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Tunnel Vision

Inside the digging of the Caldecott’s Fourth Tunnel


Photography By Karl Nielsen

Anyone involved with digging the fourth bore of the Caldecott Tunnel—from the on-site miners to regional transportation experts—will tell you it’s a dangerous undertaking. The tunnel is classified as “gassy,” which means combustible gases can be released from the earth during excavation. A spark, even an electrostatic spark from something as small as a battery-operated watch, could turn naturally occurring hydrocarbons in the tunnel into a deadly fireball.

Still, miners coming from all over the country enter the tunnel night and day to work 10- to 14-hour shifts, six days a week. As they enter, they are required by law to uphold a long-standing mining tradition called “brassing in and out.” Each miner at the fourth bore has two identically numbered brass tags—one he carries with him into the tunnel, and the other he hangs on the tag board to show he is inside.

The People: West Side


“The first indicator for rescuers who enter a tunnel after an event is the brass tags on the board,” says Ivan Ramirez, senior engineer for Caltrans. “Brass has a high melting point. So should an emergency like a strong fire occur, the brass tag would help identify the remains.”

Because of the high degree of danger, access to the worksite is strictly limited. One of those allowed access who is not directly involved with grinding through the hills separating Contra Costa from Alameda counties is photographer Karl Nielsen. The Metropolitan Transportation Commission hired the Berkeley resident to document the massive project for historical purposes because of his experience photographing mega construction projects. Nielsen’s photos provide a rare view of the cavernous, mud-drenched space, where two teams of miners—on the Orinda side tunneling east to west and on the Berkeley side heading west to east—are digging.


The tunneling progresses at a rate of about one to three meters per day, and the new bore will have taken four years to complete by its projected opening in late 2013. The benefit to commuters will be four lanes dedicated to traffic in each direction through the Caldecott, alleviating the current bottlenecks. And the fourth bore is likely to become the favored tunnel: It’s much wider than the other three bores, with the addition of a 10-foot-wide shoulder, and it has twice the headroom. Compared to the first two bores (built in the late 1930s), a drive through the new, northernmost tunnel will feel like moving from a condo to a mansion.

Funding for the fourth bore has been pieced together from several sources.
Contra Costa County residents kicked in 30 percent of the tunnel’s $390 million price
tag by voting for a half-cent sales tax, Measure J; and state and regional programs also provided substantial funding. The infusion of $180 million in federal stimulus money, at the time the largest Recovery Act allocation in the country, enabled the digging to start.

The cost in terms of exposure to danger for the miners is real, whether it’s the potential for asphyxiating gases, a fire, a cave-in, or an influx of excessive water. Officially, crews get together at the start of each shift for a safety meeting to review the constantly changing conditions. On a more personal level, according to Nielsen, the miners support each other.

“Over the past year, I’ve seen the miners really bond,” he says. “The crews are tight. They have each other’s backs.”




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