Changing Skyline | Shivers on South St. Bridge

Posted: August 03, 2007

A bridge falls in Minneapolis and the tremors are felt in Philadelphia.

After Wednesday's horrific collapse of the arched truss bridge over the Mississippi, it was natural for Philadelphians to wonder if their decrepit South Street Bridge is safe. The converted railroad bridge, built over the Schuylkill for the Centennial celebrations of 1876, has been shedding its concrete skin like someone with a bad sunburn. Trucks and buses weighing six tons or more were banned in January. And like the Interstate 35W bridge in Minnesota, the South Street Bridge has been tagged with the ominous federal designation "structurally deficient."

You can almost hear nervous officials bleating in unison for the long-planned $50 million reconstruction to start immediately. So what if the current design transforms Philadelphia's most thrilling Center City gateway into an interstate-grade cattle chute?

Ever since the Streets Department unveiled its final renderings for the bridge in January, unhappy neighborhood and business groups have been urging the agency to return to the drawing board. The groups say they are starting to make headway with the city. Now they fear that the Minneapolis collapse will spook officials into ending the conversation.

Obviously, the South Street Bridge should be closed immediately if engineers deem it is unsafe - and so far they haven't. But even if that worst case were to occur, there are compelling reasons for the city to produce a new design, rather than proceed full speed ahead with a flawed reconstruction plan.

Closing the bridge now would probably cause months of disruption for the legions of drivers, bicyclists and pedestrians who cross every day between Center City and the University of Pennsylvania. But Philadelphia's pedestrians and bikers will be cursing their fate for decades if the current bleak design is built, with its stingy sidewalks and flimsy turret outlooks. The South Street Bridge is meant to be a gracious pedestrian span that links two dynamic neighborhoods, not just an efficient delivery system for automobiles heading for I-76.

Terry Gillen, the neighborhood's Democratic Party ward leader and a staff member for Michael Nutter's mayoral campaign, believes the city and its consultants could produce a new, improved design in under six months.

"If they had been told in January to start over by someone in authority, like the mayor, it would have been done by now," she argues.

Actually, the city has known since 2001 that neighbors wanted a more fitting design for the gateway bridge, which offers a breathtaking, wide-angle panorama of the Philadelphia skyline. After the Streets Department first released a preliminary design for reconstruction, neighbors complained the scheme was ugly. Officials promised improvements. Six years of silence followed. When the "final" design was unveiled in January, it looked an awful lot like the 2001 version, despite the laudable addition of a ramp to Schuylkill Banks park.

James C. Campbell, an architect and a member of the South Street West Business Association, has been leading the crusade for a better gateway. Now he worries that if engineers decide to shut it down, "we're going to look like the bad guys" for delaying the project.

It's not surprising that a fatal bridge collapse on the scale of Minneapolis' would force Philadelphia to take a hard look at the South Street Bridge project. When you walk across the span, the sidewalks vibrate like a just-plucked guitar string, and you can see visible gouges in the roadbed as you bolt toward terra firma. The Streets Department has put the bridge reconstruction at the top of its priority list.

But just because the bridge looks dangerous doesn't mean it is. The crossing is built like a tank, with huge steel girders that rest on massive piers. In contrast, Minneapolis' arched truss bridge was assembled from hundreds of pieces of bolted and welded steel. The more joints, the more opportunities for a single piece to fail, dooming the whole structure.

Christopher Menna, Philadelphia's chief design engineer for bridges, noted that even if something were to happen to one of the South Street Bridge's girders, "there are multiple girder lines to carry the load." In other words, the bridge deck wouldn't collapse all at once. What's more, the existing girders were stiffened with extra steel during a renovation in the 1980s.

Even in its crumbling state, the South Street Bridge is an inspiring balancing act, leaping over 300 feet of river in a single bound. Designing a new span that is both comfortable for pedestrians and functional for cars will also be a balancing act.

In the meantime, walk quickly.


Contact architecture critic Inga Saffron at 215-854-2213 or isaffron@phillynews.com.

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