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_ _ T <br /> 01 <br /> Quik Stop Market No. 132 July 11, 1991page g <br /> Project No. 3-49132-31 <br /> underlying aquifer, creating asemi- <br /> confined to confined aquifer. The confined <br /> ter levels in wells MW-2, MW-3, and MW- <br /> condition is the reason the groundwa <br /> appear to be located in this clayey layer. Spanning the interface between the lower <br /> �. sandy aquifer and the clayey confining aquitard would allow for sampling of any <br /> petroleum hydrocarbons which may be flowing along the top of this aquifer. Based <br /> upon this information, it is Exceltech's opinion that monitoring wells MW-2, MSN-3, <br /> and MW-4 are properly installed and no further installations are necessary at these <br /> locations. <br /> Fecal coliform analyses were performed on groundwater samples collected from wells <br /> located with 50 feet of sewer lines (MW-2, MW-4, and MW-1R). None of the water <br /> samples had detectable fecal coliform except for MW-2, which had a concentration of <br /> 170 bacteria per 100 ml. The most likely source of:.his contamination is a main sewer <br /> line located under W. Hammer Lane. The results were reported to the San Joaquin <br /> County Public Health Services, who agreed to continue to have this well tested for fecal <br /> coliform and include that data in a quarterly groundwater monitoring program. <br /> The State of California Department of Health Services ('JHS) maintains drinking water <br /> standards (maximum contaminant levels [MCL] and action levels [ALI) for petroleum <br /> ds in drinking water. The following is a list of the <br /> hydrocarbon related compoun <br /> current DHS drinking v,,ater standards for BTEX. <br /> Compound Concentration <br /> Benzene 1.0 ppb MCL <br /> Toluene 100 ppb AL <br /> Ethyl benzene 680 ppb MCL <br /> Total xylenes 1,750 ppb MCL <br /> The`c oricentzativn of.benzene detected in the:groundwater exceeds the MCL.i <br /> CONCLUSIONS AND RECOMMENDATIONS <br /> Five exploratory borings have been drilled at the site. Six monitoring wells have been <br /> installed, one of which has been destroyed. These have revealed the presence of two <br /> aquifers beneath the site, a lower shallow aquifer and an upper perched aquifer. This <br /> perched aquifer appears to occur atop a buried ancient stream channel. <br /> mm The results of chemical analyses of soil samples indicate that petroleum hydrocarbon <br /> contamination was not detected in any of the soil samples collected from MW-1R and <br /> s of groundwater samples indicate that petroleum <br /> MW-5. Results of chemical analyse <br /> t� <br />