Mirra said the city’s Historical Commission wanted to install a old-fashioned manual-crank, similar to the original, rather than an electrical crank.
He said workers have removed tons of asphalt and concrete from the bed of the bridge and replaced it with modern composite material which is much lighter.
The month-long delay means vehicles that would normally use the bridge, including school buses, must continue using alternate routes until late September. As a consequence, students riding buses to nearby Whittier Regional High will face longer rides than usual during the first month of school.
The historic bridge, built in 1883 and rebuilt in 1914, was closed to traffic on June 18 of last year, forcing drivers who used the 812-foot span to find alternate routes.
According to state transportation officials, the Rocks Village Bridge contains the oldest movable span among all bridges presently under MassHighway control. It is located next to the Rocks Village National Register Historic District, on a site which has been utilized as a major Merrimack River crossing since the early 18th century. To date, only 44 movable bridges have been identified in the MassHighway database. The Rocks Village Bridge, the oldest of them all, is still operated by hand.
As one of the earliest riveted metal trusses yet identified in the MassHighway inventory, the Rocks Village Bridge is also the earliest known surviving work of the Boston Bridge Works, a Massachusetts bridge building firm active from the 1870s through the 1930s.
When you can start crossing bridges
Sept. 29: Rocks Village Bridge repairs to be complete
Early next year: The new Groveland Bridge (officials have no specific date)