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7.2.4.2.1 Surface Water <br /> Since creek waters will not come in contact with wastes, and run-on and run-off <br /> will be controlled, the worst case surface water release scenario involves <br /> transport of minor volumes of landfill constituents in run-off to the creek. <br /> However, considering that wastes will be covered by daily and interim cover <br /> soils, and since run-off will be controlled in a drainage system designed for the <br /> 1000-year storm event and will be monitored as part of both the Waste <br /> Discharge Requirements and NPDES permits, the volume of impacted water that <br /> might be released from the site is expected to be small. In the event that runoff <br /> from the WMU impacts creek water, a program would be implemented to <br /> investigate how such impacts occur and to identify engineering measures (e.g., <br /> leachate seep controls such as additional cover soils or drains) to eliminate the <br /> source of impacts. <br /> 7.2.4.2.2 Vadose Zone <br /> The existing landfill gas collection well system at the site will be expanded to <br /> minimize the potential for gas migration. In addition, a network of perimeter gas <br /> migration monitoring probes will be constructed to verify the adequacy of the <br /> gas control measures. Liner construction will be completed in accordance with <br /> a construction quality assurance (CQA) plan that will minimize liner defects and, <br /> thus, minimize the potential for leachate to migrate to the vadose zone. Table <br /> 19 lists existing vadose zone monitoring stations (lysimeters) at the Forward <br /> Landfill and identifies their current and expected future uses. <br /> 7.2.4.2.3 Groundwater <br /> In the event that groundwater is impacted by landfill constituents, a number of <br /> remedial responses could be implemented, depending on the nature, location, <br /> and concentration of the waste constituents detected in groundwater. These <br /> remediation systems could include ex-situ "pump and treat" methods, or in-situ <br /> treatment of impacted groundwater. If it is determined that impacts are related <br /> to landfill gas migration, additional landfill gas collection wells may also be <br /> installed. The existing air stripper system is expected to be adequate to <br /> accommodate additional treatment volumes. <br /> Forward Landfill)TD 7-8 <br /> L:\Allied\2000.193\Reports\td:Sec-7.0:05/24/02 <br /> BRYAN A.BTIRRAT S ASSOCIATES <br />