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I I I I I I 1 I I I I I I I I I 1 I, I design flow of 640 cfs, the elevation at the staff gage is El. 4679.61. Therefore, the water surface elevation used for the sizing of the screens at the design flow of 640 cfs will be El. 4679.6. Water surface elevations from above the headworks and extending down the canal to the staff gage were obtained by WCAO-ND on October 15, 1999. The flow in the canal at this time was 620 cfs. The following is the water surface survey data results: El. 4681.37 - Upstream side of the floating trashrack (south end). El. 4681.26 - Downstream side of the floating trashrack (south end). El. 4679.67 - 15 feet downstream of head works. El. 4679.39 - Staff gage. The data shows a 0.11 feet head loss across the floating trashrack (El. 4681.3 7 - El. 4681.26), and a 1.59 feet loss at the headworks (El. 4681.26 - El. 4679.67). The headworks are reported to consist of 6 gates with each gate opening approximately 5.4 feet wide by 4.5 feet tall. Sheet 3 in Appendix C shows the results of head loss calculations based on the standard orifice equation. The results show that for a flow of 620 cfs through the headgates with a 1.59 feet loss, the gates are approximately 70 percent open. Additional losses in the system will include losses through the trashrack and through the screens. Typically because of the low velocities through the system, these additional headlosses are minimal. Trashrack losses can be estimated by the following formula from Reclamation's Design Standard No.2, Canals and Related Structures, Chapter 2, Figure 15: 7