(a) Scope. For the purposes of this section only, disturbed
areas shall not include those areas:
(1) in which the only surface mining activities include
diversion ditches, siltation structures, or roads that are designed,
constructed and maintained in accordance with §§12.330-12.343,
this section, and §§12.345-12.403 of this title (relating
to Permanent Program Performance Standards--Surface Mining Activities);
and
(2) for which the upstream area is not otherwise disturbed
by the operator.
(b) General requirements.
(1) Additional contributions of suspended solids sediment
to streamflow or runoff outside the permit area shall be prevented
to the extent possible using the best technology currently available.
(2) All surface drainage from the disturbed area shall
be passed through a siltation structure before leaving the permit
area, except as provided in paragraph (5) of this subsection or subsection
(e) of this section.
(3) Siltation structures for an area shall be constructed
before beginning any surface mining activities in that area, and upon
construction shall be certified by a qualified professional engineer
to be constructed as designed and as approved in the reclamation plan.
(4) Any siltation structure which impounds water shall
be designed, constructed and maintained in accordance with §12.347
of this title (relating to Hydrologic Balance: Permanent and Temporary
Impoundments).
(5) Siltation structures shall be maintained until
the disturbed area has been stabilized and revegetated and removal
is authorized by the Commission. In no case shall the structure be
removed sooner than two years after the last augmented seeding.
(6) When a siltation structure is removed, the land
on which the siltation structure was located shall be regraded and
revegetated in accordance with the reclamation plan and §§12.390-12.395
of this title (relating to Revegetation: General Requirements, to
Revegetation: Use of Introduced Species, to Revegetation: Timing,
to Revegetation: Mulching and Other Soil Stabilizing Practices, and
to Revegetation: Standards for Success). Sedimentation ponds approved
by the Commission for retention as permanent impoundments may be exempted
from this requirement.
(c) Sedimentation ponds.
(1) When used, sedimentation ponds shall:
(A) be used individually or in series;
(B) be located as near as possible to the disturbed
area and out of perennial streams unless approved by the Commission;
and
(C) be designed, constructed, and maintained to:
(i) provide adequate sediment storage volume. The minimum
sediment storage volume shall be equal to the three year accumulated
sediment volume from the drainage area to the pond. The sediment volume
shall be determined using the Universal Soil Loss Equation, gully
erosion rates, and the sediment delivery ratio converted to sediment
volume, using either the sediment density or other empirical methods
approved by the Commission;
(ii) provide adequate detention time to allow the effluent
from the ponds to meet state and federal effluent limitations. The
minimum detention time without a chemical treatment process shall
be 10 hours;
(iii) contain or treat the 10-year, 24-hour precipitation
event ("design event") unless a lesser design event is approved by
the Commission based on terrain, climate, other site-specific conditions
and on a demonstration by the operator that the effluent limitations
of §12.340 of this title (relating to Hydrologic Balance: Water-Quality
Standards and Effluent Limitations) will be met;
(iv) provide a nonclogging dewatering device adequate
to maintain the detention time required under clause (ii) of this
subparagraph;
(v) minimize, to the extent possible, short circuiting;
(vi) provide periodic sediment removal sufficient to
maintain adequate volume for the design event;
(vii) ensure against excessive settlement;
(viii) be free of sod, large roots, frozen soil, and
acid- or toxic-forming coal-processing waste; and
(ix) be compacted properly.
(2) A sedimentation pond shall include either a combination
of principal and auxiliary spillways or single spillway configured
as specified in §12.347(a)(9) of this title (relating to Hydrologic
Balance: Permanent and Temporary Impoundments).
(d) Other treatment facilities.
(1) Other treatment facilities shall be designed to
treat the 10-year, 24-hour precipitation event unless a lesser design
event is approved by the Commission based on terrain, climate, other
site-specific conditions and a demonstration by the operator that
the effluent limitations of §12.340 of this title (relating to
Hydrologic Balance: Water-Quality Standards and Effluent Limitations)
will be met.
(2) Other treatment facilities shall be designed in
accordance with the applicable requirements of subsection (c) of this
section.
(e) Exemptions. Exemptions to the requirements of this
section may be granted if:
(1) the disturbed drainage area within the total disturbed
area is small; and
(2) the operator demonstrates that siltation structures
and alternate sediment control measures are not necessary for drainage
from the disturbed area to meet the effluent limitations under §12.340
of this title (relating to Hydrologic Balance: Water-Quality Standards
and Effluent Limitations) and the applicable state and federal water-quality
standards for the receiving waters.
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