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y �-� � ���v- ��(� �- �« fir""'�'�`+"q '� � y_ F'pa, �ve�-.'- _ irz"✓•'::�i _ *exnar,�:�a� <br /> r - r <br /> r= <br /> WATtRWORK <br /> GEOCHEMICAL0 GEOTECHNICAL+ENVIRONMENTAL <br /> August 16, 1988 <br /> AUG "4 W8 <br /> Mr. David Car is ENVIRuMENiAL HEALTH <br /> San Joaquin Local Health District PERMITAMICES <br /> 1601 East Hazelton Avenue <br /> Stockton, CA 95201 <br /> Re: Tri/Valley Growers Facility, 26200 Howell Road, <br /> Thorton, California. <br /> Dear Mr. Carts: <br /> As required by the San Joaquin Local Health District (condact <br /> this letter outlines our proposed methodology <br /> additional site investigations at the above referenced site <br /> (Figure 1) . previous investigations at the site have included <br /> t6ze removal of underground fuel storage tanks, soil sampling of <br /> tank pits and excavated materials, installation and sampling of <br /> four monitoring wells and sampling of a nearby domestic well. <br /> In February, 1987, subsequent to removal of a 5,000 gallon and <br /> 10,000 gallon underground (u/g) tank, sampling of soils and <br /> groundwater within the tank pit recorded the presence of <br /> hydrocarbon contamination (Figure 2). As a result, Exceltech, <br /> Inc. conducted a alte investigation on behalf of Tri/Valley <br /> Growers and issued a report dated November 9, 1987 entitled "Soil <br /> and Groundwater Investigation for Tri/Valley Growers, Plant T" <br /> which contained results of the investigation and recommendations <br /> for further work. The report indicated that no petroleum <br /> hydrocarbon contamination was detected in any of three newly <br /> installed groundwater monitoring wells. It was reported that "It <br /> appeared that the initial excavation appears to have removed much <br /> of the contamination". However, since none of the three wells <br /> were located down gradient of the suspected source relative to <br /> the northeasterly groundwater flow direction, the possibility <br /> existed that a contamination plume had moved in that direction. <br /> Subsequent to review of the assessment report, SJLHD requested <br /> that an additional monitoring well be installed down gradient (to <br /> the northeast) . Additional investigations were conducted by <br /> Exeltech and presented in a March, 1988 report entitled "Report <br /> of Monitoring Well Installation, Sampling and Analysts for <br /> Tri/Valley Growers". The report indicated the following iesults: <br /> 1. Laboratory testing of a groundwater sampling from the newly <br /> --installed,-- --(down - gradient)- ...monitor Ing._ well (MW4) detected <br /> concentrations of benzene and toluene above Departmen o ea <br /> Services (DHS) action levels. <br /> 2. No hydrocarbon contamination of soil was detected in samples <br /> from MW4. <br /> 1710 MAIN STREET • ESCALON.CA 95320 • (209)838-3507 <br /> FRESNO,CA(209)222-3495 • SAN LUIS OBISPO,CA(605)544-6586 + RENO,NV(702)788-6830 <br />