9380

• UCREFRP Catalog Number: 9380
• Author: U.S. Bureau of Reclamation.
• Title: Grand Valley Irrigation Company Fish Screens ‎(Predesign)‎.
• USFW Year: 2000.
• USFW - Doc Type: Boise.
• Copyright Material: NO

elevation ofEl. 4679.6 can be maintained by opening the six headgates to 84 or 89 percent open.

If this condition is not acceptable, the alternatives may include raising the water surface elevation

above the headworks or reducing the head losses. It appears raising the water surface elevation

would involve capping or raising the crest of the diversion dam. This may have detrimental

impacts on previous fish passage design work at the dam. The other option, reducing head

losses, may be accomplished by adding another gate to the headworks. Design data information

indiCates that the existing headworks structure has a space provided for adding a seventh gate.

Sheet 5 in Appendix C shows the results of head loss calculations assuming 7 gates. For a 1.2

feet head loss, Sheet 5 shows the required gate opening to be 72 to 76 percentopen.

GeoloC'
Two drill holes in the vicinity of the fishscreen structure were drilled. The location of the holes

are shown on the Site Plan, Figure 2 in Appendix B. The drill logs from the two holes, as well

as, a brief description of the geology at the site are shown in Appendix D. The data shows the

foundation and excavation for the structure and bypass pipe to be in an alluvial material

composed of silt, sand, gravel, and cobbles. The depth to bedrock was found to be

approximately 16.0 feet. All excavations would be anticipated to be in common materials. Rock

excavation or blasting is not anticipated to be required. Temporary excavated slopes will be

assumed to be at 1: 1, and permanent slopes at 2: 1.

Depth to water levels in the two drill holes were recorded. The elevation of the water level was

approximately El. 4679.8:1:. The bottom of the fishscreen structure is approximately El. 4671.6,
10

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