As of December 17, 2012, The Dumbarton Bridge Retrofit is 95% Complete
Project SummaryThe Dumbarton Bridge (State Route 84) has served the Bay Area—especially the Peninsula and South Bay communities—for nearly three decades. During that time, the realities of living in an earthquake prone area and advances in seismic safety standards have warranted retrofits of all toll bridges throughout the region. The Dumbarton Bridge Seismic Retrofit is part of the San Francisco Bay Area Toll Bridge Seismic Retrofit Program. The project began in 2010; upon its completion in 2013, the Dumbarton Bridge will meet all current seismic and safety design standards.
In the November 2012 edition of Roads and Bridges, Managing Editor Allen Zeyher published an article about the Dumbarton Bridge Retrofit and the cutting-edge seismic technology being used on the bridge. Click here to read the article.
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Dumbarton Bridge Facts
- Structure: Steel box girder and pre-stressed concrete approach and departure structures
- Length: 1.6 miles
- Vertical Clearance: 85 feet
- Channel span: 340 feet
- Capacity: Three lanes in each direction with a dedicated bike/pedestrian path on the south side
- Traffic: 61,000 vehicles per day
Implementing nighttime lane closures have allowed the contractor to access the interior and underneath of the bridge deck to complete work while traffic continues to cross the Bridge. In addition, two weekend-long closures were required this year for replacement of the two largest expansion joints.
Weeknights Monday p.m. – Friday a.m.
- • Overnight lane closures may begin as early as 7:00 p.m. and will vary between the three lanes; a maximum of two lanes will be closed at a time.
- • All westbound lanes reopen by 5:00 a.m. the following morning.
- • Lane 1 will remain open.
- • Lane 2 will be closed overnight and may be closed as early as 8:00 p.m.
- • Lane 3 will be closed overnight and may be closed as early as 8:00 p.m.
- • All eastbound lanes reopen by 6:00 a.m. the following morning.
Weekends Friday p.m. – Sunday a.m.
- • Overnight lane closures may begin as early as 4:00 p.m. and will vary between the three lanes; a maximum of two lanes will be closed at a time.
- • All westbound lanes reopen by noon the following morning.
- • Lane 1 will remain open.
- • Lane 2 will be closed overnight and may be closed as early as 6:00 p.m.
- • Lane 3 will be closed overnight and may be closed as early as 6:00 p.m.
- • All eastbound lanes reopen by 1:00 p.m. the following day.
The Dumbarton Bridge (State Route 84) is the southernmost of the highway bridges that crosses the San Francisco Bay. After serving the Bay Area for nearly three decades, the Dumbarton Bridge is undergoing a seismic retrofit to comply with all current seismic and safety design standards.
While the Dumbarton Bridge has closed twice, there are still various construction activities that must be completed in order to make the bridge resilient in the case of seismic activity. Almost 100 bearings will be installed along the main portion of the bridge to allow the bridge to shift during a seismic event. This work, along with all other retrofit activities, will be completed in 2013.
SEISMIC JOINT REPLACEMENT
In 2012, the Dumbarton Bridge closed entirely to traffic two times; once, over Memorial Day Weekend, and again over Labor Day Weekend. Two full bridge closures were necessary in order for crews to replace the existing expansion joints on the eastern and western sides of the bridge, at Piers 31 and 16, with state-of-the-art seismic joints.
Crews are currently working from west to east, installing bearings under the bridge deck that allow the bridge deck to move independently of the foundations during a seismic event. Six bearings must be installed at each pier along the main channel crossing, from piers 16 to 31, for a total of 96 bearings. As of October 16, 2012, 6 piers have been completed.
How do I find out about closures, detours and traffic delays caused by this seismic safety work?
For current traffic conditions and driving times during a closure, please call 511 or visit 511.org.
The bridge is within the Don Edwards San Francisco Bay National Wildlife Refuge and traverses a particularly fragile slice of the Bay Area’s ecosystem, including open bay, a salt marsh, a migratory bird flyway and mud flats that are home to both native plants and species.
The project is also within the San Francisco Bay Watershed to the north and the Coyote Watershed to the south. Special care is taken during construction to avoid disturbing the ecosystem’s delicate balance. A Stormwater Pollution Prevention Plan and a variety of environmental mitigation measures are in place during construction to ensure that the retrofit work does not have an adverse impact on the environment.
Installation of a new pumping plant, a sheet pile wall and a drainage pipe on the southwest side of the bridge are part of the current project. Once completed, this barrier and underground pumping system will protect the surrounding marshlands by preventing high tides from inundating the roadway and washing material into the adjacent tidal marsh.
The Dumbarton Bridge is the southernmost of the highway bridges that cross the San Francisco Bay and was the first bridge to carry vehicular traffic across the Bay. The original Dumbarton Bridge was a drawbridge located south of the existing Dumbarton Bridge that was built by private developers in 1927. When the bridge first opened, the toll was $.40 in each direction with additional charges per passenger and for animals. The State purchased the Dumbarton Bridge in 1951 for $2.26 million.
The bridge was rebuilt by Caltrans in 1982 for $70 million due to safety and traffic congestion issues. When the new bridge opened to traffic the toll was $.75 and was only levied in one direction.
After the new bridge was built, the center drawbridge portion of the original bridge was removed, leaving the two ends which became fishing piers, each extending approximately 2,000 feet into the Bay. The western pier which is known as the “Ravenswood Pier” has been closed for more than 20 years. Ravenswood Pier will be removed as part of the current seismic retrofit project. The Dumbarton Pier is located on the eastern side of the bridge and is still a popular fishing location that is managed by the U. S. Department of Fish and Wildlife Service.
An abandoned train bridge that was closed in 1982 is located south of the Dumbarton Bridge. This abandoned train bridge has been identified in regional transportation plans as a potential location for future commuter rail service.