R 425.409 Treatment and containment of reactive materials.

Rule 409. An operator shall manage overburden, ore, waste rock, peripheral rock, and tailings determined to be reactive under R 425.203(c)(v) in accordance with this rule and in a manner that is designed to reasonably minimize actual and potential adverse impacts on groundwater and surface water by preventing leaching or runoff of acid-forming waste products and other waste products from the mining process. (a) An operator shall design, construct, and operate stockpiles or storage facilities for reactive overburden, ore, waste rock, or tailings in compliance with paragraph (i) or (ii) of this subdivision. (i) A stockpile or storage facility shall meet the following requirements: (A) A stockpile or storage facility shall have a composite liner system comprised of a flexible synthetic membrane that is not less than 60 mils thick and a layer of at least 3 feet of compacted soil having a maximum hydraulic conductivity of 1.0 X 10-7 cm/sec. (B) The department may approve an alternative liner system that uses other materials or designs, including modified soil liners, or technologically advanced systems only if the operator provides data to demonstrate the alternative is capable of providing equivalent or better protection as compared to the requirements under subparagraph (A). (C) A stockpile or storage facility shall have a leachate collection system.The system shall be designed, constructed, and operated to limit the hydraulic head at the lowest point in the system to not more than 1 foot, excluding the collection sump, after construction. (D) A stockpile or storage facility shall have a leak detection system. (E) The liner, leachate collection system, and leak detection system shall be tested before the placement of overburden, ore, waste rock, or tailings into the facility. (F) A cover shall be employed to isolate the reactive overburden, ore, or waste rock from precipitation and air as soon as practicable. (G) A registered professional engineer or other qualified individual shall certify the proper design, construction, and testing of all liners, covers, and leachate collection systems required by this paragraph. The permittee shall submit the certification to the department and shall not begin placement of ore, waste rock, overburden, or tailings in the storage facility until approved by the department. (ii) Subject to approval of the department, an operator may utilize an alternative plan for a stockpile or storage facility for reactive overburden, ore, waste rock, or tailings. The department may approve an alternative plan only if the operator provides data that demonstrates that the alternative plan is capable of providing protection of groundwater and surface water that is equivalent to or better than that provided under paragraph (i) of this subdivision. The alternative plan shall incorporate 1 or more of the following: (A) Measures to prevent the generation of leachate by adding a material or materials that counteract or neutralize the acid-forming or toxic characteristics of the ore, waste rock, overburden, or tailings. (B) Measures to treat or neutralize any leachate that may be generated before it migrates outside of the storage facility. (C) Measures to isolate the ore, waste rock, overburden, or tailings from oxygen and other oxidizing substances. (D) Measures to isolate the ore, waste rock, overburden, or tailings from groundwater or surface water. (b) An operator may utilize a disposal facility to manage, contain, or isolate reactive waste rock, tailings, overburden, or peripheral rock subject to approval of the department. A disposal facility may consist of a mined area that will be backfilled. The department shall not approve the plans for a disposal facility unless the operator demonstrates that the design, construction, operation, and closure of the disposal facility will reasonably minimize the actual and potential adverse impacts on groundwater and surface water by preventing leaching or runoff of acid-forming waste products and other waste products from the mining process and will not require perpetual care following closure in accordance with MCL 324.63209(8) and with R 425.204(b)(vi). (c) A stockpile or storage or disposal facility under this rule shall be monitored in compliance with R 425.406. (d) A permittee shall conduct and maintain grading or diking at stockpiles and storage or disposal facilities subject to this rule to assure that surface water drains away from the storage or disposal area.