PLEASANT HILL -- Pleasant Hill is the first stop on a roving exhibition of photographs depicting rare excavation views of the Caldecott Tunnel's $402 million fourth bore project.

"We can't bring the public to the project," said Ivy Morrison, Caltrans public information officer, "but we can take the project to the public."

The Caldecott Tunnel fourth bore project is a partnership of the Federal Highway Administration, the Metropolitan Transportation Commission, the Contra Costa Transportation Authority, and the Alameda County Transportation Commission to build the two-lane fourth bore north of the existing three tunnels.

The exhibit left the Metropolitan Transportation Commission headquarters in Oakland where it's been on display and headed to Pleasant Hill at the beginning of September and will remain at City Hall until the end of the month when it will travel to another city requesting the display, said Morrison.

The photographs present rare views of work inside the tunnel beginning in August 2010, said Martin Nelis, Pleasant Hill public information officer in a news release.

"(It) also includes portraits of some of the project's many unsung heroes," Nelis said. "One photo depicts the "brass board" -- a vestige of traditional mining projects."


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The brass board or identification tag was used when miners entered and exited a mine. Each miner had their own tags made of brass and hung them on sign-in or sign-out boards, according to mining history thus enabling rescue crews to know who was in the mine.

Today, most miners are electronically tracked using a system of radio waves to communicate identification information between a tag and a reader.

The exhibition pictures taken by Karl Nielson of the MTC and John Huseby of Caltrans show the primary portion of excavation, including a colossal custom-made 130-ton drill and a now-historic photo of the breakthrough from the Contra Costa County side of the hill where digging began to the Alameda County side.

"It shows there is light at the end of the tunnel," Morrison joked about the project that began with the passage of Regional Measure 2 in 2004 and Contra Costa Measure J, a half-cent sales tax and the largest contributor to the project.

Proposition 1B passed in 2006 added to the coffers. The financial crisis of 2008-2009 put it in jeopardy, but federal and state leaders were able to get federal stimulus money.

There are photos of installing the final cast-in-place concrete lining -- which resembles a large yellow raincoat -- used to prevent water seepage and topped with a cage of double rebar to resist earthquakes. There were a series of 69 concrete pours moving from west to east, said Morrison.

Morrison said construction of the fourth bore is using traditional and modern technology to ensure the best outcome. The modern engineering will allow this bore, situated 0.9 miles from the Hayward Fault, to withstand a 7.4 earthquake.

When the fourth bore comes on line in 2013, there will no longer be a need to reverse direction of the center bore. It is also expected to relieve the backup and accidents created when four lanes must merge to two, Morrison said.

Although there is no photo, the new bore will have what is called an invert eight feet beneath the bottom layer of the tunnel to address ground swell, the uneven expansion of earth caused by the absorption of water. It is noticed in the other bores by a rollercoaster effect, said Morrison.

She said included in the exhibit is a rendering of what the new bore will look like when finished, with two 12-foot-wide lanes and a 10-foot-wide shoulder.

light at end of tunnel
What: Roving photo exhibit of the Caldecott Tunnel Fourth Bore project
Where: Pleasant Hill City Hall main lobby, 100 Gregory Lane
When: During September; 8:30 a.m.-5 p.m. Monday-Wednesday; 8:30 a.m.-6 p.m. Thursday; 8:30 a.m.-5 p.m. Friday
Information: The next stop on the roving tour is not set, but any city interested in hosting the exhibit can call Ivy Morrison, Caltrans public information officer, at 510-333-4742.