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t _ <br /> 8720019-1 CON-5 <br /> during the May 19 sampling noted a hydrocarbon smell while purgi-ng MW-17 <br /> but not MW-18. It is apparent that the sample results were transposed <br /> during reporting at the laboratory. The lab was contacted but could not <br /> confirm or discount the possibility. Subsequently, the second set of <br /> samples was taken on September 14, 1987 which found TPH levels of 1.0 mg/L <br /> and non-detectable for MW-17 and MW-18 respectively. This would appear to <br /> confirm the supposition that previous results were transposed. For the <br /> purposes of this report it is assumed that they were transposed and are <br /> presented in their correct form in Table 1. The current hydrocarbon levels <br /> in MW-17, with a few exceptions, have shown a continuing decrease from the <br /> initial levels encountered following installation. No contamination other <br /> than 3 ug/L ethyl bezene was detected in MW-18 during any of the sampling <br /> efforts. <br /> RECOMMENDATIONS <br /> Based on the results of the sample analyses and observations made during <br /> excavation, we recommend that no further remedial actions be taken at the <br /> site in association with this incident. It is apparent that only a minor <br /> amount of soil contamination remains, and the relatively low levels of <br /> groundwater contamination are restricted to the immediate vicinity of the <br /> tank area. The continued absence of detectable hydrocarbons in MW-18 <br /> suggests that downgradient contaminant migration is minimal or <br /> nonexistent. In addition, the decrease in contaminant levels in MW-17 <br /> could indicate that natural degradation is occurring, although the decrease <br /> is within standard laboratory margin of error. Further support of the no- <br /> action recommendation is provided by the fact that the groundwater <br /> downgradient of the spill has already been contaminated with DBCP by <br /> Occidental Chemical Company, the previous owners of the adjacent pesticide <br /> and fertilizer facility. This water is currently not recommended for any <br /> domestic, agricultural or industrial uses and is anticipated to remain as <br /> such in the foreseeable future. <br /> -7- <br />