HomeMy WebLinkAboutC.054.93011_0872 (2)B. All stormwater controls s"etares shall use wet detention pends as thea primary treatment system
unless alternative stormwater manaeement measures, as outlined in Section 703(C), 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 in accordance with followin deli n criteria:
1. Wet detention ponds shall be designed to remove a minifaum of eight 85% of total suspended
solids in the permanent pool and storage runoff from a one inch rune€£ rainfall from the site above
the permanent pool;
2. The designed runoff 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 runoff 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;
& 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 so as to provide a non-erosive velocity of flow-through the filter for a 10 -year, 24-hour
storm with a 10 -year, 1 -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;
The ...-..,......,. andye
getative filtef shall be designed te nuiiimwe veeter amaetion. Vegetative fi4eFs
if designed to FeFmin wet undeF BOMA! GORditions should have adequaie dFy weathef flew $a feduee
Fautin. maitttenaxse-
C. 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
averaee annual removal of Total Suspended Solids. Also, the discharge rate shall meet one of the
following criteria;
1. the discharge rate following the 1 -inch design storm shall be such that the
runoff draws down to the ore -storm design staee within five days, but not less that two days; or
2. the post development peak discharge rate shall equal the predevelopment rate
for the 1 -year, 24-hour storm.
D. In addition to the vegetative filters required in Section 703 (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 507(g)705(C)-41P-4h``
012dieanee.
E. A description of the area containing the stormwater control structure shall be prepared and filed in consistency
with Section 307(41)(1 707 (A and B), as a separate deed with the Iredell County Register of Deeds along
with any easements necessary for general access to the stormwater control structure should em-neFship (and
. The deeded
area shall include the detention pperA stormwater control structure, vegetative filters, all pipes and water
control structures, berms, dikes, etc., and sufficient area to perform inspections, maintenance, repairs, and
reconstruction.
F. The pen,ieus peFtions of any 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
built -upon area for any other site or area.
Section 704. Posting of Financial Security Required
A. All new stormwater control structures shall
be conditioned on the posting of adequate financial assurance for the purpose of eonswaetior-,—maintenance,
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