KYW Newsradio Team Coverage
One thing Philadelphia shares with Minneapolis: a river runs through it. And that means numerous bridges in varying states of disrepair.
KYW's Mike Dunn reports this keeps inspectors busy.
Philadelphia has about 350 bridges over water and land, and officials keep a close eye on them:
“Our policy is to inspect all 350 every two years.”
Kevin Koch is chief highway engineer for the Philadelphia Streets Department:
“Some of our structures are obviously in need of repair. Some are programmed for replacement (in the future) right now. The vast majority are not in that bad shape in the city.”
Probably in the worst shape is the heavily traveled South Street bridge (top photo), which is slated to be rebuilt entirely, beginning next spring. Trucks and buses are now barred from that bridge, and Koch says it is inspected weekly.
(Top photo: KYW's Tony Hanson)
KYW's Steve Tawa reports that the Delaware River Port Authority says it subjects each of its four bridges to regular in-depth inspections.
The DRPA looks after its two suspension bridges (the Benjamin Franklin, opened in 1926; and the Walt Whitman, opened in 1957) and its two outer steel truss bridges (the Commodore Barry, opened in 1974; and the Betsy Ross, opened two years later).
DRPA chief engineer William Brooks:
"All of DRPA's bridges have been certified to be in good or satisfactory condition."
Brooks says they do inspections every two years, plus an underwater inspection is done every four years for each bridge:
"The underwater inspections look for scouring, erosion, undermining of the footings, or other damage below the water line."
Brooks says they have an aggressive and proactive program of identifying elements of each bridge in need of attention:
"Consequently, the bridges have been maintained in good condition, in keeping with the Authority's philosophy that they need to last forever."
The Minnesota bridge was rated as "structurally deficient."
KYW's Tony Romeo reports that a spokesman for the Pennsylvania Department of Transportation says the agency is compiling a list of state-owned bridges that are similar in design to the one that collapsed in Minnesota.
Penndot spokesman Steve Chizmar says the agency is identifying all of the multiple-span, steel-deck truss bridges owned by the state:
“Once we have the list compiled, we’ll basically hold it until the details emerge from the bridge collapse in Minnesota. And then, based on what is found out there, we can take any necessary actions.”
But Chizmar cautions not to jump to conclusions about what caused the catastrophe in Minnesota. Likewise, he says, don’t jump to conclusions about the fact that 6,000 of Pennsylvania’s 25,000 state-owned bridges are deemed "structurally deficient" in some way.
He says the "structurally deficient" designation does not mean a bridge is unsafe. Chizmar says all bridges owned and maintained by Penndot are inspected at least once every two years. In some cases, load limits may be imposed. And he says any bridge deemed to be unsafe is closed.
Despite thousands of them that are deemed “structurally deficient,” Governor Rendell says he believes Pennsylvania bridges are safe.
The governor says bridges are aggressively inspected, and that ‘structurally deficient’ bridges get special attention.
“There’s a reasonable amount of certainty in crossing every bridge in Pennsylvania. Does that mean I can guarantee that a tragedy like happened in Minnesota can’t happen here? Of course not.”
Penndot has identified 30 truss bridges of the same design as the doomed Minnesota bridge, none of them in the five county southeastern region. Most of them are in western Pennsylvania, half of them in Allegheny County alone.
KYW's Tony Hanson reports that local authorities train frequently to respond to such a disaster here.
The excercises are often linked to acts of terrorism, but the training and lessons learned apply to all emergency responses.
Philadelphia police captain Kenneth O'Brien, the Marine Unit commander, says they have six boats:
"We also have a jet boat which is for a quick response. For a tragedy such as this, I think what would be the key is a quick response. Our boats do two patrols, usually about two, 2½ hours each day on both rivers, so a quick response would be formidable if we are out on the river should something like this occur."
Capt. O'Brien says they've also developed a close relationship and good lines of communications between and among agencies, including the Fire Department, US Coast Guard, and other agencies which would be involved in an emergency water response.
A professor of civil engineering at Drexel University says "everything fails at the connections."
KYW's Steve Tawa spoke with Drexel professor Joseph Martin, who notes that the bridge span came down intact:
"That's what saved so many lives; it didn't break up and shatter. There was one place where there was clearly a snap."
Martin (right), who started with the New York highway department in 1971, says he cut his teeth on watching the first-generation interstate highways and bridges go up -- those just like the Minnesota span, built in 1967:
"At the time, we had reasonable design standards. They would have expected so many cycles of fatigue. They also built into this bridge, being in Minnesota, cycles of expansion (and) contraction."
He believes it was that kind of expansion joint that gave way, in an inaccessible area that might be difficult to inspect on a regular basis.
Martin says newer bridges have hatches that give inspectors the ability to inspect structures more closely.
(Martin photo: Drexel Univ.)
KYW's Ed Kasuba spoke with an associate professor of civil engineering at Rowan University, who predicts it will take several months before the cause of Thursday’s bridge collapse in Minnesota can be determined.
Yusuf Mehta (right) says the failure of one critical part of the bridge is all that’s needed in this type of catastrophe. And, he says, even with regular inspections there is no guarantee of a visual clue in advance of this type of collapse:
"It may seem like this should be easily visible, but it’s not as simple as that.”
And since the bridge was being resurfaced, he notes, anything that was visible should have been noticed by the workers doing the routine maintenance.
(Mehta photo: Rowan Univ.)
KYW's Jim Melwert spoke with a physical geographer with a specialty in hydrology at Rutgers University who says the Mississippi River is in the Minneapolis area a dangerous, fast moving river, not the waterway that Tom Sawyer travelled.
Dr. Robert Hordon says while most people think of the Mississippi as a meandering, wide river, that's not the case around Minneapolis.
"Any time you get a flow in the river that is being forced through a narrower channel, then in order to balance that equation, then the velcity has to go up. So I can see how this would be capable of bringing down a lot of sediment."
"We're looking at a river system that is simply gigantic, but the part of the Mississippi where this occured is more in the rocks. So you have a very limited flood plain."
To compare it to something locally, he says the stretch of the Mississippi river in Minneapolis is more similiar to the Delaware River north of Trenton, N.J.
He says there's a lot of agriculture upstream of Minneapolis, and the run-off makes the water murky, causing even more problems for recovery workers.
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