I-90 Two-Way Transit & HOV Operations

In early 2015, IMCO Construction began work on this federally funded highway project in Seattle, Washington valued at over $120 Million. The contract was phase 3 of a three-phase $220 Million project to provide significant improvements to regional mobility, adding HOV lanes and direct-access ramps for transit and HOV traffic on Mercer Island and in Bellevue. A major component of this project was adding infrastructure to build the Sound Transit East Link Light Rail Extension from Seattle to Mercer Island, Bellevue, and Redmond. The project was implemented in stages due to timing and availability of funding.

IMCO Construction was contracted to update the life safety systems and construct HOV lanes in each direction between Mercer Island and Seattle, preserving pavement in both directions from I-5 across Lake Washington to Bellevue. The project built an eastbound HOV direct-access exit ramp at Island Crest Way and upgraded the I-90 tunnels’ fire and life safety systems.

IMCO crews performed modified concrete overlay in seven locations with only one 56-hour closure to complete this portion of the work, which required careful planning to meet tight deadlines and minimize impacts to traffic. These solutions included using a Texas Screed instead of a time-consuming bridge deck paving machine. IMCO’s scope also included major updates to existing fire and life safety systems and associated mechanical infrastructure inside the tunnels including the installation of 60 by 90 by 20-foot Saccardo Nozzles inside incredible tight space. IMCO’s design team scanned the nozzles to create a model and merged the nozzle models with the model of the installation site to see corrections that needed to be made prior to delivery.

This project team partnered with dozens of vendors and subcontractors and carefully coordinated lane closures and weekend closures throughout the project lifecycle, scheduling through WSDOT and local officials to ensure proper notice was given to the traveling public and impacts were mitigated.