Common use of Potential Impact to Groundwater Clause in Contracts

Potential Impact to Groundwater. For an environmental impact to occur to groundwater, leachate would have to migrate through the liner system of the landfill, flow vertically through the unsaturated zone, and then impinge on groundwater. As described in Section 1.2, both the Maplewood and King Xxxxxx County Landfills were constructed having composite double-liner systems, which exceed the liner performance standard of Subtitle D. These liner systems are highly efficient at preventing leakage of leachate from the landfill. The leachate collection systems of both landfills were designed to limit the thickness of leachate on the underlying liner to no more than 12 in. as required by subtitle D RCRA, which has been verified by design calculations. When liquids are applied to the landfill, there is a possibility that an increased quantity of leachate will reach the leachate collection system. Leachate head levels on the liner may also increase. However, as presented in Section 4.3 of the design reports [GeoSyntec, 2000a and 2000b] when additional liquids are applied, the thickness of leachate will not exceed 12 in. In reality, applying liquids to the waste above the leachate collection system will enhance the biodegradation process in the landfills, which cause more water to be consumed by landfill gas generation. This further reduces the amount of liquid that can reach the liner. For these reasons, the potential impact to groundwater will not exceed the potential environmental impact if the project were not implemented.