Historic mining tunnels in Mt. Diablo foothills… - The Mercury News

ANTIOCH  — Coal miners from a booming early Bay Area industry lay on their sides in 3-foot-tall tunnels to scrape and hack out soft black ore with pickaxes deep inside the Mount Diablo foothills.

Explosions, cave-ins and poisonous gases killed many of them, but five coal-mining towns with some 3,000 people flourished in the 1860s and 1870s in what was then the population center of Contra Costa County.

They are ghost towns now but not forgotten.

A $2.2 million expansion and upgrade of the Bay Area’s only underground mining museum at the Black Diamond Mines Regional Preserve aims to show more vividly the perils and rewards faced by miners who delivered fuel to power early development of San Francisco, Oakland and Sacramento.

When the six-month project is finished this summer, visitors on underground mine tours will be able to walk nearly twice as far — up to 2,200 feet — and for the first time on a continuous path through the mines, instead of having to retrace steps on a dead-end route.

Also for the first time, a new metal staircase with about 120 steps will enable visitors to travel down from one mine level to a deeper one.

At the bottom, a coal vein made from marsh plants that died 50 million years ago on the edge of an inland sea will glisten in the mine lights.

“The Big Steps project will give visitors a deeper appreciation of the mines,” said Pat Dedmon, the acting mining supervisor for the East Bay Regional Park District, which manages the site. “I think the public will be excited at being able to go places where they couldn’t go before.”

The project was approved earlier this month by the East Bay Regional Park District board.

Some 20,000 visitors a year take the mine tours, which are $5 and last for  90 minutes. The mine tours will continue during the upgrade, but the extent of the tours may be limited to avoid conflicts with construction, officials said..

The appeal of visiting a mine was apparent last week when some elementary school students visited with eyes wide open as they walked in a tunnel in the Hazel Atlas sand mines. The mines operated from the 1920s through 1945 in shafts near the coal mines, which are considered too dangerous and unstable for public traffic.

Tour guide Kevin Dixon asked the students wearing hardhats to be quiet, and an eerie blanket of silence enveloped the mountain rock vault with no trace of twittering birds, leaves rustling on trees, or cars revving engines and honking.

“It feels so peaceful and serene,” Dixon said.

Peaceful as they seem, the mines are an unending chore to keep safe. Park crews jostle loose rock on walls and ceilings, and monitor for poisonous gases and cave-ins. Crews wet down sandy floors if necessary to reduce dust for park visitors. The public mine areas in the park were closed for nearly a decade after the 1989 Loma Prieta earthquake caused a rock slide.

“We want visitors to have an immersion experience in what it’s like to be in the mines,” Dedmon said, “but it must be safe.”

To ensure the new visitor areas are safe, crews will reinforce walls and ceilings with long rock bolts and spray a wet mortar called Shotcrete on the tunnel ceilings to prevent sandstone rocks from tumbling down on visitors’ heads.

Visitors to the expanded tour areas also will get more glimpses of the Bay Area’s geological past from ancient imprints on the mine walls. Left behind are burrows formed by crabs and worms 50 million years ago when the region was flat and covered by marshes around a big inland sea. Geological forces from colliding earth plates pushed up Mount Diablo and its layers of coal.

“Here is the burrow of a crab from 50 million years ago where it pushed out sand,” Dedmon said as he stopped to examine a wall. “This is a great lab that geology researchers and students like to visit.”

In the visitor areas, the park district will expand displays and signs to illustrate the tough life of miners.

Because the veins of the soft lignite coal at Black Diamond were about 3 feet thick, the tunnels to remove the ore were only about 3 feet high — not big enough for an adult to stand up in.

Miners toiled 12 hours a day, six days a week using drills and picks to knock loose the coal. Young boys called nobbers also worked in the mines, pushing the coal from the miners onto metal plates greased with whale oil that were used to carry out the coal. After working in the mines by day, the boys went to school at night.

Planned new exhibits using mannequins will simulate a coal miner at work, Dedmon said.

“It was a rough life, but it was an opportunity for many newcomers or gold miners,” said Eddie Willis, a tour guide at the mines.

Coal mining in the Black Diamond area began in the 1850s, peaked in the 1860s and 1870s, and died out by 1900 because of the discovery of higher-grade coal in Washington.

When the miners departed the Black Diamond area, they left behind 200 miles of coal mine tunnels and about eight miles of sand mines. Less than half a mile of the sand mines are open to the public.

Many of the buildings in the Contra Costa mining towns were salvaged for scrap and some were taken apart board by board and then put back together for homes in Antioch.