30 CFR 817.84 - What special requirements apply to coal mine waste impounding structures?
(b) You may not use coal mine waste to construct impounding structures unless you demonstrate, and the regulatory authority finds in writing, that the stability of such a structure conforms to the requirements of this part and that the use of coal mine waste will not have a detrimental effect on downstream water quality or the environment as a result of acid drainage or toxic seepage through the impounding structure. You must discuss the stability of the structure and the prevention and potential impact of acid drainage or toxic seepage through the impounding structure in detail in the design plan submitted to the regulatory authority in accordance with § 784.25 of this chapter.
(1) You must design, construct, and maintain each impounding structure constructed of coal mine waste or intended to impound coal mine waste in accordance with paragraphs (a) and (c) of § 817.49 of this part.
(2) You may not retain these structures permanently as part of the approved postmining land use.
(3) Each impounding structure constructed of coal mine waste or intended to impound coal mine waste that meets the criteria of § 77.216(a) of this title must have sufficient spillway capacity to safely pass, adequate storage capacity to safely contain, or a combination of storage capacity and spillway capacity to safely control, the probable maximum precipitation of a 6-hour precipitation event, or greater event as specified by the regulatory authority.
(d) You must design spillways and outlet works to provide adequate protection against erosion and corrosion. Inlets must be protected against blockage.
(e) You must direct surface runoff from areas above the disposal facility and runoff from the surface of the facility that may cause instability or erosion of the impounding structure into stabilized channels designed and constructed to meet the requirements of § 817.43 of this part and to safely pass the runoff from a 100-year, 6-hour precipitation event. You must use the appropriate regional Natural Resources Conservation Service synthetic storm distribution to determine the peak flow from surface runoff from this event.
(f) For an impounding structure constructed of or impounding coal mine waste, you must remove at least 90 percent of the water stored during the design precipitation event within the 10-day period following the design precipitation event.