Salmon Creek Interchange Project

Project History

A new I-5 crossing
Since the late 1990s, Clark County planning efforts have consistently reflected the need for new I-5 crossings north of NE 134^thStreet . Locations from NE 139th Street to NE 219^th Street were considered to relieve traffic congestion on the existing I-5 crossings and improve connections between neighborhoods.

As growth projections in the area changed and computer traffic modeling technology improved, traffic projections in the Salmon Creek area were refined making the need for a new I-5 crossing near NE 134^th Street increasingly clear. No other option, including widening NE 134^th Street, relieved congestion enough to meet county traffic standards on NE 134^th Street.

Interchange options considered
Since 2002, the Salmon Creek Interchange Project team considered many ways to provide access to I-5 from the Salmon Creek area. Preliminary designs were compared based on criteria that included accommodating forecasted traffic demand; minimizing right-of-way impacts, potential environmental impacts, and project cost; and meeting community expectations. Through this process, a full interchange at NE 13^9th Street was identified for further study in the environmental assessment.

Revised project design

Additional design and environmental study continued through early 2006 when more detailed information about the selected design led to increases in the original cost estimate. The project team discovered additional risks and needs as environmental, design and traffic studies progressed which resulted in increased costs. These findings included:

increases in traffic volumes forecasted over the next twenty years
evidence that the C-Tran Park-and-Ride needed to be relocated to allow NE 134 th Street to operate at an acceptable level
presence of high ground water, poor soil conditions, and a sensitive wetland in key construction areas
significant cost increases for construction materials, particularly steel, asphalt, pipe and concrete
significant increases in real estate values, which affect purchase prices of properties needed for road rights-of-way

The project design team then identified an alternative that would still achieve desired improvements to traffic flow in the area at a lower cost. Key project elements have not fundamentally changed: the revised design still includes a new connection at NE 139^th Street across I-5 and I-205, a new I-5 interchange at NE 139^th Street, and streamlined interchanges at I-5 and I-205 at NE 134^th Street .