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. RESULTS <br /> Water levels have decreased an average of 0 47 feet since the last monitoring event in October 1995 <br /> (Table 1) A groundwater gradient map was created using the data collected on August 29, 1997 <br /> (Figure 2) Groundwater flows northeast, away from the slough, with a gradient of approximately 0 07 <br /> feet/foot or 396 feet per mile <br /> No petroleum hydrocarbon constituents were detected In the groundwater samples collected from <br /> wells MWI through MW4 Well MW5 contained benzene and xylenes below the State Maximum <br /> Contaminant Levels (MCLS) and TPHg at a concentration of 80 parts per billion (ppb) The samples <br /> from wells MW5 and MW6 contained MTBE at concentrations of 4,100 ppb and 34 ppb, respectively <br /> No other oxygenate fuel additives were detected in any wells sampled Analytical results are <br /> summarized in Table 2 Laboratory reports with chain-of-custody documents are included in <br /> Attachment 2 <br /> RECOMMENDATIONS <br /> Due to the elevated concentrations of MTBE in the groundwater sample from well MW5, Smith <br /> Technology recommends monitoring and sampling of all site wells (MW 1 through MW6) for TPHg, <br /> BTEX, and oxygenate fuel additives during the fourth quarter of 1997 to confirm that fourth quarter <br /> results are consistent with third quarter results <br /> If you have any questions or comments regarding this project, please contact our office at (209) 579- <br /> 2221 <br /> Respectfully Submitted, <br /> Smith Technology Corporation(ATC Associates) <br /> D n I -- AV- <br /> Drew Van Allen <br /> Staff Scientist o�gp�ESSf�j,�q� <br /> JEANNE F2�, <br /> HORSEY m <br /> Jeanne Homsey N0. CO47410 <br /> CA Registered Civil Engineer No C47410 Exna —L&474-- <br /> Attachments d'T9 CIVIL >>Q <br /> lF OF C�1-���� <br /> cc CRWQCB <br /> Robert Taylor, Westrec Marmas <br /> w 162514 uanI)�9f-199'7 doc 2 <br /> 19 <br /> shun <br />