Unified Development Ordinance, 31st Supplement, May 2024

Article 9.5. Watershed Protection Areas | CHAPTER 9. ​NATURAL RESOURCE PROTECTION

b. Requirement i. Nitrogen and phosphorous loads contributed by the proposed new development activity may not exceed the unit-area mass loading rates as follows:

protection areas connected to both City water and sewer utilities shall not exceed 30% unless the impervious surface coverage is 3,500 square feet per lot or less; in such instances the maximum impervious surface coverage allowed shall not exceed 50%. c. When the development is located in portions of secondary reservoir watershed protection areas that are specifically designated in the Comprehensive Plan for higher impervious surfaces, the maximum impervious surface coverage may not exceed 70%; provided that the property is connected to both City water and sewer utilities. No more than 5% of the land area within any 1 secondary reservoir watershed protection area may be developed with an impervious surface coverage in excess of 50% unless approved by the North Carolina Environmental Management Commission. d. The design of wet ponds must meet the specifications and requirements found within the Stormwater Design Manual. D. Nitrogen and Phosphorous Loading 1. New Development a. Applicability i. The following regulations apply to new development and expansions to impervious surfaces occurring on or after June 1, 2011. ii. Substitutions of impervious surface done in accordance with Sec. 10.3.5.A. are allowed provided there is no net increase in impervious surface and equal or greater stormwater control is provided. iii. Lots and structures existing prior to June 1, 2011 are not to be considered nonconforming solely because of the application of these regulations. Additions and expansions to existing impervious surfaces, uses and structures must comply with the requirements of these regulations; however, impervious surfaces existing prior to the initial application of these regulations are not to be included in the nitrogen and phosphorous loading calculations. iv. All stormwater management plans required for new development on properties located within a -SWPOD must comply with the following regulations.

a) Nitrogen: 2 2/10 pounds per acre per year; and b) Phosphorus: 33/100 of a pound per acre per year.

ii. The developer’s stormwater management plan must determine the load reductions necessary to comply with the above maximums by utilizing the loading calculation method prescribed in the Stormwater Management Design Manual. iii. Developments that comply with the watershed stormwater control master plan approved for its watershed protection area are exempted from the requirements of this section. Compliance with watershed stormwater control master plan must include: a) The installation within the development of all stormwater control measures shown on the watershed stormwater control master plan; b) The payment of fees in lieu of installation, when allowed by the State; and c) The payment of any applicable drainage fees if the facilities prescribed by the master plan are constructed. c. Option for Offsetting a Portion of Nutrient Loading i. The developer shall have the option of offsetting a portion of the nitrogen and phosphorous load by implementing or funding off site management measures. Prior to utilizing any off-site option, the developer’s stormwater management plan must implement structural stormwater controls that attain a minimum of 60% reduction in increased post-construction nitrogen loading rate and a minimum of 60% in increased post-construction phosphorus loading rate on-site and, when applicable, implementing all engineered stormwater controls for compliance with National Pollutant Discharge Elimination System requirements and any other State mandated stormwater regulation.

Supp. No. 31

9 – 62 Published May 2024

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