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R604 :UPDATE 25 12-29-1993 <br /> that MW2 does not match gasoline but contained a single peak. <br /> Another sample was obtained from MW2 on August 20, 1993 and <br /> analyzed for Volatile Organic Compounds using EPA Method 624 . <br /> This analysis showed the single compound as 1, 2-Dachloroethane at <br /> 520 ug/L (ppb) . All other wells have tested below 1 ppm <br /> gasoline range hydrocarbons since the March 29, 1992 sampling. <br /> These analyses, when compared to those of December 15, 1991, <br /> substantiate the removal of hydrocarbons associated with the <br /> ground water, see Table 1 . <br /> Before vapor extraction, November 21, 1990, gasoline range <br /> hydrocarbons were detected in MW1 (2 mg/L) , and MW5 (31 mg/L) . <br /> BTEX in Ground Water (EPA method 602) : <br /> Analyses from the December 16, 1991 sampling round show that <br /> only MW1, MW2, and MW5, had BTEXs, in very low concentrations <br /> None of the wells contained BTEXs in the March 5, and June 2, <br /> 1992 sampling, except MW5 During the September 11, 1992 <br /> sampling, sample results from MW1 detected only benzene (1 . 2 <br /> ug/L) and MW5 sample results indicated only the xylenes (4 . 1 <br /> ug/L) . The December 7, 1992 sample results showed only MW5 to <br /> contain ethylbenzene (1 . 2 ug/L) and xylenes (35 ug/L) . The most <br /> recent sampling (September 15, 1993) only MW5 contained <br /> ethylbenzene at 0 7 ug/L and xylenes at 14 ug/L. MW5 is <br /> presently being utilized as a vapor extraction well . This <br /> pulling of the contaminants to the well consequently increased <br /> concentrations . Below are the maximum contaminant levels (MCL) s <br /> that are applied for drinking water in the California <br /> MAXIMUM CONTAMINANT LEVELS (MCL) FOR PRIMARY DRINKING WATER, <br /> TITLE 22 or DHS. <br /> Primary MCL <br /> (no adverse <br /> health affects) <br /> BENZENE 1 ug/L <br /> TOLUENE 1000 ug/L <br /> ETHYLBENZENE 700 ug/L <br /> Total XYLENES 1750 ug/L <br /> Vapor extraction has removed most BTEXs from the ground water as <br /> shown by sample results obtained from the monitoring wells . The <br /> primary MCLS have been obtained since September 11, 1992 , when <br /> MW1, tested 1 2 ppb benzene With this in mind, the "Present <br /> California Water Quality Goals" have been met for over 1 year, <br /> see Table 1 . <br /> Fecal Coli form: <br /> From December, 1991 through February, 1992, monthly fecal <br /> coliform samples were collected from monitor wells MW3 , MW4 , MW5 <br /> and MW6 . Samples were again collected in June, 1992 , from <br /> monitoring wells MW3 , MW4 and MW6 . During the September 11, 1992 <br /> sampling, MW3 and MW6 were dry, no fecal coliform samples were <br /> obtained. Table 2 shows the results of these samples . the only <br /> page 2 <br />