Current through March 20, 2024
Authority: IC 14-10-2-4; IC 14-34-2-1
Affected: IC 14-34
Sec. 20.
(a) This
section applies to both temporary and permanent impoundments and must satisfy
the following conditions:
(1) An impoundment
meeting the:
(A) Class B or C criteria for
dams in the NRCS publication Technical Release No. 60 (TR-60); or
(B) 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 25-4-49 as designed to meet the requirements 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:
(i) Class B or C criteria for
dams in the NRCS publication Technical Release No. 60 (TR-60); or
(ii) 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:
(i) Class B or C criteria for dams in the
NRCS publication Technical Release No. 60 (TR-60); or
(ii) 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) Instead 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:
(A) stable
during all phases of construction and operation; and
(B) 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 the following:
(A) Surface
erosion at the site.
(B) 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:
(AA) size or other criteria of
30
CFR 77.216(a); or
(BB) 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:
(i) regularly during construction;
(ii) upon completion of construction;
and
(iii) 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:
(i) subject to
30
CFR 77.216; or
(ii) 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, and 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)
Impoundments that are entirely contained within an incised structure such that
the incised structure would completely contain the waters of the impoundment
should failure occur and failure would not create a potential threat to public
health and safety or threaten significant environmental harm.
(iii) Water impounding structures that:
(AA) impound water to a design elevation not
more than five (5) feet above the upstream toe of the structure; and
(BB) 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 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 before
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.
(iv)
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 water bodies.
(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 impoundments 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:
(A)
agricultural;
(B)
industrial;
(C) recreational;
or
(D) 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
impoundments 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 (33 1/3%) or the lesser slope needed
to do the following:
(A) Protect the public
health and safety.
(B) Enable the
permittee to do the following:
(i) Place
topsoil on the slope under section 11 of this rule.
(ii) Revegetate the slope under sections 54
through 61 of this rule.
(c) The director may authorize the
construction of temporary impoundments as part of a surface coal mining
operation. Instead 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:
(A) Class B or C criteria for dams in the
NRCS publication Technical Release No. 60 (TR-60); or
(B) 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:
(A) size or other criteria of
30
CFR 77.216(a); or
(B) 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 under
sections 54 through 61 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:
(1)
in which the vegetation is not successful; or
(2) where rills and gullies develop;
shall be repaired and revegetated under sections 51 and 54
through 61 of this rule.
(e) Plans for any enlargement, reduction in
size, reconstruction, or other modification of dams or impoundments shall:
(1) be submitted to the director;
and
(2) 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.