|December 2012 (39.0242 Degrees, -120.7207 Degrees) North Fork Bridge|
It's a long drive through switchbacks down Mosquito Ridge Road to this bridge across the North Fork of the Middle Fork of the American River. The bridge makes almost a 180 degree turn from one side of the canyon to the other as it crosses the river. Its a four span steel deck truss on four-legged towers (and with a smaller two column bent in front of the north abutment).
I found the following information from the always reliable Bridgehunter website. The 'North Fork' Bridge was built in 1946 and it's a steel Warren deck truss with a main span length of 84 ft, a total length of 492.8 ft, and a 24 ft width. It's owned by the US Forest Service, it's in extremely good condition, and it only carries 50 vehicles a day.
The tower legs are longer facing the river and the back legs are on big caissons. I would have made the legs the same length on a flat surface, but maybe they were afraid of undermining the slope with too much digging. I imagine that after the war, steel suddenly became available for things like bridges. They must have built the towers and then dropped in the truss spans. Building the curved alignment could have been tricky but I think the truss spans are straight with a curved deck sitting on top.
Placer County, California Bridges: Mosquito Ridge Road Bridge across the North Fork of the Middle Fork of the American River by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 License.