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. from year to year and transports the hydrocarbons in the process Despite this continuous <br /> movement, which is almost certainly intertwined with changes in the groundwater flow <br /> direction, there has been no obvious migration of the hydrocarbon plume during the several <br /> years that it has been monitored None of the monitoring wells provides any evidence that <br /> concentrations have increased steadily over time or that the plume has migrated in any <br /> particular direction Therefore, in view of these observations and the lack of identifiable <br /> remedial options, we recommend that groundwater monitoring be reduced to annually (first <br /> quarter, when concentrations tend to peak) for the foreseeable future, and that further <br /> investigation be dropped from further consideration <br /> 7) In the past, PHS/EHD has expressed concern over the detection of diesel fuel in the Gillies <br /> domestic well, and suggested that the well be abandoned and replaced with a deeper well <br /> We suggest a less costly remedy Only one-fourth of the samples collected at the outlet <br /> from this well have contained detectable concentrations of hydrocarbons, and only one had <br /> a diesel concentration in excess of 500,ppb Furthermore, this well is used by Gillies <br /> Trucking only in the employee restrooms, it is not used for drinking water Hence,wellhead <br /> treatment with granulated activated carbon would be a cost-effective method of removing <br /> any hydrocarbons that may occasionally be drawn into this well, and it is likely that a single <br /> carbon canister would last many months before breakthrough The cost for this type of <br /> treatment would be only a few hundred dollars per year, as opposed to many thousands of <br /> dollars to abandon the existing well and replace it No hydrocarbons have been detected in <br /> any of the samples from the domestic well on the former Barbot property next door, and <br /> . this well is not in any immediate danger from the diesel plume There is no need to treat or <br /> replace this well, but if it will not be returned to active use it would he advisable to have it <br /> properly abandoned in accordance with County regulations <br /> i <br /> 9 <br />