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R604 UPDATE 14 12-28-1992 <br /> associated with the ground water and is evident in comparing the <br /> ground water samples obtained on December 16 , 1991 to those <br /> obtained on March 5, 1992 and later, see Table 1 <br /> 6 <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 /> No BTEXs were detected in monitoring wells from the March 5 , and <br /> June 2 , 1992 sampling. During the previous sampling, December <br /> 16 , 1991 only MW1, MW2, and MW5, had BTEXs in very low <br /> concentrations During the September 11, 1992 sampling, sample <br /> results from MW1 detected only benzene (1 2 ug/L) and MW5 sample <br /> results detected only the xylenes (4 1 ug/L) This latest <br /> sampling (December 7, 1992) showed only MW5 to contain <br /> ethylbenzene (1 2 ug/L) and xylenes (35 ug/L) MW5 is presently <br /> being utilized as a vapor extraction well and concentrates the <br /> contaminates <br /> MAIMIUM CONTAMINANT LEVELS FOR PRIMARY DRINKING WATER, TITLE 22 <br /> or DHS. <br /> I <br /> BENZENE 1 ug/L TOLUENE 100 ug/L <br /> ETHYLBENZENE 680 ug/L Total XYLENES 1, 750 ug/L <br /> Vapor extraction has removed most BTEXs from the ground water as <br /> shown by sample results obtained from the monitoring wells since <br /> March 5, 1992 Except for MW1, which contained 1 2 ppb benzene <br /> on the September 11, 1992 sampling, the "Present California Water <br /> Quality Goals" have been met, see Table 1 <br /> Fecal Coliform <br /> From December, 1991 through February, 1992 , monthly fecal <br /> coliform samples were being collected from monitor wells MW3 , <br /> MW4 , MW5 and MW6 Sampling again occurred 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 As of <br /> June, 1992 all these wells are below detection limits, <2 2 MPN, <br /> for fecal coliform <br /> VAPOR EXTRACTION <br /> Vapor Recovery System and Monitoring. <br /> As stated in the Update Status Report #11, SB3 , SB5 , SB9 and SB11 <br /> were converted into vapor extraction wells on July 22 , 1992 <br /> (VSB3 , VSB5 , VSB9 and VSB11) Along with MW5, these wells are <br /> manifolded to a vapor extraction system with individual valved <br /> orifices for flow control and measurement from the individual <br /> wells The individual wells are fitted with a PVC tee head with <br /> a locking air tight cap, for well access The tee lateral (2 <br /> page 4 <br />