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*4W" NNW <br /> ENVIRONMENTAL HEALTH DEPARTMENT <br /> SAN JOAQUIN COUNTY <br /> Donna K.Heran,R.E.H.S. Unit Supervisors <br /> Director 304 East Weber Avenue, Third Floor Carl Borgman,R.E.H.S. <br /> W' <br /> Al Olsen,R.E.H.S. -2,708 Mike Huggins,R.E.H.S.,R.D.I. <br /> Stockton, California 95202 Douglas W.Wilson,R.E.H.S. <br /> Program Manager <br /> Laurie A.Cotulla,R.E.H.S. Telephone: (209) 468-3420 Margaret Lagorio,R.E.H.S. <br /> Program Manager Fax: (209) 464-0138 Robert McClellon,R.E.H.S. <br /> Mark Barccllos,R.E.H.S. <br /> DARIN ROUSE APR 01 2005 <br /> CHEVRON TEXACO ENVIRONMENTAL MANAGEMENT COMPANY <br /> P 0 BOX 6004 <br /> SAN RAMON CA 94583-0804 <br /> RE: Chevron Service Station 9-1452 <br /> 334 East Main Street <br /> Ripon, California <br /> San Joaquin County Environmental Health Department (EHD) has reviewed Work Plan for <br /> Additional Assessment, dated November 24, 2004, and Work Plan for Additional Assessment, dated <br /> January 19,2005, both prepared by Secor International Incorporated(Secor) on your behalf. <br /> EHD comments on the work plan dated November 24,2004, as follows: <br /> It is Secor's opinion that the vertical extent of contaminant impacts to soil and groundwater in the <br /> apparent source area is defined. EHD does not concur with this conclusion. Grab groundwater <br /> sample analytical results from the deepest boring on site, cone penetrometer test boring CPT-1, show <br /> a general increase for methyl tertiary-butyl ether (MTBE) and methanol at total depth of 116 feet <br /> below ground surface (bgs). MTBE was detected at 13 micrograms per liter(gg/L) and methanol was <br /> detected at 350 gg/L. Also, the analytic*rlesults from soil samples collected from the deepest boring, <br /> monitoring well MW-5D, show the presence of methanol at 3.5 milligrams per kilogram (mg/kg). <br /> Additional assessment is needed to delineate the vertical extent of contamination in soil and <br /> groundwater at this site. <br /> Secor proposes to install two monitoring wells off-site; however, the aerial map showing the two <br /> locations for the proposed wells is not specific as to the exact locations. Please submit an addendum <br /> to this work plan by June 20, 2005, showing specific locations for the two wells along with the <br /> technical justifications for these locations. If the wells are to be placed on private parcels, an access <br /> agreement will be needed from the prospective property owners. Please indicate whether the soil <br /> samples will be continuously logged or logged at five-foot intervals; and note that San Joaquin <br /> County Public Health Services Environmental Health Division Well Standards, Section 4.7, states <br /> that bentonite may be used not to exceed five percent of the volume for the bentonite-cement grout <br /> mixture. <br /> EHD agrees that Secor should approach Nestle Foods Corporation (Nestle) and request access to <br /> sample monitoring wells that are screened at approximately 20 to 40 feet bgs, or utilize Nestle <br /> sampling data to assess the contaminant impacts southwest of the Chevron Station. Please proceed <br /> with this investigation immediately. <br />