by Mary Weaver with photos by William Weaver

The Eden Stone Quarry, near Eden, WI is a busy place. “Trucks come and go all day,” explained Michael Schumacher, LEED® Accredited Professional working in business development. “We can load 20 trucks and ship 500 tons before lunch. In addition to the outside carriers that come in, we also have our own fleet of Peterbilt trucks. We operate 15 ton haul trucks and pup trucks with a dump box on the back that we built ourselves.”

Eden Stone’s six dolomitic limestone quarries, while all containing a hard, non-permeable, chemical resistant rock, have rocks that are valuable for different reasons. “At Eden Stone’s main quarry, we are walking on a bedding plane that is 425 million years old,” said Biller. “It’s a Niagara dolomite, the same kind of rock formation over which the Niagara Falls flow.”

At the Stevens Point Quarry, much of the rock features ripple marks. According to Biller, “The Stevens Point Quarry produces well cemented sandstone, different in hardness and appearance from the dolomitic limestone that comes from the rest of our quarries.”

Chilton Quarry, for example, contains dolomitic limestone in many beautiful colors, including red, pink, sunset orange, and deep yellow. These are quarried below an outcropping that was first noticed when it was a farmer’s field.

Their Oakfield Quarry yields rocks that have a weathered, distressed appearance. ‘’We call them Holey Boulders,” commented Martin Biller, Environmental Compliance Manager and Professional Geologist. “The pitting is from weathering, perhaps from softer shelled fossilized animals weathering out.” This natural finish is in demand, particularly in historic districts.

Rock splitting facility

The rock splitting facility at the Eden location, is designed for worker safety, comfort and efficiency. It also maintains an environmental friendliness. As a result, the current average length of worker employment at this facility is 15-16 years. Because of the company’s concern for the employee well being, the workers are very content, so they tend to stay. This also affects the company’s stellar safety record.

Inside the stone cutting facility, each of the HYDRASPLIT® stationary stone splitters (manufactured by Park Industries of St. Cloud, MN), has quilted baffles on either side, to limit the sound and dust it produces. Additionally, water is available for washing and dust reduction at each workstation. Each of those is cooled with extra fans in hot summer weather. “The 17,000-square-foot facility is the company’s own design and construction,” explained Biller.

Ergonomics is a priority at each step of the rock splitting process as well. For example, at each workstation, the skids on which the cut stones are stacked, are all height adjustable. “As the weight goes up, the base under it moves downward so workers are always stacking at waist height,” noted Biller. Finished stones are stacked according to size, color and shape. Another feature of the unit is that the skid bases can swivel 360 degrees at a worker’s touch. This is assisted with the help of hydraulic pistons. This brings the side of the skid to be loaded into a convenient position for the worker.

At the guillotine, each operator is able to set the distance that the stone can move into its jaws. “When the stone slides in to that point, it is snapped in place there.” This helps to prevent accidents.

“We’ve worked over seven years, 2,250 days to be exact,” (at the time of our visit last summer) without a lost time injury.” This record is even more remarkable, considering the exceptionally hard, dense stone that the workers handle, which can be razor sharp, particularly when cut.

“We’re a non-union, completely merit shop,” noted Schumacher. “Even our drivers are non-union.”

To reduce worker monotony in the rock splitting facility, they rotate jobs. This helps avoid mishaps. “A given worker would not always be running the splitter. He would move to the backside of the guillotine to catch cut stone as it comes out. There, they stacking it on skids.”

From an environmental standpoint, this plant is also “a gem” in another way. Most of the heating needs at the plant are supplied by a geothermal heating system. The remaining heat needed during winter, comes from waste oil. Heat exchange tubing for the geothermal heat pump system is buried in a berm a short distance from the building, near a stand of pine trees.

“The geothermal heat is also used to heat the stone so it is easier to work with. Because the stone is so hard and dense, it has to be heated to ambient room temperature before it is shaped,” explained Biller.

The facility also recycles water in huge quantities. “Up to 250,000 gallons of water per day, used to cool and lubricate the blades of saws cutting rock, is captured, filtered to remove rock dust and suspended solids, and recycled back to the saws to be reused, repeatedly.”

Hard stone has many uses

Because Eden Stone’s products are quite valuable, with much of it is sold by weight, Eden Stone employees trim the excess stone from cut pieces. “We don’t want our customers to pay for material they can’t use.” The cutters’ chips are converted into mini riprap, crushed into gravel by another operator or used for road berm in the quarry.

Once workers fill a skid, it moves to a computer controlled wrapping station. Inventory control starts there. Each skid is identified with a unique tag describing the product and its tonnage.

This stone is sold for flagstone, landscaping stone and custom steps. It can also be processed for building veneer. The dolomitic limestone quarries at Eden Stone (six of the eight quarries) is exceptional for these uses. Because of the rock’s high levels of magnesium, this dolomitic limestone is much harder than ordinary limestone. It is also extremely dense. A 12-inch x 12-inch x 12-inch piece of Eden material weighs approximately 170-pounds, compared to 110 pounds for Type I limestone and 135 for Type II. Additionally, because it registers at approximately four on the Mohs Hardness Scale, it is cut with diamond saws. It is resistant to moisture infiltration, and is resistant to chemical weathering as well.

“If you put a 10 percent solution of hydrochloric acid (HCl) on Indiana limestone, it will fizz,” explained Biller. “Our dolomitic limestone here is more resistant to chemical weathering, and is not affected by HCl.”

Mining the rock

In the quarry itself, the sedimentary rock is nudge blasted. Then, the layers are carefully separated by highly skilled loader operators with Volvo L-90 forklifts. “Those operators could tie boot laces with a forklift,” commented Schumacher. “A lot of times, we don’t even need to blast. The operators just peel the layers apart, very gingerly, tapping the layers in just the right places to separate them. They work to yield as many large pieces as possible.

“Our staff love the Volvo L-90’s for this work,” he continued. “Workers have better control of the forks, and the machines give a smoother ride over bumps. The smoother ride is easier on the stone and on the drivers as well. In addition, these Volvos have reduced maintenance and fuel consumption compared to other brands.”

In one of Eden Stone’s other quarries, near Chilton, WI with similar stone, Volvo L-20’s are used. “They’re a little more compact for the work we’re doing there, but the advantages are the same.”

Much of what the workers do by hand in the quarry consists of separating out individual stones for their respective product lines. Different qualities of stone go to the splitting room, to the sawing shop, or for landscaping stone, custom steps or for building veneer. “Stone can be separated by straightness (important for steps), regularity, color or the thickness of the layer. Our flagstone is our No. one selling product. Mother Nature gave us the layers, but it takes expert loader operators to separate them,” noted Biller.