Mountain Shifts Slowly From Stone to Cement
California’s great peaks--Whitney, Shasta, Mammoth Mountain--dwarf tiny Mt. Slover.
Even a century ago, before miners blasted so much of it away, Mt. Slover was scarcely more than a molehill. It stood 700 feet tall, base to summit, on an arid plain in what is now Colton.
The mountain’s size and shape have been vastly altered. Nearly 100 million tons of rock have been carved away, leaving a steep, conical mound gouged with terraces.
The flattened summit is now 300 feet high. A giant American flag stands on top, often stiffened by winds funneling through the Cajon Pass. From the pole, you can look south and east and see quarrying pits where sections of the mountain have been removed. Miners tapped all of the limestone from the slopes and are still boring after it deep below the surface.
Limestone is what raises Mt. Slover to an important geographic feature. It is the site of what is believed to be the oldest continuously operating cement plant west of the Mississippi River.
“We like to think we’ve transferred the mountain to the L.A. Coliseum... the San Diego Convention Center... [and] the Bonaventure Hotel,” said Mike Robertson, plant manager for California Portland Cement Co., which has owned and mined the mountain since 1891.
Standing on its crest, gazing down at the pits and the rugged machinery of the cement plant beyond, Robertson recited a list of roads, churches and other structures created from Mt. Slover.
Hoover Dam is one. The first freeway, from Los Angeles to Pasadena, is another. Thousands of other, nameless projects account for much of Southern California’s sprawl.
Today the limestone comes out of the pits, from the rich mineral deposits that once formed the mountain’s deep base. The visible remnant of Mt. Slover is useless for cement--a granite spire valuable only as a Colton landmark.
Millions see it each year from the San Bernardino Freeway, which skirts the north flank. Treeless and barren, a mottled gray and white, the mountain has the odd look of sculpted ash. A gravel road winds its way to the top, along berms of piled rocks and boulders. When America entered World War I in 1917, cement company officials won special approval from Congress to fly a flag on the mountain day and night--one of only three places in the country granted the privilege. The flag came down in the 1950s but was raised again, permanently, a few years ago.
Workers Take Pride in Their Small Mountain
The flag shows the pride many workers feel about their diminutive mountain. Quarry foreman Jim Hardin is one of 130 employees who help mine the 560-acre site. Like many, he has been around a long time: 39 years come July. “Next year,” he quipped, “I’m going to look for something steady.”
Hardin has an idea for when he is dead and gone. “I want to be bronzed and put up at the flag pole,” he said. “When people ask, ‘Where do you work?’ I say, ‘The hill with the flag,’ and they know exactly where I mean.”
A hunter and trapper named Isaac Slover settled at the foot of the mountain more than 150 years ago. He was in his 70s when he died in 1854, after being mauled by a bear in the Cajon Pass. The incident is legendary in Colton, a rough-hewn railroad town of 40,000, but is less relevant now than the more distant story of the origins of cement.
Ancient Egyptians and Greeks, who experimented with lime-based mortars to bond building stones, began the long chain of events that led to the mining of Mt. Slover.
Romans perfected the process during pre-Christian times. The volcanic cinders of Mt. Vesuvius were rich in the necessary minerals. The cinders were crushed and mixed with sand and water to create a cement sufficiently strong and water resistant to build the empire’s famed aqueducts.
The art was lost in the Dark Ages. An engineer named John Smeaton, intent on rebuilding a lighthouse in Cornwall, England, succeeded in 1756 in re-creating a cement that could set in the presence of water.
Many years of refinement followed before another Englishman, Joseph Aspdin, earned a patent in 1924 for “artificial stone.” The material--a composite of limestone, sand and other compounds, slurried and heated to nearly 3,000 degrees--also came to be known as Portland cement, after the Isle of Portland off the English coast. The product created by the cement was said to resemble the white building stones quarried there.
Limestone accounts for about two-thirds of cement’s raw materials. Mt. Slover’s deposits are exceptionally pure. Miners extract it with carefully planned explosions.
On a recent day, crews spent five hours filling 137 drill holes with 20,000 pounds of ammonia nitrate and diesel.
Blasts Loosen 45,000 Tons of Rock
A cry went up--”Fire in the hole!”--and an entire ridge burst in a quick series of blasts, loosening 45,000 tons of rock.
Fifty-ton trucks move the limestone--some boulders are 5 feet in diameter--to crushing equipment extending three stories below ground. The machinery roars. The sulfuric smell of limestone boils through massive conveyors that carry broken rock to other crushers and filters. By the process’ end, the rock will be crushed finer than baking powder.
Two gargantuan kilns chemically fuse the raw materials--limestone, silica, aluminum and iron ore--into clinker, a rock-like substance combined with gypsum to create the finished cement.
The kilns, which work side by side, are the most impressive thing. Each is 13 feet wide and long enough to span the field at Dodger Stadium, from home plate to deep in the outfield bleachers.
Resembling sewer pipes suspended within elaborate scaffolding, the kilns are held at a tilt and slowly rotate to cause raw material to tumble into the 3,000-degree “burn zone.” Cameras with sapphire lenses monitor the interior, displaying it on screens in a control booth. The tongue of flame is mind-boggling. It is fed by coal and, of all things, used tires--a million of them a year. They actually burn cleaner than coal and are required as part of new emission-control regulations. Around the clock, seven days a week, tires are lifted by tall conveyors to a tiny rack above the middle of each kiln. With every rotation, a trap door kicks open and two tires at a time drop into the inferno. They are consumed in 30 seconds. Finished cement is stored in silos that hold up to 70,000 tons. Two hundred trucks a day haul it to building sites such as the new Catholic cathedral in Los Angeles.
Mt. Slover figures to produce for 30 more years. By that time, much of what used to be the mountain will be a deep chasm. Even the schist separating the two quarries will be mined to produce asphalt, Robertson said.
“We’re trying to get all the squeal out of the pig.”