Caldecott Tunnel

Digging the Caldecott Tunnel's Fourth Bore

August 2010
Despite gray skies, faces were aglow at a ceremony on August 9, 2010, marking the start of tunneling for the fourth bore through the Caldecott Tunnel. As workers in hard hats waited nearby to begin work, a parade of government officials commemorated the $420 million project that will relieve traffic congestion on State Route 24 by providing four permanent lanes through the tunnel in each direction. When completed in late 2013, the new fourth bore will ease the reverse commute for motorists (eastbound toward Contra Costa County in the a.m. and westbound toward Alameda County in the p.m.), reduce weekend backups in either direction, and end Caltrans’ twice daily job of switching the direction of traffic in the middle bore to adjust traffic flow.

As one speaker at the ceremony noted, the tunnel project is “a big deal.” It is a showcase for the most advanced tunnel engineering and construction methods; it is the second largest federal “stimulus” project in the U.S; and it proves the successful partnership of county, regional, state and federal agencies to finance and move a major project forward.

The idea of a fourth bore in the Caldecott Tunnel dates back at least to 1998, some 60 years after the Caldecott Tunnel first opened (with two bores) and 34 years after the third tunnel bore opened in 1964. In the late 1990s, Contra Costa County residents and their local and state elected officials identified traffic backups at the tunnel as the number one transportation issue in the county that needed to be studied and resolved. In1998, MTC responded to public requests by working with the Alameda County Congestion Management Agency (ACCMA), the Contra Costa Transportation Authority (CCTA) and Caltrans to conduct a two-year study of options to relieve traffic backups at the Caldecott. The study concluded that adding a fourth, two-lane bore would allow 1,600 additional reverse commuters on weekdays to travel through the tunnel and eliminate the 12-minute backup projected for reverse-commute and weekend traffic by 2020.

Next came the challenge of funding the costly project. Contra Costa County residents — early supporters of the project —started the ball rolling in 2004 by passing Measure J to extend their county half-cent sales tax. Measure J leveraged $123 million, nearly 30 percent of the total cost of the project. Also in 2004, Bay Area voters approved Regional Measure (RM) 2, raising bridge tolls by $1 to fund congestion relief projects. MTC subsequently set aside $50 million in RM 2 funds for the tunnel project. In 2006, state voters approved Proposition 1B, allowing the state to issue bonds for large-scale construction projects. But the 2008-09 financial crisis doomed the bond market and threatened to delay the tunnel project indefinitely.

Hopes revived in 2009 when Congress passed the American Recovery and Reinvestment Act (ARRA), providing federal “stimulus” funds for job-creating infrastructure projects. Since the new bore was already invested with nearly half of its $400 million construction funds, it qualified for stimulus moneys as a “shovel-ready” project. MTC allocated the total $105 million in regional ARRA funds to the tunnel project, and the state contributed $92.7 million in ARRA funds. This combined total of $197.5 million in federal dollars put the project over the top and made construction a go.

The project sponsors — Caltrans, the Contra Costa Transportation Authorty (CCMA) and the Alameda County Congestion Management Agency (ACCMA) — wasted no time in starting construction. The entire project consists of four separate jobs. The tunnel project, by far the largest, was awarded to Tutor-Saliba Corp., and construction began February 2010. Two smaller projects will facilitate traffic movement in the area, and another project will landscape the staging areas after construction is complete.

The tunnel project began with building walls: huge portal walls that will frame the east and west entrances, retaining walls to hold back the hillside, and a $3.5 million, 30-foot high temporary sound wall to protect apartments just west of the tunnel from construction noise and dust.

The portal walls were completed in July, and actual excavation of the five-eighths-mile-long bore began from the Orinda side on August 9. For this job, a giant, $5.2 million, 130-ton roadheader machine with teeth that can cut through solid rock was imported from Germany. The roadheader will excavate more than half the tunnel distance, meeting a smaller roadheader machine tunneling in from the west side.

While tunneling techniques and equipment constructing the fourth bore are light-years ahead of the timber-supported Broadway Tunnel that was built 200 feet above the current Caldecott in 1903, the basic need between then and now still exists: to connect Contra Costa and Alameda counties and shorten travel time between these two vital parts of the Bay Area.

Scheduled for completion in late 2013, the new bore is also repeating another historical moment in time. When the first two bores of the current Caldecott Tunnel opened in 1937, the nation was in the midst of the Great Depression. It was a time when the federal government stepped in to finance major infrastructure projects, putting Americans back to work and helping to pull the U.S. out of financial straits. One of these projects was the Caldecott Tunnel, and another was the mighty San Francisco-Oakland Bay Bridge, which opened in 1939.

Now, some seven decades later, the U.S. is mired in a lingering recession with high unemployment, and once again, government-sponsored infrastructure projects are aiding the recovery. And once again, major Bay Area transportation projects are generating thousands of jobs: besides the fourth bore of the Caldecott Tunnel, the roster includes the new East Span of the Bay Bridge, the Transbay Transit Center in San Francisco and the reconstruction of Doyle Drive through the Presidio in San Francisco. Scheduled for completion over the next several years, these projects will improve regional transportation for years to come.
– Marj Blackwell