30 CFR 817.46 - What requirements apply to siltation structures?
(a)Scope. For the purpose of this section only, the phrase “disturb the land surface” does not include those areas -
(1) In which the only underground mining activities conducted on the land surface consist of diversions, siltation structures, or roads that are designed, constructed, and maintained in accordance with this part; and
(1) When siltation structures will be used to achieve the requirements of § 817.45 of this part, you must construct those structures before beginning any underground mining activities that will disturb the land surface.
(2) Upon completion of construction of a siltation structure, a qualified registered professional engineer, or, in any state that authorizes land surveyors to prepare and certify plans in accordance with § 784.25(a) of this chapter, a qualified registered professional land surveyor, must certify that the structure has been constructed as designed and as approved in the reclamation plan in the permit.
(i) When a siltation structure is removed, you must regrade the land upon which the structure was located and revegetate the land in accordance with the reclamation plan and §§ 817.111 and 817.116 of this chapter.
(ii) Paragraph (b)(5)(i) of this section does not apply to sedimentation ponds approved by the regulatory authority for retention as permanent impoundments under § 817.49(b) of this part if the maintenance requirements of § 800.42(c)(5) of this chapter are met.
(1) When used, sedimentation ponds must -
(i) Be located as near as possible to the disturbed area and outside perennial or intermittent stream channels unless approved by the regulatory authority in the permit in accordance with §§ 784.28 and 817.57(c) of this chapter.
(ii) Be designed, constructed, and maintained to -
(A) Provide adequate sediment storage volume.
(B) Provide adequate detention time to allow the effluent from the ponds to meet applicable effluent limitations.
(C) Contain or treat the 10-year, 24-hour precipitation event (“design event”) unless a lesser design event is approved by the regulatory authority based on terrain, climate, other site-specific conditions, and a demonstration that the effluent limitations referenced in § 817.42 of this part will be met.
(D) Provide a nonclogging dewatering device adequate to maintain the detention time required under paragraph (c)(1)(ii)(B) of this section.
(E) Minimize short circuiting to the extent possible.
(F) Provide periodic sediment removal sufficient to maintain adequate volume for the design event.
(G) Ensure against excessive settlement.
(H) Be free of sod, large roots, frozen soil, and acid-forming or toxic-forming materials.
(I) Be compacted properly.
(d)Other treatment facilities.
(1) You must design other treatment facilities to treat the 10-year, 24-hour precipitation event unless the regulatory authority approves a lesser design event based upon terrain, climate, other site-specific conditions, and a demonstration that the effluent limitations referenced in § 817.42 of this part will be met.
(e)Exemptions. The regulatory authority may grant an exemption from the requirements of this section if -
(1) The disturbed drainage area within the total disturbed area is small; and