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California ,Regional Water Quality Control Board <br /> Central Valley Region <br /> Karl E. Longley,ScD, P.E.,Chair <br /> Linda S.Adams 1 1020 Sun Center Jri%c 11200,Rancho Cordova,CaliRorma 95670-61 H Arnold <br /> Serremrrfor Phone(916)464-;291 •FAX(916)464-•x645 Schwa rzenegger <br /> Ern,uromnenlu! Urnrrirr <br /> ILtp:/i\5't\'N N'BICrhOafdS.Ca.POv,`Cl'I11181\'a111'\' <br /> Prowenon <br /> 16 December 2008 <br /> Mr. John Trinkle <br /> 24551 Kasson Road <br /> Tracy, CA 95304-9518 <br /> MONITORING WELL WORK PLAN, TRINKLE & BOYS, 31244 S. HIGHWAY 33, TRACY, <br /> SAN JOAQUIN COUNTY <br /> Thank you for providing the 4 November 2008 Monitoring Well Installation Work Plan (Work <br /> Plan) prepared by Advanced GeoEnvironmental, Inc. The Work Plan proposes three <br /> monitoring wells, soil and grab groundwater samples, and to locate remnant monitoring wells <br /> by means of ground penetrating radar. This letter generally concurs with the Work Plan, while <br /> requesting some minor changes to a monitoring well location and the sampling analyses. <br /> Monitoring Wells and Sampling <br /> Proposed monitoring wells MW-4, MW-5, and MW-6 are positioned in the former operations <br /> areas and are designed to ascertain if contaminants are in shallow groundwater, and identify <br /> groundwater gradient and flow direction. Proposed MW-4 is situated between the former <br /> gravel rinse basin and the hangar, as identified on the historical facility map provided with the <br /> Work Plan Since the grab groundwater investigation conducted in May 2008 found pollutants <br /> beneath the former basin, this well location should be moved to correspond more closely with <br /> the mapped location of the gravel rinse basin. <br /> Soil samples are proposed to be obtained from selected depths of the well borings and <br /> analyzed for organochlorine compounds, organophosphate compounds, chlorinated <br /> herbicides, diuron, carbamate/urea compounds, and polynuclear aromatic compounds. Soil <br /> sampling results reported in the 7 August 2008 Limited Subsurface Investigation Report show <br /> that polynuclear aromatic compounds and organophosphate compounds are not expected to <br /> be present. Trinkle and Boys is, of course, free to perform additional analyses, but is not <br /> required to analyze samples for more than what is listed in Table 1. At least one sample <br /> should be obtained from each boring at a depth of about three feet below ground surface. If <br /> stains, odors, or other unusual characteristics are encountered in the boring, additional <br /> samples should be taken and analyzed. Some of the EPA Analytical Methods proposed are <br /> incorrect. Please note the correct method as listed inTable 1. <br /> Groundwater from the monitoring wells should be analyzed quarterly for at least one year for <br /> organophosphate compounds, carbamate/urea compounds, and volatile organic compounds, <br /> as listed in Table 1. <br /> California Environmental Protection Agency <br /> ` P"C Clell Paper <br />