Washington Gov. Jay Inslee has announced a plan to replace the collapsed portion of the Interstate 5 bridge over the Skagit River near Mt. Vernon after it was damaged by a truck hauling an oversize load on Thursday, closing a section of the route.

A temporary four-lane bridge is set to open in mid-June to carry I-5 traffic over the Skagit River at a reduced speed and capacity. It will consist of two, 24-foot wide spans. They will be pre-built and trucked to the site to allow for accelerated installation.

The remaining southern section has been examined and will not need to be replaced, according to the state DOT.

“We will install a temporary span on the bridge that will restore traffic while we build a safe and durable permanent span adjacent to it,” Inslee said.

A portion of a bridge on I-5 collapsed into the Skagit River near Mount Vernon on Thursday evening after a semi-truck struck critical steel supports overhead. This corridor carries 71,000 vehicles each day and is the only north-south interstate in Washington state.

Replacing the bridge

Gov. Inslee, Sec. Peterson and legislators announce plans for temporary replacement to the I-5 Skagit River Bridge. twitter.com/wsdot/status/3…

— Washington State DOT (@wsdot) May 26, 2013

Crews will immediately start work on the permanent bridge when the temporary span is put in place. Crews will put temporary piers into the river to support a platform adjacent to the collapsed span where the new section will be built. Once complete, the temporary span will be removed and the new permanent span will be moved into place. Washington state DOT hopes to have the permanent bridge open to traffic in early fall.

Inslee’s announcement prompted the immediate $1 million federal emergency quick release funding from the U.S. Transportation Department. Federal funding will make up 90% of the cost of a permanent fix. The initial estimate for the total cost of a permanent fix is $15 million.

Reduced speeds during the interim fix mean traffic backups will continue to be a challenge, both on I-5 and local roads. Drivers should still allow extra time when traveling through the area. The detours will remain in place to provide drivers with travel options. 

The home stretch will be a two-week total closure of I-5, likely in September, as crews remove the temporary structure and move the permanent bridge into place, according to officials.

Investigating the cause

The National Transportation Safety Board is investigating the incident and whether the collapse is indicative of bigger problems with the bridge.

The company hauling the load that went across the bridge, Mullen Trucking, based in Canada, says it had the proper oversize permit to use the bridge.  Washington state officials say the company had the ultimate responsibility to make sure the truck and its load had enough clearance.

The pilot car driver told Seattle TV station KING in an interview the accident was “preventable.” the station reports witnesses saying the high-pole on the pilot car touched the overhead support of the bridge, indicating the load did not have enough vertical clearance. The truck driver says he wanted to move to a lane where he could have possibly cleared, but was not able to due to another rig.

The TV station also reports Washington is one of a handful of states that does not give truck drivers routes for specially permitted loads and instead relies on truckers to determine the best route.

The bridge did not have any signs indicating the vertical clearance. The truck made it across the bridge before the section collapsed, but at least two vehicles with a total of three occupants went into the water below. They were later rescued.