(a) All stormwater control structures shall be designed by a North Carolina registered professional engineer.
(b) All stormwater controls shall use wet detention ponds as a primary treatment system unless alternative stormwater management measures, as outlined in Section 9-3163(g) are used. Wet detention ponds shall be designed for specific pollutant removal according to modeling techniques approved by the North Carolina Division of Environmental Management. Specific requirements for these systems shall be by the following design criteria:
(1) Wet detention ponds shall be designed to remove eighty-five percent (85%) of total suspended solids in the permanent pool and storage run-off from a one-inch rainfall from the site above the permanent pool;
(2) The designed run-off storage volume shall be above the permanent pool;
(3) The discharge rate from these systems following the one-inch rainfall design storm shall be such that the run-off does not draw down to the permanent pool level in less than two (2) days and that the pond is drawn down to the permanent pool level within at least five (5) days;
(4) The mean permanent pool depth shall be a minimum of three (3) feet;
(5) The inlet structure shall be designed to minimize turbulence using baffles or other appropriate design features;
(6) Vegetative filters shall be constructed for the overflow and discharge of all stormwater wet detention ponds and shall be at least thirty feet in length. The slope and width of the vegetative filter shall be determined to provide a non-erosive velocity of flow through the filter for a ten-year, twenty-four (24) hour storm with a ten-year, one-hour intensity with a slope of five percent (5%) or less. Vegetation in the filter shall be natural vegetation, grasses, or artificially planted wetland vegetation appropriate for the site characteristics; and
(7) All stormwater control structures shall be enclosed by a fence with a minimum height of six (6) feet.
(c) In addition to the vegetative filters required in Section 9-3163(b)(6), all land areas outside of the pond shall be provided with a ground cover sufficient to restrain erosion within thirty (30) days after any land disturbance. Upon completion of the stormwater control structure, a permanent ground cover shall be established and maintained as part of the maintenance agreement described in Section 9-3164(c).
(d) An easement in the property containing the stormwater control structure allowing the Town to perform inspections, maintenance, repairs, reconstruction, and any other acts which may be required for the Town to carry out the provisions of this Article, along with any easements necessary for general access to the stormwater control structure, shall be prepared consistent with Section 9-3167(a) and (b) and recorded in the office of the Register of Deeds of Burke County. The area in which this easement is granted shall include the detention pond, vegetative filters, all pipes and water control structures, berms, dikes, etc., and sufficient area to perform inspections, maintenance, repairs, and reconstruction.
(e) Qualifying areas of the stormwater control structure may be considered pervious when computing total built-upon area. However, if the structure is used to compute the percentage built-upon area for one site, it shall not be used to compute the built-upon area for any other site or area. (Ord. of 1/10/05; Ord. of 12/6/10; Ord. of 6/28/21)