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+r <br /> V 1117 Lone Palm Avenue Suite 8 <br /> ,= Modesto California 95351 <br /> VA"atc-enviro cam <br /> 209 579 2221 <br /> Fax 209 579 2225 <br /> A S S O C I A TSE S I N C <br /> f � - <br /> - r <br /> ENVIRONMENTAL HEALTH DIVISION <br /> 304 E Weber Ave Third Floor <br /> March 1, 2001 P O Box 388, Stggkton CA 9520 -0388 <br /> Approved <br /> Dented <br /> 9 <br /> Conditio s ' <br /> Mr Harlin Knoll C&Xl t a.e, a_&K �" <br /> San Joaquin County Public Health Se ice ate by <br /> Environmental Health Division 6-0 - <br /> 304 E Weber Ave , Fourth Floor be) tt [� S �PJs�D C( titStock <br /> Stockton, CA 95201-03$8 , <br /> Subject Fourth Quarter 2000 Groundwater Monitoring Report and Workplan for <br /> Groundwater Extraction Pilot Test for 26056126080 Thornton Road, Thornton, <br /> CA, Site Code 1864 <br /> Dear Mr Knoll <br /> This report summarizes field activities conducted during the Fourth Quarter 2000 by ATC <br /> Associates Inc at the subject site (Figure I) Additionally, this letter presents ATC's workplan <br /> for a groundwater extraction pilot test at the subject site, per your request <br /> BACKGROUND <br /> On September 6, 1989, Western Meter Service of Stockton, California removed three <br /> underground gasoline storage tanks at the project site Soil samples were collected beneath each <br /> tank and the associated piping 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 total petroleum hydrocarbons as gasoline (TPHg) at 470 to 830 ppm <br /> Due to the presence of elevated concentrations of petroleum hydrocarbons in the tank pit soil <br /> samples, further investigation was required by San Joaquin County Public Health Services, <br /> Environmental Health Division (PHS/EHD) <br /> In a two-phased approach beginning on November 1, 1990, RESNA Industries Inc personnel <br /> advanced six soil borings (MW1 through MW6) to depths ranging from 27 to 30 feet below <br /> grade at the project site to accomplish the following 1) define the lateral and vertical extent of <br /> hydrocarbon impacted soils, 2) determine soil stratigraphy, and 3) install groundwater <br /> monitoring wells within the uppermost aquifer in order to assess groundwater quality The <br /> boring/well locations are plotted on Figure 2 Field methodology and analytical results are <br /> discussed in detail in RESNA's Interim Problem Assessment Report, dated January 13, 1992 <br /> The site's station building and garage were demolished in December 1994 to facilitate corrective <br /> action activities including the removal of hydrocarbon contaminated soil that was present <br /> w 1625821quart1yl4gr-2000 doc 1 <br />