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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

Phone: (307) 766-6651 Fax: (307) 766-3785

Funding for WRDS and the creation of this electronic document was provided by the Wyoming Water Development Commission

(http://wwdc.state.wy.us)

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Prepared for:

WHEATLAND RESERVOIR NO. 2 REHABILITATION PROJECT

LEVEL II FEASIBILITY STUDY PHASE I REPORT

JANUARY 1990

The Wheatland Irrigation District

Directors; Larry Lesback Jim Graves Phil Jenkins Bart Trautwein Alan Utter

Manager; Donald D. Britton

and the Wyoming Water Development Commission

Members;

Administrator; Project Manager;

Prepared by:

Beryl Z. Churchill William L. Glanz Myron Goodson Paul Hickey Wayne Moore Leslie Petersen Merl Rissler Kathleen Sun George Zebre Michael K. Purcell Michael A. Carnevale

Prime Consultant - Banner Associates, Inc.; Laramie, Wyoming

Subconsultants - Woodward-Clyde Consultants; Denver, Colorado - Kennedy Engineering; Wheatland, Wyoming - Western Research Corporation; Laramie, Wyoming

Banner Job No. 2379

TABLE OF CONTENTS

1.0 INTRODUCTION 1.1 Project Authorization 1.2 Project Description and Scope 1.3 Project Team

2.0 PROJECT DESCRIPTION, SUMMARY AND RECOMMENDATIONS 2.1 Description 2.2 Summary 2.3 Recommendations

3.0 PREVIOUS STUDIES AND REPORTS 3.1 COE - September 1979 3.2 RBD - January 1985 3.3 SEO - Letter February 1988, Report December 1987 3.4 SCS - October 1988

4.0 FLOOD ANALYSIS 4.1 Introduction 4.2 Probable Maximum Flood (PMF) Determination 4.3 Hydraulic Analysis 4.4 Flood Routing

4.4.1 Without the darn in place 4.4.2 With the darn in place 4.4.3 With the darn in place and failure of the darn

4.5 Results of the Routing Studies

5.0 ECONOMIC ANALYSIS 5.1 Introduction 5.2 Methodology 5.3 Results 5.4 Conclusions

6.0 CONSERVATION POOL ANALYSIS

7.0 GEOTECHNICAL ANALYSIS 7.1 Introduction 7.2 Review of Previous Studies 7.3 Site Reconnaissance 7.4 Stability Evaluation 7.5 Field Investigations 7.6 Recommendations

8.0 SAFETY INSPECTION AND OPERATIONAL ANALYSIS 8.1 Introduction 8.2 Outlet Works

8.2.1 Existing Facilities 8.2.2 Deficiencies and Problems 8.2.3 Conclusions and Recommendations

PROPERTY' OF WHDS LIBRA

LARAMIE, Wy AY (307) 766-6661

1-2 1-2 1-3

2-1 2-5 2-6

3-1 3-1 3-2 3-3

4-1 4-4 4-6 4-16 4-17 4-18 4-21 4-29

5-1 5-1 5-5 5-8

7-1 7-1 7-2 7-5 7-8 7-16

8-1 8-1 8-1 8-3 8-3

8.3 Main Spillway 8.3.1 Existing Facilities 8.3.2 Deficiencies and Problems 8.3.3 Conclusions and Recommendations

8.4 Auxiliary Spillway 8.4.1 Existing Facilities 8.4.2 Deficiencies and Problems 8.4.3 Conclusions and Recommendations

8.5 Additional Facilities 8.5.1 Existing Facilities 8.5.2 Deficiencies and Problems 8.5.3 Conclusions and Recommendations

9.0 REHABILITATION ALTERNATIVES AND OPINION OF PROBABLE COSTS

8-5 8-5 8-7 8-8 8-8 8-8 8-9 8-9 8-11 8-11 8-11 8-11

9.1 Introduction 9-1 9.2 Alternative Analyses 9-1

9.2.1 Abandonment 9-1 9.2.2 Do Nothing 9-1 9.2.3 Additional Investigations 9-2 9.2.4 Upgrade Existing Facilities 9-3 9.2.5 "Armoring" of the Main Spillway Embankment 9-6 9.2.6 Replace Main Spillway and Main Spillway Embankment 9-6 9.2.7 Upgrade the Discharge Channel Downstream of the

Main Spillway 9-9 9.2.8 Upgrade the Wheatland Reservoir No.3 Supply Canal

and the Discharge Canal from the Supply Canal to the Laramie River 9-9

9.2.9 Improve Main Spillway Access 9-11 9.2.10 Motorize Auxiliary Spillway Gate Operation 9-12

9.3 Alternatives Recommended for Further Consideration 9-12

10.0 SURVEYING

11.0 PERMITS AND ENVIRONMENTAL STUDIES 11.1 Introduction 11.2 Dredge and Fill Permits (404 and Nationwide) 11.3 Section 401 Certification 11.4 Archeology and SPHO Clearance 11.5 State Engineer's Office and Water Use Agreements 11.6 Department of Enviro~enta1 Quality (DEQ)

11.6.1 Water Quality Division (WQD) 11.6.2 Land Quality Division (LQD) 11.6.3 Air Quality Division (AQD)

11.7 Miscellaneous Permits and Special Requirements 11.8 Land Acquisition/Easements

REFERENCES

APPENDIX A - FLOOD ROUTING CROSS SECTIONS

APPENDIX B - VYOMING DAM INSPECTION REPORT

11-1 11-1 11-2 11-2 11-2 11-2 11-3 11-3 11-4 11-4 11-4

Table 4.1

Table 4.2

Table 4.3

Table 4.4

Table 4.5

Table 4.6

Table 4.7

Table 4.8

Table 4.9

Table 4.10

Table 4.11

Table 4.12

Table 4.13

Table 4.14

Table 4.15

Table 4.16

Table 5.1

Table 5.2

Table 5.3

LIST OF TABLES

Wheatland Reservoir No. 2 Elevation-Capacity Table

Wheatland Reservoir No. 2 - Inflow Design Flood

Wheatland Reservoir No. 2 - Comparison of PMP and PMF Parameters

Summary of the Physical Characteristics of the Spillways and Outlet Works

Wheatland Reservoir No. 2 - Spillway and Outlet Works Elevation - Discharge Relationship

Wheatland Reservoir No. 2 - Comparison of Rating Curves

Wheatland Reservoir No.2 - 25% PMF, Cross Section Peak Flows and Depths

Wheatland Reservoir No.2 - 50% PMF, Cross Section Peak Flows and Depths

Wheatland Reservoir No.2 - Full PMF, Cross Section Peak Flows and Depths

Dam Inspection Hydrologic Analysis - Summary Table -25% PMF

Dam Inspection Hydrologic Analysis - Summary Table -50% PMF

Dam Inspection Hydrologic Analysis - Summary Table -Full PMF

Dam Inspection Hydrologic Analysis - Summary Table -Lake Elevations, Storages and Discharge Rating Tables

Outflow Hydrograph and Flow Segregation - 25% PMF -No Dam Failure

Outflow Hydrograph and Flow Segregation - 50% PMF -No Dam Failure

Outflow Hydrograph and Flow Segregation - Full PMF -No Dam Failure

Name and Location of Ranches in the Floodplain

Property Valuation Factors

Inventory of Ranch Property in the Floodplain

4-2

4-7

4-9

4-10

4-12

4-14

4-18

4-19

4-20

4-22

4-23

4-24

4-25

4-26

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Figure 2-1

Figure 2-2

Figure 2-3

Figure 4-1

Figure 4-2

Figure 4-3

Figure 5-1

Figure 6-1

Figure 7-1

Figure 7-2

Figure 7-3

Figure 7-4

Figure 7-5

Figure 8-1

Figure 8-2

Figure 8-3

Figure 8-4

LIST OF FIGURES

Page

Location Map 2-2

Vicinity Map 2-3

Dam Embankment Plan 2-4

Active Storage Curve 4-3

Wheatland Reservoir No. 2 - Inflow Design Flood 4-8

Discharge Curves 4-13

Name and Location of Ranches in the Flood Plain 5-3

Wheatland Reservoir No. 2 - End of Month Content 6-3

Typical Dam Embankment Croos Section 7-3

Embankment Slope Stability Analysis Cross Section 7-7

Test Pit Locations 7-11

Gradation Analysis Test Pits TP-l, TP-3, & TP-4 7-14

Gradation Analysis Test Pit TP-7 7-15

Existing Outlet Works Tunnel Plan and Profile 8-2

Existing Outlet Works Tunnel Sections 8-4

Existing Main Spillway 8-6

Existing Auxiliary Spillway 8-10

1.0 INTRODUCTION

1.0 INTRODUCTION

1.1 PROJECT AUTHORIZATION

The Wyoming Legislature authorized the Water Development Commission to conduct a Level II Feasibility Study of the rehabilitation of the Wheatland Reservoir No.2 Dam. A final report will be presented at the completion of Level II activities. This report must be completed in sufficient detail to allow the Commission to request Level III construction funding from the 1991 Session of the Wyoming Legislature. Level II activities include both a Phase I preliminary analysis and report followed by a Phase II conceptual analysis and report.

On July 1, 1989, the Wyoming Water Development Commission entered into a contract with Banner Associates, Inc. to provide the Level II services.

This report constitutes the Phase I Feasibility Study for the Level II Report.

1.2 PROJECT DESCRIPTION AND SCOPE

Location: The Wheatland Reservoir No. 2 is located in Albany County, T2lN and T22N, R73W and R74W, approximately 40 miles north of Laramie, Wyoming and 35 miles west southwest of Wheatland, Wyoming.

Purpose: The purpose of the study is to evaluate the condi tion of Wheatland Reservoir No. 2 facilities and to identify and describe those rehabilitation measures which may be necessary for continued safe and efficient operation of the facility.

History: The Wheatland Reservoir No. 2 was constructed between 1880 and 1890 and was raised to its present elevation in the 1930' s. The outlet works were modified to the present configuration in 1973. The toe drain system was installed in 1973 and expanded in 1982. The dam is an earth fill structure approximately 8,400 feet long consisting of two dams of approximately equal length tying into a high point of terrain at the midpoint.

Sponsor: Wheatland Reservoir No. 2 is Wheatland Irrigation District, this project.

1-1

owned and operated by the which is the sponsor for

The Wheatland Reservoir No. 2 Project Level II Phase 1 scope consists of:

- A review of previous studies and reports.

- A flood analysis, including a PMF determination, a duration analysis, a hydraulic analysis, and several flood routing scenarios.

- An economic analysis including damage costs.

- A conservation pool analysis.

- A geotechnical evaluation including a stability analysis and test pits to evaluate existing conditions and determine potential material borrow sources.

- A safety inspection and operational analysis of existing outlet works, spillways, and canals.

Developing rehabilitation alternatives and an opinion of probable cost for these alternatives.

- Surveying of existing dam and facilities.

- Identifying permits and environmental studies required for construction of the various rehabilitation alternatives.

1.3 PROJECT TEAM

Banner Associates, Inc. has assembled a multidisiplinary group of specialists to accomplish the tasks defined in the contract. Banner's specialty subconsultants who provided assistance during the preparation of this report and their task assignments are:

Woodward Clyde Consultants, Inc. Western Research Corporation Kennedy Engineering

Geotechnical evaluations Economic analyses Wheatland Irrigation District records research, review

1-2

2.0 PROJECT DESCRIPTION, SUMMARIES AND RECOMMENDATIONS

2.0 PROJECT DESCRIPTION, SUMMARY AND RECOMMENDATIONS

2.1 DESCRIPTION

Wheatland Reservoir No.2 is located on the Laramie River in Albany County, Wyoming. The Wheatland Reservoir No. 2 Location Map is shown on Figure 2-1, and the Vicinity Map is shown on Figure 2-2. The length of the basin at the reservoir site is about 95 miles, with a maximum basin width of about 45 miles. Topography of the area is rolling to mountainous and the drainage patterns are well-defined. Slopes along the main channel average about 18 feet per mile. Land use in the basin is primarily agricultural and forest.

Wheatland Irrigation District holds an adjudicated Wyoming water right (No. 1724) for the Wheatland Reservoir No. 2 and Dam. The water right is for a total of 98,934.00 acre-feet and has a priority date of 1/29/1898.

The Wheatland Reservoir No. 2 dam embankment is a rolled earth fill structure about 8,280 feet long, 36.6 feet high at the maximum section, and 23 feet to 30 feet wide at the crest. The Dam Embankment Plan is shown on Figure 2-3. The embankment has a curved alignment between the valley abutments. The crest elevation varies along its length from a minimum of 6970.6 to a maximum of 6972.5 feet. The crest elevation averages about 6971.7 feet. A crest elevation of 6971.5 feet was used in this study as the routing studies were completed prior to receipt of the survey data. The minor difference in crest elevations is not significant to the results of this study. Based on a crest elevation of 6971.5 and a NHWL of 6964 the available flood surcharge capacity prior to overtopping the main dam embankment is 55,383 acre-feet.

The Wheatland Reservoir No. 2 main spillway embankment is located approximately 5.8 miles from the outlet works facilities. The main spillway embankment is approximately 800 feet long with an approximate crest width of 12 feet which widens in the vicinity of the spillway structure. The main spillway embankment crest elevation is approximately 6967 feet which is 4.5 feet below the top of the dam embankment.

Discharge structures for Wheatland Reservoir No.2 include a main spillway, an auxiliary spillway, a main outlet works, and three small irrigation gated outlet structures. A continuing concern has been the ability of Wheatland Reservoir No. 2 to safely pass an extreme flood event. The reservoir's ability to handle a flood depends on: the reservoir's storage capacity, the hydraulic capacities of the spillways and outlet works, and the magnitude and timing of the inflow flood hydrograph.

Wheatland Reservoir No.2 is classified by the U.S. Army Corps of Engineers and the Wyoming State Engineer as a large size dam with a significant hazard potential. Typically, a dam with this classification is required to safely pass the Probable Maximum Flood (PMF) without failure of the dam. A lesser flood may be used as the Spillway Design Flood (SDF) if it can be shown that failure of the dam under a larger flood would not result in any significant increase in damages or loss of life over the baseline condition of the flood occurring without the dam in place.

2-1

UTA H

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NO SCALE

BANNER "--___ W_H_EA_T_lA_N_O _R_ES_E_R_VO_I_R_N_O_. _2 __ ---I r- REHABILITATION - PHASE I

BANNER ASSOCIATES. INC. • CONSULTING ENGINEERS' ARCHITECTS 620 PLAZA COURT. P.O.IOX 550 - LARAMIE. WY 82010 • 1307) 745-7366 LOCATION MAP

FIGUREs

2-1

R. 74 W. R. 73 W.

~ ________________________________ ~ ______ -:~ ______ ~~~MAIN

SPILLWAY

LARAMIE RIVER

AUXILIARY SPILLWAY

OUTLET WORKS

N

LARAMIE RIVER

NO SCALE

BANNER I-______ W_H_E_AT_L_AN_O_R_ES_E_R_VO_I_R_N_O_. _2 __ ----1 REHABILITATION - PHASE 1

BANNER ASSOCIATES. INC. • CONSULTING ENGINEERS L ARCHITECTS 620 PLAZA COURT. P.O.IOX 550 - LARAMIE. WY 82010 • 13011 145-1366 VICINITY MAP

T. 23 N.

T. 22 N.

T. 21 N.

FIGURE-

2-2

II ELEVATION TOP OF

16971.31 AUXILIARY SP IllWAY (

DAM EMBANKMENT InP')

BM 235~5'5 ___ _ T}'o STRUCTURE APPRoX. <l TOP OF DAM EMBANKMENT

~~~~~7il'9~~==~r7iI.8~=-=-==_=_~~7~13~~==~~7~1.6~~~==~n~.o~~====~71.~8~~~~7~1.~4~==~~~~~~~~~==~~71~.8~~~~ 74i I ~ ~ -- -- - ~ -- - ~ I- ~m wC'< ~ ~ T ~ L!J

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NHWl • El. 6964.0 a.

DATA TAKEN FROM ACTUAL FIELD SURVEY 28-AUG-89.

':BANNER BANNER ASSO[IATES. IN[. • [ONSULTING ENGINEERS ~ AR [ HITECTS 620 PLAZA COUR T • P.O.BOX 550 - LARA1IE. WY 82070 • 13071745-7366

~ WHEATLAND RESERVOIR NO.2 \

WHEATLAND RESERVOIR NO.2 REHABILITATION - PHASE I

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PROPER~~JM~~~ LIBRARY (307) 766-6661

W H EAT LA N D RES E RV 0 I R NO. 2 DAM EMBANKMENT PLAN

2-4

FIGURE:

2-3

2.2 SUMMARY

Wheatland Reservoir No. 2 is capable of passing an event of somewhat less than the 50% PMF without the main embankment overtopping. The main spillway embankment would overtop at a storm less than the 25% PMF. However, it is believed that overtopping of the main spillway embankment would not result in a catastrophic failure of Wheatland Reservoir No.2. The main spillway embankment for the most part is no more than three feet high. The natural ground level at the main spillway embankment is approximately at the normal high water line (elevation 6964). The ground slope from the main spillway area towards the reservoir is very shallow, and an extremely large volume of material would have to be eroded away before any significant depth of cutting would occur.

The hydrological analyses undertaken for this study show that for all levels of a probable maximum flood (25%, 50%, and full PMF), there would be no appreciable difference in damages to existing structures and agricultural lands in the downstream floodplain.

The overall result is that from a downstream flooding standpoint, no benefit is gained by increasing the spillway capacities to pass a PMF when compared against letting the dam embankment overtop and fail during this extreme flood event.

The results of the incremental damage assessment indicate property losses resulting from a flood of a magnitude in the range of the 25% PMF to the full PMF would be approximately $12 million. The lives of 30 to 40 residents of the floodplain also would be at risk. This conclusion applies regardless of whether Wheatland Reservoir No. 2 is capable of passing the full PMF. There appears to be no significant difference in damages or risk to human life regardless of whether improvements are made to the Wheatland Reservoir No. 2 facilities. The simple fact that Wheatland Reservoir No. 2 exists has the effect of attenuation of the flood peak compared to the "without reservoir" scenario. In effect, the reservoir serves as a large detention pond to attenuate peak flow.

The Geotechnical Analysis and the Safety Inspection and Operational Analys is revealed no "fatal flaws"; that is, no deficiencies of a maj or nature with a high probability of a catastrophic failure in the immediate or near future. These analyses did, however, reveal several deficiencies and potential problems which can be classed as "deferred maintenance" items; that is, items that have been neglected and should be included with an ongoing operation and maintenance program. In addition, there are several areas that were defined in both the Geotechnical Analysis and the Safety Inspection and Operational Analysis that may require further investigations to better define the rehabilitation efforts required.

The rehabilitation alternatives addressed in this report include:

o Abandonment of the dam.

o Do nothing.

2-5

o Perform additional investigations.

o Upgrade existing facilities.

o "Armoring" of the main spillway embankment.

o Replace main spillway and main spillway embankment.

o Upgrade the discharge channel downstream of the main spillway.

o Upgrade the Wheatland No. 3 supply canal and the discharge canal from the supply canal to the Laramie River.

o Improve main spillway access.

o Motorize the auxiliary spillway gate operation.

The existing facilities provide a service to downstream farmers and ranchers. However, as with all facilities, continued maintenance is required for optimal performance; therefore the "Abandonment of the Dam" and "Do Nothing" alternatives would not be prudent. These alternatives have no immediate costs. However, at some point "deferred maintenance" items would become a safety hazard and would require greater and presumably more costly rehabilitation efforts.

The determining factor for many of these rehabilitation alternatives is the fact that the Economic Analysis determined that there would be no appreciable differences in incremental damages associated with a maj or flood event and possible failure of the embankments. Therefore, consideration of the recommended alternatives should revolve around providing the intended service, that of providing an irrigation water supply to the downstream farmers and ranchers.

2.3 RECOMMENDATIONS

Based upon these preliminary investigations and input from the Sponsor, the recommended rehabilitation alternatives, generally termed "Upgrade Existing Facilities", include:

o Fill in the low area of the dam crest.

o Rip rap the upstream dam face.

o Establish a rodent control program.

o Evaluate the cause and repair the "sinkhole".

o Repair the two sloughed areas.

o Re-establish, or install new piezometers, seepage measurement weirs and embankment movement monuments.

2-6

o Repair exiting irrigation outlets.

o Repairs to the outlet works and control building.

o Repairs to the main spillway.

o Repairs to the auxiliary spillway.

A preliminary opinion of probable cost was developed for the recommended rehabilitation alternatives. The preliminary opinion of probable cost developed for these recommended rehabilitation alternatives is shown on Table 2.1. The preliminary opinion of probable cost is $920,000.00. These costs may be substantially reduced if the Wheatland Irrigation District elects to perform several of these "upgrade" items using their own forces.

In addition to the "Upgrade Existing Facilities" alternative, it is further recommended to perform the following studies, investigations, and development of documented operation, maintenance and inspection manuals. A preliminary opinion of probable construction cost was not developed for the following recommended alternatives as these alternatives are essentially future studies:

o Development of an operation, maintenance and inspection manual.

o Inspection and operation of the outlet works, main spillway, auxiliary spillway as well as the irrigation facilities at reservoir levels up to at least the NHWL at elevation 6964.

o Completion of additional strength testing and stability analyses as well as observation and analysis with the reservoir at higher water levels.

Based on the preliminary investigations, the remaining rehabilitation alternatives have merit for further consideration. Also, incorporation of these rehabilitation alternatives may reduce the need for some of the upgrading existing facilities costs. For example, if the replace main spillway and main spillway embankment rehabilitation alternative is pursued, then the costs to upgrade the existing main spillway facilities are not required.

Addi tional input from the Wheatland Irrigation District and the Wyoming Water Development Commission is required for incorporation of addi tional rehabilitation alternatives into future investigations.

2-7

TABLE 2.1 WHEATLAND RESERVOIR NO.2

UPGRADE EXISTING FACILITIES PRELIMINARY OPINION OF PROBABLE COST

ITEM DESCRIPTION

Upgrade Dam Embankment Section 7.6 Item I-Fill in low area of dam crest

Item 2-Riprap upstream dam face Item 3-Rodent control program Item 4-Repair "sink-hole" Item 5-Repair two sloughed areas Item 6-Re-establish or install new

piezometers, seepage measurement weirs and embankment movement monuments

Item 7-Repair existing irrigation outlets

UNIT

LS LS LS LS LS LS

LS

SUBTOTAL

Upgrade Outlet Works LS Install Trash Racks and Vortex Splitter Wall Repaint Concrete Block, Interior, Exterior and Doors Replace Latch Set Remove Steel Pipe in Wet Well Site Grading and Installation of Protection Wall Grouting Behind Steel Liner

Upgrade Main Spillway LS Repair and Install Guardrail Repair Piers Repair Downstream Apron Repair Underdrain Below Apron Repair Cracks and Spalled Concrete Replace Skin on Gate, Repair, and Repaint Gates

Upgrade Auxiliary Spillway Repair Guardrail Repair Piers Remove and Replace Apron Slabs Remove and Replace Slope Paving Repair Cracks and Spalled Concrete Replace Skin on Gates, Repair, and Repaint Gates

15% Contractor's Overhead and Profit

15% Contingencies

15% Design Engineering

10% Construction Administration

2-8

LS

SUBTOTAL

SUBTOTAL

SUBTOTAL

SUBTOTAL

TOTAL

USE

AMOUNT

$ 67,000.00 $215,000.00 $ 53,000.00 $ 2,000.00 $ 2,000.00 $ 20,000.00

$ 7,000.00

$366,000.00

$ 48,000.00

$ 74,000.00

$ 60,000.00

$548,000.00 $ 82,200.00 $630,200.00 $ 94,530.00 $724,730.00 $108,710.00 $833,440.00 $ 83,334.00 $916,784.00

~9201000.00

3.0 PREVIOUS STUDIES AND REPORTS

3.0 PREVIOUS STUDIES AND REPORTS

The following sections briefly sturunarize previous studies and reports on Wheatland Reservoir No. 2 regarding dam safety issues. All the documents listed below are on file at the Wyoming State Engineer's Office.

3.1 U.S. ARMY CORPS OF ENGINEERS - PHASE I INSPECTION REPORT. SEPTEMBER 1979

Wheatland Reservoir No. 2 was inspected as part of the U.S. Army Corps of Engineers' (COE) National Dam Safety Program on September 18, 1979 with a subsequent Phase I Inspection Report being published. The COE classified Wheatland No. 2 Dam as a large dam with a significant hazard potential. The Phase I Inspection Report stated that generally the dam was structurally and geotechnically satisfactory; however, hydrologically it was seriously inadequate. The report stated that the dam can safely pass less than 40 percent of the Probable Maximum Flood (PMF). The COE report determined the PMF to be approximately 65,000 cfs.

The report listed several assessments and recommendations regarding the Wheatland No. 2 Dam. Recommendations to be implemented as soon as possible were: 1) a detailed hydrologic analysis to determine more accurately the PMF and required modifications to discharge this flood; 2) monitor and record seepage, and perform a formal stability analysis; and 3) observe the spillway gates during ice loading and determine capability to withstand severe ice loading conditions. Other recommendations included a thorough inspection of the main outlet works and verification that the irrigation outlet was properly abandoned, downstream channel bank stabilization, spillway maintenance be performed including periodic operation and development of a maintenance manual, develop a formal documented operation plan, and finally, implement a monitoring and inspection program and maintain records of such.

3.2 RBD. INC. - GEOTECHNICAL AND STABILITY ANALYSES. JANUARY 1985

RBD, Inc. performed field explorations in July of 1984, including drilling, logging, and sampling of the dam embankment materials. Following field investigations and laboratory analyses, a stability analysis was performed. RBD determined the dam to have a minimum factor of safety against failure of 2.15, and concluded that the embankment was structurally adequate. In addition, RBD made the recommendations that erosion should be prevented on the upstream slope of the dam by applying riprap (minimum rock size of 12 inches, ranging to 36 inches), and that extermination and rodent control be undertaken on and near the dam.

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3.3 WYOMING STATE ENGINEER'S OFFICE - INSPECTION REPORT. DECEMBER 1987. AND LETTER OF FEBRUARY 1988

The Wyoming State Engineer's Office inspected Wheatland Reservoir No. 2 on August 14 and December 11, 1987. Following the inspections, a report was prepared on December 24, 1987, which resulted in the letter to the Wheatland Irrigation District from the State Engineer in February 1988. That letter expressed specific concerns about the long-term safety of the dam. Many of the concerns reiterated concerns and recommendations made in the previous reports summarized above. Specifically, the concerns expressed were: 1) apparent inadequate spillway capacity and access to the main spillway; 2) undesirable vegetation and rodents on the dam embankment; 3) potential ice loading problems on spillways and other structures; 4) erosion protection below the main spillway and future structure rehabilitation; and 5) proper abandonment of the irrigation outlet pipe near the north abutment (note: WID's response indicates that this outlet is not abandoned and is used).

3.4 SOIL CONSERVATION SERVICE - LETTER REPORT. OCTOBER 1988

The Soil Conservation Service (SCS) responded to a request to assist in formulating a plan to increase the spillway capacity of Wheatland Reservoir No.2. Additionally, the SCS addressed some of the other concerns expressed in the State Engineer's letter. The SCS evaluated the hydraulic capacities of the outlet works and the spillways, and performed reservoir routings of various percentages of the PMF (as determined in the COE report). The SCS concluded that Wheatland Reservoir No.2 has the capacity to discharge the 75% PMF storm without overtopping the dam embankment. To accomplish this, it was recommended that the main spillway embankment be riprapped for protection in order to act as an emergency spillway. The SCS also indicated that snow drifting and ice loading has not appeared to be an operational problem. The SCS also suggested that the dam caretaker may need to have a snow machine or a four-wheel All Terrain Vehicle to gain access to the main spillway under snow conditions. An alternative would be to motorize and remotely operate the gates.

3-2

4.0 FLOOD ANALYSIS

4.0 FLOOD ANALYSIS

4.1 INTRODUCTION

As noted in the Section 3.0, a continuing concern has been Wheatland Reservoir No.2' s capacity to safely pass an extreme flood event. The reservoir's ability to handle a flood depends on: the reservoir's storage capacity, the hydraulic capacities of the spillways and outlet works, and the inflow hydrograph.

Wheatland Reservoir No.2 has a capacity of 98,934 acre-feet at the normal high water line (NHWL) elevation of 6964. The elevation-capacity relationship is presented in Table 4.1 and illustrated on Figure 4-1. The information was obtained from the expanded capacity table dated April 30, 1968 on file at the Wyoming State Engineer's Office in Cheyenne.

Discharge structures for Wheatland Reservoir No. 2 spillway, an auxiliary spillway, a main outlet works,

include a and three

main small

irrigation gated outlet structures. Drawings of the main outlet works are shown on Figure 8-1 and Figure 8-2, and drawings of the main spillway and the auxiliary spillway are shown on Figure 8-3 and Figure 8-4, respectively.

The main spillway is located at the north end of the reservoir and the auxiliary spillway is located at the left abutment of the main dam. No earth cut emergency-type spillway exists for the Wheatland Reservoir No.2. The main spillway structure and associated earth embankment are overtopped at about elevation 6966.9, or 4.6 feet below the top of the main dam embankment. The auxiliary spillway has a top elevation of 6972.0 and will not be overtopped unless the main dam embankment is overtopped. The auxiliary spillway discharges into the Supply Canal for Wheatland Reservoir No. 3 which extends for approximately two miles, at which point a large drop structure divides flow between the Wheatland Reservoir No. 3 and the Laramie River channel. The channel returning to the Laramie River has head gates located at the base of this drop structure. Due to the high erosion potential of the Supply Canal for Wheatland Reservoir No.3, discharge is typically limited to about 700-750 cfs. The Supply Canal for Wheatland Reservoir No. 3 extends approximately two miles from the drop structure to Wheatland Reservoir No.3. Water released from Wheatland No. 3 is delivered back through this flat bottom, level canal and diverted through the head gates into the Laramie River.

The main spillway is a gated structure constructed of reinforced concrete with four gate bays. The downstream apron has an approximate elevation of 6954. Each bay has a 2.1 foot high concrete sill immediately beneath the gate, or otherwise stated, an approximate sill elevation of 6956.1. The bays vary in width from 13.7 feet to 14.2 feet as shown on Figure 8-3. The vertical slide gates are about 7.8 feet high. The main spillway capacity at NHWL is approximately 4,210 cfs.

4-1

Elevation (MSL)

6935 6936 6937 6938 6939 6940 6942 6944 6946 6948 6950 6952 6954 6956 6958 6960 6962 6964

Source:

TABLE 4.1

Wheatland Reservoir No. 2 Elevation-Capacity Table

Incremental Volume

(AF)

o 934

1,049 1,164 1,279 1,395 3,142 3,612 4,268 5,113 6,005 7,192 8,428 9,410

10,139 10,910 11,920 12,974

Cumulative Volume

(AF)

o 934

1,983 3,147 4,426 5,821 8,963

12,575 16,843 21,956 27,961 35,153 43,581 52,991 63,130 74,040 85,960 98,934

Wyomings State Engineer's Office Permit 1724, Expanded Capacity Table Prepared April 30, 1968

4-2

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The auxiliary spillway is also a gated structure constructed of reinforced concrete with three gate bays. The spillway has an upstream and a downstream apron with an elevation of 6954.0 and the gates resting directly on the apron (i.e. no raised sill). The bay widths vary from 11.9 feet to 12.0 feet as shown on Figure 8 -4. Each vertical slide gate is about 10 feet high. The auxiliary spillway capacity at NHWL is approximately 1,520 cfs.

The main outlet works consists of two 84-inch diameter pipes that each lead into a gated wet well (two wet wells). Each wet well has two 5-foot by 5-foot gates (total of four gates) that discharge into a corrugated metal lined horseshoe outlet conduit (total of two outlet conduits). Each outlet conduit is approximately a 5'-7" by 6'-2" horseshoe and both discharge unto a common downstream apron. The outlet works are illustrated on Figures 8-1 and 8-2. The outlet works can discharge approximately 1,320 cfs with the reservoir at the NHWL.

There are three small irrigation gated outlet structures in the dam. These outlet works consist of submerged low level intakes, gate valve or slide gate control at or near the upstream end of the pipe, conduit in the 12-inch to l8-inch diameter range and an outlet into a small irrigation ditch. The capacity of these outlets is small in comparison to the main outlet works, and all were assumed to be closed during the flood routing analyses. As an example, the nameplate on one of the outlet works states that the headgate is for diversion to a territorial right of 10.07 cfs.

The reservoir stores water from spring runoff and rainfall. Water is released as required by downstream appropriations and by permitted appropriators using the storage of the reservoir. Operation is accomplished by Wheatland Irrigation District personnel. It has been reported that the main spillway has been used only twice during the history of the dam, with the last use of the main spillway occurring in 1984.

4.2 PROBABLE MAXIMUM FLOOD (PMF) DETERMINATION

Wheatland Reservoir No. 2 is classified as a large size dam with a significant hazard potential. Typically, a dam with this classification is required to safely pass the PMF without failure of the dam. A lesser flood may be used as the Spillway Design Flood (SDF) if it can be shown that failure of the dam under a larger flood would not result in any significant increase in damages or loss of life over the baseline condition of the flood occurring without the dam in place.

The first step in determining the PMF is to establish the Probable Maximum Precipitation (PMP) for an upstream storm. Procedures for determining the PMP for this region are established in Hydrometeorological Report (HMR) No. 55A. The PMP could occur from either a general storm, one covering a large area usually the entire basin, or a local storm, typically a thunderstorm and limited in size to a maximum of 500 square miles. Both storms are analyzed for the site, the precipitation applied to the basin, and the

4-4

resulting runoff determined. The storm producing the largest peak flow and volume is typically used as the PMF for the reservoir inflow. For the purposes of this study, it was assumed the storm that generates the general storm PMP would be located over the entire drainage basin area. The drainage area was obtained primarily from the data published with USGS gaging station 06-6620.00 (Laramie River near Lookout). The drainage area at this gage, located one mile upstream of Wheatland Reservoir No. 2 is published by the USGS as "2,174 square miles of which 603 square miles is probably non-contributing". The drainage area of basin below USGS gage 06-6620.00 and upstream of the Wheatland Reservoir No. 2 main embankment was planimetered to be about 46 square miles (including the reservoir area) . The reservoir surface area at the top of the spillway gates (elevation 6964) was planimetered to be about 10 square miles.

Using HMR 55A, the general storm PMPs for various durations were determined. The 6-hour and 72-hour index PMPs were determined to be 13.27 inches and 27.56 inches, respectively. Factors were then applied to adjust the rainfall to take into account topographic and areal distribution affects. The resulting general storm 6-hour and 72-hour PMPs for Wheatland Reservoir No.2 are 6.42 inches and 17.95 inches, respectively.

Similarly, the local storm PMP was determined. The maximum storm cell size of 500 square miles was used for Wheatland Reservoir No. 2 and was assumed to be located immediately upstream of the reservoir (maximizing inflow). The I-hour 1 square mile local storm PMP was determined to be 10.4 inches. After adjusting for elevation and areal distribution, the I-hour PMP for Wheatland Reservoir No.2 is 1.97 inches.

After the PMPs were determined, the total runoff and peak inflow for each storm was established. Incremental precipitation was established and incremental runoff determined using a minimum infiltration loss of 0.25 inches/hour. Unit hydrograph procedures, as outlined in the USBR's "Design of Small Dams, 3rd edition", were then used to determine the reservoir inflow hydrograph.

Basin factors used for the general storms were a main channel length of 155.4 miles over a total relief of 5,037 feet resulting in a overall channel slope of 32.41 feet/mile. The contributing drainage area for general storm used in this study was 1,607 square miles. The resulting lag time for the general storm was determined to be approximately 49.5 hours. Using the above information, a unit hydrograph was developed. The unit hydro graph was applied to the incremental runoff and the reservoir inflow hydrograph for the general storm determined. The general storm with a duration of 72-hours results in a peak inflow to Wheatland Reservoir No. 2 of approximately 124,250 cfs with a storm runoff volume of 656,500 acrefeet.

Similarly, the peak inflow for the local storm was determined to be approximately 36,150 cfs with a storm runoff volume of 74,100 acre-feet. Obviously, the most critical storm is the general storm, and therefore it was used as the PMF for this study. A brief examination of general storms of other durations was performed. However, due to the size of the basin

4-5

and associated long lag time of the hydro graph , storms of a duration shorter than the lag time will not produce the critical storm.

As discussed above, the calculated PMF is about 124,250 cfs, which is the event generated by a general storm over the drainage area. The next step was to determine the impact of the PMF occurring on snowmelt. Rather than spend a great deal of time performing a rigorous study, it was noted that the maximum inflow of record to Wheatland Reservoir No.2 was 4,380 cfs, as measured at USGS gage 06-6620.00. The period of record of the gage is May 1912 to December 1917, January 1921 to December 1927, April 1932 to current year (no winter records since 1972), or a period of nearly 70 years. As this peak inflow represents less than four percent of the PMF it was decided to simply consider the 4,380 cfs as a base flow and add the value to the PMF hydrograph. This is considered a very conservative assumption. The total PMF hydrograph used for this study is presented in Table 4.2 and shown graphically on Figure 4-2.

The peak inflow of the PMF determined in this study is almost double of that determined in the 1979 COE report (also used by the SCS in their analysis); 128,600 cfs versus 65,000 cfs. A comparison of pertinent data used to determine a PMF is found on Table 4.3. The two major factors that affected the difference in results are the use of HMR 55A and the assumed initial loss/infiltration rates. HMR 55A was published in 1988 and specifically addresses the Rocky Mountain region, and also tends to produce higher rainfall values than reports previously published. Infiltration rates for extreme flood events are usually assumed to be constant throughout the storm event. It is usually assumed that the ground has been saturated by smaller storms preceding the PMP event. Therefore, no initial loss was assumed for this study. Additionally, the infiltration rate used in the COE report appeared high when compared to soil groups in the basin and their associated loss rate as recommended in the USBR' s "Design of Small Dams". A soil infiltration map presented in "The Missouri River Basin - Comprehensive Framework Study - Infiltration Data" indicates a loss rate for this basin ranging from 0.60 to 2.00 inches per hour at saturation. However, that same report also indicates that infiltration rates used by federal agencies for structure design and flood studies for dams in this vicinity (Glendo, Guernsey, Seminoe, La Prele) ranged from 0.20 to 0.40 inches per hour.

4.3 HYDRAULIC ANALYSIS

In order to analyze the ability of the Wheatland Reservoir No. 2 to store and/or pass a prescribed runoff event, it was necessary to quantify the hydraulic capacities of the main and auxiliary spillways and also that of the primary outlet works. The three small irrigation outlet structures located in the main embankment were not considered in the outlet capacity of this study due to the relatively small capacity of the outlets. A summary of the physical characteristics of each of the structures is presented as Table 4.4.

4-6

TABLE 4.2

Wheatland Reservoir No. 2 Inflow Design Flood

Values in cfs

Time PMF Snowmelt Total No. (Hrs) Hydrograph Hydrograph Hydrograph

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

1 0 0 4,380 4,380 2 6 642 4,380 5,022 3 12 6,948 4,380 11,328 4 18 21,066 4,380 25,446 5 24 42,210 4,380 46,590 6 30 80,286 4,380 84,666 7 36 121,620 4,380 126,000 8 42 124,239 4,380 128,619 9 48 101,931 4,380 106,311

10 54 83,246 4,380 87,626 11 60 71,470 4,380 75,850 12 66 62,810 4,380 67,190 13 72 54,751 4,380 59,131 14 78 47,293 4,380 51,673 15 84 41,159 4,380 45,539 16 90 35,522 4,380 39,902 17 96 31,179 4,380 35,559 18 102 27,573 4,380 31,953 19 108 24,210 4,380 28,590 20 114 21,661 4,380 26,041 21 120 19,389 4,380 23,769 22 126 17,565 4,380 21,945 23 132 16,055 4,380 20,435 24 138 14,637 4,380 19,017 25 142 13,423 4,380 17,803 26 148 12,378 4,380 16,758 27 154 11,166 4,380 15,546 28 160 10,143 4,380 14,523 29 166 9,322 4,380 13,702 30 172 8,485 4,380 12,865 31 178 7,722 4,380 12,102 32 184 6,475 4,380 10,855 33 190 1,444 4,380 5,824 34 196 110 4,380 4,490 35 202 0 4,380 4,380

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TABLE 4.3

Wheatland Reservoir No. 2 Comparison of PMP and PMF Parameters

COE Banner 1979 Rpt. 1989 Rpt.

Technical Reference Unknown HMR-55A

Net PMP (inches) 14.17 " 17.95

PMP Duration 24-Hour 72-Hour

Unit Hydrograph Snyder's USBR

Initial Loss (inches) 2 0

Infiltration Rate 1.3 0.25 (inches/hour)

Contributing Drainage 2,216 1,607 Area (sq mi)

Length, longest 119.9 155.4 watercourse (mi)

Basin Relief (ft) Unknown 5,037

PMF (cfs) 64,960 124,240

4-9

"

TABLE 4.4

Wheatland Reservoir No.2 Summary of the Physical Characteristics

of the Spillways and Outlet Works

AUXILIARY SPILLWAY

Type: Gated Location: Main Embankment Sill Elevation: 6954 MSL Gates: 3-10 Foot High x 12 Foot Wide Slide Gates Bottom Width: Two Bays @ 11.9 Feet Wide and One Bay

at 12.0 Feet Wide Approximate Channel Slope Downstream of Spillway:

0.0003 ft/ft Maximum Gate Opening: 10.3 Feet Capacity at Elevation 6964 (NHWL): 1,520 cfs

MAIN SPILLYAY

Type: Gated Location: North End of Reservoir Sill Elevation: 6956 MSL Gates: 4-7.8 Foot High x 14 Foot Wide Slide Gates Bottom Width: Two Bays @ 14.1 Feet Wide, One Bay @ 14.2

Feet Wide, and One Bay @ 13.7 Feet Wide Approximate Channel Slope Downstream of Spillway:

0.01 ft/ft. Maximum Gate Opening: 6'8" Capacity at Elevation 6964 (NHWL): 4,210 cfs

OUTLET YORKS

Inlet Type: 2-84" Diameter Low Level Pipe to Gate Wet Wells Inlet Elevation: 6935 MSL Control: 4- 5'X 5' gates (two in each wet well) Conduit Type: 2-Corrugated Metal Tunnel Liner Horseshoes Conduit Length: 114 Feet Conduit Size: 6'3" by 5'7" Horseshoe Outlet Invert Elevation: 6935 MSL Capacity at Elevation 6964 (NHWL): 1,320 cfs

4-10

In developing the head/discharge relationship it was assumed that the main and auxiliary gates were fully open, as well as those of the outlet works. In the calculation of the head/discharge relationship, open channel (free flow) conditions existed until the water level rose to the invert of the gate or the top of the outlet pipe, after which pressure flow exists (true for both spillways and the outlet works). It is noted that the Wheatland Irrigation District historically has not operated the outlet canal to Wheatland Reservoir No. 3 at full capacity due to the high erosivity of the canal, but it was assumed the 'WID would operate to capacity during an extreme event storm such as the PMF.

For the open channel (free flow) calculations at the main and auxiliary spillway the effect of the piers was taken into consideration. As stated in Open-Channel Hydraulics (Chow, 1959) "Piers are needed to form the sides of the gates in gated spillways. The effect of the piers is to contract the flow and, hence, to alter the effective crest length of the spillways." The formula used to determine the effective crest length is

L = Lo - KNHe Where: L = Effective Length

Lo = clear span of the gate bay between piers

K pier contraction coefficient (0.04 for thin or pointed noses)

N no. of side contractions, equal to two for each gate bay

At the auxiliary spillway, the downstream channel slope is approximately 0.0003 ft/ft, a very mild slope. As a result, the downstream channel flow will be subcritical creating a submergence effect on the discharge and act as the controlling factor. When pressure flow exists at this spillway, the orifice equation is applicable. At the main spillway, the downstream channel slope is in excess of 0.01 ft/ft. The discharge at the main spillway is structure controlled.

The calculations for the head/discharge relationship for the main spillway, the auxiliary spillway, and the main outlet works are on file at the office of Banner Associates, Inc. The elevation-discharge relationship developed for this study are summarized in Table 4.5 and displayed on Figure 4-3. A direct comparison with the COE report's elevation/discharge relationship for each spillway was unavailable as that report presented a single combined rating curve that incorporated both spillways and the outlet works. A brief comparison of the total discharge curves in the COE study versus this study indicates that this study generally has slightly less discharge values at the lower elevations and slightly higher discharge values at the upper elevations. A comparison of the spillway rating tables for this study and the study performed by the Soil Conservation Service in 1988 is presented as Table 4.6. At the auxiliary spillway it can be seen that the SCS discharges are slightly higher at lower heads (up to elevation 6962). The main difference between the SCS values and the values developed in this study was the use of the effective crest length applied in this study. This SCS apparently used the full gate width opening in developing these values.

4-11

TABLE 4.5

Wheatland Reservoir No. 2 Spillway and Outlet Works

Elevation-Discharge Relationship

Auxiliary Main Outlet Total Elevation Spillway Spillway Works Discharge

(Ft) (cfs) (cfs) (cfs) (cfs) -------------------------------------------------------

6935 0 0 6936 10 10 6937 60 60 6938 125 125 6939 210 210 6940 285 285 6941 330 330 6945 685 685 6950 895 895 6954 0 1,035 1,035 6955 30 1,065 1,095 6956 100 0 1,100 1,200 6957 195 150 1,130 1,475 6958 315 410 1,155 1,880 6959 460 750 1,185 2,395 6960 625 1,150 1,210 2,985 6961 815 1,600 1,240 3,655 6962 1,030 2,090 1,265 4,385 6963 1,265 3,840 1,295 6,400 6964 1,520 4,210 1,320 7,050 6965 4,760 4,550 1,345 10,655 6966 5,050 4,870 1,370 11,290

6966.9 5,300 5,150 1,390 11,840 6967 5,330 5,180 1,395 11,905 6968 5,600 5,470 1,415 12,485 6969 5,850 5,750 1,440 13,040 6970 6,100 6,020 1,460 13,580

6971.5 6,460 6,405 1,495 14,360 6972 6,580 6,530 1,510 14,620 6975 7,250 7,235 1,575 16,060

4-12

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TABLE 4.6

Wheatland Reservoir No.2

Comparison of Rating Curves, Current Study vs. 1988 SCS Study

Auxiliary Spillway Main Spillway ------------------ ---------------

This SCS 88 This SCS 88 Elevation Study Study Study Study

MSL (cfs) (cfs) (cfs) (cfs) --------------------------------------------------------

6955 30 35 0 277 6956 100 111 0 879 6957 195 220 150 1,727 6958 315 358 410 2,796 6959 460 525 750 4,057 6960 625 720 1,150 5,504 6961 815 943 1,600 3,290 6962 1,030 1,194 2,090 3,750 6963 3,840 4,160 6964 4,210 4,533 6965 4,550 4,878 6966 4,870 5,199

6966.5 2,122 6966.9 5,300 5,150

6967 5,180 5,503 6968 5,470 5,791 6969 5,750 6,064 6970 6,020 6,411

6971.5 6,460 3,243 6,405 6,659 6972 6,530 6,976

4-14

For pressure flow at the auxiliary spillway, it can be seen that the discharge values computed in this study are significantly higher than those developed by the SCS. There are several differences in the computations which are discussed, as follows:

1. A "C" value (coefficient of discharge) of 0.75 was used by the SCS, which appears to be too high. In Brater and King, 1976, "C" values are presented and range from a low of 0.487 to a high of 0.628. This study used a "C" value of 0.61.

2. The SCS used a maximum gate opening of 8-feet. At the request of Banner Associates, the Wheatland Irrigation District measured the full gate opening at the auxiliary spillway to be 10.3 feet. The higher gate opening allows more flow through the spillway.

3. A maj or difference appears to be in the interpretation and use of the "head" term in the equation:

Q = Ca(2gh)1/2

Where: Q C a =

g h

discharge, cfs Coefficient of discharge area of opening (sq. ft.) gravitational acceleration head on the center of the orifice or orifices (ft)

In the calculations, using a gate opening of 6-feet (which is what the SCS used), the center of the orifice would be at elevation 6957. The SCS used a very low value for "h" in their calculations. For example, with a water surface level at 6971.5, the SCS used a head of 3.5 feet in their calculations rather than 14.5 feet (6971.5 - 6957).

At the main spillway, there are also some differences in the discharges. As with the auxiliary spillway, an effective length rather than the full gate width was used when the discharge was under free flow conditions. A maj or difference resulted from the SCS using a sill elevation of 6954 (apron elevation) and did not account for the 2-foot concrete sill beneath the gates (top of sill 6956). Another major difference in the calculations for discharge at the main spillway was that the SCS used channel control to determine the discharge for pressure flow conditions. The effect of this assumption can be seen on Table 4.6, at the transition point between free flow and pressure flow (elevation 6961). At elevation 6960 the SCS discharge was 5,504 cfs and decreased to 3,290 cfs at elevation 6962 (pressure flow). This cannot physically occur. The other difference was that the SCS used a full gate opening of 6-feet, while the measured gate opening was 6'8".

The head discharge relationship for the outlet works was developed using free flow conditions until the pipe was full and then using the energy equation once the conduit was pressurized.

4-15

4.4 FLOOD ROUTING

Following the PMF determination and the hydraulic analysis, flood routings were performed for the 25% PMF, the 50% PMF, and the Full PMF. The 25% and 50% storm hydrographs were obtained by multiplying each point of PMF hydrograph, described previously, by the appropriate percent. Three reservoir routing scenarios were performed for each of the storms listed above: 1) without the dam in place; 2) with the dam in place; and 3) with the dam in place and failure of the dam. For all reservoir routings, it was assumed the reservoir level was at the top of the spillway gates (elevation 6964) at the start of the storm. This represents a conservative but probable assumption; a PMF would most likely be preceded by a series of smaller storms possibly in the spring or early summer months. The COE report analysis as well as the SCS analysis both assumed a reservoir starting elevation of 6954. Based on historic end-of-month storage records (see Table 6.1), the reservoir was above this elevation approximately 42% of the time. Due to that fact and the reasons stated previously, this study maintained the use of the normal high water line (full reservoir) as a reservoir starting elevation. For the reservoir routings, it was assumed that the auxiliary spillway capacity would be fully utilized even though this may result in damage to the Supply Canal to Wheatland Reservoir No.3. The assumption was that it would be more prudent to risk damage to the canal than to risk overtopping and failure of Wheatland Reservoir No.2.

A limited analysis was performed to evaluate if a differential elevation would exist between the two spillways during an incoming flood wave, and what potential effect a differential elevation may have. An early concern was expressed that this condition may exist due to the length of the reservoir from the point of inflow. The auxiliary spillway is located approximately 5.5 miles from where the Laramie River enters the reservoir while the main spillway is at the extreme north end of the reservoir approximately 6.8 miles beyond the auxiliary spillway, as illustrated on Figure 2-2.

In order for a differential elevation to exist, there must be a veloci ty through the reservoir area. As noted previously, the critical storm for Wheatland Reservoir No. 2 would result from a general storm. The contributing area for Wheatland Reservoir No.2 is relatively large, and as a result the time to peak for an incoming flood develops over a long period of time (42 hours for the PMF) and there is no true "flood wave" entering the reservoir. Combining this fact with the large reservoir volume and surface area results in a negligible velocity through the reservoir. Therefore, no differential elevations are expected to occur during an extreme event general storm.

Procedures and assumption used for each scenario are described in detail below. The outflow hydro graph from each of the reservoir routings was then routed down the Laramie River to its intersection with Interstate Highway 25 (1-25) North of Wheatland. Summary tables of results are included as referenced below. However, due to the volume, complete input and output files are not included but are available at Banner Associates, Inc. office.

4-16

4.4

.1

With

ou

t th

e

Dam

in

P

lace

Fo

r th

is

scen

ario

it

was

assum

ed

that

the

main

em

ban

km

ent

had

n

ev

er

been

co

nstru

cte

d,

as

well

as

the

Su

pp

ly

Can

al to

W

heatla

nd

R

ese

rvo

ir N

o. 3

and

th

e

ch

an

nel

cu

t in

th

e

reserv

oir

basin

to

d

rain

w

ate

r th

rou

gh

a

hig

h

are

a

in

the

reserv

oir

basin

fro

m

the

no

rth

en

d

of

the

reserv

oir

tow

ard

s th

e

ou

tlet w

ork

s. A

rev

iew

o

f th

e re

serv

oir b

asin

co

nto

urs

as

pre

sen

ted

to

th

e

Sta

te

En

gin

eer's

Offic

e

in

the

orig

inal

perm

it ap

plic

atio

n

sho

ws

that

little,

if

an

y,

wate

r w

ou

ld

get

to

the

no

rth

en

d o

f th

e

reserv

oir

with

ou

t th

e

ch

an

nel

cu

t in

th

e b

asin

.

Th

e in

flow

d

esig

n

floo

d

was

rou

ted

fro

m

the

up

stream

en

d o

f th

e

reserv

oir

do

wn

stream

to

1-2

5.

Th

e ro

utin

g

was

perfo

rmed

u

sing

th

e

co

mp

ute

r p

rog

ram

HE

C-l,

with

th

e

ch

an

nel

cro

ss-s

ectio

ns

ob

tain

ed

fro

m

USG

S 7

.5

min

ute

q

uad

s. T

here

are

sev

era

l sm

all

brid

ges

and

cu

lverts

lo

cate

d

on

th

e

Laram

ie R

iver

do

wn

stream

of

the

reserv

oir.

In

this

stu

dy

, it

was

assum

ed

that

the

back

wate

r effe

ct

of

the

brid

ges

and

cu

lverts

w

ere m

ino

r re

lativ

e

to

the

mag

ni tu

de

of

the

floo

d.

By

mak

ing

th

is

assu

mp

tion

it

was

un

necessa

ry

to

use

a

back

wate

r co

mp

ute

r p

rog

ram

(such

as

HE

C-2

). T

here

is

a

tun

nel

locate

d

ad

j acen

t to

th

e

Laram

ie R

iver

do

wn

stream

of

the

reserv

oir

wh

ich

div

erts

L

ara

mie

R

iver

wate

r to

B

lueg

rass

Cre

ek

. F

or

this

stu

dy

it

was

assum

ed

that

the

tun

nel

was

clo

sed

an

d

no

w

ate

r w

as d

iverte

d

from

th

e

Laram

ie R

iver.

Th

e re

su

lts

of

this

sc

en

ario

in

dic

ate

th

at

very

little

atte

nu

atio

n

occu

rs b

etw

een

th

e

Wh

eatla

nd

R

ese

rvo

ir N

o. 2

dam

site

an

d

1-2

5.

Th

is is

la

rgely

d

ue

to

the

mag

nitu

de

of

these

flo

od

s, an

d

the

steep

ch

an

nel

slop

e

and

co

nfin

ed

flo

od

pla

in

are

a

for

much

of

this

re

ach

. T

he

stream

ro

utin

g

sum

mary

ta

ble

s

(ind

icatin

g

peak

flo

w,

maxim

um

sta

ge,

and

m

aximum

d

ep

th

for

each

sectio

n)

for

this

an

d th

e o

ther

scen

ario

s are

p

rese

nte

d in

Tab

les

4.7

, 4

.8,

and

4

.9

for

the

25%

PMF,

50%

PMF,

and

F

ull

PMF,

resp

ectiv

ely

. A

s a

no

te,

Mile

1

18

4.5

7

is ju

st

belo

w

the

dam,

and

S

ectio

n

27 (M

ile

11

21

.14

) is

slig

htly

d

ow

nstream

o

f 1

-25

. A

lso,

Ap

pen

dix

A

co

nta

ins

cro

ss-s

ectio

ns

plo

ts

of

each

sectio

n

liste

d

in

the

summ

ary ta

ble

s.

Th

ree

sets

o

f p

lots

are

p

rese

nte

d,

co

rresp

on

din

g

to

the

thre

e

storm

s an

aly

zed

, w

ith

each

sectio

n illu

stra

ting

th

e

floo

d le

vels

fo

r all

thre

e

scen

ario

s.

4.4

.2

With

th

e

Dam

in

Pla

ce

In

this

sc

en

ario

it

was

assum

ed

that

the

main

dam

em

ban

km

ent

and

th

e

main

sp

illway

em

ban

km

ent

wo

uld

be

ov

erto

pp

ed

with

ou

t fa

ilure

. F

or

this

sc

en

ario

th

e

Co

rps

of

En

gin

eers

co

mp

ute

r p

rog

ram

"Natio

nal

Insp

ectio

n

of

Dam

s, H

yd

rolo

gic

A

naly

sis P

rog

ram"

was

use

d.

As

sta

ted

in

th

e

users

m

anu

al liT

he co

mp

uted

h

yd

rog

rap

h

can

th

en

b

e

rou

ted

th

rou

gh

a

reserv

oir.

If th

e

dam is

o

verto

pp

ed

, th

e

pro

gram

w

ill re

du

ce

the

com

pu

ted

hy

dro

gra

ph

in

10%

in

cre

men

ts o

f th

e

orig

inal

storm

an

d

rero

ute

th

rou

gh

th

e

stru

ctu

re

un

til th

e

dam

is

no

t o

verto

pp

ed

."

In

this

p

rog

ram,

the

user

defin

es

the

ou

tlet

ratin

g

tab

le,

wh

ich

fo

r th

is

stud

y

inclu

des

the

main

an

d

au

xilia

ry

spillw

ay

s an

d

the

ou

tlet

wo

rks.

Th

e u

ser

als

o

defin

es

the

spillw

ay

ch

ara

cte

ristic

s

and

th

e

dam

ov

erto

pp

ing

ch

ara

cte

ristic

s.

In th

is

stud

y

the

spillw

ay

was

defin

ed

as

the

main

sp

illway

an

d asso

cia

ted

em

ban

km

ent

4-1

7

TABLE 4.7

WHEATLAND RESERVOIR NO. 2 25% PMF

CROSS-SECTION PEAK FLOWS AND DEPTHS

No Dam Dam, No With Dam Failure Failure

Channel Peak Q Max Peak Q Max Peak Q Max Mile Bottom (cfs) Stage Depth (cfs) Stage Depth (cfs) Stage Depth

Inflow 32155 Damsite 1184.57 6935 31944 6947.1 7110 12140 Sec 1 1183.32 6930 31928 6943.3 13.3 7109 6937.6 7.6 12137 6939.2 9.2

2 1181.32 6925 31846 6940.5 15.5 7108 6933.7 8.7 12134 6935.7 10.7 3 1179.30 6920 31800 6936.0 16.0 7108 6927.9 7.9 12132 6930.3 10.3 4 1176.32 6908 31733 6935.6 27.6 7107 6917.1 9.1 12131 6919.8 11.8

~ 5 1174.32 6903 31695 6920.8 17.8 7107 6912.1 9.1 12130 6914.6 11.6 I ........ 6 1173.59 6893 31696 6907.4 14.4 7107 6899.7 6.7 12130 6901.8 8.8 00

7 1172.95 6887 31695 6904.8 17.8 17306 6900.3 13.3 17750 6900.5 13.5 8 1172.32 6882 31690 6894.8 12.8 17305 6891.9 9.9 17750 6892.0 10.0 9 1171.63 6873 31686 6888.2 15.2 17305 6884.1 11.1 17750 6884.2 11.2

10 1170.32 6828 31688 6838.7 10.7 17304 6835.6 7.6 17750 6835.7 7.7 11 1168.32 6688 31689 6698.3 10.3 17301 6695.4 7.4 17750 6695.5 7.5 12 1166.12 6578 31687 6590.9 12.9 17302 6586.8 8.8 17750 6586.9 8.9 13 1161.89 6458 31674 6473.4 15.4 17297 6468.8 10.8 17750 6469.0 11.0 14 1161.81 6438 31674 6447.9 9.9 17297 6445.8 7.8 17750 6445.9 7.9 15 1160.66 6403 31675 6426.1 23.1 17296 6420.5 17.5 17750 6420.8 17.8 16 1156.93 6113 31667 6131.4 18.4 17294 6126.3 13.3 17749 6126.4 13.4 17 1153.32 5708 31663 5726.6 18.6 17294 5721.5 13.5 17749 5721.7 13.7 18 1149.90 5338 31660 5353.9 15.9 17292 5349.7 11.7 17749 5349.8 11.8 19 1144.43 4953 31644 4965.0 12.0 17289 4962.6 9.6 17749 4962.7 9.7 20 1143.77 4918 31645 4932.4 14.4 17289 4929.3 11.3 17749 4929.4 11.4 21 1142.76 4872 31643 4885.9 13.9 17289 4882.8 10.8 17749 4882.9 10.9 22 1142.32 4861 31641 4872.8 11.8 17289 4870.7 9.7 17749 4870.8 9.8 23 1138.32 4733 31599 4741.7 8.7 17280 4740.4 7.4 17748 4740.5 7.5 24 1132.05 4610 31415 4618.6 8.6 17257 4617.5 7.5 17745 4617.6 7.6 25 1129.77 4592 31383 4602.3 10.3 17249 4600.6 8.6 17744 4600.7 8.7 26 1125.32 4521 31249 4531.9 10.9 17236 4530.1 9.1 17742 4530.2 9.2 27 1121.14 4482 31105 4494.3 12.3 17221 4491.7 9.7 17740 4491.8 9.8

TABLE 4.8

WHEATLAND RESERVOIR NO. 2 50% PMF




Inflow 64310 Damsite 1184.57 6935 63991 6949.8 13070 13320 Sec 1 1183.32 6930 63955 6947.1 17.1 13058 6939.5 9.5 13236 6939.6 9.6

2 1181.32 6925 63839 6945.2 20.2 13040 6936.1 11.1 13143 6936.1 11.1 3 1179.30 6920 63765 6941.8 21.8 13026 6930.6 10.6 13134 6930.7 10.7 4 1176.32 6908 63687 6931.4 23.4 13006 6920.1 12.1 13123 6920.1 12.1

~ 5 1174.32 6903 63635 6927.0 24.0 12991 6915.0 12.0 13118 6915.1 12.1 I I--' 6 1173.59 6893 63640 6913.1 20.1 12990 6902.1 9.1 13118 6902.2 9.2 1.0

7 1172.95 6887 63642 6911.1 24.1 46389 6908.2 21.2 48490 6908.6 21.6 8 1172.32 6882 63638 6899.3 17.3 46393 6897.4 15.4 48483 6897.7 15.7 9 1171.63 6873 63635 6894.9 21.9 46392 6891.6 18.6 48475 6892.0 19.0

10 1170.32 6828 63628 6843.5 15.5 46384 6841.2 13.2 48478 6841.5 13.5 11 1168.32 6688 63624 6702.4 1!+.4 46379 6700.6 12.6 48476 6700.8 12.8 12 1166.12 6578 63628 6596.9 18.9 46380 6593.7 15.7 48467 6594.1 16.1 13 1161.89 6458 63600 6479.2 21.2 46356 6476.1 18.1 48447 6476.5 18.5 14 1161.81 6438 63599 6452.7 14.7 46357 6450.1 12.1 48447 6450.4 12.4 15 1160.66 6403 63594 6434.7 31.7 46357 6430.2 27.2 48448 6430.8 27.8 16 1156.93 6113 63600 6138.4 25.4 46347 6134.9 21.9 48445 6135.3 22.3 17 1153.32 5708 63597 5732.7 24.7 46347 5729.9 21.9 48439 5730.2 22.2 18 1149.90 5338 63585 5358.5 20.5 46341 5356.4 18.4 48439 5356.6 18.6 19 1144.43 4953 63574 4969.2 16.2 46329 4967.2 14.2 48427 4967.5 14.5 20 1143.77 4918 63574 4936.9 18.9 46327 4934.8 16.8 48426 4935.2 17.2 21 1142.76 4872 63571 4889.8 17.8 46322 4887.7 15.7 48423 4887.9 15.9 22 1142.32 4861 63567 4876.5 15.5 46324 4874.5 13.5 48423 4874.7 13.7 23 1138.32 4733 63526 4743.9 10.9 46282 4742.9 9.9 48399 4743.0 10.0 24 1132.05 4610 63355 4621.1 11.1 46078 4619.8 9.8 48282 4620.0 10.0 25 1129.77 4592 63300 4604.8 12.8 46050 4603.5 11.5 48264 4603.7 11.7 26 1125.32 4521 63105 4534.7 13.7 45980 4533.6 12.5 48227 4533.7 12.7 27 1121.14 4482 62894 4497.6 15.6 45898 4495.9 13.9 48183 4496.1 14.1

TABLE 4.9

WHEATLAND RESERVOIR NO. 2 FULL PMF




Inflow 128619 Damsite 1184.57 6935 128084 6953.2 18.2 78205 74892 Sec 1 1183.32 6930 128008 6952.0 23.0 77401 6948.4 18.4 74840 6948.2 18.2

2 1181.32 6925 127820 6950.7 25.7 76400 6946.5 21.5 74718 6946.3 21.3 3 1179.30 6920 127733 6949.2 29.2 75970 6943.6 23.6 74638 6943.4 23.4 4 1176.32 6908 127629 6938.9 30.9 75525 6933.0 25.0 74535 6932.9 24.9

~ 5 1174.32 6903 127562 6935.5 32.5 75347 6928.7 25.7 74483 6928.6 25.6 I N 6 1173.59 6893 127565 6920.8 27.8 75346 6914.8 21.8 74478 6914.7 21.7 0

7 1172.95 6887 127564 6919.1 32.1 122474 6918.6 31.6 123833 6918.7 31.7 8 1172.32 6882 127557 6904.8 22.8 122463 6904.8 22.8 123842 6904.9 22.9 9 1171.63 6873 127550 6904.0 31.0 122464 6903.4 30.4 123840 6903.6 30.6

10 1170.32 6828 127537 6850.0 22.0 122459 6849.6 21.6 123824 6849.7 21.7 11 1168.32 6688 127528 6708.2 20.2 122452 6707.8 19.8 123803 6707.9 19.9 12 1166.12 6578 127538 6605.2 27.2 122448 6604.7 26.7 123781 6604.8 26.8 13 1161.89 6458 127510 6487.2 29.2 122372 6486.6 28.6 123721 6486.7 28.7 14 1161.81 6438 127511 6457.7 19.7 122373 6457.3 19.3 123716 6457.4 19.4 15 1160.66 6403 127502 6446.0 43.0 122369 6445.3 42.3 123709 6445.5 42.5 16 1156.93 6113 127483 6148.5 35.5 122355 6147.8 34.8 123690 6148.0 35.0 17 1153.32 5708 127492 5741.2 33.2 122342 5740.7 32.7 123692 5740.8 32.8 18 1149.90 5338 127493 5365.3 27.3 122332 5364.9 26.9 123673 5365.0 27.0 19 1144.43 4953 127453 4975.5 22.5 122280 4975.0 22.0 123629 4975.1 22.1 20 1143.77 4918 127445 4942.6 24.6 122280 4942.2 24.2 123616 4942.3 24.3 21 1142.76 4872 127450 4895.2 23.2 122269 4894.8 22.8 123597 4894.9 22.9 22 1142.32 4861 127454 4880.4 19.4 122272 4880.1 19.1 123590 4880.2 19.2 23 1138.32 4733 127386 4747.0 14.0 122116 4746.8 13.8 123436 4746.8 13.8 24 1132.05 4610 127184 4623.7 13.7 121568 4623.5 13.5 122986 4623.6 13.6 25 1129.77 4592 127107 4608.5 16.5 121454 4608.2 16.2 122941 4608.3 16.3 26 1125.32 4521 126984 4538.2 17.2 121171 4538.0 17.0 122819 4538.0 17.0 27 1121.14 4482 126830 4501.8 19.8 120834 4501.5 19.5 122675 4501.6 19.6

overtopping with the overtopping characteristics assigned to the main spillway embankment. The model was then run to route the 25% PMF, 50% PMF, and Full PMF through the reservoir. The summary results of the reservoir routings are presented in Tables 4.10, 4.11, and 4.12, respectively. As can be seen, the main embankment is able to contain and pass a storm of somewhat less than a 50% PMF event.

As a part of the output, the information shown in Table 4.13 is printed which defines the outlet, spillway and over top of dam discharges relative to elevation. Also, as a part of the output, the outflow hydrograph (time versus discharge) is printed. It was necessary for HEC-l input (downstream routing analysis) to segregate flows to that discharging through the main spillway area and that discharging into the Laramie River directly below the dam. To determine the location of the outflow from the reservoir (outlet works, spillways, and/or overtopping), the outflow hydrograph stage was compared against Table 4.13. The segregation was further refined by comparing the stage to the elevation/discharge relationships presented in Table 4.6. The outflow hydrographs and flow segregation for the 25%, 50%, and 100% PMF's are presented in Tables 4.14, 4.15, and 4.16, respectively.

The segregated outflow hydrograph was then input into the HEC-l computer program to define the flood inundation limits. The major assumption that was made in the downstream routing was that the outflow from the main embankment would be directly input into the Laramie River. This is a conservative assumption as in actuality some of the outflow could be delivered to Wheatland Reservoir No.3. As before, the tunnel to Bluegrass Creek was assumed to be closed.

As noted for the previous scenario, the downstream routing results from the dam to 1-25 are presented in Tables 4.7, 4.8, and 4.9.

4.4.3 With the Dam in Place and Failure of the Dam

For this scenario, the dam breach outflow hydrograph was estimated using the National Weather Service Breach computer program (7/88 version). As stated in the users manual the program is "A physically based mathematical model to predict the breach characteristics (size, time of formation) and the discharge hydro graph emanating from a breached earthen dam is presented ... The model is developed by coupling the conservation of mass of the reservoir inflow, spillway outflow, and breach outflow with the sediment transport capacity of the unsteady uniform flow along an erosionformed breach channel ... The growth of the breach channel is dependent on the dam's material properties (D50 size, unit weight, friction angle, cohesive strength)." A sensitivity analysis was performed for the various properties required for input into the model to max~m~ze the breach outflow. For Wheatland Reservoir No.2, the model was relatively insensitive to most of the input parameters, probably due to the relatively low dam height, backwater effects, and magnitude of the peak inflow.

4-21

~ I

N N

TABLE 4.10

*********************************************************************************************************************** DAM INSPECTION HYDROLOGIC ANALYSIS - SUMMARY TABLE ***********************************************************************************************************************

Wheatland Reservoir No.2 Routing of Inflow Design Flood (1/4) Input Calculated Inflow Design Flood Spill Represents Embankment OVertopping at Main Spillway Spillways and OUtlet Works Discharge Included in OUtflow Rating

INPUT LAKE INFLOW HYDROGRAPH ORDINATES IN CFS AT 6.000 HOUR INTERVALS BEGINNING AT ZERO TIME 1098.0 1256.0 2832.0 6362.0 11648.0 21167.0 31500.0 32155.0 26578.0 21907.0 18963.0 16798.0

14783.0 12919.0 11385.0 9976.0 8890.0 7989.0 7148.0 6511.0 5943.0 5487.0 5109.0 4755.0 4451.0 4190.0 3887.0 3631.0 3426.0 3217.0 3026.0 2714.0 1456.0 1123.0 1095.0 -------------------------------------------- LAKE AND DAM INFORMATION ----------------------_.---------------------BEGINNING OUTLET BOTTOM SPILLWAY SPILLWAY TOP OF DAM TOP OF DAM HEIGHT DOWNSTREAM N-VALVE COEF OF POOL ELEV INVERT OF LAKE CREST CREST WIDTH ELEVATION LENGTH OF DAM SLOPE ON OS FLOW

FT,MSL FT,MSL FT,MSL FT,MSL FEET FT,MSL FEET FEET OF DAM SLOPE OVER DAM

6964.00 6935.00 6935.00 6966.90 875.0 6971.50 8030.0 36.5 1V ON 2.00H 0.030 2.90

------------------------ SUMMARY OF FLOOD ROUTINGS OF INFLOW HYDROGRAPH THROUGH THE LAKE --------------------------ROUTING PERCENT TOTAL MAXIMUM DEPTH OF ESTIMATED INITIAL TOTAL VOLUME MAXIMUM NUMBER OF LAKE INFLOW LAKE LAKE OVER VELOCITIES TIME TO TIME SPILLED DISCHARGE

INFLOW VOLUME ELEVATION TOP OF DAM CREST TOE OVER TOP OVER DAM OVER DAM FROM DAM HYDROGRAPH AC-FT FT,MSL FEET FPS FPS HOUR HOURS AC-FT CFS

100.0 161345. 6968.46 -3.04 0.00 0.00 0.00 0.00 0.0 17826.0

TABLE 4. 11

*********************************************************************************************************************** DAM INSPECTION HYDROLOGIC ANALYSIS - SUMMARY TABLE ***********************************************************************************************************************

Wheatland Reservoir No. 2 Routing of Inflow Design Flood (1/2 PMF) Input Calculated Inflow Design Flood Spill Represents Embankment Overtopping at Main Spillway Spillways and OUtlet Works Discharge Included in OUtflow Rating

INPUT LAKE INFLOW HYDROGRAPH ORDINATES IN CFS AT 6.000 HOUR INTERVALS BEGINNING AT ZERO TIME 2195.0 2511.0 5664.0 12723.0 23295.0 42333.0 63000.0 64310.0 53156.0 43813.0 37925.0 33595.0

29566.0 25837.0 22770.0 19951.0 17780.0 15977.0 14295.0 13021.0 11885.0 10973.0 10218.0 9509.0 8902.0 8379.0 7713.0 7262.0 6851.0 6433.0 6051.0 5428.0 2912.0 2245.0 2190.0 -------------------------------------------- LAKE AND DAM INFORMATION ---------------------------------------------BEGINNING OUTLET BOTTOM SPILLWAY SPILLWAY TOP OF DAM TOP OF DAM HEIGHT DOWNSTREAM N-VALVE COEF OF POOL ElEV INVERT OF LAKE CREST CREST WIDTH ELEVATION LENGTH OF DAM SLOPE ON DS FLOW


6964.00 6935.00 6935.00 6966.90 875.0 6971.50 8030.0 36.5 1V ON 2.00H 0.030 2.90

------------------------ SUMMARY OF FLOOD ROUTINGS OF INFLOW HYDROGRAPH THROUGH THE LAKE --------------------------ROUTING PERCENT TOTAL MAXIMUM DEPTH OF ESTIMATED INITIAL TOTAL VOLUME MAXIMUM NUMBER OF LAKE INFLOW LAKE LAKE OVER VELOCITIES TIME TO TIME SPILLED DISCHARGE

1 2

INFLOW VOLUME ELEVATION TOP OF DAM CREST TOE OVER TOP OVER DAM OVER DAM FROM DAM HYDROGRAPH AC-FT FT,MSL FEET FPS FPS HOUR HOURS AC-FT CFS

100.0 90.0

322680. 6971.96 290412. 6971.47

0.46 -0.03

3.16 7.89 0.00 0.00

50.54 0.00

17.31 0.00

9458.3 0.0

48603.7 41759.5

+:-I

N +:--

TABLE 4.12

*********************************************************************************************************************** DAM INSPECTION HYDROLOGIC ANALYSIS· SUMMARY TABLE ***********************************************************************************************************************

Uheatland Reservoir No.2 Routing of Inflow Design Flood Input Calculated Inflow Design Flood Spill Represents Embankment Overtopping at Main Spillway Spillways and OUtlet Works Discharge Included in Outflow Rating

IH~T LAKE INFLOW HYDROGRAPH ORDINATES IN CFS AT 6.000 HOUR INTERVALS BEGINNING AT ZERO TIME 4390.0 . 5022.0 11328.0 25446.0 46590.0 84666.0 126000.0 128619.0 106311.0 87626.0 75850.0 67190.0

59131.0 51673.0 45539.0 39902.0 35559.0 31953.0 28590.0 26041.0 23769.0 21945.0 20435.0 19017.0 17803.0 16758.0 15546.0 14523.0 13702.0 12865.0 12102.0 10855.0 5824.0 4490.0 4380.0

....••..•. - •.• - ..•••.••••.•••.....•..•• _ •.•. LAKE AND DAM INfORMATION ... -..•.......•...•...•.•••••••••...••.•••••• BEGINNING OUTLET BOTTOM SPILLWAY SPILLWAY TOP OF DAM TOP OF DAM HEIGHT DOWNSTREAM N·VALVE COEF OF POOL ELEV INVERT OF LAKE CREST CREST WIDTH ELEVATION LENGTH OF DAM SLOPE ON OS FLOW


6964.00 6935.00 6935.00 6966.90 875.0 6971.50 8030.0 36.5 1V ON 2.00H 0.030 2.90

- .•••••••• _ ••••••••••••• SUMMARY OF FLOOD ROUTINGS OF INFLOW HYDROGRAPH THROUGH THE LAKE ...•••••••••••.•••.•••..•. ROUTING PERCENT TOTAL MAXIMUM DEPTH OF ESTIMATED INITIAL TOTAL VOLUME MAXIMUM NUMBER OF LAKE INflOW LAKE LAKE OVER VelOCITIES TIME TO TIME SPILLED DISCHARGE

I.:FLOW VOLUME ElEVATION TOP OF DAM CREST TOE OVER TOP OVER DAM OVER DAM FROM DAM HYDROGRAPH AC·FT FT ,MSL FEET FPS FPS HOUR HOURS AC·n CFS

1 100.0 645352. 6973.64 2.14 6.78 19.75 38.90 61.15 189666.2 126657.5 2 90.0 580816. 6973.40 1.90 6.39 18.38 40.13 54.97 146863.8 113358.9 3 80.0 516281. 6973.14 1.64 5.94 16.85 41.57 48.08 106562.8 99252.7 4 70.0 451746. 6972.83 1.33 5.34 14.83 43.37 40.14 69310.0 84097.1 5 60.0 387211. 6972.45 0.95 4.52 12.12 46.02 30.32 36115.6 68075.1 6 50.0 322676. 6971.96 0.46 3.16 7.89 50.54 17.31 9457.3 48603.7 7 40.0 258141. 6970.91 -0.59 0.00 0.00 0.00 0.00 0.0 34414.1

TABLE 4 e 13

*********************.***********************.*********.***********************************.*****.****************.**** DAM INSPECTION HYDROLOGIC ANALYSIS - LAKE ELEVATIONS, STORAGES AND DISCHARGE RATING TABLES ********************************.************ •• ****.*.********.* ••• ***.*** ••• *.**** ••• ** ••• ***** •• ****.******.** ••••• *.

Wheatland Reservoir No. 2 (1) (2) (3) LAKE LAKE STORAGE PLUS OUnET SPillWAY OVER TOP TOTAL

elEVATION STORAGE HALF DISCHARGE DISCHARGE DISCHARGE OF DAM DISCHARGE FT ,MSL AC-FT AC-FT C.F.S. C.F.S. C.F.S. C.F.S.

6975.000 184940.000 237575.125 16055.000 58483.586 137753.266 212291.859 6974.000 175675.203 2119n.469 15576.667 47991.398 82848.898 146416.969 6973.000 166841. 781 189474.578 15098.333 38214.129 37971.844 91284.305 6972.000 158421.047 170596.813 14620.000 29208.451 5279.749 49108.203 6971.000 150212.906 158927.203 14100.000 21047.107 0.000 35147.109 6970.000 142232.375 149027.969 13580.000 13828.537 0.000 27408.537 6969.000 134591.000 139732.453 13040.000 7696.869 0.000 20736.869 6968.000 127019.219 130832.664 12485.000 2895.666 0.000 15380.666 6967.000 119820.000 122n8.000 11905.000 25.427 0.000 11930.428 6966.000 112436.578 115235.789 11290.000 0.000 0.000 11290.000 6965.000 105482.289 108124.063 10655.000 0.000 0.000 10655.000 6964.000 98934.000 100681.961 7050.000 0.000 0.000 7050.000 6963.000 92050.664 93637.461 6400.000 0.000 0.000 6400.000 6962.000 85598.570 86685.773 4385.000 0.000 0.000 4385.000 6961.000 79620.836 80527.047 3655.000 0.000 0.000 3655.000 6960.000 74040.000 74780.094 2985.000 0.000 0.000 2985.000

~ 6959.000 67925.250 68519.063 2395.000 0.000 0.000 2395.000 I 6958.000 62376.781 62842.902 1880.000 0.000 0.000 1880.000

N 6957.000 57225.277 57590.984 1475.000 0.000 0.000 1475.000 V1

6956.000 52516.402 52813.926 1200.000 0.000 0.000 1200.000 6955.000 48195.000 48466.492 1095.000 0.000 0.000 1095.000 6954.000 43581.000 43837.617 1035.000 0.000 0.000 1035.000 6953.000 39008.336 39256.273 1000.000 0.000 0.000 1000.000 6952.000 34915.430 35154.688 965.000 0.000 0.000 965.000 6951.000 31238.723 31469.305 930.000 0.000 0.000 930.000 6950.000 27961.000 28182.904 895.000 0.000 0.000 895.000 6949.000 24554.494 24765.984 853.000 0.000 0.000 853.000 6948.000 21573.684 21774.762 811.000 0.000 0.000 811.000 6947.000 18945.324 19135.988 769.000 0.000 0.000 769.000 6946.000 16628.947 16809.197 727.000 0.000 0.000 727.000 6945.000 14603.000 14772.837 685.000 0.000 0.000 685.000 6944.000 12151.076 12298.909 596.250 0.000 0.000 596.250 6943.000 10103.731 10229.560 507.500 0.000 0.000 507.500 6942.000 8407.246 8511.070 418.750 0.000 0.000 418.750 6941.000 6995.612 7077.432 330.000 0.000 0.000 330.000 6940.000 5821.000 5891.662 285.000 0.000 0.000 285.000 6939.000 3676.122 3728.188 210.000 0.000 0.000 210.000 6938.000 2325.617 2356.610 125.000 0.000 0.000 125.000 6937.000 1473.813 1488.690 60.000 0.000 0.000 60.000 6936.000 934.000 936.479 10.000 0.000 0.000 10.000 6935.000 0.000 0.000 0.000 0.000 0.000 0.000

(1) Includes Outlet Works, Nain Spillway and AuxilIary Spillway (2) Overtopping Discharge at Main Spillway (3) Overtopping Discharge at Main Embankment

TABLE 4.14

Wheatland Reservoir No. 2 25% PMF - No Dam Failure

Outflow Hydrograph and Flow Segregation Total (1)

Main Main Main Discharge Total Spillway Spillway Spillway Below the

Time Discharge Elevation Discharge Overtop Discharge Dam (Hrs) (cfs) (MSL) (cfs) (cfs) (cfs) (cfs)

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

6 6,770 6963.57 4,055 0 4,055 2,715 12 6,515 6963.18 3,910 0 3,910 2,605 18 6,125 6962.86 3,790 0 3,790 2,335 24 5,940 6962.77 3,755 0 3,755 2,185 30 6,410 6963.01 3,845 0 3,845 2,565 36 6,890 6963.75 4,120 0 4,120 2,770 42 10,730 6965.12 4,590 0 4,590 6,140 48 11,645 6966.56 5,045 0 5,045 6,600 54 14,260 6967.67 5,375 1,715 7,090 7,170 60 16,700 6968.25 5,545 3,980 9,525 7,175 66 17,735 6968.44 5,600 4,850 10,450 7,285 72 17,725 6968.44 5,600 4,850 10,450 7,275 78 17,105 6968.32 5,560 4,295 9,855 7,250 84 16,100 6968.13 5,510 3,460 8,970 7,130 90 15,045 6967.90 5,445 2,540 7,985 7,060 96 14,100 6967.63 5,365 1,585 6,950 7,150

102 13,100 6967.34 5,280 740 6,020 7,080 108 12,100 6967.05 5,195 150 5,345 6,755 114 11,775 6966.76 5,105 0 5,105 6,670 120 11,565 6966.43 5,005 0 5,005 6,560 126 11,340 6966.08 4,900 0 4,900 6,440 132 11,090 6965.69 4,775 0 4,775 6,315 138 10,835 6965.28 4,640 0 4,640 6,195 142 10,170 6964.86 4,500 0 4,500 5,670 148 8,835 6964.49 4,375 0 4,375 4,460 154 7,750 6964.19 4,275 0 4,275 3,475 160 7,015 6963.95 4,190 0 4,190 2,825 166 6,865 6963.72 4,105 0 4,105 2,760 172 6,715 6963.48 4,020 0 4,020 2,695 178 6,560 6963.24 3,930 0 3,930 2,630 184 6,400 6963.00 3,845 0 3,845 2,555 190 5,890 6962.75 3,750 0 3,750 2,140 196 5,335 6962.47 2,340 0 2,340 2,995 202 4,750 6962.18 2,190 0 2,190 2,560 208 4,325 6961.91 2,045 0 2,045 2,280 214 4,100 6961.61 1,895 0 1,895 2,205 220 3,855 6961.28 1,735 0 1,735 2,120 226 3,630 6960.96 1,580 0 1,580 2,050 232 3,420 6960.65 1,440 0 1,440 1,980 238 3,225 6960.35 1,305 0 1,305 1,920 244 3,035 6960.08 1,190 0 1,190 1,845 250 2,885 6959.83 1,080 0 1,080 1,805 258 2,750 6959.60 985 0 985 1,765 264 2,620 6959.38 900 0 900 1,720

(1) Includes auxiliary spillway, outlet works

4-26

TABLE 4.15

Wheatland Reservoir No. 2 50% PMF - No Dam Failure




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

6 6,800 6963.61 4,070 0 4,070 2,730 12 6,600 6963.30 3,955 0 3,955 2,645 18 6,490 6963.14 3,895 0 3,895 2,595 24 6,630 6963.35 3,975 0 3,975 2,655 30 7,775 6964.20 4,275 0 4,275 3,500 36 11,255 6965.94 4,855 0 4,855 6,400 42 18,875 6968.65 5,655 5,875 11,530 7,345 48 35,045 6970.99 6,280 20,990 27,270 7,775 54 47,760 6971.90 6,505 28,370 34,875 12,885 60 47,540 6971.89 6,505 28,285 34,790 12,750 66 43,340 6971.59 6,430 25,775 32,205 11,135 72 38,725 6971.26 6,350 23,100 29,450 9,275 78 34,695 6970.94 6,265 20,605 26,870 7,825 84 31,900 6970.58 6,175 17,915 24,090 7,810 90 28,895 6970.19 6,070 15,145 21,215 7,680 96 26,055 6969.80 5,970 12,530 18,500 7,555

102 23,465 6969.41 5,865 10,090 15,955 7,510 108 21,095 6969.05 5,765 8,000 13,765 7,330 114 19,245 6968.72 5,675 6,230 11,905 7,340 120 17,560 6968.41 5,590 4,710 10,300 7,260 126 16,025 6968.12 5,505 3,420 8,925 7,100 132 14,865 6967.85 5,430 2,350 7,780 7,085 138 13,950 6967.59 5,355 1,455 6,810 7,140 142 13,075 6967.33 5,280 715 5,995 7,080 148 12,250 6967.09 5,205 210 5,415 6,835 154 11,845 6966.86 5,135 0 5,135 6,710 160 11,685 6966.61 5,060 0 5,060 6,625 166 11,510 6966.34 4,980 0 4,980 6,530 172 11,320 6966.04 4,885 0 4,885 6,435 178 11,115 6965.72 4,785 0 4,785 6,330 184 10,895 6965.38 4,675 0 4,675 6,220 190 10,665 6965.02 4,555 0 4,555 6,110 196 9,115 6964.57 4,405 0 4,405 4,710 202 7,540 6964.14 4,260 0 4,260 3,280 208 6,905 6963.78 4,130 0 4,130 2,775 214 6,635 6963.36 3,975 0 3,975 2,660 220 6,175 6962.89 3,800 0 3,800 2,375 226 5,290 6962.45 2,330 0 2,330 2,960 232 4,530 6962.07 2,130 0 2,130 2,400 238 4,180 6961.72 1,950 0 1,950 2,230 244 3,935 6961.38 1,780 0 1,780 2,155 250 3,705 6961.07 1,635 0 1,635 2,070 258 3,490 6960.75 1,485 0 1,485 2,005 264 3,290 6960.45 1,350 0 1,350 1,940

(1) Includes auxiliary spillway, outlet works, and flow over main dam

4-27

TABLE 4.16

Wheatland Reservoir No. 2 Full PMF - No Dam Failure




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

6 6,855 6963.70 4,100 0 4,100 2,755 12 6,760 6963.55 4,045 0 4,045 2,715 18 6,840 6963.67 4,090 0 4,090 2,750 24 9,000 6964.54 4,395 0 4,395 4,605 30 11,560 6966.42 5,000 0 5,000 6,560 36 26,190 6969.82 5,975 12,660 18,635 7,555 42 97,290 6973.11 6,800 39,270 46,070 51,220 48 126,660 6973.64 6,925 44,400 51,325 75,335 54 112,040 6973.38 6,865 41,860 48,725 63,315 60 92,765 6973.03 6,780 38,510 45,290 47,475 66 80,060 6972.73 6,710 35,720 42,430 37,630 72 70,340 6972.50 6,655 33,625 40,280 30,060 78 62,000 6972.31 6,605 31,930 38,535 23,465 84 54,320 6972.12 6,560 30,265 36,825 17,495 90 48,565 6971.96 6,520 28,880 35,400 13,165 96 44,855 6971.70 6,455 26,685 33,140 11,715

102 40,500 6971.38 6,375 24,060 30,435 10,065 108 36,410 6971.09 6,305 21,765 28,070 8,340 114 33,590 6970.80 6,230 19,545 25,775 7,815 120 31,105 6970.48 6,145 17,190 23,335 7,770 126 28,660 6970.16 6,065 14,935 21,000 7,660 132 26,475 6969.86 5,985 12,920 18,905 7,570 138 24,570 6969.57 5,905 11,070 16,975 7,595 142 22,825 6969.31 5,835 9,495 15,330 7,495 148 21,240 6969.08 5,775 8,170 13,945 7,295 154 19,970 6968.86 5,715 6,965 12,680 7,290 160 18,810 6968.64 5,650 5,825 11,475 7,335 166 17,670 6968.43 5,595 4,800 10,395 7,275 172 16,600 6968.23 5,535 3,890 9,425 7,175 178 15,600 6968.04 5,485 3,090 8,575 7,025 184 14,875 6967.85 5,430 2,350 7,780 7,095 190 14,135 6967.64 5,365 2,315 7,680 6,455 196 12,835 6967.26 5,255 550 5,805 7,030 202 11,790 6966.78 5,110 0 5,110 6,680 208 11,480 6966.30 4,965 0 4,965 6,515 214 11,070 6965.65 4,760 0 4,760 6,310 220 10,205 6964.88 4,505 0 4,505 5,700 226 7,765 6964.20 4,275 0 4,275 3,490 232 6,840 6963.68 4,090 0 4,090 2,750 238 6,530 6963.20 3,915 0 3,915 2,615 244 5,850 6962.73 3,740 0 3,740 2,110 250 5,010 6962.31 2,255 0 2,255 2,755 258 4,350 6961.95 2,065 0 2,065 2,285 264 4,095 6961.60 1,890 0 1,890 2,205

(1) Includes auxiliary spillway, outlet works, and flow over main dam

4-28

As noted in the previous scenario, the main embankment is capable of passing an event of somewhat less than the 50% PMF event. This being the case, the failure scenario includes failure by overtopping for the 100% PMF and by piping for the 25% and 50% PMF' s. Similarly to the previous scenario, the reservoir routing (including failure) outflows were segregated by location, and input into HEC-l for the downstream routing analysis.

Again, the downs tream routing results of this scenario and the other two scenarios are summarized in Table 4.7, 4.8, and 4.9 for the 25% PMF, the 50% PMF, and the Full PMF, respectively. Cross-section plots with flood levels are in Appendix A.

4.5 RESULTS OF THE ROUTING STUDIES

As indicated above, Wheatland Reservoir No. 2 is capable of passing an event of somewhat less than the 50% PMF without the main embankment overtopping. The main spillway embankment would overtop at a storm less than the 25% PMF. However, it is believed that overtopping of the main spillway embankment would not result in a catastrophic release of water from Wheatland Reservoir No.2. The main spillway embankment for the most part is no more than three feet high, or stated otherwise, the natural ground level at the main spillway embankment is approximately at the normal high water line (elevation 6964). The ground slope from the main spillway area towards the reservoir is very shallow, and an extremely large volume of material would have to be eroded away before any significant depth of cutting would occur. If any loss of active storage occurred in this area as a result of the overtopping and the resulting erosion, the development of the "breach" and storage loss would be slow compared to the sudden loss of storage that would be expected if the main embankment overtopped and failed.

The downstream routing of the various floods and scenarios produced unique and unexpected results. For the three extreme flood events analyzed, the fact of having Wheatland Reservoir No. 2 in place reduces the downstream flood level when compared to the baseline condition of no dam in place. That result would be expected with the no failure scenarios, but that also held true for the dam failure scenarios under all the flood events. Tables 4.7, 4.8, and 4.9 all illustrate this result. The table also show that for the 50% and Full PMF there is very little difference in the flood routing results between any of the scenarios. As the floods decrease, the benefit of reduced downstream flows as a result of Wheatland Reservoir No. 2 increases. The flood routing cross-sections provided in Appendix A also illustrate these points.

The benefit provided by the reservoir is due largely to the distance separating the two spillways. As discussed previously, prior to the reservoir being constructed, all flows would have continued past the darn site with no discharge through the main spillway area. With the darn in place, discharges would occur simultaneously at both spillways and both spillways would peak at the same time. Flows being discharged by the

4-29

auxiliary spillway must travel approximately 11.5 river miles before reaching the confluence of the main spillway discharge. By the time the peak from the auxiliary spillway travels this distance, the peak from the main spillway has already passed. This shifting of peaks results in a overall lowering of the total peak.

The darn failure analysis did not show any increase in flows as a result of the darn failure. A large part of the reason was discussed above. Another factor is that although the storage volume is large, the height of darn for this storage is small. The rate of failure and any peak increase in discharge as a result of the darn failure is affected more by the height of the darn, rather than by the storage volume. The size of the incoming flood also affects the incremental change - if the inflow volume and peak is large, the darn failure becomes a "drop in the bucket". This is evidenced by looking at the Full PMF with no darn in place - the flow depth just below the Wheatland Reservoir No. 2 darn site would be 23 feet, or twothirds the height of the darn.

The results of the downstream routings have been plotted on USGS quad maps and are on file at Banner Associates, Inc. office. The flood inundation mapping does not shown any difference between the different scenarios of the same flood. Additionally, very little difference occurs between the 25% PMF and the Full PMF. This is largely due to the fact that the Laramie River downstream towards 1-25 is either confined in steep rocky canyons, or has a wide flat meadow bottom that rises abruptly on either side of the meadow. The result is that the meadow bottoms, where most dwellings and structures are found, will get flooded whether the flood event is a 25% PMF or 100% PMF.

The overall result of the flood routings between Wheatland Reservoir No. 2 and 1-25 North of Wheatland is that from a downstream flooding standpoint, no benefit is gained by increasing the spillway capacities to pass a PMF when compared against letting the dam overtop and fail during this extreme flood event. This would not be desirable from an irrigation standpoint, but would not result in increased flooding downstream. No conclusions are drawn in this report as to the flood routing results downstream of 1-25 as this was outside the scope of this study. Wheatland Reservoir No. 2 can currently pass approximately a 50% PMF without the main embankment overtopping. Erosion would be expected to occur to the main spillway embankment as it is overtopped with floods less than the 25% PMF, with the possibility of some loss of active storage. However, this would not result in the loss of the entire reservoir contents. The 25% PMF is still an extreme flood event, however in order to protect against any loss of active storage, the main spillway embankment could be "armored" (concrete cap, riprap, etc.) to withstand overtopping.

4-30

5.0 ECONOMIC ANALYSIS

5.0 ECONOMIC ANALYSIS

5.1 INTRODUCTION

This Phase I study was intended to include an incremental flood damage analysis for the various PMF events described in the previous section. The hydrological analyses undertaken for this study show that for all levels of a probable maximum flood (25%, 50%, and Full PMF) , there would be no appreciable difference in damages to existing structures and agricultural lands in the floodplain. For this reason, the incremental damage analysis focused on inventorying and estimating the value of all structures, machinery, livestock, and crops in the floodplain so that the information would be available for future planning efforts. All of this property would potentially be at risk from a flood in the range of the 25% PMF to the full PMF, regardless of whether Wheatland Reservoir No. 2 was in existence or not.

5.2 METHODOLOGY

Data for the floodplain inventory were compiled from three sources. First, a preliminary inventory of structures and agricultural land in the floodplain was developed from topographic maps and aerial photographs. Second, a field inspection was conducted to confirm and supplement the preliminary inventory. Finally, allIS ranches and farms identified in the floodplain were contacted, and a property value survey was completed for 12 of them. A list of the 15 ranches, along with their respective locations, is contained in Table 5.1. A corresponding map of the location of these ranches is shown on Figure 5-1.

Since the economic costs of a flood can vary by the time of year, estimates of potential damages in the floodplain were based upon a worstcase scenario; i.e., a flood in the fall, when livestock and harvested hay crops are more at risk. To estimate the economic value of structures, crops, livestock and machinery, average value factors were applied to the various items inventoried. The factors used to value residences, personal property, farm buildings, corrals, fences, crops, and livestock are shown in Table 5.2. For example, native hay crops were valued at $82 per acre, an amount reflecting average yields in Platte County and a five-year average price for hay in Wyoming. Other crop prices were derived in a similar fashion.

Residences in the floodplain were valued at $36.00 per square foot, reflecting a depreciated value of 80 percent of the estimated replacement cost of $45.00 per square foot. Farm buildings were assigned a depreciated value of 50 percent of their estimated replacement cost. Since most of the residences and farm buildings in the floodplain are relatively old, these depreciated values more accurately reflect potential economic losses than replacement costs would.

5-1

TABLE 5.1

Name and Location of Ranches in the Floodplain

Ranch No. Name Location

1 Dodge Ranch R73W, T23N, S34

2 Rich Edwards, Outfitter R71W, T23N, S 2

3 Bookout Ranch R71W, T23N, S 1

4 Dr. Wood's Ranch R70W, T24N, S34

5 Phil Rietz Ranch R70W, T24N, S36

6 Clayton Rietz Ranch R70W, T24N, S24

7 Kittell Ranch R69W, T24N, S19

8 Pait Ranch R69W, T24N, S10

9 Prosser Ranch R69W, T24N, SlO

10 Wilkinson Ranch R69W, T25N, S25

11 J.C. Galligar Ranch R69W, T25N, S35

12 Bud Wilson Ranch R69W, T25N, S35

13 Jones Ranch R69W, T25N, S25

14 Wilson Ranch R68W, T25N, S30

15 McGuire Ranch R68W, T25N, S2l

5-2

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Category

Residences

Mobile Homes

Personal Property

Wooden Farm Buildings

til Metal Farm Buildings I ~

Stone Farm Buildings

Corrals

Field Fences

Crops: Native Hay Alfalfa Corn

Pasture Restoration Crop Retoration

Livestock: Cattle Horses

TABLE 5.2

Property Valuation

Unit Factor

Value per square foot $ 36.00


Percentage of residence value 50%

Value pe~ square foot $ 4.00



Value per running foot $ 2.00

Value per mile $2,144.00

Value per acre $ 82.00 Value per acre $ 194.00 Value per acre $ 241.00

Value per acre $ 25.00 Value per acre $ 120.00

Value per head $ 550.00 Value per head $ 600.00

Factors

Source

Average of Albany County contractors' estimates, depreciated to 80%.

Average of Albany County contractors' estimates, depreciated to 80%.

Standard method of valuation in the insurance industry.

Albany County contractors' average estimate depreciated 50%.

Albany County contractors' average estimate depreciated 50%.

Based on cost of labor and depreciated 50%.

Based on cost of materials.

Based on cost of materials and labor.

Wyoming Agricultural Statistics. 1987-88, compiled by Wyoming Agricultural Statistics Service, Cheyenne, Wyoming.

Western Research Corporation, 1989.

Wyoming Agricultural Statistics, 1987-88, compiled by Wyoming Agricultural Statistics Service, Cheyenne, Wyoming.

Damage to other infrastructure in the study areas was also considered. A physical inspection was made at dams, bridges, roads and utility installations in the floodplain. Information supplies by engineers, state and county personnel, and telephone and rural electric association officials was used to estimate the value of these infrastructure items.

5.3 RESULTS

The results of the property value inventory are tabulated in Tables 5.3 and 5.4. Table 5.3 shows that the estimated value of all damageable ranch property in the floodplain is approximately $8.4 million. The cos t of replanting crops and restoring fields and pastures due to a PMF event is estimated to be about $900,000.

The value of other infrastructure in the floodplain is estimated to be $2.7 million as shown in Table 5.4. The principal items at risk are the dams below the Wheatland Tunnel, valued at $911,000; roads, valued at $690,000; and utility installations, valued at $830,000.

In addition to the value of ranch property and infrastructure in the floodplain, another type of economic loss would accrue from a flood in the range of 25% to the Full PMF. The hydrological studies described earlier indicate that a flood of this magnitude would cause overtopping of the main spillway embankment of the reservoir, and subsequent erosion may cause portions of storage capacity in the reservoir to be lost. While the embankment could be repaired in a relatively straightforward fashion, the flood event could result in the loss of up to 30,000 acre-feet of irrigation water that would otherwise be utilized by the Wheatland Irrigation District. Also, Wyoming Water Development Commission Grant/Loan Funds may not be available for reconstruction following a future flood event.

Previous studies have shown that irrigation water applied to crops in eastern Wyoming can be valued at approximately $26 per acre - foot (WRC, 1986). Applying this value to the estimated 30,000 acre-foot water loss described above means that a one time income loss to farmers in the Wheatland Irrigation District of up to $780,000 could occur in the event of a severe flood.

The estimated value of all potential losses due to a 25% to the Full PMF event above Wheatland Reservoir No. 2 is approximately $12 million. Approximately $8.4 million of this total represents potential damage to ranch property, approximately $2.7 million represents potential damage to infrastructure in the floodplain, and about $800,000 represents possible income losses if irrigation water is lost to the Wheatland Irrigation District. In addition to these property losses, there are between 30 and 40 people living in residences located in the floodplain, depending upon the time of year. Without adequate warning, the lives of these residents could be at risk in the event of a severe flood.

5-5

TABLE 5.3

Inventory of Ranch Property in the Floodplain

Category

Residences(l)

Personal Property

Farm Buildings(2)

Corrals

Field Fences

Crops

Field Restoration

Livestock

Farm Equipment

Vehicles

Irrigation Systems

Total Estimated Value

Estimated Value

$1,479,132

739,566

344,854

102,480

534,981

578,357

893,914

2,681,728

578,788

235,200

191,335

$8,360,335

1. Residences were depreciated to 80% of their estimated replacement cost of $45.00 per square foot.

2. Farm buildings were depreciated to 50% of their estimated replacement cost.

5-6

TABLE 5.4

Value of Infrastructure in the Floodplain

Category

Two Diversion Dams

Bridges (4)

Gauging Stations (4)

Unimproved Roads (15 miles)

Asphalt Roads (3 miles)

Telephone Lines (20-30 miles)

Electric Power Lines (20-30 miles)

Total Infrastructure

Estimated Value

$ 810,000 101,000

180,000

60,000

450,000

240,000

330,000

500.000

$2,671,000

5-7

Source

Banner Associates, 1989

Banner Associates estimated a replacement cost of $50/sq. ft.

Telephone conversation with the Albany County Water Commissioner, Sept., 1989.

Wyoming Highway Department estimates.

Estimate provided by the Platte County Engineer.

Based on replacement cable at $2.50 per running foot.

Estimate provided by Chuck Witte, Wheatland Rural Electric Association.

5.4 CONCLUSIONS

The results of the incremental damage assessment described in this section indicate that property losses resulting from a flood of a magnitude in the range of 25% to the Full PMF would be approximately $12 million. The lives of 30 to 40 residents of the floodplain also would be at risk. This conclusion applies regardless of whether Wheatland Reservoir No. 2 is capable of passing the full PMF; there appears to be no significant difference in damages or risk to human life regardless of whether improvements are made to the Wheatland Reservoir No. 2 facilities. In actuality, the simple fact that Wheatland Reservoir No. 2 exists has the effect of attenuating the flood peak compared to the without reservoir scenario. In effect, the reservoir serves as a large detention pond to attenuate peak flows.

One potential economic rationale for improvements to Wheatland Reservoir No. 2 involves avoiding the potential loss of approximately 30,000 acrefeet of irrigation water in the event of a 25% to the full PMF occurrence. Given the extremely low probability of such a flood event, however, such improvements could not be justified on a strict benefit-cost basis. Other reservoir improvements may be justified based upon operational safety criteria, which are discussed elsewhere in this report.

5-8


An analysis of the historic reservoir storage records was performed to determine the feasibility of maintaining a minimum pool level of 15% to 20% of the total reservoir capacity. Specific sources of the historic records (by water years) were as follows: 1) 1936 through 1951 were obtained from the Wheatland Irrigation District; 2) 1952 through 1966 were obtained from USGS Water-Supply Papers; and 3) 1967 through 1989 were obtained from the Water Division No. 1 Annual Hydrographer's Reports. No records were found prior to 1936, and only records during the irrigation season were available from 1936 to 1942. Also, no records were available for water years 1949, 1950, and the non-irrigation months of water year 1951. Some gaps of data also existed for several years during the non- irrigation season. The historic end-of-month storage volumes are presented in Table 6.1 and illustrated in Figure 6-1. Gaps in the data were estimated by evaluating the known storage levels on either side of the gap in conjunction with evaluating the reservoir inflow gaging station records. Therefore, the total period analyzed for this report was from May 1936 through September 1989.

The reservoir capacity at normal high water is 98,934 acre-feet. From examination of the elevation-capacity table and the early reservoir contour map, it appears this volume reflects active storage only. The early reservoir contour map shows approximately 3,383 acre-feet below the outlet works intake level, which would indicate a total capacity of 102,317 acrefeet. The records discussed above are based on active storage. Since the records reflect active storage and also due to the fact that dead pool volumes have not recently been verified, this analysis presents results based on both the active storage and the total storage.

Typically, guidelines for maintaining a conservation pool for recreation and fisheries would be that the pool would not be encroached upon more than 2 out of 10 years on the average, or 20% of the years. The first approach taken was to count the number of years when sometime during that water year the storage dropped below the 15% or 20% levels. For the active capacity, that corresponds to 14,840 acre-feet and 19,787 acre-feet, respectively. The records indicate that in 27 out of 54 years the storage dropped below the 15% level at some time during the year. Similarly, the storage dropped below the 20% level 33 out of the 54 years. Very little change results from using the total storage versus the active storage. The 15% and 20% levels of total storage correspond to 11,965 active acre- feet and 17,080 active acre- feet, respectively. The 15% level comparison is the same as for the active storage; at the 20% level, 32 out of the 54 years drop below the target storage.

Another approach taken was to compare the total amount of time (based on months) that the storage contents were below the 15% and the 20% levels. Typically, the years in which the storage fell below the target levels, the storage dropped below in August and remained below through March of the following year. Based on the active capacity, the reservoir was below the 15% level 21.4% of the time, and was below the 20% level 27.0% of the time.

6-1

TABLE 6.1 WHEATLAND RESERVOIR NO. 2

End-of-month active storage (Ac-Ft)

Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sept

1936 19300 24100 11800 4700 1900 1937 3000 # # # * * + 23900 38800 32900 18200 8300 Normal Active Capacity = 1938 # # * * + + + 32400 57400 62500 38200 26000 98,934 ac-ft 1939 + + + + + + 43800 47100 36900 1nOO 6700 3060 1940 # # # # # 6000 8800 8400 8200 4800 2100 2000 1941 # # # 6800 9700 11400 14400 14000 16000 12500 5700 3200 May 1936 through Sept 1988 1942 2200 5800 8400 11000 11800 14500 21100 72100 70800 40800 21700 18000 1943 20100 20100 24100 25800 27000 33800 43100 61200 77200 71600 44700 24600 1944 21300 21400 22300 23100 23800 25300 31400 34800 26300 16700 8100 2800 Total period = 641 months 1945 1100 2100 3000 3100 8000 9300 16900 26900 45500 55700 45000 37800 1946 34000 34600 + 36600 42600 44300 51600 53300 54100 37500 19400 9900 1947 8000 11200 # * 16700 20200 25700 43800 78700 88000 70300 52400 15% Normal Capacity = 1948 49160 52330 + 56500 60900 63500 77300 88100 82400 61000 41600 27000 14,840 ac-ft 1949 + + + + + + + + + + + + 137 months below 15% 1950 + + + + + + + + + + + + = 21.37% of period 1951 + + + + + + + + 80300 85600 65400 51800 1952 46600 48600 52020 52510 53970 59760 76920 92320 87840 57970 36370 24540 20% Normal Capacity = 1953 23220 23300 23510 25640 28300 33690 35800 35600 27150 10900 3270 934 19,790 ac-ft 1954 2600 4040 6500 7780 10210 11650 12130 12020 10780 970 240 0 173 months be l ow 20% 1955 0 0 0 0 I 768 1360 3530 3730 1910 1680 768 768 = 26.99% of period 1956 1710 2370 3450 5110 6120 7900 12580 14600 7500 2330 1140 0 1957 0 500 1100 1700 4090 9350 16170 19990 80590 93410 71280 65800 Total Capacity = 1958 66860 70230 72340 73470 75880 80890 81800 81670 75650 48480 25630 20410 98934 + 3383 = 102,317 ac-f

0'\ 1959 20000 20680 22360 23620 25080 29200 36940 41350 47450 31930 16170 9230 I 1960 12000 16180 17140 18570 20250 26800 29820 29680 37670 19800 8070 5740 15% Total Capacity =

N 1961 6240 10190 11100 11500 12000 13690 17280 20810 56860 39980 25080 22900 11,965 active ac-ft 1962 30230 37340 41800 45860 54980 62820 68580 78680 94270 79870 52220 42060 112 months below 15% 1963 43270 44460 45590 45600 48880 54320 56970 50000 48200 30680 16940 8290 = 17.47% of period 1964 13440 13920 13990 14740 15440 17010 24480 25410 31400 20680 5260 6980 1965 7250 n60 8460 9270 10040 11740 15630 21650 73812 67931 49319 49350 20% Total Capacity = 1966 61000 67900 71900 74800 77400 82700 83470 69570 59500 34104 12667 9240 17,080 active ac-ft 1967 # # # # # # * 16000 48710 61890 37538 26146 159 months below 15% 1968 + + + + + 41338 52843 55118 96455 74496 54560 44282 = 24.80% of period 1969 44033 44033 + 51100 54350 58071 64400 62084 81307 64660 32116 16900 1970 19230 23100 24300 + + + 48195 55757 94011 83126 62084 50376 1971 + + + 68800 '73400 81911 82639 70780 94536 85215 56859 50570 1972 54000 57100 59800 61980 65240 71895 73288 74320 91410 64070 41453 35200 1973 38300 42600 45200 47490 49700 53213 78090 87710 90060 84040 66420 61820 1974 59500 + + + + 77500 67700 67000 93800 71700 48500 39000 1975 42500 46400 48800 50200 52900 58700 65800 57200 84500 76900 52400 39300 1976 40700 44200 48300 50400 54200 60700 66100 64800 63600 50100 37600 27100 1977 27700 29700 31000 31500 32500 36000 39200 38300 35600 22000 9740 8140 1978 9830 11500 12600 14300 16400 22800 25400 30200 72900 72000 51700 36400 1979 36600 39200 41100 42500 44000 51900 66900 70400 88800 69600 51400 37100 1980 37600 41400 45200 49300 52600 59900 81900 71400 84000 64900 44300 36600 1981 37200 39700 43500 45900 47600 50200 50700 53000 48300 33300 17600 15600 1982 16600 18400 20900 21800 24200 29900 31400 27900 66600 80400 61100 54400 1983 57800 62000 63400 62900 64500 74400 69200 65100 86800 89700 75000 55100 1984 57500 61900 66100 70500 74200 75700 87300 86600 91100 91000 88800 80300 1985 78400 74400 72000 71400 73000 82300 86200 86000 86400 68100 50700 41600 1986 47500 52400 56900 60500 68500 79400 81700 81100 92900 86400 62300 54800 1987 61900 68900 69200 68100 69700 73400 78900 75200 65700 48800 24500 17600 1988 15700 18300 20500 21000 22200 28700 47500 58000 82200 67100 44500 35000 1989 34400 36000 38000 39300 41600 51900 55300 52700 50300 25800 12300 11800

# Storage assumed below 14,840 ac-ft * Storage assumed below 19,790 ac-ft + Storage assumed above 19,790 ac-ft

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WHEATLAND RESERVOIR NO.2 End-of-Month Content (A F )

3638 4 () c~ :-2 44 46 48 50 52 54 56 5 E3 60 62 64 66 68 70 7 2 7 4 7 6 78 80 82 84 86 88 90

Water Year

--14,840 Ac-Ft

Based on total capacity, the reservoir was below the 15% level 17.5% of the time, and was below the 20% level 24.8% of the time.

The results indicate that neither a 15% nor 20% conservation pool could be maintained for 8 out of 10 years (based on the entire period of record) unless past operating procedures would be modified. As a note, the 15% level was only encroached upon in three years between 1968 and 1989. If the criteria is based on 80% of time (months), the 15% level would be "in the ballpark" under past operating procedures.

If a goal will be to maintain a conservation pool for 8 out of 10 years on the average, a detailed reservoir operation study should be undertaken to determine what operational changes and constraints will be necessary. Also, a reservoir operation study could indicate if the higher storage levels over the past 20 years have occurred from higher inflows or resulted from operational changes and more efficient use of Wheatland Reservoir No. 3 being used in conjunction with Wheatland Reservoir No.2.

6-4

7.0 GEOTECHNICAL ANALYSIS

7.0 GEOTECHNICAL ANALYSIS

7.1 INTRODUCTION

Wheatland Reservoir No. 2 is located in the northeast portion of the Laramie Basin, Wyoming Basin Physiographic Province. The geology in the area consists of a series of tightly folded sedimentary units unconformably overlain by Quaternary alluvial deposits. The centerline of the main dam nearly follows the axis of a syncline. The main dam crosses the Cretaceous Mowry, Thermopolis and Cloverly, Jurassic Morrison and Sundance Formations; and the Chugwater Group moving from south to north. The unconformable contact between the sedimentary rock units and the Quaternary alluvial deposits is either located near or directly under the dam. The main spillway structure is located on the quaternary alluvium. Exposures of the soil and bedrock were limited near the dam site because of a well established grass cover. Soils used to construct the dam embankment were observed as a silty sand to silty clay and silty sand with cobbles in the downstream toe drain.

The geotechnical analysis for Phase I of the Level II Feasibility Study for the Wheatland No. 2 Rehabilitation Proj ect included a review of previous studies, a site reconnaissance, a stability evaluation, field investigations, and evaluating the results.

7.2 REVIEW OF PREVIOUS STUDIES

The reports and letters reviewed included:

- Phase I Inspection report National Dam Safety Program, Wheatland No. 2 Dam prepared for the Corps of Engineers (COE) dated September 18, 1979.

- Wheatland Irrigation District Report, Water Division No.1, Platte County, Wyoming, October 1988, by the Soil Conservation Service.

- Report of a Geotechnical Investigation for an Existing Dam, Wheatland Reservoir No. 2 prepared by RBD, Inc. dated January 4, 1985.

Report on Conditions of Wheatland reservoir No.2, Permit No. 1724 prepared by Russell Dahlgren (Assistant Safety of Dams Engineer) dated December 24, 1987.

These reports presented several conclusions and recommendations and the significant findings with respect to the geotechnical evaluation are:

1. Seepage measurement and inspection, and maintenance of the upstream face was recommended by the COE. In addition, observations of the dam were to be conducted by a qualified soils engineer during high pool conditions.

7-1

2. Rodent holes in the dam embankment may cause a long-term stability problem and were to be repaired as a maintenance item.

3. A lack of plans such as an Emergency Action Plan, a Standard Operating Procedures Plan/Maintenance Schedules, and an Inspection Program was noted. The COE recommended periodic inspections of the dam, the outlets, and main spillway.

7.3 SITE RECONNAISSANCE

A geotechnical site reconnaissance of the Wheatland No. 2 Dam site was performed on July 20 and 21, 1989 by personnel from Woodward-Clyde Consultants, Banner Associates, Inc., Wyoming State Engineer's Office, Wyoming Water Development Commission, and the Wheatland Irrigation District; to observe site conditions, seepage, potential spillway locations, and existing dam conditions as part of the scope of services. The on-site reconnaissance consisted of observing the water level conditions and the condition of the upstream and downstream slope and crest of the dam. The reservoir water level was at the approximate elevation of 6945 at the time of the site reconnaissance which is near historic low reservoir levels.

The reconnaissance was conducted by walking and methodically recording the condition of the dam at about 200 feet stations. The locations noted below from the site reconnaissance are paced distances, starting from the fence gate at the north end of the dam (We have estimated the stations assuming the fence gate is at station 74+26 from the survey data). The embankment, in general, appeared to be in good condition. We did not observe signs of cracking on the crest or slopes of the dam. Our observations generally showed the following conditions:

- Crest widths averaged about 24 feet and ranged up to about 36 feet near the caretaker's house. The crest level was slightly depressed along a short reach of the dam near the outlet works. A typical dam embankment cross section is shown on Figure 7-1.

Riprap on the upstream face varied in thickness from 0 feet to 8 feet, with some recent riprap placed for maintenance.

- Significant rodent activity was noted on the downstream face of the dam.

- Two areas of erosion/shallow sloughing of the downstream slope.

- Slopes of the dam ranged from generally 2:1 to 2.5:1 for the downstream slope and ranged from 1.5:1 to 2:1 for the upstream slope. Below the normal water level, the upstream embankment slope flattened to about 4:1 or flatter.

7-2

VAR I ES

EX 1ST I N G G R 0 U N D

L

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APPROXIMATE BERM ELEVATION 6954 (VARIES)

BANNER BANNER ASSOCIATES. INC. • CONSULTING ENGINEERS 8. ARCHITECTS 620 PLAZA COURT. P.O.BOX 550 - LARAMIE. WY B2070 • (3071745-7366

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(23' TO 30')

APPROX. ct

TOP OF EMBANKMENT (ROAD)

OF EMBANKMENT

WHEATLAND RESERVOIR NO.2 (AP P R OXI MATE WATER ELEVATION 6945 AT THE TIME OF THE SITE RECONNAISSANCE)

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APPROXIMATE CREST ELEVATION 6971.5 (VARIES)

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7-3

TYPICAL CROSS SECTION DAM EMBANKMENT

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7-1

- Several piezometers were noted on the dam.

- The outlet for Irrigation Outlet No. 2 through the dam could not be located.

- Discharge from the toe drains in general could not be measured.

- Areas of heavy, lush vegetation of types indicating shallow ground water conditions and underseepage were noted downstream of the dam, primarily on the south one-half.

The crest of the dam was generally about 24 feet wide, and ranged from 24 feet to 36 feet. We noted a depressed area between about Station 43+26 and Station 44+26 left of the outlet works section, approximately 6 inches to 1 foot deep. This area is close to the access ramp leading to the downstream face. There were no obvious slope movements in this area and we postulate that this may be related to ramp construction rather than settlement.

Observations along the upstream face of the dam showed riprap of varying quantity and quality. The riprap was variable in terms of angularity and rock hardness. Areas of thinner riprap were noted between of the right end of the dam and about Station 74+26, between about Station 70+26 and Station 72+26, and between about Station 64+26 and Station 66+26. Recently placed riprap was observed in the upper 8 to 10 feet on the upstream face of the dam between about Station 15+62 and Station 52+26 which generally consisted of gravel, cobbles, and boulders up to 2 feet in diameter, intermixed with sandy clays and clayey sands. The majority of the materials are less than 1 foot in size. The riprap placed appeared to widen the crest by about 7 to 8 feet, to the present average width of about 24 feet. We also noted signs of undermining the loosely placed riprap by wave action or runoff in several areas. The overly steep upstream slope of dumped riprap will likely be unstable when the reservoir level rises. Between the auxiliary spillway and about station 52+26, the riprap is sparse in the upper 6 to 8 feet. We also noted an erosion scarp about 8 feet high and 35 yards long near the left end of the dam, in an area lacking riprap to the left of the auxiliary spillway.

The downstream slope and toe area of the dam was easily visible through the sagebrush, grass and weeds vegetating the slope. The downstream face of the dam in general did not show signs of cracking or seepage, however significant rodent activity was noted starting near the auxiliary spillway to about Station 62+26. In general there was minimal rodent activity below the bench level on the downstream slope. A depression about 4 feet in diameter and 1 to 1.5 feet deep downstream of the toe of the dam was noted at about Station 51+66. This area is apparently over the toe drain. We also noted some minor slope movement in the downstream face of the dam near Station 27+36. The movement appears to be near surface erosion or shallow (a few feet deep) movement and is likely not serious. There is also a similar feature near about Station 28+26; this feature is near the Irrigation Outlet No. 1 and is about 60 feet long. The upper portion of the movement is about 12 to 15 feet above the berm and appears to be aggravated by erosion.

7-4

During our reconnaissance, we located piezometers near Station 18+11 and Station 64+56 on the downstream bench. We were unable to remove the caps. We also encountered two apparent drill holes from the 1984 investigation, at about Station 42+01 and Station 58+86, along the crest of the dam.

There are three irrigation pipes apparently passing through Wheatland No. 2 dam. Irrigation Outlet No. 1 was discharging to the canal at the time of our visit. We could not observe the outlet of the pipe due to discharge for irrigation demands. Inlet and control valves were noted for two other irrigation canals located near the fence gate at the north end of the dam and at about Station 13+09. However, the outlet to Irrigation Outlet No.2 could not be located.

We observed three toe drain outlets along the downstream toe of the dam. One outlet at about Station 29+16, in the south half of the dam showed a minor discharge estimated at 1/4 to 1/2 gallon per minute. The Phase I National Dam Safety Program Report indicated that a considerable amount of seepage exits through this drain pipe during the spring when reservoir levels are higher. A second outlet (10-inch diameter tile) was noted in a concrete box located about Station 43+96, right of the main outlet pipes. An occasional drip of water discharged from this pipe at the time of our reconnaissance. Details of the piping/drains were not available in the records that we reviewed. The third drain outlet is associated with drain systems for the north half of the dam. This toe drain was installed beneath the downstream buttress according to SCS drawings, dated October 1973. The drain flows downstream of the dam to a manhole located westnorthwest of the dam caretaker's house and then to the river channel, downstream of the main outlets. The drain discharge was estimated at about 15 to 20 gallons per minute on July 21, 1989.

We saw no active seepage at the downstream toe of the dam during our reconnaissance. However, the reservoir was very low and it is possible that active seepage occurs when the reservoir is at higher levels. Areas of heavy, lush vegetation and cattails (indicative of shallow ground water conditions and seepage areas) were noted near the toe of the buttress and in the downstream areas at about Station 56+26 and between about Station 22+26 and Station 34+26. We also noted ponded water at the downstream toe of the berm between about Station 39+46 and Station 40+86. In addition, the irrigation ditch near Station 15+46, approximately 8 feet lower in elevation had standing water, but no flow was observed.

7.4 STABILITY EVALUATION

A stability analysis was performed by RBD Inc. for the Wheatland Dam No.2; results were reported in a letter dated January 4, 1985. We have reviewed the stability analysis including the assumed soil parameters, strength test results, and standard penetration test results from the field investigation, and summary logs and water levels obtained in the field investigation program.

7-5

The embankment generally consists of a sandy, silty, clay with some gravel. Standard penetration tests indicated an average blow count for the embankment of about 7, and laboratory test results indicated an average dry unit weight of about 108 pounds per cubic foot (pcf).

The upper portion of the foundation generally consists of a silty clay with an average blow count of about 15 and an average dry unit weight of about 109 pcf, based on data contained in the report. A sand and gravel layer was encountered below the silty clay layer. The blow counts averaged 29 and the average dry density was about 106 pcf. A very dense claystone or sandstone bedrock underlies the sand and gravel material.

The cross section assumed for the slope stability analysis by RBD, Inc. appeared to be for the maximum section of the embankment. The assumed cross section is shown on Figure 7-2 (excerpted from the RBD report), and consisted of embankment fill, underlain by a silty clay layer and then a sand and gravel layer, overlying bedrock. Soil parameters assumed for the analysis by RBD, Inc. are also shown on Figure 7-2. RBD, Inc. reported a minimum Factor of Safety of 2.15, using the Modified Bishop method of analysis, for a circular arc passing either through the top of the sand and gravel foundation layer, or the bottom of the silty clay foundation layer. It appears from Figure 7-2 of the RBD cross-section that the soil parameters used by RBD, Inc. consisted of both total and effective stress parameters. The bar (-) used over the angle of internal friction values of 11°, is normally used to denote an effective stress parameter. However, a friction angle of 10° is shown on Figure B-24 of the RBD report, as a total stress parameter. In addition, the other properties of the materials used in the triaxial strength tests were not noted, making it difficult to check the strength parameters developed. The soil parameters used by RBD, Inc. and the basis for selecting them are therefore somewhat difficult to discern.

We reviewed the laboratory test results, field drill logs and blow counts from the field investigation in comparison with our interpretation of the assumed soil parameters. We performed stability analysis for three cases utilizing a "hand check" analysis assuming total stress conditions (Case I) and effective stress conditions (Cases II and III). The Ordinary Method of slices was used for our hand check analysis assuming the failure surface reported by RBD, Inc. We did not perform a search for other failure surfaces. The Ordinary Method of Slices generally is more conservative than the Modified Bishop Method of Analysis. Results of the stability analyses and assumptions made for each of the three cases are as follows.

The total stress analysis (Case I) assumes the embankment and foundation is normally consolidated, and undrained. If the consolidated, undrained condition represents Wheatland Dam No.2, we estimate the theoretical factor of safety is about 1.5. The effective stress analysis assumes pore water pressures for steady seepage conditions, and the angle of internal friction of the soil based on consolidated, drained conditions, and cohesion. The calculated theoretical factor of safety assuming effective

7-6

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We also calculated the theoretical factor of safety assuming that the failure surface passes through Layer D, the sand and gravel layer (Case III) . Our calculated factor of safety for this case was about 1.9, and compares to the calculation by RBD, Inc. of 2.15. We cannot be sure if this matches the assumptions in the RBD report. However, we believe the failure surface for this embankment and foundation configuration would pass through Layer C (above Layer D) as assumed in our analysis for Cases I and II. The results of our analysis and assumed soil parameters are summarized below.

PARAMEnRS Theoretical Friction Factor of Soil Angle Cohesion Total Unit

CASE Safety L:iyer d (psf) Weig):1t (pcf)

I. Total Stress l.5 A 210 288 110 Analysis Failure B 110 288 115 Surface Througp C 110 288 115 L:iyer C

II. Effective Stress l.8 A 210 288 110 Analysis Failure B 210 288 115 Surface Througp C 210 288 115 layer C

III. Effective Stress l.9 A 210 288 110 Analysis Failure B 210 288 115 Surface Througp C 210 288 115 L:iyer D D 3]0 288 120

7.5 FIELD INVESTIGATIONS

Field investigations were conducted on September 19 and 22, 1989 for the purpose of assessing spillway foundation materials and excavatability, and to evaluate potential borrow materials. The investigations consisted of the excavation of eight test pits, and a site reconnaissance by a Woodward Clyde Consultants engineering geologist. The test pits were excavated using a JCB backhoe with a 3/8 cubic yard bucket provided by the Wheatland Irrigation District. The test pits were logged and selected bulk soil samples were obtained. Test pit logs are shown on Table 7.1, and test pit locations are shown on Figure 7-3.

7-8

TABLE 7.1

TEST PIT NO.1

LOCATION: 125 ft. west of crest of dam

Depth (ft.) USCS* Description Excavatabi1ity

0-7 CL CLAY, very sandy, brown to tan, moist easy

7-12 CL CLAYSTONE, sandy dark brown to black difficult

TEST PIT NO.2

LOCATION: 200 ft. west of TP-1; 25 ft. north of road

Depth (ft.)

0-4 SC

4-12 CL

Description

SAND, clayey, light brown to tan, dry

CLAYSTONE, sandy, weathered dark brown to black

TEST PIT NO.3

Excavatabi1ity

easy

easy to moderately difficult

LOCATION: 57 ft. west of fence; 52 ft. north of dike

Depth (ft.) Description Excavatabi1ity

0-3 CL CLAY, silty reddish brown, slightly moist easy

3-6.5 SC SAND, very clayey, brown and gray, easy slightly moist

6.5-9.0 GP GRAVEL, sandy, brown, iron-stained moderate

9-10.5 SP SAND, gravelly, gray to tan difficult

TEST PIT NO.4

LOCATION: 75 ft. north of TP-3; 61 ft. west of fence


0-1 ML SILT, slightly sandy reddish brown easy

1-9.5 SM-SP SAND, slightly silty, tan easy

9.5-11.5 GP-GC GRAVEL, very sandy, slightly clayey, brown difficult

* Unified soil classification system 7-9

TEST PIT NO.5

LOCATION: 125 ft. north of TP-4; 52 ft. west of fence

Depth (ft.)

0-1.5 ML

1.5-6.5 SM-SP

6.5-11.0 CL

Description

SILT, slightly sandy, reddish brown

SAND, silty, buff and black, slightly moist

Excavatabi1ity

easy

easy

CLAYSTONE, sandy, weathered, brown to gray easy

TEST PIT NO.6

LOCATION: 400 ft. west of TP-3; 20 ft. south of road

Depth (ft.) USCS Description Excavatabi1ity

0-1 ML SILT, clayey reddish brown easy

1-9.5 SP-SC SAND, clayey, buff easy

9.5-12.0 GP GRAVEL, sandy, yellow-brown cobb1y, difficult some boulders up to 16" diameter

TEST PIT NO.7

LOCATION: Highest ridge north of dam

Depth (ft.)

0-1.5 ML

1.5-5 FP-GC

5-9 SP

9-10.5 GP

Description Excavatabi1ity

SILT, slightly sandy reddish brown easy

GRAVEL, very sandy, cobb1y slightly silty easy clayey

SAND, gravelly, cobb1y, grayish white easy to moderate

GRAVEL, sandy, cobb1y yellow moderate to difficult

TEST PIT NO.8

LOCATION: 15 ft. from road - low ridge


0-3 CL CLAY, sandy, reddish brown easy

3-6.5 CL CLAYSTONE, sandy, weathered gray difficult

7-10

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WHEATLAND NO.2 DAM SITE PLAN

Test pits 1 and 2 were located in a swale downstream of the right abutment (north end) of the Wheatland No. 2 Dam. The materials encountered were about 4 to 7 feet of sandy clay and clayey sand overlying claystone bedrock to the bottom of the test pits at a depth of about 12 feet. Excavation of the overburden clay and sand was relatively easy, but excavation became moderately -difficult to difficult in the claystone bedrock to the 12 foot depth.

Test pits 3, 4, 5, and 6 were excavated in the north spillway area, downstream of the access dike and west of the existing discharge channel. Test pits 3 and 4 were located approximately 52 and 127 feet, respectively, downstream (north) of the berm. We encountered 1 to 3 feet of silty, clay overlying 3.5 to 8.5 feet of clayey sand and silty sandy and then sandy gravel and gravelly sand to the bottom of the excavations at depths of 10.5 and 11.5 feet. Excavation was generally easy in the silt and upper sand, but became difficult in the gravel and deeper sand partially due to the depth of the test pits and larger gravel sizes encountered.

Test pit 5 was located 125 feet north of test pit 4 and also encountered about 1.5 feet of silt over silty sand to a depth of about 6.5 feet. We found claystone from a depth of 6.5 feet to the bottom of the test pit at 11.0 feet. Excavation was relatively easy the full depth of the test pit. Test pit 6 was located approximately 400 feet west of test pit 3. Clayey silt about 1 foot thick was underlain by about 8 1/2 feet of clayey sand over relatively clean sandy gravel to the bottom of the test pit at a depth of 12 feet. Excavation in the silt and sand was relatively easy. Excavation in the gravel was difficult due to the depth of the pit and the presence of cobbles and small boulders up to 16 inches in diameter.

Test pits 7 and 8 were excavated on two ridges north of the main dam to assess potential borrow materials. Test pit 7 was located on the highest ridge, along the road to the north of the spillway and encountered 1.5 feet of sandy silt overlying sandy gravel and gravelly sand to the bottom of the test pit at 10.5 foot depth. Boulders could be encountered as boulders to 6 feet in length were noted in the nearby quarry, which has apparently been used for riprap. A second lower ridge was the location of test pit 8. At that location we found three feet of sandy clay over claystone bedrock.

Laboratory analyses were conducted on bulk samples obtained from test pits 1, 3, 4, and 7. Atterberg limits for four samples indicated low plasticity with liquid limit (ASTM 423-66)_ranging from 28 to 39 and plasticity index ranging from 5 to 21.

Concrete aggregate tests were performed on the sample from test pit 7 including Los Angeles (L.A.) Abrasion (ASTM C 535-81 and ASTM C 131-81), Sodium sulfate Soundness Loss (%) (ASTM C 88-876), Silica-alkali; Reactivity (ASTM C 289-81), Specific Gravity (ASTM C 127-81 and ASTM 128-79), and Absorption (ASTM C 127-81 and ASTM 128-79). The results are shown on Table 7.2. L.A. Abrasion, absorption and sodium sulfate soundness values were higher than values generally deemed acceptable for normal concrete use.

Gradation analyses of test pits TP-l, TP-3, and TP-4 are shown on Figure 7-4 and gradation analysis of test pit TP-7 is shown on Figure 7-5.

7-12

TABLE 7.2 SUMMARY OF LABORATORY TEST RESULTS

NATURAL ATTERBURG LIMITS L.A. SODIUM SllICA-NATURAL DRY LIQUID PLASTICITY ABRASION SULFATE ALKALI

HOLE DEPT MOISTURE DENSITY LIMIT INDEX WEAR SOUNDNESS REACTIVITY SPG SOIL TYPE (FEET) (X) (PCF) (X) (X) (X) LOSS (MllllMOLES) (ROCK) ABSORPTION

PER LITER

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(CL)

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(SC)

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(GP-GC)

TP-5 6.5-11.0 CLAYSTONE, weathered, very sandy, brown

(CL)

TP-7 1.5-5.0 28 5 67 2"-1 1/2" - 32.1 S =27 2.70 67 GRAVEL, very 1 1/2"-3/4 - 50.1 R =138 sandy sl ;ghtly 3/4-3/8 - 71.0 sHty, clay 3/8- #4 - 66.6 brown (GP-GC)

WOODWARD-CLYDE CONSULTANTS CONSUL.TING ENGINEERS, GEOL.OGISTS AND ENVIRONMENTAL. SCIENTISTS

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FIGURE 7- 4

WOODWARD-CLYDE CONSULTANTS CONSULTING ENGINEERS, GEOLOGISTS AND ENVIRONMENTAL SCIENTISTS

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GRADATION ANALYSIS ?IGli"RE 7- 5

7.6 RECOMMENDATIONS

Based on our site reconnaissance, review of reports and results of stability analysis, we make the following recommendations:

1. The low area of the crest, near the main outlet works, should be filled to a level consistent with the remainder of the crest and a movement monument should be established in this area for monitoring of vertical movement. The crest should be graded to drain upstream.

2. Modifications should be made to the on-going maintenance programs for the riprap on the upstream face of the dam. In our opinion, the riprap on the upper 8 to 10 feet of the dam that has been dumped at the angle of repose and contains soil sizes would not be stable under high reservoir levels. Under these conditions, the materials would probably slough and be relatively ineffective in providing erosion protection. The existing clayey, sandy gravels and cobbles and boulders should be removed or dozed down onto the bench on the upstream slope of the dam and replaced with new riprap. Also, new riprap to supplement existing riprap should be placed in areas where the riprap is thin. We recommend that the new riprap consist of rock with a minimum size of 2 inches. The maximum size rock and riprap thickness should be based on wave height calculations. The riprap should be placed in lifts using either a dozer or backhoe on a slope no steeper than 2:1 if the materials are angular and 3:1 if they are semi-angular.

3. A more intensive rodent control program is recommended along with backfilling of the existing rodent holes with compacted soil. We believe that this is important to the long term stability of the dam.

4. The hole over the drain line near Station 51+66 (north half of the dam) should be excavated and the cause of the "sinkhole" evaluated. Repairs should then be made and the area backfilled with compacted fill. In addition the drain access near Station 70+26 should be cleaned out and a new cover installed. A flow measurement system should be established and monitored for the toe drain systems.

5. The two sloughed areas in the downstream slope, on the left side of the dam above the irrigation outlets, should be excavated (probably 2 feet deep) and the excavations backfilled with compacted fill. The excavations should be observed by a qualified geotechnical engineer to confirm our opinion that the slope movement in these areas is a near surface feature.

6. We recommend that the piezometers be re-established, or newly established at about 8 study sections. Movement monuments should also be established at each study section. Monitoring of the piezometers and movements monuments should be done periodically.

7-16

The existing piezometers and/or drill holes along the crest of the darn should be cleaned out and new piezometers installed, or the holes grouted full. The piezometers in the downstream bench should be checked and incorporated into the instrumentation plan, or replaced if they are not operational.

7. The irrigation outlets near the fence gate at the north end of the darn and at about Station 13+09 should be excavated and exposed. The outlets should be refurbished and extended so that the pipes can be monitored, or the pipes should be plugged and appropriately abandoned by removal or plugging.

8. Our review of the stability analysis indicates that the Factor of Safety for the downstream slope is about 1.5 for a total stress analysis and 1.8 for an effective stress analysis using the assumed failure surface, soil parameters, and phreatic level. We recommend that piezometers be established and monitored as discussed above. A Factor of Safety of 1.5 is consistent with good engineering practice. However, we could not confirm that the strength test results presented in the RBD report, included the lower blow count material encountered in their investigation. We recommend that additional samples be obtained during piezometer installation and that strength tests be performed on the three layers. A geotechnical engineer should compare measured water levels and results of the strength tests with the stability analysis. Based on this comparison, additional stability analysis may be needed.

9. We recommend reconnaissance of the darn under full reservoir conditions to observe seepage conditions associated with the dam under more critical reservoir levels.

10. A formal operation and maintenance program and inspection program should be developed for Wheatland Reservoir Darn No.2. Monitoring of piezometers, movement monuments, and seepage rates should be included in the program.

Based on our site reconnaissance, and the test pits excavated, we make the following recommendations:

11. Clayey sands, sandy gravels and gravelly sands from the north spillway channel excavation will probably not be suitable for soil cement or roller compacted concrete for a spillway apron due to the clays in the material and/or the higher than desirable quantity of minus No. 200 sieve size materials. The silty sands could be used for soil cement if there is a sufficient quantity of non-plastic to low plasticity material. The sands and gravels from the high ridge north of the darn (TP-7) are generally suitable for RCC and would require processing (screening and washing) to remove the oversize and fines. The results from the L.A. Abrasion and absorption tests indicate higher than normal maintenance should be expected due to potential freeze-thaw deterioration if

7-17

these materials are used for aggregate. Based on the expected infrequent use of the spillway we believe wetting of the concrete will be minimal and Ree could be used for the spillway if higher than normal maintenance costs are acceptable to the District. Laboratory tests should be conducted to further develop design criteria. We recommend that structural concrete for the spillway overflow section and structure concrete be constructed using higher quality aggregate from off-site sources.

12. The excavatability of the upper materials in the test pits was generally easy. Excavation difficulty increased as the depth and gravel and cobble content increased. We observed some of the gravel and cobbles exposed in the spillway discharge channel were cemented conglomerate. Heavy ripping and possibly some blasting could be required, if these materials are encountered in the excavation. Shallow excavations for a spillway channel can likely be accomplished by a large dozer with ripper attachment.

13. The natural materials encountered in the test pits were generally suitable for founding the spillway. We believe minimal foundation preparation will be required.

14. The on-site sands and gravels encountered in the test pits could be used for structural fill material.

15. In our opinion, riprap borrow material or drain material could be obtained by processing (screening and/or washing) the material from the current borrow source on the knob northwest of the darn. Some breakdown of riprap due to freeze thaw deterioration would be expected if the material has similar properties to test pit 7. In addition, the gravels, cobbles and boulders are generally subrounded, and should be placed at a moderately flat slope to minimize the potential for some dislodging due to wave action. We believe that riprap areas that develop deterioration can be replaced with a routine inspection and maintenance program. Other, sources such as the higher quality angular rock noted on portions of the north half of the darn, would involve lower maintenance and be less likely to dislodge by wave action, if such a source is developed.

7-18

8.0 SAFETY INSPECTION AND OPERATIONAL ANALYSIS

8.0 SAFETY INSPECTION AND OPERATIONAL ANALYSIS

8.1 INTRODUCTION

The facilities at Wheatland Reservoir No. 2 were inspected on July 21, 1989. Present were personnel from Banner Associates Inc., Woodward-Clyde Consultants, Wyoming State Engineer's Office, Wyoming Water Development Commission, and the dam caretaker. The dam caretaker operated the outlet works gates and explained the operation of the outlet works and spillways. The existing facilities, the dam embankment, and the main spillway embankment were also video taped during this site inspection. Additional facilities inspection by personnel from Banner Associates occurred on September 18, 1989. The safety inspection for the dam embankment and the main spillway embankment is discussed in Section 7, Geotechnical Analysis.

8.2 OUTLET WORKS

8.2.1 Existing Facilities

The existing outlet works consists of two 84" diameter reinforced concrete intake conduits with flared end inlet sections, a gated wet well with four high pressure control gates (two high pressure gates for each intake conduit), two horseshoe shaped outlet conduits, and a gate house. The intake conduit upstream of the gate house is approximately 80 feet in length. The gate house is located over the gated wet well on the reservoir side of the dam embankment and houses an operator for each of the high pressure gates. A plan and profile of the existing outlet works is shown on Figure 8-1.

The gates are operated with a portable electric drill that is moved between operators as required. The dam caretaker typically only has one drill on site and there is no backup. The gates are furnished with a manual crank if the electric drill fails or electrical power is interrupted. Also there is a small portable electric generator available in the event of power failure.

The conduit outlet consists of two 115 foot long, 6'3" horseshoe corrugated metal pipes. The conduit has an approximate inlet invert elevation of 6934. It is unknown if the conduit has seepage collars. The invert of the outlet conduit is lined with concrete.

The only areas of the outlet works that could be inspected were the gate house, the gate operators, and that portion of the outlet conduits from the downstream side of the high pressure gates to the downstream end of the horseshoe conduits. The intake conduits, gated wet well, and downstream apron could not be dewatered and were submerged and could not be inspected.

8-1

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22'-0"

~======~~============================~

2-I.D Steel P'iH' ~ ~~~::=====::=:=================~~~J:*}f~==~A--~=======-=====""",,:r--=========-=============+~ Fiarrd End Inle t Sec t,on i

En. W.II

Flared End Inlet S~ctlon-",

with Trash Rack

TAKEN FROM DRAWINGS BY HNTB (HOWARD. NEEDLES. TAMMEN & BERGENDDFFl DATED 9/19/73.

BANNER BANNER ASSOCIATES, INC. • CONSULTING ENGINEERS L ARCHITECTS 620 PLAZA COURT. P.D.IOX 550 - LARAMIE. WY 82070 • 13071 745-7366

,/ ,/

/'

,/ ,/

,/

"...

I I

,)- --

~84" Reinforced Concrefe Pipe, Clau J wdh R-4 JOint""

I

\" Top D,r 8&,,", £/&VG ~"'t!Jn 6961'..) :

I

----~---------/!

,I // ~I / 1 //

/ /

/

T~lIn~irioT7 Sec.rion

Sfa 10' 21 (

PLAN VIEW OUTLET CONDUIT

(Top not shown)

EXISTi"9 Cont/ul'"

PROFILE ON t OF CONDUI T


(En"" Wall

c¥/,sring OM'rt .. ,.. S",,.ucr,,,.,. ..

W H EAT LA NOR ESE RV 0 I R NO. 2 OUTLET WORKS TUNN EL

8-2

FIGURE:

B-1

8.2.2 Deficiencies and Problems

The downstream outlet conduit is in good condition. There is minor rusting of the corrugated lining in some areas but nothing to cause concern. By tapping the perimeter of the conduit at several locations along its length, we determined that there are some void areas in the grout behind the lining. A cross section of the downstream outlet conduit is shown on Figure 8-2.

The gate house has a finish floor elevation of approximately 6967 and the top of the dam embankment is approximately 6972. Since the gate house is of the reservoir side of the dam embankment, water levels above 6967 may flood the gate house. The gate house has some cracks visible in the concrete masonry units (CMU) mortar joints which could allow moisture to penetrate into the block and cause deterioration. There is backfill against the block wall on the reservoir side of the building which will also hold moisture against the block.

At the time of this inspection, there were no leaks observed at the high pressure gates; however, the reservoir water level was low. A section of steel pipe, which was the stilling well for the abandoned Steven's water level gauge, in the gated wet well is not anchored down and is loose. Therefore, there is the possibility the pipe could become j arruned in the high pressure gates when they are open making it impossible to totally close the gates, or possibly damage the gates.

A whirlpool was visible in front of the intake conduits when water was being released. The outlet conduits do not have trash racks or antivortex devices at the intake. At the time of the inspection it was noted that the power pole adj acent to the gate house was leaning precariously. Subsequently there has been notification that another power pole has been installed adjacent to the "leaning" power pole and the two have been strapped together, thus improving the situation.

If the reservoir is ever opened to the public, the area around the intake of the outlet works would require a safety device to keep boats, fishermen, and swirruners away from the intake area.

8.2.3. Conclusions and Recorrunendations

The outlet conduits should have trash racks and an antivortex device installed at the intake. The trash racks would prevent logs and debris from going through the outlet works and causing damage. The anitvortex device would improve the efficiency of the outlet conduits.

The upstream outlet works conduit and gated wet well should be inspected to determine the condition of the outlet works upstream of the high pressure gates. This will require a scuba diver who is experienced with underwater inspection of dam structures or this inspection may be accomplished during future construction activities. The outlet works intake area will require dewatering for anti-vortex device and trashrack installation. Additional inspection of the facilities that are normally underwater may be conducted

8-3

I

L~

TAKEN FROM DRAWINGS

- Tunnel Liner

Conc.rl£t-~ BcroSe

10 Ga.:!e ,<-feral CorrU!lare.d T .. ""1.1 /"I/Ic-r

TYPICAL CROSS SECTION OF OUTLET

NO SCALE

BY HNTB (HOWARD, NEEDLES, TAMMEN 8. BERGENDOFFl DATED 9/19/73.

BANNER BANNER ASSOr:IATES. INL • r:ONSULTING ENIiINEERS L ARr:HITEr:TS 620 PLAZA COURT. P.O.BOX 550 - LARAMIE. WY 12070 • (3071745-7366


I

11/

.. , TUNNEL LINER PLATE DETAIL

WHEATLAND R ESERVO I R NO.2 OUTLET WORKS

8-4

Grout- Are.o.

FIGURE:

8-2

at that time, and repair items determined from this additional investigation may be handled as force account work to the construction contract. This type of inspection should be performed at approximately ten year intervals or more often if conditions warrant.

The downstream outlet works conduit should be completely sounded for voids behind the steel liner and any voids grouted full. The conduit should be inspected each spring to check the condition of the steel lining, and repairs made as required.

Any cracks in the CMU mortar joints of the gate house should be re-pointed and any cracks in the CMU block should be epoxy filled. The backfill against the wall on the reservoir side should be removed and the grade around the building sloped such that water will be directed away from the building. If the existing dirt berm is for protection of the building from high water or waves, other means of protection should be provided.

The steel pipe in the gated wet well of the gate house should be removed before it becomes wedged in the control gates or possibly caught in the downstream outlet conduit.

The high pressure gates should be checked for leaks and adjusted as required when the downstream conduit is inspected each year.

8.3 MAIN SPILLWAY


The main spillway is located at the north end of the reservoir, and consists of a gated structure with four 14' wide by approximately 8' high roller gates. The top of the bridge deck over the gates is at elevation 6967 . 0 which is approximately 4.5 feet below the top of the main dam embankment. A plan and elevation of the main spillway is shown on Figure 8-3.

The roller gates are steel framed with an upstream corrugated steel skin. The sill elevation of the gates is approximately 6956. The gates are operated by a hand geared lifting hoist on each gate with access to the hoisting mechanism provided by a single lane vehicle bridge across the top of the spillway structure. Once the gates have been opened, the gates will not close on their own and must be forced shut.

8-5

OPE RAT 0 R CON C R ET E TOP 0 F CUR B ITYP.J~ WALL ITYP.J~ ON BRIDGE,

~r~=~==~ ~I(~~======~~~~==' ==~ ~~1t~~~===*\~Jr.~ 1------f----------

fr----------

1. 5'~1 1~ 13.7'

f:=-- ---~---------1

,------ -----r

TOP OF CO NCR ETE

S ILL ~--'--_---'j

I-r-- _- _- _ - _- _- _-_- ----j

TOP OF CON CRETE APRON\

2.0' 2.0 ' 2.0'

TOP j OF GATE

14.1 '

ELEVATION OF GATES (AS VIEWED FROM RESERVOIR) SCALE: 1" '" 10'

EL. =: 6967.0±

EL. =: 6963.9±

EL. '" 6956± EL. =: 6954±

V (HA NN El TO LARAMI E Him

t-:z w L:

"" :z « dJ L: UJ . >-« ~ -' a.. U1

z « L: (TJ

u.. l{: a a-

D <i. z UJ tIl

/

// /~ .. / / EL .• 696 8.7 /./ --

/ ~ ...... // 1/ / /

V' / / El. • 6966.8 ,..- /

/~- / / \'/

/ / / /

/ /

// /\ / / :: ( EL. • 6966.5

/ / / PRO FI LE RIGHT EDGE EMBA NKMENT . / / / IHIGH SIOEI

/ /

/ ...... \ / / / / EL.· 6966.6

[ON [ RETE APRON I '\ WING WALL {TYP.I / /

tZ W :c "" z « dJ :c w

/ / / /

\ / / CUR B ITYP.l~. ____ / /

~~~~==n===jIl=t1- - - - - - - /

~ ~ ~ ~ ~ :;I-OGE--------~ r ~ ~ ~ ~ ___ I\~\:: \ fl .. 6R 56 }

/ --- ---K' ~GATEITYP.l E L .·6966.~ _ ~'-{:-- _ \ - El. • 69 66 .9 ~y~~A6~R4 1 : _ 0 _

_ - -;... - EL .• 6966,3 ~ « ............... _ - .; NHWL· EL . 6964.0 t;; - --- -\~ -

TOP OF GATE· EL . 69 63.9'

a.. tIl - -- _ EL. = 6966.6 - -- -z « L: - -/ -u.. / _

Cl / \' "'0 / / ~ ';' / / / / EL .• 6967.0 ~o /' / '" « / / ~t;; /

/ /

'eEl. = 696 7.8

BANNER BA NNER ASSOC IATES. INC. • CONSULT ING ENGINEERS ~ ARCHITE CTS 620 PLAZA CO URT. P.D.BOX 550 - LAR AMI E, WY B2070 • 130 71745-7366

« tU1

MAIN SPILLWAY STRUCTURE

MAIN SP ILLWAY EMBANKMENT PLAN SCALE: 1" = 50'

WHEATLAND RESERVO IR NO.2 REHABI LITATI ON - PHASE I ,

N , I

\-. WHEATLAND NO.2 RESERVO IR \

DATA TAKEN FROM ACTUAL FIELD SUR V EY 2 B -AUG -B 9 .

WHEATLAND RESERVOIR NO.2 MAIN SPILLWAY

8 6

FIG UR E:

B-3

\

The abutments of the spillway are vertical walls with wing walls extending upstream and downstream from the abutments. A concrete apron extends from the upstream wing walls to the downstream wing walls. A cut-off wall is located approximately 4' downstream of the concrete apron and extends the full width of the channel. An underdrain system is visible at the downstream side of the concrete apron. Bridge piers act as splitter walls between the gates and provide support for the lifting hoist.

The main spillway discharges into a channel which extends approximately 1.2 miles to the Laramie River.


The upstream concrete apron was covered with silt and could not be inspected. The majority of the downstream concrete apron has surface spalling and cracks. One slab section has eroded enough to expose some reinforcement along the downstream edge of the apron. The cut off wall beyond the downstream apron is spalled and eroded on the exposed surfaces.

There are spalled and honeycombed areas on the bridge piers, wing walls, and abutments. There are also some large cracks in the wing walls and abutment walls.

The steel framing of the roller gates is rusted and there are rust areas on the corrugated skin of the gates. There was no water against the gates at the time of inspection so it was not possible to observe water tightness of the gates. The gate rails should be checked and regrouted as required.

The gate hoists were locked and were not operated although all hoists appeared to be operable. There is some spalling below the hoist bearings. The bridge deck appeared to be in good condition. The bridge guard rail is rusting and has been bent. The intermediate rail is missing between two of the rail posts.

A concern expressed by the Wheatland Irrigation District has been the remote location of the main spillway, and that difficult access to this remote location may hinder manual operation of the gates.

Wheatland Irrigation District personnel stated that the main spillway discharged in 1983 and again in 1984 and there were no clear recollections of discharges prior to that time. Wheatland Irrigation District personnel did recall that there was very little or no erosion in the main spillway discharge channel prior to 1983. The soil downstream of the main spillway structure is highly erodible. Even though the main spillway has discharged few times there are numerous locations along the channel that the discharged flow has eroded a channel approximately 20 feet to 30 feet deep with steep or near vertical sides. Landowner's along this channel have expressed concerns that grazing livestock may fall into this channel.

8-7

8.3.3 Conclusions and Recommendations

The upstream concrete apron should be cleaned and inspected for damage. Any spalled areas should be patched and all cracks should be epoxy injected. If the condition of any slab section is too badly deteriorated, it should be removed and replaced. The downstream concrete apron has some surface spalling and some cracking. The slab should be cleaned to sound concrete and a new topping slab placed over the existing slab. The new slab should be bonded and anchored to the existing slab, and extended another 50' downstream to provide channel protection. The existing underdrain should be extended to the end of the new concrete apron also. A new cut-off wall should be incorporated into the end of the new apron :,slab to prevent scouring at the end of the apron.

The spalled and honeycombed areas on the bridge piers, wing walls, and abutments should be removed to sound concrete and patched. Any cracks in the piers or walls should be epoxy inj ected. The gate rails should be inspected and regrouted to provide full and continuous bearing behind the rails. Any spalled areas below the hoist bearing pads should be removed to sound concrete and patched.

The rust should be removed from the roller gates and all steel painted. The corrugated steel skin on the face of the roller gates should be replaced. All rollers should be repaired as required, and all cables checked and replaced as required. Hoists should be cleaned, lubricated, and repainted. All gates should be exercised at least once a year, lubricated, and repaired as required.

The bridge railing should be straightened, missing rails replaced, and the rails repainted. New railing should be added to the upstream side of the bridge, and a platform with guardrail installed at each hoist operator.

Additional rehabilitation alternatives for spillway replacement are discussed in Sections 9.2.5 "Armoring" of the Main Spillway Embankment, and 9.2.6 Replace Main Spillway and Main Spillway Embankment.

Additional options for either improving site access or remote control of the main spillway gates are discussed in Section 9.2.9 Improve Main Spillway Access.

Several options for rehabilitation of the main spillway discharge channel were investigated. These rehabilitation alternatives are discussed in Section 9.2.7 Upgrade the Discharge Channel Downstream of the Main Spillway.

8.4 AUXILIARY SPILLWAY


The auxiliary spillway is located on the left abutment of the dam embankment and consists of a gated structure with three 12' wide by 10' high roller gates. Top elevation of the bridge deck over the gates is

8-8

embankment is overtopped. A plan and elevation of the auxiliary spillway is shown on Figure 8 -4. The auxiliary spillway discharges into a canal which extends for approximately two miles, at which point a large drop structure divides flow between the Wheatland Reservoir No. 3 and the Laramie River channel. Inspection of the supply canal to Wheatland Reservoir No. 3 was not included in the scope of this report and this canal was not inspected.

The roller gates of the auxiliary spillway are steel framed with an upstream corrugated steel skin. The sill elevation of the gates is 6954.0. Each gate is operated by a hand geared lifting hoist with access to the hoisting mechanism provided by a single lane vehicle bridge across the top of the auxiliary spillway structure. Once opened, the gates are typically difficult to close again. Historic operation has been to release all tension in the hoist cables and then drop a large rock on top of the gate. If this method is unsuccessful it is necessary to bring in a front end loader to push the gates shut.

The abutments of the auxiliary spillway are vertical walls with wing walls extending upstream and downstream from the abutments. Slope paving extends beyond the downstream wing walls to the downstream apron slab. Bridge piers act as splitter walls between the gates and provide support for the lifting hoist.


The concrete aprons were covered with silt and could not be inspected. The downstream slope paving on the right side has a large area that has spalled although no reinforcement was visible.

There are minor spalled areas on the wing walls and bridge piers. The upstream nose of each bridge pier has an embedded angle which is badly rusted below the high water mark.

The steel framing of the roller gates is rusted and there are rust areas on the corrugated skin of the gates. There was no water against the gates at the time of inspection so it was not possible to observe the water tightness of gates.

The gate hoists appeared to be in good working condition. bearing at the top of the piers is spalled on all piers.

The hoist

The bridge deck is partly covered with gravel and was not visible at the time of inspection. That portion visible on the top of the bridge and the bottom of the bridge deck appear in good condition.


The concrete aprons should be cleaned and inspected to determine if there is any damage. Any spalled areas should be patched and any cracks should be epoxy injected. If the condition of any slab section is too badly deteriorated, the slab should be removed and replaced.

8-9

CONCRETE WALL (TYP.J~

OPERATOR (TYP .)

TOP OF CURB ON BRIDGE

1 TOP OF !

EL. = 6972.S±

I ' I GATEl I I I I _ 1 EL. = 6963. 9:!: rr--- I' fr---- r---L--~,! II ~.-- i II TOP OF I Ii i

I !! Ii. II 'I ~ CONCRETE I. I Ii I

U J l~P~_ON_=lJJ ii i EL. = 6954±

I ! I I I I II 9' -'I I, E 2.0' 2.0';;...! I..:: 11.9' 0;.":: 12.0' 30E • ~

2.0' 2.0'

ELEVATION OF GATES (AS VIEWED FROM RESERVOIR) SCALE: }" = }Ol

r SUPPLY CANAL TO ______________ ~ WHEATLAND NO.3 RESERVOIR

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

I CURB !TYP.)

I

l L CONCRETE

~ CATTlE6UARD

I I I STA, ,-"

I .

I V APPROX. t TOP OF EMBANKMENT

i I

ROAD

STA.7·10

GATE !TYP.I

NHWL • El. 6964.0

"- WHEATLAND RESERVOIR NO. 2\

- ----- ------ ----I APRON7

TOP OF GATE· El. 6963.9!

DATA TAKEN FROM ACTUAL FIELD SUR V EY 2 B -A U G -B 9 .

BANNER BANNER ASSOCIATES. INC. • CONSULTING ENGINEERS 8. ARCHITECTS 620 PLAZA COURT. P.O.BOX 550 - LARAMIE. WY 62070 • (307) 745-7366

AUXILIARY SPILLWAY PLAN SCALE: }" = 40 1


CURTAIN WALL mp. I WING WAll !TYP.)-l

STA. 6.05

OPERATOR (TYP. OF 3)

WHEATLAND RESERVOIR NO.2 AUXILIARY SPILLWAY

8-10

FIGUREr

8-4

The hoist bearing areas should be removed and replaced to provide uniform bearing under the hoist. All other spalled areas in concrete should be patched and all cracks epoxy injected. The gate rails should be inspected and regrouted to provide full and continuous bearing behind the rails.

The rust should be removed from the roller gates and the pier nosings and all steel should be painted. The corrugated steel skin on the roller gates should be replaced. All rollers should be repaired as required, and all cables checked and replaced as required.

Hoists should be cleaned and lubricated. All gates should be exercised at least once a year, lubricated, and repaired as required. A platform and guardrailing should be installed at each hoist operator.

Personnel from the Wheatland Irrigation District have expressed the desire to investigate the possibility of adding electric motor operation to these gates for easier operation. This rehabilitation alternative is discussed in Section 9.2.10 Motorize Auxiliary Spillway Gate Operation.

The bridge deck covered with gravel should be cleaned and the bridge deck inspected. Any damaged areas should be repaired as required.

8.5 ADDITIONAL FACILITIES


There are three small irrigation outlet works in the dam. During the inspection, the outlet for the Irrigation Outlet No. 2 near the right abutment could not be located. Later discussions with the WID indicated that the outlet pipe extends quite a distance downstream before daylighting. It is also possible cattle may have trampled dirt over the outlet obscuring it. These outlet works consist of submerged low level intakes, gate valve or slide gate control at or near the upstream end of the pipe, conduit in the l2-inch to l8-inch diameter range and an outlet into a small irrigation ditch. The capacity of these outlets is small in comparison to the main outlet works.


The operators on the irrigation outlet works are in poor condition. One of the outlets does not operate anymore and appears to have been abandoned. The remaining two outlets can be operated if the operators are lubricated.


The outlet that appears to have been abandoned should be inspected and verified that it has been properly plugged. The remaining two outlets should have the operators repaired, lubricated, and the control valves inspected and repaired as required. If it is determined the irrigation outlets are not required any longer, they should be abandoned and properly plugged.

8-11


9.1 INTRODUCTION

The Geotechnical Analysis and the Safety Inspection and Operational Analysis revealed no "fatal flaws"; that is, no deficiencies of a maj or nature with a high probability of a catastrophic failure in the immediate or near future. Also the Flood Analysis demonstrated that there is no need for a spillway sized to pass the Full PMF. These analyses did; however, reveal several deficiencies and potential problems which can be classed as "deferred maintenance" items; that is, items that have been neglected and should be included with an ongoing operation and maintenance program. In addition, there are several areas that were defined in both the Geotechnical Analysis and the Safety Inspection and Operational Analysis Sections that may require further investigations to better define the rehabilitation efforts required.

We have developed several rehabilitation alternatives based upon these investigations and discussions with the Wheatland Irrigation District. A preliminary opinion of probable construction cost has been developed for some of these rehabilitation alternatives. Costs are based on 1989 dollars with no inflation factors for construction in subsequent years.

9.2 ALTERNATIVE ANALYSES

9.2.1 Abandonment

The Economic Analysis determined that for all levels of a probable maximum flood there would be no appreciable difference in incremental damage to existing lands and facilities within the floodplain regardless of whether Wheatland Reservoir No. 2 were in existence or not. The darn serves to store irrigation water for downstream farmers and ranchers. This benefit would be lost if the darn were to be abandoned. Therefore, there is no safety or economic benefit in abandonment of the darn, and no opinion of probable cost has been developed.

9.2.2 Do Nothing

One alternative is to "do nothing" to the existing facilities. The Economic Analysis determined that there would be no appreciable difference in incremental damages for all flood events analyzed regardless of whether Wheatland Reservoir No. 2 were in existence or not, and the Geotechnical Analysis and the Safety Inspection and Operational Analysis revealed no "fatal flaws" with the existing embankments and facilities.

The current operation and maintenance program has allowed some deterioration of the embankments and structures, and if this alternative is pursued this deterioration would continue. Although it has been determined that this would not appreciably increase the downstream damages due to a flood event; the logical assumption is that at some point the ability of

9-1

Wheatland Reservoir No. 2 to function as intended would be decreased or possibly cease. Also, at some point of deterioration, safety due to failure of the embankment becomes a paramount concern. This deterioration of existing embankments and structures could be further slowed by future adjustments to the maintenance programs.

Obviously, there are no immediate costs for the "do nothing" rehabilitation al ternati ve ; however, at some point, "deferred maintenance" items would become a safety hazard and would require greater and presumably more costly rehabilitation efforts.

9.2.3 Additional Investigations

The Geotechnical Analysis and the Safety Inspection and Operational Analysis sections of this report discussed additional research and investigations that should be considered. These items include:

o Additional inspection of the outlet works facilities upstream of the high pressure gates. This inspection may require the services of a scuba diver experienced with the underwater inspection of dam structures, or these investigations may be accomplished during future construction activities. The outlet works intake area will require dewatering for anti-vortex device and trashrack installation. Additional inspection of the facilities that are normally underwater may be conducted at this time, and repair items determined during this additional investigation may be handled as force account work to the construction contract.

o Additional research should be conducted to develop an operation, maintenance, and inspection program to reduce the likelihood of future "deferred maintenance" items becoming major repair items. This program may include riprap replacement on the upstream dam embankment as well as on the main spillway embankment, a rodent control program, monitoring of the piezometers and movement monuments, monitoring of seepage rates at different reservoir levels, and timely detailed inspection and operation of all outlet works, main spillway, auxiliary spillway facilities, as well as the irrigation facilities. This program should also include an emergency action plan.

o The outlet works, main spillway, and auxiliary spillway facilities as well as the additional irrigation facilities should be inspected and operated at reservoir levels up to at least the NHWL elevation 6964. This is work which is traditionally conducted under another Level II analysis.

o Additional strength testing and stability analyses should be performed as well as observation and analysis with the reservoir at higher water levels. This work is traditionally undertaken as a Level II task.

9-2

These additional investigations include completion of the above items along with the development of a comprehensive operation, maintenance and inspection program. These investigations may occur with subsequent levels of study and/or the operation, maintenance, and inspection program may be developed following completion of construction of additional rehabilitation alternatives. Other tasks can be accomplished under new Level II studies.

Due to the preliminary nature of the scope of these investigations, an opinion of probable cost for either these investigations or the costs associated with the implementation of these programs has not been developed at this time.

9.2.4 Upgrade Existing Facilities

Another rehabilitation alternative is to "upgrade" existing facilities (embankments and structures). This alternative addresses the "deferred maintenance" items, and includes those construction items listed in the Geotechnical Analysis Section 7.6 items 1 through 7;

1. Fill in low area of darn crest,

2. Riprap upstream darn face,

3. Rodent control program,

4. Repair "sink-hole",

5. Repair two sloughed areas,

6. Re-establish or install new piezometers, seepage measurement weirs and embankment movement monuments,

7. Repair existing irrigation outlets;

and those construction items discussed in the Safety Inspection and Operational Analysis Sections 8.2.3, 8.3.3, 8.4.3 and 8.5.3;

8.2.3 Repairs to the outlet works and control building,

8.3.3 Repairs to the main spillway,

8.4.3 Repairs to the auxiliary spillway,

8.5.3 Repairs to the existing irrigation outlets.

9-3

Several of these "deferred maintenance" items if ignored could deteriorate to become dam safety concerns.

An opinion of probable cost for this rehabilitation alternative is difficult to determine since quantities may be difficult to determine, and may change considerably with results from further investigations as outlined in Section 9.2.3 above. (For example, it is difficult to estimate costs for backfilling the existing rodent holes.) Construction and bidding documents will be difficult to produce, as well, and it is anticipated much of this rehabilitation work will be accomplished with a negotiated time and material contract. Also, the Wheatland Irrigation District may elect to perform some of the work themselves.

A preliminary opinion of probable cost to upgrade existing facilities is shown on Table 9.1. The cost developed for this rehabilitation alternative is $920,000.00; however, these costs may be substantially reduced if the Wheatland Irrigation District elects to perform several of these "upgrade" items themselves.

9-4

TABLE 9.1 WHEATLAND RESERVOIR NO.2

UPGRADE EXISTING FACILITIES PRELIMINARY OPINION OF PROBABLE COST

ITEM DESCRIPTION

Upgrade Dam Embankment Section 7.6 Item I-Fill in low area of dam crest

Item 2-Riprap upstream dam face Item 3-Rodent control program Item 4-Repair "sink-hole" Item 5-Repair two sloughed areas Item 6-Re-establish or install new

piezometers, seepage measurement weirs and embankment movement monuments

Item 7-Repair existing irrigation outlets

UNIT

LS LS LS LS LS LS

LS

SUBTOTAL

Upgrade Outlet Works LS Install Trash Racks and Vortex Splitter Wall Repaint Concrete Block, Interior, Exterior and Doors Replace Latch Set Remove Steel Pipe in Wet Well Site Grading and Installation of Protection Wall Grouting Behind Steel Liner

Upgrade Main Spillway LS Repair and Install Guardrail Repair Piers Repair Downstream Apron Repair Underdrain Below Apron Repair Cracks and Spalled Concrete Replace Skin on Gate, Repair, and Repaint Gates

Upgrade Auxiliary Spillway Repair Guardrail Repair Piers Remove and Replace Apron Slabs Remove and Replace Slope Paving Repair Cracks and Spalled Concrete Replace Skin on Gates, Repair, and Repaint Gates


15% Contingencies



9-5

LS

SUBTOTAL

SUBTOTAL

SUBTOTAL

SUBTOTAL

TOTAL

USE

AMOUNT

$ 67,000.00 $215,000.00 $ 53,000.00 $ 2,000.00 $ 2,000.00 $ 20,000.00

$ 7,000.00

$366,000.00

$ 48,000.00

$ 74,000.00

$ 60,000.00

$548,000.00 $ 82,200.00 $630,200.00 $ 94,530.00 $724,730.00 $108,710.00 $833,440.00 $ 83,334.00 $916,784.00

~920z000.00

9.2.5 "Armoring" Of The Main Spillway Embankment

Although the Economic Analysis determined that there would be no appreciable difference in incremental damages due to the magnitude of the flood event, the Flood Analysis did show that the main spillway embankment would be overtopped with the 25% PMF. If the main spillway embankment is overtopped during a flood event, it will sustain some damage and possibly a breach. This damage would have to be repaired following the flood event or the operational capacity of the reservoir would be decreased. One rehabilitation alternative is to "armor" the main spillway embankment. This "armoring" would consist of placing a conventional concrete slab on the upstream side of the embankment, on the crest and on the downstream side of the embankment. Concrete cut-off walls would also be placed at the upstream toe and the downstream toe of the embankment to prevent erosion and undercutting of the slab. The "armoring" would allow overtopping of the main spillway embankment during a major flood event and minimize the damage to the embankment.

A preliminary opinion of probable cost for "armoring" of the main spillway embankment is shown on Table 9.2. The cost developed for this rehabilitation alternative is $575,000.

9.2.6 Replace Main Spillway And Main Spillway Embankment

Rather than upgrade the existing main spillway and "armor" the main spillway embankment, the rehabilitation alternative of demolishing the existing main spillway facilities and the main spillway embankment and replacing these facilities with roller compacted concrete was investigated. This roller compacted concrete embankment would be designed to be overtopped with the 25% PMF or larger storm. This rehabilitation alternative would eliminate operational difficulties with the main spillway gates.

Various crest elevation configurations from 6964 (NHWL) through 6967 were considered. If this rehabilitation alternative is recommended for further investigation, these various crest elevation options will be analyzed; however, for this study and to develop a preliminary opinion of probable cost a crest elevation of 6964 was assumed for a length of 600 feet and a crest elevation of 6968 was assumed for a length of 200 feet. These assumptions also included a 100 foot gradual transition at both ends of the embankment from the 6964 to the 6468 crest elevation. The assumed crest cross section included a 15 feet crest width with upstream and downstream slopes of 3 feet horizontal to 1 foot vertical, and an 8 feet wide by 5 feet deep key for the entire length of the embankment.

A preliminary opinion of probable cost for replacing the main spillway and the main spillway embankment with a roller compacted concrete embankment is shown on Table 9.3. The cost developed for this rehabilitation alternative is $860,000.

9-6

TABLE 9.2

WHEATLAND RESERVOIR NO.2 "ARMORING" OF THE MAIN SPILLWAY EMBANKMENT

PRELIMINARY OPINION OF PROBABLE COST

ITEM DESCRIPTION QUANTITY UNIT

Concrete Slab 6" Thick x 880' Long x (12' + 27' + 20') wide

Upstream Concrete Cut-off Wall (2' deep x l' wide x 880' long)

Downstream Concrete Cut-off Wall (2' deep x l' wide x 880' long)

1000 CY

70 CY

70 CY


15% Contingencies



UNIT PRICE

$ 300.00*

$ 300.00*

$ 300.00*

SUBTOTAL

SUBTOTAL

SUBTOTAL

SUBTOTAL

TOTAL

USE

AMOUNT

$300,000.00

$ 21,000.00

$ 21,000.00

$342,000.00

$ 51,300.00

$393,300.00

$ 58,995.00

$452,295.00

$ 67,844.00

$520,139.00

$ 52,014.00

$572,153.00

$575,000.00

* The Unit Price includes ordinary foundation preparation, forming, reinforcement, and stripping of forms.

9-7

TABLE 9.3

WHEATLAND RESERVOIR NO.2 REPLACE MAIN SPILLWAY AND MAIN SPILLWAY EMBANKMENT

PRELIMINARY OPINION OF PROBABLE COST

ITEM DESCRIPTION

Demolish Existing Main Spillway Removal of Existing Main Spillway

Embankment and Foundation Preparation for Roller Compacted Concrete Embankment

Roller Compacted Concrete

QUANTITY UNIT

1 9000

9100

LS CY

CY


15% Contingencies

15% Engineering


9-8

UNIT PRICE

$ 4.00

$50.00

SUBTOTAL

SUBTOTAL

SUBTOTAL

SUBTOTAL

TOTAL

USE

AMOUNT

$ 20,000.00 $ 36,000.00

$455,000.00

$511,000.00

$ 76,650.00

$587,650.00

$ 88,148.00

$675,798.00

$101,370.00

$777,168.00

$ 77,717.00

$854,885.00

$855,000.00

9.2.7 Upgrade the Discharge Channel Downstream of the Main Spillway

The main spillway discharge channel extends approximately 1.2 miles to the Laramie River. The main spillway has discharged few times over many years and the discharged flow has, in many places, eroded a deep channel with steep or near vertical sides. Landowners along this channel have expressed concern that grazing livestock may fall into this channel. The Wheatland Irrigation District has questioned the possibility of additional excavation along the channel to "flatten" the side slopes, or the addition of fencing along the sides of steeper portions of the channel.

A preliminary opinion of probable cost was developed to "flatten" the channel side slopes and reduce the likelihood of livestock falling into the channel. The opinion of probable cost was developed assuming a constant 12 foot depth the entire length of the channel, with the average existing side slope at 1 foot horizontal to 1 foot vertical and "flattening" of the existing slope to 3 foot horizontal to 1 foot vertical. This determines an excavation quantity of approximately 68,000 cubic yards. The cost of excavation is assumed at $5.50 per cubic yard. A preliminary opinion of probable cost "flattening" of the steep channel side slopes is shown on Table 9.4. The cos t developed for this rehabilitation al ternati ve is $630,000. This cost does not include costs for land acquisition.

This "flattening" of the channel side slopes will alleviate some of the concerns connected with the steep side slopes; however, the channel may experience additional erosion following the next storm event of a magnitude large enough to require discharge through the main spillway. Thus, much of the rehabilitation efforts may last only until a subsequent discharge through the main spillway.

A preliminary opinion of probable cost to install fencing along the sides of steeper portions of the channel assumes 50% of the entire length for both sides of the channel would require fencing. This determines a quantity of 6340 feet. With an assumed cost of $4.00 per lineal foot of fence. A preliminary opinion of probable cost for fencing along the discharge channel of the main spillway is shown on Table 9.4. The cost developed for this rehabilitation alternative is $45,000.

9.2.8 Upgrade the Wheatland Reservoir No.3 Supply Canal and the Discharge Canal from the Supply Canal to the Laramie River

Currently, the auxiliary spillway discharges into a canal which functions as the supply canal to Wheatland Reservoir No.3. A drop structure is located along this canal which diverts water from the supply canal through a discharge canal to the Laramie River. This system of canals allows for discharges from the Wheatland Reservoir No. 2 auxiliary spillway to be routed to Wheatland Reservoir No. 3 or the Laramie River as well as enabling discharge from Wheatland Reservoir No. 3 to be routed through the supply canal, through the drop structure, and to the Laramie River, Although the canal system has a much higher capacity, historic discharges have been limited to approximately 700 to 750 cubic feet per second. Discharges in excess of these values cause excessive erosion in parts of the canals, with sediment deposits occurring in other parts of the canals.

9-9

TABLE 9.4 WHEATLAND RESERVOIR NO. 2

UPGRADE THE DISCHARGE CHANNEL DOWNSTREAM OF THE MAIN SPILLWAY

ITEM DESCRIPTION

Excavation

PRELIMINARY OPINION OF PROBABLE COST -"FLATTEN" SIDE SLOPES-

QUANTITY UNIT UNIT PRICE

68000 CY $5.50 (Includes Reseeding)


SUBTOTAL

15% Contingencies

SUBTOTAL


SUBTOTAL


TOTAL

USE

-FENCING ALONG CHANNEL-

ITEM DESCRIPTION QUANTITY UNIT UNIT PRICE

Fence 6340 LF $4.00


SUBTOTAL

15% Contingencies

SUBTOTAL


SUBTOTAL


TOTAL

USE 9-10

AMOUNT

$374,000.00

$ 56,100.00

$430,100.00

$ 64,515.00

$494,615.00

$ 74,192.00

$568,807.00

$ 56,881.00

$625,688.00

$630,000.00

AMOUNT

$ 25,360.00

$ 3,804.00

$ 29,164.00

$ 4,375.00

$ 33,539.00

$ 5,031.00

$ 38,570.00

$ 3,857.00

$ 42,427.00

$ 45,000.00

Rehabilitation alternatives to increase the carrying capacity of these canals would improve the operation of both Wheatland Reservoir No. 2 and Wheatland Reservoir No. 3 with respect to the storage and supply of irrigation water. This work will be evaluated in Phase II of Level II.

Investigations are ongoing to further evaluate these canals and define possible rehabilitation alternatives. Refer to Section 11.0 for ongoing surveying activities. At this time, no opinion of probable cost has been developed for this rehabilitation alternative.

9.2.9 Improve Main Spillway Access

The main spillway is located approximately 5.8 miles from the outlet works facili ties and the dam caretaker's house. Access from the caretaker's house is via an unimproved dirt road that follows along the downstream toe of the dam embankment and then forks with one road basically following the edge of the reservoir to the main spillway and the other fork turning up and following a ridge of higher ground to the main spillway location. Personnel from the Wheatland Irrigation District have expressed concerns that it may be difficult to access the main spillway to operate the gates in the event of a major precipitation event.

One option to reduce the access concerns is to provide the dam caretaker with a snowmobile, a four wheel drive vehicle or an all terrain vehicle. With these vehicles, the dam caretaker would be able to get to the main spillway location in more inclement weather; however, the possibility still remains that access would be impossible or dangerous even with these vehicles during a maj or precipitation event. No preliminary opinion of probable cost was developed for this. Another option would be to provide electric operation of the main spillway gates with an additional remote control location in the outlet works building. The existing main spillway location has no power supply, and a power source would need to be located and a power line extended to the vicinity of the main spillway location. The electric operators would have to be equipped with weather tight enclosures. A preliminary opinion of probable cost was developed to provide electric opening with remote control for the main spillway gate. The assumptions associated with development of these costs included:

o A primary power supply line is located within 1/4 mile of the main spillway site. The power company would extend the primary service to a location adj acent to the main spillway gates and supply the transformer.

o The requirements of the electric operator would be for single phase power only.

o The remote electric operation of the main spillway gates would be at the existing outlet works gate house.

o There is "line of sight" between the main spillway location and the outlet works gate house enabling the use of a radio controlled telemetry system.

9-11

o The main spillway gates would still require closure under their own weight.

The preliminary opinion of probable cost developed to reduce the main spillway access problems by adding electric operation of the main spillway gates with remote control is shown on Table 9.5. The cost developed for this rehabilitation alternative is $85,000. This cost is an additional cost not included in the costs developed to upgrade existing main spillway facilities.

The existing outlet works gate house is situated on the reservoir side of the embankment with a floor elevation below the level of the crest of the embankment. This may present problems during a major flood event. Subsequent studies may determine that construction of a separate building constructed at a "safer" location to house the remote electric operation of the spillway gates may be advantageous.

9.2.10 Motorize Auxiliary Spillway Gate Operation

Personnel from the Wheatland Irrigation District have expressed the desire to investigate the costs associated with supplying electric operators to the auxiliary spillway gates. This would greatly reduce the effort required for operation of these gates.

Development of a preliminary opinion of probable cost for this rehabilitation alternative contains the same assumptions as the preliminary opinion of probable cost developed for the rehabilitation alternative to provide electric operation with remote control for the main spillway gates, with the exceptions that there are only three spillway gates instead of four, and the primary power source is located closer to the auxiliary spillway gates location.

A preliminary opinion of probable construction cost to motorize the existing auxiliary spillway gate operation is shown on Table 9.6. The cost developed for this rehabilitation alternative is $65,000. This cost is an additional cost not included in the costs developed to upgrade existing auxiliary spillway facilities.

9.3 ALTERNATIVES RECOMMENDED FOR FURTHER CONSIDERATION

A wide range of rehabilitation alternatives have been investigated and a preliminary opinion of probable cost has been determined for several of these options. The determining factor for many of these rehabilitation alternatives is the fact that the Economic Analysis determined that there would be no appreciable difference in incremental damages associated with a maj or flood event and possible failure of the embankments; therefore, consideration of the recommended alternatives should revolve around providing the intended service, that of providing an irrigation water supply to the downstream farmers and ranchers and ability to pay for the improvements.

9-12

TABLE 9.5

WHEATLAND RESERVOIR NO.2 REDUCE MAIN SPILLWAY ACCESS PROBLEM

ELECTRIC OPERATION OF MAIN SPILLWAY GATES PRELIMINARY OPINION OF PROBABLE COST


Retrofit for Electric Operations Telemetry Power Company Costs Electrical Work

4 1 1 1


15% Contingencies



EA LS LS LS

UNIT PRICE

$ 5,000.00 $15,000.00 $ 5,000.00 $10,000.00

SUBTOTAL

SUBTOTAL

SUBTOTAL

SUBTOTAL

TOTAL

USE

NOTE: Power Company Monthly Usage Costs Have Not Been Included

9-13

AMOUNT

$20,000.00 $15,000.00 $ 5,000.00 $10,000.00

$50,000.00

$ 7,500.00

$57,500.00

$ 8,625.00

$66,125.00

$ 9,919.00

$76,044.00

$ 7,604.00

$83,648.00

$85,000.00

TABLE 9.6

WHEATLAND RESERVOIR NO.2 PRELIMINARY OPINION OF PROBABLE COST

MOTORIZE AUXILIARY SPILLWAY GATE OPERATION


Retrofit for Electric Operations Telemetry Power Company Costs Electrical Work

3 1 1 1


15% Contingencies



EA LS LS LS

UNIT PRICE

$ 5,000.00 $15,000.00 $ 3,000.00 $ 5,000.00

SUBTOTAL

SUBTOTAL

SUBTOTAL

SUBTOTAL

TOTAL

USE

NOTE: Power Company Monthly Usage Costs Have Not Been Included

9-14

AMOUNT

$15,000.00 $15,000.00 $ 3,000.00 $ 5,000.00

$38,000.00

$ 5,700.00

$43,700.00

$ 6,555.00

$50,255.00

$ 7,538.00

$57,793.00

$ 5,779.00

$63,572.00

$65,000.00

Based upon these preliminary investigations, the rehabilitation alternative of Abandonment of the dam as discussed in Section 9.2.1 and the Do Nothing alternative as discussed in Section 9.2.2 are not recommended for further consideration. The existing facilities provide a service to downstream farmers and ranchers and contains no "fatal flaws"; however, as with all facilities, continued maintenance is required for optimal performance.

Based upon these preliminary investigations and discussions with the Wheatland Irrigation District and WWDC, the recommended rehabilitation alternatives are the Upgrade Existing Facilities as discussed in Section 9.2.4.

Specifically, the recommended rehabilitation alternatives include:

o Fill in the low area of the dam crest.

o Rip rap the upstream dam face.

o Establish a rodent control program.

o Evaluate the cause and repair the "sinkhole".

o Repair the two sloughed areas.

o Re-establish, or install new piezometers, seepage measurement weirs and embankment movement monuments.

0 Repair exiting irrigation outlets.

0 Repairs to the outlet works and control building.

0 Repairs to the main spillway.

0 Repairs to the auxiliary spillway.

The preliminary opinion of probable cost developed for these recommended rehabilitation alternatives is shown on Table 9.1. The preliminary opinion of probable cost is $920,000.00. These costs may be substantially reduced if the Wheatland Irrigation District elects to perform several of these "upgrade" items themselves.

Recommended Additional Investigations are listed below. A preliminary opinion of probable construction cost was not developed for the following recommended Additional Investigations:

o Development of an operation, maintenance and inspection manual.

o Inspection and operation of the outlet works, main spillway, auxiliary spillway as well as the irrigation facilities at reservoir levels up to at least the NHWL at elevation 6964.

9-15

o Completion of additional strength testing and stability analyses as well as observation and analysis with the reservoir at higher water levels.

Based on the preliminary investigations, the remaining rehabilitation alternatives have merit. Also, incorporation of these rehabilitation alternatives may reduce the need for some of the upgrading existing facilities costs. For example, if the replace main spillway and main spillway embankment rehabilitation alternative is pursued, then the costs to upgrade the existing main spillway facilities are not required.

Additional input from the Wheatland Irrigation District and the Wyoming Water Development Commission is required for incorporation of additional rehabilitation alternatives into future investigations.

9-16

10.0 SURVEYING

10. a SURVEYING

Surveying activities were performed in conjunction with the site reconnaissance and the safety inspection and operational analysis.

Completed surveying activities include:

1. Centerline profiles of the dam and main spillway embankments were performed with elevations taken at 100 foot intervals. The dam embankment surveyed elevations are shown on Figure 2-3, and the main spillway embankment surveyed elevations are shown on Figure 8-3.

2. Measurements of the main spillway structure and of the auxiliary spillway structure were performed to verify existing drawings. These measurements are shown on Figure 8-3 and Figure 8-4.

3. Cross sections of the dam embankment were taken at 500 foot intervals.

4. Two cross sections were taken in each of the auxiliary spillway canal and in the main spillway discharge channel.

5. The elevation of the floor slab of the outlet works control building was tied to a USGS benchmark elevation.

6. A traverse was performed between the dam embankment and the auxiliary spillway embankment to establish a common horizontal datum.

7. The weir below the outlet works structure was measured and tied into the survey network.

8. The test pits were located and tied into the survey network.

9. The survey has been tied to government land corners.

10. The auxiliary spillway canal also serves as Supply Canal to Wheatland Reservoir No.3, including a structure to divert flows to the Laramie River. A profile of this canal is being performed, including cross sections taken at 1000 foot intervals, and at changes of the canal cross section or in the slope of the canal.

11. Measurements are being performed to detail the gate structure which diverts flows to the Laramie River and the drop structure associated with this gate structure.

10-1

11.0 PERMITS AND ENVIRONMENTAL STUDIES

11.0 PERMITS

11.1 INTRODUCTION

Several permits, clearances, and certifications may be required prior to Wheatland No. 2 Reservoir Rehabilitation construction. Some of these permits should be secured by the Wheatland Irrigation District prior to bidding the construction project, due to the long lead time necessary to obtain these permits. Other permits which are specific to a Contractor's operation and method of construction should be obtained by the Contractor, with a copy of these permits transmitted to the Sponsor prior to the commencement of any construction activities addressed by the permit. This section of the report provides a brief description of the permits that may be required for construction. Obviously, the magnitude of this permitting and the permitting effort depends largely upon the extent of the rehabilitation construction and which rehabilitation alternatives are pursued.

11.2 DREDGE AND FILL PERMITS (404 AND NATIONWIDE)

The U. S. Army Corps of Engineers, under Section 404 of P.L. 92-500 (Clean Water Act), requires permits to authorize dredging or placement of fill in the waters of the United States. An individual 404 Permit, Nationwide Permit authorization, or both, may be required to place fill material or to dredge material from a stream channel or other body of water. The Nationwide Permit process is simpler and much less time consuming than the 404 Permit process. It is anticipated for the extent of rehabilitation alternatives proposed in this report that the construction activities will be authorized by a Nationwide Permit.

As a part of the permitting process, an Environmental Assessment (EA) or an Environmental Impact Statement (EIS) may be required by the Corps of Engineers to evaluate projects. It is anticipated that an EIS will not be required due to the minimal environmental impacts associated with the rehabilitation alternatives proposed for this project. If authorization is granted under the Nationwide Permit process, an EA will not be required.

Normal process in time for a non-controversial 404 Permit application is two to three months; however, an allowance up to six months should be provided. The Corps may also require that a public hearing be convened to receive public input. The time frame to secure necessary permitting or authorization from the Corps is dependent upon the need for an EA, and the necessity to acquire 404 Permits rather than Nationwide Permit authorization.

11-1

11.3 SECTION 401 CERTIFICATION

The Wyoming Department of Environmental Quality (DEQ) , under Section 401 of the Clean Water Act, will review the application for 404 Permit activities with the intent to certify project activities in accordance with the Act. Normally, no additional requirements over and above the 404 Permit are required by the DEQ and, if they are, these requirements are incorporated into the 404 Permit. Processing of the 401 Certification is concurrent with the 404 Permit process.

11.4 ARCHAEOLOGY AND SPHO CLEARANCE

Clearance from the State Historical Preservation Officer (SPHO) is required before ground disturbing activities occur. In order to receive SPHO clearance, an archeological survey of the proj ect construction area must be made. Since most if not all of this proj ect occurs wi thin previously disturbed areas, the archeological survey effort should be minimal or not required at all.

11.5 STATE ENGINEER'S OFFICE AND WATER USE AGREEMENTS

The current permits on file with the State Engineer's will require updating with any rehabilitation activities associated with Wheatland Reservoir No. 2 and the Dam, although none of the proposed rehabilitation alternatives involve anticipated changes in the existing water right agreements.

Permits for temporary facilities and construction water are also required by the State Engineer's Office. Temporary sediment ponds require permits to construct from both the State Engineer's Office and the DEQ (see paragraph 11.6). If the Contractor requires temporary sediment ponds for his operation, he will be responsible to obtain the State Engineer's permits. These permits generally can be processed within 30 to 60 days. Temporary construction water requires the development of a Temporary Use Agreement with the permittee from which the water is being purchased. The Contractor will be responsible to locate and secure the necessary agreements and to file these forms and obtain the approval of the State Engineer's Office.

11.6 DEPARTMENT OF ENVIRONMENTAL QUALITY (DEQ)

Various permits may be required from the Wyoming DEQ to construct this project. Most of these permits are construction oriented and the Contractor should be assigned the responsibility to apply for and secure the construction oriented permits.

11-2

11.6.1 Water Quality Division (WQD)

The maj or thrust of permitting from the DEQ will be through the Water Quality Division.

Permits are required to construct temporary wastewater treatment facilities (sediment ponds) as may be required. At this time, the need for sediment ponds is not anticipated; however, if the Contractor requires a sediment pond for his ac ti vi ty , he will be respons ible to secure this permi t. Processing time for a permit to construct is generally 30 to 90 days.

A National Pollutant Discharge Elimination Systems (NPDES) Permit, also called a discharge permit, is required if discharges are made from a temporary waste water treatment facility into a receiving water of the State. An NPDES permit is also required if discharges are made into a receiving water from trench or other construction dewatering operations. Construction operations should be restricted to prohibit such discharges to only those absolutely necessary in order to avoid the need to acquire an NPDES Permit. Significant construction controversy and potential violations of State water quality standards and subsequent fines can be avoided by eliminating discharges into receiving waters. Also, this permit can take up to six months to acquire. A determination as to whether an NPDES Permit will be applied for by the Wheatland Irrigation District will be made during the design process, otherwise responsibility will be assigned to the Contractor.

In lieu of discharging directly into a receiving water as a point discharge, a diffused discharge of wastewater or dewatering effluent should be made. Generally, this process is termed land treatment and the DEQ is responsible to permit such operations. The Contractor will be assigned the responsibility to apply for and secure land application permits.

11.6.2 Land Quality Division (LOD)

The LQD is responsible for administering the permit process for m~n~ng

operations. The Contractor will require a material source for riprap and other aggregates. The Contractor will be assigned the responsibility to locate, secure, and obtain permits for borrow areas as required. The Contractor may elect to purchase these materials from a local supplier and avoid the need for a permit.

Waste areas may also be required to dispose construction debris, other than petroleum by-products. The Contractor will be responsible for acquiring a permit from the DEQ if he elects to develop a waste area. Otherwise, the Contractor should be encouraged to use existing landfills.

11-3

11.6.3 Air Quality Division (AQD)

Permits will be required from the AQD to burn selected construction debris and materials cleared from the right-of-way if the Contractor chooses to dispose of these materials by burning. Fugitive dust permits will be required for the Contractor's crushers. This permit generally travels with the individual piece of equipment and is the responsibility of the Contractor.

11.7 MISCELLANEOUS PERMITS AND SPECIAL REQUIREMENTS

The Contractor will be assigned the responsibility to prepare and submit for review to the EPA a Spill Prevention Control and Countermeasure (SPCC) Plan. The SPCC Plan will detail precautions and procedures to be followed in the event of an oil, fuel, or hazardous material spill.

The Contractor will also be responsible to contact the Wyoming Highway Department and Albany and Platte Counties to determine load limits and the extent of permitting that will be required to use State Highways and County roads for material hauling purposes. If permits, agreements, or licenses are required, the Contractor will be responsible to obtain these permits.

Prior to, and during the construction process, other permits and special requirements may be determined. These items will be addressed with the Wheatland Irrigation District to determine the best approach and who, the Wheatland Irrigation District or the Contractor, should be responsible for obtaining them.

11.8 LAND ACQUISITION/EASEMENTS

Activities of the Wheatland Reservoir No. 2 rehabilitation construction may require acquisition of easements and authority to occupy existing easements or rights-of-way. Construction activities may also include the purchase of additional land; however, at this time no land acquisition is anticipated for the rehabilitation alternatives proposed.

Securing easements required for the extension of any primary service power lines are the responsibility of the power company.

Landowner construction easements may be required for work along the main spillway discharge channel. Also landowner agreements and easements may be required on lands utilized as sources for borrow material. Typically, the Wheatland Irrigation District would determine a "reasonable" construction easement width along the discharge channel and secure the landowner construction permits, and the construction contractor may elect to negotiate additional construction easements with landowners at his expense. The agreements and easements with landowners for borrow materials may be secured by either the Wheatland Irrigation District or the construction contractor. During the design phase the engineer will work with the Wheatland Irrigation District to determine who, the Irrigation District or the construction contractor, should be responsible to obtain the permits associated with the borrow areas.

11-4

REFERENCES

REFERENCES

1. Phase I Inspection Report, National Dam Safety Program, Wheatland No.2 Dam, Albany County, Wyoming, Inventory Identification No. WY 0005, UoS. Army Corps of Engineers, Dated September 18, 1979.

2. Report of a Geotechnical Investigation For An Existing Dam, Wheatland Reservoir No.2, Albany County, Wyoming, Prepared by RBD, Inc., Fort Collins, CO, Project No. 5402-84, Dated January 4, 1985.

3. Wyoming State Engineer's Office - Permit No.1724, Ditch.

4. Wyoming State Engineer's Office - Report on Conditions of Wheatland Reservoir No.2, Permit No.1724, Prepared by Russell Dahlgren (Assistant Safety of Dams Engineer), Dated December 24, 1987.

5. Wyoming State Engineer's Office - Letter of February 1988.

6. Wheatland Irrigation District Report, Water Division No.1, Platte County, Wyoming, The Soil Conservation Service, Dated August 1988.

7. Hydrometeorological Report (HMR) No.55A Probable Maximum Precipitation Estimates--United States Between the Continental Divide and the 103rd Meridian, June 1988.

8. United States Department of the Interior, Bureau of Reclamation "Design of Small Dam, Third Edition".

9. Wheatland Irrigation District Reservoir No.2.

Historic Records for Wheatland

10. Means Site Work Cost Data, 1989, 8th Annual Edition, R.S. Means Company, Inc.

11. Plans for Renovation of Wheatland Irrigation District Reservoir No.2 Outlet; Howard, Needles, Tammen, and Bergendoff (HNTB) , September 19, 1973.

12. Western Research Corporation, Horse Creek Reservoir Proj ect Preliminary Economic Analysis: Agricultural Ability to Pay, Report Submitted to HDR Infrastructure, Inc., October 1, 1986.

13. Open-Channel Hydraulics by Ven Te Chow; McGraw-Hill Book Company 1959.

14. Handbook of Hydraulics - For the Solution of Hydraulic Engineering Problems by Ernest F. Brater and Horace Williams King; McGraw-Hill Book Company, Sixth Edition.

15. Safety of Existing Dams-Evaluation and Improvement; National Academy Press 1983.

16. Evaluation Procedures for Hydraulics Safety of Dams; ASCE.

Wheatland Reservoir No.2 References Page 2

17. Compilation of Records of Surface Waters of the United States Through September 1950, Geological Survey Water-Supply Paper 1310.

18. Compilation of Records of Surface Waters of the United States, October 1950 to September 1960, Geological Survey Water-Supply Paper 1730.

19. Surface Water Supply of the United States 1961-65, Geological Survey Water-Supply Paper 1918.

20. Surface Water Supply of the United States 1966-70, Geological Survey Water-Supply Paper 2118.

21. The Missouri River Basin Comprehensive Framework Study - Infiltration Data, October 1966.

22. National Inspection of Dams, Hydrologic Analysis Program Army Corps of Engineers, 1978.

23. NWS Breach Program, July 1988, Version.

24. HEC-1 Program, Army Corps of Engineers, Most Recent Version.

25. USGS Topographic Wyoming Quadrangle Maps - 7.5 Minute Series, Most Recent Version including: Dodge Ranch, Bull Camp Peak, Bluegrass Wells, McGill Lakes, Ayres Springs, Moonshine Peak, Squaw Rock, Reese Mountain, Hightower SW, Hightower, Wheatland.

APPENDIX A - FLOOD ROUTING CROSS SECTIONS

25% PMF

Cross-Sections

6990

6980

~6970 ~ (J)

~6960 c o

. - 6950 -+-' o >

CROSS SECTION 1183.32 Loramie River

1/4 PMF

00000 No Dam (6943.3) o 0 0 0 0 With Dam, No Failure (6937.5) I I I I I With Dam Failure (6939.0)

Q) 6940 UJ ~--------------~~~--~~~~----------------~~

6930

6920~~~-~1~11~1~1~1~11~1~1~1~11~I~I~I~II~II~I~I~I~II~I~I~I~I~II~I~I~I~II~I~I~I~I~II~I~I~I~II~I~I~I~I~II~I~I~I~II~I~I~I~I~II

0.00 1 000.00 2000.00 3000.00 4000.00 5000.00 6000.00 7000.00

SteJtiorl, In F--c(~t, r~ronr, L __ eft BOtll-<

6970

6960

~

~ 6950

2 '--.../

C 6940 o

--t-J

o > 6930 Q)

W

CROSS SECTION 1181.32 Laramie River

1/4 PMF

6920 0 0 0 DoNo Dam (6940.5) o 0 0 0 o With Dam, No Failure (6933.7) I I I I I With Dam Failure (6935.7)

6 9 1 0 -----t--.--,---r--r-.-r--.-, -'-1 ---'-1 -rl ~I---'Ir-.--I '--1 IT 1 1 1 I 1 1 1 I 1 1 1 1 I I 1 I 1 I I 1 1 I I I I I I I 1 I 1 1 I

0.00 1 000.00 2000.00 3000.00 4000.00 5000.00

S tot i 0 rl , I r-l F-- e e t , F r- 0 ron L_ eft B a tl ~<

6970

6960

~


1/4 PMF

uS 6950

:2 '-......-/

C 6940 o

--f-J

o > 6930~------------------------~----~--~--~~~-+ CD

W

6920 00000 No Dam (6936.0) o 0 000 With Dam, No Failure (6927.9) +-+ I I I With Dam Failure (6930.3)

6 9 1 0 -+-r--...--.--~-.--.----.--.--....---.---r--'----'---'--'---r--r-T--rTI I I I I I I I I I I I 1----rT I I I I I I I I I I I I I I I I I I I I I I I

0.00 500.00 1 000.00 1500.00 2000.00 2500.00 3000.00

~;totior-l, Ir-) f~~-eet, I=-r-or-n L_eft BOrl~~

6970

6960

6950.

C 6930 o

+-l

o 6920 > (})

W 6910


1/4 PMF

6900 000 DoNo Dam (6920.8) o 0 0 00 With Dam, .No Failure (6912.1) I I I I I With Dam Failure (6914.6)

6 8 9 0 --+---'I-r--I -r--r-I -r-I ---'-1 --'-1 ---'-1---'-1---'1 ~~I ~I ~I ~I 11---1'1 1 1 1 1 1 1 1 1 1 1 1 TI 1 1 1 1 1 I 1 I I I I

0.00 400.00 800.00 1200.00 1600.00

~) tot i C) r-) , I rl f~ (; e t , f=- r- C) rn ~_ E~ f t Ball ~<

I I I I I 2000.00

7000

6980

~6960 ~ (J)

2 '--../6940

c o

· - 6920 -+--' o >


1/4 PMF

~6900~----~----~--~----~~~~----~~~--~ W

6880 G-B-B--a-fl No Dam (6904.8) o 0 000 With Dam, No Failure (6900.3) I I I I t With Dam Failure (6900.5)

6 8 6 0 --t-r-----y---,----.---r---.---.----~11r__r1----.1----.-1-,-1 -'--1 -'-1 -'-1 -'---1 "---1 .-, "----'1 r-rl 1 1 1 1 1 , 1 I 1 1 1 1 1 1 1 , 1 1 1 1 1 1 I I I I I I 1 I I I I I I I 0.00 500.00 1 000.00 1500.00 2000.00 2500.00 3000.00

~) t (J tiC) rl ) I rl I~ C~ e t ) F-- r~ 0 I'll 1 ___ eft Bon k

6940

6920

~6900 ~ (f)

~6880 c o

. - 6860 ~

o > Q) 6840

W

6820


1/4 PMF

00000 No Dam (6838.7) o 0 0 0 ~ With Dam, No Failure (6835.6) 1 1 1 l-t- With Dam Failure (6835.7)

6 8 0 0 -t--r-r-r-r--lr-r-T---'I"-'-I -'-'1 I-r--I -'-----'1 ITTTTTT1-n-TTI I I I I II I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I 0.00 200.00 400.00 GC)().OO 800.00 1000.00 1200.00 1400.00 1600.00

S t CJ t i () r) , I ri r=- (~ E~ t , I~ r 0 tl/l L_ eft [3 0 n I~

6650

6600

~

~ 6550

:2 ~

C 6500 o ~

o > 6450 ())

W

6400


1/4 PMF

~--------~--~~~~--~~-------~o------~o

G-e-a-&-fl No Dam (6426.1) o 0 0 0 0 With Dam, No Failure (6420.5) I I I I I With Darn FClilure (6420.8)

6350 I I I I II I TrTTT1T I I I I I I I I I I II I I I I I I I I II I I I I I I I I II I I I , , , I , I' , I' , , I , I I 0.00 100.00 200.00 300.00 400.00 500.00 600.00 700.00 800.00

~; tot i () rl , I r-) r- (~ (~ t , r-~ r- C) rYl l~ eft Bon ~<

5550

5500

~

~ 5450

:2 ~

C 5400 o

+--" o


1/4 PMF

> 5350 -+------~-~~~~-____:~-~-~~---_4t CD

W

5300 G--B--8-B-fl No Dam (5353.9) ~-++~ With Dam, No Failure (5349.7) 1 1 1 1--+ With Dam Fa ilu re (5349.8)

5 2 5 0 ~--..---..----.----r---.--~~~~--I~I ~I ~I l----r-r I I I I I I I I I I I I I I I I I I I I I I I I I I I I I 0.00 200.00 400.00 600.00 800.00 1 000.00

S tot i () rl , I n r-~ (~ (; t , Fro rl~1 l __ eft Bon ~<

4790

4780

~4770 ~

en 2S4760

c o

. - 4750 -+--' o > Q) 4740

W

4730


1/4 PMF

00000 No Dam (4741.6) o 0 0 0 0 With Dam, No Failure (4740.4) I I I I t With Dam Failure (4740.5)

4720 I I I I I I I I I I III I I 111-, I I I I I I I I I I I I I I I I I I I I I I I I I I I I I 0.00 1000.00 2000.00 3000.00 4000.00 5000.00

S t Cl tiC) r-) I r) r~- e t) t F r~ 0 Ilr-1 L_ eft Bon 1< -~~~ - , ./-,

4580

4560

~

~ 4540

2 '---.../

C 4520 o

-+-.J

o > 4500 CD

W

4480

CROSS SECTION 1 1 21 .1 4 Loramie River

1/4 PMF

o 0 0 0 f) No Dam (4494.3) ~~~ With Dam, No Failure (4491.7) -t-f-t-t-+ With Dam Failure (4491.8)

4460 I I I I I I I I I I I I I I I I I I I TJlllrTT I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I 0.00 500.00 1 000.00 1500.00 2000.00 2500.00 3000.00 3500.00

S t CJ t I () rl , I rl ~ ~- (~ c? t , r=- r- C) rr'-I L~ t? f t B C1 n ~<

50% PMF

Cross-Sections

6990

6980

~6970 ~ (f)

2S6960

c o

. - 6950 ~

o > CD 6940

W

6930


1/2 PMF

OBBBO No Dam (6947.1) 00000 With Dam, No Failure (6939.5) I I I I I With Dam Failure (6939.5)

o 0

• •

6920 I I I I I I I I I rTTTTTTTTTTTTI-r,-nl'l I I I I I I TTTlI I I I I I I I I rl I I I I I I I I I I I I I I I I I I I 0.00 1000.00 2000.00 jOOO.OO 400().()0 5000.00 6000.00 7000.00

S t (J t- i () r) , I rl f - (~(=~; l , F- r- C) 1/ 1'-) 1_ (~ f LBo tl 1<

6970

6960

~

~ 6950

2 '----/

C 6940 o

+---' o > 6930 Q)

W

CROSS SECTION 1181 .32 Laramie River

1/2 PMF

6920 G-a-a-a-fl No Dam (6945.2) o 0 000 With Dam, No Failure (6936.1) I I I I I With Dam Failure (6936.1)

69 1 0 --+--r----'----'---'-·-----r-I 1 I I I 1 1 I 1 1,-. 1 I I 1 I I I I I I I I I I I I I 1 1 1 1 1 I I I 1 1 1 1 I 1 I 0.00 1000.00 2000.00 3000.00 4000.00 5000.00

S lot i () n , I n r- (=? e l , Fro r--r) L_ eft Ball I~

6970

6960

~

~ 6950

2

C 6940 o

-f----I

o


1/2 PMF

> 6930~----------------------~~----~--~--~~~~ Q)

W

6920' 0 0 0 DoN 0 Dam ( 694 1 .8) o 0 000 With Dam, No Failure (6930.6) I I I I I With Dam Failure (6930.7)

691 0 I I I I I I I I I I I I I I I I I I I I I I I 1 I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I 0.00 500.00 1000.00 1500.00 2000.00 2500.00 3000.00

S t (J t i 0 rl , I rl r~- (; e t , F r C) t~ll l ___ eft Bon l-<

6970

6960

6950 ~

~

~ 6940 ~

c 6930


1/2 PMF

o ~--------~----~--~------------~--~~~~

-f--l

o 6920 > Q)

W 6910

6900 0 0 0 DoNo Dam (6927.0) <) 0 0 O~ With Dam, No Failure (6915.0) I I I I I With Dam Failure (6915.1)

6 8 9 0 -t---.--.--r--r--r----.--r--,---,--,----y-----.--.------.--.,----,---,- I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I

0.00 400.00 800.00 1200.00 1600.00 2000.00

S tot i C) n , I rl r~-eel , r~ r- 0 rrl 1_ eft Bon ~<

7000

6980

~6960 ~ (J)

2S6940

c o

· - 6920 +--J

o > Q) 6900

W

6880


1/2 PMF

00000 No Dam (6911.1) o 0 0 0 0 With Dam, No Failure (6908.2) +-+-i-t-+ With Dam Failure (6908.6)

6860~~~~~~~1 1~1~1~1~1~1~1~1·lnnn I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I 0.00 500.00 1 000.00 1 500.00 2000.00 2500.00 3000.00

:) t CJ t i () r) , I r) r-e e t , F t~ 0 t'n L_ eft B C1 n ~<

6940

6920

~6900 ~ (J)

2S6880

c o . - 6860

--t--J

o >


1/2 PMF

~6840-~------------~~~~--~--~~--~~------~~ W

6820 G-a-B-&-f1 No Dam (6843.5) ~+h) With Dam, No Failure (6841 .2) I I I I I With Dam Failure (6841.5)

6 8 0 0 --t--r-r-r-r-.--r-r-.--r-r-..---r---r-T-r--.---r-r--.---r-r--'--'-TTT-nT I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I 0.00 200.00 400.00 600.00 800.00 1000.00 1200.00 1400.00 1 600.00

Stclti(jn, Ir-) F-cet, FrOtll '-_eft Bon~<

6650

6600

~

~ 6550

2 ~

C 6500 o

-f-J

o > 6450 CD

W

6400


1/2 PMF

G-a-&-B-£J No Dam (6434.7) ~ 0 0 0 0 With Dam, No Failure (6430.2) +-1 1 1 1 With Dam Failure (6430.8)

6 3 5 0 -+---r-,.-----y-r--.---r--r----r-r--r-r-r-r---"-n,n I I I I I I I n-lITT-' I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I 0.00 1 00.00 200.00 300.00 400.00 500.00 600.00 700.00 800.00

StCJtiOrl, In r-ect, F:-I~orn Left Bonk

5550

5500

~

~ 5450

:2 '-.....-/

C 5400 o

+-J

o > 5350 Q)

W

5300

5250 I

0.00 I I


1/2 PMF

00000 No Dam (5358.5) o 0 0 0 () With Dam, No Failure (5356.4) I I I I I With Dam Failure (5356.6)

I I I I I I I I I IT I I l-.-r I I I I I I I I I I I I

200.00 400.00 600.00

S t CJ t- i (j rl , I r~) F- (J (:J t ,-j./ , F ro til

I I I I I I I I I I I I I I I I 800.00 1 000.00

Lef l Bon~<

4790

4780

c o

. - 4750 -t-J

o > Q) 4740

W

4730


1/2 PMF

DODO£] No Dam (4743.9) o 0 0 0 0 With Dam, No Failure (4742.9) t-t-t-t-t With Dam Failure (4743.0)

4 7 2 0 --+--'-~'---'---'--Y--I -'---1 -'--1 -'-1 -'--1 -'-1 ---'-1-------'-1 ~I~I I I I I ,I I I I I I I I I 1 I I I I I I I I I 1 I I I I I I I I I

0.00 1 000.00 2000.00 3000.00 4000.00 5000.00

S t CJ t i 0 r-) , I r-) F- e (~ t , F r- 0 t~rl L eft B 0 tl 1<

4580

4560

~

~ 4540

2 '--.--/

c 4520 o ~

o > 4500

CROSS SECTION 11 21 .14 Loramie River

1/2 PMF

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

W

4480 &-0000 No Dam (4497.6) 00000 With Dam, No Failure (4495.9) -t--t---t--t-+ Wit h Dam F a i I u r e (449 6. 1 )

4460 - I I I I I I I I I I I I I I I I I I Iflll,-T-rl I I I I I I I I I I I I I I I I I I I I I Iii I I I I I I I I I I I I I I I I I I I 0.00 500.00 1000.00 1500.00 2000.00 2500.00 3000.00 3500.00

~; t CJ t i () rl , I rl r-~ c? e t , F-- r C) t~ll l~ __ eft Bon I~<

FULL PMF

Cross-Sections

6990

6980

~6970 --.J (J)

2S6960

c o

. - 6950


Full PMF

00000 No Dam (6952.0) o 0 000 With Dam, No Failure (6948.4) I I I I I With Dam Failure (6948.2)

~ ~==============~~====~~~~================~~

o > Q) 6940

W

6930

6 9 20 - -, I I I I I I r I I I I I I TTII------rr-n-1-r-r-1Tl I I I I I I I I I TTfI I I I I nI I I I I I I I I I I I I I I I I I I I I I I

0.00 1 000.00 2000.00 30GO.GO 4000.00 5000.00 6000.00 7000.00

c~ t (J t i () t/-l , I r--I r -(_~ E~ t , r~ t~ 0 I'll l_ t~ r t B 0 tl 1-<

6970

6960

~

~ 6950

2 "---../

C 6940 o

--+---' o > 6930 Q)

W

CROSS SECTION 1181 .32 Loramie River

Full PMF

6920 0 0 0 O-t1 No Dam (6950.7) ~-+-H> With Dam, No Failure (6946.5) +-1 1 I t- With Dam Foilure (6946.3)

6 9 1 0 -'-1 -'-1 --'---'-1 -'-1---'-1----'1---'1"----'-1 IT-IT-T~r -r-T --,_nl,-r-T I I I I -. I I I I I I I I .1 I I I I I I I

0.00 1 000.00 :~OOO.OO 3000.00 4000.00

=~) l c] tiC) rl ) I r~ I 1- -- C~:i (~ t , ,=- r- 0 r-rl L_ (~ f t [3 0 n I~<

I I I I I 5000.00

6970

6960

~


Full PMF

~6950~ __________ ~ __________ ~ ________ ~~ __ ~ __ ~~

2 '-......-/

C 6940 o

--f-----I

o > 6930 Q)

W

6920 GOOD£] No Dam (6949.2) (rl~ With Dam, No Failure (6943.6) +-+-t-t--+ With Dam Failure (694:5.4)

69 1 0 - I I I I I lI'jll-r-Ti-rniT-rrT-r I I I I I I I I I I I I I I ITT I I I I I I I I I I I I I I I I I I I 0.00 500.00 1000.00 1500.00 20C)0.C)O 2500.00 3000.00

S t (] t I (j rl , I r 1 I~ C~ (~l t , 1-- r- C) r-ll l __ ~ e f l E30 tll<

6970

6960

6950


Full PMF

c 6930 ~----~-~,---~------------'l~-.{jJ----.4l-+-4f-~ o

-t-J

o 6920 > Q)

W 6910

6900 0 0 0 DoNo Dam (6935.5) o 0 0 0 0 With Dam, No Failure (6928.7) -t-1-t-t-t With Dorn Failure (6928.6)

6 89 0 --TI 1 1 r,-,I 1 I 1 -'--1 -'------'---1 11I--r--l-fII---rT 1 1 1 1 1 I 1 1 1 1 1 1 1 1 1 I I I I 1

0.00 400.00 800.00 1200.00 1600.00

c) t (Jt i () r-l , I r~ l r --- (~ (:: t , F r-- () r II I (~f t f3 0 n 1<

1 1 1 I I 2000.00

7000

6980

~6960 ~ (J)

~6940


Full PMF

c o

6- 6920 J======9~====~==~======~~~======~4=~====4 -+-' o > Q) 6900

W

6880 [J--a-e--a--f) NoD a m ( 6 9 1 9. 1 ) O-~-~ With Darn, No Failure (6918.6) +--+-+--t-t With Darn Failure (6918.7)

6860 --+---r---.---.--.---.---y--y--,~----...---r--'--T I I I I Tl--rr-T~I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I 0.00 500.00 10C)O.OO 1500.00 2000.00 2500.00 3000.00

c~ l (J L i () r--l , I rl ,-- C,) (~t , r~- r- () rr-) 1 ___ eft 13 a rll<

6940

6920

~6900 ~

Ul

2S6880

c o

. - 6860 -+--' o > CD 6840

W

6820

CROSS SECTION 11 70.32 Laramie River

Full PMF

G 0 0 DoN 0 Darn ( 6850 . 0 ) <t-~-~-() With Dam, No Failure (6849.6) + I 1 1-+ With DarTl Failure (6849.7)

6800 _. I I I I I niTTTlI-TTTTTTTTTT-rT-rrTTTT-n-TTTrTT1' I I I 1ITrT1TTTTTTTri I I I I I I I I I I I I I I I I I I I I I 0.00 200.00 400.00 600.00 800.00 -1000.00 '1200.00 1 400.00 1 600.00

r~ t- (J l i () r-) , I r) r~ (~ (~ l , l~ r- () ,-r, 1 __ (~ f l Bon 1<

6650

6600

~

~ 6550

2 "----/

C 6500 o ~

o


Full PMF

> 6450 ~ ~------------~--~~.------.~--~------.-----------~

W

6400 G-B-B-B-fl No Dam (6446.0) o-+~(; With Dam, No Failure (6445.3) +-t-t-t-+ Wit h Dam r:- CJ i I u r e (644 5 . 5 )

6350 "'" ,TTl I I , , rrrrli[lT-r-n-T-r-rrrrrrr-'TTTlT,r,r-n--.rlfli'ifTTl-1 I ' , , I I I I I I I I I , , I , , I I I

0.00 1 00.00 200.00 j(jO.OO 400.00 5C)0.OO 600.00 700.00 800.00

~) t (J t i () rl , I rl ,- C; c L , F r- 0 r-ll L_ eft B a tl ~<

5550

5500

~

~ 5450

2

C .5400 o

-+--' o > 5350 Q)

W

5300

-:ROSS SECTION 11 49.90 Laramie River

Full PMF

G-&-£-a-tJ No Dam (5365.3) Ct-O 0 0 0 With Dam, No Failure (5364.9) +-t-+-t-t With Dam Foilure (5365.0)

5250 I I I I I I I I I I I I~~II-IT I I I I I I I I I I I-r-I I I I I I I I I I ' , I I

0.00 200.00 400.00 600.00 800.00

:) t CJ t i 0 r--l , I r~) r~- (~? E~~ t , F r~ 0 Il'~-) L __ eft Bon ~<

I I I I 1 000.00

4790

4780

~4770 ---.J (f)

~4760 c o . - 4750

+--' o > Q) 4740

W

4730


Full PMF

G-B-e--&-t] No Dam (4747.0) ~-++--tJ With Dam, No Failure (4746.8) +--+--t-t-t With Dam Failure (4746.8)

4 7 2 0 -- I I I T-I~ I I I ---r-T--r--rr--.---rTT---r-1 I I I I I I I I I I I I I I I I I I I I I I I I I I I 0.00 1000.00 2000.00 3000.00 4000.00 5000.00

~~t (J t i () r--) , I r-) r -(~ (; t , f-- r~ C) r~n l ___ t~ f t BOil 1<

4580

4560

~

~ 4540

2

c 4520 o

-+---.l

o > 4500 Q)

W

4480

CROSS SECTION 11 21 .14 Loramie River

Full PMF

G-H-B-EHJ No Dam (4501 .8) ~-~ With Dam, No Failure (4501.5) +-111 t With Dam Failure (4501.5)

4460 - -TTl I I I 1-rTT,-1-rTl-rll-1TT-rTl,-TTTTTTTl I I I I I I T-rTTT,-TTT'I I I I I I I I I I I I I I I I I I I I I 0.00 500.00 1000.00 1500.00 2000.00 2500.00 3000.00 3500.00

(:; l (J t i () r-) , I r 1 I (? C~~ t , r=-- r- C) I'll L __ eft B 0 t'll<

APPENDIX B - WYOMING DAM INSPECTION REPORT

WYOMING DAM INSPECTION REPORT

Name of Dam Wheatland Reservoir No.2 Date July 21, 1989

Permit No. 1724 Water Division Number 1 District # 4 ------------------------------ ----- ~-----

county: _____ A_l_b __ an~y ______________________ Location: ~ Section, EtC.:~NW ______________ _

Section ______ 3_1 _____________ Township ____ 2_2_N _____________ Range ____ 7_3W ______________ __

Earthfill Type of Dam (circle) EARTHFILL, ROCKFILL, CONCBETE, OTHER ---------------------------Estimate Actual Capacity: Actual Capacity:

-----------------------98,934

Estimate Height: Actual Height: 37' --------------------------------Estimated Level @ Elevation 6945 Ma·in - 62.1'

Waterlevel - 2&&1tx.i:.imoe~dmQ~ga={}ag~~ ___ Estimate Spillway width: Aux. - 39.8 (Circle which one) or Emergency spillway ___ __ Estimate Freeboard (Spillway to Top of Dam): 7.5' top of spillway gates to crest

Use: IRRIGATION, MUNICIPAL, (circle), OTHER, (specify) Irrigation

Fill in all blanks, if unknown - enter unknown; or not applicable - enter N/A; if none - enter none.

DIRECTIONS: Mark an "X" in the Yes or No column and circle the word or phrase which applies.

Yes No .. 1. Are the roads to the dam adequate to allow ACCESS BY EMERGENCY

EQUIPMENT and TRAVEL ACROSS THE DAM (i.e., TP.UCKS, Ai.\1BULk."lCES)? X

2. Is there DEBRIS, TREES, or BROSH on the upstream slope that prevent seeing the entire surface of the slope? X

3. Are there TREES or~on the CREST, or DOWNSTREA}l SLOPE that prevent seeing the entire surface? X

4. Are there CRACKS , SLIDES ,(["LUMP]) BQII.S. SETTLEl-lENT or OTHER on the UPSTREAM SLOPE, CREST, ~WNSTREAM SLOEFA MII.Jol( X

S·. Are there~ENT HOLE~Or ERODED GULLIES on the UPSTREAM or ltX5WNSTREAM SL01't!7 X

6. Is the upstream slope eroded from wave action? X

7. Is there FLOWING WATER or~GE BOGGY SPOT])at the toe of the dam? X

8. Are there FLOWS OF WATER or WET SPOTS above the toe of the dam? X

9. Is the riprap~ISPI.AciE)or BROKEN DOWN or@SSINGoV MINlJlI X

10. Are there toe drains? X

11. Is the water from the TOE DRAINS or LEAKS found to be MUDDY or SANDY? X

12. Are any of the concrete portions excessively~RACKEtDor(§?ALL~ X

13. Is the OUTLET CONTROL or GATE found to be STUCK, BROKEN, or EXCESSIVELY CORRODED? X

OVER

Yes No 14. Is the outlet control easy to get to? X

15. Is released water UNDERCUTTING THE OUTLET or ERODING THE EMBA.L~KMENT? X

16. outtet & main spillway

Does the spi±±~ channel show significant{EROSIoN) BACK-CUTTING or DETERIORATION? X

17. Is the spillway obstructed with FLASHBOARDS, TREES, DEBRIS, BRUSH or OTHER? X

18. Is there evidence that the dam has been overtopped? X

19. Ar~§~illway WALLS, lfLoofD CONTROL SECTION, and ENERGY DIS-SIPATOR in POOR condition? X

20. Is the outlet pipe BLOCKED, or EXCESSIVELY CORRODED or OTHER? X

21. Is the reservoir usually full YEAR ROUND, OVER ~ OF YEAR, or asss THAN .. ~ OF YEA~

22. Should this dam be promptly inspected by a field engineer? X

23. Are photographs to be forwarded to Headquarter's Office? X

24. Additional Comments:

Refer to the study to which this is attached, particularly Chapters 7 and 8, for a

detailed description of the facilities and the findings of the inspection. Also,

a video tape made and photographs taken during the inspection are available at the

office of Banner Associates, Inc. in Laramie, Wyoming.

Inspection team: Frosty Kepler, PE, BAI Tim Conner, PE, BAI Sig Zvejnieks, PE, BAI Clyde Smith, PE, BAI Terry Arnold, PE, Woodward-Clyde Consultants Jim Obermeyer, PE, Wood-ward Clyde Consultants David Benner, PE, SEO-Dam Safety Mike Carnevale, Project Manager, WWDC Bud Nichols, Dam Caretaker, Wheatland Irrigatin District

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