| (a) General Requirements.
(1) With the approval of the Commission, any flow from
mined areas abandoned before May 3, 1978, and any flow from undisturbed
areas or reclaimed areas, after meeting the criteria of §12.344
of this title (relating to Hydrologic Balance: Sedimentation Ponds)
for siltation structures removal, may be diverted from disturbed areas
by means of temporary or permanent diversions. All diversions shall
be designed to minimize adverse impacts to the hydrologic balance
within the permit and adjacent areas, to prevent material damage outside
the permit area and to assure the safety of the public. Diversions
shall not be used to divert water into underground mines without approval
of the Commission under §12.353 of this title (relating to Hydrologic
Balance: Discharge of Water Into an Underground Mine).
(2) The diversion and its appurtenant structures shall
be designed, located, constructed, maintained and used to:
(A) be stable;
(B) provide protection against flooding and resultant
damage to life and property;
(C) prevent, to the extent possible using the best
technology currently available, additional contributions of suspended
solids to streamflow outside the permit area; and
(D) comply with all applicable local, state, and federal
laws and regulations.
(3) Temporary diversions shall be removed when no longer
needed to achieve the purpose for which they were authorized. The
land disturbed by the removal process shall be restored in accordance
with §§12.330-12.340, this section, and §§12.342-12.403
of this title (relating to Permanent Program Performance Standards--Surface
Mining Activities). Before diversions are removed, downstream water-treatment
facilities previously protected by the diversion shall be modified
or removed, as necessary, to prevent overtopping or failure of the
facilities. This requirement shall not relieve the operator from maintaining
water-treatment facilities as otherwise required. A permanent diversion
or a stream channel reclaimed after the removal of a temporary diversion
shall be designed and constructed so as to restore or approximate
the premining characteristics of the original stream channel including
the natural riparian vegetation to promote the recovery and the enhancement
of aquatic habitat.
(4) Diversion designs shall incorporate the following:
(A) be constructed with gentle sloping banks that are
stabilized by vegetation. Asphalt, concrete or other similar linings
shall be used only when approved by the Commission to prevent seepage
or to provide stability. Channel linings shall be designed using standard
engineering practices to pass safely the design velocities and shall
be approved for permanent diversions only where they are stable and
will require infrequent maintenance;
(B) erosion protection shall be provided for transition
of flows and for critical areas such as swales and curves;
(C) energy dissipators shall be installed when necessary
at discharge points, where diversions intersect with natural streams
and exit velocities of the diversion ditch flow is greater than that
of the receiving stream;
(D) excess excavated material not necessary for diversion
channel geometry or regrading of the channel shall be disposed of
in accordance with §§12.363-12.366 of this title (relating
to Disposal of Excess Spoil: General Requirements, to Disposal of
Excess Spoil: Valley Fills, to Disposal of Excess Spoil: Head-of-Hollow
Fills, and to Disposal of Excess Spoil: Durable Rock Fills); and
(E) topsoil shall be handled in compliance with §§12.334-12.338
of this title (relating to Topsoil: General Requirements, to Topsoil:
Removal, to Topsoil: Storage, to Topsoil: Redistribution, and to Topsoil:
Nutrients and Soil Amendments).
(b) Diversions of Perennial and Intermittent Streams.
(1) Diversions of perennial and intermittent streams
within the permit area may be approved by the Commission after making
the finding relating to stream buffer zones that the diversion will
not adversely affect the water quantity and quality and related environmental
resources of the stream.
(2) The design capacity of channels for temporary and
permanent stream channel diversions shall be at least equal to the
capacity of the unmodified stream channel immediately upstream and
downstream from the diversion.
(3) The requirements of subsection (a)(2)(B) of this
section shall be met when the temporary and permanent diversions for
perennial and intermittent streams are designed so that the combination
of channel, bank and floodplain configuration is adequate to pass
safely the peak runoff of a 10-year, 6-hour precipitation event for
a temporary diversion and a 100-year, 6-hour precipitation event for
a permanent diversion.
(4) The design and construction of all stream channel
diversions of perennial and intermittent streams shall be certified
by a qualified professional engineer as meeting the performance standards
of this part and any design criteria set by the Commission.
(c) Diversion of Miscellaneous Flows.
(1) Miscellaneous flows, which consists of all flows
except for perennial and intermittent streams, may be diverted away
from disturbed areas if required or approved by the Commission. Miscellaneous
flows shall include ground-water discharges and ephemeral streams.
(2) The design, location, construction, maintenance,
and removal of diversions of miscellaneous flows shall meet all of
the performance standards set forth in subsection (a) of this section.
(3) The requirements of subsection (a)(2)(B) of this
section shall be met when the temporary and permanent diversions for
miscellaneous flows are designed so that the combination of channel,
bank and flood-plain configuration is adequate to pass safely the
peak runoff of a 2-year, 6-hour precipitation event for a temporary
diversion and a 10-year, 6-hour precipitation event for a permanent
diversion.
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