Design a cap incorporating low permeability clay and/or a flexible synthetic liner system sufficient to prevent water infiltration into the landfill and mitigate potential exposure of the public to waste, leachate, and methane. Existing cover soils may be stripped during cap construction and reused where practical as part of a protective vegetative layer. Existing clay may be removed as necessary and reused as part of a low permeability clay cap provided it meets permeability requirements. A borrow material source should be located at a reasonable distance to prevent excessive costs. If borrow material is not available, a synthetic cap option may be appropriate. Cap design should maximize positive drainage and limit infiltration. o NOTE: the on-site sports complex is now subject to removal. Any closure plan must bring the site back into compliance with the historic landfill program’s closure standards. o NOTE: Duke Energy and SD1 have existing on-going projects involving the landfill property. The selected firm will be required to coordinate with all project stakeholders to incorporate existing designs into the final cap. • Develop a design for the impound lot area that addresses soil contaminants, PAH’s, methane gas abatement and subsequent capping. • Develop a closure plan that addresses ongoing leachate and methane generation at the landfill. o Leachate treatment shall consist of a leachate collection system that can be tied to the existing SD1 sanitary sewer system for transport to the nearest wastewater treatment plant (WWTP). o Methane abatement activities will need to prevent methane intrusion into surrounding private property while also discharging methane safely to the atmosphere or collected for repurposing. • Develop a plan to remove the constructed wetland in its entirety. o NOTE: this wetland is subject to an in-leu fee program from the US Army Corps of engineers. Selected firm will be required to obtain a US Army Corps permit for the removal of the wetland.
