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Mailing Address: Water Resources Data System

University of Wyoming, Dept 3943 1000 E University Avenue

Laramie, WY 82071

Physical Address: Wyoming Hall, Room 249 University of Wyoming

Laramie, WY 82071

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LITTLE SNAKE RIVER WATER MANAGEMENT PROJECT

EXECUTIVE SUMMARY

Prepared for

WYOMING WATER DEVELOPMENT COMMISSION

November 1984

.&-Stone & Webster Engineering Corporation

Approved:


EXECUTIVE SUMMARY

Prepared for WYOMING WATER DEVELOPMENT COMMISSION

November 1984

tOt.

14980.07 - H(D)-l

Project Engineer Division Head

ering Management

Copyright 1984 Stone & Webster Engineering Corporation

Denver, Colorado STONE Be WEBSTER A

No. of Copies

1

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INTERNAL DISTRIBUTION

Recipient

Director of Engineering, Boston - Philip A. Wild

Engineering Manager, DOC - R. J. Conlon

Hydraulic Division Manager - D. L. Matchett

Geotechnical Division Manager - D. L. Matchett

Technical Information Center, Boston

Technical Information Center, DOC

D. H. Rutherford

G. C. K. Grinnell

R. Mascolo

R. D. Reynolds

M. L. Barningham

Western Water Consultants, Laramie Wyoming

Western Research Corp., Laramie, Wyoming

Robert Jack Smith and Associates, Rawlins, Wyoming

W. W. Reedy, Denver, Colorado

Dr. R. B. Peck, Albuqurque, New Mexico

STONE Be WEBSTER A


EXECUTIVE SUMMARY

PREPARED FOR

WYOMING WATER DEVELOPMENT COMMISSION CHEYENNE, WYOMING

WALTER J. PILCH Chairman

JAMES NOBLE Vice Chairman

WILLIAM J. KIRVEN, JR. Secretary

LEWIS FREUDENTHAL

KENNETH KENNEDY

J.W. WES' MYERS

WILLARD C. RHOADS

MERL RISSLER

NELSON E. WREN, JR.

MICHAEL K. PURCELL

Administrator

PREPARED BY

.&. Stone & Webster 'JI"i Engineering Corporation

DENVER, COLORADO

NOVEMBER 1984

STONE Be WEBSTER A

INTRODUCTION

This document provides a Summary of the study results on the Little

Snake River Water Management Project (LSRWMP) located in South Central

Wyoming as conducted by Stone & Webster Engineering Corporation (SWEC)

under the direction of the Wyoming Water Development Commission (WWDC).

More detailed information on the study can be found in the Technical

Summary Report dated November 1984.

The Wyoming Legislature by W.S. 41-2-121 authorized the WWDC to

prepare a report recommending a project configuration, providing a schedule

for implementing the project and project components, and furnishing an

estimate of construction cost for development of the LSRWMP. SWEC was

commissioned to examine project alternatives which best satisfy the

conditions set forth in legislation, comply with criteria established by

the Commission, and best conform with sound engineering and economic

considerations. Three major development alternatives were to be considered:

• Alternative C A gravity collection system extending the

Cheyenne Stage III collector across the Continental Divide into a

regulating reservoir on Sage Creek with a transmission pipeline

to the North Platte River.

• Alternative D - A storage reservoir(s) in the Little Snake River

Basin and a trans-basin pipeline with pumping stations to deliver

water from a diversion point near Baggs to the North Platte River

near Sinclair.

• Fish Creek Alternative - A collection system as in Alternative C

but storing the water in Fish Creek Reservoir located on the west

side of the Continental Divide and transporting the water by

tunnel or pumping into the North Platte River Basin.

The firms of Western Water Consultants, Inc. of Laramie and Sheridan

Wyoming, Western Research Corporation of Laramie, Wyoming, and Robert Jack

Smith and Associates, Inc. of Rawlins, Wyoming were a part of the study

team. Dr. Ralph B. Peck and W. W. Reedy served in an advisory capacity.

-1-STONE Be WEBSTER ..

LEGISLATIVE REQUIREMENTS

The major requirements and considerations which were set down in

legis lation regarding the development of the LSRWMP, located as shown on

Figure 1, are summarized as follows:

1. Storage of at least 10,000 acre-feet on Savery Creek.

2. Storage of at least 50,000 acre-feet for use in the Little Snake River Basin.

3. A collection and the North Platte purposes.

conveyance system for transporting water into River Basin for municipal and industrial

4. Groundwater should not be considered to be an alternative to the Stage III water supply. There should be no condemnation of agricultural water rights.

5. Enlargement of Seminoe Reservoir or alternative North Platte River storage should be considered.

6. The first phase of the study should recommend one of the two basic Alternatives, C or D.

In that Alternative C when originally conceived did not provide any

storage on Savery Creek or in the Little Snake Basin, the most recent

legislation required that in-basin storage be added to this scheme of

development.

EVALUATION OF PROJECT COMPONENTS

At the beginning of the study, SWEC examined the major alternative

development plans to identify the basic components. These components are

shown on Figure 2 and described as follows.

Two collector systems constructed so as to gather and convey water

from melting snow fields high on the western s lope of the Continental

Divide were considered. 'They are:

1. The Sage Creek Collector which runs from the Stage III collection area in a northwest direction until its gravity pipeline crosses the Continental Divide and into the Sage Creek Reservoir.

-2-STONE 8: WEBSTER A

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LOCATION MAP

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ICALE

LITTLE SNAKE RIVER

STUDY AREA

FIGURE

STONE Be WEBSTER A

GREAT DIVlDE BASiN

,~~

~ SAGECREEV GRAVITY LIN

-/ f \

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\ STAGE III '/7""'~"" COLLECTION IAREA

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( ~r~ ...

U'PPER SAVERY RESERVOIR~~ '-l.. ~.. . 1

I

o 5 ----- 10

SCALE IN MILES

15

HOUTT NATIONAl

20


LOCATION OF PROJECT COMPONENTS FOR ALTERNATIVE PLANS

FOREST

OREST

FIGURE 2

~ Stone & Webster Engineering Corporation

2. The Fish Creek Collector - which has an alignment slightly lower

vertically than the Sage Creek System and flows by gravity into

the Fish Creek Reservoir on the west side of the Continental

Divide.

Six storage sites which are capable of providing annual storage of

spring snow melt runoff were considered. Five are located in the Little

Snake Bas in. They are:

1. Fish Creek Dam on Savery Creek

2. Upper Savery Dam on Savery Creek

3. Sandstone Dam on Savery Creek

4. Pot Hook Dam on Slater Creek

5. Three Forks Dam on Little Snake River

6. Sage Creek Dam on Sage Creek, tributary to North Platte River

Transportation systems associated with the LSRWMP are the features

which convey water by gravity flow or by pumping from storage or diversion

points to delivery points in the North Platte River Basin.

Four general transportation routes were considered. They are:

1. Fish Creek to Sage Creek

2. Sage Creek to North Platte River at Overland Crossing

3. Sage Creek to Rawlins to North Platte River at Sugar Creek

4. Baggs to Rawlins to North Platte River at Sugar Creek

The feasibility of incorporating hydrogeneration to benefit the

project was considered. Since flood control and recreational development

were outside the responsibilities of the WWDC, they were not included in

the studies.

By evaluating each of the project components on a comparable basis,

the relative effectiveness of separate components were assessed.

Combinations of project components were assembled to provide various plans

that supply water to both the Little Snake River and the North Platte River

basins.

Some of the project components were judged to be mutually exclusive,

that is, construction of one would eliminate the need for the other. These

were:

Fish Creek Dam and Sage Creek Dam

Tunnel and pipeline from Fish Creek to Sage Creek

-5-STONE Be WEBSTER ..

Pipeline from Sage Creek to North Platte River at Overland Crossing and pipeline from Sage Creek to North Platte River via Rawlins and Sugar Creek

Upper Savery Dam and Sandstone Dam

Although the Baggs Diversion/Pipeline is an alternate to the

trans-basin collection systems, it can also provide water to other areas in

south central Wyoming if additional storage in the Little Snake River Basin

is provided.

Hydrology

The major portion of the flow in the Little Snake River and its

tributaries comes from snowmelt runoff in the months of May and June each

year. Those tributaries with headwaters near the Wyoming-Colorado border

in the Sierra Madre mountains contribute significantly more flow to the

Little Snake River than do those in the northern area near the Great Divide

Basin. For institutional and other reasons water could be passed through

or over the Continental Divide only at the north end of the proposed

collector system. Therefore, it was concluded that staged development of a

collector system would be neither practical nor economical and it would be

necess'ary to construct a collector system from the Stage III collection

area, carrying water northward into the North Platte Basin as a single

project. The Fish Creek Dam as a storage site for in-basin use was not

feasible without the added water produced by a collector system.

Construction of a collector system for in-basin use alone was not cost

effective.

The Sage Creek Collection System would develop an average yield of

38,300 acre-feet while the Fish Creek Collection System being slightly

lower with a larger drainage area could develop 47,600 acre-feet.

Simulated Operations Studies were conducted to determine the most

effective size of the various reservoirs, and to assess the effect of

storage on yields. The selected reservoir capacities and average yields,

taking into account the Stage III Fish Creek Collection system depletions,

are tabulated below. Firm yields shown are computed on the basis of using

a 50 percent agricultural demand, which is one-half cfs per 70 acres of

water right acreage (approximately one cfs per 70 acres of presently

irrigated acreage).

-6- STONE Be WEBSTER ..

Upper Savery

Sandstone

Pot Hook

Three Forks

Hydraulics

Reservoir Capacity

(acre-feet)

40,000

52,000

61,500

100,000

Average Firm Yield Yield

(acre-feet/yr.) (acre-feet/yr)

23,500 16,000

38,500 25,900

33,500 32,300

84,500 73,500

Project components governed by hydraulic design considerations were

sized for comparable operation criteria wherever possible. For water

exported via the Fish Creek and Sage Creek Collection Systems it was

considered that all available water could be used in the North Platte River

basin, since export capability appeared to be in the range of the

preliminary forecasted needs in the year 2030. The smaller yield of the

Sage Creek System would be totally utilized sooner than the Fish Creek

System.

While the addition of hydrogeneration to the project looked

potentially feasible at Three Forks, Sandstone and Sage Creek Dams, the

benefits from hydro installations, were not large enough to change the

general ranking of the preferred plan of development.

Geotechnical Aspects

Geotechnical evaluation of the six damsites, two collectors, and four

pipeline/tunnel conveyance systems was based on available information from

previous studies and field reconnaissance. Subsurface information was

available for four of the six damsites, Fish Creek, Upper Savery, Sandstone

and Pot Hook. With only one boring at each site, Three Forks and Sage

Creek sites were evaluated primarily from surface geologic information.

Resul ts of the geotechnical evaluation were incorporated into the

design concepts for the various features and are reflected in the

comparative cost estimates for each.

Review of the geotechnical aspects of the dams was provided by

Dr. Ralph Peck, an internationally recognized expert in the area of

embankment dams and geotechnical engineering.

-7- STONE Be WEBSTER A.

Environmental Considerations

Environmental studies were limited to the identification of possible

environmental problems of a magnitude and/or complexity that would severely

impair or prohibit the development of the proposed LSRWMP. Such problems

are not evident at this time. Necessary coordination with appropriate

agencies regarding the preparation of an Environmental Impact Statement

eElS) is recommended as a part of the WWDC Level III Phase II project

work. The EIS process will require the evaluation of project alternatives,

including the consideration of no action and utilization of ground water.

PLAN COMPARISONS

Near the beginning of the study, a methodology was developed that

would provide a framework for making comparisons in a thorough and

systematic manner. A progressive evaluation and screening process was

used, first to compare the various components and alternatives, and then to

eliminate those that appeared less attractive. Comparisons were subjective

with respect to environmental and institutional factors. Engineering

features of the components were developed to approximately the same

standards of constructability and safety. Costs then become the

determining factor in selecting between components that would serve the

same function, and ultimately in selecting the preferred plan.

Based upon evaluation of the Legislative, Environmental,

Hydrological, Geotechnical and Institutional considerations, the following

conclusions were reached:

• Fish Creek Reservoir is not a practical site considering

in-basin storage only.

• Pot Hook and Three Forks damsites are wholly or partially in

Colorado. Because of the significant additional legal and

administrative activities considered necessary to construct

either of these storage facilities, it is believed prudent not

to utilize them as near term project developments.

• Upper Savery damsite requires special design criteria to

accommodate the poor foundation conditions at that site.

-8- STONE Be WEBSTER A

COST ESTIMATES

Comparative cost estimates were developed for the various project

components which were identified in the study. They are summarized on

Table 1.

The least cost in-basin storage facility, Pot Hook, is located in

Colorado. Sandstone is the least costly site in Wyoming.

The Fish Creek Collection System is the most economical trans-basin

diversion system, due to its greater yield and lower cost. The free flow

or tunnel alternative from Fish Creek reservoir through the Continental

Divide, although slightly more costly, is preferred over the pumping

alternative primarily due to its increased reliability and flexibility.

The Baggs Diversion alternative when considered along with the least

costly in-basin Reservoir (Pot Hook) is not cost competitive with the Fish

Creek Collection System.

A summary of the estimated costs of six plans developed by selecting

various components of in-basin and trans-basin diversion facilities is

shown on Figure 3. The least costly plan, Plan 2, combines the Fish Creek

Collection System with Pot Hook Reservoir. Plan 2 requires dedication of a

portion of the collector system water to in-basin needs to satisfy

legis lative requirements and therefore, reduces water yield to the North

Platte River basin. It also requires the involvement of Colorado interests

to develop the in-basin Pot Hook reservoir.

Plan 1, which combines the Fish Creek Collection System with

Sandstone Dam and Reservoir becomes, therefore, the preferred plan for

development of the Little Snake River water resource.

-9 - STONE Be WEBSTER A

TABLE 1

Project Component Cost Summary

In-Basin Storage

Upper Savery Sandstone Pot Hook Three Forks

Trans-basin Diversion (45,000 acre-feet/yr.)

Fish Creek Collector Fish Creek Dam & Reservoir Tunnel & Pipeline to N. Platte River

Fish Creek Collection System

Unit Cost of Water = $3800/acre-foot

Pumps & Pipeline Pot Hook Dam

Baggs Diversion Pumping Scheme


Trans-basin Diversion (33,300 acre-feet/yr.)

Sage Creek Collector Sage Creek Dam & Reservoir Pipeline to North Platte River

Sage Creek Collection System


Pumps·& Pipeline Pot Hook Dam

Baggs Diversion Pumping Scheme


-10-

Estimated Cost ($ X 1000)

$ 65,400 61,300 26,300 73,900

94,300 26,400 50,200

$170,900

165,700 26,300

$191,000

183,500 24,600 27,400

$235,500

142,600 26,300

$168,900

STONE 8: WEBSTER A

IN BASIN STORAGE

THREE FORKS POTHOOK SANDSTONE

DAM AND DAM AND DAM AND RESERVOIR RESERVOIR RESERVOIR

COMPONENT ESTIMATED COSTS 73,900 26,300 61,300

($ x 1000)

PLAN t 61,300

PLAN 2 26,300

PLAN 3 26,300

PLAN 4 73,900

PLAN S 61,300

PLAN 6 73,900 61,300

TRANS - BASIN DIVERS 10 N

PUMPING COLLECTION SYSTEMS PIPELINES

IAGa CONYEYANCE PLAN

DIYERSIOtI TO COLLECTORS RESERYOIRS PIPELINES ESTIMATE

N. P\.ATTE R. ilATTL! CREEK COSTS

45.000 A/ft. 'ISH CREEK 'ISH CREEK

($ X 1000) -,tsH CREEK -N. Pt.ATTE R.

I6S,700 94,300 26,400 50,200

94,300 26,400 50,200 232,200

94,300 26,400 50,200 197,200

16S,700 94,300 26,400 312,700

16S,700 94,300 26,400 360,300

16S,700 2S3,300

16S,700 300,900

[J PREFERRE 0 PLAN

FIGURE 3

STONE Be WEBSTER ..

• o o .. • N -C

RECOMMENDED PLAN OF DEVELOPMENT

The preferred plan of development for the Little Snake River Water

Management Project consists of three prime components as shown on Figure

4. The plan provides for:

1. Sandstone Dam & Reservoir - In-basin storage for the Savery Creek and Little Snake River drainages.

2. Fish Creek Collection System - Out-of-basin transfer of water to the North Platte River drainage.

3. Baggs Diversion Pipeline with Pot Hook and/or Three Forks Reservoir - Future expansion facilities that provide flexibility to use the full allotment of Wyoming Compact water as a long-range plan for ultimate development of the Little Snake River basin waters.

SCHEDULE

The recommended LSRWMP schedule of development as shown on Figure 5

is to proceed immediately with the in-basin storage facility Sandstone Dam

and Reservoir. It is estimated that water storage could be achieved in the

spring of 1990.

Evaluation of the results of the WWDC work in progress that will

impact the Fish Creek Collection System should be continued. Preparation

of a conceptual design layout for the collector system with possible

alternatives should be undertaken. Pipeline routing to the North Platte

using the stream bed of Sage Creek for portions of the conveyed water as

well as a joint pipeline with the city of Rawlins should be investigated.

Such studies will provide the necessary data with which to evaluate the

environmental concerns and define field data collection to comply with

permitting requirements.

The ultimate plan of development should be pursued as necessary to

provide continuing dialog and cooperation with Colorado that will be

beneficial to the future development of Wyoming Compact water.

-12-STONE Be WEBSTER A

BUDGET

The budget for the recommended plan of development should anticipate

the permitting and design efforts for Sandstone Dam and Reservoir in 1985

and 1986, with construction expenditures beginning in 1987. Funding for

the further definition of the Fish Creek Collection System impacts and

utilization should be considered during the period 1985-1990.


"

GREAT

\

BAGGS TO NORTH PLA TTE PIPELINE

D!VIDE BASIN

\

\.._~C: N TIN £ N TAL l.._./\ .... //",;

c,... ..

SANDSTONE RESERVOIR

_ INITIAL DEVELOPMENT

_ ULTIMATE DEVELOPMENT

o 5 ----- 10 15

SCALE IN MILES

ROUTT

20 !


RECOMMENDED PLAN OF DEVELOPMENT

F 0 I, .E S T

NATIONAL FOREST

FIGURE 4

~ Stone & Webster Engineering Corporation

APPENDIX SUMMARY

NORTH PLATTE RIVER SUPPLEMENT

The North Platte River Management Model (NPRMM) is a computer program

which simulates the river operations which are coordinated by the U. S.

Bureau of Reclamation using the six storage reservoirs on the North Platte

River in Wyoming. Figure 6 shows the location of these six reservoirs

along the North Platte River.

As a portion of the LSRWMP Phase I work, a study of the currently

available NPRMM revealed that the model was incapable of accounting for

imported water from the Little Snake River Basin or quantifying possible

additional existing water resources in the North Platte River. A new

algorithm was developed to establish an additional ownership account

(Excess-to-Ownership). Several studies were performed using the revised

model and discharge records for the period 1940 to 1982.

The term "excess-to-ownership" refers to the amount of North Platte

River water that is available after all present ownerships are satisfied

or, simply, unappropriated water. By accounting for the "excess-to

ownership" water in the North Platte River, a firm annual yield of about

8,400 acre-feet can be obtained from an enlarged Seminoe Reservoir. A

yield of 9,600 acre-feet per year was found with only two out of 56 years

experiencing shortage.

There is sufficient remaining capacity in the existing Seminoe,

Pathfinder, and Glendo Reservoirs to regulate imported water from the Fish

Creek Collector system. An enlargement of Seminoe Reservoir is not

necessary to regulate the imported water, but it would make possible the

maximum utilization of the total water resources of the system.

The NPRMM has been a useful tool for evaluating the impacts of

importing water into the North Platte River Basin from the Little Snake

River. For future detailed planning, the model should include options of

where, when, and how much water will be imported. The quantity, timing and

diversion points for utilizing the imported water should be modeled as well

as the necessary conveyance loss estimates. The calculation of conveyance

losses below Guernsey Dam and the demands of private ditches below Whalen


LITTLE SNAKE RIVER LEVEL III PHASE I - SELECT PLAN

IN BASIN DEVELOPMENT

SANDSTONE DAM

ENVIRONMENTAL IMPACT STATEMENT

CONCEPTUALIZE

DESIGN

CONSTRUCTION

TRANS BASIN DEVELOPMENT

COLLECTOR SYSTEM AND FISH CREEK DAM

ENVIRONMENTAL IMPACT STATEMENT

DESIGN

CONSTRUCTION

ULTIMATE DEVELOPMENT

POT HOOK/THREE FORKS DAMS AND BAGGS PIPE LINE

RESOLVE COLO. INTEREST

DESIGN

CONSTRUCTION

0 1 2 3 198- 199-456 7 8 9 0 1 2 345 6 7 8 9

-

---

...... -~

-----~--------

200-0 1 2 3 4 5 6 789 0

-

20'1- 202-1 2 3 4 5 6 7 E 9 o 1 2 3 4 5 6 7 8 9


PREFERRED DEVELOPMENT PLAN YEARS 1984 THROUGH 2029

FIGURE 5

co o

~ • o -ID

Diversion Dam should be revised. The model has been separately modified by

Western Water Consultants and Boyle Engineering in 1984. These two

modifications plus the proposed exchange of water between the Casper Alcova

Irrigation District and the City of Casper should be incorporated into a

single model.

Since Wyoming

utilization of North

has a

Platte

major

River

interest

waters

in the present and future

and the WWDC is involved in

planning and development of projects such as the LSRWMP which need a

computer model to evaluate .the impacts and benefits of imported water, it

is recommended that the WWDC initiate this effort to insure the model's

reliability as a planning tool.

-17- STONE 8c WEBSTER A

--------------------------------------------------------------------------~ .

Douglas

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\ ( J KORTES~~~

/ RE& (SEMINOE : l----, RES. J

" • 0,. ~ ~~~ \ 01'1);, C -, ~'\ .&.~. °"PI

,~ont;nental I! ~~ ~

LITTLE SNAKE R:;;~ c.'" tl ~ WATER DEVELOPMENT " Laramie,..,---------- (Q PROJECT \ C. ,.- --- <t IMPORTED WATER '\~ \ 0 .: ffi

----1-_ .• ---....-__ ,,/ £.HEYENJ~EI z

'" I J 0 I /. ~ J I I \ ) COLORADO \ '--.. / .....,.,.--

NORTH PLATTE RIVER BASIN

FIGURE 6

STONE Be WEBSTER A

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