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Atlanc Richfield Company 9 ARCO 4932, 16 E Huding Way,Stockton CA lune 7 2002 Soil stratigraphy at the proposed depths specified within SECOR's January 15, 2002 work plan and the SJCEHD February 14, 2002 letter within the boreholes for extraction well EW-1 and deep well DMW-1 consisted of silty sand In order to prevent the possible migration of petroleum hydrocarbon-impacted ' groundwater Into deeper zones, the borehole for well EW-1 was filled with bentonite through the sandy silt layer encountered between approximately 45 feet and 50 feet bgs, and completed within the sandy silt/clayey silt layer at approximately 44 feet bgs For the same reason, well DMW-1 was advanced through encountered layers of silty sand and sand between approximately 73 feet and 80 feet bgs, and completed within a clayey silt layer at approximately 81 feet bgs Within the past work plan submittals, SECOR proposed that the extraction wells 1 would be installed with a 4-Inch diameter casing Well EW-1 was constructed with a 6-Inch casing to increase the volume for the future removal and treatment of petroleum hydrocarbon-impacted groundwater beneath the site ' • Logging of Soil. Instead of logging soil at 5-foot intervals as proposed within the past work plan submittals, soils were continuously logged between 50 feet and 81 feet bgs in the boring for deep well DMW-1, and between 20 feet and 50 feet bgs in the boring for extraction well EW-1 to evaluate soil stratigraphy beneath the site RESULTS OF AQUIFER TESTING The purpose of this test was to evaluate hydrogeologic conditions beneath the site and to determine whether GWE is a feasible alternative for remediating dissolved petroleum hydrocarbons and MtBE in groundwater beneath the site Methodology Prior to beginning the step drawdown and constant rate pumping tests, pressure transducers with built-in data-loggers were installed in pumping well GWE-1 and ' observation wells MW-1, MW-2, MW-4, and 1\4W-6 on April 1, 2002 to monitor water levels before, during, and after aquifer testing (Figures 2 and 3) The data-loggers were programmed to record water level depths at one-minute intervals A step-drawdown test was conducted on April 2, 2002 using a submersible pump in well EW-1 Prior to the start of the test, water levels in pumping well EW-1 and the four observation wells (MW-1, MW-4, MW-6, and MW-7) were monitored Well EW- 1 was subsequently pumped for a specified period at different pumping rates (steps) while monitoring changes in the water level in the pumping well The water levels and corresponding times were recorded during each step to allow for analysis of the ' drawdown attributed to each step, and to provide information needed for the selection of an optimum pumping rate for the constant-rate pumping test The optimum pumping ' IIARCO149321Reports\Asmt&AgfrTstRpt doc