Wading through the Stormwater Runoff Rules
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(April 2007)
Two of these – NR 216 and NR 151 – are discussed most frequently within our communities. What are these rules, and how do they apply to your municipality?
Wisconsin Administrative Code Chapter NR 216: Stormwater Discharge Permits
This code establishes the procedures and requirements for WDNR stormwater discharge permits issued to applicable construction sites, industrial facilities, and municipalities to limit the discharge of polluted runoff into public waters. The code applies to communities with:
- 10,000 or more residents OR
- Urbanized area communities that together have a population of 50,000 or more and an overall density of at least 500 people per square mile.
Wisconsin Administrative Code Chapter NR 151: Runoff Management
This code establishes runoff performance standards for stormwater management systems. NR 151 focuses on requirements to minimize the entry of sediment and other pollutants into waterways. The rules address agricultural sites, construction sites, post-construction sites, and transportation systems. Initially these rules applied only to sites greater than 5 acres, but they now apply to sites of 1 acre or more.
Construction Site Requirements
New development and redevelopment construction sites of 1 acre or more require implementation of an erosion and sediment control plan that employs best management practices (BMPs) that reduce the annual average sediment load leaving the site by 80% (compared to a site with no BMPs).
Post-Construction Site Requirements
Once construction is completed and stabilized, sites need to meet post-construction standards. Owners need to develop and implement a written stormwater management plan that meets the following WDNR standards:
Total Suspended Solids: For new development, stormwater management features must control 80% of the total suspended solids that would normally leave the site. For redevelopment, the goal for total suspended solids removal is 40%.
Peak Discharge Rate: For new development and redevelopment, the peak runoff discharge rate for the two-year, 24-hour design storm must be the same as or less than the pre-development runoff rate for the same storm.
Infiltration: For new development residential sites, infiltration of stormwater runoff must be provided for 90% of the pre-development infiltration volume, or 25% of the post-development runoff from the two-year, 24-hour storm, using an infiltration area comprising up to 1% of the area of the site. Commercial and industrial sites are required to infiltrate at a lesser percentage. Pretreatment of runoff from parking lots and roads is required before entering an infiltration system.
Protective Areas: For new development, permanent vegetative buffer areas (usually 50 to 75 feet wide) must be maintained around lakes, streams, and wetlands to filter pollutants and minimize erosion.
Fueling and Maintenance Areas: For fueling and vehicle maintenance areas, all visible gasoline or oil sheen must be removed from runoff leaving the site.
Information and Education: By March 2008 permitted municipalities will be responsible for implementing public education aimed at reducing polluted runoff through management of leaves, grass clippings, lawn and garden fertilizers and pesticides, pet wastes, oil, and other chemicals. These local governments also will have to address leaf and grass management, proper nutrient application schedules for municipally owned property, and detection and elimination of illicit discharges.
