ORINDA (CBS SF) – The bottlenecks and backups faced by motorists heading toward the Caldecott Tunnel will be a thing of the past as soon as Saturday morning with the opening of the tunnel’s brand new fourth bore, a Caltrans director said Friday.

Caltrans director Malcolm Dougherty made the announcement at a ribbon-cutting ceremony Friday afternoon for the fourth bore of the state Highway 24 tunnel connecting Oakland and Orinda.

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Dougherty did not provide a specific time for when the new tunnel would open.

State and federal transportation officials as well as local city and county leaders were on hand Friday afternoon to celebrate the two-lane bore, which is expected to unclog off-peak traffic heading toward the tunnel.

“With the completion of the fourth tunnel, Bay Area residents will get to where they’re going more efficiently and safely through this historically congested area,” said U.S. Transportation Secretary Anthony Foxx.

The new bore will create a smoother flow of traffic for the more than 160,000 people who travel through the Caldecott Tunnel each day by keeping four lanes of traffic open in each direction at all times, Caltrans officials said.

The additional tunnel will allow Caltrans to end its 50-year-old practice of manually reversing the flow of traffic twice per day using the middle bore.

Drivers heading in off-peak directions leading up to the tunnel, or east on weekday mornings and west during the evening rush hour, could shave an average of five minutes from their morning commute cut an average of 7 to 10 minutes from the westbound evening return trip, according to Caltrans.

Weekend travelers heading in off-peak directions will also have more predictable traffic approaching the tunnel thanks to the additional two lanes, Caltrans officials said.

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“It’s not only convenient for those who have to travel through the tunnel, but also very good for our air quality,” said state Assemblywoman Nancy Skinner, one of many legislators who spoke at today’s ribbon-cutting ceremony at the westbound entrance to the fourth bore.

Skinner noted that the reduction in idling cars, a major source of air pollution, would be a boon for the area’s air quality.

The fourth bore is also outfitted with a number of safety upgrades, including wide shoulders, a series of powerful jet fans to blow smoke out of the tunnel in the event of a car mishap or fire and cross-passages connecting the third and fourth bores that serve as emergency exits.

The $417 million project was funded mostly by federal stimulus funding as well as through revenue from Measure J, a half-cent sales tax approved by Contra Costa County voters in 2004. Funding also came from Bay Area bridge toll revenue, and proposition 1B, a 2006 voter-approved state transportation bond.

The project received one of the greatest shares of funding under the American Recovery and Reinvestment Act and created more than 5,000 jobs, according to Caltrans.

“In the depths of the recession, (President Barack Obama) had the presence of mind to remind our country that great things are still worth doing and investments in our infrastructure can help us lead our economic growth,” Foxx told the audience at Friday’s ribbon cutting festivities.

U.S. Rep. George Miller, D-Martinez, lauded the partnership among transportation agencies as well as the state, federal and county governments, city leaders, residents and construction crews who helped make the fourth bore a reality.

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