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Atlantic Richfield Company Page 4 ARCO Station No 4932 Stockton,California August 29 2002 In the 3`d Quarter 2001, LPH was discovered in wells SVE-1 and MW-4 Upon discovery, SECOR notified the SJCPHS and initiated weekly LPH removal SECOR performed weekly LPH removal until the LPH was no longer present (six weeks) Currently, LPH is not present at the site however, SECOR periodically checks site wells to verify this If LPH is rediscovered, LPH removal will be reinitiated In 2001, SECOR conducted a door-to-door survey of businesses and residences in the area to identify any water supply wells within a 500-foot radius of the site A questionnaire was supplied to those businesses or residences that could not be contacted first hand Based on review of verbal and written survey results returned to SECOR, there were no water supply wells confirmed within a 500-foot radius of the site According to the SJCEHD in a letter dated November 21, 2000, two water supply wells were documented in the vicinity of the site These water supply wells were located in the field, approximately 1/2 mile east of the site at the Stockton State Hospital, and approximately 2,000 feet northwest of the site, at the intersection of Wyandotte and Commerce Streets Results of the well survey are included in SECOR's report titled,Additional Site Assessment Report, dated November 9, 2001 Also in 2001, SECOR performed a utility survey to evaluate whether nearby off-site utilities or other underground improvements may act as potential conduits for migration of petroleum hydrocarbons Since depth to water at the site is approximately 27 feet bgs and no underground improvements or utilities were identified near this depth, it is unlikely that any subsurface utilities or other unknown underground improvements are preferential migration pathways for petroleum hydrocarbon-impacted groundwater SECOR concluded that higher potential exists for vapor-phase contaminant migration through these areas (SECOR, Additional Site Assessment Report, dated November 9, 200 1) As a result of the discovery of LPH in wells MW-4 and SVE-1 during the third quarter 2001 sampling event on July 20, 2001, weekly interim groundwater remediation was initiated on October 29, 2001, which consisted of the removal of LPH and petroleum hydrocarbon- impacted groundwater from the wells with a bailer Interim GWE continued for approximately six weeks until measurable LPH was no longer present Between October 29, 2001 and December 17, 2001, approximately 10 to 15 gallons of LPH had been removed from the wells As a result of the continued presence of elevated concentrations of petroleum hydrocarbons and MtBE in on-site wells, interim GWE was reinitiated on March 18, 2002 utilizing a vacuum truck Interim GWE by vacuum truck is currently conducted on a biweekly basis utilizing selected wells containing LPH or elevated concentrations of petroleum hydrocarbons and MtBE (MW-1, MW-4, MW-6, SVE-1, EW-1) Between March 18 and August 2, 2002, approximately 23,350 gallons of LPH and petroleum hydrocarbon- impacted groundwater had been removed from beneath the site On March 14 and 15, 2002, West Hazmat installed one deep groundwater monitoring well (DMW-1) and one GWE well (EW-1) DMW-1 and EW-1 were completed at 81 feet bgs s and 44 feet bgs, respectively Stabilized groundwater levels in wells DMW-1 and EW-1 1 WRCO\49321PAR\PAR doc