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• The iithology beneath the site varies from silty clays & stickly blue clays to very <br /> silty clayey sands. MW-3 is downgradient from the site of the UST's & pump <br /> island; it has never revealed any petroleum hydrocarbons in soil or water samples. <br /> • The hydraulic gradient is very low at approximately .003'/ft.; it has been <br /> consistently to the northwest. The potentiometric surface has ranged from an <br /> average of 6.86' bgl in January, 1997, to 9.24' in September, 1998. The results of <br /> the four samplings are tabulated below for your information. <br /> Depths to water from four onitoring events <br /> DATE MWA MW-2 MW-3 JAVERAGE <br /> 10-96 8.39' 8.62' 8.27' 8.43' <br /> 1-97 6.82' 7.05' 6.71' 6.86' <br /> 6-97 8.08' 8.28' 7.96' 8.11' <br /> 9-98 9.20' 9.45' 9.08' 9.24' <br /> Average 8.12' 8.35' 8.01' 8.16' <br /> Max. Chane 2.38 2.40' 2.37' 2.38' <br /> • Available data indicates that domestic wells in the area are screened below 80 <br /> feet due to insufficient aquifers above that depth. There are no wells located <br /> within 100 feet of the source of contamination. <br /> Based upon all of the evidence collected to date as detailed above and in prior <br /> reports, the minor amount of contamination remaining beneath this site is restricted to <br /> a small area beneath and adjacent to the existing building. The contamination in the <br /> soil and groundwater have not migrated more than 30 feet from the source, which is <br /> due to the very low transmissivity of the sediments and the very shallow hydraulic <br /> gradient. Therefore, we believe that there is no present or future threat to <br /> potable water supplies from this site, and we continue to recommend that the <br /> si'te/b, los <br /> 4 <br /> f�(J <br /> Wm. J. unter <br /> W . . Hunter &Associates � aV-D GE <br /> cc: California Welding Supply �S 0e,�, <br /> Mark List, RWQCB �`` �.hu iiER <br /> G�a1u�a f�19q <br /> * <br /> NO.8W <br /> SJ, P <br /> A�OF CA�ZF�`�t�` <br /> 2 <br />