The C-SWPPP must include a best management practices (BMP) section that accurately and descriptively addresses the use, installation, maintenance and inspection for each measure outlined in the stormwater management and sediment control section. This BMP section must be in accordance with SCDHEC’s NPDES-CGP. In addition, the plan must include the following:
(A) Development shall be fitted to the topography and soils to create the least erosion potential.
(B) Natural vegetation shall be retained and protected wherever possible.
(C) Natural vegetation and non-structural methods shall be employed, to the extent possible, for stream bank stabilization and erosion control wherever possible.
(D) Only the smallest practical area shall be exposed and then only for the shortest practical period of time. Effort should be made not to disturb more than 20 acres at any one time. If more than 20 acres are to be disturbed at any one time, the plan shall contain the following:
(1) The method of limiting the time of exposure and amount of exposed area to achieve the objectives of this chapter.
(2) A cut/fill analysis that shows where soil will be moved from one area of the tract to another as ground elevation is changed.
(3) Construction sequence and construction phasing to justify the time and amount of exposure.
(4) Techniques to be used to prevent sedimentation associated with larger disturbed areas.
(5) Additional erosion control measures, structures, and devices to prevent sedimentation.
(E) Waterway stabilization structures such as drop structures, grade stabilization structures, and channel liners shall be utilized to dissipate the energy of flowing water by holding the waterway slopes and velocities within non-erosive limits.
(F) For land disturbances of one acre and greater, all sediment control BMPs shall be designed and installed to meet a minimum sediment removal efficiency of 80% for total suspended solids (TSS) or greater or a 0.5 ml/l settleable solid effluent concentration using a ten-year, 24-hour design storm event, whichever is less.
(1) For construction sites located within three-quarters of a mile of Lake Wylie, Catawba River, Broad River, a drinking water supply source, or within 500 feet of a perennial stream as designated on the USGS map or as delineated by a professional wetlands consultant:
(a) All sediment control BMPs shall be designed to achieve a sediment removal efficiency of 85% or greater for total suspended solids (TSS).
(b) Use of additional erosion and sediment control treatment measures to enhance sediment removal efficiency, including the use of polymer flocculants, shall be required. Site specific soil sampling and analysis will be required to determine the reaction time and most effective polymer blend.
(G) Sediment basins and traps:
(1) The structure may be removed once stabilization is reached in the development of the area draining to that sediment basin or trap.
(2) A sediment basin or sediment trap may be required to be enclosed with temporary fencing in the event public safety is a concern. If fencing is to be provided, the type of fence and its location shall be shown in the C-SWPPP.
(3) Sediment basins and traps shall be designed to achieve a sediment removal efficiency of 80% or greater for total suspended solids (TSS) or meet a 0.5 ml/l settleable solids effluent standard using a 10-year, 24-hour design storm event, whichever is less.
(4) For construction sites located within 3/4 mile of Lake Wylie, Catawba River, Broad River, a drinking water supply source, or within 500 feet of a perennial stream, as designated on the USGS map or as delineated by a professional wetlands consultant, all sediment basins and traps shall be designed to provide storage for a calculated volume of runoff from the entire drainage area using, at a minimum, a 10-year, 24-hour storm event and designed to achieve a sediment removal efficiency of 85% or greater for total suspended solids (TSS). Sediment basins shall be designed to drain out over a period no less than 72 hours, using the calculated storage volume from the 10-year, 24-hour storm event.
(5) Sediment basins and traps must remain in place until 80% of the contributing drainage area is permanently stabilized.
(6) On-site stormwater retention structures (wet basins) shall not be utilized as a sediment basin during construction.
(H) Cut and fill slopes and other exposed areas shall be stabilized as soon as practical to limit the duration of the exposed soil.
(I) Description of spill prevention and response practices.
(J) Temporary erosion and sediment control measures shall be maintained continuously until permanent soil erosion control measures have reached final stabilization.
(K) Stockpiles shall be temporary and shall be leveled to conform to surrounding elevation as a precondition for any of the following, whichever occurs first:
(1) Request for a notice of termination; or
(2) Request for York County acceptance of a road or street in accordance with the road/street acceptance requirements of Chapter 154 - Land Development Code of this code.
(L) Stockpiles shall not be located within 50 feet of any water quality buffer zone.
(Ord. 2819, passed 6-17-19; Am. Ord. 3420, passed 10-5-20)