(1) The stormwater administrator shall use the policy, criteria, and information, including technical specifications and standards, in the latest published edition or revision of the North Carolina Department of the Environment and Natural Resources-Division of Water Quality's Manual of Stormwater Best Management Practices (referred to herein as the stormwater BMP design manual). The BMP Stormwater BMP design manual will serve as the basis for decisions about stormwater permits and about the design, implementation and performance of structural and non-structural stormwater BMPs.
Low-density projects (no more than two dwelling units per acre or 24 percent built-upon area for all residential and non-residential development) shall comply with each of the following standards:
(1) Stormwater conveyance. Stormwater runoff from the development shall be transported from the development by vegetated conveyances to the maximum extent practicable.
(2) Stream buffers. All built-upon area shall be at a minimum of 30 feet landward of all perennial and intermittent surface waters. A perennial or intermittent surface water shall be deemed present if the feature is approximately shown on either the most recent version of the soil survey map prepared by the Natural Resources Conservation Service of the United States Department of Agriculture (USDA) or the most recent version of the 1:24,000 scale (7.5 minute) quadrangle topographic maps prepared by the United States Geologic Survey (USGS). An exception to this requirement may be allowed when surface waters are not present in accordance with the provisions of 15A NCAC 2B .0233 (3)(a) or similar site-specific determination made using Division-approved methodology.
(3) Density provision A project with an overall density at or below the low-density thresholds, but containing areas with a density greater than the overall project density, may be considered low density as long as the project meets or exceeds the post-construction model practices for low-density projects and locates the higher density in upland areas and away from surface waters and drainageways to the maximum extent practicable.
(4) Restrictions on property use. The approval of the stormwater permit shall require an enforceable restriction on property usage that runs with the land, such as recorded deed restrictions or protective covenants, to ensure that future development and redevelopment maintains the site consistent with the approved project plans.
High-density projects (any project that exceeds the low density thresholds for dwelling units per acre or built-upon area) shall implement structural stormwater management systems that comply with each of the following standards:
(1) Treatment volume. The measures shall be designed to control and treat the stormwater run-off generated by the one-inch of rain;
(2) Drawdown time. Runoff volume drawdown time shall be a minimum of 48 hours, but not more than 120 hours;
(3) Post-development flows. Stormwater shall not leave the project site at a rate greater than the predevelopment discharge rate for the ten-year, 24-hour storm;
(4) Total suspended solids removal. All structural stormwater treatment systems used to meet the requirements of the program shall be designed to have a minimum of 85 percent average annual removal for total suspended solids (TSS);
(5) General design criteria. General engineering design criteria for all projects shall be in accordance with 15A NCAC 2H .1008(c), as explained in the design manual;
All stormwater control measures that incorporate a permanent or temporary water pool with depth greater than two feet shall be fenced. The fence shall meet the design standards maintained by the stormwater administrator.
(6) Stream buffers. All built-upon area shall be at a minimum of 30 feet landward of all perennial and intermittent surface waters. A surface water shall be deemed present if the feature is approximately shown on either the most recent version of the soil survey map prepared by the Natural Resources Conservation Service of the United States Department of Agriculture (USDA) or the most recent version of the 1:24,000 scale (7.5 minute) quadrangle topographic maps prepared by the United States Geologic Survey (USGS). An exception to this requirement may be allowed when surface waters are not present in accordance with the provisions of 15A NCAC 2B .0233 (3)(a) or similar site-specific determination made using Division-approved methodology.
(7) Restrictions on property use. The approval of the stormwater permit shall require an enforceable restriction on property usage that runs with the land, such as recorded deed restrictions or protective covenants, to ensure that future development and redevelopment maintains the site consistent with the approved project plans.
(a) Function of BMPs as intended. The owner of each structural BMP installed pursuant to this article shall maintain and operate it so as to preserve and continue its function in controlling stormwater quality and quality at the degree or amount of function for which the structural BMP was designed.
(b) Annual maintenance inspection and report. The person responsible for maintenance of any structural BMP installed pursuant to this article shall submit to the stormwater administrator an annual inspection report from one of the following persons performing services only in their area of competence: a qualified registered North Carolina professional engineer, surveyor, or landscape architect, soil scientist, aquatic biologist, or person certified by the North Carolina Cooperative Extension Service for stormwater treatment practice inspection and maintenance. The inspection report shall contain all of the following:
(1) The name and address or the land owner;
(2) The recorded book and page number of the lot of each structural BMP;
(3) A statement that an inspection was made of all structural BMPs;
(4) The date the inspection was made;
(5) A statement that all inspected structural BMPs are performing properly and are in compliance with the terms and conditions of the approved maintenance agreement required by this article; and
(6) The original signature and seal of the engineer, surveyor, or landscape architect.
All inspection reports shall be on forms supplied by the stormwater administrator. An original inspection report shall be provided to the stormwater administrator beginning one year from the date of as-built certification and each year thereafter on or before the date of the as-built certification.
City of Mebane Stormwater Website
Piedmont Triad Regional Council- Stormwater SMART