-SWPOD: Swift Creek Watershed Protection Overlay District Guide
The City of Raleigh’s Swift Creek Watershed Protection Overlay District (-SWPOD) protects the integrity of Class WS-III drinking water by imposing strict impervious surface limitations, natural resource buffer requirements, and a 40% forestation rule. This overlay prohibits specific high-impact uses, such as new landfills, and requires advanced stormwater control measures for developments exceeding base intensity thresholds [Sec. 5.1.1.B.5, Sec. 9.5.3.G].
Purpose and Prohibited Uses
The -SWPOD is designed to provide clean and safe water for the residents, businesses, and ecosystems of the City of Raleigh and surrounding communities. To ensure this protection, the City of Raleigh prohibits the following uses within the Swift Creek Watershed Protection Overlay District, regardless of the underlying base zoning:
- New landfills; and
- New sites for the land application of sludge, residuals, or petroleum-contaminated soils [Sec. 5.2.5.B].
Impervious Surface Coverage Limitations
The Swift Creek Watershed Protection Overlay District is divided into primary and secondary reservoir watershed protection areas. The City of Raleigh limits the amount of built-upon area (impervious surface) based on the specific area and whether the property is connected to both City water and sewer utilities.
Maximum Impervious Surface Coverage
| Area Type | No Stormwater Control Measures | With Retention, Detention, or Capture (First 1/2" Runoff) | Management of First Inch of Rainfall |
|---|---|---|---|
| Primary Area | 6% impervious; or 3,500 sq. ft. if ≤ 12% total | N/A | N/A |
| Secondary Area (No City Water/Sewer) | 12% impervious; or 3,500 sq. ft. if ≤ 24% total | N/A | N/A |
| Secondary Area (With City Water/Sewer) | 12% impervious; or 3,500 sq. ft. if ≤ 24% total | 24% impervious surface | 30% built area (standard); 50% built area (lots ≤ 3,500 sq. ft.); up to 70% in Comprehensive Plan designated areas |
[Section 9.5.3.B.1]
Watercourse Buffer Requirements
The City of Raleigh requires the establishment of natural resource buffers along all perennial watercourses within the -SWPOD. These buffers are measured perpendicularly from the edge of the watercourse bank [Sec. 9.2.3.A.1].
-SWPOD Buffer Width Standards
| Watercourse Type / Condition | Required Buffer Width (Each Side) |
|---|---|
| Drains 25 or more acres | 60 feet |
| Drains 5 to 25 acres | 35 feet |
| Stream draining less than 5 acres | 35 feet |
| Secondary area with > 24% impervious surface | 100 feet |
| Special Flood Hazard Areas (SFHAs) | Adjoining primary buffers |
| Slopes 15% or greater | Adjoining primary buffers or SFHAs |
[Section 9.2.3.A.2]
Forestation and Wooded Areas
Every lot within the City of Raleigh -SWPOD must provide and maintain a wooded area set aside for trees equal to at least 40% of the total lot area. This requirement is subject to the following rules:
- Contiguity: Tree areas may be one contiguous area or scattered, but no single required area can be less than 1/5 of the total required set-aside [Sec. 9.1.9.A.1].
- Active Preservation: Active tree preservation areas must contain a minimum of 2 inches of tree caliper per every 100 square feet [Sec. 9.1.9.A.4].
- New Plantings: If the area does not meet preservation standards, it must be planted with shade trees. The minimum rate is either 1 bare-root seedling (at least 14 inches tall) per 100 square feet or one 2-inch caliper shade tree per 200 square feet [Sec. 9.1.9.A.6].
- Exemptions: This does not apply to lots in the Comprehensive Plan designated for impervious surfaces exceeding 30% [Sec. 9.1.9.E].
Required Stormwater Measures
Developments within the City of Raleigh -SWPOD that exceed 24% impervious surface must implement specific capture and retention methods.
- Runoff Treatment: The first 1/2 inch of stormwater runoff must be retained for harvesting/use, infiltrated into the soil, evaporated, or captured by an approved treatment device [Sec. 9.5.3.C.1].
- Street Runoff: If impervious coverage exceeds 24%, the first inch of stormwater running off any street must be contained within the development using the same retention or capture methods [Sec. 9.5.3.C.2].
- Use of GSI: In secondary watershed areas where built area exceeds 24%, runoff must be controlled on a volume basis so that post-development runoff is equal to or less than pre-development levels (assumed forested) based on the 90th percentile storm [Sec. 9.5.3.C.3].
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