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U4l14/Ub ] I Ul PAA Ulb Sill UUUZ UtIvir'a a mvunr. ra + <br /> is <br /> E <br /> I <br /> Public Health Service-Environmental Health Division <br /> San Joaquin County <br /> April 14, 1995 <br /> Page 2 <br /> 1 <br /> In our conversation, I presented AFPC's proposal.to provide further analytical support for <br /> our position concerning the absence of a threat to groundwater beneath the site_ You have agreed <br /> to afford AFDC the opportu dty to conduct additional testing as follows: <br /> * Installation of a groundwater monitoring well within 10 feet of the former waste oil <br /> tom; 1 <br /> Installation of two additional soil borings in locations where previous analyses <br /> reported TPH concentrations in excess of 5,000 ppm TPH; <br /> • Analysis of five soil samples for WET extractable TPH constituents(diesel and semi- <br /> volatile compounds)to evaluate the concentration and mobility of TPH remaining in <br /> soils; <br /> Evaluation of these data using geochemical modeling_ <br /> Vire believe that the groundwater level measurements will be of particular value as a means <br /> of evaluating the impact of recent rainfall on the depth to groundwater beneath the site. We are <br /> prepared to commence the above-described work immediately and to present a report on our results <br /> by July 1, 1995_ This report will include soil and groundwater analyses,modeling, and other studies <br /> required to evaluate the potential impact of TPH in soils on groundwater. An approximate time <br /> sebedule for completing the additional work is attached_ Based on the totality of the data generated <br /> through this next phase, we will mutually be in a better position to evaluate the risk presented by the <br /> site, if any, and the options for finalizing closure. <br /> As we discussed, you have approved use of the November 1994 technical work plan for <br /> additional soil sampling and monitoring well installation that was previously submitted to your <br /> offices. AFDC will apply for monitoring well and soil boring permits and attach a neap showing the <br /> proposed locations for the soil borings after the initial groundwater level data is evaluated. <br /> I <br /> snc146.1 z <br /> 1 <br /> } <br /> I <br />