One engineer's top worrisome site

If there's a bridge that keeps Chuck Davies awake at night, it's the big span on the Blue Route that crosses the Schuylkill.

Not only is it structurally deficient, by PennDot's standards, but it's one his wife, Pamela, crosses every day on her route to and from work.

"So I'm very concerned about her," he said.

It is Davies' job to worry about the safety of bridges, and worry he does.

The structural engineer, 53, is in charge of bridge and highway design for PennDot in the Philadelphia region.

No bridge now in use is unsafe, he said. But 602 of 2,720 state-maintained bridges in the area are in such critical need of immediate repairs - PennDot's words - that the state classifies them as structurally deficient.

Among the ones Davies most worries about - besides the Blue Route (Interstate 476) bridge - is another span that crosses the river. This is the Schuylkill Expressway bridge that divides Center City from West Philadelphia.

Also at the top of his concerns are a number of smaller spans that carry I-95 over the streets of Port Richmond and Northeast Philadelphia.

Statewide, more than 5,900 bridges are structurally deficient - which means they have at least one deteriorating structural component. Some are massive spans in the interstate highway system; others are small bridges over two-lane roads.

Davies, in an interview yesterday at PennDot's glass-enclosed regional office in King of Prussia, said he did not mean to imply that any bridge now open to traffic ought to be closed.

"No; the bridges are safe," he said.

But he added: "There are things I worry about. I worry about the things we might not know."

Only two major bridges in the area are of the truss type that collapsed Wednesday in Minnesota, sending eight lanes of interstate highway tumbling into the Mississippi River.

But neither of them - the Girard Point Bridge on I-95 nor the parallel George C. Platt Memorial Bridge on Route 291 - is deemed structurally deficient, Davies said.

Many of the truss bridges that were built across America decades ago - as these were - have a critical weakness.

If any support beam or pillar collapses, the whole bridge can tumble, Davies said.

Spans exactly like the Girard Point or Platt Bridges would not be built today, he said. What they require is what engineers call "redundancy" - a means to ensure that, if one support fails, another will still hold the bridge.

Asked if such additional support could be added to either bridge, Davies said: "I don't believe there is a practical way to do it now."

Asked, then, if either bridge should he replaced, he said no.

But he added: "They do have issues. We need to be out front on it. We need to do maintenance. We need to do thorough inspections."

Davies said that the Girard Point Bridge recently had major repairs and that the Platt Bridge was scheduled for $10 million to $12 million in work in 2009 or 2010.

"They are both in good condition," he said.

Each bridge is required to be inspected at least once every two years, Davies said.

Andrew Warren, a former PennDot regional administrator, noted yesterday that most of the region's bridges were small and constructed in the late 1800s or early 1900s. "Built at the same time, it's not illogical to assume they will start to deteriorate at the same time," he said.

If a bridge is deficient, weight limits may be imposed and inspections done more often.

PennDot has only a staff of 10 in the region to do bridge inspections. The bulk of the work is handled by engineering firms hired by PennDot.

"That's sufficient," Davies said.

An engineering company was working yesterday inspecting the Route 202 bridge over the Schuylkill Expressway bridge at King of Prussia. PennDot spokesman Gene Blaum said it was the only inspection work being done in the region.

The bridges that Davies said he fretted about most - the Blue Route bridge and the Schuylkill Expressway bridge - were two-girder systems.

Davies said both suffered from significant rust and corrosion. The Blue Route bridge needs a new deck.

Next year, he said, both will undergo "major rehabilitation."

Could a Minnesota-like collapse happen here?

"A collapse can happen almost anywhere," he said. "It is just a question of how thorough we are in our inspections. . . . It's really a matter of being careful."