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4 <br /> WEISS ASSOCIATES Consulting in Geology 6 Geohydrology <br /> 1 <br /> 2938 McClure Street, Oakland, CA 94609 415-465-1100 <br /> May 16, 1989 (( \ U <br /> V �A <br /> Mc Richard O. Norona gg <br /> Diamond Walnut Growers, Inc. <br /> P.O. Box 1727 <br /> Stockton, CA 95201 <br /> Re: Tank Investigation <br /> 1050 South Diamond Street <br /> Stockton, California <br /> WA Job #74-331-03 <br /> Dear Mr. Norona: <br /> This letter presents Weiss Associates'(WA)proposed Scope of Work(SOW) for additional <br /> soil boring and sampling at the Diamond Walnut Growers (DWG) walnut processing plant in <br /> Stockton, California. The results of the WA Phase I subsurface investigation conducted in <br /> December 1988 indicated: <br /> • Ethylene and/or propylene glycol concentrations in native soil beneath Tanks 1 <br /> and 6 exceeded 1,000 parts per million (ppm). <br /> • Hexavalent chromium concentrations in soil beneath Tank 8 slightly exceeding <br /> California Department of Health Services (DHS) Soluble Threshold Limit <br /> Concentrations (STLC). <br /> • Calcium and chloride in soil beneath Tank 8 were higher than estimated <br /> background concentrations of these compounds in native soil. <br /> The objective of this Phase 11 investigation is to determine the vertical extent of the <br /> released chemicals beneath Tanks 1, 6 and 8, and the potential for ground water quality <br /> degradation from these chemicals. Our recommended SOW for the investigation is to: <br /> I) Determine the present and historic depth to ground water beneath the site. <br /> 2) Determine the extent of the released chemicals in soil by drilling additional <br /> borings adjacent to and beneath each tank and collecting and analyzing soil <br /> samples. <br /> 3) Report the results. <br /> Each of these tasks is described below. <br /> A Division or AguaTwrta Associates Incorroialed <br />