Work will begin Monday to replace a 61-year-old bridge in Chanceford Township that engineers have deemed structurally deficient.

The bridge carries Gum Tree Road over the south fork of Otter Creek. About 300 vehicles travel the route each day, according to PennDOT.

PennDOT awarded a $718,919 contract for the work to Dillsburg-based Lobar Site Development Corp. The company will demolish the existing single-span steel bridge and replace it with a concrete one.

Beginning Monday, Gum Tree Road will be closed to traffic between routes 425 and 74 until the end of the year, according to a news release. Gordon House Road will also be closed to traffic.

A detour will follow Gum Tree Road, Route 425, Lucky Road and Smith Hollow Road.