Oklahoma Administrative Code
Title 460 - Department of Mines
Chapter 20 - The Permanent Regulations Governing the Coal Reclamation Act of 1979
Subchapter 43 - Permanent Program Performance Standards: Surface Mining Standards
Section 460:20-43-12 - Hydrologic balance: siltation structures

(1) In which the only surface mining activities include diversion ditches, siltation structures, or roads that are designed, constructed and maintained in accordance with this Subchapter; and

(2) For which the upstream area is not otherwise disturbed by the operator.

(1) Additional contributions of suspended solids sediment to stream flow 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 controlled through use of a siltation structure, a series of siltation structures, or such alternative techniques as provided in Section 460:20-43-11 of this Chapter before leaving the permit area.

(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 registered professional engineer or registered professional land surveyor to be constructed as designed and as approved in the reclamation plan. The certifying engineer or land surveyor shall have experience in pond construction.

(4) Any siltation structure which impounds water shall be designed, constructed and maintained in accordance with Section 460:20-43-14 of this Chapter.

(5) Siltation structures shall be maintained until removal is authorized by the Department and the disturbed area has been stabilized and revegetated. In no case shall the structure be removed sooner than 2 years after the last augmented seeding.

(6) When 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 Sections 460:20-43-43, through 460:20-43-46 of this Chapter. Sedimentation ponds approved by the Department for retention as permanent impoundments may be exempted from this requirement.

(1) When used, sedimentation ponds shall:

(2) Spillways. A sedimentation pond shall include a combination of principal and emergency spillways or a single spillway configured as specified in (c)(2)(A) of this Section, designed and constructed to safely pass the applicable design precipitation event specified in (c)(2)(B) of this section, except as set forth in (c)(2)(C) of this section.

(1) Other treatment facilities shall be designed to treat 10-year, 24-hour precipitation event unless a lesser design event is approved by the Department based on terrain, climate, other site-specific conditions and a demonstration by the operator that the effluent limitations of Section 460:20-43-9 will be met.

(2) Other treatment facilities shall be designed in accordance with the applicable requirements of Subsection (c) of this Section.

(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 Section 460:20-45-9 and the applicable State and Federal water quality standards for the receiving waters.

(1) General requirements. Sedimentation ponds shall be used individually or in series and shall:

(2) Sediment ponds shall provide adequate sediment storage per acre of disturbance draining into the structure.

(3) Detention time. Sedimentation ponds shall provide the required theoretical detention time for the water inflow or runoff entering the pond from a 10-year, 24-hour precipitation event (design event).

(4) Dewatering. The water storage resulting from inflow shall be removed by a non-clogging dewatering device or a conduit spillway approved by the Department.

(5) Each operator who conducts surface mining activities shall design, construct, and maintain sedimentation ponds to prevent short-circuiting to the extent possible.

(6) The design, construction, and maintenance of a sedimentation pond or other sediment control measures in accordance with this Section shall not relieve the operator from compliance with applicable effluent limitations as contained in Section 460:20-43-9.

(7) There shall be no out-flow through the emergency spillway during the passage of the runoff resulting from the 10-year, 24-hour precipitation event or lesser events through the sedimentation pond.

(8) An appropriate combination of principal and emergency spillways or a single open channel spillway as specified in Section 460:20-43-9(c)(2) shall be provided to safely discharge the runoff from a 25-year, 6-hour precipitation event, or large event specified by the Department. The elevation of the crest of the emergency spillway shall be a minimum of 1.0 foot above the crest of the principal spillway. Emergency spillway grades and allowable velocities shall be approved by the Department.

(9) The minimum elevation at the top of the settled embankment shall be 1.0 foot above the water surface in the pond with the emergency spillway flowing at design depth. For embankments subject to settlement, this 1.0 foot minimum elevation requirement shall apply at all times including the period after settlement.

(10) The constructed height of the dam shall be increased a minimum of 5 percent over the design height to allow for settlement unless it has been demonstrated to the Department that the material used and the design will ensure against all settlement.

(11) The minimum top width of the embankment shall not be less than the quotient of (h+35)/5, where H is the height, in feet, of the embankment as measured from the upstream toe of the embankment.

(12) The combined upstream and downstream side slopes of the settled embankment shall not be less than 1v:5H, with neither slope steeper than1v:2h. Slopes shall be designed to be stable in all cases, even if flatter side slopes are required.

(13) The embankment foundation area shall be cleared of all organic matter, all surface sloped to no steeper than 1v:1h, and the entire foundation surface scarified.

(14) The fill material shall be free of sod, large roots, other large vegetative matter, and frozen soil and in no case shall coal-processing waste be used.

(15) The placing and spreading of fill material shall be started at the lowest point of the foundation. The fill shall be brought up in horizontal layers of such thickness as is required to facilitate compaction and meet the design requirements of this Section. Compaction shall be conducted as specified in the design approved by the Department.

(16) If a sedimentation pond has an embankment that is more than 20 feet in height, as measured from the upstream toe of the embankment to the crest of the emergency spillway, or has a storage volume of 20 acre-feet or more, the following additional requirements shall be met;

(17) Each pond shall be designed and inspected during construction under the supervision of and certified after construction by a qualified registered professional engineer.

(18) The entire embankment including the surrounding areas disturbed by construction shall be stabilized with respect to erosion by a vegetative cover or other means immediately after the embankment is completed. The active upstream face of the embankment where water will be impounded may be riprapped or otherwise stabilized. Areas in which the vegetation is not successful or where rills and gullies develop shall be repaired and revegetated in accordance with Section 460:20-43-41.

(19) All ponds including those not meeting the size or other criteria of 30 CFR 77.216(a) shall be examined for structural weakness, erosion and other hazardous conditions and reports and modifications shall be made to the Department in accordance with 30 CFR 77.216-3. With the approval of the Department, dams not meeting these criteria [77.216(a)] shall be examined four times per year.

(20) Sedimentation ponds shall not be removed until the disturbed area has been restored, and the revegetation requirements of Section 460:20-43-43 through 460:20-43-46 are met and the drainage entering the pond has met the applicable State and Federal water quality requirements for the receiving stream. When the sedimentation pond is removed, the affected land shall be regraded and revegetated in accordance with Sections 460:20-43-37, through 460:20-43-41, and 460:20-43-43, through 460:20-43-46, unless the pond has been approved by the Department for retention as being compatible with the approved postmining land use under Section 460:20-43-51. If the Department approves retention, the sedimentation pond shall meet all requirements for permanent impoundments of Sections 460:20-43-14 and 460:20-43-15.