Unified Development Ordinance, 30th Supplement, November 2023

CHAPTER 9. ​NATURAL RESOURCE PROTECTION | Article 9.2. ​Stormwater Management

D. Diffuse Stormwater Flow Required 1. All stormwater runoff from new man-made stormwater control facilities, including new ditches or canals, which flow into a watercourse natural resource buffer or into riparian surface water buffer shall be diffused flow so as not to concentrate stormwater or form gullies. 2. Diffuse flow shall be maintained. 3. The landowner or person in possession or control of the land shall be responsible for dispersing concentrated flow of stormwater runoff. 4. The landowner shall take corrective action to prevent the formation of erosion gullies and the landowner shall take corrective action to restore diffuse flow. 5. When diffuse flow is impractical to achieve, stormwater control facilities that attenuate the flow of stormwater runoff and control nitrogen may be approved by the City as an alternative means of compliance. E. Watercourse Buffer Permits 1. No development, expansion of development or change in use may occur on a lot containing a natural resource buffer or open space area required as part of an approved stormwater control plan, without first being issued a written watercourse buffer permit from the City. 2. The City may not issue a watercourse buffer permit until the boundaries of any required natural resource buffer, riparian surface water buffer or permanently protected undisturbed open space areas that are adjacent to or encompass a work site are demarcated by a protective fence in the field. 3. No watercourse buffer permit may be issued for work in a riparian surface water buffer regulated by the State pursuant to Title 15A of the North Carolina Administrative Code Subarticle 2B, Section .0233 unless: a. The North Carolina Division of Water Quality has determined that surface waters are not present; b. The applicant provides sufficient documentation to demonstrate that the requested work is exempt under the rule; c. The North Carolina Division of Water Quality has determined that the requested work is allowable with mitigation under the rule; or

2. Regulations Applying to Both Primary and Secondary Buffer Areas a. Stormwater Control Facilities in Primary or Secondary Areas Stormwater control facilities may be allowed within a primary or secondary area only if the following requirements are met: i. The constructed uses within the buffer area require the use of such facilities; ii. The provisions of Sec. 9.4.4.G.4. require facilities in the buffer area; iii. A wet pond is required by Sec. 9.5.1. , Sec. 9.5.2. or Sec. 9.5.3. ; or iv. A lake or wet pond is created or preserved. b. Stormwater Control Facilities in Required Buffers Stormwater control facilities may be allowed within required buffer areas only if the following requirements are met. i. The velocity of the stormwater shall not exceed a non-erodible velocity, according to Sec. 9.4.4.G.3. , beyond the outlet of the storm control facilities. ii. Trees over 2-inch DBH which: a) Would be destroyed by installation of storm control facilities, but not including lakes or wet ponds; b) Lie within the greater distance of either a 7-foot radius or 1 foot in diameter for each inch of circumference of the tree measured from the outer edge of the grading limits of a storm drainage project shall be replaced by 1 new tree planted in the same general location, all to achieve the same effect as shown on an approved site plan. The planting must be a minimum caliper of 2 inches and be at least 8 feet tall at time of planting; and c) This provision shall not require trees to be planted on cleared land forming the basin of a wet pond or lake. iii. Stormwater control facilities, which are permitted in the primary and secondary buffer area, shall comply with Sec. 9.5.1.C. , Sec. 9.5.2.C. or Sec. 9.5.3.C.

Supp. No. 30

9 – 26 Published November 2023

Part 10: Unified Development Ordinance City of Raleigh, North Carolina