The lore of Lawson Adit

Mining students line up in front of Lawson Adit, named for Professor Andrew Lawson, who used the 900-foot tunnel to demonstrate mining techniques. Located on the east side of the Hearst Memorial Mining Building, the adit was open between 1919 and 1930 and extended all the way to the Hayward Fault. It was eventually closed for safety reasons. Photo courtesy of University Archives, UC Berkeley

19 September 2002 |

John Pruynes, 90, came back to campus recently to admire the Hearst Mining Building’s new seismic foundation of rubber and steel isolators, and to peek inside the fenced-off entrance to Lawson Adit, a mining shaft he helped blast more than 60 years ago.

“This is one of the few mines that was deliberately drilled into a fault,” says the 1939 Cal graduate in mining and metallurgy. “The first 200 feet were experimental tunnels, but we drove that mine on to about 900 feet, right into the Hayward Fault zone.”

Lawson Adit [add-it], a horizontal mining shaft on the east side of the Hearst Memorial Mining Building, is as much a part of Berkeley’s mining history as the grand old building itself. Named for Professor Andrew Lawson, it was used between 1919 and 1930 to offer mining and metallurgy students hands-on practice in their trade. To educate future miners, the adit began as an experiment in teaching the art of dynamiting, “mucking,” and shoveling rock and gravel in search of gold, iron, copper, and other valuable minerals.

“It was always wet as heck down there, from the water table, and we couldn’t keep the timbers up, because the ground was always so wet and clayish, and moving around,” Pruynes says. “But the pay was out of this world — a dollar an hour, which was far better than the standard pay then.”

Pruynes worked the graveyard shift at Lawson Adit with another mining student and a union boss. “Dean Frank Probert had several gangs of students working on it in three shifts,” he recalls, “so we were digging farther east into the hills all the time. After we blasted the tunnel with dynamite, we’d have to load up the mining cars and roll them out. But I knew the routine because I’d already worked in a mine.”

With old-fashioned oxygen tanks strapped to their backs and wooden boxes of dynamite sticks in their arms, the mining students could be seen lining up between the Hearst building and the entrance to the mining shaft every day to begin another experiment in tunneling.

By 1939, seismologist George Louderback had found a new purpose for the mine: it could be used to study the Hayward Fault zone, lying just 800 feet away, to determine the safety of building a new women’s dormitory. He began recruiting job-seeking students to help lengthen the tunnel.

The shaft indeed allowed engineers to identify the precise locations of multiple fractures of the fault. But the closer the tunnel came to the fault, the softer the ground became, Pruynes recalls. “We couldn’t keep the timbers up after a while, the ground was shifting so much.”

Some parts of the mine began to collapse and were filled in with concrete, he says. “Later, they even wanted to continue the tunneling on the other side of Gayley Road, but they decided they couldn’t do that because it wasn’t safe.”

However, Louderback’s investigation of the Hayward Fault from underground proved beneficial, persuading him to recommend that Berkeley move the site of what is now Stern Hall 50 feet to the east, to clear the fault.

Pruynes, who says he is glad to have earned his degree from a school that was strong in mining, found lucrative work in several local mines after graduation, until the industry died down with the coming of World War II. He says he has lost touch with all of his classmates but, because he lives in nearby El Cerrito, visits campus occasionally for “mining events,” such as the completion last January of the Hearst building’s new seismic foundation.

“That was really something to see,” he says of the new state-of-the-art base-isolation system.