Secondary and Cumulative Impacts Master Management Plan - 2014

APPENDIX B – WAKE COUNTY PROGRAMS TO MITIGATE SECONDARY AND CUMULATIVE IMPACTS

The County created a Stormwater Management Section within its Environmental Services Department, whose goal is to minimize the impacts of stormwater runoff. The department staff is charged with upholding the local, state, and federal regulations related to stormwater, including:  Floodplain management  Sediment and erosion control  WSW protection  Neuse River Basin NSW stormwater rules  National Pollutant Discharge Elimination System (NPDES) Phase II Stormwater Regulations Stormwater management permits are also required. The County requires the use of the Wake County Stormwater Hybrid Design Tool for all stormwater management submittals. Its purpose is to streamline the many different stormwater requirements and facilitate a more timely review and approval of stormwater management plans. Complete stormwater requirements can be found in the 2014 Wake County Stormwater Manual: Submittal and Design Guidance. The purpose of this document is to provide guidance for the management of stormwater runoff resulting from development in the County’s jurisdiction. It provides support to Article 9 of the UDO and applicable State regulations, which establish minimum requirements to address impacts of stormwater runoff associated with new development and expansions. The County requires that the pre-development peak runoff rate be maintained. If the difference between pre- and post- runoff exceeds 10 percent for the 1-year, 24-hour storm then the developer must mitigate peak flow within the drainage area. Nitrogen export must not exceed of 3.6 pounds per acre per year (lbs/acre/year) in the Neuse River. The County additionally requires that residential post-development curve number not exceed target curve numbers. Article 9, Part 2 of the UDO requires volume management for target curve number matching. The County has established a stormwater credit system that provides incentives for better site design and the locating of new development in areas that cause less impact to aquatic resources. Approved methods to receive credit include: disconnected impervious surfaces, reforestation, and cluster and open space subdivisions. These stormwater practices reduce generation of stormwater, reduce size and cost of stormwater storage, and provide partial removal of pollutants. The County has impervious surface limitations in its WSWs. The impervious surface limitations range from 6 to 30 percent for residential areas, and up to 30 percent for non- residential areas. Under NPDES Phase II rules, development that exceeds 24 percent is required to implement stormwater best management practices (BMPs). Stormwater permits are required for non-residential projects that cumulatively disturb more than 0.5 acre. Wake County is required to implement the Neuse River and Jordan Lake NSW stormwater rules, as previously described, and stormwater program submittals are required for developments to ensure compliance with the rules. These rules supersede the Neuse Rules within the Jordan Lake watershed portion of the Cape Fear River Basin.

B-18