Butte County, California Bridges: Old Bidwell Bar Bridge

August 2015 (39.53747 Degrees, -121.45417 Degrees) Old Bidwell Bar Bridge

The first suspension bridge (ropes hung above an obstacle) predates recorded history. The first iron suspension bridge was built (appropriately) by the Tibetan bridge engineer Thangtong Gyalpo in the 15th century. The first US suspension bridge was the Jacob's Creek Bridge in Pennsylvania built in 1801. The first California suspension bridge was the Bidwell Bar Bridge built across the Middle Fork of the Feather River in 1855 (see photo below).

Bidwell Bar was a gold rush town that was founded after John Bidwell discovered gold there in 1848. The town experienced a rapid boom and an equally rapid bust until the bridge was just about all that remained. When the Oroville Dam was built in 1965, the town was submerged and the bridge (along with a historic orange tree and toll building) was moved to its present location (Kelly Ridge Park) in a state boat launch facility about a mile west of its original location.

When I drove to the park entrance in August, the ranger told me the bridge was inaccessible because the road had been blocked by fencing surrounding houseboats in dry dock. I was irritated that after all of the trouble to move the bridge the park had closed it to the public. However, the bridge turned out to be readily accessible to anyone willing to hike up a hill (although photos suggest the bridge was less accessible before the drought). Another thing that bothered me is that timber piles now supported the bridge rather than having the suspension cables carry the 240 ft long span.

The Bidwell Bar Bridge was fabricated in Troy, New York and shipped around the southern tip of Chile to California. The towers are atop stone abutments and composed of four iron pipes stamped with 'Starbuck's Metal Works of Troy, NY. The pipes at each tower form a pyramid with saddles on the top that support two suspension cables. Regularly spaced hangers support timber floor beams that carry the deck. The bridge is a California Historical Landmark and a Historical Civil Engineering Landmark.

Butte County, California Bridges: Old Bidwell Bar Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

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 (carrying Lumpkin Road) 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.