Wetland Mitigation in Washington State is a two-part interagency document providing guidance on wetland mitigation. You can access the current mitigation guidance documents at this link: https://ecology.wa.gov/Water-Shorelines/Wetlands/Mitigation/Interagency-guidance
Ecology worked with the Environmental Protection Agency (EPA) and the U.S. Army Corps of Engineers (Corps) to update Part 1 of the interagency wetland mitigation guidance that was originally published in 2006.