460:20-45-14 - Impoundments

460:20-45-14. Impoundments

(a) General requirements. The requirements of this Subsection apply to both temporary and permanent impoundments.

(1) Impoundments meeting the Class B or C criteria for dams in the U.S. Department of Agriculture, Soil Conservation Service Technical Release No. 60 (210-VI-TR60, Oct. 1985) shall comply with the "Minimum Emergency Spillway Hydrologic Criteria" table in TR-60 and the requirements of this section. The technical release is hereby incorporated by reference. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C 552(a) and 1 CFR Part 51. Copies may be obtained from the National Technical Information Service (NTIS), 5285 Port Royal Road, Springfield, Virginia 22161, order No. PB 87-157509/AS. Copies can be inspected at the OSM Headquarters Office, Office of Surface Mining Reclamation and Enforcement, Administrative Record, Room 660, 800 North Capitol Street, Washington, DC, or at the Office of the Federal Register, 800 North Capitol Street, NW, suite 700, Washington, DC.

(2) Impoundments meeting the criteria of 30 CFR Section 77.216(a) shall comply with the requirements of 30 CFR Section 77.216 and this section. The plan required to be submitted to the District Manager of MSHA under 30 CFR Section 77.216 shall also be submitted to the Department as part of the permit application.

(3) Design Certification. The design of impoundments shall be certified in accordance with Section 460:20-31-9(a) of this Chapter as designed to meet the requirement of this part using current, prudent, engineering practices and any design criteria established by the Department. The qualified, registered, professional engineer or qualified, registered, professional, land surveyor shall be experienced in the design and construction of impoundments.

(4) Stability.

(A) An impoundment meeting the Class B or C criteria for dams in TR-60, or the size or other criteria of 30 CFR 77.216(a) or located where failure would be expected to cause loss of life or serious property damage shall 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.

(B) Impoundments not included in Subsection (a)(4)(A) of this Section, except for a coal mine waste impounding structure, or located where failure would not be expected to cause loss of life or serious property damage shall have a minimum static safety factor of 1.3 for a normal pool with steady state seepage saturation conditions or meet the requirements of Section 460:20-31-9(c)(2).

(5) Freeboard. Impoundments shall have adequate freeboard to resist overtopping by waves and by sudden increases in storage volume. Impoundments meeting the Class B or C criteria for dams in TR-60 shall comply with the freeboard hydrograph criteria in the "Minimum Emergency Spillway Hydrologic Criteria" table in TR-60.

(6) Foundation.

(A) Foundation and abutments for the impoundment structure shall be stable under all conditions of construction and operation of the impoundment and shall be designed based on accurate and adequate information on the foundation conditions. For an impoundment meeting the Class B or C criteria for dams in TR-60 or the size or other criteria of 30 CFR 77.216(a), sufficient foundation investigations and laboratory testing of foundation material shall be performed in order to determine the design requirements for foundation stability.

(B) All vegetative and organic materials shall be removed and foundations excavated and prepared to resist failure. Cutoff trenches shall be installed if necessary to ensure stability.

(7) Slope protection shall be provided to protect against surface erosion at the site and protect against sudden drawdown.

(8) 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.

(9) Spillways. An impoundment shall include either a combination of principal and emergency spillways or a single spillway configured as specified in paragraph (a)(9)(A) of this Section, designed and constructed to safely pass the applicable design precipitation event specified in paragraph (a)(9)(B) of this Section, except as set forth in (c)(2) of this Section.

(A) The department may approve a single open-channel spillway that is:

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

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

(B) Except as specified in (c)(2) of this Section, the required design precipitation event for an impoundment meeting the spillway requirements of paragraph (a)(9) of this Section is;

(i) For an impoundment meeting the Class B or C criteria for dams in TR-60, the emergency spillway hydrograph criteria in the "Minimum Emergency Spillway Hydrologic Criteria" table in TR-60, or greater event as specified by the Department.

(ii) For an impoundment meeting or exceeding the size or other criteria of 30 CFR 77.216(a), a 100-year 6-hour event, or greater event as specified by the Department.

(iii) For an impoundment not included in Subsections (a)(9)(B)(I) or (ii), a 25-year 6-hour event, or greater event as specified by the Department.

(10) The vertical portion of any remaining highwall shall be located far enough below the low-water line along the full extent of highwall to provide adequate safety and access for the proposed water users.

(11) Inspections. Except as provided in paragraph (a)(11)(D) of this Section, a qualified registered professional engineer or other qualified professional specialist under the direction of a professional engineer, shall inspect each impoundment as provided in paragraph (a)(11)(A) of this Section. The professional engineer or specialist shall be experienced in the construction of impoundments.

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

(B) The qualified registered professional engineer, or qualified registered professional land surveyor as specified in paragraph (a)(11)(D) of this Section, shall promptly after each inspection required in paragraph (a(11)(A) of this Section provide to the Department 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 shall include discussion of any appearance of instability, structural weakness or other hazardous condition, depth and elevation of any impounded waters, existing storage capacity, and existing or required monitoring procedures and instrumentation, and any other aspects of the structure affecting stability.

(C) A copy of the report shall be retained at or near the minesite.

(D) A qualified registered professional land surveyor may inspect any temporary or permanent impoundment that does not meet the SCS Class B or C criteria for dams in TR-60 or the size or other criteria of 30 CFR 77.216(a) and certify and submit the report required by paragraph (a)(11)(B) of this Section, except that all coal mine waste impounding structures covered by Section 460:20-45-31 of this Chapter shall be certified by a qualified registered professional engineer. The professional land surveyor shall be experienced in the construction of impoundments.

(12) Impoundments meeting the SCS Class B or C criteria for dams in TR-60 or other criteria of 30 CFR 77.216(a) must be examined in accordance with 30 CFR 77.216-3. Other impoundments shall be examined at least quarterly by a qualified person designated by the operator for the appearance of structural weakness and other hazardous conditions.

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

(b) Permanent impoundments. A permanent impoundment of water may be created, if authorized by the Department in the approved permit based upon the following demonstration:

(1) The size and configuration of such 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, will meet applicable State and Federal water quality standards, and discharges from the impoundment will meet applicable effluent limitations and will not degrade the quality of receiving water below applicable State and Federal water quality standards.

(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 the diminution of the quality and quantity of water utilized by adjacent or surrounding landowners for agricultural, industrial, recreational, or domestic uses.

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

(c) Temporary impoundments.

(1) The Department may authorize the construction of temporary impoundments as part of a surface coal mining operation.

(2) In lieu of meeting the requirements of paragraph (a)(9)(A) of this Section, the Department may approve an impoundment that relies primarily on storage to control the runoff from the design precipitation event when it is demonstrated by the operator and certified by a qualified registered professional engineer or qualified registered land surveyor in accordance with Section 460:20-27-14(a) of this Chapter that the impoundment will safely control the design precipitation event, the water from which shall be safely removed in accordance with current, prudent, engineering practices. Such an impoundment shall be located where failure would not be expected to cause loss of life or serious property damage, except where:

(A) In the case of an impoundment meeting the SCS Class B or C criteria for dams in TR 60, or the size or other criteria of Section 77.216(a) of 30 CFR, it shall be designed to control the precipitation of the probable maximum precipitation of a 6-hour event, or greater event as specified by the Department, or

(B) In the case of an impoundment not included in Subsection (c)(2)(A) of this Section it shall be designed to control the precipitation of a 100-year 6-hour event, or greater event as specified by the Department.

Amended at 12 Ok Reg 3592, eff 10-12-95; Amended at 16 Ok Reg 3526, eff 9-13-99

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