Stormwater Resources

Stormwater runoff occurs when precipitation from rain or snowmelt flows over the ground. Impervious surfaces like driveways, sidewalks, and streets prevent stormwater from naturally soaking into the ground.

Stormwater can pick up debris, chemicals, dirt, and other pollutants and flow into a storm sewer system or directly to a lake, stream, river, or wetland. Anything that enters a storm sewer system is discharged untreated into the water bodies we use for swimming, fishing, and providing drinking water. Polluted stormwater runoff can have many adverse effects on plants, fish, animals, and people.

Polk County administers a Stormwater Management Program (SWMP) that has been created for the area of Polk County located within the City of Salem urban growth boundary (UGB). This program was developed to meet the Municipal Separate Storm Sewer System (MS4) permit requirements of the National Pollutant Discharge Elimination System (NPDES), and is reviewed and updated annually. If you would like to learn more about Polk County’s SWMP, please contact the Polk County Community Development Department at (503) 623-9237.

Post-Construction Best Management Practices.

Roof tops, parking lots, and driveways create impervious surfaces that concentrate stormwater run-off. Stormwater flowing over these developments pick up oil and other particle matter that can be harmful to riparian ecosystems. In order to decrease the quantity and increase the quality of stormwater that enters the County rivers and streams, construction operators should plan how to minimize stormwater runoff from new development prior to beginning construction. The following links provide technical guidance in implementing practices that can be used to minimize the impact of development on County rivers and streams:

• Maintain native vegetation along rivers, streams, and sloped areas of your property: Trees and other vegetation provide stream bank stability and minimize erosion caused by rain events. Streamside vegetation also provides a natural filter for sediment that becomes suspended in stormwater.

• Vegetated/Grassed Swales:

° EPA Fact Sheet

° California Stormwater Quality Association Guidance Document

 • Bioretention (Rain Gardens):

° EPA Fact Sheet

° Wisconsin Extension -- How-To-Guide

• Pervious Pavement & Porous Asphalt:

° EPA Fact Sheet - Pervious Concrete Pavement

° EPA Fact Sheet - Porous Asphalt

° California Stormwater Quality Association Guidance Document

• Rain Barrel Construction:

° City of Portland, OR Guidance Document

° City of Bremerton, WA Guidance Document