La. Admin. Code tit. 43 § XV-5327

Current through Register Vol. 50, No. 9, September 20, 2024

Section XV-5327 - Hydrologic Balance: Siltation Structures

A. Definitions. For the purposes of this Section only:

Disturbed Area- shall not include those areas:

a. in which the only surface mining activities include diversion ditches, siltation structures or roads that are designed, constructed and maintained in accordance with this Chapter; and

b. for which the upstream area is not otherwise disturbed by the operator.

Other Treatment Facilities- 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 contributions of suspended solids to streamflow or runoff outside the permit area.

Siltation Structure- a sedimentation pond, a series of sedimentation ponds or other treatment facility.

B. General Requirements

1. 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.

2. 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.

3. Any siltation structure which impounds water shall be designed, constructed, and maintained in accordance with §5333

4. Siltation structures shall be maintained until removal is authorized by the office and the disturbed area has been stabilized and revegetated. In no case shall the structure be removed sooner than two years after the last augmented seeding.

5. When a 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 §5417-5423 Sedimentation ponds approved by the office for retention as permanent impoundments may be exempted from this requirement.

C. Sedimentation Ponds

1. When used, sedimentation ponds shall:

a. be used individually or in series;

b. be located as near as possible to the disturbed area and out of perennial streams unless approved by the office; and

c. 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 office based on terrain, climate, other site-specific conditions, and on a demonstration by the operator that the effluent limitations of §5321 will be met;

iv. provide a nonclogging dewatering device adequate to maintain the detention time required under §5327. C.1.c 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.

2.

a. Sedimentation ponds meeting the size or other qualifying criteria of 30 CFR 77.216(a) shall comply with all the requirements of that Section, and shall have principal and emergency spillways that in combination will safely pass a 100-year, 6-hour precipitation event.

b. Sedimentation ponds not meeting the size or other qualifying criteria of 30 CFR 77.216(a) shall provide a combination of principal and emergency spillways that will safely discharge a 25-year, 6-hour precipitation event. Such ponds may use a single spillway if the spillway:

i. is an open channel of nonerodible construction and capable of maintaining sustained flows; and

ii. is not earth-lined.

D. Other Treatment Facilities

1. Other treatment facilities shall be designed to treat the 10-year, 24-hour precipitation event unless a lesser design event is approved by the office based on terrain, climate, other site-specific conditions, and a demonstration by the operator that the effluent limitations of §5321 will be met.

2. Other treatment facilities shall be designed in accordance with the applicable requirements of §5327 C

E. Exemptions. Exemptions to the requirements of this Section may be granted if:

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 §5321 and the applicable state and federal water quality standards for the receiving waters.

La. Admin. Code tit. 43, § XV-5327

Promulgated by the Department of Natural Resources, Office of Conservation, LR 14:441 (July 1988), amended LR 20:447 (April 1994).

AUTHORITY NOTE: Promulgated in accordance with R.S. 30:901-932.