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QUARTERLY SUMMARY REPORT Third Quarter 2002 (July - September) krs1 TOSCO (76) Service Station No. 11195 16500 South Interstate 5 Lathrop, CA CITY: Lathrop COUNTY: San Joaquin BACKGROUND. The site contains an operating 76 service station. Five groundwater monitoring wells were installed in, December 1992. Two additional monitoring wells were installed in September 1993. In July 1998,one waste oil underground storage tank (UST) and the associated remote fill piping were removed from the site. Approximately 10 cubic yards of soil were removed from the site and disposed of at an approved landfill. An abandoned domestic well was sampled and properly destroyed in July 1998. In September 1998,one monitoring well was destroyed and five monitoring wells were installed in the vicinity of the site. Sensitive receptor and water well surveys have been performed for the site. In December 1998 and January 1999,three fuel USTs were removed from the site during UST replacement activities. Approximately 1,017.96 tons of soil and backfill materials were removed from the site and disposed of in an approved Iandfill. A slotted temporary conductor casing was installed in the former UST pit to facilitate removal of hydrocarbon-impacted groundwater. In May 1999 Tosco Marketing Company assumed responsibility for investigative and remedial activities at the site from f, =r� British Petroleum(BP). Submitted Interim RemedialAction Plan in July 1999. In February 2002,five offsite geoprobe soil borings were advanced downgradient of the subject site. Five offsite Groundwater Monitoring Wells were installed in May 2002. The seventeen monitoring wells are currently sampled on a quarterly basis. Corrective Action Plan(dated August 28, 2002) submitted. RECENT QUARTER ACTIVITIES: • Monitored and sampled the existing wells. • Prepared and submitted the quarterly summary report. • Purged a total of 58,500 gallons of groundwater from the conductor casing CC-1, monitoring wells MW-3, MW-4, MW-5 and MW-10 during 13 weekly purging events. • Submitted a report documenting procedures and results of offsite monitoring well installation. • Submitted a Work Plan for additional downgradient delineation. ANTICIPATED NEXT QUARTER ACTIVITIES: • Monitor and sample groundwater monitoring wells. • Purge 5,000 gallons of groundwater per week per the Interim Remedial Action Plan. • Prepare and submit the quarterly summary report. • Install 4 offsite downgradient groundwater monitoring wells in Harlan Road 140793.01 I i E