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Atlantic Richfield Company Page 14 ARCO Station No 4932 Stockton California August 29,2002 • Capture zones of approximately 31 feet and 48 feet were calculated in the downgradient and cross-gradient directions, respectively The capture zone was calculated using the Javandel and Tsang (1986) method • A pumping rate 4 and 6 gallons per minute was used for the constant rate drawdown pumping test • The geometric mean of T, K, and S for the observation wells was determined to be 0 34 ft2/min or 3,600 gdp/ft, 0 014 cm/sec, and 0 03, respectively The well installation and aquifer pumping test is documented in SECOR's report titled,Site Assessment and Aquifer Testing Results, dated June 7, 2002 5.2.2 Conclusions Based on measurable drawdown of water levels in the pumping well and observation wells at pumping rates ranging between 4 and 6 gpm, and the calculated capture zone radii of 31 feet and 48 feet in the downgradient and cross-gradient directions,respectively, GWE appears to be a capable remedial alternative for removing petroleum hydrocarbons and MtBE from beneath the site The newly installed additional extraction well (EW-2) would also be used to capture and prevent the further downgradient migration of the dissolved petroleum . hydrocarbon/MtBE plume 5.3 Batch Extraction/Interim Remediation Batch extraction as a form of interim remediation was initiated on March 18, 2002 and was subsequently conducted on April 19, April 29, May 13, May 30, June 21, July 3, July 18, and August 2, 2002 Batch extraction events prior to May 30 were reported in SECOR's Quarterly Groundwater Monitoring Report, Second Quarter 2002 dated July 8, 2002 Batch extraction events after and including May 30, 2002, will be reported in the third quarter 2002 groundwater monitoring report As of August 2, 2002, 23,350 gallons of impacted groundwater have been removed from wells MW-1, MW-4, MW-6, SVE-1, EW-1, and EW- 2 by batch extraction The total volume of groundwater removed from batch extraction events is included in Table 8 6.0 EVALUATION OF REMEDIAL ALTERNATIVES 6.1 Evaluation of Remedial Feasibility Testing and Remediation Goals The presence of dissolved petroleum hydrocarbons and MtBE in on and off-site wells and the results of remediation feasibility testing are the basis for evaluating the effectiveness of proposed remedial alternatives • Two goals of this remediation effort are (1)the removal and/or in-situ biodegradation of petroleum hydrocarbons and MtBE in soil and groundwater to below applicable cleanup I 1ARCO\49321PAR\PAR doc