SHARECOMMENTMORE

MINNEAPOLIS -The sound of heavy work being done is unmistakeable, but outside the Plymouth Avenue bridge in Minneapolis there is nothing happening.

What gives?

As it turns out, crews are working inside the span that crosses the Mississippi River. The Plymouth Avenue bridge was built with box girder spans,hollow concrete tubes that are basically long, windowless rooms that stretch across the river.

It's inside the girder spans that repairs are being done. Other than the occasional truck or cement mixer on the bridge's deck, no other construction work can be seen.

The bridge is expected to reopen to traffic in mid-October when construction season wraps up. Additional construction will be needed in 2013, but the bridge will remain open to traffic while those repairs are made.