Starting Monday, the Flagler Memorial Bridge in West Palm Beach will be closed for six months.

The Florida Department of Transportation is closing the bridge as construction crews work on a section of a $94.3 million replacement bridge that is being constructed nearby.

The 86-year-old bridge that spans the Intracoastal Waterway has been sinking since work began on the replacement bridge two years ago. In that time, the state DOT has closed the bridge twice before, but those closures were only for a few days.

At one point, the state considered permanently closing the old bridge because of concerns about safety. But the town of Palm Beach protested, and the state spent $9.4 million on emergency repairs to shore up the old bridge's foundation, including giving the contractor a $675,000 bonus for completing the work early.

Not long after those repairs were completed, the state had to close the bridge for a few days because the bridge had sunk again.

The six-month closure comes as work begins on the main foundation for the movable sections of the new drawbridge.

"In the past, the bridge settling coincided with work on those main bridge piers," said Tish Burgher, a FDOT spokeswoman.

So FDOT is closing the old bridge in case the foundation work for the replacement bridge has some impact on the old bridge.

Traffic will be detoured to the Royal Park Bridge, which will include a new traffic pattern. Drivers going south on Flagler Drive will not be able to go east on the Royal Park Bridge, and drivers going west over the Royal Park Bridge will not be able go south on Flagler Drive

The old bridge is expected to reopen Nov. 1. The new replacement bridge is scheduled to be finished in 2017.

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