SR 520 - I-5 to Medina Project - Natural Resource and Parks Mitigation
When planning transportation projects, WSDOT first seeks to avoid or minimize adverse effects to the environment. If a project has unavoidable effects, we must mitigate for those effects. To mitigate for effects to parks, wetlands and aquatic resources associated with the I-5 to Medina project, we are proposing mitigation activities at several sites. Additional information about these proposed mitigation activities can be found by clicking on the individual sites shown on the above map.
To identify these mitigation sites, WSDOT has undertaken a comprehensive screening process in coordination with local, state and federal regulatory agencies, stakeholders, and tribes. Opportunities for on-site mitigation have been maximized to the extent possible. However, on-site mitigation is limited by existing land use, high density development surrounding the project area, and overall insufficient area available for mitigation. WSDOT will restore construction-related impacts on-site. For any remaining unavoidable temporary or permanent impacts, WSDOT will also conduct mitigation at off-site locations.
Additional information on the natural resources mitigation planning process and proposed wetland and aquatic mitigation sites can be found in the Wetland Mitigation Plan and Aquatic Mitigation Plan.
WSDOT proposed to enhance the shoreline by removing bulkhead structure along the shoreline, replanting shoreline vegetation, and supplementing gravel in Lake Washington to improve salmon habitat. The mitigation proposed at Seward Park continues work previously begun by the Seattle Parks Department.
Total area of aquatic mitigation: 2.69 acres
Proposed mitigation at Taylor Creek calls for stream and delta restoration by reconstructing the channel, establishing an active and accessible floodplain, and planting the riparian buffer with native vegetation. This work is a continuation of the stream restoration proposed and being pursued by Seattle Public Utilities at the site and upstream of Rainier Avenue.
Total area of aquatic mitigation: 0.97 acres
Proposed mitigation at this site includes restoring shoreline vegetation, enhancing shoreline, and removing structures, which will improve conditions for salmon migrating from the Cedar River (located adjacent to the site) to Lake Washington and Puget Sound.
Total area of aquatic mitigation: 3.97 acres
WSDOT will work with the City of Redmond to improve salmon habitat by restoring portions of Bear Creek, through re-alignment and reconstruction of the channel, riparian and floodplain restoration, and planting of native riparian vegetation.
Total area of aquatic mitigation: 15.78 acres
WSDOT proposes to improve salmon habitat at the East Approach of the new SR 520 floating bridge. This work will include removing structure and bulkhead, supplementing spawning gravel, and restoring shoreline.
Total area of aquatic mitigation: 0.89 acres
Proposed mitigation at the Union Bay Natural Area includes wetland enhancement and establishment, which consists of grading, removing invasive and non-native species, replanting with native species, and enhancing wetland buffers. The proposed mitigation supports and continues work previously begun by the University of Washington as part of the Union Bay Natural Area Master Plan.
Total area of wetland mitigation (including wetland buffer enhancement): 25.70 acres
Proposed mitigation at the WSDOT Peninsula will include wetland re-establishment in a historically dredged area, wetland enhancement through the removal of existing invasive and non-native species, grading, replanting with native vegetation, and wetland buffer enhancement. The proposed mitigation also includes establishing wetland in previously dredged areas.
Total area of wetland mitigation (including wetland buffer enhancement): 9.04 acres
WSDOT proposes to conduct both wetland and aquatic mitigation at Magnuson Park. Proposed wetland mitigation includes wetland establishment and enhancement, which consists of grading, removal of existing invasive or non-native species, replanting with native vegetation, and enhancement of wetland buffers. Proposed aquatic mitigation includes shoreline enhancement, which involves removing structure along the shoreline, replanting with shoreline vegetation, and supplementing gravel. The proposed mitigation continues work previously begun by the Seattle Parks Department as part of the .
Total area of aquatic mitigation: 1.55 acres
Total area of wetland mitigation (including wetland buffer enhancement): 19.82 acres
WSDOT proposes to conduct both wetland and aquatic mitigation at the Elliott Bridge Reach site, located on the Cedar River. The proposed combined mitigation would include lowering the existing levee to allow overbank flows, removing floodplain fill material behind the levee, and establishing a forested floodplain-wetland mosaic. Components of the aquatic mitigation will also include restoring gravel bar habitat and creating an off-channel backwater slough with large woody debris elements. The site will be planted with native vegetation, and a setback levee will be constructed to protect adjacent infrastructure and downstream residences.
Total area of aquatic mitigation: 4.16 acres
Total area of wetland mitigation (including wetland buffer enhancement): 4.27 acres
