Swift Creek Watershed Protection Overlay District (-SWPOD) Regulations
The Swift Creek Watershed Protection Overlay District (-SWPOD) is established by the City of Raleigh to protect Class WS-III drinking water sources by regulating land use and development intensity. This overlay district mandates that most lots provide an area set aside for trees equal to at least 40% of the lot area and adheres to strict impervious surface limitations, which can range from a base of 6% in primary protection areas to a maximum of 70% in specifically designated transit-oriented locations.
General Purpose and Applicability
The City of Raleigh applies the -SWPOD to protect the integrity of drinking water for the municipality and surrounding communities. The district is intended to ensure safe water for residents, businesses, industries, and wildlife at a reasonable cost. The -SWPOD is divided into two distinct zones: the primary reservoir watershed protection area and the secondary reservoir watershed protection area [Sec. 5.1.1.B.5].
Impervious Surface Coverage Standards
The City of Raleigh limits the amount of built-upon area (impervious surface) within the -SWPOD based on the location of the lot and the availability of public utilities. These standards apply to all lots in existence prior to March 1, 1988, or those established via the subdivision process after that date [Sec. 9.5.3.B.1].
-SWPOD Maximum Impervious Surface Limits
| Area Type | No Stormwater Control Measures | With Retention, Detention, or Capture (First 1/2" Runoff) | Management of First Inch of Rainfall |
|---|---|---|---|
| Primary Water Supply Protection Areas | 6% or 3,500 sq. ft. (if not > 12%) | N/A | N/A |
| Secondary Protection Areas (No City Water/Sewer) | 12% or 3,500 sq. ft. (if not > 24%) | N/A | N/A |
| Secondary Protection Areas (With City Water/Sewer) | 12% or 3,500 sq. ft. (if not > 24%) | 24% | 30% built area; or 3,500 sq. ft. (if not > 50%); or 70% in designated Comp Plan areas |
In the secondary reservoir watershed protection areas, the City of Raleigh may allow up to 70% impervious surface coverage if the property is connected to both City water and sewer and is located in an area specifically designated in the Comprehensive Plan for higher impervious surfaces [Sec. 9.5.3.C.3.c].
Natural Resource Buffer Yards
The City of Raleigh requires the establishment of natural resource buffer yards along primary and secondary watercourses within the -SWPOD to filter pollutants and manage stormwater flow [Sec. 9.5.3.A].
| Watercourse Type | Minimum Buffer Width (Each Side) |
|---|---|
| Primary: Draining 25+ acres | 60 feet |
| Primary: Draining 5 to 25 acres | 35 feet |
| Primary: Stream draining < 5 acres | 35 feet |
| Secondary: Areas in SFHA or with slopes 15%+ | Varies based on site |
If a property in a secondary reservoir watershed protection area exceeds 24% impervious coverage, the City of Raleigh requires a buffer of no less than 100 feet wide along each side of the watercourse [Sec. 9.5.3.C.1.b].
Forestation and Tree Conservation
Within the -SWPOD, the City of Raleigh requires that every lot provide and maintain an area set aside for trees equal to at least 40% of the total lot area [Sec. 9.5.3.G]. This requirement is subject to the following rules:
- At least 1/5 of the total gross land area must be a contiguous or scattered wooded area [Sec. 9.1.9.A.1].
- Tree areas must consist of either active tree preservation (minimum 2 inches of tree caliper per 100 square feet) or new shade tree plantings [Sec. 9.1.9.A.4].
- If new plantings are used, they must be either 14-inch bare-root seedlings planted at one per 100 square feet or 2-inch caliper shade trees planted at one per 200 square feet [Sec. 9.1.9.A.6].
Nutrient Loading Requirements
New development and expansions to impervious surfaces within the City of Raleigh -SWPOD occurring on or after June 1, 2011, must meet specific nitrogen and phosphorus export limits [Sec. 9.5.3.D.1.a]:
- Nitrogen: Export load must not exceed 2.2 pounds per acre per year.
- Phosphorus: Export load must not exceed 0.33 pounds per acre per year.
Developers may offset a portion of this loading by funding off-site management measures, provided they first implement on-site structural controls that achieve at least a 60% reduction in the increased loading rate [Sec. 9.5.3.D.2.c].
Stormwater Control Measures
The City of Raleigh requires specific capture and retention methods for lots in the -SWPOD that exceed 12% impervious coverage in secondary areas. The first 1/2 inch of stormwater runoff must be managed through water harvesting, infiltration, or approved treatment devices [Sec. 9.5.3.C.1.a]. For areas exceeding 24% built area, the first full inch of rainfall must be captured and managed [Sec. 9.5.3.C.1.b].
Sections Cited
- Article 5.1. General Provisions
- Article 5.2. Environmental Overlays
- Article 9.1. Tree Conservation
- Article 9.2. Stormwater Management
- Article 9.5. Watershed Protection Areas