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141 V <br /> A S S O C I A T E S I N C <br /> concentration of TPHg 1n the sample from well MW7 was 2,800 parts per billion (ppb) BTEX <br /> were not detected in the groundwater samples collected from wells MW 1 through MW6 The <br /> sample from well MW7 for benzene increased to 100 ppb The samples from wells MW5 and <br /> MW7 contained the highest concentrations of MTBE at 1,500 ppb, and 84,000 ppb, respectively <br /> There appear to be correlations between groundwater elevations and MTBE concentrations in <br /> MW5 (Figure 4) and MW7 (Figure 5) MTBE was also detected in well MW6 at a concentration of <br /> 890 ppb <br /> Analytical results are summarized in Table 2 Laboratory reports with chain-of-custody documents <br /> are included in Attachment 2 <br /> RECOMMENDATIONS <br /> ATC recommends continued quarterly monitoring and sampling of all site wells (MW I through <br /> MW7) for TPHg, TPHd, and BTEX by EPA Methods 8015/8021 and fuel oxygenate additives by <br /> EPA method 8260 ATC also recommends evaluation of the vertical extent of impacted <br /> groundwater and will submit a workplan for the proposed scope of work under separate cover <br /> If you have any questions or comments regarding this project, please contact our office at (209) <br /> 579-2221 <br /> Respectfully submitted, <br /> ATC Associates Inc <br /> Mike Lukslc, R G # 7310 <br /> Staff Geologist y <br /> 4t <br /> ,s-_I',�E <br /> Jeanne Homsey, P E r,E <br /> CA Registered Civil Engineer No C47410 1 <br /> Attachments ' <br /> V3 A ' <br /> Y�' 2f=� <br /> cc Mr Jim Barton, CRWQCB ��`�,�.�,� <br /> James"J "Mills, Westrec Properties = , <br /> s lenvironmenta11625141quartlyl2gr-2003 doc 4 <br />