Laserfiche WebLink
Draft Final ROD Memorandum -4- 22 December 1992 <br /> DDRW, Sharpe <br /> Definition of Environment <br /> In general , under the Comprehensive Environmental Response, Compensation and <br /> Liability Act (CERCLA) , the health-based Risk Assessments are used to establish <br /> the aquifer cleanup levels for the primary ground water contaminants of concern. <br /> The <br /> health-based Risk Assessments usually only evaluate human health risks and as a <br /> result, the Primary MCL is often deemed protective of human health. The purpose <br /> of the remedial action is usually quoted as being for the protection of human <br /> health and the environment. However, under CERCLA, usually only biological <br /> receptors are considered as part of the environment. It appears that protection <br /> of ground water as a resource is not considered as part of the environment when a <br /> Risk Assessment is performed under CERCLA guidance. Only biological receptors, <br /> and not the water resource, were considered for the Sharpe Risk Assessment (page <br /> 19) . <br /> Although the cleanup of the ground water as proposed by Sharpe will restore some <br /> beneficial uses of the aquifer, the cleanup of an aquifer to the Primary MCL does <br /> not necessarily protect all beneficial uses of the all water bodies in all cases. <br /> In site cleanups, where human health-based Risk Assessments are required to be <br /> performed, a clarifying statement on the differences between the evaluations <br /> needed to assess risks to human health or other biological receptors and risks to <br /> the water resource should be provided in the Risk Assessment. We suggest that a <br /> clarifying statement be presented in the Declaration for the ROD. <br /> VOC Plumes and Contaminants of Concern <br /> Section 6. 1 .2 of the Draft Final ROD (page 21) indicates that there are six VOC <br /> plumes at the Sharpe site and that TCE is the primary VOC contaminant of concern. <br /> We continue to disagree that there are six VOC plumes and believe that there may <br /> as few as four plumes because six source areas have not been identified. We have <br /> previously written regarding this issue in our letters dated 21 March 1991, 21 May <br /> 1992 and 14 December 1992. If there are six VOC plumes then it may be assumed <br /> that remedial action for the soils in the source areas are needed and will be <br /> addressed as part of the comprehensive RI/FS and ROD. <br /> When Sharpe submitted the Draft ROD on 6 April 1992, aquifer cleanup levels for <br /> many different VOCs were proposed because these constituents had been detected <br /> during ground water monitoring. Sharpe has accurately concluded that TCE is the <br /> primary contaminant of concern and conceptual plans for the remedial action are <br /> based on the extent and concentrations of this contaminant. However, other VOCs <br /> including, tetrachloroethylene (PCE) , 1, 1,1-trichloroethane (TCA) , 1,2- <br /> dichloroethane (DCA) , 1,2-dichloroethene (DCE) and carbon tetrachloride (CCL4) are <br /> frequently found in the ground water in the North and South Balloon and Central <br /> Areas. Two of these contaminants, 1,2-DCA and CCL4, have been detected in samples <br /> in concentrations that exceed the Primary Maximum Contaminant Level (MCL) of 0.5 <br /> Ag/l (for both constituents) . Concentrations of 1,2-DCA and CCL4 have been found <br /> in samples in concentrations of up to about 20 µg/1 . Sharpe has not produced <br /> concentration contour maps of these contaminants. Sharpe should produce <br />