Under the National Pollutant Discharge Elimination System (NPDES) municipal stormwater permit, Snohomish County must carry out a variety of actions that limit or prevent pollution from entering and leaving the county’s storm drainage system. The storm drainage system is the network of ditches, pipes and catch basins that convey stormwater on county roadways and county-owned property such as road maintenance facilities, the fairgrounds in Monroe and Paine Field airport.
The NPDES permit refers to all required actions, taken together, as a Stormwater Management Program (SWMP). The SWMP must include:
The County is also required to participate in stormwater monitoring, either directly or by paying into a regional monitoring program funded by the Washington State Department of Ecology.
Each year, by March 31, the county must prepare two documents and submit them to the Washington State Department of Ecology. One is the Stormwater Management Program (SWMP) Plan, which describes how the county intends to implement required actions during current and future years. The other is an annual report, which describes how the county carried out required actions during the previous calendar year.