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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the estimated cost for Option B would also be approximately $2,000,000.00.

Option C - Rotary Drum Screens

General

This option involves constructing a screen structure with cylindrical rotary drum type screens in

a single line. This arrangement is shown on Figure 5. Photos 8 and 9 in Appendix A show

examples of this type of screen. The structure will consist of a concrete slab on grade with

concrete walls and drum screens separated by concrete piers. The structure invert in front of the

screens is at E1.4672.6. The base of the drum screens are set at El. 4673.6, one foot above the

invert. This will provide a one foot depth to allow for silt deposition. The minimum design

depth on the screens is at El. 4679.6, which gives a minimum six feet depth of flow on the

screens. The drum diameter is selected such that the six feet depth of water will result in a depth

on the drum that is 0.75 times the drum diameter. An eight feet drum diameter will meet this

requirement. To determine the number of drums required, the net area of the drum is calculated.

Sheet 7 in Appendix C is used to estimate the net area to then calculate the required screen size

for an approach velocity of 0.5 fps. Assuming 8 feet diameter drums, 16 feet long, the overall

factor from Sheet 7 will be 0.343. If 15 drums are used, the allowable design flow will be 8.0' x

16' x 15 screens x 0.343 = 659 cfs, which is slightly more than the design flow of 640 cfs.

Rotary drum screens are cleaned of debris by a slow rotation of the drum that lifts debris attached

to the drum over to the downstream side where it is carried offby the canal flow. The rotation of

each drum is powered by a small electric motor. An access platform is also provided on the

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