A recent increase in blasts originating at the Lehigh Southwest Cement Co. quarry near Los Altos Hills is causing a bit of a shakeup. Unsure of whether the mining blasts could have a larger impact on seismic activity, the Los Altos Hills City Council plans to ask the Santa Clara County Board of Supervisors to conduct a study to assess the situation.
“We have a combination going on at Lehigh with both blasting and blasting on fault lines,” said Los Altos Hills resident Bill Almon, explaining why he requested that councilmembers consider action.
Observing an increase in blasts from the 1,288-acre quarry, Almon gathered seismic data from the U.S. Geological Survey that recorded 23 earthquakes and 66 blasts ranging from 0.64 to 2.95 on the Richter scale in 2013. Concerned that some of the blasts could possibly induce or contribute to seismic activity along the Berrocal Fault, which lies below the plant, or the nearby Altamont, Monta Vista or San Andreas faults, Almon contacted the State Mining and Geology Board and the Santa Clara County Board of Supervisors urging further investigation – to no avail.
“What we would like would be for the knowledgeable agencies to look into the problem and either say there is a problem or not,” Almon said. “From a common-sense point of view, it seems like you shouldn’t (be blasting) on a fault line.”
Councilmembers expressed interest in the issue and voted unanimously to engage their colleagues at the county and state levels.
“The only thing we can do is send a letter to the board of supervisors requesting a study and more in-depth information,” said Councilman Gary Waldeck. “(The U.S. Geological Survey and county supervisors are) taking the wait-and-see attitude, and I’d like to see more alacrity at this point.”