Repair Bill Is Coming Due for `Baby Boom' of Bridges

SUE McNEIL, fresh from Australia, remembers driving across Pittsburgh's Liberty Bridge and feeling anything but free. ``I was literally terrified,'' recalls Ms. McNeil, a civil engineer. ``It was just a very old, rusted structure.''

Ten years later, Pittsburgh's most important bridges have undergone extensive repairs. Now, engineers are concerned about the secondary structures. The picture here is typical of the nation as a whole. While the United States is taking better care of its most visible transportation infrastructure, secondary roads, bridges, and other structures are getting short shrift.

``Just as there is a baby boom ... we have a bridge boom that came out of the first 10 years of the Interstate [highway] program,'' says Francis D. Fran,cois, executive director of the American Association of State Highway and Transportation Officials.

Already, 238,400 of the nation's 577,700 bridges are structurally deficient or functionally obsolete. In the next 20 years, another 140,000 bridges will fall into one of those categories.

The situation in Pittsburgh is much the same. After decades of neglecting the problem, the city began to tackle it in the 1980s. Of the 19 road bridges that span the city's three rivers, six have undergone major rehabilitation since 1983, eight are scheduled for important maintenance in the next several years, and the rest are either new or in sufficient shape to last awhile, state and county officials say.

The major impetus for the rebuilding program was a 1982 Pennsylvania measure that targeted bridge repair and replacement and set up a 12-year state plan through which local governments could attract federal and state money for their projects. According to Jerry Johnson, district bridge engineer for the Pennsylvania Department of Transportation, engineers today have a much better idea of the condition of the various structures than they did 10 years ago. Still, the state is barely ahead of the national average. In June 1988, 41.3 percent of the nation's bridges were structurally deficient or functionally obsolete.

If Liberty Bridge is refurbished, Pittsburgh's Shadeland Avenue bridge is definitely not. It has scores of potholes and badly peeling paint. It is one of four large bridges that have city officials worried. They are considering reducing the bridge's vehicle load limits from 5 tons to 3 tons, virtually eliminating all trucks.

Despite the state's bridge-renewal program, funding remains the biggest problem, says Richard Connors, project manager of the bridge and structures division of Pittsburgh's engineering department. Since 1978, 53 bridge projects have been completed at a cost of more than $50 million (much of it paid for by federal and state money). But the competition for further funding is heating up as communities vie to make their projects a state priority. And money is tighter. Of 41 Pittsburgh bridges on the state's 12-year plan two years ago, all but 16 have been pushed off the list by other priorities, Mr. Connors says.

Six of his city's projects were completed, he adds, and the other 10 would cost an estimated $19.2 million. But he says the city needs $30 million to keep up with the deterioration problem.

``There's a big backlog left over,'' adds Steven Fenves, a bridge expert and a civil-engineering professor at Carnegie Mellon University. ``The smaller the bridge, the more difficult it is to accumulate funding for it.''