312 IAC 25-6-84 - Underground mining; hydrologic balance; permanent and temporary impoundments
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.
(b)
Permanent impoundments of water may be authorized by the director upon the
basis of the following demonstration:
(1) The
quality of the impounded water shall be suitable, on a permanent basis, for its
intended use and, after reclamation, will meet applicable Indiana and federal
water quality standards, and discharge of water from the impoundment will meet
applicable effluent limitations and shall not degrade the quality of receiving
waters to less than the water quality standards established under applicable
Indiana and federal laws.
(2) The
level of water shall be sufficiently stable to support the intended
use.
(3) Water impoundments shall
not result in the diminution of the quality or quantity of water used by
adjacent or surrounding landowners for agricultural, industrial, recreational,
or domestic uses.
(4) The size and
configuration of the impoundment are adequate for the intended purposes. The
impoundment has an adequate freeboard to resist overtopping by waves and by
sudden increases in storage volume.
(5) The impoundment will be suitable for the
approved postmining land use.
(6)
The design, construction, and maintenance of structures shall achieve the
minimum design requirements applicable to structures constructed and maintained
under the Watershed Protection and Flood Prevention Act, P.L. 83-566
(16 U.S.C.
1006).
(7) Final grading will provide for adequate
safety and access for proposed water users.
(8) For final cut and permanent incised
impoundments, final graded slopes down to the water level shall not exceed in
grade thirty-three and one-third percent (33a%) or the lesser slope needed to
do the following:
(A) Protect the public
health and safety.
(B) Enable the
permittee to place topsoil on the slope under section 75 of this rule and to
revegetate the slope under sections 115 through 122 of this rule.
(c) The director may
authorize the construction of temporary impoundments as part of an underground
coal mining operation. In lieu of meeting the requirements in subsection
(a)(7)(A), the director may approve an impoundment that relies primarily on
storage to control the run-off from the design precipitation event when it is
demonstrated by the operator and certified by a qualified registered
professional engineer that the impoundment will safely control the design
precipitation event, the water from which shall be safely removed in accordance
with current, prudent engineering practices. Such an impoundment shall be
located where failure would not be expected to cause loss of life or serious
property damage, except where in the case of an impoundment:
(1) meeting the Class B or C criteria for
dams in the NRCS publication Technical Release No. 60 (TR-60) or meeting the
size or other criteria of
30
CFR 77.216(a), it is
designed to control the precipitation of the probable maximum precipitation of
a six (6) hour event or greater event as specified by the director;
or
(2) 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), it is designed to control the precipitation of a one hundred
(100) year, six (6) hour event, or greater event as specified by the
director.
(d) All
embankments of temporary and permanent impoundments, and surrounding areas and
diversion ditches disturbed or created by construction, shall be graded,
fertilized, seeded, and mulched to comply with the requirements of sections 115
through 122 of this rule after the embankment is completed. The active,
upstream face of the embankment where water is impounded may be riprapped or
otherwise stabilized. Areas in which the vegetation is not successful or where
rills and gullies develop shall be repaired and revegetated to comply with the
requirements of sections 115 through 122 of this rule.
(e) Plans for any enlargement, reduction in
size, reconstruction, or other modification of dams or impoundments shall be
submitted to the director and shall comply with the requirements of this
section. Except where a modification is required to eliminate an emergency
condition constituting a hazard to public health, safety, or the environment,
the director shall approve the plans before modification begins.
Notes
State regulations are updated quarterly; we currently have two versions available. Below is a comparison between our most recent version and the prior quarterly release. More comparison features will be added as we have more versions to compare.
No prior version found.