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Temple Fork Dam

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Team Members 

  • John Sumsion
  • Riley Manwaring
  • Kendall Maedgen
  • Adam Pack
  • Taylor Kesler
  • Logan Thackeray 

Photo Credited to Dr. Bethany Neilson

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Client and Advisors 

  • Client:

Nathan Daugs

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  • External PE:

Dr. Loren Anderson, PE

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  • Additional PE:

Rick Riker, PE

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  • Faculty Advisor:

Dr. Bethany Neilson

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Background

  • The population of Cache County is expected to increase by 93% between the years 2015 and 2065 (Perlich, 2017).

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  • According to the Cache Water District, an additional 90,500 acre-ft of water storage is required.

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  • Cache Water District will consider multiple sites.

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Bear River Development Report

  • Originally proposed a 327-ft roller-compacted concrete dam (RCC)
  • 41,350 acre-ft of storage
  • CWD requested a 10,000 acre-ft reservoir at this location

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Design Criteria

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  • Hydrologic and hydraulic considerations
    • Storage of 5,000 to 10,000 acre-ft 
    • (optimally 10,000)
  • Environmental impact
    • Location of dam relative to Spawn Creek
  • Size of the structure (footprint)
  • Recreation potential of reservoir
  • Risk of failure to downstream residents

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Alternatives Considered

  • Site A: The same site explored by the Bear River Development Report
    • High environmental impact
    • Able to store 10,000 acre-ft

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Alternatives Considered

  • Site B: Approximately a mile up from Site A
    • Lower environmental impact
    • Able to store ~7500 acre-ft

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Alternatives Considered

  • Two Dam Alternative: Two smaller dams constructed at Sites A and B
    • High environmental impact
    • Able to store 10,000 acre-ft, by storing 5,000 acre-ft at each location

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Evaluation of Alternatives

Alternative

Total�Score

Do-Nothing

3.7

Two dam

2.6

RCC - Site A

3.3

Earth - Site A

3.3

RCC - Site B

2.8

Earth - Site B

2.8

0: Not Preferred

5: Preferred

Criteria

Weight

Environmental Impact

30%

Dam Size

15%

Recreation Potential

10%

Risk to Downstream Residents

20%

Reservoir Capacity

25%

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Recommended Alternative:�RCC Dam at Site A

Storage Volume: 10,000 ac-ft

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Surface Area: 150 acres

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Crest Height: 230 ft

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Hydrologic Calculations

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Hydrologic Calculations

  • Based on data from 1954-2020 (USGS gaging site 10109000)
  • Assuming a loss to groundwater of 5-15%
    • Loss to groundwater needs in-depth investigation
  • Additional water is needed to fill the reservoir

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Average Annual Reservoir Water Balance

Volume Accumulated in Reservoir�(acre-ft)

Required Dam Release �(acre-ft)

Loss to�Evaporation�(acre-ft)

Loss to Groundwater�(acre-ft)

Storage�(acre-ft)

13,500

9370

418

674-2020

1680-3020

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Hydraulic Design

  • Probable maximum flood (PMF): 8,600 cfs (HMR-49)
  • Stepped auxiliary spillway and stilling basin provide energy dissipation (FEMA-94)
  • Three 72-in. diameter pipes capable of passing 100-year flood and draining the reservoir within a week. (Utah Administrative Code R655-11)

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Geotechnical Considerations

https://pubs.usgs.gov/tm/04d02/pdf/TM4-D2-chap3.pdf 

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Geotechnical Considerations

  • Groundwater Pressure
    • Green – High
    • Blue – Low

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Grout curtain

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Structural Considerations

  • Factors of safety were calculated to ensure the dam is big enough to not slide or overturn when the reservoir is full
  • Three load cases were checked: average, flood, and seismic event
  • Data for the seismic case was insufficient, further seismic studies of the area are highly recommended

Average loading

Unusual loading

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Fish Passage

  • The Bonneville Cutthroat Trout are an important part of the ecosystem
  • Alternatives were considered to allow fish passage between Logan River and Spawn Creek
    • Smaller sized dams
    • The addition of a fish ladder (USFWS, 2017)
      • 1057 ft total length
      • 4 switch backs

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Cost Estimate

Temple Fork Reservoir

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Cost Item

Quantity

Unit

Unit Price

Total

Dam Facilities

Subtotal

$34,488,500

Clear and Grub Dam Footprint

140000

SF

$0.25

$35,000

Foundation/Abutment Overburden Excavation

120,000

CY

$6.00

$720,000

Foundation Grout Curtain

1

LS

$3,600,000.00

$3,600,000

Bedrock Foundation Prep / Dental Grout

1,000

CY

$200.00

$200,000

Roller Compacted Concrete Dam

300,000

CY

$80.00

$24,000,000

Dam Construction Dewatering & River Control

1

LS

$500,000.00

$500,000

Toe Drain & Drain Collection System

1

LS

$100,000.00

$100,000

Monitor Wells & Piezometers

8

EA

$20,000.00

$160,000

Spillway

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Concrete Work

1,300

CY

$800.00

$1,040,000

Plunge Pool Excavation

4,000

CY

$5.00

$20,000

Plunge Pool Riprap

1,100

CY

$35.00

$38,500

Outlet Works

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Inlet/Outlet Structure & Gates (on face of RCC)

1

LS

$1,900,000.00

$1,900,000

72" Pipe in RCC Dam

600

LF

$500.00

$300,000

Instrumentation & Controls

1

LS

$250,000.00

$250,000

Ancillary Facilities

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$0

Access Road & USFS Road Excavation

120,000

CY

$10.00

$1,200,000

Dam Access/County Roads Gravel Volumes

9,000

CY

$25.00

$225,000

Clear and Grub Reservoir Area

1

LS

$200,000.00

$200,000

Supply/Discharge Pipe

Subtotal

$2,169,000

Pipeline (PS to Dam)

2,325

LF

$520.00

$1,209,000

Flow Control Valve & Box to Temple Fork Creek

1

LS

$200,000.00

$200,000

Flow Meter Vault

1

LS

$170,000.00

$170,000

Control Valve Vault (to river)

1

LS

$440,000.00

$440,000

Energy Dissipation Structure to Logan River

1

LS

$150,000.00

$150,000

Supply Pump Station

Subtotal

$15,650,000

Site Work & Excavation

1

LS

$500,000.00

$500,000

Dewatering & River Control

1

LS

$550,000.00

$550,000

Intake/Pump Sump Structure & Control Building

1

LS

$850,000.00

$850,000

Screens & Rakes

1

LS

$375,000.00

$375,000

Pumps & Motors

1

LS

$2,750,000.00

$2,750,000

Mechanical, Valves & Piping

1

LS

$1,200,000.00

$1,200,000

Surge Protection Facilities

1

LS

$1,000,000.00

$1,000,000

Electrical & Controls

1

LS

$675,000.00

$675,000

RMP Impact Study

1

EA

$250,000.00

$250,000

RMP Substation

1

EA

$2,500,000.00

$2,500,000

Power Line

20

MI

$250,000.00

$5,000,000

Land Acquisition & Wetland Mitigation

Subtotal

$1,000,000

Leases, Easements, & Legal

1

LS

$450,000.00

$450,000

Wetland Mitigation Estimate

5.5

AC

$100,000.00

$550,000

Pump Station Power Cost

Subtotal

$1,000,000 

Fish Ladder 

Subtotal

$6,000,000

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TOTAL  

$60,307,500

  • Scaled-down version of Bear River Development Report
  • Cost of RCC for dam: $24 million
  • Total project cost: $60 million
  • Relocation of road not included.

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Overall Recommendations

  • From the data we have, a dam of this size at this location is plausible.
  • More site-specific research is needed in the following areas to determine overall feasibility and reduce uncertainty:
    • Water loss due to karst features or formation both underneath dam foundation and underneath reservoir.
    • Site investigation into existing faults/fractures to better understand current geologic conditions.
    • Dynamic seismic loading analysis. 
    • Amount of sediment transport likely to occur.
    • Re-routing existing road.
    • Aggregate sourcing.
    • Pumping water from Logan River

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Plan View:

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References