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Project Evaluation: I-90, I-405 Vicinity Bridges - Seismic

Bellevue, King County
Crews installed 45 steel column jackets on the bridges at the I-90/I-405 interchange to  reduce the risk of catastrophic failure during earthquakes and bring them up to current seismic standards.

Design:  Construction Management:  Schedule:  Cost:  Engineer's Estimate: $ 2,477,367 Contractor's Bid Amount: $ 1,725,575 Anticipated final payment to contractor: $ 2,291,487

Construction Summary
The project is substantially complete.  The I-90/I-405 interchange now meets current seismic safety standards.  Adding wetland plants is the only work remaining.

This project was delayed one year to reduce the risk of environmental damage and permit violations.  In 2004, WSDOT biologists re-evaluated several bridge piers and determined that their construction could only occur during the short period of time when the work is least likely to affect endangered fish, known as the fish window.  WSDOT decided to retrofit those piers in 2005 to reduce the added costs, make the work more efficient and reduce the risk of violating environmental permits.  Almost all additional costs are due to this delay.

Contact Information

Contractor: 
Mowat Construction, Woodinville

WSDOT Contact:
Brian Dobbins, Project Engineer
(425) 956-2114
dobbin@wsdot.wa.gov

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