National Pollution Discharge Elimination System (NDPES)

Stormwater runoff is the number one source of water pollution. This is according to the 1996 National Water Quality Inventory Report to Congress. Urbanization leads to increased runoff volumes and rates as there is no way for precipitation to infiltrate through these impervious surfaces. As a result, we are seeing accelerated stream flows, stream bank and shoreline erosion and a decline in aquatic habitat. This also leads to increased stormwater runoff pollutant loads and concentrations.

The pollutants most commonly associated with stormwater runoff that enter our surface and groundwater include pesticides, herbicides, fertilizers, oils, heavy metals, salt, sediment and pathogens. These accumulate on driveways, parking lots, sidewalks and other hard surfaces and are transported with the stormwater runoff.

The Stormwater Program for Municipal Separate Storm Sewer System (MS4) operators is intended to reduce the pollutant loading to water resources from storm sewer systems to the “maximum extent practicable.” Stormwater discharges are regulated through National Pollution Discharge Elimination System (NPDES) permits. Through this permit, Chanhassen, as an owner/operator of a storm sewer system must develop a stormwater pollution prevention program (SWPPP) that uses a variety of best management practices (BMPs) to achieve this goal.

The State of Minnesota adopted MN Rule Chapter 7090 in August of 2005 to implement the NPDES requirements. On August 1, 2013 the General Permit Authorization to Discharge Stormwater Associated with Small Municipal Separate Storm Sewer Systems under the National Pollution Discharge Elimination System/State Disposal System (NPDES/SDS) Permit Program MNR040000 was established.

Under the new permit, existing permit holders were required to submit an MS4 SWPPP Application for Reauthorization. This application must describe how the MS4 is in compliance with the new permit or what steps they will take and the anticipated schedule to come into compliance with the new permit. Chanhassen’s application was deemed complete and is available for public comment. The document can be found at the link below or is available as a hard copy at Chanhassen City Hall. You may also request that a copy be sent to you either electronically or via U.S. mail by contacting Joe Seidl.