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

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Bypass Desi2n Alternatives

The following two bypass alternatives are for consideration with screen options A through D.

Screen Option E does not require a bypass pipe.

Alternative 1.

General

Alternative 1 involves the standard bypass design used by the PN Region. The angle of the

screens to the line of flow was set at 14 degrees for all screen options. The depth of flow on the

screens was also set at 6 feet. Sheet 8 in Appendix C shows a spreadsheet used to calculate the

bypass flow. The spreadsheet calculates the bypass flow such that the resulting velocity in the

full depth bypass slot will be 1.5 times the velocity in the fishscreen structure upstream from the

screens. Sheet 8 shows this condition will be meet with a 30 inch wide bypass slot and a 44 cfs

bypass flow. It is also desirable to have the bypass flow be a certain percentage of the design

flow through the screens. Sheet 9 in Appendix C shows typical bypass flows as a percentage of

screen flows from past designs. A 44 cfs bypass flow would be about 7 percent of the 640 cfs

screen flow, which is appropriate.

The 44 cfs bypass flow is maintained by proper bypass pipe design and by discharging the

bypass flow over a ramp weir in the bypass slot. The ramp weir is an adjustable crest weir that

provides a slight acceleration of flow to sweep fish and debris over the weir and into a downwell

and eventually into the bypass pipe and then back to the river. Typical drawings of the ramp

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