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Atlantic Richfield Company 10 ARCO 4932 16 E Harding Way Stockton CA .Pune 7,2002 rate is the highest pumping rate that will not draw the water level down to the pump over the duration of the constant-rate pumping test (approximately 24 hours) Following the completion of the step-drawdown test on April 2, 2002, the constant-rate pumping test was initiated The objective of the test was to create hydraulic stress in the ' aquifer by pumping from well EW-1 at a constant pumping rate, while monitoring drawdown in observation wells MW-1, MW-4, MW-6, and MW-7 Dunng the constant-rate pumping test, groundwater was continuously extracted for 1,323 minutes, ' while water levels were continuously logged in the pumping well and the four observation wells Extracted groundwater was discharged to a 6,500 gallon-capacity holding tank on-site Flow rates were monitored using a rotometer to register water flow from the system to the holding tank At the conclusion of the constant-rate pumping test, groundwater ' recovery data was monitored and recorded until water levels in the wells recovered to at least 99 percent of their pre-pumping levels The resulting drawdown and recovery data were analyzed to estimate the aquifer parameters of transmissivity (T), hydraulic conductivity (K), and storativity (S) Results of aquifer testing are discussed below Data plots of drawdown and recovery within pumping well EW-1 are included in Attachment J A summary of calculated hydraulic parameters is provided in Table 7 Step-Drawdown Pumping Test Pumping rates of 3 gpm, 4 gpm, 5 gpm, and 6 gpm were applied on extraction well EW- 1 for 30-minute intervals After pumping at 6 gpm for 30 minutes, the constant-rate pumping test was initiated utilizing this pumping rate Constant-Rate Pumping Test and Aquifer Recovery ' At the beginning of the constant-rate pumping test on well EW-1, pumping was continued at 6 gpm immediately after the step drawdown test and before recharge occurred After pumping from well EW-1 for 210 minutes at a rate of 6 gpm, it ' appeared that this pumping rate would dewater the well before equilibrium conditions were reached The pumping rate was then decreased to 5 5 gpm for 30 minutes, followed by a decrease to 5 gpm for 150 minutes, and another decrease to 4 5 gpm for ' 180 minutes The 4 5-gpm pumping rate also appeared to be dewatering the well and the pumping rate was reduced to 4 gpm for the remainder of the test (780 minutes) For data analysis, a time-weighted value for Q (pumping rate) was used, which was calculated using the pumping rates for the step-drawdown test and the constant-rate pumping test The constant-rate pumping test created a maximum drawdown of 13 73 ' feet in extraction well EW-1, 0 4 feet in well MW-1, 0 82 foot in well MW-4, 0 05 foot �\ in well MW-6, and 0 16 foot in well MW-7 After continuously pumping from well EW-1 for 1,323 minutes, the pump was shut down, and groundwater recovery levels 1 ' I1ARCO149321Reports\Asmt&AgfrTslRpt doc