30 CFR 817.49 - What requirements apply to impoundments?

§ 817.49 What requirements apply to impoundments?

(a)Requirements that apply to both permanent and temporary impoundments. -

(1)MSHA requirements. An impoundment meeting the criteria of § 77.216(a) of this title must comply with the requirements of § 77.216 of this title and this section.

(2)Stability.

(i) An impoundment that meets the criteria of § 77.216(a) of this title or that includes a dam with a significant or high hazard potential classification under § 784.25(a) of this chapter must have a minimum static safety factor of 1.5 for a normal pool with steady state seepage saturation conditions and a seismic safety factor of at least 1.2.

(ii) Impoundments not included in paragraph (a)(2)(i) of this section, except for a coal mine waste impounding structure, must have a minimum static safety factor of 1.3 for a normal pool with steady state seepage saturation conditions or meet the requirements of § 784.25(e)(2) of this chapter.

(3)Freeboard.

(i) Impoundments must have adequate freeboard to resist overtopping by waves that occur in conjunction with the typical increase in water elevation at the downwind edge of any body of water, waves resulting from sudden influxes of surface runoff from precipitation events, or waves resulting from any combination of these events or other events.

(ii) An impoundment that includes a dam with a significant or high hazard potential classification under § 784.25(a) of this chapter must comply with the freeboard hydrograph criteria in the following table:

Minimum Auxiliary Spillway Hydrologic Criteria

Hazard potential classification of embankment Design precipitation event for -
Auxiliary spillway hydrograph Freeboard hydrograph
Significant P1001 0.12(PMP 2−P100) P100 0.40(PMP−P100)
High P100 0.26(PMP−P100) PMP

1 P100 = Precipitation event for 100-year return interval.

2 PMP = Probable Maximum Precipitation event.

(4)Foundation.

(i) Foundations and abutments for an impounding structure must be stable during all phases of construction and operation and must be designed based on adequate and accurate information on the foundation and abutment conditions.

(ii) You must conduct foundation and abutment investigations, as well as any necessary laboratory testing of foundation material, to determine the design requirements for foundation stability and control of underseepage for an impoundment that includes a dam with a significant or high hazard potential classification under § 784.25(a) of this chapter.

(iii) You must remove all vegetative and organic materials from the foundation area and excavate and prepare the foundation area to resist failure. You must install cutoff trenches if necessary to ensure stability.

(5)Protection of impoundment slopes. You must take measures to protect impoundment slopes from surface erosion and the adverse impacts of a sudden drawdown.

(6)Protection of embankment faces. Faces of embankments and surrounding areas shall be vegetated, except that faces where water is impounded may be riprapped or otherwise stabilized in accordance with accepted design practices.

(7)Spillways. An impoundment must include either a combination of principal and emergency spillways or a single spillway configured as specified in paragraph (a)(7)(i) of this section, designed and constructed to safely pass the applicable design precipitation event specified in paragraph (a)(7)(ii) of this section, except as set forth in paragraph (c)(2) of this section.

(i) The regulatory authority may approve a single open-channel spillway that is:

(A) Of nonerodible construction and designed to carry sustained flows; or

(B) Earth- or grass-lined and designed to carry short-term, infrequent flows at non-erosive velocities where sustained flows are not expected.

(ii) Except as specified in paragraph (c)(2) of this section, the required design precipitation event for an impoundment meeting the spillway requirements of paragraph (a)(7) of this section is:

(A) For an impoundment that includes a dam with a significant or high hazard potential classification under § 784.25(a) of this chapter, the design precipitation event specified in the auxiliary spillway hydrograph column in the table in paragraph (a)(3)(ii) of this section, or any greater event specified by the regulatory authority.

(B) For an impoundment meeting the criteria of § 77.216(a) of this title, the 100-year, 6-hour event, or any greater event specified by the regulatory authority.

(C) For an impoundment not included in paragraphs (a)(7)(ii) (A) and (B) of this section, the 25-year, 6-hour event, or any greater event specified by the regulatory authority.

(8)Highwalls. The vertical portion of any highwall remnant within the impoundment must be located far enough below the low-water line along the full extent of the highwall to provide adequate safety and access for the proposed water users.

(9)Inspections. Except as provided in paragraph (a)(9)(iv) of this section, a qualified registered professional engineer or other qualified professional specialist under the direction of a professional engineer must inspect each impoundment as provided in paragraph (a)(9)(i) of this section. The professional engineer or specialist must be experienced in the construction of impoundments.

(i) Inspections must be made regularly during construction, upon completion of construction, and at least yearly until removal of the structure or release of the performance bond.

(ii) After each inspection required by paragraph (a)(9)(i) of this section, the qualified registered professional engineer, or qualified registered professional land surveyor as specified in paragraph (a)(9)(iv) of this section, must promptly provide to the regulatory authority a certified report that the impoundment has been constructed and/or maintained as designed and in accordance with the approved plan and this chapter. The report must include a discussion of any appearance of instability, any structural weakness or other hazardous condition, the depth and elevation of any impounded waters, the existing storage capacity, any existing or required monitoring procedures and instrumentation, and any other aspects of the structure affecting stability.

(iii) You must retain a copy of the report at or near the minesite.

(iv) In any state that authorizes land surveyors to prepare and certify plans in accordance with § 784.25(b)(1) of this chapter, a qualified registered professional land surveyor may inspect any temporary or permanent impoundment that does not meet the criteria of § 77.216(a) of this title, or that is not classified as having a significant or high hazard potential under § 784.25(a) of this chapter, and certify and submit the report required by paragraph (a)(9)(ii) of this section, except that a qualified registered professional engineer must certify all coal mine waste impounding structures covered by § 817.84 of this chapter. The professional land surveyor must be experienced in the construction of impoundments.

(10)Examinations.

(i) Impoundments that meet the criteria of § 77.216 of this title, or that are classified as having a significant or high hazard potential under § 784.25(a) of this chapter, must be examined in accordance with § 77.216-3 of this title.

(ii) Impoundments that are not subject to § 77.216 of this title, or that are not classified as having a significant or high hazard potential under § 784.25(a) of this chapter, must be examined at least quarterly. A qualified person designated by the operator must examine impoundments for the appearance of structural weakness and other hazardous conditions.

(11)Emergency procedures. If any examination or inspection discloses that a potential hazard exists, the person who examined the impoundment must promptly inform the regulatory authority of the finding and of the emergency procedures formulated for public protection and remedial action. The regulatory authority must be notified immediately if adequate procedures cannot be formulated or implemented. The regulatory authority then must notify the appropriate agencies that other emergency procedures are required to protect the public.

(b)Requirements that apply only to permanent impoundments. A permanent impoundment of water may be created if authorized by the regulatory authority in the approved permit based upon the following demonstration:

(1) The size and configuration of the impoundment will be adequate for its intended purposes.

(2) The quality of impounded water will be suitable on a permanent basis for its intended use and, after reclamation, discharges from the impoundment will not cause or contribute to a violation of applicable state or tribal water quality standards or effluent limitations, including, but not limited to, water quality standards established under the authority of section 303(c) of the Clean Water Act, 33 U.S.C. 1313(c), and effluent limitations established in the National Pollutant Discharge Elimination System permit for the operation under section 402 of the Clean Water Act, 33 U.S.C. 1342, or its state or tribal counterpart.

(3) The water level will be sufficiently stable and be capable of supporting the intended use.

(4) Final grading will provide for adequate safety and access for proposed water users.

(5) The impoundment will not result in diminution of the quality or quantity of surface water or groundwater used by surrounding landowners for agricultural, industrial, recreational, or domestic uses.

(6) The impoundment will be suitable for the approved postmining land use.

(7) Approval of the impoundment will not result in retention of spoil piles or ridges that are inconsistent with the definition of approximate original contour.

(8) Approval of the impoundment will not result in the creation of an excess spoil fill elsewhere within the permit area.

(9) The impoundment has been designed with dimensions, features, and other characteristics that will enhance fish and wildlife habitat to the extent that doing so is not inconsistent with the intended use.

(c)Requirements that apply only to temporary impoundments that rely primarily upon storage.

(1) In lieu of meeting the requirements in paragraph (a)(7)(i) of this section, the regulatory authority may approve an impoundment that relies primarily on storage to control the runoff from the design precipitation event when you demonstrate, and a qualified registered professional engineer or qualified registered professional land surveyor in accordance with § 784.25(b) of this chapter certifies, that the impoundment will safely control the design precipitation event.

(2) You must use current prudent engineering practices to safely remove the water from an impoundment constructed in accordance with paragraph (c)(1) of this section.

(3) An impoundment constructed in accordance with paragraph (c)(1) of this section must be located where failure would not be expected to cause loss of life or serious property damage, unless the impoundment meets one of the following exceptions:

(i) An impoundment that meets the criteria of § 77.216(a) of this title, or that is classified as having a significant or high hazard potential under § 784.25(a) of this chapter, and is designed to control the precipitation of the probable maximum precipitation of a 6-hour event, or any greater event specified by the regulatory authority.

(ii) An impoundment not included in paragraph (c)(3)(i) of this section that is designed to control the precipitation of the 100-year, 6-hour event, or any greater event specified by the regulatory authority.

This is a list of United States Code sections, Statutes at Large, Public Laws, and Presidential Documents, which provide rulemaking authority for this CFR Part.

This list is taken from the Parallel Table of Authorities and Rules provided by GPO [Government Printing Office].

It is not guaranteed to be accurate or up-to-date, though we do refresh the database weekly. More limitations on accuracy are described at the GPO site.


United States Code
U.S. Code: Title 30 - MINERAL LANDS AND MINING