Each year, Snohomish County is required to prepare two documents and submit them to the Washington State Department of Ecology by March 31:
In addition, the county prepares other documents such as Structural Stormwater Control Program Plans.
The NPDES Annual Report and SWMP Plan are different in two important ways. First, they address different time periods: the annual report covers the past, while the SWMP Plan covers the future. Second, the annual reports are legally-binding documents used by the Department of Ecology to determine permit compliance based on actual performance during the previous year. The SWMP Plan document is essentially a non-binding document, used to inform the Department of Ecology and the public about the NPDES permit and the actions the county intends to take to comply with it.