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Results of Groundwater Pumping Tests - 152 East 11th Street, Tracy Page 6 Pumping Trials To establish the appropriate types, sizes and capacities of the pump, flow meter and ancillary equipment required to perform the tests, a pumping trial was conducted on December 21st 1993 That effort showed that it would be necessary to pump from Well NAV 6 using an air-powered suction sump set on the surface That equipment was necessary because no submersible pumps are manufactured that can be installed in a 2 in diameter well casing and that can sustain a discharge flow rate sufficient to produce an adequate drawdown of the groundwater level in the well under the prevailing discharge- head and well-yield conditions The pumping trial showed that a sustained discharge flow rate of between 8 and 10 gallons per minute would produce a drawdown of between 4 and 6 ft in the pumped well, NAV 6, and that a small, but measurable, drawdown would occur in the observation well, NAV 3, within 15 min from the time pumping was started On December 21st there was persistent fog in the area of the site and the air temperature did not rise above 45°F Such conditions frequently occur in the Tracy area during the winter months and often persist for days or weeks These weather conditions result in a high moisture content in the ambient air When this air is compressed to power an air- powered, suction pump and then undergoes rapid cooling due to the sudden adiabatic pressure reduction that occurs when it is exhausted from the pump, the contained moisture freezes and the resulting ice fouls the pump valves This causes the pump to fail a short time after it is started Low ambient temperatures aggravate the pump icing problem This experience showed that, to perform a pumping test of adequate duration, it would be necessary to wait for conditions when the air was free of fog, of sufficiently low moisture content and at sufficient ambient temperature that it would not cause the pump to freeze Equipment Selection Based on the pumping trials conducted on December 21 st 1993, the following equipment was selected for the groundwater pumping tests A Wilden Model M-2, air-powered, suction pump connected to a 0 75 in internal diameter suction line equipped with a spring-activated, foot valve set at a depth of 18 ft below the top of the 24 ft deep casing of the pumped well (i a approximately 10 ft below the static water level), a 0 75 in internal diameter discharge line to conduct the pumped water to the sanitary sewer, a zero to 10 GPM, pitotube-type flow meter mounted on the discharge line and, flow-regulating and shut-off valves mounted in the discharge line down stream of the flow meter To measure depths to groundwater in the pumped and observation wells a standard, conductivity-type, water-level probe and a Hermit Model SE2000 data logger manufactured by In-Situ Inc connected to two Model PXD-260 zero to 10psi range, pressure transducers, also by In-Situ Inc , were selected