Section 096-200-5-21 - Mine Waste Unit Design StandardsA.Requirements. Mine waste units shall be designed to prevent the direct or indirect discharge of pollutants that could reasonably result in a condition of nonattainment or noncompliance with the performance standards of this Chapter.(1) The design of waste units for the management of Group A mine waste shall provide for a liner system which includes a composite liner. A leachate collection and removal system above the composite liner shall be incorporated into the design. A composite liner shall consist of the following:(a) A clay or compacted till bottom liner having a permeability of less than or equal to 1 x 10-6 cm/sec with a minimum 2-foot thickness; and(b) A High-Density Polyethylene (HDPE) liner having a minimum thickness of 60 mils.(2) The design of waste units for the management of Group B mine waste must provide for a clay or till bottom liner having a permeability of less than or equal to 1 x 10-7 cm/sec with a minimum 3-foot thickness. A leachate collection and removal system above the liner must be incorporated into the design.(3) Leachate ponds must be provided with the composite liner system described in subsection 21(A)(1) of this Chapter except that leachate collection and removal are not required. An emergency spillway must be included in the design. Leachate ponds must have a minimum 2 feet of freeboard measured to the lowest spillway elevation or an additional capacity volume equal to 25% of the total required capacity, whichever provides greater storage volume. Additional freeboard or other measures may be required to contain wave action as necessary. Leachate ponds must have a means installed to measure leachate depth within the ponds.(4) If stabilization of Group A and Group B mine waste may be ineffective in preventing pollutant release, the design must include a system for detection of leaks and leak recovery, or other engineered system as required by the Department.(5) If a mine waste unit will generate leachate, the Applicant shall provide a description of the leachate management methods for the unit, including a process flow diagram for water use and reuse at the site, and a water balance for each unit. In evaluating the water balance for each unit, the volume of leachate generated must be based on the most recent historical annual precipitation data, with a minimum of a 15-year database, and the leachate storage volume must include capacity for the precipitation from a 24-hour, 500-year storm falling on the mine waste unit and the leachate storage pond.(6) Leachate collection and removal systems must be designed to maintain 12 inches or less of leachate head on the liner system.(7) The Department reserves the right to require additional and/or alternative waste unit design elements if necessary to protect the environment and public health and safety.B.Alternative Design Process. Alternatives to the minimum design standards and requirements may be proposed by the applicant. A variance request is not required for proposals which meet the requirements of this paragraph. The Applicant shall submit the following documentation to clearly and convincingly demonstrate technical equivalency of a proposed alternative:(1) A discussion of the benefits of the proposed alternative technology;(2) A discussion of the risks and drawbacks of the proposed alternative technology;(3) An assessment of similar applications of the proposed alternative technology;(4) A demonstration that the alternative technology will provide equal or superior performance to the component it is proposed to replace, or that its inclusion within a system will result in equal or superior performance of that system;(5) An assessment of the feasibility of constructing the proposed alternative, including the ability to provide an adequate level of quality assurance and quality control. A demonstration of the feasibility of construction may be required; and(6) An assessment of the likelihood that the proposed alternative will perform as designed through operations, closure, and post-closure periods.C.Tailings Management. All tailings must be managed in dry stack tailings management units. Notwithstanding section 21(B), no alternative tailings management designs or technologies will be approved.06-096 C.M.R. ch. 200, § 5-21