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TABLE IV shows the results of water samples from MW-4, which is approximately 150 <br /> feet downgradient from the removed UST. There was no soil or groundwater contami- <br /> nation measured during the work, and four sampling events since completion have all been <br /> below detection limits, However, the latest sampling in December, 1997 revealed minor <br /> amounts of toluene, (0.3 ug/L) and xylene, (0.9 ug/L.) These levels are what would be <br /> expected to be seen in MW-3, (see TABLE III,) which was ND. Although it appears 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. We are <br /> reluctant to accept those results without further confirmation. <br /> PLATES H through VI show the inferred lines of equal concentrations of BTEX & TPHg <br /> from the latest work, assuming that the analyses from MW-4 is correct. This would <br /> indicate that the plume has migrated downgradient over 100 feet in six months, an unlikely <br /> scenario based on prior data. The next quarterly sampling event, due in March, should <br /> clarify the matter. <br /> We have investigated the use of ORC compound for reducing levels of contamination, but <br /> there is considerable disagreement about the effectiveness of the procedure. Disposal is a <br /> problem, and long-term results are uncertain. We are evaluating other methods, and hope <br /> to have a proposal for your review& comment within the next 60 days. However, we <br /> believe it advisable to delay any remediation project until the results of the next sampling <br /> event a av ' ble. <br /> W . J anter &Associates <br /> cc: QCB <br /> George Lechich <br /> N GE <br /> .61 <br /> WLLIAM}.HUNTER <br /> APass Ir!9? <br /> NO.860 <br /> P <br /> sT9�OF CAL1F�`�` <br /> �A) <br /> 2 <br />