EVERETT — To place the Grand Avenue Park Bridge requires a carefully choreographed dance between two constructions crews, the city of Everett and BNSF Railway.
Nearly a football field in length, the steel bridge will carry utility lines and pedestrians from Grand Avenue Park over West Marine View Drive and five rail lines to the waterfront. A 10-day road closure, between 13th and 18th streets, began Tuesday for the installation.
Two heavy downpours last week almost delayed the $20 million project, but city crews worked overnight to repair three outfalls along Marine View to ensure it continued on schedule.
The stormwater and sewer pipes underneath the bridge will help prevent flooding by moving water off streets above Marine View Drive.
Even so, the project would not have completely alleviated the flooding after the unprecedented amount of rain from two storms that occurred in quick succession earlier this month, according to Heather Griffin, an engineer with the city.
Catch basins on the street can’t handle more than three inches of water a day, she said. Nearly four inches of rain fell during that 24-hour period last week.
Mounted underneath the bridge are three utility pipes. Once connected, a combined stormwater and sewer pipe will link to two outfalls that empty into Possession Sound near Boxcar Park. This will be used during heavy rain events. A second pipe will carry stormwater to an outfall just north of where the bridge will be placed.
A third will move sewage east over the bridge and later toward a facility on Smith Island.
Over the course of several days, crews will lift, rotate and attach the bridge, which for several months sat assembled on the side of Marine View.
Over the weekend, crews drove a self-propelled transporter underneath the steel bridge and built the first of four lifting towers needed to raise the structure.
This week, workers plan to construct the rest of the lifting towers and move the bridge into the middle of Marine View. Then, two beams between each set of towers will slowly hoist the 1 million pound structure over the course of a day.
After it reaches about 36 feet, a foot higher than the eventual height, a second transporter will scoot underneath.
Then crews will place a steel structure on the transporters and lash it to the bridge. This allows for the removal of the south towers, which gives enough room to rotate the structure 90 degrees.
Towering above the road and railroad tracks, the bridge will then be driven south by the transporters and swung around.
On the east side, two pin bearings, similar to very large door hinges flipped sideways, will secure the bridge to the platform. Gravity holds it in place on the other end, according to Ken Kettel, resident engineer with KBA Construction Management, the firm building the bridge.
“So it can slide when it gets hot and expands,” Kettel said.
Installing a bridge over active rail lines is not easy or cheap.
The city paid about $300,000 to BNSF to construct the bridge across the tracks. The city will also be charged for costs associated with the installation.
Once the bridge is placed, the next step is to install the deck and lighting before it can open, set to happen in 2020.
Lizz Giordano: 425-374-4165; firstname.lastname@example.org; Twitter: @lizzgior.
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