The Next Page: The destruction of our historic metal bridges is the destruction of our heritage

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"Pontists," from the French word pont (bridge), is the growing community of engineers, public officials and enthusiasts who realize that, as a nation, we need to do more to prevent, or at least slow down, the replacement of historic bridges.

Pennsylvania -- and especially the Pittsburgh region -- is a ground zero for this movement.

Pittsburgh is one of the foremost "bridge cities" in America, along with New York, Cleveland, Portland, Chicago and Los Angeles, to name a few. Pittsburgh became the most important American city for bridge fabrication when J.P. Morgan consolidated 24 companies into American Bridge in 1900. A year later it became a subsidiary of Andrew Carnegie's U.S. Steel and continues building bridges.

Before that the Keystone Bridge Co., Penn Bridge, Fort Pitt Bridge Works and Pittsburgh Bridge were national leaders in the bridge-fabricating market. The threatened historic bridges I've selected to illustrate are owned by PennDOT, but other agencies are delinquent as well. Bridges are owned by counties, townships and municipalities.

Historic Bridge Weekend

Local Pittsburgh Pontists are hosting the First Annual Historic Bridge Weekend this week, July 10-12. The trip routes for the bridge weekend will be posted on

After the event, the routes will be maintained on the site. I encourage readers to take a day and follow the routes! The site is map-based to help future pontists plan their own bridge trips. -- Eric DeLony

Destroying historic bridges is destroying Pittsburgh's past.

Wooden-covered are usually the first bridge type that comes to mind when people think about historic bridges. Dark, mysterious, quaint and romantic, their settings along pastoral streams provoke nostalgia. The United States has more covered bridges than any other country -- about 750 -- and, Pennsylvania has the most of any state, currently 197.

While the loss of covered bridges are a concern, the true bridge heritage at risk are metal trusses.

The merit of the metal truss bridge

The many varieties of metal truss bridges are not easily recognizable by the layperson, yet they are technologically significant and are one of America's greatest contributions to bridge technology. The ubiquitous metal truss solved the need for thousands of inexpensive and efficiently manufactured bridges. Metal trusses are characterized by prefabricated parts made from standard mass-produced shapes and materials.

Agents representing bridge-fabricating companies would traverse the countryside, meeting with local officials to hawk their product line with claims of low cost, high durability and ease of erection. They were easily and inexpensively erected using unskilled labor.

Called "catalogue bridges" because they were sold to township supervisors and county commissioners from catalogs, many of these trusses were based on specific, proprietary patents. No other country experimented or built as many metal trusses as America did during the late 19th and early 20th centuries, when hundreds of patents for iron bridges were granted. While many came from trained engineers, others were drawn up by crafters, millwrights and mechanics.

These unschooled "apple-tree engineers" tried to make improvements, but most of their designs were impractical. While metal trusses continued to be fabricated into the 20th century, many built in the 19th century are still in use today.

Because Pennsylvania was one of the first settled areas of the United States, it should come as little surprise that it possesses the richest collection of historic bridges of any state in the Union. Its ever-expanding population and consequent transportation requirements made the Keystone State a pioneer in transportation innovation, particularly in the design of bridges.

Following the American Revolution, Pennsylvania embarked on infrastructure improvements that would not be complete until the commonwealth was knit together by a series of turnpikes, canals, railroads and highways. And all needed bridges.

Pennsylvania's historic bridges: Under threat

According to the Pennsylvania Historic Bridge Inventory, if the current trend to replace continues, all historic truss bridges that have not been preserved or rehabilitated will be demolished within the next 16 years. More than half of the historic bridges nationally, identified by statewide surveys, have disappeared over the last quarter-century since states began surveying historic bridges, according to a 2003 survey and attrition rates that states have reported since then.

Charleroi-Monessen and Hulton are two classic examples of this subtle and elegant, yet vanishing, bridge type. The other are single-span pony and through trusses, like Dorrington Road. The ones that survive are some of the most distinguished in the country blending natural setting, engineering and craftsmanship into structures worth contemplating as well as crossing.

The Dorrington Road Bridge (1888)

Dorrington Road Bridge, over Robinson Run in Collier Township, represents a classic metal, pin-connected Pratt pony truss, fabricated by the Pittsburgh Bridge Co. The 60-foot span made of wrought iron is one of 15 remaining iron bridges statewide, according to the state's 1997 survey. It is the only bridge of its type in Allegheny County.

When span requirements required longer bridges, the solution was a through truss. The upper lateral bracing gave the bridge more rigidity allowing for longer spans, typically 60 to 140 feet. These short spans can be lifted by a hydraulic crane, set on a flat-bed truck, and transported to a shop where repairs and repainting can be done under cover economically. (Although once common by Eastern standards, New Mexico, where I now live, has no such bridge.)

Estimates to relocate this 121-year-old span ranged from $250,000 to $500,000, including repair costs. PennDOT marketed this bridge, eliciting no interest. Pittsburgh History and Landmarks Foundation never came forward with anyone interested in taking over the bridge. It's simply too late now. The contract has been let. Its demolition is imminent.

Maybe everyone dropped the ball. Several trails in the area need bridges. Did anyone do any legwork to get one of them interested in relocating Dorrington Road, an eminently salvageable bridge?

Hulton Bridge, Oakmont (1908)

The Hulton Bridge is a multiple-span, subdivided Parker Pratt through truss with a channel span of 460 feet across the Allegheny River between Harmar and Oakmont. Total length is 1,544 feet. One reason the bridge is notable is because the 460-foot channel span pushes the span length of simply supported trusses. The Metropolis Bridge (1917), a multiple truss like Hulton, with a total length of 6,424 feet and a channel span of 708 feet across the Ohio River, remains the longest pin-connected simple through truss span in the world.

The bridge was named after Jonathan Hulton, one of the major landowners in the area. His son started a ferry in 1864 below the family's home, which continued to operate until the bridge was built. Constructed at a cost of $306,000, this was the first Allegheny River crossing built by Allegheny County. Hulton is typical of many multiple-truss spans threatened in Pennsylvania.

Hulton Bridge is to be replaced, not for structural reasons but for chronic congestion caused by its narrow width. The new bridge is to be built alongside the existing bridge. With the proposed Allegheny River Trail on the north side of the river, the current bridge would make an ideal pedestrian bridge connecting the historic borough of Oakmont with the trail.

In the fall, civil engineering students at Carnegie Mellon University will study converting the bridge for pedestrian use. Unless the local communities, Allegheny County and PennDOT resolve how to incorporate this bridge as part of the trailway, PennDOT plans to replace it in five years with a $75 million, four-span structure.

Charleroi-Monessen Bridge (1907)

Charleroi-Monessen Bridge is another multiple-span truss typical of Pennsylvania. I have followed PennDOT's decision whether to coax additional life out of the 102-year-old bridge or pursue a $40 million replacement.

The 1,857-foot bridge spanning the Monongahela River is listed in the National Register of Historic Places and was documented for the Library of Congress in 1997. It was closed Feb. 19 after inspection revealed deterioration in some of the vertical truss members. On April 17, PennDOT announced the three-span truss will be replaced under a design/build contract and will be completed by the end of 2011.

Rivers of Steel National Heritage Area was created by Congress in 1996 committed to preserving, interpreting and managing the historic, cultural and natural resources related to Big Steel and its related industries. It would be shortsighted to demolish Charleroi-Monessen right in the heart of the former steelmaking community. Rehabilitated, interpreted and painted anew, it could be a prominent landmark of the region's industrial past.

Spreading the word

While working with the Historic American Engineering Record, a program of the National Park Service and America's national documentation of engineering, industrial and technological heritage, we documented many sites in the commonwealth, including the iron and steel industry in Pittsburgh's Mon Valley, many engineering, industrial and architectural sites, and a selection of the commonwealth's historic bridges.

Most could argue that the commonwealth has the richest collection of historic bridges of any state in the Union.

In the Rust Belt (which I know well, having grown up in Ohio), many people view the old truss bridges as eyesores -- aging or unattractive relics of an industrial past that has left them behind.

But thanks to the historic bridge movement that has grown over the last three decades, communities are beginning to appreciate an attractively painted rehabilitated truss and preserve it rather than accepting an unattractive, utilitarian modern steel or concrete beam bridge.

Congress in 1987 encouraged the secretary of transportation, in cooperation with the states, to implement programs in a manner that encourages the inventory, retention, rehabilitation, adaptive reuse and future study of historic bridges. There is scant evidence that PennDOT has given this national policy serious consideration.

At any rate, what's been done in the past 20-plus years hasn't been working to preserve historic bridges. It sounds like it's time for change, and there is a fortuitousness about the present time for a review to move past "in a manner that encourages" to "in a manner that guarantees."

The approach PennDOT has chosen -- along with many other states, alas -- is counter to current national goals of sustainability, the green wave of architecture, and maintaining amenity in the form of historic properties and visual beauty as represented by structures like the Dorrington Road, Charleroi-Monessen and Hulton bridges. Preserving bridges like these saves historic structures. It could be less expensive than new construction, too. Saving the bridges represents national goals of sustainability, maintaining cultural landscapes, both urban and rural, and preserving riverside settings.

Some say if you leave it to black-and-white engineers, it'll come out gray. My experience is that good engineers solve complex problems. Bridges are the icons of civil engineering art. We have reached a stage that bridge officials must look beyond the artificial barriers between federal, state, local and township-owned bridges.

The loss of locally owned historic bridges demonstrates how important national guidance is needed. Congress needs to issue a national mandate that goes beyond current policy that encourages states to consider the preservation of historic bridges, regardless of ownership.

There is growing opposition by the public to their loss, but public interest coupled with political will can work wonders. Until there is national leadership outlining ways to save a selection of America's historic bridges, we have no choice but to assume responsibility for addressing these issues at the state and local levels.

Eric DeLony is chief emeritus, Historic American Engineering Record, National Park Service. ( ).


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