§ 784.25 - Return of coal processing waste to abandoned underground workings.

§ 784.25 What information must I provide for siltation structures, impoundments, and refuse piles?

(a) How do I determine the hazard potential of a proposed impoundment ? You must use the following table to identify the hazard potential classification of each proposed impoundment that includes a dam:

Hazard potential classification Loss of human life in event of failure Economic, environmental, or lifeline losses¹ in event of failure LowNone expectedLow potential; generally limited to property owned by the permittee. SignificantNone expectedYes. HighLoss of one or more lives probableYes, but not necessary for this classification.

¹ Lifeline losses refer to disruption of lifeline facilities, which include, but are not limited to, important public utilities, highways, and railroads.

(b) How must I prepare the general plan for proposed siltation structures, impoundments, and refuse piles ? If you propose to construct a siltation structure, impoundment, or refuse pile, your application must include a general plan that meets the following requirements:

(1) The plan must be prepared by, or under the direction of, and certified by a qualified registered professional engineer, a professional geologist, or, in any state that authorizes land surveyors to prepare and certify such plans, a qualified registered professional land surveyor, with assistance from experts in related fields such as landscape architecture.

(2) The plan must contain a description, map, and cross-sections of the structure and its location.

(3) The plan must contain the hydrologic and geologic information required to assess the hydrologic impact of the structure.

(4)

(i) The plan must contain a report describing the results of a geotechnical investigation of the potential effect on the structure if subsurface strata subside as a result of past, current, or future underground mining operations beneath or within the proposed permit and adjacent areas. When necessary, the investigation report also must identify design and construction measures that would prevent adverse subsidence-related impacts on the structure.

(ii) Except for structures that would meet the criteria in § 77.216(a) of this title or that would have a significant or high hazard potential under paragraph (a) of this section, the requirements of paragraph (b)(4)(i) of this section do not apply -

(A) In areas with 26.0 inches or less of average annual precipitation; or

(B) To siltation structures.

(5)

(i) The plan must contain an analysis of the potential for each impoundment to drain into subjacent underground mine workings, together with an analysis of the impacts of such drainage.

(ii) Except for structures that would meet the criteria in § 77.216(a) of this title or that would have a significant or high hazard potential under paragraph (a) of this section, the requirements of paragraph (b)(5)(i) of this section do not apply -

(A) In areas with 26.0 inches or less of average annual precipitation; or

(B) To siltation structures.

(6) The plan must include a schedule setting forth the dates when any detailed design plans for structures that are not submitted with the general plan will be submitted to the regulatory authority.

(c) How must I prepare the detailed design plan for proposed siltation structures, impoundments, and refuse piles ? -

(1) Detailed design plan requirements for high hazard dams, significant hazard dams, and impounding structures that meet MSHA criteria. If you propose to construct an impounding structure that would meet the criteria in § 77.216(a) of this title or that would have a significant or high hazard potential under paragraph (a) of this section, you must prepare and submit a detailed design plan that meets the following requirements:

(i) The plan must be prepared by, or under the direction of, a qualified registered professional engineer with assistance from experts in related fields such as geology, land surveying, and landscape architecture. The engineer must certify that the impoundment design meets the requirements of this part, current prudent engineering practices, and any design criteria established by the regulatory authority. The qualified registered professional engineer must be experienced in the design and construction of impoundments.

(ii) The plan must incorporate any design and construction measures identified in the geotechnical investigation report prepared under paragraph (b)(4) of this section as necessary to protect against potential adverse impacts from subsidence resulting from underground mine workings underlying or adjacent to the structure.

(iii) The plan must describe the operation and maintenance requirements for each structure.

(iv) The plan must describe the timetable and plans to remove each structure, if appropriate.

(2) Detailed design plan requirements for other structures. If you propose to construct an impounding structure that would not meet the criteria in § 77.216(a) of this title and that would not have a significant or high hazard potential under paragraph (a) of this section, you must prepare and submit a detailed design plan that meets the following requirements:

(i)

(A) Except as provided in paragraph (c)(2)(i)(B) of this section, the plan must be prepared by, or under the direction of, a qualified, registered, professional engineer, or, in any state that authorizes land surveyors to prepare and certify such plans, a qualified, registered, professional, land surveyor. The engineer or land surveyor must certify that the impoundment design meets the requirements of this part, current prudent engineering practices, and any design criteria established by the regulatory authority. The qualified registered professional engineer or qualified registered professional land surveyor must be experienced in the design and construction of impoundments.

(B) All coal mine waste structures to which §§ 817.81 through 817.84 of this chapter apply must be certified by a qualified, registered, professional engineer.

(ii) The plan must reflect any design and construction requirements for the structure, including any measures identified as necessary in the geotechnical investigation report prepared under paragraph (b)(4) of this section.

(iii) The plan must describe the operation and maintenance requirements for each structure.

(iv) The plan must describe the timetable and plans to remove each structure, if appropriate.

(3) Timing of submittal of detailed design plans. You must submit the detailed design plans to the regulatory authority either as part of the permit application or in accordance with the schedule submitted under paragraph (b)(6) of this section. The regulatory authority must approve, in writing, the detailed design plan for a structure before you may begin construction of the structure.

(d) What additional design requirements apply to siltation structures? You must design siltation structures in compliance with the requirements of § 817.46 of this chapter.

(e) What additional design requirements apply to permanent and temporary impoundments?

(1) You must design permanent and temporary impoundments to comply with the requirements of § 817.49 of this chapter.

(2) The regulatory authority may establish, through the regulatory program approval process, engineering design standards that ensure stability comparable to a 1.3 minimum static safety factor in lieu of conducting engineering tests to establish compliance with the minimum static safety factor of 1.3 required in § 816.49(a)(2)(ii) of this chapter.

(3) Each plan must include stability analyses of the proposed impoundment if the structure would meet the criteria in § 77.216(a) of this title or would have a significant or high hazard potential under paragraph (a) of this section. The stability analyses must address static, seismic, and post-earthquake (liquefaction) conditions. They must include, but are not limited to, strength parameters, pore pressures, and long-term seepage conditions. The plan also must contain a description of each engineering design assumption and calculation with a discussion of each alternative considered in selecting the specific analysis and design parameters and construction methods.

(f) What additional design requirements apply to coal mine waste impoundments, refuse piles, and impounding structures constructed of coal mine waste? If you propose to place coal mine waste in a refuse pile or impoundment, or if you plan to use coal mine waste to construct an impounding structure, you must comply with the applicable design requirements in paragraphs (f)(1) and (2) of this section.

(1) Design requirements for refuse piles. You must design refuse piles to comply with the requirements of §§ 784.28, 817.81, and 817.83 of this chapter.

(2) Design requirements for impounding structures that will impound coal mine waste or that will be constructed of coal mine waste.

(i) You must design impounding structures constructed of or intended to impound coal mine waste to comply with the coal mine waste disposal requirements of §§ 784.28, 817.81, and 817.84 of this chapter and with the impoundment requirements of paragraphs (a) and (c) of § 817.49 of this chapter.

(ii) The plan for each impounding structure that meets the criteria of § 77.216(a) of this title must comply with the requirements of § 77.216-2 of this title.

(iii) Each plan for an impounding structure that will impound coal mine waste or that will be constructed of coal mine waste must contain the results of a geotechnical investigation to determine the structural competence of the foundation that will support the proposed impounding structure and the impounded material. An engineer or engineering geologist must plan and supervise the geotechnical investigation. In planning the investigation, the engineer or geologist must -

(A) Determine the number, location, and depth of borings and test pits using current prudent engineering practice for the size of the impoundment and the impounding structure, the quantity of material to be impounded, and subsurface conditions.

(B) Consider the character of the overburden and bedrock, the proposed abutment sites for the impounding structure, and any adverse geotechnical conditions that may affect the impounding structure.

(C) Identify all springs, seepage, and groundwater flow observed or anticipated during wet periods in the area of the proposed impounding structure on each plan.

(D) Consider the possibility of mudflows, rock-debris falls, or other landslides into the impounding structure, impoundment, or impounded material.

(iv) The design must ensure that at least 90 percent of the water stored in the impoundment during the design precipitation event will be removed within a 10-day period.

Return of coal processing waste to abandoned underground workings.

(a) Each plan shall describe the design, operation and maintenance of any proposed coal processing waste disposal facility, including flow diagrams and any other necessary drawings and maps, for the approval of the regulatory authority and the Mine Safety and Health Administration under 30 CFR 817.81(f).

(b) Each plan shall describe the source and quality of waste to be stowed, area to be backfilled, percent of the mine void to be filled, method of constructing underground retaining walls, influence of the backfilling operation on active underground mine operations, surface area to be supported by the backfill, and the anticipated occurrence of surface effects following backfilling.

(c) The applicant shall describe the source of the hydraulic transport mediums, method of dewatering the placed backfill, retainment of water underground, treatment of water if released to surface streams, and the effect on the hydrologic regime.

(d) The plan shall describe each permanent monitoring well to be located in the backfilled area, the stratum underlying the mined coal, and gradient from the backfilled area.

(e) The requirements of paragraphs (a), (b), (c), and (d) of this section shall also apply to pneumatic backfilling operations, except where the operations are exempted by the regulatory authority from requirements specifying hydrologic monitoring.

[44 FR 15366, Mar. 13, 1979, as amended at 48 FR 44780, Sept. 30, 1983; 81 FR 93355, Dec. 20, 2016; 82 FR 54958, Nov. 17, 2017]