Construction crews on the new Pensacola Bay Bridge are scheduled to lift an 800,000-pound steel arch into place atop the bridge on Thursday.

The Florida Department of Transportation is urging drivers who are traversing the existing bridge to keep their eyes on the road while the work is taking place.

The navigational channel beneath the bridge will be closed to marine traffic and the U.S. Coast Guard will patrol the area to maintain a safety buffer during the work, the department said.

"The arch is a signature architectural element for the new bridge that will also provide structural support for the multi-use path included on the bridge," the department said in a news release.

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The $389.5 million Pensacola Bay Bridge replacement project is the largest infrastructure project in the history of Northwest Florida. The first eastbound expanse of the new bridge is scheduled for completion later this summer.

Plans call for traffic to flow in both directions on the first expanse of the bridge while the existing bridge is demolished and the second, west to east, bridge expanse is constructed.

The entire project is estimated for completion in mid-2021, according to FDOT.

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The new bridge will consist of two parallel structures, each equipped with three travel lanes, adjacent inside and outside shoulders, and 10-foot multi-use paths for pedestrians and bicyclists, FDOT said.

Melissa Nelson Gabriel can be reached at mnelsongab@pnj.com or 850-426-1431.