Sec. 9.5.2. Falls Watershed Protection Overlay District (-FWPOD)

For all lots or portions of lots in existence prior to March 1, 1988 or lots established outside the subdivision process after that date, no additional impervious surface may be added to the property which would result in greater coverage by impervious surface than is allowed by the following table:

1. Within any secondary watershed protection area, lots which are connected to both City water and sewer utilities and have a total maximum impervious surface of more than 3,500 square feet may have an impervious coverage of more than 12% and less than 24%; provided that the first ½ inch of stormwater which directly or indirectly runs off the surfaces in excess of 12%, from the lot is:
   1. Retained for water harvesting and use on the site, infiltration into the soil, evaporation into the air, or a combination of these;
   2. Detained for at least a 12-hour period;
   3. Captured by an approved stormwater treatment device; or
   4. A combination of the above.
2. Impervious surface coverage of 24% or higher is allowed in secondary reservoir watershed protection areas when the first inch of rainfall (including the amount from the first 24% impervious surface coverage) is captured by an approved stormwater treatment device. Such runoff must be managed in accordance with Sec.9.5.2.C.3 below.

1. Where impervious surface coverage is equal to or less than 12% in any primary water supply watershed protection area or equal to or less than 24% in any secondary water supply watershed protection area, the first ½ inch of stormwater which runs off any street must be contained within the development capture methods set forth in Sec. 9.5.2.C.1. above.
2. Where impervious surface coverage is greater than 12% in any primary water supply watershed protection area or greater than 24% in any secondary water supply watershed protection area, the first inch of rainfall from streets must be managed in accordance with Sec. 9.5.2.C.3. below.

1. When impervious surface exceeds 24% in secondary reservoir watershed protection areas, runoff from the entire development site must be controlled on a runoff volume basis such that the post-development volume of stormwater leaving the site is equal to or less than the predevelopment volume of stormwater leaving the site based on the 90th percentile storm. For the purpose of meeting this requirement for new development sites, the pre-development land cover must be assumed to be forested for the entire development site. The developer may request, and the City may approve, a design exception to this requirement based on one or more of the following criteria:
   1. Low infiltration rates of native soils on the site.
   2. Shallow depth to seasonally high groundwater table on the site.
   3. Shallow depth to bedrock on the site.
   4. Other hardship approved by the Engineering Services Director based on site conditions. In requesting a design exception to this requirement, the developer must demonstrate that runoff resulting from the first inch of rainfall over the entire development site will be detained or retained using conventional stormwater treatment practices, GSI practices, or a combination.
2. Except where located in areas designated in the Comprehensive Plan for higher impervious surfaces, the maximum percent of impervious surface coverage in those portions of the secondary reservoir watershed 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%.
3. 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.
4. The design of wet ponds must meet the specifications and requirements found within the Stormwater Management Design Manual.

1. Applicability
   1. The following regulations apply to new development and expansions to impervious surfaces occurring on or after June 1, 2011.
   2. 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.
   3. 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.
   4. All stormwater management plans required for new development on properties located within a -FWPOD must comply with the following regulations.
2. Requirement
   1. Nitrogen and phosphorous loads contributed by the proposed new development activity may not exceed the unit-area mass loading rates as follows:
      1. Nitrogen: 2 2/10 pounds per acre per year; and
      2. Phosphorus: 33/100 of a pound per acre per year.
   2. The developer’s stormwater management plan must determine the load reductions necessary to comply with the above maximums by using the accounting tool approved by the State of North Carolina.
   3. 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:
      1. a) The installation within the development of all stormwater control measures shown on the watershed stormwater control master plan;
      2. b) The payment of fees in lieu of installation, when allowed by the State; and
      3. c) The payment of any applicable drainage fees if the facilities prescribed by the master plan are constructed.
3. Option for Offsetting a Portion of Nutrient Loading
   1. The developer shall have the option of offsetting a portion of the nitrogen and phosphorous load by implementing or funding offsite 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.
   2. Offsetting measures provided off-site by the developer must achieve at least equivalent reductions in nitrogen and phosphorus loading as needed on-site to comply with the maximum loading rates specified above. Offsetting measures provided off-site must meet the requirements of State Administrative Rule 15A NCAC 02B .0282, which may include the following:
      1. Payments to the North Carolina Department of Environmental Quality Division of 
         Mitigation Services Nutrient Offset Program contingent upon acceptance of payments by that program;
      2. A City approved offset program prescribed in the Raleigh Stormwater Design Manual; or
      3. An offset program proposed by the property owner which is located within the applicable reservoir watershed protection area basin subject to final approval by the  Engineering Services Director.