§ 817.46 - Hydrologic balance: Siltation structures.

§ 817.46 What requirements apply to siltation structures?Hydrologic balance: Siltation structures.

(a) Scope. For the purpose purposes of this section only, the phrase “disturb the land surface” does disturbed areas shall not include those areas -

(1) In which the only underground surface mining activities conducted on the land surface consist of diversionsinclude diversion ditches, siltation structures, or roads that are designed, constructed , and maintained in accordance with this part; and

(2) For which you do not plan to otherwise disturb the land surface upgradient of the diversion, siltation structure, or roadthe upstream area is not otherwise distributed by the operator.

(b) General requirements.

(1) When siltation structures will be used to achieve the requirements of § 817.45 of this part, you must construct those structures Additional contributions of suspended solids and sediment to streamflow or runoff outside the permit area shall be prevented to the extent possible using the best technology currently available.

(2) All surface drainage from the disturbed area shall be passed through a siltation structure before leaving the permit area, except as provided in paragraph (b)(5) or (e) of this section. The requirements of this paragraph are suspended effective December 22, 1986, per court order.

(3) Siltation structures for an area shall be constructed before beginning any underground mining activities

that will disturb the land surface. (2) Upon completion of construction of a siltation structure, a

in that area, and upon construction shall be certified by a qualified registered professional engineer, or, in any

state that

State which authorizes land surveyors to prepare and certify plans in accordance with § 784.

25

16(a) of this chapter, a qualified registered professional land surveyor,

must certify that the structure has been

to be constructed as designed and as approved in the reclamation plan

in the permit

.

(

3

4) Any siltation structure

that

which impounds water

must

shall be designed, constructed and maintained in accordance with § 817.49 of this chapter.

(

4) You must maintain siltation structures

5) Siltation structures shall be maintained until removal is authorized by the regulatory authority and the disturbed area has been stabilized and revegetated.

(5)

(i) When a

In no case shall the structure be removed sooner than 2 years after the last augmented seeding.

(6) When the siltation structure is removed,

you must regrade

the land

upon

on which the siltation structure was located

and revegetate the land

shall be regraded and revegetated in accordance with the reclamation plan and §§ 817.111

and

through 817.116 of this chapter.

(ii) Paragraph (b)(5)(i) of this section does not apply to sedimentation

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

may be exempted from this requirement.

(7) Any point-source discharge of water from underground workings to surface waters which does not meet the effluent limitations of § 817.42 shall be passed through a siltation structure before leaving the permit area.

(c) Sedimentation ponds.

(1) When Sedimentation ponds, when used, sedimentation ponds must shall -

(i) Be used individually or in series;

(ii) Be located as near as possible to the

disturbed

distrubed area and

outside perennial or intermittent stream channels

out of perennial streams unless approved by the regulatory authority

in the permit in accordance with §§ 784.28 and 817.57(c) of this chapter.

(ii) ; and

(iii) 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

State and Federal 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 on a demonstration by the operator that the effluent limitations

referenced in

of § 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

iii)(B) of this section

.

;

(E) Minimize

short circuiting

, to the extent possible

.

, short circuiting;

(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.

coal-processing waste; and

(I) Be compacted properly.

(2) Spillways. A sedimentation pond must shall include either a combination of principal and emergency spillways or a single spillway configured as specified in § 817.49(a)(9) of this part.

(d) Other treatment facilities.

(1) You must design other Other treatment facilities shall be designed to treat the 10-year, 24-hour precipitation event even unless the regulatory authority approves a lesser design event based upon is approved by the regulatory authority based on terrain, climate, other site-specific conditions , and a demonstration by the operator that the effluent limitations referenced in of § 817.42 of this part will be met.

(2) You must design other Other treatment facilities shall be designed in accordance with the applicable requirements of paragraph (c) of this section.

(e) Exemptions. The regulatory authority may grant an exemption from 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) You demonstrate The operator demonstrates that neither siltation structures nor and alternate sediment control measures are not necessary for drainage from the disturbed drainage area to comply with areas to meet the effluent limitations under § 817.42 of this part. and the applicable State and Federal water quality standards for the receiving waters.

[48 FR 44051, Sept. 26, 1983, as amended at 53 FR 43607, Oct. 27, 1988; 59 FR 53030, Oct. 20, 1994; 73 FR 75884, Dec. 12, 2008; 75 FR 60275, Sept. 29, 2010; 79 FR 76232, Dec. 22, 2014; 81 FR 93418, Dec. 20, 2016; 82 FR 54999, Nov. 17, 2017]