Traffic won't begin flowing on the new Pensacola Bay Bridge until at least Aug. 4, the Florida Department of Transportation announced Friday in a last-minute delay to the switch originally planned for Sunday.

The department said the delay was caused by recent bad weather and "an ambitious schedule from the contractor."

The new dates for the bridge switch are Aug. 4 for eastbound traffic (Pensacola to Gulf Breeze) and Aug. 8 for westbound traffic (Gulf Breeze to Pensacola).

For weeks, officials have prepared drivers for a planned traffic switch that would take place for the eastbound lanes on Sunday and for the westbound lanes on Thursday.

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The Pensacola Bay Bridge $400 million replacement project is the largest infrastructure project in the history of Northwest Florida.

The existing bridge, which opened in 1960, carries more than 55,000 vehicles back and forth between Pensacola and Gulf Breeze each day. It has survived everything from hurricanes to barge strikes.

Plans call for demolition of the existing bridge to begin once traffic begins flowing on the first expanse of the new bridge. The entire project is scheduled for completion in mid-2021.

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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.

Ian Satter, a spokesman for FDOT's regional office, said 17th Avenue between Gregory Street and the Graffiti Bridge will closed from 8 p.m. Aug. 4 through 6 a.m. Aug. 8, as part of the bridge switch.

Drivers will be detoured using Ninth Avenue and Cervantes Street, he said.

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