~ ENGINEERING COMPANY CONSULTING ENGINEERS

BLACK BEAR LAKE HYDROELECTRIC PROJECT

PENSTOCK SIPHON STUDY REPORT

150 SOUTH WACKER DRIVE CHICAGO. ILLINOIS 60606-4288

TEL [312) 855-7000 CA8LE HARZENG CHICAGO TELEX 25-3540

BLACK BEAR LAKE HYDROELECTRIC PROJECT

PENSTOCK SIPHON STUDY REPORT

1. SCOPE

This report describes a study of a siphon to draw water from Black Bear Lake for the proposed 3.0 MW hydroelectric

project. This siphon would be used instead of a dam, which

would have raised the lake level to provide storage, and an

intake for water withdrawals. The study includes an estimate of

the project construction cost with the siphon system. The

siphon and upper penstock in this study have been sized for a 3

MW hydro plant, the proposed first stage of a potential 6.0 MW

development of the resource. A profile of the proposed upper penstock for the siphon concept is shown on Exhibit 1. The size

of the vertical shaft and lower penstock remain as sized in

previous feasibility studies for a 6.0 MW project.

2. DESCRIPTION

2.1. The use of a siphon to draw water from a lower water

source is practical to a depth up to 25 feet. Theoretically,

sta.ndard atmospheric pressure (76 cm of mercury) could raise water to a height of 33.9 feet at sea level. At the altitude of

Black Bear Lake (EI. 1687 MLLW datum) atmospheric pressure

equals about 31.9 feet of water. However, siphons are consid­

ered to be practical for no more than 75% of atmospheric pres­

sure. The topography of Black Bear Lake and its outlet permits

the use of a siphon to provide the intake of water for a pen­

stock to the hydro plant. This penstock, can be routed in

ground about 10 feet above the existing lake elevation, thus

providing the ability to draw the lake down about 15 feet. An

-1-

intake on the siphon penstock in the lake would be located about

5 feet below this minimum drawdown elevation to provide submer­

gence to reduce vortex formation and to protect the intake from

damage or clogging by ice. This submergence would also allow a

small margin for error in plant operation to prevent a brake in

the siphon action in the event that operation of the turbine

continues beyond the minimum drawdown elevation. In the design

proposed~ if the siphon action does break, it would take over an

hour to reestablish the siphon.

2.2. The proposed siphon system would consist of the fol­

lowing main equipment: two vacuum pumps, electric motor driven,

rated 450 cfm at 22 inches of mercury (equals 25 feet of water)~

vacuum tank1 a seal water supply pump~ and unit heaters for a

small building enclosing the vacuum pump equipment. Piping

would consist of the connections from the penstock to the vacuum

tank, from the tank to the vacuum pumps and. for seal water,

from the lake to the vacuum pumpso Power for operation of the

siphon system equipment would be provided from the powerhouse

via an interconnection line as described in the Feasibility

Report Update 0

2.3. The proposed siphon system would be designed to

start the siphon action at any lake level down to the lowest

designed drawdown level. The vacuum tank and pumps would be

located on the high point of the upper penstock approximately

360 feet downstream from the intake. This point would be about

50 feet downstream of the location of the dam axis shown in the

February 1987 Feasibility Report Update.

-2-

The operating procedure would be as follows:

1. To fill the penstock with water, the turbine

inlet valve and by-pass valve at the powerhouse

would be closed. An air inlet valve on the

vacuum tank would be closed. The intake valve at

the vacuum pump would be opened and the pump

started to evacuate air from the tank and pen­

stock. After the penstock is filled with water,

the vacuum pump intake valve would be closed and

the turbine inlet or powerhouse by-pass valve

opened. With the turbine inlet valve open, the

turbine can be started and siphoning action would

commence.

2. To dewater the penstock, the turbine would be

shut-down and the by-pass valve opened. The air

inlet valve on the vacuum tank would be opened to

allow air to enter the penstock and water to

drain toward the powerhouse and through the by­

pass. The upstream portion of the penstock would

drain to the lake. Opening the air inlet valve

will break the siphon and will shut-off flow in

the penstock which eliminates the need for an

intake gate or valve at the entrance of the pen­

stock.

2.4. The proposed intake would consist of a cylindrical

trashrack formed by vertical steel bars supported by horizontal,

bars bent into rings, with a horizontal flat circular plate on

top of the cylinder serving as a velocity cap. The cylindrical

intake trashrack would be welded to a miter reducing bend of 90

degrees which would be welded to the steel penstock. The intake

-3-

would be located in Black Bear Lake where the natural water

depth is 30 feet. Soundings of the lake show this depth to be

about 182 feet from the lake shore near the lake's outlet creek.

The discharge required for 3.0 MW of generating capacity is 32

cfs (with net head of approximately 1,300 feet). To obtain an

approach velocity of one foot per second the size of the cylin­

drical intake would be 3'-6" in diameter and 3 feet high. Sixty

3/8 inch thick vertical bars equally spaced on the circumference

of t.he supporting rings would result in openings of 1.824" wide.

The height of the intake with miter reducing bend would be 7

feet above the center line of penstock. With a minimum submer­

gence of 5 feet the maximum drawdown of the lake would be about

15 feet below the present natural lake elevation. The natural

lake is at elevation 1687 and the penstock centerline at the

miter bend would be at approximately El. 1660. This would pro­

vide a lake drawdown to El. 1672.

2.5. In the Feasibility Report Update of February 1987,

the water conduit system for the 6.0 MW alternative consisted of

the following:

a) An upper steel penstock of 48 inch diameter and about

325 feet long,

b) A vertical concrete lined shaft of 48 inch diameter about 1237 feet deep, and

c) A lower steel penstock of 30 inch diameter about 2,800

feet long.

The computed total head loss for this system is 106.84 feet for

64 cfs and 33.24 feet for 32 cfs. Replacing the dam (as shown

in the feasibility report update) with a siphon will increase

-4-

the upper penstock length by 310 feet~ The increase in length

consists of 128 feet from the dam axis location to the lake bank

and 182 feet from bank into lake at penstock intake. It is

proposed that the upper penstock for the 3.0 MW siphon alterna­

tive be sized to have approximately the same total head loss as

the 6.0 MW alternative (at maximum plant discharge) but without

changing the shaft and lower penstock diameterso On this basis

the diameter of the nearest standard size pipe for the upper

penstock would be 20 inches. The head loss in the 20 inch 0.00

upper penstock j 48 inch 1.0. shaft and 30 inch 0.0. lower pen­

stock for 32 cfs flow is estimated to be about 76 feeto At

minimum lake Elo 1672 the net head for the plant would be 1335

feet. For future expansion of the plant to 6.0 MW, the upper

penstock would be replaced by a larger pipe, but the shaft and

lower penstock would not require change.

2.6. Approximately 182 feet of pipe would be placed under­

water at the upstream end of the upper penstock. It is proposed

that this pipe be protected by dumping rock fill underwater to a

one foot thickness over the top of the pipe. A layer of rip~rap

would be placed over the rockfill. This protection would pre­

vent damage to the pipe by ice with lake drawdown and possible

erosion of pipe foundation by wave action in the vicinity of the

pipe. During project operation, the lake bed adjacent to the

pipe and its p~otective material should be inspected when the

lake is drawn down and rockfill/r ip-rap placed 'if necessary. In

the event of failure of the power supply or control lines from

the powerhouse to the siphon equipment, an emergency portable

generator could be flown by helicopter to the siphon site.

2.7. The total internal volume of the water conduit sys­

tem, as proposed, equals 30,607 cubic feet. With the 450 CFM

-5-

vacuum pump capacity proposed, the time required to evacuate all

air in the conduit is 68 minutes.

2.8. Black Bear Lake has not been surveyed below its water

surface~ therefore, its water volume below the surface is not

known exactly. An estimate of its volume can be made by extra­

polating the reservoir area/volume curves. Extrapolation from

natural surface at EIQ 1687 to EI. 1672 gives a volume of 2650

acre-feet. Since there is some uncertainty about the under

wate~ topography, it is recommended that a usable storage of

2000 acre-ft be assumed for the 15 feet of drawdown. Based on

reservoir operation studies performed for the 3.0 MW B.W.EL.

1595 alternative (2000 acre-feet of storage) the estimated 3.0

MW siphon intake alternative average annual energy generation

would be about 18,000 MWh.

2.9. The environmental impacts of this alternative include the following:

a) Shores not previously or naturally exposed will be

exposed.

b) Fish habit will be reduced when the lake is drawn down

during winter. There may also be a drawdown during

late summer in dry years.

c) Lake outflows, by way of the creek, will be eliminated

during drawdown.

d) The distance from the Forest Service cabin to the lake

shore will increase during winter and some late summer

periods.

-6-

3. COST ESTIMATE

Based on the cost estimate for the 3.0 MW H.W.EL. 1695 Stage I alternative presented in the Feasibility Report Update,

the construction cost of the project has been estimated for the

3.0 MW generating plant with the siphon system. This estimated

cost is for the complete power generating plant but without any transmission lines from its substation. The estimated transmis­

sion line costs for several options of serving load demand cen­

ters are shown in Table 1II-10 on page 1II-27 of the February

1987 Feasibility Report Update. The elimination of the dam and

its replacement by a siphon system, reduces the work required in

the vicinity of Black Bear Lake which reduces mobilization and

logistics costs.

for these changes.

contractor's indirect costs have been revised

The changes in quantities for construction

consist of elimination of all dam work, revision of upper pen­

stock steel, excavation, backfill and bedding, underwater place­

ment of pipe and its protection. Quantities for the vertical

shaft, lower penstock, powerhouse, access roads and substation

are unchanged. Costs have been estimated for the siphon system

equipment and a small building to protect this equipment. A

summary of the estimated construction cost is shown in the table

below. A detailed estimate is shown on Exhibit 2.

-7-

Item No.

SUMMARY OF COST ESTIMATE January 1986 Price Level

Description Estimated Cost

330 331 332 333 334 335 336 353

Land & Land Rights $ 73,000 630,000

7,499,000 641,000 584,000

57,000 560,000 196,000

1,100,000

Powers tat ion & Improvements Reservoir, Dams & Waterways TUrbine & Generator Accessory Electrical Equipment Miscellaneous Mechanical Equipment Access Road Substation Equipment & Structures Mobilization & Logistics

Subtotal Direct Cost Contingency Allowances Civil 15%

Equip. 10%

Total Direct Cost Engineering & Administration 17.5% Total Estimated Construction Cost

-8-

11,340,000 1,480,000

150,000

12,970,000 2,270,000

$15,240,000

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DATE MAR 06 1987 HARZA ENGINEERING COMPANY I3MWSF1284Cl FEASIBILITY ESTIMATE (LFC/RAM D) ~ROJECT 3.0 MW. HWL EL 1687. SIPHON INTAKE

ITEM DESCRIPTION QUANTITY UNIT UNIT

PRICE TOTAL PRICE

----------------------------------------------330.

LAND 8. LAND RIGHTS 1 LS 730013.00 73.000

--------------------------------------------

SUBTOTAL. PAGE 73.000

SUBTOTAL - A/c 330. LAND 8. LAND RIGHTS 73.000

., ,

ATE MAR 06 1987 HARZR ENGINEERING COMPANY 3MWSF1284Cl FEASIBILITY ESTIMATE (LFC/RAM D) ROJECT 3.0 MW. HWL.EL 1687. SIPHON INTAKE

TEM DESCR IPTION QUANTITY·UNIT UNIT

PRICE TOTAL PRICE

,-----------------------------------,---------------

330.5 MOB ILIZATION 8. LOG ISTICS 1 LS 1100000.00

._------------------------------------

;UBTOTAL. PAGE 2

SUBTOTAL - A/c 330.5 M08ILIZATION 8. LOGISTICS

1.100.000

lATE MAR 06 1987 HARZA ENGINEERING COMPANY 3M\.JSF1284C1 FEASIBILITY ESTIMATE (LFC/RAM D) -ROJECT 3.0 MW. HWL EL 1687 ~ S I PHON INTAKE

UNIT TOTAL TEM DESCRIPTIOI'l QUANTITY UN IT PRICE PRICE ._---------------------------------

331. POWERSTATION & IMPROVEMENTS

331.1 POWERHOUSE

331. 11 DIVERSION & CARE OF WATER 1 LS 350a0.00 35,000

rl 331. 12 ,-

CLEARING. HEAVY 3 AC 105a0.00 .' 31.500 \"()

331. 13 EXCAVAT I ON. TALUS 1750'CY 10.50 18.375

331. 14 FILL 750 CY 8.80 6.600

331.15 SUBSTRUCTURE CONCRETE 345 :CY 530.00 182.850

331.161 SUPERSTRUCTURE CONCRETE 65 CY 790.00 51.350

331. 162

~ MASONRY 470 SF 20.50 9.635

331. 163 ~ INSULATED METAL ~~ PANELS 3700 SF 7.05 26.085 ~~

~--------------------------------------- ~f\, UJ ;UBTOTAL. PAGE 3 361.395

ATE MAR 86 1987 HARZA ENGINEERING COMPANY 3MWSF1284Cl FEASI8ILITY ESTIMATE CLFC/RAM D) ROJECT 3.8 MW. HWL EL 1687. SIPHON INTAKE

TEM DESCRIPTION QUANTITY UNIT UNIT

PRICE TOTAL PRICE

---------------------------------------------331.164

ARCHITECTURAL TREATMENT

331. 165 STRUCTURAL STEEL

331. 166 INSULATED METAL ROOF

331.167 HVAC 8. PLUMBING

331. 168 MISCELLANEOUS METALS

331.2 STATI ON YARD

331.21 FILL

331.22 CRUSHED ROCK SURFACING

331. 23 CHAIN LINK FENCE 8. GATE

331.24 CONCRETE FOUNDATION PADS

;UBTOTAL. PAGE 4

1 LS 5558a.08 55.58a

58a88.'LB 2.75 137.588

3988 SF 6.45 25.155

1 LS 2588a.08 25.888

2888 LB 2.75 5.58a

258 CY 8.80 2.2813

68·CY 25.a8 1.588

168 LF 32.58 5.288

28.CY 54El. a8 :. 18.888

---------------

SUBTOTAL - A/c 331. POWERSTATION 8. IMPROVEMEHTS

268.355

629.750

, )

lATE MAR 06 1987 HARZA ENGINEERING COMPANY 13MWSF1284C1 FEASIBILITY ESTIMATE (LFC/RAM D) 'ROJECT 3.0 MW. HWLEL 1687. SIPHON INTAKE

ITEM DESCRIPTION QUANTITY ,UNIT

332. RESERVOIRS. DAMS. 8. WATERWAYS

332.3 WATERWAYS

332.31 INTAKE

332.311 CONCRETE - STRUCT. (BUILDING EQUIPMENT Be FOUNDATIONS) 7 CY

332.312 TRASHRACK 8. BEND 930 'LBS

332.313 BUILDING 240 SF

332.314 VACUUM PUMPS. CONTROLS. TRANSFORMER. AND MISC. EQUIPMENT 1 LS

332.315 POWER SUPPLY Be CONTROL LINES 1 LS

332.32 PENSTOCK

332.321 UPPER PENSTOCK

332.3211 EXCAVATION

332.32111 EXCAVATION. OVERBURDEN 360CY

UNIT PR ICE .'

875.00

3.70

55.50

100000.00

73500.00

13.00 ---------------------------------------------)UBTOTAL. PAGE 5

TOTAL PRICE

6.125

3.441

13.320

100.000

73.500

4.680

201.066

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~\) ~ .~ , lI'tK \ ... \'K ~f\l

rATE MAR 86 1987 HARZA EHGIHEERIHG COMPAHY 3MWSF 1284C 1 FEAS IB IL lTV ESTIMATE (LFC/RAM D) 'ROJECT 3 '.8 MW. HWL EL 1687. S I PHOH I HTAKE

TEM DESCRIPTIOI'! QUAHTITVUHIT UHlT

PRICE TOTAL PRICE

._----------------------------------------------332.32112

EXCAVATIOH. ROCK 488'CY 57.58 23.888

332.3212 BACKFILL 698 CV 16.58 11. 385

332.3213 BEDDIHG 35;CV 45.58 1.593

332.3214 COHCRETE THRUST 8LOCKS & SADDLES 6 CV 11513.88 :. 6.988

332.3215 GRAVEL FILL (FOR PEHSTOCK SUBMERGED PORTIOH) 388,:CV 42.58 , 12.758

332.3216 RIPRAP (FOR PEHSTOCK SUBMERGED PORTIOH) 288 :CV 62.88 12.488

332.322 LOWER PEHSTOCK

332.3221 EXCAVATIOH

332.32211 EXCAVATIOH. TALUS 3988 CV 19.88 74.188

.. _---------------------------------------------------

;UBTOTAL. PAGE 6 142.128

~

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lATE MAR 136 1987 HARZA ENGINEERING COMPANY 3MWSF1284Cl FEASIBILITY ESTIMATE (LFC/RAM D) 'ROJECT 3. a MW. HWL EL 1687. SIPHON INTAKE

TEM DESCRIPTION QUANTITY:UNIT

332.32212 EXCAVATI ON. ROCK

332.3222 BACKFILL

332.3223 BEDDING

332.3224 CONCRETE THRUST BLOCKS 8. SADDLES

332.323 PENSTOCK SHAFT

332.3231 EXCAVATION

332.3232 CONCRETE LINING

332.324 TUNNEL EXCAVATION 8. SUPPORT

332.325 PENSTOCK STEEL

332.3251 UPPER SITE POWER CONDUIT

ruBTOTAL.PAGE 7

411313 CY

18aa"CY

15 CY

12413 ~ LF

73a"CY

166aLF

335aa"LB

UNIT PRICE

8.813

25.1313

985.1313 ". "

TOTAL PRICE

36.13813

45.131313

14.775

11513.1313 839.51313

213013.1313" 3.3213.131313

3.135 1132.175

6.1331.5313

r-"

lATE MAR 06 1987 HARZA ENGINEER ING COMPANY 3MWSF1284Cl FEASIBILITY ESTIMATE (LFC/RAM D) 'ROJECT 3.0 MW. HWL EL 1687. SIPHON INTAKE

TEM DESCR IPTIOH QUANTITY;UHIT UNIT

PRICE .. TOTAL PRICE

._-------------------------------------------------

332.3253 LOWER SITE POWER CONDU IT

332.326 TAILRACE & STREAM CHANNEL IMPROVEMENT

332.3261 EXCAVATIOH. TALUS

362000.LB 3.0S

1900CY 10.S0

._------------------------------------

;UBTOTAL. PAGE 8

1.104.100

19.9S0

1. 124.0S0

SUBTOTAL - A/C 332. RESERVOIR. DAMS. & WATERWAYS. 7.498.774

DATE MAR 06 1987 HARZA ENGINEERING COMPANY I3MWSF1284C1 FEASIBILITY ESTIMATE (LFC/RAM D) PROJECT 3.0 MW, HWL EL 1697, SIPHON INTAKE

ITEM DESCRIPTION QUANTITY UNIT

333. TURBINE & GENERATOr.

333.1 TURBINE Co GOVERNOR

333.2 GENERATOR

SUBTOTAL, PAGE 9

1 EA

1 EA

SUBTOTAL - O/C 333. TURBINE & GENERATOR

UNIT PRICE

39S8e8.88

253888.88

TOTAL PRICE

399,888

253,888

DATE MAR 06 1987 HARZA ENGINEERIHG COMPAHY " I3MWSF1284C1 FEASI8ILITY ESTIMATE (LFC/RAM D) PROJECT 3.0 MW. HWLEL 1687. SIPHON INTAKE

ITEM DESCR I PTI ON QUANTI TV ;UN IT

334. ACCESSORY ELECTRICAL EQUIPMENT

334.1 f:lCCESS. ELEC. EQPT. 1.LS

334.2 SUPERV'SRY CONTROLS 1 LS

334.3 COMMUN I Cf:lTI ONS l' LS

UNIT PRICE

.390000.00

.' 1250013.00

69000.00

TOTAL PRICE

390.El00

125.000

69.000

------------------------------------------------SUBTOTAL. PAGE 10 584.000

SUBTOTAL - A/C 334. ACCESSORYELECTRICALEQUIPMEHT 584.000

c' {~

~ATE MAR 1116 1987 HARZA EHGIHEERIHG COMPAHY :3MWSF1284C1 FEASIBILITY ESTIt1HE (LFCI'RAM D) -ROJECT 3.111 MW. HWL.EL 1687. SIPHOH INTAKE

:TEM DESCRIPTIOH QUAHTITY:UHIT

335. MISCELLAHEOUS MECHANICAL EQUIPMEHT

335.1 POWERHOUSE CRAHE

335.2 MISC. EQPT.

1 LS

1 LS

._------------------------------- -----

iUBTOTAL. PAGE 11

UHIT PRICE

48111111111.111111

955111.111111

SUBTOTAL - A/C 335. MISCELLAHEOUS MECHANICAL EQUIP.

TOTAL PRICE

48.111111111

9.55111

57.55111

57.55111

DRTE MAR a6 1987 HARZA EHGINEERING COMPANY " I3MWSF1284Cl FEASIBILITY ESTIMATE (LFC/RAM D) PROJECT 3.a MW. HWL EL 1687. SIPHON INTAKE

ITEM DESCR I PTI ON QUANTI TY :UH IT

336. ACCESS ROAD 1 LS

SUBTOTAL. PAGE 12

SUBTOTAL - A/c 336. ACCESS ROAD

UNIT PRICE

TOTAL PRICE

560a0a. aa.· 56a. €lea

56a.aaa

56a.aaa

~TE MAR B6 1987 HRRZR ENGINEERING COMPRNY 3MWSF1284C1 FERSIBILITY ESTIMATE (LFC/RRM D) ROJECT 3.B MW~ HWL EL 1687~ SIPHON INTRKE

TEM DESCRIPTION QURNTITY:UNIT

353. SUBSTRTION EDUIPMENT 8. STRUCTURES

353.1 TRRNSFORMERS

353.2 SWITCHES~ BRERKERS~ 8. MISCELLRNEOUS

1 ER

1 LS

UNIT PRICE

6B5BB.BB ..

135BBB.BB .

TOTRL PRICE

SUBTOTRL - n/C 353. SUBSTRTION EQUIP. 8. STRUCTURES 195~5BB