State highway officials said they are closing the U.S. 11 bridge over the Potomac River in Washington County tomorrow for a month for emergency repairs ordered after a routine inspection found that one of the bridge's support piers was sinking.
Earle Freedman, the state's chief bridge engineer, said yesterday that the 82-year-old, two-lane bridge is expected to reopen to vehicles weighing less than 7,000 pounds on July 3, after the initial phase of the $400,000 repair job.
The 1,700-foot-long steel girder structure, located southwest of Hagerstown, is expected to reopen to vehicles weighing more than 7,000 pounds by mid-August.
Russ Ulrich, a spokesman for the highway administration, saiinspectors noticed more than a month ago that the one of about 20 piers supporting the bridge, which normally carries 4,200 cars a day, had settled slightly into the river bottom.
Mr. Freedman said measurements showed that the pier -- one of four not built on bedrock when the bridge was erected in 1909 -- had settled between 1/8th and 3/16ths of an inch. "It's a very small movement in a very large structure," he said. "But the point was there was movement, and that's what concerned us." Such settlement, he said, sometimes occurs in buildings and bridges for reasons that are not always clear.
In early May, the state imposed a 30,000-pound weight limit on the bridge and inspected the affected pier frequently for further sinking.
Those measurements, although not conclusive, suggested that the pier had continued to sink, Mr. Freedman said. So officials imposed a 7,000-pound weight limit while urgent repairs were arranged.
Although highway officials are concerned about the settling, Mr. Ulrich said, the bridge is not in danger of collapsing.
The contractor on the project is expected to work seven days a week through June to shore up the sinking pier and reopen the bridge to light traffic, Mr. Freedman said. The contractor will then buttress the other three piers not built on bedrock, he said, before the bridge fully reopens in mid-August.
The state is expected to pay $80,000 of the cost of repairs, Mr. Freedman said, while a federal grant will pay the balance.
Over the next month, motorists will be directed to detour around the U.S. Highway 11 bridge using Route 68 (Conococheague Street) and the Interstate 81 bridge, about a mile south.