Cary consistently ranks among the most desirable places to live and work in the country. An important aspect of complementing economic development and environmental protection is effective floodplain and stormwater management. Cary has provided consistent leadership in this respect for over thirty-five years. The balance between growth, quality of life, and quality of the natural environment is a foundational principle. 

Cary Stormwater’s twelve programs are driven by federal, state, and local regulations. The National Pollution Discharge Elimination System (NPDES Phase II Permit) dictates six (6) of these programs.  

Specific regulations can be found in our Land Development Ordinance (LDO). Specific objectives for stormwater regulations include: protection of riparian buffers, control of nitrogen export from development, control of peak stormwater runoff, and the use of Stormwater Control Measures (SCMs). 

• Section 3.12 & 3.13 – Legal Authority (development in flood hazard area, grading permits) 

• Section 4.4.6 – Watershed Protection Overlay (impervious surface limits, SCMs) 

• Section 7.3 – Stormwater Management (nutrient reduction, peak runoff) 

• Section 14 – Environmental Regulation (illegal discharges to the storm sewer system, erosion and sediment, buffers, and flood damage prevention) 

NPDES Permit 

Cary is permitted under the National Pollutant Discharge Elimination System (NPDES) with a Municipal Separate Storm Sewer System (MS4) Permit. This means that Cary’s stormwater programs must fulfill several key requirements set by the EPA and NCDEQ. 

The Stormwater Management Plan guides programs and regulations that help keep local waterways healthy and fulfill Cary's NPDES Phase II permit requirements.  

As required by the permit, our Stormwater Program includes six (6) measures: 

• Public Education and Outreach  

• Public Involvement and Participation  

• Illicit Discharge Detection and Elimination 

• Construction-Site Runoff Controls  

• Post-Construction Runoff Controls  

• Pollution Prevention and Good Housekeeping for Municipal Operations 

History 

In 1972, the National Pollution Discharge Elimination System (NPDES) Program was established under the authority of the Federal Clean Water Act. The Phase I and II stormwater-permitted programs associated with NPDES were delegated to the North Carolina Department of Environmental Quality (DEQ) for implementation. They are currently regulated by the North Carolina Division of Energy, Mineral and Land Resources. 

In 2005, the state designated the Town as a Phase II National Pollution Discharge Elimination System (NPDES) Stormwater Program community. The Phase II permit has a five-year cycle, was renewed in 2016, and as of 2023, is in the process of being renewed again.  
 

Total Maximum Daily Load (TMDL) 

Another aspect of the Town’s NPDES Program requires that we specifically address all receiving waters in our jurisdiction that have a federally established Total Maximum Daily Load. There has been a TMDL for Swift Creek since 2009. In addition to fulfilling the six minimum measures, we further support the health of Swift Creek by: 

• Street sweeping in the Swift Creek watershed 

• Increased illicit discharge detection and elimination inspections 

• Ongoing implementation of the town-wide stream buffer program 

• Encouraging the installation of rain gardens  

• Inspecting and cleaning the sanitary sewer  

• Increased public education and outreach 

Watershed Protection 

Watershed Protection (LDO 4.4.6) 
The intent of the Watershed Protection Overlay is to ensure the availability of public water supplies at a safe and acceptable level of water quality for present and future residents of the Town and the surrounding region. 

The two Water Supply Watersheds in Cary are Jordan Lake and Swift Creek. 

Nutrient Reduction 

Nutrient Reduction (LDO 7.3.2) 
This section is intended to protect water quality for present and future residents of the Town and surrounding regions by limiting the amount of pollutants, including but not limited to nitrogen and phosphorus, in stormwater runoff.