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" '1 ,- '..... ;jJr-' ') . . '. .J oJ- METROPOLITAN WATER VISTlllCT viding maximum efficiency in the various lines. High flows in the Palos Verdes feeder caused entrapment of air in the line near the northerly end, thereby creating line surges. Two new vacuum valves and two larger air release valves were installed south of Eagle Rock tower to alleviate this condition. The Orange County feeder was operated under full flow to determine the maximum capacity and to establish a time schedule for increasing flows to prevent waste of water at the various surge chambers in the line. Delivery of water to the San Diego aqueduct continued at a high rate during the lirst half of the liscal year with flows above 106 cubic feet per second being maintained. During these high deliveries chlorination of the San Jacinto reservoir outflow was constant at rates varying between 400 and 900 pounds of liquid chlorine per day averaging 9 pounds per million gallons. Laboratory determination is made of the amount of chlorine dosage necessary to kill bacterial growths that otherwise would produce slimes on the inner surface of the pipe and cause increased frictional resistance to the flow of water. The design capacity of the San Diego aqueduct is 85 cubic feet per second and since, at the high rates of flow such as were maintained, a small increase in frictional resistance in the pipe \vnuJd cause an overflow at an open structure, constant vigilance was required in regulat.ing the chlorine dosage in order to prevent the growth of friction-producing organisms. Due to the large run- off from winter rains received in storage reservoirs of constituents of the San Diego County Water Authority delivery of water to the San Diego aqueduct was discontinued from May 9 to 21 and was then resumed at 8 cubic feet per second. During the shutdown periud inspection of the interior of the pipe line revealed the pres- ence of a hard, thin calcium deposit on the interior of the pipe extending about 7 miles downstream from the reservoir. At all reservoirs spot treatments with copper sulfate to control the gl"Qwth of algae were necessary. At San Jacinto reservoir ex- tensive cutting of underwater grass with a mowing device attached to a boat was required during the summer months, warm weather accelerating its growth. At Lake Jl.fathews the shores and IirebreakH were cleared of brush and weeds by tractor and disc during the months of May and June ahead of rising water levels. District roads required some repairs during the year, Portions of the road at Lake Mathews from Cajalco dike to the east gate were surfaced with disintegrated granite, the roads connecting the head works, dike, and headquarters were seal-coated with an oil