Two remaining structures of the old Allegheny River Bridge on the Pennsylvania Turnpike will be imploded at 10 a.m. Friday.

A 268-foot span on the western side of the bridge will fall into the non-navigational backchannel of the Allegheny River and a 213-foot span on the eastern side of the bridge over the Allegheny Valley Railroad will fall on land. In addition, abutments on each end of the bridge and the eight piers in between are in the process of being dismantled.