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R604 UPDATE 19 5-19-1993 Dissolved Petroleum Hydrocarbons an Ground Water (EPA method 5030 . TFH as gasoline) With the exception of MWS and MW2 , which contained 370 and 360 parts per billion (ug/L) respectively, dissolved total fuel hydrocarbons, gasoline range, were below detection limits for wells sampled on December 7, 1992 ( MWI, MW3 , MW4 , MW6 and MW7) MW5 has tested below 1 ppm for gasoline range hydrocarbons since the June 24 , 1991 sampling and the laboratory reported that MW2 does not match gasoline but contained a single peak. All other wells have tested below 1 ppm gasoline range hydrocarbons since the March 29, 1992 sampling This analysis substantiates the removal of hydrocarbons associated with the ground water and is evident in comparing the ground water samples obtained on December 16, 1991 to those obtained on March 5, 1992 and later, see Table 1 Before vapor extraction, November 21, 1990 , gasoline range hydrocarbons were detected in MW1 (2 mg/L) , and MWS (31 mg/L) BTEX -in Ground Water (EPA method 602) No wells contained any BTEXs in the samples of the monitoring wells from the March 5, and June 2 , 1992 sampling During the December 16, 1991 sampling round only MW1, MW2 , and MW5, had BTEXs in very low concentrations During the September 11, 1992 sampling, sample results from MW1 detected only benzene (1 2 ug/L) and MW5 sample results indicated only the xylenes (4 1 ug/L) The December 7, 1992 sample results showed only MW5 to contain ethylbenzene (1 2 ug/L) and xylenes (35 ug/L) . The most recent sampling (March 30, 1993) only MW5 contains benzene at 0 4 ug/L, ethylbenzene at 4 . 3 ug/L and xylenes at 56 ug/L. MW5 is presently being utilized as a vapor extraction well . This pulling of the contaminants to the well consequently increased concentrations MAX-T= CONTAMINANT LEVELS FOR PRIMARY DRINKING WATER, TITLE 22 or DHS. BENZENE 1 ug/L TOLUENE 100 ug/L ETHYLBENZENE 680 ug/L Total XYLENES 1, 750 ug/L Vapor extraction has removed most BTEXs from the ground water as shown by sample results obtained from the monitoring wells since March 5, 1992 Except for MW1, which contained 1 2 ppb benzene on the September 11, 1992 sampling, the "Present California Water Quality Goals" have been met, see Table 1 Fecal Coliform: From December, 1991 through February, 1992 , monthly fecal coliform samples were collected from monitor wells MW3 , MW4 , MW5 and MW6 Samples were again collected in June, 1992, from monitoring wells MW3 , MW4 and MW6 . During the September 11, 1992 sampling, MW3 and MW6 were dry, no fecal coliform samples were obtained. Table 2 shows the results of these samples As of page 2