20052146 Ver 5_Staff Comments_20090923

I propose we add the following condition to the SeaWatch 401 Certification and the
Conservation Easement Deed in order to protect the uses of this wetland and allow the
discharge of stormwater to the wetland:
Stormwater runoff from impervious surfaces within drainage areas that will drain to the two
Carolina Bay's (Easement Areas 32, 35, 54, 56 and 57) must be collected and treated in
engineered Stormwater treatment systems designed to reduce the nutrient load. These stormwater
treatment systems must control and treat the runoff from all surfaces generated by one and one-
half inches of rainfall or the difference in the stormwater runoff from all surfaces from the
predevelopment and postdevelopment conditions from a one- year, 24-hour storm, whichever is
greater. All inflow into the wetland must be at non-erosive velocities. In addition, these
stormwater treatment systems must be constructed, operated and maintained as provided in the
most recent version of DWQ's stormwater BMP manual. Monitoring must be done on this
wetland at two locations for 10 (ten) years following development activities in the drainage area
to the wetland. These two locations must be approved by DWQ and be in the northern and
southern part of the bay. This monitoring must be done on an annual (A) or semi-annual (SA)
basis for the following parameters: vegetation (every five years with annual reporting on the
percent cover of trees and shrubs within the permanent study plots), amphibians (A), aquatic
macrobenthos (every other year), water chemistry (SA) when water is present and hydrology
(reported SA with a well that records at daily intervals). This sampling must mirror the sampling
done by DWQ for the past three years in order to allow a comparison of the hydrological,
chemical and biological effects of the stormwater. All water chemistry analyses and
macrobenthos identification must be done by North Carolina certified laboratories. Written
DWQ approval is needed for an exact monitoring plan before development occurs within the
drainage area. Monitoring will begin when construction of the first house begins in the drainage
area and continue for ten (10) years. After five (5) years, the applicant may petition DWQ for a
reduction in the frequency of monitoring based on the data collected to date. Annual, written
reports must be provided to DWQ by March 31" of each year to the Division's Central and
Wilmington Regional Offices. These reports must summarize all the date collected to date and
compare these data to the baseline data collected by DWQ. These reports must also report the
approximate percent impervious surfaces in the drainage area and have a narrative discussion of
any changes to the development site plan in the drainage area. Data from the monitoring will be
compared to the baseline data that DWQ has collected in order to determine whether any adverse
impacts are occurring or have occurred. Please note that the development will not be held
responsible for any adverse impacts on the wetland as long as all other conditions of this
Certification are complied with including the provision for design, construction, operation and
maintenance of the stormwater treatment systems as noted above in this condition.
It- ?. E C9C?[?! 0WL4
S E P 2 3 2009
DENR - WATER QUALITY
WETLANDS AND STORMWATER BRANCH
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