Okla. Admin. Code § 460:20-43-10

Current through Vol. 42, No. 7, December 16, 2024

Section 460:20-43-10 - Diversions

(a)General requirements.

(1) With the approval of the Department, any flow from mined areas abandoned before May 3, 1978, and any flow from undisturbed areas or reclaimed areas, after meeting the criteria of Section 460:20-43-12 for siltation structure 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 Department under Section 460:20-43-8(i).

(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 promptly 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 this part. 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 the aquatic habitat.

(4) Temporary diversions shall be constructed to pass safely the peak runoff from a precipitation event with a 2-year, 6-hour recurrence interval or a larger event as specified by the Department.

(5) To protect fills and property and to avoid danger to public health and safety permanent diversions shall be constructed to pass safely the peak runoff from a 6-hour, 10-year precipitation event or a larger event as specified by the Department. Permanent diversions shall be constructed with gently sloping banks that are stabilized by vegetation. Asphalt, concrete or other similar linings shall be used only when approved by the Department to prevent seepage or to provide stability.

(6) Diversions shall be designed, constructed and maintained in a manner which prevents additional contributions of suspended solids to streamflow and to runoff outside the permit area to the extent possible using the best technology currently available. Appropriate sediment control measures for these diversions may include, but not be limited to maintenance of appropriate gradients, channel linings, revegetation, roughness structures, and detention basins.

(7) No diversion shall be located so as to increase the potential for landslides. No diversion shall be constructed on existing landslides unless approved by the Department.

(8) When no longer needed, each temporary diversion shall be removed, and the affected land regraded, topsoiled, and revegetated in accordance with these Regulations.

(9) Diversion design shall incorporate the following:

(A) channel lining shall be designed using standard engineering practices to pass safely the design velocities. Riprap shall be nondegradable, nonacid or toxic forming rock such as natural sand and gravel, sandstone, limestone, or other durable rock that will not slake in water and will be free of coal, clay, or shale.

(B) Freeboard shall be no less than 0.3 feet. Protection shall be provided for transition of flows and for critical areas such as swales and curves. Where the area protected is a critical area as determined by the Department, the design freeboard may be increased.

(C) Energy dissipators shall be installed when necessary at discharge points. Where diversions intersect with natural steams and exit velocity 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 Sections 460:20-43-24, through 460:20-43-27.

(E) Topsoil shall be handled in compliance with Section 460:20-43-7.

(F) Diversions shall not be constructed or operated to divert water into underground mines without approval of the Department.

(b)Diversion of perennial and intermittent streams.

(1) Diversion of perennial and intermittent streams within the permit area may be approved by the Department 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 (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 flood-plain 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 registered professional engineer as meeting the performance standards of this Subchapter and any design criteria set by the Department.

(5) Flow from perennial and intermittent streams within the permit area may be diverted, if the diversions:

(A) Are approved by the Department after making the findings called for in Section 460:20-43-16(a);

(B) Comply with other requirements of this Subchapter; and

(C) Comply with local, State, and Federal statutes and regulations.

(6) When streamflow is allowed to be diverted, the stream channel diversion shall be designed, constructed, and removed, in accordance with the following:

(A) The longitudinal profile of the stream, the channel and the flood-plain shall be designed and constructed to remain stable and to prevent to the extent possible using the best technology currently available, additional contributions of suspended solids to stream-flow or to runoff outside the permit area. These contributions shall not be in excess of requirements of State or Federal law. Erosion control structures such as channel lining structures, retention basins, and artificial channel roughness structures shall be used in diversions only when approved by the Department of Mines as being necessary to control erosion. These structures shall be approved for permanent diversions only where they are stable and will require infrequent maintenance;

(B) The combination of channel bank and flood-plain configurations shall be adequate to pass safely the peak runoff of a 10-year, 6-hour precipitation event for temporary diversions, a 100-year 24-hour precipitation event for permanent diversions or larger events as specified by the Department. However, the capacity of the channel itself shall be at least equal to the capacity of the unmodified stream channel immediately upstream and downstream of the diversion.

(7) When no longer needed to achieve the purpose for which they were authorized, all temporary stream channel diversions shall be removed and the affected land regraded and revegetated in accordance with Sections 460:20-43-9, 460:20-43-11, 460:20-43-37 through 460:20-43-40 and 460:20-43-43 through 460:20-43-46. At the time diversions are removed downstream water treatment facilities previously protected by the diversion shall be modified or removed to prevent overtopping or failure of the facilities. This requirement shall not relieve the operator who conducts the surface mining activities from maintenance of a water treatment facility required under this Subchapter of the permit.

(8) When permanent diversions are constructed or stream channels restored, after temporary diversions, the operator shall:

(A) Restore, enhance where practicable, or maintain natural riparian vegetation on the banks of the stream;

(B) Establish or restore the stream to its natural meandering shape of an environmentally acceptable gradient, as determined by the Department;

(C) Establish or restore the stream to a longitudinal profile and cross-section, including aquatic habitats (usually a patter of riffles, pools, and drops rather than a uniform depth) that approximate premining stream channel characteristics.

(c)Diversion of miscellaneous flows.

(1) Miscellaneous flows, which consist of all flows except for perennial and intermittent streams, may be diverted away from disturbed areas if required or approved by the Department. 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 Chapter:

(3) The requirements of (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.

Okla. Admin. Code § 460:20-43-10