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Advanced <br /> GeoEnvironmental, Inc. <br /> 06 September 2002 <br /> AGE Project No 95-0130 F <br /> Mr Nuel Henderson <br /> San Joaquin County Environmental Health Department ` s <br /> 304 East Weber Avenue, Third Floor .afl <br /> Stockton, CA 95202 <br /> Subject- Ground Water Extraction Capture Zone Analysis <br /> TOP FILLING STATION <br /> 101 South Wilson Way, Stockton, California <br /> Dear Mr Henderson <br /> In accordance with our telephone conversation on 20 June 2002,Advanced GeoEnvironmental, Inc <br /> (AGE) has performed a ground water extraction capture zone analysis for 101 South Wilson Way, <br /> Stockton,California(site) The purpose of the capture zone analysis is to demonstrate the theoretical <br /> area that would be influenced during ground water extraction activities from one well at the site <br /> Procedures for performance of a 24-hour ground water extraction pump test was outlined for the site <br /> in Feasibility Studies and Monitoring Well installation Work Plan, dated 11 March 2002, and <br /> approved by the San Joaquin County Environmental Health Department (EFID) on 25 April 2002 <br /> To date,ground water aquifer characterization testing has not been performed at the site Therefore, <br /> general ground water aquifer characteristics such as hydraulic conductivity and draw-down at <br /> specific pumping rates must be estimated to calculate the capture zone Literature on capture zone <br /> equations was obtained by AGE from Practical Design Calculations for Ground Water and Sol/ <br /> Remediation, Kuo, 1999(Appendix A) <br /> The following variables were estimated based on site characterization data <br /> • Utilizing general correlations between soil type and hydraulic conductivity, AGE estimates <br /> a hydraulic conductivity(K)value at 10"2 cm/s(Appendix B)based on fine to medium sand, <br /> silty sand and sandy silt generally encountered at depths between 35 and 55 feet below <br /> surface grade (bsg) <br /> • AGE estimates the average ground water gradient to be 0 004 ft/ft based on ground water <br /> monitoring data collected at the site since January 1995 <br /> • AGE selected a ground water extraction rate of 5 gallons per minute (GPM) based on the <br /> 837 Shaw Road,Stockton,California 95215 <br /> Tclephonc(209)467-1006 FAX(209)467-1118 <br />