Skip Top Navigation

Environmental Mitigation

SR-18 stream mitigation
SR-18 stream mitigation


In addition to roadside restoration, WSDOT Landscape Architects and designers restore according to regulatory requirements. Types of regulatory related projects include (but are not limited to) wetland mitigation, stream restoration and wetland/stream buffer enhancement.

Environmental Mitigation Resources

Environmental Procedures Manual

Standards of Success for Wetland Mitigation
The Wetland Mitigation Standards of Success Study was a project of the Roadside and Site Development Unit of the Washington State Department of Transportation (WSDOT). It was designed to identify scientifically-based benchmarks for establishing vegetation success standards on wetland compensatory mitigation projects.

Phase One of this study was completed in October 1999. It included a literature review of plant succession in Pacific Northwest wetlands, identification of potential study sites, a pilot study, and a recommended work plan for Phase Two.

Phase One Report (pdf, 130kb)

Annotated Bibliography (pdf, 57kb) of research on wetland ecology and success standards in wetland mitigation

Phase Two of this study surveyed and documented structural characteristics of vegetation within forested and scrub-shrub zones of wetland mitigation sites 6-11 years old. Each site was freshwater, located within the Puget Trough of Washington, and contained established stands of woody vegetation. Quantitative data were recorded on cover and density of woody vegetation, as well as cover of reed canarygrass. Additional qualitative observations included hydrology indicators and hydrogeomorphic settings, soils, herbaceous vegetation, and surrounding land use. Through this data, benchmarks for performance standards were proposed for forested and scrub-shrub components of wetland mitigation projects.

Phase Two Report (pdf, 239kb)

The study was funded by the Environmental Protection Agency (EPA) and WSDOT.

Environment/Ecology
Environmental Legislation Affecting Transportation

International Institute for Sustainable Development

National Wetlands Inventory

Stream Restoration, US Dept. of Agriculture-NRCS

Swiss Federal Research Institute WSL

WSDOT and Wetlands

toptop