In the second of four partial traffic shutdowns, the westbound lanes of the Highway 520 floating bridge will close this weekend for Montlake lid construction.

Contractors will install dozens of concrete girders above the roadway, similar to the eastbound closure last weekend.

The shutdown goes from 11 p.m. Friday until 5 a.m. Monday, affecting all lanes from 92nd Avenue Northeast on the Eastside to the Montlake Boulevard exit in Seattle. Drivers can still go from Montlake west to reach I-5.

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The walk-bike trail on the floating bridge will be open and quieter than usual, without any westbound traffic whizzing past.

Additional closures are scheduled Feb. 27-28 westbound, then March 6-7 eastbound.

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Eventually the lid will support plants, a walk-bike trail and a bus station when the Washington State Department of Transportation completes the new Montlake interchange and lanes over the Lake Washington shore in 2023. The entire $4.65 billion rebuild and widening program, which began near I-405, should reach I-5 in the late 2020s.

Crews lift concrete girders into place late last month over eastbound Highway 520 to construct a lid over the highway at Montlake. Girders will be installed this weekend over the westbound lanes. (WSDOT photo)

In other detours, the Highway 99 tunnel below downtown Seattle will close from 10 p.m. Friday to 6 a.m. Saturday, for maintenance and safety-system testing.

Olympia’s southbound I-5 exit to the Olympic Peninsula’s Highway 101 — a major junction that also leads west toward Grays Harbor and the Pacific Coast — will close for tree trimming Saturday and Sunday mornings from 6 a.m. to 11:30 a.m. each day. Drivers will be detoured past Olympia to the Trosper Road interchange, then backtrack on northbound I-5 to the Highway 101 junction.

Community Transit announced an opening date of Feb. 21 for a new parking lot and some bus-stop changes at Mountlake Terrace Transit Center along I-5, which is being converted to a light-rail station that will open by 2024. The parking garage will remain open.