Unified Development Ordinance, 4th supplement, September 2017

Part 10A: Unified Development Ordinance City of Raleigh, North Carolina 9 – 36 Effective Date: September 01, 2013 Supp. No. 4 x. White Store clay loam, 2 to 15% slopes (WvD3); y. Wilkes, 10% to 20% slopes (WwE); z. Wilkes, 20% to 45% slopes (WwF); and aa. Wilkes, 15% to 25% slopes (WxE). 5. Armored Armored or otherwise non-vegetatively lined watercourse lining shall, in addition to the requirements of Sec. 9.4.4.G.3. above, be provided at the storm outlet and for those portions of the receiving watercourse which have undergone land-disturbing activity. 6. Exception Where piped, paved or armored storm drainage facilities connect to existing off-site piped, paved or armored storm drainage facilities or where it can be demonstrated that stormwater discharge velocities will not create an erosion problem in the receiving watercourse, none of the foregoing provisions of this section shall apply. 7. Equivalent Alternatives The management of stormwater runoff to minimize or control downstream channel and bank erosion is a developing technology. Innovative techniques and ideas will be considered and may be used when shown to have the potential to produce successful results. Alternatives include, but are not limited to: a. Avoid increases in surface runoff volume and velocity by including measures to promote infiltration to compensate for increased runoff from areas rendered impervious; b. Avoid increases in stormwater discharge velocities by using vegetated or roughened swales and waterways in lieu of closed drains and high velocity paved sections; c. Provide energy dissipators at outlets of storm drainage facilities to reduce flow velocities to the discharge point. These may range from simple rip-rapped sections to complex structures; and d. Protect watercourses subject to accelerated erosion by improving cross- sections or providing erosion-resistant lining. H. Operations in Lakes or Natural Watercourses 1. Any land-disturbing activity in connection with construction in, on, over or under a lake or natural watercourse shall be planned and conducted in such a manner so as to minimize the extent and duration of disturbance of the stream channel and to prevent off-site sedimentation. 2. The relocation of a natural watercourse must meet the provisions of Sec. 9.4.4.G. and must minimize changes to the stream flow characteristics. The relocation of a natural watercourse may not occur in natural resource buffer yards of a -UWPOD, -FWPOD, -SWPOD, -MPOD or CM District. I. High-Quality-Water Zones Within high-quality-water (HQW) zones the following additional design standards shall apply. 1. Uncovered areas in HQW zones shall be limited at any time to a maximum total area within the boundaries of the tract of 20 acres. Only the portion of the land-disturbing activity within an HQW zone shall be governed by this section. Larger areas may be uncovered within the boundaries of the tract with the written approval of both the Director of the Division of Land Resources of the North Carolina Department of Environment, Health and Natural Resources and the City Council. 2. Sediment basins shall be designed and constructed such that the basin will have a settling efficiency of at least 85% for the 40 micron size soil particle transported into the basin by the runoff of that two-year storm which produces the maximum peak rate of runoff as calculated according to procedures required by this Articl e. 3. Newly constructed open channels in HQW zones shall be designed and constructed with side slopes no steeper than 2 horizontal to 1 vertical if vegetative cover is used for stabilization unless soil conditions permit a steeper slope or where the slopes are stabilized by using mechanical devices, structural devices or other acceptable ditch liners. In any event, the angle for side slopes shall be sufficient to restrain accelerated erosion. J. Keep Dirt and Mud Off Public Streets The accumulation of more than 1/32 inch of dirt, mud or both on any public street, measured 6 feet from an entrance or exit of any land-disturbing activity, is prohibited. CHAPTER 9. ​NATURAL RESOURCE PROTECTION | Article 9.4. Erosion & Sedimentation Control Sec. 9.4.5. Maintenance