Statutes, codes, and regulations
Wyoming Administrative Code
Agency 020 - Environmental Quality, Dept. ofSubagency 0011 - Water QualityChapter 11 - DESIGN AND CONSTRUCTION STANDARDS FOR SEWERAGE SYSTEMS, TREATMENT WORKS, DISPOSAL SYSTEMS OR OTHER FACILITIES CAPABLE OF CAUSING OR CONTRIBUTING TO POLLUTION AND MOBILE HOME PARK AND CAMPGROUND SEWERAGE AND PUBLIC WATER SUPPLY DISTRIBUTION SYSTEMS
Part C - COMMERCIAL/INDUSTRIAL WASTE AND WASTEWATER FACILITIES
Section 11-31 - Sedimentation Control Facilities

020-11 Wyo. Code R. § 11-31

Download
PDF
Current through April 27, 2019
Section 11-31 - Sedimentation Control Facilities

This section includes the standards for sedimentation control facilities. Those sedimentation control facilities that are regulated under Water Quality Rules and Regulations, Chapter 2, Appendix J, "Additional Requirements Applicable to Coal Mining Operations" are exempted from this section.

(a) Location. The sedimentation control facilities shall be as near to the affected lands as possible to keep construction and containment volumes to a minimum. Sedimentation control facilities shall be located off-channel when possible. Runoff from unaffected lands should be bypassed around the containment area. All affected lands must drain to a sedimentation control facility.

(b) Basis of design. Sedimentation control facilities shall control all runoff from areas that drain into the facility from a 10-year 24-hour precipitation event in addition to the estimated sediment storage volume for one (1) year be always available. The pond shall be drained down to the permanent pool level as soon as the effluent meets the discharge parameters. The applicant shall demonstrate that equipment or outlet structures are available for draining the pond.

(c) Layout.

  • (i) Inlet ditches or structures shall not erode or disturb the pond bottom.
  • (ii) Outlet structures, if used, shall have an overflow device, prevent short-circuiting, prevent floating debris from discharging and shall not erode or disturb the dike. All pipe protruding through a dike shall have adequate seepage control. The point of discharge into a channel shall be protected against erosion and erosion control devices shall be designed based on flow velocities.
  • (iii) Spillways. Sedimentation control facilities that individually contain more than 2.0 acre-feet of runoff or that individually have more than 2.0 acres of surface area or that are located on-channel shall have a spillway to by-pass precipitation events in excess of the design event. Spillways shall safely pass the 25-year flood event except when the impoundment height is greater than twenty feet or capacity exceeds twenty acre-feet; in which case the spillway shall safely pass the 100-year flood event.
  • (iv) By-pass ditches. If by-pass ditches are provided to transport runoff from unaffected lands, they shall be designed to pass the runoff from a 25-year precipitation event.
  • (v) Freeboard. Freeboard shall be provided to protect embankments and dikes from overtopping from wave action and shall be a minimum of one (1) foot above the high water level. For ponds less than two (2) acres, one-half (1/2) foot of freeboard may be acceptable.

(d) Construction.

  • (i) Soils used in constructing the pond bottom and dike cores shall be relatively incompressible, have a low permeability, and be free from organic material or trash. The soil shall be compacted at a water content that will insure structural stability, minimize hydraulic seepage, and minimize settling.

    Rocks larger than six (6) inches in length shall not be placed within five (5) feet of the interior slope surface of any pond embankment. Material containing by volume less than 25 percent of rock larger than six (6) inches and less than twelve (12) inch in length dimension may be placed in the remainder of the embankment.

  • (ii) Outer dike slopes shall not be steeper than one (1) vertical to two (2) horizontal. Flatter slopes may be required to maintain slope stability. Inner dike slopes shall be sloped between one (1) vertical to four (4) horizontal and one (1) vertical to three (3) horizontal.
  • (iii) The minimum top dike width shall be sufficient to provide structural stability.
  • (iv) Riprap or other acceptable erosion control shall be installed on the inner dike slopes at all anticipated levels of water. Dikes cut into existing ground shall be exempted from riprap requirements. Ponds that have less than 2.0 acres of surface area shall also be exempted.

020-11 Wyo. Code R. § 11-31

Amended, Eff. 6/29/2018.