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0 <br />rJ <br />KENNETH D. SCHMIDT AND ASSOCIATES <br />GROUNDWATER QUALITY CONSULTANTS <br />Mr. Harold F. Grinde <br />April 10, 1986 <br />Page 2 <br />Sampling Existing Wells <br />Shallow strata possibly affected by gasoline from the two <br />tanks are apparently sealed off in all three factory wells. <br />However, as a precaution, water samples should be collected from <br />each of these wells during a heavy pumping period and analyzed <br />for benzene, toluene, and xylene. Each well would be pumped for <br />at least several hours prior to collecting a water sample for <br />laboratory analysis. California Analytical Laboratories, Inc. <br />of Sacramento would analyze the samples by EPA Method 602 <br />(modified). Samples would be collected in duplicate glass vials, <br />with no air bubbles, and kept cool until analysis. Chemical <br />analyses of water samples collected from these three wells in <br />September 1985 all indicated less than 0.01 mg/l of lead. Total <br />organic carbon contents were all less than 3.0 mg/1, considered <br />normal for unpolluted groundwater in the area. Chain -of -study <br />procedures would be followed for all water samples collected <br />during this investigation. Samples for trace organic chemicals <br />would be delivered to the laboratory the same day as they are <br />collected. There are no other wells close enough to have been <br />impacted by gasoline from these two tanks. <br />New Monitor Wells <br />Three shallow monitor wells should be drilled within 70 feet <br />of each tank. The attached map shows the proposed locations for <br />these wells. The wells would be drilled so as to tap at least <br />five or ten feet of the shallowest permeable strata (sand) at <br />each site. The wells would be drilled by the air -rotary method <br />and the drill cuttings logged by a geologist. Drill cuttings <br />would be carefully observed for any hydrocarbon odor. If <br />noticeable odors are present, samples of the drill cuttings would <br />be taken (at five foot depth intervals) and placed in open- <br />mouthed glass containers for analyses of benzene, xylene, and <br />toluene. The samples would be kept cool until analyzed. <br />California Analytical Laboratories, Inc. would analyze the <br />samples by EPA Method 8020 (modified). Drill cuttings for the <br />wells near the leaded tank site would be analyzed for lead, at <br />five-foot depth intervals. BC Laboratories, Inc. of Bakersfield <br />would perform the lead analysis. <br />Five -inch diameter 160 psi PVC would be used for the well <br />casing. The casing would be perforated from five feet in depth <br />to the bottom, and the annular space gravel packed. The annular <br />space above the gravel would be then sealed with cement. A steel <br />protective casing (8 -inch diameter) would be installed at the <br />surface to protect the PVC. Each well would be developed by <br />air -lifting. If no hydrocarbon odor is detected, a portable <br />