Virginia Administrative Code › Title 4 - CONSERVATION AND NATURAL RESOURCES › Agency 25 - DEPARTMENT OF ENERGY › Chapter 130 - COAL SURFACE MINING RECLAMATION REGULATIONS › Part 817 - Permanent Program Performance Standards-Underground Mining Activities › Section 4VAC25-130-817.49 - Impoundments

Current through Register Vol. 40, No. 24, July 15, 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), "Earth Dams and Reservoirs," 1985 shall comply with "Minimum
				  Emergency Spillway Hydrologic Criteria" table in TR-60 and the requirements of
				  this section. The technical release is hereby incorporated by reference. Copies
				  may be obtained from the National Technical Information Service (NTIS), 5285
				  Port Royal Road, Springfield, Virginia 22161, Order No. PB87-157509/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, D.C. or at the Office of the Federal Register, 800 North
				  Capitol Street, NW, Suite 700, Washington D.C.
(2) An impoundment meeting the size or other
				  criteria of 30 CFR
				  77.216(a) shall comply with
				  the requirements of 30 CFR
				  77.216 and this section.
(3) Design certification. The design of
				  impoundments shall be certified by a qualified registered professional engineer
				  as designed to meet the requirements of this Part using current, prudent
				  engineering practices and any other criteria established by the division. The
				  qualified registered professional engineer shall be experienced in the design
				  and construction of impoundments.
(4) Stability.
(i) An impoundment meeting the SCS Class B or
				  C criteria for dams in TR-60, or the size or other criteria of
				  30 CFR
				  77.216(a) 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.
(ii) Impoundments not included in paragraph
				  (a)(4)(i) of this section, except for a coal mine waste impounding structure
				  shall have a minimum static safety factor of 1.3 for a normal pool with steady
				  state seepage saturation conditions. In lieu of engineering tests to establish
				  compliance with the minimum static safety factor of 1.3, earth embankments
				  whose top widths are no less than 10 feet and whose embankment slopes are 2h:1v
				  or flatter may be used provided that the permittee documents that a minimum
				  static safety factor of 1.3 can be met using the graphical solution methods
				  outlined in the "Bureau of Mines Report of Investigations/1981, RI 8564, Factor
				  of Safety Charts for Estimating the Stability of Saturated and Unsaturated
				  Tailings Pond Embankments, United States Department of Interior."
(5) Freeboard. Impoundments shall
				  have adequate freeboard to resist overtopping by waves and by sudden increases
				  in storage volume. The minimum freeboard shall be one foot. Impoundments
				  meeting the SCS 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.
(i) Foundations and abutments for
				  an impounding structure shall be stable during all phases of construction and
				  operation and shall be designed based on adequate and accurate information on
				  the foundation conditions. For an impoundment meeting the SCS Class B or C
				  criteria for dams in TR-60, or the size or other criteria of
				  30 CFR
				  77.216(a), foundation
				  investigations, as well as any necessary laboratory testing of foundation
				  material shall be performed to determine the design requirements for foundation
				  stability.
(ii) 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 and minimize seepage. The pool area shall be cleared of all brush and
				  trees unless the requirement is waived by the division.
(iii) The most impervious material available
				  shall be used in the cutoff trench and center portion of the dam. If sandy or
				  gravelly material is encountered, it shall be placed in the outer shell,
				  preferably in the downstream portion of the dam.
(7) Slope protection. Slope protection shall
				  be provided to protect against surface erosion at the site and protect against
				  sudden drawdown.
(8) Vegetation.
				  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)(i) of this section, designed and
				  constructed to safely pass the applicable design precipitation event specified
				  in paragraph (a)(9)(ii) of this section, except as set forth in paragraph
				  (c)(2) of this section.
(i)
(A) The division may approve a single
				  open-channel spillway that is:
(1) Of
				  nonerodible construction and designed to carry sustained flows; or
(2) Earth- or grass-lined and designed to
				  carry short-term, infrequent flows at non-erosive velocities where sustained
				  flows are not expected.
(B) Temporary ponds that do not meet the size
				  or other criteria of 30 CFR
				  77.216(a) and located where
				  failure would not be expected to cause loss of life or serious property damage,
				  may use a single spillway of the pipe and riser design if the riser is no less
				  than 15 inches in diameter, the barrel is no less than 12 inches in diameter,
				  and a properly designed anti-vortex device and trash rack are securely
				  installed on top of the riser.
(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)(9) of this section is:
(A) For an impoundment meeting the SCS Class
				  B or C criteria for dams in TR-60, the emergency spillway hydrologic criteria
				  in the "Minimum Emergency Spillway Hydrologic Criteria" table in TR-60 or
				  greater event as specified by the division.
(B) For an impoundment meeting or exceeding
				  the size or other criteria of
				  30 CFR
				  77.216(a), a 100-year
				  six-hour event, or greater event as specified by the division.
(C) For an impoundment not included in
				  paragraphs (a)(9)(ii)(A) and (B) of this section, a 25-year six-hour event, or
				  greater event as specified by the division.
(10) Inspections. 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)(10)(i) of this section. The professional engineer or
				  specialist shall be experienced in the construction of impoundments.
(i) Inspections shall 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) The qualified registered professional
				  engineer shall, within two weeks after each inspection required in paragraph
				  (a)(10)(i) of this section, provide to the division, a certified report that
				  the impoundment has been constructed and/or maintained as designed and in
				  accordance with the approved plan and this chapter. Construction certified in
				  previous reports need not be recertified after each annual inspection. 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, any existing or required monitoring
				  procedures and instrumentation, and any other aspects of the structure
				  affecting stability.
(iii) A copy
				  of the report shall be retained at or near the minesite.
(11) Examinations. Impoundments meeting the
				  SCS Class B or C criteria for dams in TR-60, or the size of other criteria of
				  30 CFR
				  77.216 must be examined in accordance with
				  30 CFR
				  77.216-3. Impoundments not meeting the SCS
				  Class B or C criteria for dams in TR-60, or subject to
				  30 CFR
				  77.216 shall be examined at least quarterly.
				  A qualified person designated by the operator shall examine impoundments for
				  appearance of structural weakness and other hazardous conditions.
(12) Emergency procedures. If any examination
				  or inspection discloses that a potential hazard exists, the permittee shall
				  promptly inform the division of the finding and of the emergency procedures
				  formulated for public protection and remedial action. If adequate procedures
				  cannot be formulated or implemented, the division shall be notified
				  immediately. Notification shall be by the fastest available means and followed
				  in writing. The division shall then notify the appropriate agencies that other
				  emergency procedures are required to protect the public.