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enviroso <br /> Step-Discharge and Constant-Rate Discharge Aquifer Tests <br /> As proposed in the September 9, 1997 work plan, two pump tests will be performed in <br /> Well RW-1: a step-discharge test and a constant-rate discharge test. <br /> The step-discharge test is performed by pumping the well at increasingly higher discharge <br /> rates (steps)while monitoring the change in water level drawdown in the pumping well and <br /> in nearby monitoring wells. During each step of the test, the flow rate is metered using a <br /> flow gauge. Each discharge rate is held constant until the rate of change in drawdown in <br /> the pumping well stabilizes. The flow rate is typically doubled at each step until a flow rate <br /> is attained that the well cannot maintain and the well dewaters. The flow rate information <br /> collected from this test is used to determine the flow rate that will be used for the constant- <br /> rate discharge test. <br /> The constant-rate discharge test will be performed in Well RW-1. The well will be pumped <br /> at a constant flow rate for a period of 4 to 6 hours. <br /> Water level measurements will be recorded in the pumping well along with water level <br /> measurements in nearby monitoring wells during both tests. Once the pump is shut off, <br /> water level recovery data will be monitored until the pumping well has recovered a <br /> minimum of 90% of the drawdown observed during pumping. <br /> Pump testing data will be used to determine a sustainable pumping rate should ground <br /> water extraction be proposed as part of site remediation. Other aquifer characteristics will <br /> be calculated from the data collected during testing including: hydraulic conductivity, <br /> transmissivity, specific yield,radius of influence and an estimate of zone of capture. <br /> As requested by SJCPHS, ground water samples will be collected prior to the step- <br /> discharge test and subsequent to the constant-rate discharge test and analyzed for Total <br /> Purgeable Petroleum Hydrocarbons as gasoline (TPPH) by EPA Method 8015 (modified) <br /> and benzene, toluene, ethylbenzene, xylenes (BTEX) and methyl-tertiary-butyl-ether <br /> (MTBE) by EPA Method 8020. The pre-pumping and post-pumping ground water <br /> samples will be compared to make a determination of the effectiveness of ground water <br /> extraction for removal of MTBE in ground water. <br /> Schedule <br /> All of the various phases of field activities have been scheduled as follows: <br /> October 15, 1997 CPT Borings <br /> October 22 & 23, 1997 Pump Testing <br /> October 24, 1997 Drilling and installation of 3 Shallow Wells <br /> November 3 to 7, 1997 Drilling and installation of 3 Deep Wells <br /> This schedule is dependent upon receipt of drilling permits from SJCPHS and <br /> encroachment permits from the City of Stockton. <br /> 371 2 <br />