Sec. 26.20.21.06. Siltation Structures

A. Exemptions. Exemptions to the requirements of this regulation may be granted if the:

(1) Disturbed drainage area within the total disturbed area is small; and

(2) Operator demonstrates that siltation structures and alternate sediment control measures are not necessary to meet the effluent limitations in this chapter and the applicable State and federal water quality standards for receiving waters.

B. In this regulation, the following terms have the meanings indicated.

C. Terms Defined.

(1) Disturbed Area.

(a) "Disturbed area" means an area from which vegetation, topsoil, or overburden is removed or land occupied by topsoil stockpiles, spoil piles, the open pit, access or haul roads, haulageways, storage areas, shop areas, processing and shipping areas, drainage or sediment control structures, coal processing wastes, underground development waste, or non-coal waste.

(b) "Disturbed area" does not include those areas where the:

(i) Only surface mining activities include diversion ditches, siltation structures, or roads that are designed, constructed, and maintained in accordance with COMAR 26.20.19; and

(ii) Upstream area is not otherwise disturbed by the operator.

(2) "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.

(3) "Siltation structure" means a sedimentation pond, a series of sedimentation ponds, or other treatment facility.

D. General Requirements for Siltation Structures. All siltation structures:

(1) Shall prevent additional contributions of suspended solids sediment to streamflow or runoff outside the permit area to the extent possible using the best technology currently available;

(2) Shall collect all surface drainage from the disturbed area before leaving the permit area, except as provided in §A of this regulation;

(3) Shall be constructed before beginning a surface mining activity in an area and, upon construction, be certified by a qualified professional engineer as being constructed in accordance with the approved design;

(4) Shall be designed, constructed, and maintained in accordance with Regulation .08 of this chapter if the structure impounds water;

(5) Shall be maintained until:

(a) Removal is authorized by the Department;

(b) The disturbed area has been stabilized and revegetated;

(c) The quality of the untreated drainage from the disturbed area meets applicable State and federal water quality standards for the receiving stream; and

(6) May not be removed if augmented seeding has occurred within the last 2 years.

E. When a siltation structure is removed, the land on which the structure was located shall be regraded and revegetated in accordance with the approved reclamation plan.

F. The design, construction, and maintenance of a siltation structure does not relieve the person from compliance with applicable effluent limitations.

G. Sedimentation Ponds. Sedimentation ponds shall be used individually or in series and shall be:

(1) Designed, constructed, and maintained in accordance with Regulation .08 of this chapter;

(2) Located as near as possible to the disturbed area and out of perennial streams, unless approved by the Bureau; and

(3) Designed, constructed, and maintained to:

(a) Provide a minimum sediment storage volume of 67 cubic yards per acre of drainage area to the pond;

(b) Provide adequate detention time to allow the effluent from the ponds to meet State and federal effluent limitations;

(c) Contain or treat the 10-year, 24-hour precipitation event so there is no outflow through the emergency spillway unless a lesser design event is approved by the Bureau based on terrain, climate, other site conditions, and on a demonstration by the operator that the effluent limits of Regulation .02 of this chapter will be met;

(d) Provide a nonclogging dewatering device adequate to maintain the detention time;

(e) Minimize, to the extent possible, short circuiting; and

(f) Provide for the removal of sediment when the volume of sediment accumulates to 60 percent of the sediment storage volume.

H. The dewatering device required by §G(3)(d) of this regulation may not be located at an elevation lower than the maximum elevation of the sediment storage volume, unless approval is obtained from the Bureau.

I. Other Treatment Facilities. Other treatment facilities shall be designed:

(1) In accordance with the applicable requirements of this section; and

(2) To contain or treat the 10-year, 24-hour precipitation event unless a lesser design event is approved by the Bureau in accordance with §G(3)(c) of this regulation.