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R604 .UPDATE 23 10-20-1993 <br /> Dissolved Petroleum Hydrocarbons in Ground Water (EPA method 5030 <br /> TFH as gasoline) : <br /> Dissolved total fuel hydrocarbons, gasoline range (TFHg) is <br /> present in MW5, and MW2 which contained 0 . 86 and o . 26 parts per <br /> million (mg/L) respectively. All other wells sampled, , <br /> MW4 , MW6 and MW7 were below detection limits on September 15, <br /> 1993 . MW5 has tested below 1 ppm for gasoline range hydrocarbons <br /> since the June 24, 1991 . The laboratory reported that MW2 does <br /> not match gasoline but contained a single peak. Another sample <br /> was obtained from MW2 on August 20, 1993 and analyzed for <br /> Volatile Organic Compounds using EPA Method 624 . This analysis <br /> showed the single compound as 1, 2-Dschloroethane at 20 <br /> (ppb) , All other wells have tested below 1 ppm gasoline range <br /> hydrocarbons since the March 29, 1992 sampling. These analyses, <br /> when compared to those of December 15, 1991, substantiate the <br /> removal of hydrocarbons associated with the ground water, see <br /> 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 192, <br /> 1992 sampling, except MWS . During the September 11, <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 TMWS <br /> most <br /> to <br /> contain ethylbenzene (1 . 2 ug/L) and xylenes (35 ug/L). <br /> he <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 /> concentrationlhlmnevels (MCL) s <br /> that are applied fordrinkingwaterintheCalifornia <br /> MAXIMUM CONTAMINANT LEVELS (MCL) FOR PRIMARY DRINKING WATER, <br /> TITLE 22 or DHS. <br /> Primary MCL <br /> (no adverse <br /> health affects) <br /> 1 ug/L <br /> BENZENE 1000 ug/L <br /> TOLUENE 700 ug/L <br /> ETHYLBENZENE 1754 ug/L <br /> Total XYLENES <br /> Vapor extraction has removed most BTEXs from the ground water as <br /> shown by sample results obtained from the monitoring wells. The <br /> when <br /> primary MCLs have been obtained since September 11, 1992Present <br /> MW1, tested 1 . 2 ppb benzene. With this in mind, " year, <br /> California Water Quality Goals" <br /> have been met for over 1 Y <br /> see Table I . <br /> page 2 <br />