Humboldt County Bridges: Highway 101 Bridge across the Eel River at Rio Dell

September 2013 (40.50967, -124.12001) Eel River Bridge

The Eel River Bridge (04 0016R) was built in 1940 with an unfortunate geometry, structure-type, and design for the site. It was originally a three span Pratt through truss bridge, but log jams during floods caused so much damage that the third truss span (and most of the girder spans) had to be replaced in 1964 (see photo below).

The piers were so vulnerable due to earthquakes that lead-rubber isolation bearings were eventually placed between the piers and bearings (in 1986) to reduce the inertia forces from the heavy truss spans.

Also, the remaining through truss spans were constantly in need of repair due to oversize loads damaging the cross-bracing (see photo below).

This bridge is now 78 years old, but it needed constant work to remain in service.

Monterey County, California Bridges: Bridges Near the Town of Bradley

July 2016 (35.80806, -120.85556) Nacimiento Lake Drive Bridge

I wanted to acknowledge a few bridges that we missed in our survey of Monterey County. The Nacimiento Lake Drive Bridge (44C0009) over the San Antonio River is a single lane Pratt truss bridge (with a steel deck) that was built by the Jones and Laughlin Steel Company in 1921. Note the guides on the deck to keep vehicles from banging into the truss members. Photos of details and modifications to the truss provided by Craig Philpott are on the Bridgehunter Website.

State Highway 101 is carried over a county road on the Jolon Road Bridges (44 0009R/L) in Bradley. The parallel bridges have three span haunched T beam superstructures and were built in 1936.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Plumas County, California Bridges: Port Wine Road Bridges across Slate Creek

November 2015 (39.66161, -120.96432) Port Wine Road Bridges

The Port Wine Road Bridges are two crossings that carry about 50 vehicles a day over Slate Creek. Port Wine Road Bridge #1 (09C0014) is a single span 120 ft long through truss that was built in 1910. Port Wine Road Bridge #2 (09C007) is an 'A' frame supported steel stringer bridge built in 1936. However, it isn't clear how people crossed the creek before the second bridge was built.

The Port Wine Road Bridge #1 is a six panel Pratt truss built by George Brandt 105 years ago. The two center panels have cross members, the second and fifth panels have members sloping down toward the center of the bridge, and the ends are half panels sloping down to far ends of the bridge. The superstructure is only 12 ft wide, with a vertical clearance of only 13.5 ft and is rated in fair condition.

Port Wine Road Bridge #2 is 50 ft long and has sloping legs to support the superstructure at midspan without having to put a pier in the creek. This makes the bridge an unusual hybrid somewhere between a 3 pinned arch and a truss. A problem with this kind of design is that the bridge is rigid (rather than flexible) for longitudinal displacement and the legs are more vulnerable to shear.

The bridges cross Slate Creek on the border between Sierra and Plumas Counties. The creek has a rocky obstruction in the middle that allowed two short bridges (instead of one longer bridge) to be built. When I visited in November of 2015 the creek was only flowing in the deep channel under Port Wine Road Bridge #2 (this was the same as when Craig Philpott visited the site in August 2010).

The name Port Wine came from an abandoned mining town that was formed (but soon abandoned) during the Gold Rush of the 1850s. Since the bridges were built many years later, they may have replaced earlier bridges across Slate Creek. This area (the North Yuba Watershed) has many ghost towns and abandoned mines dotting the landscape. Cemeteries, mine shafts, and building foundations still remain. Today, the town of La Porte is the largest remaining community from that time. It had a population of 10,000 people in the 1880s, a population of 43 in 2000, and a population of 26 in 2010. 

Plumas County, California Bridges: Port Wine Road Bridges across Slate Creek by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Butte County, California Bridges: Poe Powerhouse Bridge across the North Fork of the Feather River

September 2015 (39.7278 Degrees, -121.4684 Degrees) Poe Powerhouse Bridge

Just north of Lake Oroville is the 'Big Bend' and several interesting bridges. Last week we looked at the beautiful Union Pacific North Fork Bridge. Today we're studying the nearby Poe Powerhouse Bridge. I previously mentioned all the dams (and powerhouses) along the North Fork of the Feather River. The only access to some of them are on dilapidated roads and bridges. The Poe Powerhouse is typical. You drive down a gravel road (Bardees Bar Road) full of switchbacks to the river and across an old truss bridge with weight restrictions that takes you to the powerhouse. The Poe Powerhouse consists of transformers and a 890 ft long penstock with a drop of 477 ft that produces 120 megawatts of electricity. The bridge and the powerhouse are owned by Pacific Gas and Power.

The Poe Powerhouse Bridge is 335 ft long with a single, 178 ft long deck truss span across the North Fork of the Feather River. The substructure consists of tapered concrete pier walls. The superstructure supports an 18 ft wide reinforced concrete deck that carries an unnamed road. The road is used by the powerhouse employees and by the occasional kayaker, although the many dams across the river must make kayaking a hassle.

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

San Joaquin County, California Bridges: Manthey Road Pedestrian Bridge across the San Joaquin River

April 2014 (37.78593, -121.30706) Manthey Road Pedestrian Bridge

Because the sidewalk on the adjacent Manthey Road Bridge is deteriorated (and because it's next to a park) the county built a pedestrian bridge at this site (see photo above). This bridge is so new that I couldn't find any information about it. However, we can see that it's a four span Pratt pony truss on single column hammerhead bents with pipe shear keys to keep the spans from being knocked off during earthquakes. In Google earth, I measured the bridge to be about 650 ft long across the San Joaquin River.

San Joaquin County, California Bridges: Manthey Road Pedestrian Bridge across the San Joaquin River by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Contra Costa County, California Bridges: Iron Horse Trail Bridge across Walnut Creek

February 2014 (37.90560 Degrees, -122.05736 Degrees) Walnut Creek Bridge 

The Iron Horse Trail has a number of older bridges from when the trail was a railroad line. Today's bridge is a four panel Pratt truss with diagonal members sloping towards the center in tension. The bridge crosses over Walnut Creek, which is a concrete-lined channel covered with warning signs due to the danger of flash floods and drownings.

This bridge was built in 1929 and has the date stamped on the portal frames at the ends of the bridge. It's 102 ft long, 18 ft wide, and made up of wide flange compression members and laced tension members. The Ygnacio Valley Road POC is just north of the Walnut Creek Bridge and a little to the side to allow people to continue on or off the trail as shown in the photo below.

Contra Costa County, California Bridges: Iron Horse Trail Bridge across Walnut Creek by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.