A routine inspection of the northbound Nisqually River Bridge on Saturday, May 4 became anything but normal when our crews noticed a new crack under the 82-year-old bridge. Thankfully, their keen eyes and quick response helped avoid major delays for the 121,000 vehicles that travel that section of I-5 between Olympia and DuPont each day.
We regularly inspect all state bridges to ensure public safety, manage our facilities and properly plan for the future. These inspections allow us to monitor structure condition and address problems or damage early on before they become bigger and more expensive.
|This crack beneath the bridge deck was identified during a routine inspection of the|
northbound I-5 Nisqually River Bridge in early May.
This particular bridge – which was built in 1937 to carry both northbound and southbound traffic on US 99 (I-5 was still a couple decades away) – was last inspected in 2017.
This time, though, crews discovered a floor beam beneath the right lane on the northbound bridge deck – called a stringer – that had cracked from top to bottom, raising serious concerns. The damage was not there in the previous inspection. Concern about the safety of the bridge was enough to require a lane to remain closed until a full repair could be made. We have crews available 24/7 for critical work like this, helping minimize repair and lane closure times, and they swung into action.
Engineers from our Bridge Preservation Office collaborated with our bridge maintenance crews to design a repair. At the same time, bridge maintenance workers got ready on-scene so they could start the moment the repair plan was approved.
|A routine inspection discovered a crack from top to bottom of this floor beam – called a stringer –|
below the I-5 Nisqually River Bridge, leading to emergency repairs.
Meanwhile, because the lane closure would last longer than initially announced from our earlier inspection, our communications team went to work informing the public through our various outreach channels.
The repair was estimated to take eight hours to complete but instead, the entire fix took just under seven hours. That’s a remarkable turnaround time given the complexity of bridge repairs and the need to work next to moving traffic – and it wouldn’t have happened without many people working together to make it possible.
What did we do?
The repair plan determined that a 3/8-inch steel plate was needed on each side of the bridge stringer with a new connection to the floor beam to reinforce the damaged girder. After searching in our maintenance yard, the steel plate was not available in house but our crews found and purchased the plate from a local steel vendor and set to work on the repairs.
First crews removed the rivets and cut the steel to size. Next they placed it over the defective area and drilled new holes to secure the plate. Finally, they tied the ends together and got the highway reopened. It may sound simple, but there are many moving, complex parts that come into play, and working from a mobile platform suspended over the water does not make it easy, especially while trying to keep our workers and drivers safe and traffic moving.
|Teams from our Bridge Preservation Office as well as bridge maintenance crews collaborated on an emergency repair of the Nisqually River Bridge on I-5, fully reopening the highway just seven hours after the repair started.|
Regular inspections prevent emergency closures
Most bridge inspections on our state highways happen every two years but some can happen more often depending on concern. For example, before it was permanently closed earlier this year, Seattle’s Alaskan Way Viaduct was inspected every six months. These inspections are critical in catching small problems that can be fixed early before they become larger, emergency situations that would require our crews to shut down or restrict access to a bridge they don’t feel is safe. Besides the increased safety risk, the cost of replacing a bridge is much more expensive than repairing and maintaining it.
That said, we also understand lane closures needed for some of this work can be an inconvenience and we thank you for your patience while we got this critical work done. And of course, we extend a huge thanks to our bridge preservation engineers and our maintenance and IRT workers who pulled off this successful repair quickly and safely to get the highway fully reopened for weekend travelers. Great job!