will continue to migrate into the river subsurface approximately 99.9% of the rain and snow melt water will be eliminated from leachate generation by the cap. The landfill leaahate mound (water level within the waste) will be starved of water and will begin to fall as leachate continues to be removed via the collection system. The substrate is not an adequate liner to enhance with a slurry wall and eliminate hydraulic connection with the river discharge system. A slurry wall would only be effective at the CPL in combination with a pump and treat system (Alternative 2B). A slurry wall alone would only retard the flow of water from beneath the landfill to the river. A pumping system within the confines of the slurry wall is needed to reverse the flow of water from the river towards the slurry wall. The reasons why Alternative 2 was selected over Alternative 2B are explained in the response to Issue No. 9. Issue 11: The selected remedy should be amended to include the installation of an active deep well leachate collection system capable of retnoving a significant mass of contaminants from the landfill. ResDonse: As discussed in the response to Issue 9, the acceleration of the capping schedule by two years will result in a greater reduction of contaminant mass loading to the environment than pumping the leachate mound for 15 years. Deeper groundwater is generally less contaminated than the leachate mound within the waste mass as demonstrated by comparing the shallow or S-series monitoring well results to the deep or D-series monitoring well results presented in the RI Report (refer to RI Tables 4.7-1 and 4.7-2). Therefore, pumping from a deep well collection system would not reduce contaminant mass loading to the environment as much as pumping the leachate mound or accelerating the capping schedule by two years. Issue 12: The selected remedy should include the installation of a temporary leachate recirculating system until the technology is available for the effective treatment of leachate at sewage treatment facilities. In addition, once the on-site treatment system is installed, it could be.used to introduce cleansing agents to the landfill to remove the toxins and pollutants. ResDonse: In April 1992, the County ceased recirculating leachate at the landfill and began to send leachate to the STP with the concurrence of the DEC. By stopping leachate recirculation, the height of leachate within the waste will begin to decrease and will result in less leachate being discharged to the environment. Therefore, to temporarily recirculate leachate would result in a greater impact to the environment. There is no need to hesitate in sending contaminants to a STP because the consultantrs analysis clearly shows the plant is fully capable of processing the landfill leachate and 'meeting all regulatory limits at the present time. We presume the cleansing agents referred to by the commenter are surfactants or similar compounds used to make relatively insoluable organic compounds much more soluble in water (acids can also be used to mobilize metals). While such methods are suitable for remediating relatively small volumes (less than 100,000 cubic yards) of contaminated soils or waste in a contained treatment system (concrete or steel tanks), these methods are neither effective nor suitable for a large volume\of waste (11 million cubic yards) in-place where containment and control of these fluids would be impractical. Mobilizing metals and organics in this manner would create a much greater impact on the environment than leaving the site unremediated. Issue 13: Provide a list of parameters for which the County will test the various environmental media. Resoonse: Groundwater and surface waters will be sampled and tested for 6 NYCRR Part 360 baseline parameters annually and routine parameters quarterly at a minimum for the first five (5) years. Routine parameters include ammonia, nitrate, COD, TOC, TDS, sulfate, alkalinity, phenols, chloride, total hardness, turbidity, potassium, sodium, iron, manganese, magnesium, lead, cadmium, and calcium. Baseline parameters include all the routine parameters plus total Kjeldahl nitrogen, BOD, color, boron, aluminum, antimony, arsenic, beryllium, barium, chromium (total and hexavalent), copper, mercury, nickel, selenium, silver, thallium, zinc, cyanide and volatile organics. Landfill gases will be sampled from the collection pipes and tested for volatile organics and combustible gas concentration. Stormwater discharge testing will be set by the DEC under the County's general stormwater discharge permit. Marsh sediments will be tested for arsenic, cadmium, copper, lead, mercury, and silver at a minimum. Leachate will be tested monthly for the first several years for biological oxygen demand (BOD), total suspended solids, total organics, and various metals including antimony, cadmium, chromium, copper, lead, mercury, nickel, silver and zinc at a minimum. The above parameters will be included in the long-term monitoring plan, however, the review of the County's plan by DEC and DOH may result in the addition of other parameters. Subsequent