CENTRALIA – Girder setting for a new couplet bridge over Interstate 5 near Mellen Street will reduce the interstate to a single lane in each direction for six hours, starting at 10 p.m. Monday, Dec. 16.
Five 152-foot-long concrete girders arrive by truck Monday night. The trucks will park in the closed left lanes on both directions of I-5 just south of Mellen Street. Two cranes working from each side of the interstate will pick up the girders and set them in place over the lanes of I-5.
“It’s never ideal to take I-5 down to a single lane, but with the method we’re using to build this bridge, it’s the only way we can set these long girders,” said Washington State Department of Transportation Project Engineer Colin Newell. “The work is being done late at night, which will help keep backups from getting too bad.”
Crews will also slow drivers on I-5 periodically to create gaps in traffic and keep drivers from being under the girders while they’re being set. Drivers should expect congestion in the area and are encouraged to consider alternate routes if they enter or exit I-5 at Mellen Street.
Girder setting is a major milestone in bridge construction. Once girders are set and secured, crews will start building the 154-foot-long, 43-foot-wide bridge deck. They will first build a wooden support structure around the deck, then place and tie together mats of steel rebar and pour concrete to form the driving surface.
Once the bridge is complete, crews will build the ramps and connecting roadways, and reconfigure the existing Mellen Street intersection. When the couplet is complete in late 2014, traffic will move in a counter-clockwise direction, improving traffic flow in the historically congested Mellen Street area.
WSDOT is overhauling 4 miles of I-5 in Centralia. The I-5 Mellen Street to Blakeslee Junction project constructs new collector-distributor lanes, a couplet system at Mellen Street, safety improvements north of Blakeslee Junction, congestion relief at the Mellen Street and Harrison Avenue interchanges, and a new local travel option via the Louisiana Avenue-Airport Road connection.
The project is funded through the 2005 gas tax and is the last in an eight-year-long, $168 million effort to improve safety and congestion on I-5 in Lewis and south Thurston counties.