(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 §12.148(c) 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 30 CFR 77.216(a), 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 user.
(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.
(b) Permanent Impoundments. A permanent impoundment
of water may be created, if authorized by the Commission in the approved
permit based upon the following demonstration:
(1) the size and configuration of such impoundment
will be 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 applicable state and federal water-quality standards, and
discharges from the impoundment will meet applicable effluent limitations
and will not degrade the quality of receiving water below applicable
state and federal water-quality standards;
(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 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; and
(6) the impoundment will be suitable for the approved
postmining land use.
(c) Temporary Impoundments.
(1) The Commission may authorize the construction of
temporary impoundments as part of a surface coal mining operation.
(2) In lieu of meeting the requirements of subsection
(a)(9)(A) of this section, the Commission may approve an impoundment
that relies primarily on storage to control the runoff from the design
precipitation event when it is demonstrated by the operator and certified
by a qualified 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:
(A) 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(a), shall be designed to control the precipitation
of the probable maximum precipitation of a 6-hour event, or greater
event as specified by the Commission; and
(B) impoundments not included in subparagraph (A) of
this paragraph shall be designed to control the precipitation of the
100-year, 6-hour event, or greater event as specified by the Commission.
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