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Attachment A <br /> Investigating Officers Report <br /> Steven Sasson, Senior REHS <br /> SJCEHD <br /> 304 E Weber Ave., Third Floor <br /> Stockton CA 95201 <br /> (209) 468-3459 <br /> Background Information <br /> On January 29, 1988 a pre-tank removal assessment was conducted. <br /> Contamination was discovered in 2 of 5 borings to 25 feet deep. Contamination <br /> was present on the north side of the west dispenser (KB3) and the south side of <br /> the east dispenser (KB5). The tanks were north of the dispensers. <br /> On March 29, 1988 two 10,000 gallon unleaded tanks located north of the <br /> dispensers and a 550 gallon waste oil tank located south of the dispensers were <br /> removed. Analytical results of a sample from the portion of the tank pit adjacent <br /> to the north side of the western dispenser at a depth of 16 feet confirmed <br /> contamination as Gasoline (TPH-g) 582 parts per million (ppm), Benzene .6 <br /> ppm, Toluene 6.5 ppm, Ethyl Benzene 10.4 ppm and Xylene 39 ppm. <br /> On March 30, 1988 an over excavation was conducted on the former tank pit to <br /> a depth of 26 and 30 feet. Confirmation samples were slightly contaminated <br /> (TPH-g <18 ppm and Benzene <1.72 B). Results of a pipeline sample showed <br /> minimal impact. Impacted soil in the product line area was not removed. <br /> PHS/EHD was on site during sampling. <br /> On June 1, 1988 monitoring wells 1,2,3 were installed. The wells were drilled to <br /> 50 feet and screened from 20 to 50. MW-1 had no contamination and MW 3 had <br /> organic vapor analyzer (OVA) readings below 7 ppm. MW-2 had a high OVA of <br /> 1088 ppm at 35 feet and was 56 ppm at 50 feet. MW-2 and MW-3 were mostly <br /> sandy and MW-11 was mostly clay. Groundwater was encountered at 30 feet in all <br /> three wells. <br /> On June 6, 1988 the wells had their initial samples taken. Lab results of Benzene <br /> were non detectable for MW-11, 5700 ppb for MW-2, and 1.0 ppb for MW-3. The <br /> wells went dry in 1990 and were not re-sampled until March 26, 1993. The initial <br /> analytical results of Benzene after drought conditions were non detectable (ND) <br /> in MW land 1400 ppb in MW-2. MW-3 was sampled June 4, 1993 with a <br /> Benzene level of 260 ppb. <br />