(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.

Source Note: The provisions of this §12.341 adopted to be effective November 4, 1997, 22 TexReg 10640; amended to be effective December 28, 2020, 45 TexReg 9503