Frith Rd./ Pine River

County: St. Clair

City/Township: St. Clair Twp.

Location: Frith Rd./ Pine River

Year Built: 1914

About this Bridge:
The Firth Road Bridge over the Pine River is located in a rural area southwest of Port Huron. The main span of the bridge is a seven-panel, pin-connected Pratt through truss. A single stringer span provides an approach to the east; to the west are two wood-and-concrete spans. The truss contains the following members: upper chord: back-to-back channels with cover plate and battens; lower chord: two looped bars; end verticals: pair of square-section rods; other verticals: back-to-back channels with V-lacing; diagonals: two looped bars; counter: two looped square-section rods; bottom and top laterals: round rods; portal bracing: paired angles in A-form; sway bracing: two pairs of angles with V-lacing; floor beams: I-beam bolted to angle riveted to plate below vertical; railing: modern metal guardrail.

The original deck and stringers have been replaced by a laminated timber slab. Wood curbs edge the roadway on the approach spans. There are roller bearings at the east end of the truss.

The Michigan Department of Transportation database gives a construction date of 1914. While the floor system has been replaced, and the metal on the truss has rusted, the structure's integrity is relatively good.