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Cheaper#76,890 N.Main St.,Manteca,California <br /> December 22,1995 <br /> Page 3 <br /> • A groundwater sample was procured from MW-4, which has historically been <br /> down-gradient from the former tank location. The sample was non-detect for <br /> TPH-g and BTEX. <br /> Quarterly monitoring was performed by Parker Environmental Services <br /> during 1993. In March, 1993, during the first quarter of morutonng, xylenes <br /> were measured at 1.2, 1.1, and 0 96 ppb in three of the wells (MW-1, MW-2, <br /> and MW-3). Toluene was present (1.2 ppb) in MW-4. All 4 wells were ND for <br /> 1,2-dibromoethane (ethylene dibromide) and for lead. <br /> All wells were ND for both TPH-g and BTEX in July, September, and <br /> December, 1993, and in April and July, 1994 Groundwater levels ranged from <br /> about 21 feet BGS to about 28 feet BGS over that period. Monitoring was not <br /> performed in October, 1994, because of the low water table <br /> Monitoring resumed in January, 1995, Wells MW-1, MW-3 and MW-4 were found <br /> to be free of the chemicals of interest at or above the analytical method detection <br /> limits MW-2 contained 1.3 ppb benzene, 0.91 ppb toluene, 0 79 ppb xylenes, and was <br /> ND for TPH as gasoline and ethylbenzene April 1995 sampling and analysis showed <br /> trace amounts of BTEX in MW-4 Water levels had risen up to about 12 feet above <br /> MSL. <br /> . In July, 1995, all samples were non-detect for TPH-g and BTEX. <br /> The environmental concern for this site is the possibility of residual petroleum <br /> hydrocarbons remaining in the soil above the groundwater, which due to the low <br /> rainfall for the last few years, has remained low. If groundwater rises to higher <br /> levels, possible groundwater contamination could re-occur. <br /> • <br /> Parker Environmental Services, 190 East 7th Street, Pittsburg, CA 94565-2317 <br /> Phone (510) 439-1024 Fax (510) 439-2566 <br />