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S E C O R Conceptual Site Model Chevron Service Station #9-6171 March 25, 2005 Page 27 6.7.2 Sampling and Analyses The following is a discussion of groundwater and soil sampling and analysis 6 7 21 Groundwater Sampling and Analyses In 1984, the California Environmental Protection Agency (Cal/EPA) became aware of this site after PCE was detected in Lincoln Village Maintenance District (LVMD) Well 1 Detected contaminants included PCE at concentrations up to 120 µg/L, trichloroethene (TCE) at concentrations up to 20 2 pg/L, trans-1,2 dichloroethene (trans-1,2 DCE) at concentrations up to 23 9 µglL, and cis-1,2 dichloroethene (1,2 DCE) at concentrations up to 3 6 µg/L LVMD Well 6 also exhibited concentrations of PCE, however, SECOR was unable to find the pertinent analytical data IIn March 1985, water samples from manholes down9 radient from the LVSC wells contained PCE at concentrations of 160,000 µg/L and 283 µg& In August 1985, these same manholes contained concentrations of PCE at 181 gg/L and 71 1 µg/L, as well as concentrations of TCE at 1 68 µg/L In addition, PCE was reported at a concentration of I 160 ppm in sludge samples taken from sewer manholes in the LVSC In November 1986, LVMD Well 6 was sampled and PCE was reported at a concentration of 19 5 ppb In 1988, groundwater monitoring wells MW-1 through MW-4 were installed on site Each well is screened between 60 feet and 70 feet bgs Groundwater samples from these wells contained PCE at concentrations of 2,500 ppb and TCE at concentrations of 190 ppb Between September 1990 and April 1991, eleven additional groundwater monitoring wells were installed on site Eight wells were screened between 60 feet and 70 feet bgs Two wells were screened to approximately 130 feet bgs, and one well is screened to more than 200 feet bgs The maximum concentration of PCE detected in the two monitoring wells installed at 130 feet bgs was 450 ppb The maximum total concentration of volatile organic compounds (PCE, TCE, and/or 1,2 DCE) was detected in the shallow wells at a concentration of 32,000 ppb There were no volatile organic compounds detected at or above laboratory reporting limits in the monitoring wells installed at more than 200 feet bgs 6.7 2.2 Soil Sampling and Analyses In 1988, during the installation of the first four groundwater monitoring wells, sod samples were collected at 35 feet, 45 feet, and 70 feet bgs Only one sample contained concentrations of PCE at 0 12 mg/kg Soil samples were also collected from beneath the site and under five sewer lines in the area PCE concentrations in soil samples collected • from underneath the site ranged from non-detect to 0 36 mg/kg PCE concentrations in soil N\Files\Projects\Chevron\Retadl#9-61711Site Conceptual ModeRFINAL_CSM doc