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Mr Harlin Knoll <br /> Page 2 <br /> I <br /> at concentrations of 61 ppb, 4 2 ppb, 55 ppb, 95 ppb, and 2,200 ppb, respectively Wells MW3, <br /> MW4, and MW8 contained low levels of gasoline constituents Most notably, benzene was <br /> detection at 13 ppb, 12 ppb, and 8 2 ppb, respectively TPHG was detected in wells MW3 and <br /> MW4 at 75 ppb and 52 ppb, respectively No TPHG was detected in well MW8 MTBE was <br /> detected in wells MWI, MW3, and MW4 at 7 ppb, 6 ppb, and 7 ppb, respectively No MTBE <br /> was detected in wells MW5 or MW8, although the detection limit in well MW5 was elevated to <br /> 50 ppb due to sample dilution Analytical results are summarized in Tables 2 and 3 Laboratory data <br /> sheets and chain of custody documentation are included in Attachment B Figure 3 shows the <br /> estimated extent of dissolved benzene in groundwater <br /> RECOMAIEENDATIONS <br /> MTBE was detected in wells MWI, MW3, and MW4 at 7 ppb, 6 ppb, and 7 ppb, respectively in <br /> February 1998 In the previous quarter(November 1997)MTBE was detected only in well MWI at 5 <br /> ppb MTBE has not been detected in three sampling events (February 1996, <50 ppb, November <br /> 1997, <5 0 ppb,February 1998, <50 ppb)in well MW5 The recommended cleanup goal (Department <br /> of Health Services California State Action Level) for MTBE is 35 ppb Based on this information, <br /> Ground Zero recommends discontinuing analysis of groundwater samples for oxygenate compounds <br /> The next quarterly monitoring and sampling is scheduled for May 1998 and will include morntoring <br /> . depth to water in all site wells, purging and sampling wells MWI, MW4, MWS, and MW8, and <br /> analyzing samples for TPHG and BTEX <br /> Ground Zero also anticipates conducting further investigation of the vertical and lateral extent of soil <br /> contamination in the vicinity of well MW5 at the request of PHS/EHD in anticipation of a request for <br /> closure of the site A workplan will be submitted under separate cover <br /> I <br /> gmundw\knowles hwnVeportsllgmi998 doe <br />