In the News

By Carl Emigh

Fine-crushing hard basaltic rock for making asphalt sand and C33 sand for ready-mix concrete is a tough job. This is what now makes up about 30 percent of the overall production at BoDean Co.’s Mark West Quarry near Santa Rosa, Calif. “That’s business we never had before,” said Director of Production Bill Reid. “And we’re planning to expand our production capabilities to meet growing market demands. Adding manufactured sand to our product mix is one of the best business decisions we’ve ever made. It kind of evolved over time.”

The quarry opened in 1910 and was run by various operators until BoDean purchased it in 1989 and updated and replaced the quarry’s existing equipment and systems. For several years, the quarry successfully produced base rock and two sizes of drain rock. At that point, making sand was 10 to 15 years in BoDean’s future, but never far from their minds.

“When we first took over the quarry, it was very vertical, with large faces,” Reid said. “The quarry is located on a steep hillside. We were mining rock 400 ft. above our plant. We had to do a lot of benching – that is, cutting flat ledges into the hillside to form what we called ‘work benches’ where we could drill and blast the basaltic rock. When we finished with an area, we would drop down to a lower level and cut a new work bench.

“As we came down the hillside, we ran into some water, clay and broken up rocks from time to time,” he continued. “We had to learn how to handle that to maximize our resource. But for the most part, we were crushing and screening relatively dry material. Over the years as we started thinking more and more about making sand, we knew disposal of clay and wash plant water would be a major problem because we have no room for settling ponds at our cramped vertical site.”

The Mark West Quarry, equipped with a jaw crusher, horizontal impact crusher and dry screening system, was very successful at that time. Base rock and drain rock were their main markets. But market demands were volatile, changing yearly or even monthly. They saw the next shift in the aggregate industry moving toward asphaltic and concrete rock.

Also, Sonoma County, along with other counties in California, was telling aggregates producers to stop taking alluvial gravels from rivers and streams. That further increased demand for certain types of crushed aggregates. The quarry’s product mix at that time included drain rocks and base rocks.

Enlarging the Quarry

In 1994-1995 BoDean decided to enlarge the Mark West product line by including rock that could be used in asphalt and concrete products. “To fulfill all our fluctuating demands efficiently,” Reid said, “we developed a system with swinging product gates that provided diversification with one simple plant. That took a lot of creative engineering and design. But it means we didn’t have to change screens each time we changed product lines. While the fine crusher produced an abundance of the small 3/8-in. chip, it did not produce enough of the sand product. Both of these products were not being produced in the right shape – it was too long and flat. So the fine cone crusher was replaced with a REMco 9000 rock-on-rock vertical shaft impact crusher.

“The jaw-cone-VSI system with dry screening enabled us to produce our existing product mix plus the asphaltic material with a very good cubicle shape,” Reid said. “This added to our product sales potential, and overall we had better quality products with greater durability and workability at lower production costs. Further, it added to our tph capabilities and cut maintenance time and expense significantly. Plus, we were a step closer to making sand.

“With this equipment and system we operated very successfully for a number of years,” Reid said. “But since we were so dependent on contracts that can come and go, we decided to enter into the asphalt business ourselves, and purchased an asphalt plant nearby. At first we were buying sand for the plant from an outside local source, and that was working out. But the sand source began to dry up. Sand was becoming more expensive, and the supply was sporadic. We were at the mercy of our suppliers, some of whom were our competitors. So we knew we were going to have to take control of our own destiny and make sand.

“Further, we thought it was potentially very profitable,” Reid said. “But we still had to solve the problem of disposing with wash plant water and clay waste. The rock we mine contains 15 percent to 20 percent clay, or cake, as we call it. With no room for settling ponds, we had to find a good way to deal with the cake if we wanted to make sand. So we did our homework.”

BoDean checked out various solutions, including belt presses to move waste off site, but nothing seemed quite right. Then they found a plate press system from Europe that enabled them to stack the cake and bring it back up the hillside. There it was mixed with overburden and placed in the reclamation project required for all quarries by California law.

“That was our ‘aha’ moment,” Reid said. “At that point we knew we could make sand efficiently at this quarry site. We were jubilant. Our next challenge was to determine how to revise or add to our existing plant to produce the sand. Again, we went to REMco. They’re the sand experts. We liked that they know all there is to know about cone crushers versus VSI crushing capabilities. In the process, we looked at a lot of numbers ­– a premium plant versus more economical plants – what would the payback be? We chose the premium plant, and the payback has been about four years.

“In addition to a wash plant, we installed a REMco 400 SandMax. The result has been everything we’d hoped for. We make top quality sand, including spec sand products, very efficiently in terms of production, capital cost, wear parts cost, and balancing production to meet market demands. Further, REMco gives a production guarantee on their equipment; so we went into sand making with great confidence. It’s one of the wisest business decisions we’ve ever made at this quarry."

Crushing Circuit

Plant Superintendent Anthony Boyle explained the crushing circuit, consisting of a primary plant with a feeder and jaw, and a secondary plant with a cone crusher, a REMco SandMax, and three screens that combine to produce all the various aggregate products and sand needed for market demands.

Incoming material is deposited by front-end loaders onto a vibrating grizzly feeder and fed into the jaw crusher. From there, the crushed material goes to a surge pile with an underground reclaim tunnel, equipped with two belt feeders, to feed the secondary plant with a 7- x 20-ft. three-deck screen.

Here aggregate is separated out: the smallest is ½-in. minus. Everything else goes to the secondary cone or tertiary VSI. Then it is collected on a common belt that feeds to a closed circuit system that consists of a 6- x 20-ft. three-deck screen, a 6- x 20-ft. two-deck screen, and the cone and VSI. From there, the material can go to individual stockpiles or to a blending belt. This blending belt feeds a stockpile/surge pile that feeds the wash plant.

Under the surge pile is a reclaim tunnel with a belt feeder that feeds a quality control screen that eliminates clumps. The material then goes to the blade mill (for agitating and scrubbing) and on to a 7- x 20-ft. triple-deck horizontal screen. It then moves to stockpiles or back to the REMco 400 VSI and on to the blade mill in closed circuit. The smallest material goes to a sand pump to a cyclone to a dewatering screen to final stockpile as C33 spec sand at higher than 3.1 FM.

“We use a cyclone instead of the much larger sand screws because of our lack of space,” Boyle said. “We found that the gradation consistency is beautiful. And with two VSIs in the system, we have all cubical product – nothing flat or elongated – and we’ve eliminated oversize and out-of-balance material.”

After supplying their own asphalt plant with sand, BoDean still had an abundance of sand to sell to other markets. They determined that the best market for their purposes was ready-mix concrete, but producers resisted.

“They were so used to the super smooth alluvial sand that they felt manufactured sand wouldn’t finish well,” Reid said. “They thought it would leave marks, would be rough, would be unstable, and wouldn’t pump well.

“We pointed out that manufactured sand was being used all over the world,” Reid continued, “But they still resisted. We tried several ready-mix suppliers, but to no avail. So we did our own test pours, using the concrete for our own equipment footings, and that worked very, very well. We offered to give sand to concrete companies to try out, but they didn’t want it. It was like they had a mental block.”

“We saw that as a chance to go into the concrete business ourselves; so we became affiliated with a ready-mix concrete company,” Reid said. “That was in 2010, and it has been a great opportunity for us. The only difference we see between concrete made with alluvial sand and manufactured sand is a little bit of our natural stone color once it dries. Otherwise, there’s no difference. Manufactured sand is at least as good as natural sand, sometimes better. And what’s more it’s available when natural sand is in short supply or is too expensive. The ready-mix companies we’re partnering with are selling concrete for finishing and everything else: bridges, overpasses, buildings and so on. The strength is high, and there have been no issues.”

“A lot of times problems are lead-ins to opportunities,” Reid said, and pointed out some examples:

• As electric costs soared, they experimented with solar power at their offices in 2007. That worked well; so they installed solar panels on a reclaimed hillside to power the entire quarry. That has saved us a lot of money and has ecological benefits. Now other California aggregate companies are trying solar and/or wind power.
• They don’t have room for settling ponds; so they found a neat, efficient way to use waste material as part of the reclamation process. It’s far better than messy, mucky, hazardous settling ponds, and it will save them money over time.
• Same with manufactured sand. You ask the great majority of quarry operators and they’ll say it can’t be done successfully. Well, we’re doing it very successfully. And it’s a huge market. But usually it can’t be done with a quarry’s existing standard crushing equipment like primary jaws and cones or primary horizontal impactors and cones. They found the VSI to be the solution.
• They’re selling all the sand they can make. Currently their run time is 65 hours a week with about 700 tph from the jaw crusher, 500 tph from the cone and VSI combined, and about 80 tph from the SandMax. They can only run the sand plant long enough to digest the waste mud. So they’re planning to expand their reclaimed water system to double run time.

“To any quarry operator who thinks making sand is a can of worms, I’d say it’s more like a can of opportunity,” Reid said. “Just do your homework, talk to manufactured sand experts, then make the investment and reap the profits you’re not getting now. It’s a big market. There’s room for us all.”