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41 <br />;H <br /> v o <br /> r• A S S O C I A T E S I N C <br /> RESULTS <br /> Water levels have decreased an average of 129 feet since the last monitoring event on March 4, <br /> 1999 (Table 1) A groundwater gradient map was created using the data collected on June 9, 1999 <br /> (Figure 2) Groundwater flows northeast, away from the slough, with a gradient of approximately <br /> 0 07 feet/foot or 370 feet per mile <br /> No petroleum hydrocarbon constituents were detected in the groundwater samples collected from <br /> wells MW1, MW3, and MW4 TPHg, and BTEX were not detected in any of the groundwater <br /> samples The samples from wells MW5 and MW6 contained TPHd at concentrations of 120 parts <br /> per billion (ppb) and 160 ppb, respectively, but was reported as an unidentified hydrocarbon The <br /> samples from wells MW2, MW5, and MW6 contained MTBE at concentrations of 3 5 ppb, 20,000 <br /> ppb, and 52 ppb, respectively Analytical results are summarized in Table 2 Laboratory reports <br /> with chain-of-custody documents are included in Attachment 2 <br /> RECOMMENDATIONS <br /> Due to the detectable concentrations of MTBE in the groundwater sample from wells MW2, MW5, <br /> and MW6, ATC recommends continued monitoring and sampling of all site wells (MW1 through <br /> MW6) for TPHg, TPHd, BTEX, and MTBE by EPA Methods 8015/8020 <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 /> Ate► <br /> 4, <br /> Drew Van Allen <br /> Staff Scientists ; :Sf � <br /> H0S'EY <br /> Jeanne Hornsey�'� ;;�� i;0 U'14 1:'1110 <br /> � <br /> CA Registered Civil Engineer No C47410 UP <br /> t CIVIL <br /> AttachmentsOT <br /> ; <br /> cc CRWQCB <br /> AD James"J " Mills, Westrec Properties <br /> w 1625141quart1yl2gr-1999 doe 2 <br />