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MONITORING WELL INSTALLATION WORK PLAN July 1998 K&S Gas & Grocery 701 East Charter Way, Stockton, California 1.0. INTRODUCTION AND SCOPE OF WORK In accordance with the request of Mr. Khaldoon Othman of K&S Gas & Grocery, Advanced GeoEnvironmental, Inc. (AGE) has prepared this Monitoring Well Installation Work Plan for 701 East Charter Way, Stockton,California. The location of the site is illustrated on Figure 1. Structures, underground storage tank (UST) and dispenser island locations are illustrated on Figure 2. This work plan is prepared in accordance with guidelines established by the San Joaquin County Public Health Services - Environmental Health Division (PHS-EHD) and Central Valley Regional Water Quality Control Board(CVRWQCB)for the investigation of underground storage tank(UST) sites. 2.0. BACKGROUND The site is located in a commercial area of low topographic relief in Stockton, California, on the northeast corner of Charter Way and Stanislaus Street. Two 12,000-gallon single-walled gasoline USTs were installed at the site in 1972. One 1,000-gallon double-walled UST was installed at a later time at the site. On 19 June 1997, four soil probe borings(probings)were advanced at the site near the 12,000-gallon USTs. Three probings were advanced to a vertical depth of 20 feet below surface grade (bsg); due to the presence of hydrocarbon odor, one probing (132) was advanced to a vertical depth of 45 feet bsg. TPH-g was detected at depths of 30 and 40 feet bsg at concentrations of 460 ppm and 1,000 ppm, respectively, beneath the south end of the USTs. Petroleum hydrocarbons were not detected at a depth of 45 feet bsg or in samples analyzed from the three other probings. Three underground storage tanks (USTs) were removed from the site on 13 February 1998. Petroleum hydrocarbons were detected in soil samples collected from below the two 12,000-gallon USTs at concentrations as high as 1,400 parts per million (ppm, reported as milligrams per kilogram). Petroleum hydrocarbons were not detected beneath the 1,000-gallon UST. One 20,000-gallon UST was installed at the site following the 1998 UST removals. Approximately 341 tons of hydrocarbon-impacted soil were excavated during removal of the old USTs and overexcavation for the installation of the new UST and piping. Soil was disposed at Forward Landfill. During the UST installation, two conductor casings were installed through the pea gravel adjacent to the UST in anticipation of future site assessment need. A&-anced GeoEnvironmental.Inc.