8 CAR § 60-621. Minimum design criteria

(a) Applicability. Unless provided otherwise, the requirements of this section as well as 8 CAR §§ 60-624, 60-625, and 60-626 shall apply only to: (1) Newly permitted facilities; (2) Increases in the permitted capacity or disposal area; or (3) Permit renewals as specified in 8 CAR § 60-309. (b) Design standards. In accordance with 8 CAR § 60-620, a facility or practice shall be designed to prevent the contamination of an underground drinking water source beyond the solid waste boundary or beyond an alternative boundary specified in accordance with 8 CAR § 60-620(b). (c) Minimum design criteria. At a minimum, the bottom and side slope liner systems of new Class 4 landfills and expansions of the permitted fill area shall be constructed: (1) With a compacted clay liner consisting of at least an eighteen-inch thickness with a hydraulic conductivity of no more than 1 x 10-5 cm/sec; or (2)(A) In accordance with a design approved by the Director of the Division of Environmental Quality. (B) The design must ensure that the concentration values specified in Appendix 3 will not be exceeded in the uppermost aquifer at the relevant point of compliance, as specified by the director under 8 CAR § 60-620. (C) Landfills sited in favorable, uniform geologic settings exhibiting in-place permeability equal to or less than 1 x 10-5 cm/sec may be constructed without compacted liners provided the standards of this section are met. (d) Final cover system requirements. Each waste unit shall at a minimum provide a final cover system consisting of, from bottom to top: (1) A compacted clay barrier layer of at least an eighteen-inch thickness with a hydraulic conductivity of no more than 1 x 10-5 cm/sec; and (2) An erosion layer of at least six inches (6”) thickness that is capable of supporting vegetation; or (3)(A) In accordance with a design approved by the director. (B) The design must demonstrate equivalency to the prescriptive final cover requirements contained in subdivision (d)(1) of this section. (e) Ground water monitoring. Ground water monitoring will not be required unless the director determines that monitoring is required to confirm that the ground water standards set forth in 8 CAR § 60-620 are being met.