Closure criteria

In addition to sections 33.1-20-04.1-05 and 33.1-20-04.1-09, at closure, an owner or operator shall cover an existing unit with a layer of compacted clay-rich earthen material having a thickness of twelve inches [30.5 centimeters] or more and free from cracks and extrusions of solid waste. A second layer of six inches [15.2 centimeters] or more of clay-rich soil material suitable for serving as a plant root zone must be placed over the compacted layer. At least six inches [15.2 centimeters] of suitable plant growth material must be placed over the covered landfill and the facility planted with adapted grasses. The total thickness of the final cover must be at least two feet [61.0 centimeters]. If a total cover thickness of four feet [1.2 meters] or more of clay-rich earthen material is achieved, including the six-inch layer of suitable plant growth material, compaction is not required.