By Shanon D. Murray and Edward A. Walls
HAGERSTOWN, Md. – After 162 years of use, Booth’s Mill Bridge in Washington County is showing its age.
Its stone walls are cracking and shifting. They’ve bulged more than three inches since 1986, said Jim Aguirre, a Maryland State Highway Administration engineer. The state recently closed the bridge to traffic until next spring, when a $1.1 million repair job will be complete, Aguirre said.
The Booth’s Mill Bridge deterioration is not unique, bridge engineers said.
Of at least 43 stone, iron and timber bridges built in Maryland in the 19th century, more than 20 need work, said Aguirre and county engineers working on the projects.
More than a dozen have already been rehabilitated, according to SHA and county bridge data.
The good news, from a preservationist’s perspective, is that care is now being taken to repair the bridges without destroying their historical features.
That is a new development, said Beth Hannold, a preservation officer with the Maryland Historic Trust. She said bridge engineers have only recently begun to reach some “understanding and appreciation” of the historic structures.
In past decades, crumbling old bridges put preservationists and engineers at odds. While historians stressed the value of keeping the structures intact, engineers wanted modern bridges requiring lower maintenance.
“There wasn’t much consideration for historical value in the olden days. It was whatever goes,” said Terrence McGee, a Washington County public works engineer.
He noted that from an engineering perspective, there are better and more cost-effective alternatives than rehabilitating old structures.
When engineers did rehabilitate old bridges, they often did so with new parts, Aguirre said. The historic value of five Washington County bridges was ruined by bridge engineers who rebuilt them, McGee said.
For instance, Devil’s Backbone Bridge, a 171-year-old stone arch on state Route 68 in Washington County, was devalued in 1977 when state engineers encased the stone walls in concrete to prevent further bulging, Aguirre said.
“It’s a rehab failure,” said Aguirre, a Civil War buff. “You can’t see any of the stones.”
The bridge is scheduled to be restored again in the next few years to remove the concrete, he said.
“It’s our job to do what we can to preserve these bridges for Marylanders and people from around the country,” Aguirre said.
A bridge’s historic worth is determined by federal criteria rating its connection to noted persons or events, its age and method of construction, Hannold said.
Washington County has 18 historic bridges dating from the 19th century – more than any other county in the state, Hannold said. The bridges were built near local mills to help transport products made there, furthering the county’s economic development, Hannold said.
County funds will be used to rehabilitate more than a dozen of the bridges at a cost of at least $100,000 each, McGee said. Three of the 18 bridges don’t need rehabilitation, Aguirre and McGee said.
The county will require contractors fixing the bridges to keep the structures’ historical values intact, McGee said. They must clean, repair and re-use the bridges’ original materials whenever possible.
Washington County engineers expect to begin work in September on the 165-year-old Dogstreet Bridge, a stone arch near state Route 67 whose walls are “showing significant signs of bulging,” McGee said.
“The walls are moving considerably,” he said.
The weight of cars, trucks and buses has compacted waterlogged soil under the roadway – originally built for horse- and-buggy traffic – and pushed the bridges’ stone walls outward, Aguirre said.
“Water probably damages bridges more than anything you can think of,” he said.
Booth’s Mill Bridge will undergo similar renovations.
Contractors will dismantle the bridge’s walls layer by layer and replace bridge fill with concrete and better drainage systems, Aguirre said.
Care is also being taken in Frederick County with the restoration of 10 19th-century bridges, some timber, some metal, said Ken Harwood, the bridge repair manager. He said they will be restored in the next few years, at a cost for each ranging from $15,000 to $600,000. The original materials will be used to repair the timber, steel and wrought iron bridges, Harwood said. -30-