Work to repair the corroded Plymouth Avenue bridge, closed since October 2010, finally got underway Monday.

But the work means that the bridge, which has been closed to its typical daily traffic of more than 14,000 vehicles, also will be closed to foot and bike traffic until the first phase of work is completed, scheduled for Oct. 15.

When that portion is ready, the repair work will continue with lane closures rather than a total shutdown of the bridge, according to the city's Department of Public Works.

The bridge closed after it was discovered that hollowed sections of box girders, held in place with cables, had been damaged by salty water. The moisture ate into the concrete as well as some of the cables.