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Mr Harlin Knoll • May 31, 1995 (9347-0085) BACKGROUND The following subsections describe the site and its history Site Descnption The site is an operating service station located on the Lodi South 7 5 minute topographic map at T2N, R6E, section 13, NE 114, SE 1/4 According to the San Joaquin County assessors office, the parcel number is 092-110-09 The 0 80 acre site is located in an agricultural/residential area of Stockton, at the southeast corner of Moreland Court and Hammer Lane Shell dispenses three grades of unleaded gasoline from three 12,000-gallon, double-walled fiberglass UST Soil beneath the site consists primarily of unconsolidated sand, silt, and clay Ground water is approximately 70 feet below grade (bg) Pm-Tank Removal Investigation On April 4, 1988, Delta Environmental Consultants, Inc (Delta), performed a pre- • tankpull assessment Soil borings B-1 through B-4 were advanced to 21 feet bg Borings B-5 and B-6 were advanced to 16 5 feet bg The results are summarized in their April 19, 1988, letter report Tank And Piping Removal During December 1988 and January 1989, three single-walled steel UST(one 7,500-gallon and two 5,000-gallon) and product piping were removed Laboratory analyses of soil sample TS-2 collected from the excavation at 15 feet bg (Figure 2) indicated a concentration of total petroleum hydrocarbons of 1,030 parts per million (ppm) Petroleum hydrocarbons were indicated in soil samples collected from beneath the western dispenser islands, at approximately 4 feet bg (Figure 2, PL-5 and PL-6) Laboratory analyses indicated TPH concentrations of 1,130 ppm in soil sample PL-5, and 117 ppm in PL-6 Benzene was also indicated at 0 680 ppm in PL-6 Approximately 200 cubic yards (yd`) of soil containing petroleum hydrocarbons were excavated during tank removal The soil was disposed of at Forward Landfill in Manteca, California The replacement UST (three, double-walled fiberglass) were installed on January 9, 1989 According to blueprints, they overlapped the west end of the former UST The overlap has not been clearly represented in Delta's "Tank Closure Report," dated April 7, 1989 Additional Investigation On August 8, 1989, two soil borings, SB-7 and SB-8, were advanced to 31 5 and 26 5 feet, respectively Boring SB-7 was located approximately 15 feet northwest of product line sample PL-5 A soil sample was collected at 11 5 and 26 5 feet bg Boring SB-8 was located 93470055 AWP 2 -