High-density projects shall implement stormwater control measures that comply with each of the following standards:
(A) Volume runoff control. All new development is required to control volume discharge from the site. All structural stormwater treatment systems used to meet this requirement shall control and treat runoff from the first one inch of rainfall. Runoff volume drawdown time shall be a minimum of 48 hours, but not more than 120 hours.
(B) Peak runoff control.
(1) All new development is required to control peak discharge rate from the site. All structural stormwater treatment systems used to meet this requirement shall control and treat runoff for the 1-year, 24-hour storm to predevelopment levels to avoid contributing to erosion to the stream channel.
(2) Peak flow control is not required for developments that meet one or more of the following requirements:
(a) The increase in peak flow between pre- and post-development does not exceed 10%, or
(b) The proposed new development meets all of the following criteria overall impervious surface is less than 15% and the remaining pervious portions of the site are utilized to the maximum extent practical to convey and control the stormwater runoff, or
(c) Greene County may exempt development in specific locations if such locations are prone to flooding and controlling peak flow will aggravate the flooding problems.
(C) Total suspended solids (TSS) removal. All structural stormwater treatment systems used to meet the requirements of this program shall be designed to have a minimum of 85% average annual removal for total suspended solids (TSS).
(D) General engineering design criteria. General engineering design criteria for all projects shall be in accordance with 15A NACA 2H .1008(c), as explained in the Design Manual.
(E) Minimum separation from perennial and intermittent surface waters. 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.
(F) Restrictions on property. 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.
(Ord. passed 6-29-16)