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I <br /> PUBLIC HEALTH SERVICES <br /> SAN JOAQUIN COUNTY <br /> N: < <br /> JOG[KHANNA M.D,M.P.H. <br /> Health Officer , P. <br /> P.O. Box 2009 0 (1601 East Hazelton Avatue) 0 Stockton, California 95201 <br /> 4Cf FGR <br /> (209) 468-3400 <br /> CLINT ROGERS J(/ <br /> ENVIRONMENTAL ENGINEER l <br /> CHEVRON USA INC <br /> P O sox 5004 FEE 17 1993 <br /> SAN RAMON CA 94583 - 0804 <br /> RE: Chevron Service Station #9-1918 SITE CODE: 1138 <br /> 45 East Harding Way <br /> Stockton CA 95204 <br /> San Joaquin County Public Health Services Environmental Health Division (PHS/EHD) <br /> has completed review of the "Work Plan for Soil and Groundwater Assessment" dated <br /> December 15, 1992 and the "Work Plan Addendum" dated February 1, 1993, both <br /> prepared by Groundwater Technology. PHS/EHD has the following comments for your <br /> consideration. <br /> The work plan proposed the installation of two additional monitoring wells to assess the <br /> extent of soil and groundwater contamination. PHS/EHD agrees that a well <br /> downgradient of MW11 is necessary to further define the extent of groundwater <br /> contamination. PHS/EHD also agrees that the groundwater contamination noted before <br /> groundwater dropped below the screened interval of MW5 (2,300 ppb benzene) and of <br /> MW6 (5 ppb benzene) warrants additional investigation. The work plan proposed a <br /> deeper monitoring well to replace MW5 and MW6. <br /> The work plan indicated that soil samples would be collected every five feet and at a <br /> minimum, the soil sample collected at 30 feet would undergo laboratory analysis. <br /> PHS/EHD agrees that analysis of the soil sample collected at 30 feet would further <br /> characterize soil contamination, since soil contamination, at that approximate depth, had <br /> been detected during the installation of MW5 and MW6. However, additional soil <br /> sample analysis may be necessary to adequately characterize possible soil contamination <br /> which may have resulted from leaking underground storage tanks or from the disposition <br /> of contaminants from water to soil which may have occurred as the groundwater level <br /> lowered. <br /> A Division of San Joaquin County Halth Cue Se cm 40 <br />