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• App/ied GeoSystems 43255 Mission Blvd. Suite B Fremont, CA 94539 (415)651-1906 <br /> July 17, 1987 <br /> AGS Job 87031-2, <br /> 87050-2 <br /> 0717RNIB <br /> Mr. Robert Niblack <br /> California Regional Water Quality Control Board <br /> Central Valley Region <br /> 3443 Routier Road <br /> Sacramento, CA 95827-3098 <br /> Subject: Work plans for contaminant distribution delineation, <br /> USA Station #110 , 2132 East Mariposa Road, Stockton, <br /> and Hydrocarbon contaminant delineation and <br /> hydrogeologic characterization, USA Station #65, 2500 <br /> West Lodi Avenue, Lodi, California. <br /> Mr. Niblack: <br /> • In confirmation of our phone conversations of July 16 and 17 , <br /> 1987, Applied GeoSystems makes the following revisions to the <br /> work plans previously submitted for these sites . These revisions <br /> reflect verbal agreements made in order to make the proposed <br /> programs effective in delineating hydrocarbon concentrations at a <br /> minimum cost to USA Petroleum Company. <br /> As previously stated, all soil samples collected will be <br /> evaluated using a field photoionization hydrocarbon detector <br /> (Photovac TIP) . At least one sample from each boring, taken at <br /> the lowest sample interval above the ground water surface, will <br /> be analyzed for total volatile hydrocarbons (TVH) and the <br /> volatile hydrocarbon constituents benzene, toluene, ethylbenzene, <br /> total xylenes (BTEX) . In addition, the soil sample from each <br /> boring which shows the highest reading on the TIP will also be <br /> analyzed for TVH and BTEX. Thus each boring will have a minimum <br /> of one and a maximum of two soil samples analyzed. Normally the <br /> sample immediately above the ground water surface will show the <br /> highest hydrocarbon concentrations . <br /> Selected samples will be analyzed for TVH and BTEX by EPA Methods <br /> 8020 ( soil) and 602 (ground water) . These methods are suitable <br /> and appropriate for sites where gasoline is judged to be the <br /> major contaminant present. Since a diesel tank is present at the <br /> • Stockton site, selected samples will also be analyzed by the <br /> modified EPA Method 8015 for total extractable hydrocarbons <br /> (TEH) . All soil samples will be frozen and stored for a minimum <br /> of 30 days after collection. This will allow for later <br /> additional analyses if necessary on the basis of new data. <br />