Ala. Admin. Code r. 880-X-10C-.17
Current through Register Vol. 42, No. 8, May 31, 2024
Section 880-X-10C-.17 - Hydrologic Balance: Siltation Structures(1) Definitions. For the purposes of this Section only: (a) Siltation structure means a sedimentation pond, a series of sedimentation ponds, or other treatment facility.(b) Disturbed area 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 this part; and2. For which the upstream area is not otherwise disturbed by the operator.(c) Other treatment facilities means any chemical treatments, such as flocculation, or mechanical structures, such as clarifiers, that have a point-source discharge and that are utilized to prevent additional contribution of suspended solids to streamflow or runoff outside the permit area.(2) General requirements.(a) 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.(b) All surface drainage from the disturbed area shall be passed through a siltation structure before leaving the permit area, except as provided in Paragraph (2)(e) or (5) of this Section.(c) 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 to be constructed as designed and as approved in the reclamation plan.(d) Any siltation structure which impounds water shall be designed, constructed and maintained in accordance with 880-X-10C-.20.(e) Siltation structures shall be maintained until removal is authorized by the Regulatory Authority 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.(f) 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 880-X-10C-.58 through 880-X-10C-.63. Sedimentation ponds approved by the Alabama Surface Mining Commission for retention as permanent impoundments may be exempted from this requirement.(3) Sedimentation ponds.(a) When used, sedimentation ponds shall --1. Be used individually or in series;2. Be located as near as possible to the disturbed area and out of perennial streams unless approved by the Regulatory Authority, and3. Be designed, constructed, and maintained to --(i) Provide adequate sediment storage volume;(ii) Provide adequate detention time to allow the effluent from the ponds to meet State and Federal effluent limitations;(iii) Contain or treat the 10-year, 24-hour precipitation event ("design event") unless a lesser design event is approved by the Alabama Surface Mining Commission based on terrain, climate, other site-specific conditions and on a demonstration by the operator that the effluent limitations of 880-X-10C-.13 will be met;(iv) Provide a nonclogging dewatering device adequate to maintain the detention time required under Paragraph (3)(a)3(ii).(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.(b) Spillways. A sedimentation pond shall include either a combination of principal and emergency spillways or a single spillway configured as specified in paragraph (3) (b)1. of this section, designed and constructed to safely pass the applicable design precipitation event specified in paragraph (3)(b)2. of this section, except as set forth in paragraph (3)(b)3. of this section. 1. The Alabama Surface Mining Commission may approve a single open-channel spillway that is: (i) Of nonerodible construction and designed to carry sustained flows; or(ii) Earth- or grass-lined and designed to carry short-term infrequent flows at non-erosive velocities where sustained flows are not expected.2. Except as specified in paragraph (3)(b)3. of this section, the required design precipitation event for a sedimentation pond meeting the spillway requirements of paragraph (3)(b) of this section is:(i) For a sedimentation pond meeting the size or other criteria of 30 CFR 77.216(a), a 100-year 6-hour event, or greater event as specified by the Alabama Surface Mining Commission.(ii) For a sedimentation pond not meeting the size or criteria of 30 CFR 77.216(a), a 25-year 6-hour event, or greater event as specified by the Alabama Surface Mining Commission.3. In lieu of meeting the requirements in paragraph (3)(b)1. of this section, the Alabama Surface Mining Commission may approve a sedimentation pond that relies primarily on storage to control the runoff from the design precipitation event when it is demonstrated by the operator and certified by a qualified registered professional engineer that the sedimentation pond will safely control the design precipitation event, the water from which shall be safely removed in accordance with current, prudent, engineering practices. Such a sedimentation pond shall be located where failure would not be expected to cause loss of life or serious property damage, except where:(i) In the case of a sedimentation pond meeting the size or other criteria of 30 CFR 77.216(a), it is designed to control the precipitation of the probable maximum precipitation of a 6-hour event, or greater event as specified by the Alabama Surface Mining Commission; or(ii) In the case of a sedimentation pond not meeting the size or other criteria of 30 CFR 77.216(a), it is designed to control the precipitation of a 100-year 6-hour event, or greater event as specified by the Alabama Surface Mining Commission.(4) Other treatment facilities.(a) Other treatment facilities shall be designed to treat the 10-year, 24-hour precipitation event unless a lesser design event is approved by the Alabama Surface Mining Commission based on terrain, climate, other site-specific conditions and a demonstration by the operator that the effluent limitations of 880-X-10C-.13 will be met.(b) Other treatment facilities shall be designed in accordance with the applicable requirements of Paragraph (3) of this Section.(5) Exemptions. Exemptions to the requirements of this Section may be granted if -- (a) The disturbed drainage area within the total disturbed area is small; and(b) 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 880-X-10C-.13 and the applicable State and Federal water quality standards for the receiving waters.Author: Randall C. Johnson
Ala. Admin. Code r. 880-X-10C-.17
May 20, 1982. Amended: September 18, 1990; effective: August 2, 1991.Statutory Authority:Code of Ala. 1975, §§ 9-16-71, 72, 73, 74, 75, 76, 80, 84, 90, 92, 97.