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' Aquifer Testing Work Plan • • Former PureGro Bro Facility ' Stockton, ton, Broadway Avenue - S[ock[on,California Sierra-Pacific Project No. 94-055.05 ' 4.9 Installation of the Pumping Well After Sierra-Pacific has installed both new observation wells, has developed and pump-tested the ' observation wells, and has collected and tested ground water samples, the drilling contractor will be ' mobilized for the third time and a 6-inch-diameter extraction well will be constructed at location E-1 on Figure 7 in accordance with the design of the observation wells. The extraction well will be used to ' perform a series of aquifer tests,as described below. Only contaminated intervals will be screened and tested. Screened intervals of the pumping well will likely be similar in length and position to the screened intervals of the observation wells. The well boring will be 12 inches in diameter. The slot-sizes and filter sand used to construct the extraction well will be larger than used for observation wells. The ' pumping well will be constructed to optimize the flow-rate and well efficiency. Individual aquifers will be isolated during the aquifer tests with expandable packers to selectively pump from the desired aquifer. t If the multiple aquifers identified in the observation well behave as a single unconfined aquifer,it may be necessary to screen the entire saturated interval between the aquifers. 4.10 Aquifer Tests ' A series of 8-hour aquifer (pumping) tests will be conducted at the Giglio property to determine the transmissivity and storage coefficient of the contaminated aquifers. Multiple confined or leaky aquifers ' will require multiple aquifer tests. Each aquifer test will involve a period of sustained pumping and concurrent water level measurements. The aquifers will be tested by pumping,then again by monitoring ' the recharge period. If ground water elevations do not stabilize within 8-hours,pumping will continue for 24 hours if necessary. ' An automated GL-300A data logger,manufactured by Global Water of Gold River, California will be ' employed for recording the draw-down of ground water in the extraction well (E-1), two observation wells (0-1 and 0-2),and monitoring well MW-8. Pressure transducers will be placed in the extraction ' well and in each of the observation wells. According to the manufacturer,the pressure transducers have an accuracy rating equivalent to t 0.002 feet of hydraulic head. Data will be recorded at a fixed rate ' SIERRA-PACIFIC GROUP 11