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31 August 2005 AGE-NC Project No. 96-0232 Page 3 of 30 the August 1993 event at a concentration of 9.4µg/1. Results of the preliminary environmental site assessment are summarized in Appendix D. 2.2. UNDERGROUND STORAGE TANK REMOVAL On 31 March 1995,four 12,000-gallon gasoline USTs,one 12,000=gallon diesel UST and associated fuel dispensers were removed from the site and were replaced with three 12,000-gallon gasoline USTs,one 12,000-gallon diesel UST and new fuel dispensers. Following removal of the UST;the tank pit was laterally over-excavated approximately 2 feet to remove discolored soil with petroleum odor; thereafter, grab ground water samples and sidewall soil samples were collected from the excavation (8 to 9 feet bsg). A floating petroleum sheen was observed in the UST cavity at approximately 8 feet bsg during collection of grab water samples.Analytical results of soil samples did not detect any constituents of concern;however,analytical results of grab ground water samples detected total petroleum hydrocarbons quantified as gasoline (TPH-g) at concentrations as high as 18,000 µg/l, TPH-d (diesel) as high as 1,000 µg/l, benzene as high as 230 µg/1, toluene as high as 300 µg/1, ethylbenzene as high as 160 µg11 and total xylenes as high as 860 µg/1. 5 Between 03 and 12 April 1995,the UST tank pit was deepened an additional 2-3 feet and a total of 180 cubic yards of potentially impacted saturated soil was further excavated from the tank pit. Thereafter, additional grab ground water samples were collected from the over-excavated tank .cavity;additional soil samples were collected beneath the over-excavated tank cavity(14%to 15 feet bsg) and beneath the former product piping locations (3 to 6 feet bsg). Analytical results of soil samples did not detect any.constituents of concern beneath the over-excavation; however, TPH-g was detected from product piping sample LB3 (southeast fuel dispenser)at a concentration of 1.5 milligrams.per kilogram (mg/kg). Analytical results of the additional grab ground water samples detected TPH-g at concentrations as high as 1,600 µg/1, TPH-d as high as 1,400 µg/l, benzene was not detected,toluene as high as 4.2 µg/1, ethylbenzene as high as 89 µg/I and total xylenes as high as 73 µg/1. During the April 1995 over-excavation activities,monitoring well MW-3 was abandoned under San Joaquin County Environmental Health Department well destruction permit(See Appendix E);MW-3 was abandoned by pressure grouting to the surface with a portland grout mixture to the surface. It became necessary to abandon MW-3 due to the close proximity to the over-excavation. Analytical results of UST removal soil and grab ground water samples are summarized in Table 1; UST removal soil and grab ground water sample Iocations are depicted in Figure 4. A report of findings(Report on tank Removal Soil Sampling and Source Removal Overexcavation, dated 24 May 1995)was prepared by Ground Zero Analysis and submitted to the SJCEHD. Advanced GeoEnvironmental,Inc. �7