Swedish contractor Skanska has signed a contract with the transport department of Washington State to replace the Portage Bay Bridge in Seattle.

The $1.4bn design-and-build project will involve the erection of two parallel bridges and the placing of a landscaped “lid” over the SR 520 – the road that crosses the bay – between 10th Avenue East and Delmar Drive East.

The department commented in a press statement that Skanska’s bid was the “apparent best value”, and “exceeded our engineer’s estimate”.

The department added that the project was part of a larger programme of works to reconstruct the SR 520 corridor from Bellevue to Seattle, a distance of about 17km.

James Bailey is executive vice president of Skanska USA Civil’s West Coast operations. He commented in a press statement: “Our work to replace the Portage Bay Bridge is an important piece of broader improvements to the SR 520 corridor, one of the busiest across the Puget Sound region.

“The project will work to ensure safer travel across the bay, improve mobility and add more connections to Seattle’s non-motorised trail network.”

The eastbound span will extend the regional bicycle and pedestrian trail across the bay. The Roanoke Lid, as the cover is called, will create 1.2ha of recreational space and reconnect communities cut off by the SR 520.

Construction is expected to begin in August and to complete in 2031. US engineer Aecom will serve as the lead designer for the project.