Making Up Watsonville's Bedrock - Graniterock a Mainstay for 114 Years

Posted by Reposted from another publication on Mar 18, 2015

By Todd Guild of the Register-Pajaronian 

The siren warning that a blast was imminent at Graniterock’s A.R. Wilson Quarry Tuesday came two minutes before 25,000 pounds of explosive would hammer loose a landslide of rocks and boulders. When the time came, electronic timers ignited 74 explosive charges, sending a massive cloud of stone and dirt into the air. This was followed by the roar and rumble as the rock tumbled into the quarry. 

Far from the dramatic explosions for which Hollywood is famous, this controlled blast put more than 50,000 tons of quality granite precisely where the company’s engineers wanted it. Jeremy Hunzie, who leads a team tasked with removing dirt and other debris from the granite so it can be mined, called the event a “boring blast.” The remark was far from disparaging. “We want our job to be boring,” he said, referring to the company’s strict adherence to safety standards. Indeed, safety messages are emblazoned onto trucks and other places through-out the company.

Next, two massive bulldozers took over, each capable of pushing 70 tons. Their mission was to move the pile of car-sized boulders and make them accessible to the night crew. Using other earth-moving equipment, that team would scoop the boulders into a house-sized crusher, reducing them to soccer-ball sized rocks that would be transported via a mile long conveyor belt to a secondary processing station. There, crushing machines would further reduce the rocks into a variety of sizes from superfine sand to one-and-a half-inch gravel, all of which has different uses in the construction industry.

Airport runways, for example, must be able to support the weight of airliners and need gravel mixes with larger diameters. Driveways for homes, on the other hand, need smaller-sized gravel. The base rock that goes under concrete slabs, furthermore, must be formulated to easily compact and be extremely strong. Each of those requires a different mix of gravel size and formulation. 

The 800-acre A.R. Wilson Quarry in Aromas is fed by a mass of granite that formed more than 200 million years ago, and will allow Graniterock to provide granite products to its local customers for many years to come. Unlike the solid, towering granite monoliths of Yosemite National Park, however, this granite sits atop the San Andreas Fault, which for eons has pre-fractured the stone and made it easier to mine. But throughout the history of the quarry, the weight of the granite has made it incredibly difficult to mine, from the time the company was founded in 1900 by Arthur Roberts Wilson and Warren Porter at a time when men with picks and shovels worked alongside steam engines to break rock at A.R. Wilson Quarry.

Even after the company has automated most of the mining processes, shipping the final product still poses a financial challenge to customers. This, marketing services manager Keith Severson said, called for an innovative solution. Because trucking is notoriously expensive -- $90 per hour -- the company developed “Granite Express,” an innovative way to load its product onto waiting trucks, any time of day. “Every minute adds money to the final product,” Severson said. Truckers drive under a loading machine, and guided by radio frequency, the automated system loads the exact size and shape of rock they need. This has reduced loading time by half, Severson said. “It’s like a 24/7 ATM for rock,” he said. Nearby, another machine is capable of loading a 100-ton railcar in three minutes, Severson said.

needs, the company has an onsite research and technical services division that tests for gravel size and for strength of its stone projects. Severson said. s products are shipped as far as the Marshall Islands to make satellite launching pads, approximately 99 percent stays local and is shipped out to all points from Santa Cruz to South San Francisco via a system of 400 rail cars, each capable of holding 100 tons.

The company also offers decorative rock, concrete supplies and building materials. Its products go to large and small contractors, paving companies and a legion of large and small customers. The company boasts hundreds of longstanding customers, including Santa Cruz Underground and Paving, Inc. and Granite Construction for projects that include roads, paving and landscaping.

The company’s construction division offers services such as commercial site development, grading, paving, mass excavation and earth moving. The company has had a hand in construction projects throughout the area, including airports in San Francisco, San Jose and Salinas. The primary takeoff runway at San Francisco International was a Graniterock project, as was part of San Jose Valley Medical Center. “Graniterock is proud to have been a literal cornerstone and part of the foundation of the Watsonville community,” Severson said. “We live and work in this town and have been helping make it the wonderful and unique environment it is since 1900.”


For a video of the blast, visit For information, visit

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