BURLINGTON The permanent span goes in Saturday night, Sept. 15, but for the next two months, drivers will still experience some detours around the Interstate 5 bridge over the Skagit River.
The bridge and that section of freeway will be closed from 7 p.m. Saturday to 7 a.m. Sunday to slide the span into place.
Then crews start work Monday to increase the overhead clearance on the entire bridge. I-5 will be closed nightly between College Way in Mount Vernon and George Hopper Road in Burlington.
The bridge will be completely closed on seven nights, from 8 p.m. to 8 a.m. on weekdays and 9 p.m. to 9 a.m. on weekends. It will be partially closed 36 times (18 closures in each direction) from 9 p.m. to 5 a.m. Monday through Saturday.
The state Department of Transportation has not announced exact dates for each closure, but expects the $2.5 million to $3 million project paid with federal emergency-relief money to take until mid-November.
Detours during the closures will be the same as when the bridge was out this summer: Trucks are encouraged to use the Riverside Bridge just east of I-5, while passenger cars can use that route or several others, including Highway 20 and Memorial Highway or Highway 9.
Signs will mark detour routes. Drivers also can find detour maps on wsdot.wa.gov.
An overheight load struck critical steel supports on May 23, sending a northern span of the bridge and two vehicles into the Skagit River.
Three people were rescued, none seriously injured.
That was just one of many hits the bridge has taken from oversize loads over the years. Upping the height of the bridge's steel trusses will reduce the risk of it happening again, DOT officials say.
The project also will convert the steel support structure so it is the same height over both lanes. The current structure is curved, making its vertical clearance 18 feet in the middle but only 15 feet 6 inches at the fog line the white line on the right side of the road.
The truck that spurred the collapse was too tall to be in the outside lane and struck a lower point in the structure.
After the upgrade, the vertical clearance over all lanes will be 18 feet.
"This bridge is the lowest steel structure in the state of Washington over I-5," said Polly Brooks, DOT assistant project engineer, when the project was announced. "We will be increasing the clearance by approximately 4 feet, and it will no longer be the lowest structure."
While they work on the overhead structure, crews also will paint, replace rivets below the deck and do other needed reinforcement and maintenance, bringing the total cost of the work to $4.1 million. Funding for this other work is not eligible for federal emergency money.
Issaquah-based PCL Civil Constructors, Inc. was awarded the contract for the project on Aug. 7.
The contractor will be rewarded for shaving off closure days, $50,000 per full closure and $10,000 for partial closures, to a maximum of $200,000, a DOT traffic engineer said when the project was announced.
Similarly, the contractor will see penalties in those amounts for any additional closure days.