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in all wells In general, there has been significant improvement in contaminant concentrations since <br /> high levels were encountered in October 1996 <br /> 5.0 CONCLUSIONS AND RECOMMENDATIONS <br /> Contrary to typical observations at most sites, the degree of groundwater contamination remains <br /> low, even though the static water level is relatively high Normally, seasonal rises in the <br /> groundwater table are accompanied by an increase in the degree of contamination as water comes <br /> into contact with residual contamination trapped in the vadose zone and/or capillary fringe Both <br /> sampling events since October 1996 have found that diesel concentrations have declined, but the <br /> principal reason may be that the water level is above the well screen in three wells and the samples <br /> are not truly representative of the water column. In the three most reliable wells (GT-5, GT-6, and <br /> GT-9), concentrations remain below dection limits in one, have declilned in another, and risen in <br /> the third These results cannot be confidently interpreted on the basis of the few samples that have <br /> been obtained from these wells Therefore, we recommend that groundwater monitoring be <br /> continuted on a regular quarterly basis in 1998 so that any patterns or trends may be identified <br /> At the present time, it is not possible to determine whether contaminant concentrations have <br /> increased, decreased, or remained unchanged, nor is it possible to determine whether <br /> contaminantion is migrating Hence, we conclude that it would be premature to prepare a <br /> Corrective Action Plan or perform any remedial work We recommend that this step be postponed <br /> • until such time as more definitive trends in contaminant concentrations have been established <br /> 4 <br />