Thursday, June 25, 2009
Happy 170th birthday obscure little bridge
Folks in a badly-decaying town in the upper reaches of the Monongahela River are planning a party for an historic bridge that has an identity crisis. This story, below, about its noble importance appeared last week in the Observer-Reporter, Washington, Pa.
Shucks, I feel the need to be there.
By Scott Beveridge
BROWNSVILLE, Pa. – An outsider driving through downtown Brownsville would never know that under the pavement rests one of the most important engineering accomplishments in America.
The 170-year-old Dunlap’s Creek Bridge, the nation’s first cast iron span, is there – hidden below deteriorating building foundations and behind tall weeds hugging the National Road in southwestern Pennsylvania.
“It has the same designation as the Eiffel Tower and you wouldn’t even know it was there,” said Marc Henshaw, a Brownsville archaeologist who admires the old bridge.
The 80-foot-long span even rates up there with the Statue of Liberty, according to the American Society of Materials International, which designated all three structures landmarks because each represents a breakthrough in technology.
Brownsville was selected for the bridge experiment because the area had been located on a rich iron seam, which fed two local foundries that produced quality work, Henshaw said.
The U.S. Army Corps of Engineers contracted with the Herbertson Foundry in Brownsville to cast the bridge from 140 tons of pig iron purchased in Portsmouth, Ohio.
Vulcan Iron and Machine Works, owned by John Snowden, produced the wrought iron railings, according to the Historic American Engineering Record on file at the Brownsville Heritage Center.
Corps Capt. Richard Delafield opted to use cast iron because the local sandstone was not strong enough to “resist the thrust of the arch” needed to span the creek.
He didn’t want to use wood, either, because of the threat of fire and timber decay, the record shows.
It amazes Henshaw that the bridge has survived so many years of heavy automobile traffic because its engineers never imaged such vehicles would exist when they designed the structure.
The bridge probably survived because it was built with high-quality iron that remained as pure in 1921 as what could be purchased new at the time, the HAER report indicates.
By all indications, the iron is still in good condition, said Don Herbert, a bridge engineer at the state Department of Transportation, which will build new sidewalks on the span this summer.
Henshaw said the bridge is important because it “represents an achievement of the fledgling industrialization and technological innovation” in the 1830s.
The span also is important to Brownsville because it was designed, patterned and built by local residents, he said.
If only people could see it, said Norma Ryan, a volunteer director for the Brownsville Area Revitalization Corp., which hopes to demolish the foundations beside the bridge and create a park there.
“To this day, most people think it’s the Inter-county Bridge that joins Fayette and Washington counties,” Ryan said, referring to the nearby gray steel arched bridge crossing the Monongahela River.
BARC will hold the celebration from noon to 3 p.m. July 4. Space is available for vendors. For information, call 724-785-9331 or 412-969-6779, or e-mail firstname.lastname@example.org