THE CEMENT PLANT AT CLARKDALE

When the engineers huddled over their slide rules in planning the Glen Canyon Dam in Northern Arizona, they came up with some fabulous statistics. They decided to build a gravity-arch type of dam to rise seven hundred feet from the Colorado River bottom. Their calculations called for 5,000,000 cubic yards of concrete. That's a big pile of concrete and almost twice as much as they used at Hoover Dam, a pretty good-sized structure itself. The next problem was to find enough raw material as close at hand as possible to make the necessary cement usually referred to as Portland cement. An Englishman is responsible for the name "Portland" as he thought that concrete made from cement looked exactly like the rock formations on the Isle of Portland off the English coast. The basic ingredients of cement are limestone and gypsum. An enormous deposit of the former was located at Clarkdale, Arizona, at the base of Mingus Mountain, a short distance below the ghost town of Jerome. The mines at Jerome have enjoyed a peaceful tranquility since 1950 when they shut down marking the end of an era. During its heyday there were over 20,000 people living in the Verde Valley which includes Jerome, Clarkdale and Cottonwood. The population shrank to the 1,000 mark, but not before they carted away over a billion dollars in copper, silver, gold, lead and zinc. The geologists found enough limestone a short way up the hill from Clarkdale to last over a thousand years. They uncovered two important deposits within a mile of one another and logically the cement plant was built between them. Limestone is formed by an accumulation of dead marine life collecting at the bottom of an ocean or lake. According to a Geological Survey prepared by the U.S. Department of Interior, Clarkdale was an ocean bottom area five different times and a lake bottom once. Quite an interesting background. The ocean bottom period covered about five hundred million years while its lake bottom existence lasted a mere twenty million. The older deposit is called Redwall, its younger counterpart Lakebed. Modern man comes along, mixes the two deposits together, then adds a little gypsum from Camp Verde, a little slag from the smelter at Clemenceau and there you have it. Of course the exact recipe is a closely guarded secret, but you could make up your own "mix" if you really were interested. The cement plant has been in full operation since early summer 1960. It is owned and operated by the Phoenix Cement Company, a division of the American Cement Corporation. The plant was designed and engineered by the Fluor Corporation and built by the Fisher Contracting Company of Phoenix.

As might be expected, the plant is an achievement in modern engineering. Automation has cut manpower to a working crew of 130, a paltry few compared to older plants with comparative production. The latest methods have been used to conquer the dust problem. If you have ever driven past an older cement plant you will have noticed a heavy layer of limestone on the countryside for miles around. Telephone wires, poles, trees and shrubbery are covered with the stuff. Well that isn't the case at Clarkdale, thank goodness. They have devised a glass bag contraption which traps 99% of all escaping dust and gas. All that is visible is a small wisp of blond smoke. Otherwise the plant operates along the old and classic methods of manufacture. They collect the various ingredients from the cooperative countryside in big dump trucks. The material is crushed to proper size in the confines of tremendous steel grinders. Then the proper mix is dumped in a long tubular kiln or oven where perfect fusion takes place to form cement. The finished cement is stored in towering silos for shipment. The kilns, which average eleven feet in diameter, are 350 feet long and turn while in operation. These kilns used in the manufacture of cement are the largest pieces of moving machinery known to industry. The fusion takes place because of the tumbling action of these gigantic cylinders plus the added factor of applied heat along its length to the tune of 2750 degrees F. Fortunately natural gas is available. They use 4,000,000 cubic feet of natural gas per day. At present capacity the plant at Clarkdale is shipping about thirty truckloads of bulk cement around the clock to the Glen Canyon Dam project 190 miles to the north.

Testing new batch of cement "Shooting" in kilns to loosen cement

They expect to ship about 1,000,000 barrels of cement per year. That leaves a balance of 500,000 barrels available for sale locally in the Northern Arizona area.

During 1960 the cement trucks had no choice but to plod up the tortuous cutbacks through Oak Creek Canyon to reach Flagstaff on the plateau above. Starting in 1961 the route was changed. Now these lumbering giants head east towards Camp Verde, then north on the Black Canyon highway to Flagstaff. The Belyea Truck Company has the hauling contract. They figure that their drivers will rack up 137,052,000 cargo-ton-miles to make it the largest over-the-road cement haul in history.

Clarkdale, like its surrounding topography has had its ups and downs. The oldtimers have "seen 'em come and go." They remember Jerome and Clarkdale in their heyday. Those days haven't come back and aren't likely to. But every little bit helps. The building of the cement plant brought a large although temporary influx of workers to the area. The present force of 130 men and their families are on a more permanent basis. Of course they are a drop in the bucket compared to thousands of miners employed when copper was king. Nevertheless the aluminum-helmeted cement plant employees and their families have given the local economy a welcome shot in the arm. When the dam is completed in 1963 it is bound to slow things down at the cement plant at Clarkdale. But maybe not nearly as much as some people think. Northern Arizona is growing at a lively rate. Cement is a necessary factor in housing and roads. Besides there is doubtless additional reclamation work in sight for the Colorado River which supplies life giving water and power to large areas of the Southwest.

350-foot long fusing kilns Kiln where materials are fused Technician in chemical lab