Landfill cover and closure

1. The owner or operator must place intermittent cover on all exposed solid waste according to the approved operation plan. a. Unless specified otherwise in the operation plan, the solid waste must not be left uncovered for more than forty-eight hours. Cover must be provided by additional waste or with a suitable material proposed by the landfill owner and approved by the department. b. The cover materials used and cover depth must be sufficient to cover the solid waste completely. 2. The final cover at closure must be eight feet [2.74 meters] or more, and meet the requirement of subsection 7 of section 33.1-20-10-03. In addition, the final cover must include, at a minimum from bottom to top: a. A barrier layer consisting of at least twenty-four inches [61.0 centimeters] of compacted earthen materials with a hydraulic conductivity no greater than 1 x 10-7 centimeters per second; b. A synthetic flexible membrane liner which is at least sixty mil thick; c. A drainage layer consisting of at least six inches [15.2 centimeters] with a transmissivity of 3 x 10-2 centimeters squared per second or greater; d. A layer which is at least thirty-six inches [91.4 centimeters] thick to protect the synthetic liner and barrier layer from freezing, the upper twelve inches [30.5 centimeters] of this layer must be suitable as a plant root zone; and e. A top layer at least six inches [15.2 centimeters] thick consisting of suitable plant growth material.