Sunday, February 28, 2016

Marin County, California Bridges: State Route 1 (Green Bridge) across Lagunitas Creek

February 2016 (38.06471, -122.80513) Bridge over Lagunitas Creek
The next few blogs will be on the bridges over Lagunitas Creek.

At Point Reyes Station, Highway 1 crosses over Lagunitas Creek on an old pony truss bridge (27 0023). This has been a place to cross the creek since the Coast Miwoks lived in the area. The current bridge includes a 100 ft long steel truss span and two 25 ft long slab approach spans. The bridge was built in 1929, it's a few hundred yards from the San Andreas Fault, and Caltrans is planning to replace it with one of the bridges shown below.
The existing bridge is called the 'Green Bridge' and so the replacements all have green paint on them, at least for the railings. The third and forth alternative are the only ones that don't include piers in the creek, which may make one of them the winner with the various government agencies who will need to approve this project.
The residents of Point Reyes Station also have a say in the bridge replacement, which has evoked strong emotions. A series of meetings have been held so that everyone hcan express there opinion on the project. A temporary bridge will be used while the old bridge is being replaced.
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Marin County, California Bridges: State Route 1 (Green Bridge) across Lagunitas Creek by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Sunday, February 21, 2016

Marin County, California Bridges: Point Bonita Lighthouse Bridge

December 2015 (37.8157, -122.5294) Point Bonita Lighthouse Bridge
I was hoping to photograph the suspension bridge leading to the Point Bonita Lighthouse (at the extreme southwestern end of Marin County) in December. However, the tunnel to the lighthouse was closed and so I had to drive along the coastline to get a clear shot of the bridge. Unfortunately I only had brought a 24 to 120mm lens which limited the amount of detail I could obtain. I returned on Presidents' Day weekend but I had to fight crowds of revelers in order to find a parking space near the bridge and lighthouse.
The current bridge was built by Flatiron Construction Company in 2012 and replaced a bridge built in 1954. The project had a number of challenges. The only access was through a 4 x 6 foot tunnel (see lower right corner of photo above). The bridge was constructed of dense hardwood from the Cameroon (because of its resistance to salt spray). The cliff that supports the bridge was reinforced with steel rods. The project cost $1.9 million and was paid for by the Federal Highway Administration.
The bridge is a replica of the previous structure, a suspension bridge with timber 'A' frame towers supporting a timber deck and with asymmetric suspension cables anchored into the surrounding cliffs. No bridge was originally needed to reach the lighthouse when it was first moved to its current location in 1877. However, the cliffs slowly eroded. The US Coast Guard still maintains and operates the lighthouse horn and beacon.

You can see the towers of the Golden Gate Bridge peaking above the heads of visitors in the photo below.
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Marin County, California Bridges: Point Bonita Lighthouse Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Sunday, February 14, 2016

Marin County, California Bridges: San Anselmo Creek Bridges

January 2016 (37.96889-122.56000) San Anselmo Creek Bridges
Almost unnoticed from the road are several old arch bridges crossing San Anselmo and Corte Madera Creeks in the towns of San Anselmo and Ross. Some of the bridges, like the Sir Francis Drake Bridge (27C0050), have such dense vegetation that it's impossible to see the arch without a machete to clear the brush. The nearby Shady Lane Bridge (27C0078) shown below was designed by John B. Leonard and is on the list of historic places.
Other structures like the Winship Road Bridge (27C0074) shown below are in need of maintenance and must act like a dam during heavy rains.
Modern structures like the Center Avenue Bridge (27C0101) shown below have more headroom for floods and are in better shape. However, this bridge is scheduled to be replaced as part of a flood control project.
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Marin County, California Bridges: San Anselmo Creek Bridges by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Sunday, February 7, 2016

Marin County, California Bridges: Bellum Blvd Bridges

January 2016 (37.9579, -122.5090) Bellum Blvd. Bridges
A complaint that can be made about US bridge engineers is they often place different bridges together without regard to the resulting appearance. In the foreground is a new, single span steel thru truss pedestrian bridge on squat bents/abutments. Right behind it is an old, abandoned, timber trestle railroad bridge. Directly above these smaller bridges are the giant concrete US-101 expressway bridges. No thought was given to how unattractive these bridges look as a whole to people driving by.
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Marin County, California Bridges: Bellum Blvd Bridges by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.