Cell 4 is currently in need of a final closure design and long-term monitoring plan. This design and plan must comply with all regulatory requirements surrounding landfill closures and must be submitted to the Oregon Department of Environmental Quality (DEQ) for approval. Other than County approval during the design process, no other permits are anticipated. The closure design will address grading for surface water drainage, an impermeable cap, shallow subsurface drainage and deeper groundwater gradient control. There is an existing groundwater gradient control line as well as a shallow subsurface line that will need to be extended further to address the groundwater around cell 4. The design will also need to positively connect to the existing cell 3 top liner. Additionally, survey and volume calculations will be needed for an existing soil stockpile which is intended for use to construct the cell cap. A leachate collection system is already in place and will not be a part of this closure design. As the monofill only accepted material rendered inert (incinerator ash), a landfill gas collection system will also not be necessary or a part of this closure design (unless requested by Oregon DEQ).
