Stormwater is rain water and snow melt that collects on the ground as a result of rain and snowfall. When this water flows across the surface of the ground it picks up soil and pollutants and carries them to the nearest stream, river, or lake. Stormwater is NOT TREATED at the treatment plant.
Duluth's stormwater utility system consists of 451 miles of pipe, over 100 miles of ditches, and about 3000 culverts. Storm drains and catch basins carry stormwater from the streets and parking lots to the nearest waterway. Catch basins are the heavy steel grates located along the curbs, usually near intersections. There are nearly 12,000 catch basins in the City of Duluth.
Impervious surfaces are materials that do not allow water to infiltrate into the ground. Asphalt parking lots and streets, concrete sidewalks, rooftops, and compacted gravel areas are examples of impervious surfaces. Impervious surfaces create runoff that must be captured and carried by Duluth's storm sewer system.
RESIDENTIAL: Storm water fees are calculated based on the number of Equivalent Residential Units (ERU)s on a property. One ERU equals 1,708 square feet of impervious surface. 1,708 square feet is the average impervious surface area in Duluth for a single family home. All residential buildings are billed 1 ERU per living unit.
COMMERCIAL/INDUSTRIAL: Commercial/Industrial properties are billed based on the total square footage of impervious surface on the property (typically buildings and parking lots). The total impervious square footage of a commercial property is then converted to ERUs. For example, a medium-sized business might have a total impervious surface of 11,000 square feet. 11,000 sq. feet/1,708 sq. feet per ERU = 6.4 ERUs.
If you have any questions or concerns about stormwater, or if you would like to review and comment on the City of Duluth's SWPPP please contact the Stormwater Program Coordinator at 218-730-5200.