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'""" r- '0. l~ '~>~, :i'~I~ ~ C'~. 6. Pilot Knob Powerplant and Wasteway c The Pilot Knob Powerplant operated in January. a month in which the powerplant is normally off-line, due to anticipatory releases from reservoirs on the Colorado River. Operations during the remainder of the year were normal. Water was transferred from the Yuma Project to the Pilot Knob Powerplant under provisions of Contract No. 14-07-300-1381 (Contract for Temporary Use of Water for the Generation of Electric Power and Energy). See Table No.1 for monthly and annual quantities of water. Repairs were required on a portion of the floor of the Pilot Knob Wasteway as steel reinforcement bars in the concrete flood channel were exposed and rusting. 7, Hydrography The schedule for metering flow in the All-American Canal is 2 times per week at Station 60 and Station 1117 with the District's hydrographers alternating with U.S. Geological Survey (USGS) hydrographers. One measurement is made each week in the forebay of Pilot Knob Powerplant by the District's hydrographers again alternating with USGS hydrographers. Additional measurements are taken at other times as deemed necessary. The flow through Pilot Knob Powerplant is computed by District and USGS personnel from values indicated by the head method from wicket gate settings because gears in the turbine flowmeter failed in 1980. Current meter measurements are made once each week in the forebay when the Pilot Knob Powerplant is operating. Adjustments in the computed flow are made as required. The District provides the USGS representative at Yuma with a log of the midnight readings obtained from the wicket gate settings. Also provided are the discharge measurements made by the District, the forebay recorder graph, and if required, the tailrace recorder graph and a record of wicket gate openings. The record of flows computed by the District is considered as provisional and is published as such by the USGS. 8. Sediment Determinations The District forces take sediment samples once each month with a D-49 sampler at Station 60 and at Pilot Knob Powerplant forebay. Sediment samples of the sludge discharge from the All-American Canal Desilting Basins are also taken once each month with a special vacuum. The results are shown on Table Nos. 4 and 5 of this report. A complete sediment sampling program for Imperial Dam and the All-American Canal system is shown on Table No.3. 9. Cathodic Protection The impressed current cathodic protection system installed on the desilting works and headworks which are operated by Imperial Irrigation District has been in operation continuously throughout the 9