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• 4.0 CONCLUSIONS AND RECOMMENDATIONS <br /> The investigations conducted to data have documented diesel <br /> contamination of the groundwater beneath the site. The newly <br /> developed data indicates that a small plume of dissolved diesel <br /> hydrocarbons with concentrations below state DOHS .Action levels <br /> for drinking water exists on-site. <br /> The minor diesel contamination detected in the groundwater is <br /> well below the designated level to protect groundwater of 1,000 <br /> ppb. It is reasonable to expect natural biodegradation to # <br /> remediate such low levels of dissolved hydrocarbons. However, it <br /> cannot be determined at the present level of knowledge if the ; <br /> plume may simply not have reached the downgradient wells. In <br /> order to monitor the chemical levels in the water bearing zone <br /> while assuring that no significant expansion of plume size occurs <br /> we propose that a quarterly ,monitoring= and-,.,sampling:.7 program,;-be. <br /> initiated. Wells will be monitored and then purged until p1l, <br /> Hw temperature and electrical conductivity stabilize. All purged R <br /> " water will be contained on-site until laboratory results are <br /> received. At such time, treatment and disposal alternatives will <br /> be evaluated. The water samples .will be collected per WaterWork <br /> water sampling protocol (Appendix IV) and analyzed for BTEX and <br /> TPH as gasoline and diesel. A gradient map will he prepared from <br /> the water level data. <br /> s <br /> If quarterly monitoring shows plume migration or an increase in <br /> hydrocarbon levels, further investigation and possible initiation <br /> of a remediation program involving hydraulic control can be <br /> implemented. <br /> t <br /> 3 <br />