§ 880-X-10D-.17. Hydrologic Balance: Siltation Structures
(1) Definitions. For the purposes of this Section only:
(b) Disturbed area shall not include those areas --
1. In which the only underground mining activities include diversion ditches, siltation structures, or roads that are designed, constructed and maintained in accordance with this part; and
2. For which the upstream area is not otherwise disturbed by the operator.
(c) Other treatment facilities mean any chemical treatments, such as flocculation or neutralization, or mechanical structures, such as clarifiers or precipitators, that have a point source discharge and are utilized:
(1) To prevent additional contributions of dissolved or suspended soils to streamflow or runoff outside the permit area, or
(2) To comply with all applicable State and Federal water-quality laws and regulations.
(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 underground 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-10D-.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-10D-.52 through 880-X-10D-.57. 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, and
3. 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-10D-.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 880-X-10D-.02(1)(i).
(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-10D-.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-10D-.13 and the applicable State and Federal water quality standards for the receiving waters.
Author: Randall C. Johnson(May 20, 1982. Amended: September 18, 1990; effective August 2, 1991. Amended: Filed July 27, 1998; effective August 31, 1998; operative January 3, 1999.)
On December 4, 1998, the Office of Surface Mining approved this rulemaking adopted by the commission on July 16, 1998. The effective date of this rule will be January 3, 1999.
Statutory Authority: Code of Ala. 1975, §§ 9-16-71, 72, 73, 74, 75, 76, 80, 84, 90, 92, 97.
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