Ill. Admin. Code tit. 62, § 1816.49 - Impoundments
a) 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 No. 60 (210-VI-TR60, October 1985), "Earth Dams and
Reservoirs," shall comply with "Minimum Emergency Spillway Hydrologic Criteria"
table in TR-60 and the requirements of this Section.
2) Impoundments meeting the size and other
qualifying criteria of
30
CFR 77.216(a) shall comply
with the requirements of
30
CFR 77.216(1998) and this
Section.
30
CFR 77.216 does not include any later
editions or amendments. The plan required to be submitted to the District
Manager of the Mine Safety and Health Administration (MSHA) under
30
CFR 77.216 shall also be submitted to the
Department as part of the permit application insofar as the MSHA informational
design standard requirements are duplicative of the requirements of 62 Ill.
Adm. Code 1780. In addition, the permittee shall submit to the Department any
certification issued by MSHA with respect to the design plan.
3) The design of impoundments shall be sealed
in accordance with 62 Ill. Adm. Code
1780.25(a)
as designed to meet the requirements of this Part using current, prudent
engineering practices. 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 subsection (a)(4)(A), except for a coal mine waste impounding
structure, and located where failure would not be expected to cause loss of
life or serious property damage shall have a minimum static safety factor of
1.3 for a normal pool
with steady state seepage saturation conditions, or meet the design,
construction and maintenance requirements of U.S. Natural Resources
Conservation Service Practice Standard IL 378, "Ponds," June 1992. Practice
Standard 378 is hereby incorporated by reference and does not include later
editions or amendments.
5) Impoundments shall have adequate freeboard
to resist overtopping by waves and by sudden increases in storage volume.
Impoundments meeting the SCS Class B or C criteria for dams in TR-60 shall
comply with the freeboard hydrology criteria in the "Minimum Emergency 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 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 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) Impoundments shall include a combination
of principal and emergency spillways which shall be designed and constructed to
safely pass the design precipitation event specified in subsection (b) or
(c).
10) 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, as evidenced by the placement of a registered
professional engineer's seal on the inspection report.
A) 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(a), shall be
inspected, examined and certified in accordance with
30
CFR 77.216. Annual status reports required
under
30
CFR 77.216-4 shall be submitted to the
Department within 30 days after the reporting period.
B) All other impoundments shall be inspected
at least quarterly during construction, provided at least one inspection is
conducted for impoundments completed in less than one quarter, and upon
completion of construction. The qualified registered professional engineer
shall submit to the Department within 30 days after each inspection, a sealed
report that the impoundment has been constructed as designed and in accordance
with the approved plan and these regulations.
C) A copy of the reports required in
subsections (a)(10)(A) and (B), and the examination reports required in
subsection (a)(11), shall be retained at or near the mine site. The Department
may approve reports being retained at a different location if there is no
permanent mine office.
11) Impoundments which do not meet 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 by a qualified person designated by the permittee for appearances of
instability, structural weakness or other hazardous conditions. At least one of
the quarterly examinations conducted during the calendar year shall be sealed
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 these regulations. This examination shall be conducted during
the period of October 1 through December 31 of each calendar year. The sealed
examination report shall be submitted to the Department within 30 days after
the examination. Impoundment examinations shall be conducted until the
impoundment has been removed or until final bond release in accordance with 62
Ill. Adm. Code
1800.40. If the
permittee 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 all
examination requirements of this subsection, following approval by the
Department:
A) Impoundments that are
completely incised;
B) Water
impounding structures that impound water to a design elevation no more than
five feet above the upstream toe of the structure and that can have a storage
volume of not more than 20 acre-feet; provided the exemption request is
accompanied by a report sealed by a registered professional engineer licensed
in the State of Illinois, 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
Department prior to approval and periodically thereafter. The Department may
terminate the exemption if so warranted by changes in the area downstream of
the structure or in the structure itself; and
C) Impoundments that do not facilitate mining
or reclamation including, but not limited to, sewage lagoons, landscaping
ponds, pools or wetlands in replaced stream channels, existing impoundments not
yet used to facilitate mining, ephemeral waterbodies, active mining pits and
differential settlement pools.
12) If any examination or inspection
discloses that a potential hazard exists, the person who examined the
impoundment shall promptly inform the Department of the finding and of the
emergency procedures formulated for public protection and remedial action. If
adequate procedures cannot be formulated or implemented, the Department shall
be notified immediately. The Department shall then notify the appropriate
agencies that other emergency procedures are required to protect the
public.
b) Permanent
impoundments. A permanent impoundment of water may be created, if authorized by
the Department in the approved permit, based upon the following demonstration:
1) The size and configuration of the
impoundment is adequate for its intended purposes.
2) The quality of impounded water will be
suitable on a permanent basis for its intended use and, after reclamation, will
meet water quality standards set forth in Section
1816.42,
and discharges from the impoundment will meet applicable effluent limitations
and will not degrade the quality of receiving water below water quality
standards set forth in Section 1816.42.
3) The water level will be sufficiently
stable and be capable of supporting the intended use.
4) Final grading will provide for adequate
safety and access for proposed water users.
5) The impoundment will not result in the
diminution of the quality and quantity of water utilized by adjacent or
surrounding landowners for agricultural, industrial, recreational, or domestic
uses.
6) The impoundment will be
suitable for the approved post-mining land use.
7) The impoundment perimeter slopes shall be
consistent with the intended use of the impoundment, not be steeper than the
angle of repose and comply with subsection (a)(4). Where surface runoff enters
the impoundment area, the side slope shall be protected against erosion.
A) Runoff from above the slope shall be
diverted to erosion free outlets.
B) Grading of slopes shall be scheduled to be
completed at the onset of the most favorable seeding period.
8) Embankment ponds, those having
embankment heights of three feet or greater above natural ground elevation,
shall have outslopes of 1v:2h or less and interior slopes to the normal pool
elevation of 1v:2h or less.
9)
Permanent impoundments
A) Permanent
impoundments not meeting the Class B or C criteria for dams in TR-60, or the
size or other qualifying criteria of
30
CFR 77.216(a), shall be
provided with a spillway that will safely discharge a 25 year, six hour
precipitation event, or such larger event as may be specified by the Department
based on factors such as terrain, topography and soil type.
B) Permanent impoundments meeting the size or
other criteria of
30
CFR 77.216(a) shall be
provided with a spillway that will safely discharge a 100 year, six hour
precipitation event, or such larger event as may be specified by the Department
based on factors such as terrain, topography and soil type.
C) Permanent impoundments meeting the Class B
or C criteria for dams in TR-60 shall be provided with a spillway that meets
the criteria in the "Minimum Emergency Spillway Hydrologic Criteria" table in
TR-60, or such larger event as may be specified by the Department based on
factors such as terrain, topography and soil type.
10) In lieu of the combination principal and
emergency spillway requirements of Section
1816.49(a)(9),
an impoundment may have a single spillway configured as set forth in
subsections (b)(10)(A) and (b)(10)(B) that is designed and constructed to
safely pass the applicable design precipitation specified in subsection (b)(9).
The Department shall approve a single open-channel spillway that is:
A) Of nonerodible construction and designed
to carry sustained flows; or
B)
Earth or grass-lined and designed to carry short-term, infrequent flows at
non-erosive velocities where sustained flows are not expected.
c) Temporary
impoundments
1) Temporary impoundments not
meeting the Class B or C criteria for dams in TR-60, or the size or other
qualifying criteria of
30
CFR 77.216(a), shall be
provided with a spillway that will safely discharge a 25 year, six hour
precipitation event or such larger event as may be required by the Department
based on factors such as terrain, topography and soil type. Temporary
impoundments meeting the size or other criteria of
30
CFR 77.216(a) shall be
provided with a spillway that will safely discharge a 100 year, six hour
precipitation event, or such larger event as may be specified by the Department
based on factors such as terrain, topography and soil type. Temporary
impoundments meeting the Class B or C criteria for dams in TR-60 shall be
provided with a spillway that meets the criteria in the "Minimum Emergency
Spillway Hydrologic Criteria" table in TR-60 or such larger event as may be
specified by the Department based on factors such as terrain, topography and
soil type.
2) In lieu of the
combination principal and emergency spillway requirements of Section
1816.49(a)(9),
an impoundment may have either:
A) A single
spillway configured as set forth in subsection (c)(2)(A)(i) or (c)(2)(A)(ii)
that is designed and constructed to safely pass the applicable design
precipitation specified in subsection (c)(1). The Department shall 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; or
B) Sufficient spillway capacity to safely
pass, adequate storage capacity to safely contain, or a combination of storage
capacity and spillway capacity to safely control the design precipitation event
when it is demonstrated by the permittee and certified by a qualified
registered professional engineer in accordance with 62 Ill. Adm. Code
1780.25(a)
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. Impounding structures relying on this method to control
runoff shall be located where failure would not be expected to cause loss of
life or serious property damage, except where:
i) In the case of an impoundment meeting the
SCS Class B or C criteria for dams in TR-60, or 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 6-hour event, or greater event as specified by the Department.
ii) In the case of an impoundment not
included in subsection (c)(2)(B)(i), it is designed to control the
precipitation of a 100-year 6-hour event, or greater event as specified by the
Department.
Notes
Amended at 24 Ill. Reg. 5967, effective March 21, 2000
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