An environmental assessment for the project is currently underway. The state and county are required by the federal government to conduct this process to comply with the National Environmental Protection Act of 1969 (NEPA) and the Washington State Environmental Policy Act (SEPA).
Some topics covered in the environmental assessment include how the proposed project may affect:
- The natural environment such as wetlands, wildlife, and water quality
- Historic and cultural resources
- Traffic operations and community connectivity
- The surrounding community such as noise impacts, right-of-way acquisition
Following the extensive study of design options beginning in 1997, the environmental assessment will consider changes that would occur in the area if the proposed project is constructed compared to a no-build option. Both options share the same assumptions about growth.
- The build alternative looks at what the area and traffic would look like in 20 years if the proposed project were constructed (see below).
- The no-build alternative looks at what the area and traffic would look like in 20 years if the proposed project were not constructed.
Salmon Creek Interchange Project Build Alternative
The Salmon Creek Interchange Project includes improvements and changes to the interstate system and local streets.
Freeway improvements
The build alternative will:
- Construct a new interchange at I-5 and NE 139th Street that provides for movement in three directions
- Remove the on-ramp from NE 134th Street to I-5 northbound and relocate to NE 139th Street. Associated changes will be made to the traffic signal on NE 134th Street
- Reconstruct I-5 bridges over I-205 to accommodate future I-5 widening
- Construct a new lane on I-5 northbound between NE 139th and NE 179th Street
- Add an exit-only lane to NE 134th Street from I-205 northbound resulting in a two-lane off-ramp
- Realign northbound I-205 to the west at NE 139th Street to accommodate vertical clearance requirements with NE 139th Street.
Local road improvements
The build alternative will:
- Construct a new segment of NE 139th Street from NE 10th Avenue to NE 20th Avenue that passes over I-5 and I-205
- Widen NE 139th Street to two lanes in each direction, with bike lanes, a sidewalk on the south side, and a median from NE Tenney Road to the Legacy Hospital driveway
- Redesign of the intersection of NE 139th Street and NE Tenney Road to a âTâ configuration with NE 139th Street being the main through route
- Widen NE 10th Avenue between NE 134th Street and NE 141st Street to one lane in each direction with a center turn lane, bike lanes and sidewalks
- Modify the traffic signal and intersection on NE 134th Street and NE 10th Avenue to accommodate the other changes in the area and truck movements
- Improve the intersection of NE 20th Avenue at NE 139th Street with double left turn lanes and right turn lanes in all directions
- Relocate the C-Tran Park-and-Ride from NE 134th Street to a new location near the corner of NE 139th Street and NE 10th Avenue