi 11 be in the area between the access road and the camp.
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8 -DEVIL CANYON RESERVOIR
The Devil Canyon reservoir, at a normal operating level of 1455 feet,
will be. approximately 26 miles long with a maximum width on the order
of 1/2 mile. The total surface area at normal operating level is 7800
acres. Immediately upstream of the dam, the maximum water depth will
be approximately 580 feet. The minimum reservoir 1 eve 1 wi 11 be 1405
feet during normal operation, resulting in a maximum drawdown of 50
feet. The reservoir will have a total capacity of 1,090,000 acre-feet
of which 350,000 acre-feet will be live storage.
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9 -TURBINES AND GENERATORS -DEVIL CANYON
9.1 -Unit Capacity
The Devil Canyon powerhouse will have four generating units with a nom-
inal capacity of 150 MW based on the minimum December reservoir level
(Elevation 1405} and a corresponding gross head of 555 feet. The head
on the plant will vary from 555 feet to 605 feet.
The rated average operating head for the turbine has been established
at 575 feet. Allowing for generator losses, this results irl a rated
turbine output of 225,000 hp (168 MW) at full gate.
The generator rating has been se 1 ected as 180 MVA with a 90 per~ent
power factor. The generators wi 11 be capab 1 e of continuous operation
at 115 percent rated power. Because of the high capacity factor for
the Devil Canyon station, the generators wi 11, therefore, be sized on
the basis of maximum turbine output at maximum head, allowing for a
possible 5 percent addition in power from the turbine. This maximum
turbine output (250,000 hp) is within the continuous overload· rating of
the generator.
9. 2 -Turbines
The turbines will be of the vertical shaft Francis type with steel
spiral casing and a concrete elbow type draft tube. The draft tube
will have a single water passage (no center pier).
Maximum and minimum heads on the unit will be 542 feet and 600 feet,
respectively. The full gate output of the turbines will be about
240~ 000 hp at max imtm net head and 205,000 hp at minimum net head.
Overgating of the turbines may be possible, providing approximately 5
percent additional power. For preliminary<:) design purposes, the best
efficiency (best gate) output of the units has been assumed at 85 per-
cent of the full gate turbine output.
The full gate and best gate efficiencies of the turbines will be about
91 percent and 94 percent~ respectively, at rated head. The efficiency
will be about 0.2 percent lower at maximum head and 0.5 percent lower
at minimum head.
9.3-Generators
The four generators in the Devil Canyon powerhouse wi 11 be of the vert-
ical shaft!) overhun semi-umbrella type directly connected to the verti-
cal Francis turbinese
The generators will be similar in· construction and design to the Watana
generator and the general features described in Section 3. 2 for the
stator, rotor, excitation system, and other details which apply for the
Devil Canyon generators.
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The rating and characteristics of the generators are as follows:
Rated Capacity:
Rated Power:
Rated Voltage:
Synchronous Speed:
Inertia Constant:
Short Circuit Ratio:
Efficiency at Full Load:
9.4 -Governor System
J.BO MVA, 0. 9 power factor with over-
load rating of 115 percent.
162 MW
15 kV, 3 phase, 60 Hertz
225 rpm
3. 5 MW -Sec/MVA
1.1 (minimum)
98 percent (minimum)
A governor system with electric hydraulic governor actuators will be
provided for each of the Devil Canyon units. The system will be the
same as for Watana (see Section 3.4).
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10 -TRANSMISSION LINES -DEVIL CANYON
To accommodate the additional power from Devil Canyon, the two
initially constructed 345 kV transmission lines from Watana will be
augmented by a third line from Devil Canyon to Knik Arm. The section
between Knik Arm and University substations is a double circuit line
capable of taking the extra capacityo This section will be a single
steel pole~ double circuit structure. The second stage~ or the Devil
Canyon addition shown will include the following:
Substation Additions
Devil Canyon
Willow
Knik Arm
University (Anchorage)
Ester (Fairbanks)
Line Section Additional Circuit
· Devil Canyon to Willow 1
Willow to Knik Arm 1
Knik Arm Crossing 1
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11 -APPURTENANT EQUIPMENT ~ DEVIL CANYON
11.1 -Miscellaneous Mechanical Equipment
(a) Compensation Flow Pumps
The two pumps for providing m1n1mum discharge into the Susitna
River between the dam and the tailrace tunnel outlet portal will
be vertical mixed flow type located in the powerhouse service bay
below the main erection floor, as shown on P1 ate 66. Each pump
will be rated at 250 cfs (115,000 gal/min) at 35 feet tot.a1 head,
and will be driven by 1,400-hp induction motors.
A single pump intake will be located in the surge chamber with an
8-foot-diameter intake tunnel leading to the powerhouse. The in-
take tunnel will bifurcate into individual pump intake conduits
within the powerhouse. The pump discharges wi 11 converge into a
single pump discharge 1 ine.
Butterfly type valves will be installed in the intake andr, dis-
charge lines of each ptJnp to permit isolation of a pump for in-
spection and maintenance. Trash screen guides and a-trash screen
will be provided in the surge chamber at the pump intake. It will
be possible. to remove the trash screen using the draft tube gate
crane discussed be 1 ow. The width of the guides will be selected
so that one of the turbine draft tube gates may be installed in
the intake to permit dewatering the pump intake tunnel for inspec-
tion and/or maintenance of the tunnel or the intake butterfly
valves. Stoplog guides and a set of stoplogs will also be pro-
vided at the downstream end of the pump discharge tunnel to allow
the discharge tunnel to be dewatered. The stoplogs will be
handled.with a mobile crane and a follower.
(b) Powerhouse Cranes .
(c)
Two overhead type powerhouse cranes will be provided at Devil Can-
yon as at Watana. The estimated crane capacity wi 11 be 200 tons.
.
Draft Tube Gates
Draft tube gates. wi 11 be provided to permit dewatering of the tur-
bine water passages for inspection and maintenance of the tur-
bines. The arrahgement of the draft tube gates will be the same
as for Watana, except that only two sets of gates will be pro-
vided, each set with two 21-foot-wide by 10. 5-foot-high sections.
(d) Draft Tube Gate Crane
A crane will be installed in the surge chamber for installation
and removal o.f the draft tube gates. The crane will be either a
monorail {or twin monorail) crane or a gantry crane of 30-ton
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capacity. The crane wi 11 be pendant-operated and have a two po1n't
1 ift. A fa 11 ower wi 11 be used with the crane for handling the
gates. The ·crane runway will be located along the upstream side
of the surge chamber and wi 11 extend over the intake for the com-
pensation flow punps,. as well as a gate unloading area at one end
of the surge chamber.
(e) Miscellaneous Cranes and Hoists
In addition to the powerhouse cranes and draft tube gate cranes!;;
the following cranes and hoists will be provided in the power
plant:
- A 5-ton monorail hoist in the trpnsformer gallery for transfor-
mer maintenance;
-Sma 11 overhead, jib, or A-fr arne type hoists in the machine shop
far handling material; and
-A-frame or monorail hoists in other powerhouse areas for hand-
1 ing small equipnent.
(f) Elevators
Access and service elevators will be provided for the power plant
as follows:
-Access elevator from the control building to the powerhouse;
-Service elevator in the powerhouse service bay; and
... Inspection hoists in cable shafts.
{g) Power Plant Mechanical Service Systems
The power plant mechanical service systems for Devil Canyon will
be essentially the same as discussed in Section 5.1{f) for Watana,
except for the following:
-There wi 11 be no main ge.,erator breakers in the power plant;
therefore, circuit breaker air wi 11 not be required. The high-
pressure air system wi11 be used only for governor as well a5
instrunent air. The operating pressure wi 11 be 600 to 1,000
psig depending on the governor system operating pressure.
-An air-conditioning system will be installed in the powerhouse
control room.
-Heating and ventilating wi 11 be required for the entrance build-
ing to the access shaft in the south abutment.
-For preliminary design purposes~ only one drainage and one de-
watering sump have been provided in the powerhouse. The de-
watering system wi 11 also be used to dewater the intake and dis-
charge 1 ines for the compensation flow pumps.
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(h) Surface Facilities Mechanical Service Systems
The entrance building above the power plant will have only a heat-
ing and ventilation system. The mechanical services in the stand-
by power building will include a heating and ventilation system~ a
fuel oil system~ and a fire protection system, as at Watana.
(i) Machine Shop Facilities
A machine shop and tool room will be located in the powerhouse
service bay area to take care of ma.-intenance work at the plant.
The facilities will not be as extensive as at Watana. Some of the
1 arger components wi 11 · be transported to ·watana for necessary
machinery work.
11.2 -Accessory Electrical Equipment
(a) General
The accessory electrical equipment described below includes the
following main electrical equipment:
-Main generator step-up 15/345 kV transformers;
-lso 1 &ted phase bus connecting the generator and transformers;
-345 kV oil-filled cables from the transformer terminals to the
switchyard; -
-Control systems; and
-Station service auxiliary ac and de systems.
Other equi pnent and systems described inc 1 ude grounding~ 1 ighting
system and communications.
The main equipment and connections in the power plant are shown in
the single 1 ine diagram, (Plate 70). The arrangenent of equipment
in the powerHouse; transformer gallery, and cable shafts is shown
in Plates 65 to 67. ·
{b) iransformers and HV Connections
Twelve single-phase transformers and one spare transformer will be
located in the transformer gallery. Each bank· of the three
single-phase transformers will be connected to one generator by
;. so 1 ated phase bus 1 ocated in bus tunnels. The HV terminals of
the transformer wi 11 be connected to the 345 kV switchyard by 345
kV single-phase oi.l-filled cables installed in 800-foot lony vert-
ical shafts. There will be two sets of three single-phase 345 kV
oil-filled cables installed in each cable shaft. One additional
set wi11 be maintained as a spare three-phase cable circuit in the
second cab 1 e shaft. These cab 1 e shafts wi 11 a1 so contain_ the con-
trol· and power cables between the powerhouse and the surface con-
trol room~ as well as emergency power cables from the diesel gen-
erators .at the surface to the underground facilities.
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(c)
(d)
(e)
(f)
Main Transformers
The transformers will be of the single phase, two-winding, oil-
immersed, forced-oil water-cooled (FOW) type. A total of twelve
single-phase transformers and one spare transformer wi 11 be pro-
vided, with rating and characteristics as follows:
Rated capacity:
High Vo 1 tage Winding:
Basic Insulation Level
(BIL) of HV Winding:
Low Voltage Winding:
Transformer Impedance:
Generator Isolated Phase Bus
70 MVA
345/ 3 k V, grounded Y
1300 k v
15 kV, Delta
15 percent
Isolated phase bus connections will be located between the genera-
.tor and the main transformer. The bus will be of the self-cooled,
welded alllllinl.ITl tubu13r type with design and construction details-
generally similar to the bus at the Watana power plant .. The rat-
·;ng of the main bus is as follows:
Rated current:
Short circui-~e-.-··current momentary: ·
Short circuit 4 current
s.;mmetr i ca 1 :
Basic Insulation Level (BIL):
345 kV Oil-Filled Cable
9,000 amps
240,000 crnps
150, 000 amps
150 kV
The cables will be rated for a continuous maximum current of 400
amps at 345 kV +5 percent. The cables will be of single-core con-
struction with oil flowing through a central oil duct within ~he
copper conductor. The cables will be installed in the 800-foot
cable shafts from the transfonner gallery to the surface. No
cable jointing will be necessary for this installation length.
Contra 1 Systems
The Devil Canyon power pl a'lt wi 11 be designed to be operated as an
unattended plant. The plant will be normally controlhsd ,;hraugh
supervisory control from the Susitna Area Control Center at
Watana. The plant wi 11, however, be provided with a control room
with sufficient control, indication, and annunciation equipment to
enab 1 e the plant to be operated during anergencies by one operator
in the control room.. In addition, for the purpose of testing and
commissioning and maintenance of the plant, 1oc:al control boards
will be mounted on the powerhouse floor near each unit.
Automatic 1 a ad-frequency control of the four units at Devil Canyon
will be accomplished through the central computeraided control
system located at the Watana Area Contro1 Center~
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The power plant will be provided with 11 black start"· capability
similar to that provided at Watana, to enable the start of one
unit without any power in the powerhouse or at the switchyard,
except that provided by one anergency diesel generator" After the
start-up of one unit, auxiliary station service power will be
established in the power plant and the switchyard; the remaining
generators can then be started one after· the other to bring the
plant into full output within the houre
As at the Watana ~power plant, the contto 1 system wi 11 be designed
to permit local-manual or local-automatic starting, voltage ad-
justing, synchronizing, and loading of the unlt from the power-
house control room at Devil Canyon.
The protective re1 aying system is shown in the main single line
diagram (Plate 70) and is generally similar to that provided for
the Watana power plant.
· (g) Station Service Auxiliary AC and DC Systems
( i) AC Auxiliary System
The allxiliary system will be similar to that in the Watana
power p 1 ant except, that .the swi tchyard and surface fac i 1 i-
ties power will be obtained from a 4.16 kV system supplied
by two 5/7.5 MVA, OA/FA, oil-immersed transformers con-
nected to generators Nos. 1 a.nd 4, respectivelyo The 4.16
kV double-ended switchgear will be located in the power-
house. It will have a normally-open tie breaker which will
prevent parallel operation of the two sections. The tie
breaker will close on failure of one or the other of the
incoming supplies. The 1400 hp compensation flow pumps
wi 11 be supp 1 i ed with power direct 1 y from the 4. 16 k V sys-
tem. Two 4.16 kV cables installed in the cable shafts will
supply power to the surface facilities.
The 480 V station service system will consist of a main 480
V switchgear, separate auxiliary boards for each unit, an
essential auxiliaries board, and a general auxiliaries
board. The main 480 V switchgear wi 11 be supplied by two
2000 k VA, 15,000/480 V grounded wye sealed gas dry-type
transformers~ A third 2000 kVA transformer will be main-
tained as a spare •
Two emergency diesel generators, each rated 500 kW, will be
connected to the 480 V powerhouse main switchgear and 4.16
kV surface switchboard, respectively. Both diesel gener-
ators wi 11 be located at the surface.
An uninterruptible high-security power supply will be pro-
vided for the supervis.ory computer-aided plant control
systems. a
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{ii) DC Auxiliary Station Service System
The de auxiliary system will be similar to that provided at
the wa~ana plant and will consist of two 125 V de lead-acid
batteries. Each battery system wi 11 be supplied by a
double rectifier charging system. A 48 V de battery system
will be provided for supplying the supervisory and communi-
cations systems •
(h) Other Accessory Electrical Systems
The other accessory electtical systems including the grounding
system~ lighting system, and powerhouse communications system will
be similar in general design and construction aspects to the sys-
tem described in Section 5 .. 2 for the Watan a power plant.
11o 3 -Switchyard Structures and Equipment
(a) S 1ngle Line Diagram
The electric system studies recommended a "breaker-and-a-halfn
single 1 ine arrangement. This arranganent was recommended for
reliability and security of the power system. Plate 70 shows-the
details of the switchyard single line diagram.
Devil Canyon will be the main switching station for the generation
and transmission system. Five 1 ines will emanate from this
switchyard, with three going to Anchorage and two going to Fair-
banks.
(b) rSwitchyard Equipment
The number of 345 kV circuit breakers is determined by the number
of elements to be switched such as 1 ines or in-feeds from the
powerhouse. Each breaker wi 11 be equipped with t\\0 disconnect
switches to allow safe maintenance.
The aux i 1 i ary power for the swi tchyard wi 11 be obtained from the
generator bus via a 15 -4.16 kV transformer and 4.16 kV cable.
The voltage will then be stepped down to 480 V for local use~
(c) Switchyard Structures and Layout
The switchyard layout will be based on a conventional outdoor type
design. The design adopted for this project will provide a t\\Q
level bus arrangenent. This design is commonly known as a lO'W
station profile. ·
The two-level bus arrangenent is desirable because it is less
prone to extensive damage in case of an earthquake. Due to the
lower heights, it is also easier to maintain.
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LIST OF REFERENCES
(1)
{2)
(3)
Acres Jlmerican Incorporated, Susitna Hydroelectric Project 1980-81
Geotechnical Report, prepared for the Alaska Power Authorit.Y;'
February 1982. . ·
Barton, et al., Engineering Classification of Rock Masses for the
Design of Tunnel Support •
Acres American Incorporated, Susitna Hydroelectric Project,
1980-81 Geotechnical Report, prepared for the Alaska Power
Authority, February 1982.
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TABLE A .. 1: PRINCIPAL PROJECT PARAf€TERS
Item -
,Hydrology
-Average River Flow {cfs)
-Peak Flood Inflows {cfs)
• Pl1F
• 10,000 · year
• 100 year
Reservoir Characteristics
-· Normal Maximun ~srating Level { ft)
-Mnximun Level, PHF ( ft)
-Minimum Operating Level {ft)
-Area at J'..Mll (acres)
-Length (miles}
-Total Storage {acres/feet)
-Li-ve Storage (acras/feet)
ProJect Outputs
-Plant Design Capability (MW)
-Annual Generation ( GWh)
• Firm
• Average
Dams -
-Type
-Crest Elevation ( ft)
-Crest Length { ft)
-Height; .above Foundation ( ft)
-Crest Width ( ft)
-Upstre~ Slope (H:V)
-Downatream Slope (H:V)
Diversion
-Cofferdl[lt'ls
• Type
• Upstrean Crest Elevation ( ft)
• Downstream Crest Elevation (ft)
• Maximum U/5 Water Level (ft)
-Tunnels
• ttlmber/Type
• Diameter ( ft)
• Capacity (cfs)
Outlet Facilities
-Central Structures
-Dianeter (in)
-Water Passage Diameter ( ft)
-Capacity (cfs)
Watana
7,940
326,000
156,000
92,000
2,185
2f202
2,045
38,000
48 6
9.5 X 10 6 4.4 X 10
1,020
2,630
3,450
Earth/Rockfill,
Central Core
2,210
4,100
885
35
2.4:1
2:1
Roc-kfill,
Central Core
1,545
1,472
1,536
2 '"" Circular,
concrete-lined
38
80,500
6-fixed cone valves
78
28
24!000
Devil Canyon
9,040
346:r000
165,000
61,000
1,445
1,466
1,405
7,800
26
1.1 X 1o6
0.35 X 1o6
600
z,no
3,340
Concrete Arch
(Earth/Rockfill
Saddle)
1,463 {1472)
1,650 (950)
646 (245)
20 (35)
-(2.4:1)
-(2:1)
Rockfill,
tentral Core
947
898
944
1 -Horseshoe,
concrete-lined
30
36,000
1-fixed cone valves
4-102, 3-90 a.5n.s
38,500
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TABLE A.1 (Cont'd)
Item -
Main Spillways
-Capacity (cfs)
-Control Structure
• Type
• Crest Elevation ( ft)
• Gates (H x. W, ft)
-O'lute Width (ft)
-Energy Dissipation
Emergency Spillways
-Capacity (cfs)
-Contra~ Strll:ture
• Type
• Crest Elevation ( ft) -cnw..e Width < ft)
Power Intakes
-Control S~ructures·
-Gates (H x W, ft)
-Crest Elevation ( ft)
-Maximtn Orawdown (ft)
-Capacity, percent (cfs)
Penstocks
-Number
-Type
-Diameter ( ft)
• CDncrete-lined
• Steel-lined
Powerhouses
-Type
-Cavern Size (L x W x H, ft)
-Turbine/Generator
-Speed (rpm)
-Design lhit Capability
• Nat head ( ft)
• Flow (cfs)
• Output (MW)
-Rated Unit Capability
• tet Head (ft)
• Full Gate Flow (cfs)
• Full Gate Output (MW)
• Best Gate Outpu·t ( MW)
-Transformers
• location
• Cavern Size (L x W x H,. ft)
• Number/Type
• Valtag& (kV)
• Rating (MVA)
Watana
115,000
gated ogee
2,148
3-49 X J6
144/80
Flip bucket
140,000
f),Joo channel/
fuse· plug
2200/2201.5
310/200
Multi-level, gated
4-18 X 30
2,012
140
3,870
6
Inclined/horizontal
17
15
lhdergromd
455 x 74 'x 126
6 Vertical Francis/
Synchr.
225
652
3,510
170
680
3,550.
1,089
924
~streSIJ gallery
314 X 45 X 40
9 -single phase
15/345
145
Devil Canyon
125,000
gated ogee
1,404
3-54 X 35
122/65
Flip bucket
160,000
~en channel/
fuse' plug
1464/1465.5
220
Single level, gated
1-25 X 20
1,364
50
3,670
4
Inclined/horiLOntal
20
15
tbdergromd
360 X 74 X 126
4 Vertical Francis/
Synchr.
225
542
3, 710·
150
575
3,790
656
560
q,stream gallery·
446 X 43 X 40
12 -single phase
15/~45
70
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TABLE A.1 (Cont'd)
Item
Tailrace Tunnels
-Number/Type
-Diameter ( ft)
-Surge Chamber Size ( L x W x H, ft)
-Capacity (cfs)
Watana
2 -Hoi'seshoe,
concrete-lined
34
350 X 50 X 150
22,000
Devil Canyon
1 -Horseshoe
concret~-1ined
.38
300 X 75 X 190
15,500
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2200~--~----~--~----~---+----+----+----~--~----~
J J A
18 20
2300
2200
2100
2000
1900
1800
1700
1600
1500
""" ~
1\
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\
ll \
\
M J J A S 0 N 0 J F M
2 4 6 8 10
MONTHS
MAY START
WATANA RESERVOIR
EMERGENCY ORAWDOVIN
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A
16
2300
2200
2100
2000
1900
l800
t700
1600
1500
" f\
\
1\
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s 0 N 0 J
2 4
"
~ WET 'I EAR
J
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F M A M J J
6 a 10
MONTHS
SEPTEMBER START
\
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A S 0 N D
12 t4
FIGURE A.l
16