Butte County, California Bridges: Route 162 Bridge across the Middle Fork of the Feather River

August 2015 (39.54987 Degrees, -121.42988 Degrees) Lake Oroville Bridge

This week's bridge crosses over the Middle Fork of the Feather River. The water level is so low now that the bridge looks like it did when it was first built. It's a suspension bridge, which is one of the easier long span bridges to build. Once you drape the cables over the towers (and anchor them) you can just work from each end hanging the superstructure until they meet in the middle.

Chico State University has archived many photos that were taken during construction of the bridge and the dam. It's surprising how many long span bridges were designed and built during the period when the dams were being constructed. Sepulveda Dam was completed by the USACE in 1941, Shasta Dam was built by the USBR in 1945, Oroville Dam was built by the CDWR in 1965, etc. Who were all these bridge engineers?  There seems to be a boom period for different places when money is available and amazing infrastructure is created.

This week's bridge has several names. It's called the Bidwell Bar Bridge because it replaced an old bridge by that name that we'll look at next week. It's called the Lake Oroville Bridge because its the most impressive of the bridges over Lake Oroville. Caltrans calls it the Middle Fork of the Feather River Bridge (12 0188) after the obstacle that it crosses. It carries the Olive Highway, which is also called the Oroville-Quincy Highway and it's officially called California Route 162.

The main span is 1108 ft long and the entire bridge is 1793 ft long. The roadway is 28 ft wide with sidewalks on both sides of the roadway. It's an interesting bridge because it is on a horizontal curve with the suspension cables anchored to the side of the deck. Note how there are no back stays on the bridge. Instead, there are concrete piers to support the back spans on both ends of the bridge. Eric Sakowski writes that it's the highest reservoir bridge in the US. The towers are 350 ft tall and were built about 300 ft above the bottom of the river.

Butte County, California Bridges: Route 162 Bridge across the Middle Fork of the Feather River by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Butte County, California Bridges: Enterprise Bridge Carrying Lumpkin Road across the South Fork of the Feather River

August 2015 (39.53636 degrees, -121.33944 degrees) Enterprise Bridge

Every river flowing out of the Sierras (except for the Smith River near California's northern border) is dammed at least once before it reaches the valley. The Oroville Dam was completed in 1968 and filled the branches of the Feather River with Lake Oroville. Long, tall bridges were needed to cross these swollen river branches.

Last week we looked at the West Branch of the Feather River Bridge. In today's blog we've moved to the southeast side of Lake Oroville to look at the Enterprise Bridge across the South Fork of the Feather River. The Enterprise Bridge (12C0199) is a 1175 ft long continuous three span deck truss bridge that was built in 1967. As can be seen in the photos, California's drought has reduced the South Fork to a trickle.

These continuous truss bridges were popular for medium long spans in the 1960's. However, I doubt if they would be built today. All of the bridges with spans between 400 to 1000 ft in length that have been built recently in California have either been concrete arches (like at Devil's Slide) or segmentally constructed concrete box girder bridges (like the new Benicia Martinez Bridge). California hasn't even built a long span steel girder bridge let alone a steel truss in many years.

Butte County, California Bridges: Enterprise Bridge Carrying Lumpkin Road across the South Fork of the Feather River by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Butte County, California Bridges: State Route 70 Bridge across the West Branch of the Feather River

The Sacramento is the largest river in California and the Feather River is its principal tributary. We previously visited bridges on the Feather River in Yuba County. However, the really big bridges are across the branches higher up in the Sierras.

The first bridge we visited is the State Route 70 Bridge across the West Branch of the Feather River (12 0134). It's a double deck truss bridge that carries the highway on the top deck and the Southern Pacific Railroad on the lower deck.

This bridge is composed on four, 576 ft long Warren truss spans for a 2730 ft total length (with the approach spans). The always reliable Eric Sakowski states, "The second highest double decker road and rail bridge in the world after the Pit River Bridge, the West Branch Feather River cantilever bridge is one of 4 high spans that cross Lake Oroville in Northern California. The creation of America’s deepest man-made lake started in the early 1960s when construction began on the Oroville Dam. Completed in 1968, the earth fill structure is the highest in the United States measuring 770 feet (235 meters) from base to crest."

I'll visit bridges across Lake Oroville and across the various branches of the Feather River over the next few weeks.

Butte County, California Bridges: State Route 70 Bridge across the West Branch of the Feather River by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.