Texas Administrative Code › Title 16 - ECONOMIC REGULATION › Part 1 - RAILROAD COMMISSION OF TEXAS › Chapter 12 - COAL MINING REGULATIONS › Subchapter K - PERMANENT PROGRAM PERFORMANCE STANDARDS › Division 2 - PERMANENT PROGRAM PERFORMANCE STANDARDS - SURFACE MINING ACTIVITIES › Section 12.347 - Hydrologic Balance: Permanent and Temporary Impoundments

Current through Reg. 49, No. 28; July 12, 2024
(a) General Requirements. The requirements of
					 this subsection apply to both temporary and permanent impoundments.
(1) Impoundments meeting the significant or
					 high hazard class criteria of dams in the U.S. Department of Agriculture
					 (USDA), Natural Resources Conservation Service Technical Release No. 60
					 (210-VI-TR60, July 2005), Earth Dams and Reservoirs, shall comply with the
					 table of Minimum Auxiliary Spillway Hydrologic Criteria in Technical Release
					 No. 60 (TR-60), which is incorporated by reference, and the requirements of
					 this section. Copies may be obtained on the USDA website.
(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 of this section.
(3) The
					 design of impoundments shall be certified in accordance with §12.148(a) of
					 this title (relating to Reclamation Plan: Ponds, Impoundments, Banks, Dams, and
					 Embankments) as designed to meet the requirements of this part using current,
					 prudent, engineering practices and any design criteria established by the
					 Commission. The qualified professional engineer shall be experienced in the
					 design and construction of impoundments.
(4) Stability.
(A) An impoundment meeting the significant or
					 high hazard class criteria for dams in TR-60, or the size or other criteria of
					 30 CFR 77.216(a), shall have a minimum static 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) An impoundment
					 not included in subparagraph (A) of this paragraph, 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 §
													RSA
					 12.148<subdiv>(c)</subdiv> of
					 this title (relating to Reclamation Plan: Ponds, Impoundments, Banks, Dams, and
					 Embankments).
(5)
					 Impoundments shall have adequate freeboard to resist overtopping by waves and
					 by sudden increases in storage volume. Impoundments meeting the significant or
					 high hazard class criteria for dams in TR-60 shall comply with the freeboard
					 hydrograph criteria in the Minimum Auxiliary Spillway Hydrologic Criteria table
					 in TR-60.
(6) Foundations.
(A) 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 significant or high
					 hazard class 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
					 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) An impoundment shall
					 include either a combination of principal and auxiliary spillways or a single
					 spillway configured as specified in subparagraph (A) of this paragraph,
					 designed and constructed to safely pass the applicable design precipitation
					 event specified in subparagraph (B) of this paragraph.
(A) The Commission may approve a single
					 open-channel spillway that is of nonerodible construction and designed to carry
					 sustained flows or 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 subsection (c)(2) of this section, the required design precipitation event
					 for an impoundment meeting the spillway requirements of this paragraph is:
(i) for an impoundment meeting the
					 significant or high hazard class criteria for dams in TR-60, the auxiliary
					 spillway hydrograph criteria in the Minimum Emergency Spillway Hydrologic
					 Criteria table in TR-60, or greater event as specified by the
					 Commission;
(ii) for an impoundment
					 meeting or exceeding the size or other criteria of
					 RSA
					 77.216<subdiv>(a)</subdiv>, a
					 100-year, 6-hour event, or greater event as specified by the Commission;
					 and
(iii) for an impoundment not
					 included in clauses (i) and (ii) of this subparagraph, a 25-year, 6-hour event,
					 or greater event as specified by the Commission.
(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) A qualified
					 professional engineer or other qualified professional specialist under the
					 direction of a professional engineer, shall inspect each impoundment as
					 provided in subparagraph (A) of this paragraph. The professional engineer or
					 specialist shall be experienced in the construction of impoundments.
(A) Inspections shall be made regularly
					 during construction, upon completion of the construction, and at least yearly
					 until removal of the structure or release of the performance bond.
(B) The qualified professional engineer shall
					 promptly after each inspection required in subparagraph (A) of this paragraph,
					 provide the Commission 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 hazard 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.
(C)
					 A copy of the report shall be retained at or near the
					 minesite.
(12)
					 Impoundments meeting the NRCS significant or high hazard class 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 NRCS
					 significant or high hazard class 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) If any examination or inspection
					 discloses that a potential hazard exists, the person who examined the
					 impoundment shall promptly inform the Commission of the finding and of the
					 emergency procedures formulated for public protection and remedial action. If
					 adequate procedures cannot be formulated or implemented, the Commission shall
					 be notified immediately. The Commission shall then notify the appropriate
					 agencies that other emergency procedures are required to protect the
					 public.