Next in Line for Seismic Retrofits:
Dumbarton and Antioch Bridges
Dumbarton Bridge (top); Antioch Bridge (bottom).
Photos: John Huseby, Caltrans
The Dumbarton and Antioch bridges may not have the iconic
presence, name recognition or heavy traffic volumes of the
San Francisco-Oakland Bay Bridge, but they are
important links in the regional transportation network nonetheless.
And now MTC’s
Bay Area Toll Authority (BATA) is working
with Caltrans to bring these spans up to
current earthquake safety standards. BATA is also developing
a plan to raise tolls on the region’s state-owned bridges
to cover the $750 million cost of the retrofits as well as
to compensate for declining toll revenues and escalating construction
“These two bridges were built before the Northridge
and Loma Prieta earthquakes,” said Andrew Fremier, the
MTC deputy executive director who oversees BATA’s operations. “We’ve
learned a lot since then.”
Opened in 1982 and 1978 respectively,
the Dumbarton and Antioch bridges were too young to merit a
seismic review back in the 1990s when Caltrans initially mapped
out a bridge seismic retrofit program. That earlier effort
targeted five of the region’s
seven state-owned toll bridges and is now largely complete,
with the exception of the new East Span of the Bay Bridge,
which is still under construction.
The 1.6-mile long Dumbarton
Bridge carries an average of 60,000 vehicles a day across the
southern end of the Bay. The retrofit strategy calls for modifying
deck joints and reinforcing columns on the approaches. Along
the bridge’s central hump, new
isolation bearings will be placed between the superstructure
and the piers to reduce shaking movements transferred to the
deck in the event of an earthquake.
The retrofit approach is
similar for the Antioch Bridge, which stretches 1.8 miles across
the San Joaquin River and transports an average of 15,000 vehicles
a day between Eastern Contra Costa County and Sacramento County.
Its tall columns also will require cross-bracing.
work is scheduled to begin by April 2010 and be completed in
2012 on the Antioch Bridge, and 2013 on the Dumbarton Bridge.
Toll Increases Ahead
MTC’s Bay Area Toll Authority has been formulating scenarios
for raising the current toll scheme for the region’s
state-owned bridges, under which cars and light trucks pay
$4, trucks pay according to the number of axles, and carpools
and vanpools traverse for free during commute hours. View
and comment on current proposals.