<div class="chunk-title">Sec. 30-119. - Structure design.</div>
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            <p class="incr0">
               (a)
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            <p class="content1">
               All stormwater control structures shall be designed by a state registered professional
               with qualifications appropriate for the type of system required. These registered
               professionals are defined as professional engineers, landscape architect, to the extent
               that the G.S. ch. 89A allows, land surveyors, to the extent that the design represents
               incidental drainage within a subdivision, as provided in G.S. ch. 89(C)-3(7).
               </p>
            		
            <p class="incr0">
               (b)
               </p>
            		
            <p class="content1">
               All stormwater controls shall use wet detention as a primary treatment system unless
               alternative stormwater management measures, as outlined in subsection (c) of this
               section are used. Wet detention ponds shall be designed for specific pollutant removal
               to modeling techniques approved by the state division of water quality. Specific requirements
               for these systems shall be in accordance with the following design criteria:
               </p>
            		
            <p class="incr1">
               (1)
               </p>
            		
            <p class="content2">
               Wet detention ponds shall be designed to remove 85 percent of total suspended solids
               in the permanent pool and storage runoff from a one-inch rainfall from the site above
               the permanent pool;
               </p>
            		
            <p class="incr1">
               (2)
               </p>
            		
            <p class="content2">
               The designed runoff storage volume shall be above the permanent pool;
               </p>
            		
            <p class="incr1">
               (3)
               </p>
            		
            <p class="content2">
               The discharge rate from these systems, following the one-inch rainfall design storm
               shall be such that the runoff does not draw down to the permanent pool level in less
               than two days, and that the pond is drawn down to the permanent pool level within
               at least five days;
               </p>
            		
            <p class="incr1">
               (4)
               </p>
            		
            <p class="content2">
               The mean permanent pool depth shall be a minimum of three feet;
               </p>
            		
            <p class="incr1">
               (5)
               </p>
            		
            <p class="content2">
               The inlet structure shall be designed to minimize turbulence using baffles or other
               appropriate design features;
               </p>
            		
            <p class="incr1">
               (6)
               </p>
            		
            <p class="content2">
               Vegetative filters shall be constructed for the overflow and discharge of all stormwater
               wet detention ponds and shall be at least 30 feet in length. The slope and width of
               the vegetative filter shall be determined so as to provide a nonerosive velocity of
               flow through the filter for a ten-year, 24-hour storm with a ten-year one-hour intensity
               with a slope of five percent or less. Vegetation in the filter shall be natural vegetation,
               grasses or artificially planted wetland vegetation appropriate for the site characteristics.
               </p>
            		
            <p class="incr0">
               (c)
               </p>
            		
            <p class="content1">
               Alternative stormwater management systems, consisting of one treatment option or a
               combination of treatment options, may be used. The design criteria for approval shall
               be 85 percent average annual removal of total suspended solids. Also, the discharge
               rate shall meet one of the following criteria:
               </p>
            		
            <p class="incr1">
               (1)
               </p>
            		
            <p class="content2">
               The discharge rate, following the one-inch design storm shall be such that the runoff
               draws down to the prestorm design within five days, but not less than two days; or
               </p>
            		
            <p class="incr1">
               (2)
               </p>
            		
            <p class="content2">
               The post development peak discharge rate shall equal the predevelopment rate for the
               one year, 24-hour storm.
               </p>
            		
            <p class="incr0">
               (d)
               </p>
            		
            <p class="content1">
               In addition to the vegetative filters required in subsection (b)(6) of this section,
               all land areas outside of the pond shall be provided with a ground cover sufficient
               to restrain erosion within 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 <a href="" data-chunk-id="COOR_CH30EN_ARTIIWAPR_DIV4STCO_S30-120POFISERE" class="section-link" data-product-id="13953">section 30-120</a>(c).
               </p>
            		
            <p class="incr0">
               (e)
               </p>
            		
            <p class="content1">
               A description of the area containing the stormwater control structure shall be prepared
               and filed consistent with <a href="" data-chunk-id="COOR_CH30EN_ARTIIWAPR_DIV4STCO_S30-123INREPEBO" class="section-link" data-product-id="13953">section 30-123</a>(a) and (b), as a separate plat, with the county register of deeds along with any
               easements necessary for general access to the stormwater control structure. The plat
               shall include the stormwater control structure, vegetative filters, all pipes and
               water control structures, berms, dikes, etc., and sufficient area to perform inspections,
               maintenance, repairs and reconstruction.
               </p>
            		
            <p class="incr0">
               (f)
               </p>
            		
            <p class="content1">
               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.
               </p>
            		
            <p class="historynote0">
               (Ord. of 8-21-2001, Â§ 501)
               </p></div>