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r. , <br /> AkE <br /> A MA <br /> FAN <br /> Working To Restore Nature <br /> 1710 Main Street <br /> Escalon, CA 95320 <br /> Phone (209) 838-3507 <br /> FAX (209) 838-3509 r `' <br /> January 12, 1993 <br /> 0 <br /> Ms. Mary Meays <br /> San Joaquin County Public Health Services <br /> Environmental Health Division <br /> P O Box 2009 <br /> Stockton, CA 95201 <br /> RE Quarterly Monitoring Report, October through December 1992, 26056 Thornton, <br /> Road, Thornton, CA, Site Code 1864 <br /> Dear Ms Meays <br /> This letter report summarizes groundwater monitoring activities conducted by RESNA Industries, <br /> . Inc (RESNA) during the fourth quarter of 1992 at the above referenced site (Figure 1) <br /> BACKGROUND <br /> On September 6, 1989, three underground gasoline storage tanks were removed at the project <br /> site by Western Meter Service of Stockton, California Soil samples were collected beneath each <br /> tank and the associated piping The soil samples were analyzed for benzene, toluene, <br /> ethylbenzene, xylenes (BTEX), total petroleum hydrocarbons as gasoline (TPHG), tetra ethyl <br /> lead (TEL), and ethylene dibromide (EDB), by California Water Labs utilizing appropriate EPA <br /> and DHS methodologies Soil samples collected from beneath two of the tanks contained <br /> moderate to high levels of ethylbenzene and xylenes (1 2 to 70 parts per million [ppm]) as well <br /> as TPHG (470-830 ppm) <br /> f <br /> The presence of elevated concentrations of petroleum hydrocarbons in the tank pit soil samples j <br /> indicated further investigation would be required <br /> In a two phased approach beginning on November 1, 1990, RESNA personnel advanced six soil <br /> borings (MW1-MW6) to depths ranging from 27 to 30 feet below grade at the project site to <br /> accomplish the following 1) Define the lateral and vertical extent of hydrocarbon impacted <br /> soils, 2) determine soil stratigraphy, and 3) install groundwater monitoring wells within the <br /> uppermost aquifer in order to assess groundwater quality The bonnglwell locations are plotted <br /> on Figure 2 Field methodology and analytical results are discussed in detail in RESNA's <br /> 40 Interim Problem Assessment Report, dated January 13, 1992 <br /> QR121592 DRF <br />