Oklahoma Administrative Code › Title 460 - Department of Mines › Chapter 20 - The Permanent Regulations Governing the Coal Reclamation Act of 1979 › Subchapter 45 - Permanent Program Performance Standards: Underground Mining Activities › Section 460:20-45-14 - Impoundments

Current through Vol. 41, No. 20, July 1, 2024
(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.