Tampa Bay area bridges have been in the news recently.
While the new Howard Frankland Bridge opened March 25, a national report released a week earlier said the Sunshine Skyway needs a "vulnerability assessment."
The National Transportation Safety Board included the Skyway on a list of 68 bridges that should be assessed for the risk of vessel strikes.
The report does not state that the structures mentioned are at risk of collapse.
Rather, it urges groups like the Coast Guard and U.S. Army Corps of Engineers to "form a dedicated, interdisciplinary team that provides guidance and assistance to bridge owners on evaluating and reducing the risk of a bridge collapse from a vessel collision."
Mark Luther is the director of the Ocean Monitoring and Prediction Lab at the University of South Florida. As an expert on oceanography and maritime studies, he has served on multiple regional planning committees and conducted research funded by the National Oceanic and Atmospheric Administration.
"Simply driving on any highway around here is much more dangerous than the risk of collapse of the bridge," Luther said.
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The cable-stayed span opened in 1987, seven years after a freighter struck a pier of the original truss superstructure during a morning thunderstorm. As the roadway crumbled, 35 people died when their vehicles – including a bus – plunged 150 feet into the bay.
Luther believes that the main reason why the Skyway was included on the list is because it was built before the 1991 Guidelines for Bridge Management Systems by the American Association of State Highway and Transportation Officials existed.
The 1980 Skyway disaster greatly influenced the developement of the guidance.
Luther said "they went to great lengths" to reduce the possibility of a collapse when the Skyway was designed — especially since its predecessor was destroyed by a vessel strike.
Three main features add to the bridge's safety, he said:
- Rip rap, which is a pile of rocks that enforce the main supports.
- Dolphins, which are large rock islands that span up to 65 feet across and extend 15 to feet above the water to block stray vessels from crashing into the bridge.
- The tall center span of the bridge extends 180 to 182 feet above sea level, which means ships will rarely be tall enough to get stuck underneath.
The NTSB's report comes a year after the Francis Key Scott Bridge in Baltimore collapsed after a vessel lost power and crashed into the structure.
Luther thinks the likelihood of that happening in Tampa Bay is low.
"It's not that unusual for a vessel to lose power on the way in or out of the bay," he said. "But unless it happens mere seconds before they approach the bridge, then they can deal with it simply by steering it out of the channel or throwing out an anchor."
Something the Tampa Bay Area Maritime Security Committee is worried about, however, is the possibility of someone intentionally sinking a vessel under the Sunshine Skyway.
At a March 26 meeting, Luther said that such an event would block the ship channel and "totally disrupt the economy of the region for weeks, maybe even months."
The NTSB's report only included two Florida bridges — the Skyway and Jacksonville’s Dames Point Bridge.
And while a review would help assess their vulnerability to collisions, Luther said "it's highly unlikely that there could be any collapse at the new Skyway bridge."
