The southbound I-5 Stillaguamish River Bridge was built in 1933. It originally carried two lanes in each direction of US 99. When I-5 was built in the 1960s, the bridge became part of the freeway. In 1971, a new bridge was built just east of the original one to carry three lanes of northbound I-5. The old bridge continued to handle three lanes of southbound I-5.
After 81 years, the 1933 bridge’s deck has worn out and some of the supporting steel framework underneath has rusted. Because of this, the bridge is considered structurally deficient. These parts of the bridge need to be replaced. When the work is complete, the bridge will no longer be listed as structurally deficient.
To keep traffic flowing in both directions of I-5 as this work is done, in 2014 contractor crews for WSDOT will build crossover lanes to northbound I-5 on either side of the Stillaguamish River. The northbound bridge will be reconfigured to carry traffic in both directions, and southbound I-5 will be shifted to share that span. One previously installed camera and one new one will help WSDOT and the public monitor bridge traffic.
The southbound bridge will be closed for four months. During this time the bridge deck will be removed and portions of the steel framework will be replaced, then a new deck will be installed. In fall 2014 the refurbished bridge will reopen to southbound traffic and the crossover lanes will be removed, restoring the area to its previous condition.
sourced – graphics/photo courtesy WSDOT