The Washington State Department of Transportation is advising travelers that three of the four westbound Highway 16 lanes on the westbound side of the Tacoma Narrows Bridge will be closed this Thursday night, Sept. 19.

At 8 p.m. Thursday, bridge maintenance crews will close the two left westbound Highway 16 lanes across the bridge. At 9 p.m., they will close a third westbound lane.

The right westbound lane will remain open all night, as will ramps near the bridge.

All three westbound lanes will reopen by 6 a.m. Friday, Sept. 20.

During the closure, crews will chip out small areas of concrete in the bridge deck to expose, repair and reinforce about six steel bars that have broken loose inside the deck.

Officials said similar work was done in 2011 when bridge crews repaired several bars in an adjacent lane.

The bars were embedded in the bridge deck’s concrete when the Tacoma Narrows Bridge was originally constructed in 1950. The deck has hundreds of such bars, whose purpose is to connect the deck to the bridge’s steel expansion joints.

Officials said welds on the bars break due to metal fatigue caused by the daily pounding of traffic. When that happens, bridge maintenance crews either replace the bars or fix them.

In the work planned for later this week, crews will repair the existing bars as well as install new bars to reinforce the area.