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PUBLICHEALTH SERVICES <br /> SAN JOAQUIN COUNTY ' <br /> ENVIRONMENTAL HEALTH DIVISION <br /> Karen Furst, M.D., M.P.H., Health Officer <br /> 304 East Weber Avenue,Third Floor • Stockton, CA 95202 <br /> 209/468-3420 <br /> PAUL VAN DYKEN FEB O 8 2002 <br /> N&S IRRIGATION <br /> P O BOX 805 <br /> RIPON,CA 95366-0805 <br /> Site Code: 1474 <br /> Re: N& S Irrigation, 215 West Main St., Ripon, CA <br /> San Joaquin County Environmental Health Department (EHD) has reviewed the "Summary Report of <br /> Supplemental Subsurface Investigation" dated January 4,2002,prepared by ATC Associates Inc. <br /> Soil samples taken at 20-25 feet below grade (see Table 1) did not indicate detectable concentrations of <br /> total petroleum hydrocarbons as gasoline (TPHg), benzene, toluene, ethylbenzene, and xylenes (BTEX) <br /> or fuel oxygenates including methyl tertiary butyl ether (MTBE). Soil samples were collected and <br /> analyzed from soil probes SB7, SB8, S139, S13 10, S1311, and SB 12 to investigate the vertical and lateral <br /> extent of contamination. The well survey included in the report documents one operating well, four <br /> monitoring wells, and one off-line well within the 2,000-foot radius. The closest well is 300 feet north <br /> of the site and is in operation by the City of Ripon, it is located in the downgradient direction. <br /> Water samples were obtained and analyzed from S137 through SB 12 and CPT 1. Sample results from first <br /> encountered groundwater did not indicate detectable concentrations of TPHg, BTEX, or fuel oxygenates <br /> including MTBE. <br /> Maps in the report show the estimated lateral and vertical extent of contamination. The shallow lateral <br /> extent of contamination appears to be defined north, west and south of the site. There are no lateral <br /> downgradient soil borings or wells northeast of the former underground storage tank(UST)location. To <br /> further define the lateral and vertical extent of contamination, EHD recommends a minimum of one well <br /> downgradient of the former UST location and any other sources of contamination that are found. <br /> During an inspection of the performance of the soil probes in September 2001, EHD staff discovered a <br /> fill pipe to a UST located west of the restaurant located on this property. If this UST was not previously <br /> properly closed, it must be properly closed now under permit and inspection of EHD Unit III staff. <br /> Through discussions with your consultant about this UST it was disclosed that this portion of the <br /> property had previously been an operating service station. This may explain the groundwater <br /> contamination evidenced in MW3 which is upgradient of the UST's removed in March 1990. In a letter <br /> dated January 26, 2001, EHD requested an explanation for contaminant concentrations being highest in <br /> MW 1, which is crossgradient of the UST's removed in March 1990. This explanation was not provided. <br /> The past uses and possible sources of contamination at this site should be investigated in order to <br /> evaluate and explain contaminant levels found upgradient and crossgradient of the UST's removed in <br /> March 1990. The location of the UST's operated when there was a service station at the site should be <br /> shown on the site map. <br /> A Division of San Joaquin County Health Care Services <br />