Louisiana Administrative Code › Title 43 - NATURAL RESOURCES › Part XV - Office of Conservation-Surface Mining › Subpart 5 - Permanent Program Performance Standards › Chapter 53 - Permanent Program Performance Standards: Surface Mining Activities › Section XV-5333 - Hydrologic Balance: Impoundments

Current through Register Vol. 50, No. 6, June 20, 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 Number 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. 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 Number 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, D.C., or at the Office of the
Federal
				  Register
, 800 North Capitol Street, NW., Suite 700, Washington,
				  D.C.
2. Impoundments meeting the
				  criteria of
				  30
				  CFR 77.216(a) shall comply
				  with the requirements of
				  30
				  CFR 77.216 and § 5333.
3. Design Certification. The design of
				  impoundments shall be certified in accordance with §2725. A as designed to
				  meet the requirements of Chapter 53 using current prudent engineering practices
				  and any design criteria established by the office. The qualified registered
				  professional engineer 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) 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 §5333.
				  A.4 a, 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 or meet the requirements of §2725. C 1
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
				  impounding structure shall be designed to be stable under all phases of
				  construction and operation of the impoundment. Sufficient foundation
				  investigations and laboratory testing shall be performed in order to determine
				  the design requirements for foundation stability. 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), foundation
				  investigation, as well as any necessary laboratory testing of foundation
				  material, shall be performed 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 to 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 §5333. A.9 a, designed and constructed to
				  safely pass the applicable design precipitation event specified in §5333.
				  A.9 b, except as set forth in §5333. C 2
a. The office 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 §5333. C 2,
				  the required design precipitation event for an impoundment meeting the spillway
				  requirements of §5333. A.9 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
				  office;
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 office;
iii. for an impoundment not included in
				  §5333. A.9.b.i and ii, a 25-year 6-hour or greater event as specified by
				  the office.
10. The vertical portion of any remaining
				  highwall shall 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.
11. Inspections. A
				  qualified registered professional engineer or other qualified professional
				  specialist, under the direction of the professional engineer, shall inspect the
				  impoundment. 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 or release of
				  the performance bond.
b. The
				  qualified registered professional engineer, upon completion of construction,
				  shall promptly provide to the office a certified report that the impoundment
				  has been constructed as designed and in accordance with the approved plan and
				  these regulations. In addition, the qualified registered professional engineer
				  shall, after each annual inspection, promptly provide to the office a certified
				  report that the impoundment has been maintained in accordance with the approved
				  plan and these regulations. Each such report shall include discussion of any
				  appearances of instability, structural weakness or other hazardous conditions,
				  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.
c. A copy of the report shall be retained at
				  or near the minesite.
12. Impoundments meeting the SCS Class B or C
				  criteria for dams in TR-60, or the size or 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 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
				  office of the finding and of the emergency procedures formulated for public
				  protection and remedial action. If adequate procedures cannot be formulated or
				  implemented, the office shall be notified immediately. The office shall then
				  notify the appropriate agencies that other emergency procedures are required to
				  protect the public.