C153333 Feasibility Study - Laserfiche WebLink

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I I I I I I I I I I I I I I I I I I I V-J chamber, level with the invert of the 42-inch pipe, The major problem with the diversion dam is that the. sand and gravel carried by Beaver Creek has filled the pool. so that there is less than a 3-acre foot capacity to the pool to absorb variations in stream flow rates. The sluice gate has been utilized two or three times each year to re- move accumulated sediment, but is only able to remove up to about 7.000 cubic yards each time the pool is flushed. The leakage problems with the sluice gate make this a tedious operation, If the capacity of the diversion pool were increased, less sand could enter the aqueduct and streamflow fluctua- tions would be dampened. resulting in fewer trips by the ditch rider to adjust the gate opening, Measurement of the filled area upstream of the diversion dam indicates that the pool could 'be enlarged up to a 50-acre foot capacity by dig- ging, This would remove about 80,000 cubic yards of sand and gravel. The pool would again fill in after several years, but some improvements could be achieved, The material could be stockpiled on the floodplain next to the pool, A con- tractor might be interested in removing the material and there is an access road on the west side of the diversion. At present, the only point to remove sand from the 42- inch pipeline is through an eight-inch drain line which is located where the pipeline climbs up out of the Beaver Creek valley, This drain line is not large enough to generate a high velocity to flush much sand from the pipeline, There is a need for an in-line sand trap to be located immediately downstream of the diversion dam. A box structure with in- ternal baffles would allow much of the sand which enters through the diversion to be settled out and periodically be flushed back to Beaver Creek. A combination of the sand trap and enlarging the diversion pool should greatly reduce the sediment load into the upper canal, The recommended improvements at the diversion dam are: 1. removal of 80.000 cubic yards of accumulated sediment;