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completion have all been below detection limits. However, the December, 1997 sampling <br /> revealed minor amounts of toluene, (0.3 ug/L) and xylene, (0.9 ug/L.) Those levels are <br /> what would be expected to be seen in MW-3, which was ND. Although it appeared that <br /> the samples from MW-3& MW-4 were reversed, the testing laboratory was unable to <br /> clarify the matter since the original sample containers had been disposed of In order to <br /> determine the validity of those results,Del-Tech sent duplicate samples from this latest <br /> work to another laboratory, BSK Analytical Laboratories in Fresno The results revealed <br /> that both MW-3 and MW-4 was below detection limits, which supports our belief <br /> mentioned in the last report that the samples were reversed. The top of the well screen is at <br /> T below surface, which is above water depth. <br /> PLATES II through VI show the inferred lines of equal concentrations of BTEX& TPHg <br /> from the latest work. There does not appear to be any significant change in the shape of the <br /> plume, indicating there is little or no lateral movement. <br /> In March of this year, we discussed the project with another environmental firm, and asked <br /> them to make recommendations for cleaning up the site. Amer an intensive review, they felt <br /> that a modified "pump & treat"test would be the best way to determine cleanup options. <br /> However, the San Joaquin County EHD staff did not concur; they believed that air sparging <br /> .' was a better technique. It was pointed out that the groundwater was too shallow, and that <br /> would not be sufficient vadose zone to allow air sparging to be effective. The County staff <br /> directed that quarterly monitoring continue pending further review and analysis. <br /> We do not believe that further monitoring will serve any useful purpose. The UST and a <br /> large amount of contaminated soil have been removed, and the site filled with clean <br /> material. Four(4) monitoring wells and eleven(11) soil borings have been placed on and <br /> off the property to adequately define the limits of soil & groundwater contamination. The <br /> owners are unable to sell the property without site closure. They have complied with all <br /> directives and requirements of the County EHD, RWQCB, and Cleanup Fund staffs. We <br /> cannot justify additional staff time and money to make recommendations until we receive <br /> some guidance from the County EHD. <br /> Qu rly m toring will continue until further notice. <br /> M. rater& ociates D 0Ep�0�/ <br /> c: uis Lechich <br /> RWQCB ��'I.HUNTE <br /> No.860 <br /> OF <br /> 2 <br />