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Ms Margaret Lagono November 27, 1995 (9347-9013) The followingsections include the site description, background, investigation results and g conclusions Site Description The site is an active retail gasoline service station located on the southeast corner of Kettleman Lane and Hutchins Road in Lodi, California (Figures 1 and 2) The site is located within a commercial area of Lodi Background In September 1989, Aegis Environmental Consultants (Aegis) of Roseville, California, performed a pre-UST replacement site assessment at the subject site Soil borings B-1 through B-15 were advanced onsite to depths ranging from 11 5 to 21 5 feet below grade, at the locations identified on Figure 2 The soil sample collected from boring B-8 at 10 feet below grade (bg) contained concentrations of total petroleum hydrocarbons (TPH) as gasoline and benzene of 1,060 and 1 81 parts per million (ppm), respectively Complete assessment results were documented in Aegis' Pre-Tank Site Assessment Results Report dated October 16, 1989 Review of the laboratory results, included in Attachment 2, indicated that the extent of the adsorbed-phase petroleum hydrocarbons was limited to the immediate vicinity of boring B-8 • On October 3 and 4, 1990, Aegis installed 4-inch-diameter ground water monitoring wells MW-1 through MW-3 to depths of 75, 73, and 75 feet bg, respectively (Figure 2) No TPH as gasoline or benzene, toluene, ethylbenzene, and total xylenes were detected above the reported detection limits in the soil and ground water samples collected from wells MW-1 through MW-3 Complete investigation results were documented in Aegis' Site Assessment Monitonng Well Installation Results Report dated March 26, 1991 No concentrations of petroleum hydrocarbons have been detected above reported detection limits in any of the three monitoring wells since October 1992 The wells were monitored and sampled quarterly until 1994 In a February 8, 1994 letter, the S7CPHS/EHD authorized an annual monitoring and sampling program The wells are currently monitored and sampled annually in the fourth quarter Soil Borings and Monitonng Well Installation On August 8, 1995, Fugro personnel supervised the drilling and sampling of soil borings MW-4 and B-17, by Gregg Drilling of Martinez, California, using a hollow-stem-auger drill rig (Figure 2) Boring MW-4 was drilled to 80 feet bg using 10-inch-hollow-stem augers Boring B-17 was drilled to 20 feet bg using 6-inch-hollow-stem augers Boring B-17 was drilled approximately 3 feet northeast of boring B-8 Boring MW-4 was drilled approximately 10 feet south of the current UST basin Soil samples were collected from each boring at 5-foot intervals and field screened using a portable organic vapor monitor Ground water was encountered in MW-4 at an approximate depth of 68 feet bg Soil types encountered generally consisted of sand, silty sand, and silt in each boring 93479013 ARR -2-