The Yuba River Bridge at Parks Bar
1913 - 1994
William M. Thomas of Thomas and Post Consulting Engineers designed the 685-foot-long Parks Bar Bridge in 1912 for Yuba County. The original 16-foot-wide bridge with four 140-foot-long arch spans was constructed by the Portland Concrete Pile Company in 1912-13. The bridge was widened to 22 feet in 1924. It was removed in 1994 after a new bridge was built downstream.
William Thomas established himself as a leader in early reinforced concrete bridge design by developing the "Thomas System." This system consisted of precast construction, three-hinge arches and open spandrels. Each arch had three flexible connections: one on each base and one joining the arch halves in the middle. Open spandrels (triangular spaces between the arches and the deek) added to the beauty of the bridge.
Over time, the river bed lowered and eroded the bridge's base. Undermining of the footings hastened replacement of this impressive early example of the "Thomas System."
This bridge was determined eligible for the National Register of Historic Places in 1984
Marker is on Timbuctoo Road south of California Highway 20.
Courtesy hmdb.org
