Indiana Administrative Code › Title 312 - NATURAL RESOURCES COMMISSION › Article 25 - COAL MINING AND RECLAMATION OPERATIONS › Rule 6 - Performance Standards › Section 6-84 - Underground mining; hydrologic balance; permanent and temporary impoundments

Current through July 10, 2024
Authority: IC 14-34-2-1
Affected: IC 14-34
Sec. 84.
(a) This
				section applies to both temporary and permanent impoundments and must satisfy
				the following conditions:
(1) An impoundment
				meeting the Class B or C criteria for dams in the NRCS publication Technical
				Release No. 60 (TR-60) or 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 rule.
(2) The design of impoundments shall be
				certified in accordance with
				312
				IAC 25-4-87 as designed to meet the requirement of
				this rule using current, prudent engineering practices and any design criteria
				established by the director. The qualified registered professional engineer
				shall be experienced in the design and construction of impoundments.
(3) Impoundments must meet the following
				criteria for stability:
(A) An impoundment
				meeting the Class B or C criteria for dams in the NRCS publication Technical
				Release No. 60 (TR-60) or an impoundment meeting the size or other criteria of
				30
				CFR 77.216(a) shall have a
				minimum static safety factor of one and five-tenths (1.5) for a normal pool
				with steady state seepage saturation conditions and a seismic safety factor of
				at least one and two-tenths (1.2).
(B) Impoundments not meeting the Class B or C
				criteria for dams in the NRCS publication Technical Release No. 60 (TR-60) or
				not meeting the size or other criteria of
				30
				CFR 77.216(a), except for a
				coal mine waste impounding structure, shall have a minimum static safety factor
				of one and three-tenths (1.3) for a normal pool with steady state seepage
				saturation conditions.
(C) In lieu
				of meeting the static safety factor requirements of clause (B), the applicant
				may elect, in order to ensure stability for temporary impoundments not meeting
				the Class B or C criteria for dams in the NRCS publication Technical Release
				No. 60 (TR-60) or not meeting the size or other criteria of
				30
				CFR 77.216(a) to grade as
				follows:
(i) The side slopes of the settled
				embankments shall not be steeper than two (2) horizontal to one (1) vertical on
				the upstream slopes.
(ii) The
				downstream slopes shall not be steeper than three (3) horizontal to one (1)
				vertical. An impoundment constructed within these guidelines shall not be
				approved for permanent postmining land use until the criteria for permanent
				impoundments of this section have been satisfied.
(4) The size and configuration of
				the impoundment shall be adequate for its intended purposes. 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.
(5) 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 size or other
				criteria of
				30
				CFR 77.216(a) or the Class B
				or C criteria for dams in the NRCS publication Technical Release No. 60
				(TR-60), foundation investigation, as well as any necessary laboratory testing
				of foundation material, shall be performed to determine the design requirements
				for foundation stability. 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.
(6) Slope protection shall be provided to
				protect against surface erosion at the site and protect against sudden
				drawdown.
(7) An impoundment shall
				include either a combination of principal and emergency spillways or a single
				spillway configured as specified in clause (A), designed and constructed to
				safely pass the applicable design precipitation event specified in clause (B),
				except as set forth in subsection (c)(1).
(A)
				The director may approve a single open channel spillway that is:
(i) of nonerodible construction and designed
				to carry sustained flows; or
(ii)
				earth-lined or grass-lined and designed to carry short term, infrequent flows
				at nonerosive velocities where sustained flows are not expected.
(B) Except as specified in
				subsection (c)(1), the required design precipitation event for an impoundment
				meeting the spillway requirements of this section is as follows:
(i) For an impoundment meeting the size or
				other criteria of
				30
				CFR 77.216(a), a one hundred
				(100) year, six (6) hour event, or greater event as specified by the
				director.
(ii) 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 director.
(iii) For an impoundment not meeting the size
				or other criteria of
				30
				CFR 77.216(a) or not meeting
				the Class B or C criteria for dams in the NRCS publication Technical Release
				No. 60 (TR-60), a twenty-five (25) year, six (6) hour event, or greater event
				as specified by the director.
(8) The vertical portion of any remaining
				highwall must be located far enough below the low water line, along the extent
				of the highwall, to provide adequate safety and access for proposed water
				users. If surface run-off enters the impoundment, the side slope must be
				protected to prevent erosion.
(9) A
				qualified registered professional engineer or other qualified professional
				specialist under the direction of a professional engineer, either of whom shall
				be experienced in the construction of impoundments, shall inspect each
				impoundment according to the following provisions:
(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 shall, within thirty (30) days after each inspection required in
				clause (A), provide to the director a certified report that the impoundment has
				been constructed or maintained, or both, as designed and in accordance with the
				approved plan and this article. The report shall include discussion of the
				following:
(i) Any appearance of instability,
				structural weakness, or other hazardous condition.
(ii) Depth and elevation of any impounded
				waters.
(iii) Existing storage
				capacity.
(iv) Any existing or
				required monitoring procedures and instrumentation.
(v) Any other aspects of the structure
				affecting stability.
(C)
				A copy of the report shall be retained at or near the mine site.
(D) Impoundments subject to
				30
				CFR 77.216 or meeting the Class B or C
				criteria for dams in the NRCS publication Technical Release No. 60 (TR-60) must
				be examined in accordance with
				30
				CFR 77.216-3.
(E) Impoundments that do not meet the size or
				other criteria of
				30
				CFR 77.216(a) or do not meet
				the Class B or C criteria for dams in the NRCS publication Technical Release
				No. 60 (TR-60) shall be examined at least quarterly by a qualified person
				designated by the permittee for appearances of instability, structural
				weakness, or other hazardous conditions. At least one (1) of the quarterly
				examinations conducted during the calendar year shall be certified by a
				qualified registered professional engineer and shall include a discussion of
				any appearances of instability, structural weakness, or other hazardous
				conditions, any other aspects of the structure affecting stability, and a
				statement indicating the pond has been maintained in accordance with the
				approved plan and this section. This examination shall be conducted during the
				period of October 1 through December 31 of each calendar year. The certified
				examination report shall be submitted to the director within thirty (30) days
				of the examination. Impoundment examinations shall be conducted until the
				impoundment has been removed or until final bond release in accordance with
				312 IAC
				25-5-16. If the operator can demonstrate that failure
				of the structure would not create a potential threat to public health and
				safety or threaten significant environmental harm, the following impoundments
				shall be exempt from the examination requirements of this clause, following
				approval by the director:
(i) Impoundments
				that are completely incised.
(ii)
				Water impounding structures that impound water to a design elevation no more
				than five (5) feet above the upstream toe of the structure and that can have a
				storage volume of not more than twenty (20) acre-feet; provided the exemption
				request is accompanied by a report sealed by a qualified registered
				professional engineer licensed in the state of Indiana, accurately describing
				the hazard potential of the structure. Hazard potential must be such that
				failure of the structure would not create a potential threat to public health
				and safety or threaten significant environmental harm. The report shall be
				field verified by the director prior to approval and periodically thereafter.
				The director may terminate the exemption if so warranted by changes in the area
				downstream of the structure or in the structure itself.
(iii) Impoundments that do not facilitate
				mining or reclamation, including, but not limited to, the following:
(AA) Sewage lagoons.
(BB) Landscaping ponds.
(CC) Pools or wetlands in replaced stream
				channels.
(DD) Existing
				impoundments not yet used to facilitate mining.
(EE) Ephemeral waterbodies.
(FF) Active mining pits.
(GG) Differential settlement pools.
(10) If any
				examination or inspection discloses that a potential hazard exists, the person
				who examined the impoundment shall promptly inform the director of the finding
				and of the emergency procedures formulated for public protection and remedial
				action. If adequate procedures cannot be formulated or implemented, the
				director shall be notified immediately. The director shall then notify the
				appropriate agencies that other emergency procedures are required to protect
				the public.