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UNOCAL CORP <br /> Page 2 <br /> VW3 is upgradient of the VW2 and MW2 areas. VW3 was screened from 24 to 49 feet bsg when <br /> it was installed but currently has a total depth of 39.25 feet. Levels of MtBE in groundwater <br /> samples from VW3 in 1999 have been as high as 1300 ug/L (EPA Method 8260) and Benzene <br /> was first detected in the water sample from this well in October 1999. <br /> MtBE concentrations in groundwater samples have increased since January 1999 in MWS, MW2, <br /> MW16, MW17 and MW14 which are all down-gradient of VW3. The highest Benzene and TPH as <br /> gasoline concentrations in groundwater are from samples collected from VW7 which is screened <br /> from 55 to 60 feet bsg. MW11 (screened 52-72 feet) and PTW1 (screened 52.5-72.5 feet) the <br /> deepest down-gradient wells currently are not evidencing Benzene, TPH as gasoline or MtBE in <br /> the groundwater. MW15 (screened 18-38 feet) a shallow down-gradient well has evidenced low <br /> levels of MtBE. Remedial options for the groundwater contamination evidenced in VW7 and VW3 <br /> should be evaluated. <br /> In the summary and conclusions of the"Well Installation and Soil Boring Report" it was stated that <br /> the site was scheduled for demolition during the second quarter 2000 and that the UST system <br /> would be removed. PHS/EHD has not received a removal plan for the UST system to date. <br /> When the UST system is removed, additional information will be gathered. <br /> Vapor extraction has successfully removed some of the contamination from this site. PHS/EHD <br /> recommends continuing the"pulse" mode operation of the vapor extraction system. In addition, <br /> quarterly sampling and analysis of water samples from all the wells at the site should continue. <br /> As more information is gathered, PHS/EHD will evaluate additional requirements. <br /> If you have any questions contact me at(209)468-3449. <br /> Donna Heran, REHS, Director <br /> Environmental Health Division <br /> Margaret Lagorio, Supervising REHS <br /> Site Mitigation Unit <br /> c: SJCADA- David Irey <br /> TOSCO- Ed Ralston <br /> Gettler Ryan -Stephen Carter <br /> CVRWQCB - Marty Hartzell <br /> Dayton Hudson Corp- Dave Luick <br />