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Enclosure One to DHS Letter to the MCTC, <br /> Subject: Closure Status and Information Requirements <br /> The Marley Stockton Facility Surface Impoundment <br /> EPA #CAD009140120 <br /> Information required from the MCTC: <br /> 1. Redesign of the proposed RCRA cap to extend the cap to a <br /> depth of 15 feet below the surface impoundment bottom and <br /> encompassing the entire perimeter of the surface <br /> impoundment. <br /> 2 . Risk assessment information including: <br /> a. Risk isopleths <br /> b Definition of any risk to school children or local <br /> residents. <br /> C. A risk reduction component for each of the five <br /> identified MCTC closure alternatives . <br /> 3 . Analysis of the potential for groundwater-level rise. If <br /> potential to rise is determined, the resultant impact to <br /> groundwater and necessary mitigating measures shall be <br /> addressed. <br /> 4 . A proposal for additional monitoring around the pond if <br /> hazardous waste were to be left in place. <br /> 5. The amount of hazardous waste in the surface impoundment by <br /> weight and hazardous waste constituents, e.g. pounds each of <br /> chromium three, chromium six, arsenic and copper. <br /> (Previously requested. ) <br /> 6. A leachability study for arsenic and copper. The <br /> leachability study shall consist of a series of tests to <br /> determine at which pH levels, (acid, neutral and alkaline) <br /> copper and arsenic will leach from the surface impoundment. <br /> The Department Hazardous Materials Laboratory (HML) will <br /> review the procedures used and the results of the study. In <br /> addition, the HML will conduct check analyses of split <br /> samples to be provided by. the MCTC. <br /> 7 . A detailed description and design of the proposed flushing <br /> system to include measures to preclude the injected fluids <br /> from saturating the hazardous waste above the piping system, <br /> and plans to ensure recapture of the contaminated <br /> groundwater. <br /> 8. A proposal for dust suppression and winterization of the <br /> surface impoundment. <br />