Traffic is moving across the old Flagler Bridge again but for how long?
That’s the nagging question for local residents and commuters who have endured numerous delays over the past year from malfunctions caused by vibrations emitted from construction on a new bridge a few feet to the south.
“We did not expect settlement two weeks ago. We did not expect settlement last year. We expected to be able to build this bridge adjacent to the old bridge without having any kind of problems at all. That’s our history with numerous bridges we have built before,’’ James Wolfe, regional secretary for the state Department of Transportation, said in an interview with The Palm Beach Post.
“Of course, that means, what is our level of assurance now? We’ve run numbers again. We’ve done our best engineering. But are we certain? Well, no, we are no longer certain about what is going to happen with this old bridge.’’
Wolfe said the DOT doesn’t believe any additional underwater settling in the soil around the old drawbridge’s foundations will occur because, among other reasons, work on the new bridge’s main foundations has been suspended until May 1.
It’s what happens after May 1 that state engineers are most concerned about. And they’re not ruling out the possibility of shutting the bridge down for good at some point before the new bridge’s opening, which is projected for the fall of 2016.
“The reality is, we have a long way to go,’’ Palm Beach Mayor Gail Coniglio said. “I am fearful that we will see new glitches.’’
Vibration from work on the new bridge caused soil to move and settle under the old bridge and that subtle movement led to malfunctions in the locks that hold the movable spans in the down position.
The bridge opened to traffic again Thursday night after being shut down Nov. 12. Before that, the bridge had opened to traffic on Oct. 29, after a five-month, $9.4 million repair project triggered by settlement in September 2012, when work started on the $94.2 million replacement bridge.
Now, state transportation officials are concerned the latest problems may have caused additional wear and tear on the old bridge, which was built in 1936 and deemed “structurally deficient” and “functionally obsolete” in 2006.
The settling – about 2 ½ inches since work on the new bridge started — has been confined to the southeast pier.
“When you have settlement of one of four corners of a bridge that is different from the others (corners), you create stresses in the concrete which result in cracking. They could ultimately result in failure of the bridge,’’ Wolfe said at a news conference Thursday.
But he also said DOT engineers have carefully inspected the concrete beams “both underwater, at the pilings and the pile cap, and above water” and concluded “the bridge is still safe and traffic can run on it.’’
Still, any additional settling could lead to the closure of the bridge, meaning that traffic would be diverted to the Royal Park and Southern Boulevard bridges to the south until the new Flagler Bridge is completed in 2016.
“The margin of safety of that bridge every time we have additional settlement becomes an even greater concern,’’ Wolfe said, “but we are confident at this time, with this degree of settlement, the bridge is safe both mechanically and structurally to re-open to traffic.
“We would also suspect that the bridge is stable indefinitely, as long as we don’t work on the new bridge, but ultimately we have to work on the new bridge.’’
The settlement in the one corner also caused another problem, which is why the bridge was re-opened Thursday night to two lanes only – one in each direction – instead of four. One of the drawbridge spans, known in technical terms as “bascule leaves,” has rotated to the point that, when closed, there is a “jump” on the outside lanes by as much as 2 ½ inches, Wolfe said.
The misalignment cannot be fixed, Wolfe said. “It’s not going to be good for vehicles to drive over that bump and not good for bascule leaves to have vehicles pressing down on it when they hit that bump,’’ he said.
“That’d be quite a jolt if you drove over it in your car. But in the center of the bridge, it, in fact, matches correctly.’’
The misalignment is also causing additional stress and friction on the motors and machinery of the 75-year-old bridge.
“We can tell partly by amount of electricity, how much work the motor has to do to move the (spans), and it is greater than it used to be,’’ Wolfe said.
“This is additional wear and tear on old machinery, and it would not be surprising if in the next several months, even though we have had no additional settlement, we could start to have some mechanical problems with the motor and the bascule bridge.’’
Despite all of those concerns, the state still considers the bridge safe for use. And the state still wants to try to keep it open instead of just shutting it down.
“If we are faced with (a scenario) where we have no alternative, then we’ll have to deal with that,’’ Wolfe told The Post. “We are not there yet. We are developing a plan that will maintain traffic throughout construction.’’
Officials over the next six months will re-design the new foundations in a way that will create fewer vibrations when construction starts back up.
Options to keep the new bridge on schedule include allowing additional work crews and equipment next spring. The town will also consider allowing work to proceed around the clock, 24 hours a day and seven days a week.
“When we re-initiate the work on May 1, we expect to continue to operate traffic on the old bridge. We expect it not to settle and we are devising plans to make that happen,’’ Wolfe said before pausing a few seconds and adding: “Stay tuned.’’
FLAGLER MEMORIAL BRIDGE
• Built first as a wooden railroad bridge in 1895. Replaced and built as a railroad and pedestrian bridge at its current location in 1901.
• First modern replacement in 1938. Common design life for bridges at the time was 50 years.
• Renovated in 1995 for $2.5 million.
• Existing 80-foot horizontal and vertical 17-foot clearances are less than current U.S. Coast Guard guidelines of 125 feet horizontal, 21 feet vertical.
• Sufficiency rating in 2008 was 32.4, barely satisfactory. Sub-structure rated at level 4 (poor), on a scale of 9.
• September 2012: Construction starts at east main bridge pier.
• Early October 2012: Span locks begin to malfunction.
• Oct. 14, 2012: First of many span lock repairs.
• Nov. 5-12, 2012: Bridge closed due to settlement.
• Feb. 25, 2013: FDOT tells public its plans to close the bridge April 1.
• March 19, 2013: Bowing to pressure from politicians and major campaign contributors, FDOT announces bridge will remain open but with one lane in each direction.
• Oct. 29: All four lanes open Oct. 29 with completion of $9.4 million emergency repair.
• Nov. 12 – Bridge closes to all traffic because of span lock malfunction.
• Nov. 21 – Bridge re-opens to two lanes of traffic. Most work on new span suspended until May 1.