Construction activity is booming in Florida. That demand is depleting the supply of raw materials and consequently driving up their prices. Many concrete and asphalt producers are scrambling for high-quality reserves. So when RMC-Ewell found an opportunity to build a plant on a 20-year sand deposit in Polk City, Fla., it dug in.

RMC Business Manager Mike Pearson says reserves are being stretched, creating a premium situation. More companies have become vertically integrated and would only sell to sister operations during severe shortages. “If you don't have any raw materials, you are going to lose out,” he says.

RMC cannot afford to lose out. The company operates five ready-mix concrete operations near Tampa and 43 plants in Florida. The company says it is the largest ready-mix producer in Tampa.

RMC leased a site with 550 acres permitted for mining; enough sand reserves to last the company 20 years. Two companies had mined the site since 1971, but it has sat dormant since 1990. The Bronson Sand Mine, named after the landowner, is near Polk City, about 45 miles northeast of Tampa and 40 miles southwest of Orlando. But getting the land was only half the battle.

The other concern for RMC is quality control. A consistent supply of coarse sand optimizes the concrete mix, which results in cost savings. High-quality materials, however, can be produced only by an efficient plant.

The responsibility of building a high-efficiency plant fell on the shoulders of Paul Polakoff, general manager of aggregates for RMC's Estero Quarry. Polakoff knew nothing about sand mining. But RMC officials were confident that he could pull it off after seeing his work at the Estero Quarry. They were right.

He had the $5 million dredge operation up and running in just eight and a half weeks. They first broke ground in May 2003, started erecting the plant that July, and the first truck crossed the scale on Aug. 27.

In 1978, Polakoff was drilling injection wells for Youngquist Brother. When the company began dabbling in limestone, he was elected to help engineer the plant, which is now RMC's Estero Quarry, also in Florida. Youngquist Brothers flew him to quarries around the country to find what worked and what didn't.

“I knew nothing about rock other than drilling,” Polakoff says. “When you don't know anything about anything, you look at it with such an open mind and view that you will only start bringing in the good ideas. We did real well with that little rock quarry.”

RMC bought Youngquist Brothers in 1999, and Polakoff went with the acquisition. And he focused his attention on the Bronson Sand Mine. Again, he was able to inspect the competition's technology with an open mind and decide what would work best. Once he was confident about what the plant needed and got the budget approved, he was ready to start.

Polakoff hired engineering and construction firms, like himself, with no sand mining experience. In fact, the contractors worked under a new name just in case they failed, Polakoff says. Before breaking ground, they held regular meetings at the local diner, scribbling ideas onto napkins. Polakoff says they went through 13 revisions before they were done, and started building before the blue prints were finished. The result was an efficient plant that could operate itself.

The Bronson operation has a two-fraction plant automated with Rockwell Automation software and proprietary methods from LPT Group. A computer adjusts the sand recipes.

The plant feed is controlled automatically by AFTCO nuclear density magnetic flow meters on the dredge and feed prep pump. The meters analyze the output and radios data to the control room so the computer can adjust the valves on the hydrosizers. They also indicate if the dredge is in a hard deposit, and if so, the computer will slow the plant. “That little red piece [flow meter] is $32 grand, but it is very accurate and does really good. It tells you exactly what you need,” Polakoff says.

Everything operates with one man in the control room and one on the dredge. The control room was built on a pad separate from the plant to prevent vibration. “I don't even need a man. I'm just scared the belt is going to tear,” Polakoff says. “(The control room operator) just sets the recipe, and he's gone.”

The existing dredge has a diesel-powered 12- × 14- × 32-ft pump. It pumps 6,500 gpm. But, its days as the main dredge are numbered. In April, the Bronson Mine will begin operating with a Twinkle dredge equipped with a G.I.W. 12- × 14- × 36-ft electric ladder pump and a linear chain cutter. The Viking chain is about 25-ft long. Polakoff says electricity is cleaner, safer and much cheaper than Florida's diesel fuel. Also, it will not need to overcome the atmosphere because the ladder is mounted underwater. It will pump 8,500 gpm.

For now, the Bronson Mine only produces 300,000 tpy. But once the new dredge arrives, the plant will produce as much as to 1 million tpy of DOT sand on a single 12-hour-shift.

Polakoff says the current dredge's capacity is too small, and the hard deposit is destroying the cutter head. It also builds ridges on the lake bottom that have to be redredged. The Twinkle, which Polakoff says is the only chain ladder head in Florida, bores with the chain to free sand for suction. The linear chain will not build ridges or potholes and will more adequately handle the deposit.

The two 10-year deposits have an overburden of fill dirt, sod and tree roots being stripped by an excavator and end dump. Below the sand is 7 ft of clay that is allowed to process because it has a good color, Polakoff says. The coarsest sand is 15 to 35 ft below the water table, and the finer sand is 35 to 70 ft below the table. RMC plans to stop at 70 ft unless it can secure a strong market for beach sand.

The top of the water table is covered by a layer of mucky waste left by a previous operation. With the help of recent technology, however, that sludge is now usable product.

The lake was originally dug with a 20-ft ladder by Florida Mining during the '70s and '80s, Polakoff says. RMC-Ewell will deepen it with an 80-ft ladder, but it first has to process the waste. “There is a lot of slime and it's nasty. It goes in (the prep screen) all slimy and it comes out (the dewatering screens) pure white,” Polakoff says. “That's new technology versus old technology.”

Dredged material is sent to a feed prep area that has a Metso Minerals 6- × 20-ft double-deck scalping screen and sump. The top deck consists of Trellstep urethane panels with square openings. The second deck is covered with Trellstep four-mesh urethane panels. Polakoff says he underestimated the muck and slime that falls off the first deck. In the future, he will be incorporating a sump to take it back to the lake.

The prep screen also uses a rubber torque tensioner on the motor base, which keeps tension on the belt shaking the screens.

From the prep screen, a G.I.W. feed pump carries 7,000 gpm through a 16-in. line to the plant and 70 ft straight up to two LPT desliming hydrocyclones. The heaviest and coarsest sand falls to the bottom of the hydrocyclones. Material smaller than minus 200 flows up to the hydrocyclone overflow and back to the lake by gravity. Larger particles from the bottom of the hydrocyclones are fed to two LPT hydrosizers.

Water is pumped into each hydrosizer producing an upward current to classify the sand based on particle size. Sand meeting a preset 4-30 mesh cut settles to the bottom of the hydrosizer's collection cone to discharge onto LPT dewatering screens.

Sand particles smaller than 30 mesh rise with the current of the hydrosizer and are sent to an overflow sump. About 99% of the sand in the overflow is smaller than 30-mesh. From the overflow, the sand is pumped to LPT separators. The dewatered fine sand is discharged into the in-line blending bin. A computer-controlled valve under the blending bin opens to allow sand to discharge onto a dewatering screen.

The water shaken out goes back to the top for a second cycle in a separate classifier. Polakoff chose dewatering screens because sand leaves with only 13% moisture. A dewatering screw can only reduce sand to 22% moisture. Also, a screw has moving parts that can be hazardous. Screens allow a person to get up close and touch the sand to inspect its consistency.

Water and some fine sand pass through the screens. The fine sand and water is discharged into a pump sump and pumped to a LPT separator by a rubber-lined LPT pump. The separator discharges the dewatered sand into the in-line blending bin.

The dewatered sand is discharged onto a transfer conveyor belt, equipped with a Ronan Engineering nuclear density scale. From there it carried to the stockpile on a pedestal stacker conveyor.

Polakoff says they can stack eight times more than a standard radial stacker. There is 87 ft from the discharge to the center. By raising it up 11 ft, it can stack 104,000 tons.

The Stephens-Adamson troughing idlers are greased for life, but are not exposed to a lot of sand. Belts are counterweighted by the tail pulley rather than hanging a weight from the middle. This eliminates the need for two bend pulleys and a gravity take-up mounted mid-belt.

The tower encompassing the plant is all bolted, 100% galvanized steel. Polakoff says galvanized steel costs nearly half as much as regular steel with two coats of epoxy paint and a urethane overlay.

All of that steel on a Florida ridge, however, would draw enough lightening make Benjamin Franklin nervous. But Polakoff fends off the lightening with lightening dissipators that also act as light poles with flood lamps. Each dissipator is connected by a network of copper wire running underground and to the top of each pole. An umbrella of barbwire on the top emits positive electrons from each point.

Unlike a lightening rod, the barbwire loosely scatters positive electrons into the atmosphere, and the lightening looks for another source to strike. It may strike all over, but never the tower.

The entire plant also is ground fault protected by Cutler-Hammer Advantage motor controls. Polakoff says having a system that trips immediately if something goes wrong provides more safety than a good ground.

RMC-Ewell also installed a $500 IT analyzer on the controls that can analyze power consumption before the power company sends the bill. It can be reset each month to illustrate kW demands and efficiency. Information can be graphed day by day or for an entire year.

The analyzer also makes the plant safer. “MSHA loves it. If there is any kind of ground fault at all, even if it is an extension cord, it can trip the main breaker,” Polakoff says. “It gives MSHA better confidence.”

The product is loaded for contracted drivers by Volvo 220-E loaders. Loaders are equipped with Load-Right scales, which can load a truck within 200 lb of the target weight. Each truck is weighed when entering and leaving the yard by two 11- × 80-ft Emery-Winslow scales.

Trucks that fall short are topped off by a screw conveyor with a 15-ton hopper. But before the tires even touch the scale they are washed on the ramp by water lines running off the hydrant system.

It all makes for one clean operation that feeds its own ready-mix needs and provides quality sand at a premium price. And, it only requires two men to run it — not too bad for a team's first sand plant.

Home on the Range

When Paul Polakoff, a general manager of aggregates with RMC-Ewell, looks through the sliding glass door of his trailer, he often sees herds of buffalo meandering past his sand plant. They're not even phased by the hum of the conveyors stacking concrete sand between the trees or the front-end loaders digging in the stockpiles.

In the forests and swamps of central Florida, a $5 million sand mine is producing up to 1 million tpy between fields of cow pies. RMC-Ewell leases the property from cattle rancher Donald Bronson, whose father bought the land in 1947. All of the pasture was originally cleared by Bronson's family.

“It works good together, sand mining and the cow business, because sometimes the cow business isn't always the best business in the world,” Bronson says. “It allows me to do more things that I like.” He continues to raise his cattle and hunt the property, while RMC-Ewell buys his sand. He also raises exotic animals such as emu. On most days he eats freshly killed game in his clubhouse next to a pond with mallard ducks.

The land has won several environmental awards for Bronson including the Florida Environmental Stewardship Award in 2000. “I was trained at an early age to protect the land and look after people and future generations,” Bronson says. “I've been an environmentalist before I even heard the word.”

In the early '70s, Bronson formed an organization and helped stop the government from seizing his land by Imminent Domain. The government claimed that it should own and control the land in order to preserve it.

Bronson first let sand miners onto his property with Florida Mining in 1971. The company mined until about 1990 when it was acquired by Vulcan Materials and moved to another site. RMC-Ewell started the permitting process in 2001, and the first truck crossed the scale in August 2003.

This unconventional relationship, however, requires compromise, which is why one of the stacking conveyors is cutting through two trees. The sentimental Bronson planted one of them when he was 17, so Polakoff tried to accommodate him. But when Bronson saw a worker raking leaves from the stockpile, he told Polakoff to cut it down.

“I'm trying to be real nice to him,” Polakoff says. “I want to get his input and work with him, and it's better that way.”

Polakoff set aside a small portion of the land near an old corn silo to preserve some of Bronson's artifacts such as old molasses tanks. Polakoff even found a rusted-out corpse of logging truck that Bronson bought from the original Ewell Construction Co. And an old wooden outhouse still sits behind the prep screen where Bronson's friends used to camp.

Naturally, Bronson expects the company to take good care of the land. “The first thing out of his mouth was, ‘I don't want any trash leavings on my property,’” says RMC-Ewell Business Manager Mike Pearson. And several signs posted by Bronson remind everyone entering plant. To ensure the man-made lake being dredge doesn't affect the natural swamp land, Polakoff built a berm to separate the two.

For mitigation purposes, “we are going to make a five-acre wetland, and hopefully it will turn into a better environment for the wildlife,” Polakoff says. There they will be transplanting several young cypress trees from an area they intend to mine.

Gaining the proper permits was a relatively painless eight-month process, which Pearson says is very fast in Polk County, Fla. There is no federal jurisdiction over the land because it is not attached to a moving body of water. Also, Bronson is very respected in the community, and the land had been zoned for mining in the past.

One reason for the smooth process was that RMC-Ewell tried to talk to all of the neighbors before leasing the property and announced its intentions in the local newspaper. The company also hired Polk County contractors exclusively.

We believe that you have to put back into the community what you take out, Polakoff says.

But Polakoff knows his permitting experience was more the exception than the norm. “What's hard to get is the permission from a county,” he says. “If you have that permit and that allowable feature to go in there, you have to be a good steward, and you better mine it to the best of your ability.”

Bronson Sand Mine has about 1,850 acres with 550 acres permitted for mining that will be mined over a span of 20 years.

That sand is our jewel and needs to be mined for all that it's worth, Polakoff says. The company's plan is to mine it efficiently over 20 years rather than race through it in 10 years and waste half the reserve.

New technology allows RMC to mine the waste left by the previous companies. If miners abuse the land today, they might not be allowed to mine tomorrow. And, if there isn't a supply nearby, costs could skyrocket.

“Are we going to bring the rock in on a ship to Tampa from Nova Scotia and tell our kids, ‘sorry, you have to borrow another $100,000 to build your house because we built golf courses on all of our sand and rock?’”
— Adam Madison

Major Equipment Reference

Dredge (arriving in March)

Twinkle dredge with a 12- × 14- × 36-ft ladder pump

Screening

Metso 6- × 20-ft horizontal screen
(2) LPT 6- × 12-ft VD-18 dewatering screens
LPT 4- × 10-ft VD-12 dewatering screen
(2) LPT HS3620B12 hydrocyclone
(2) 10- × 10-ft LPT DMS 105 hydrosizers
(2) LPT S-830A fines separators
LPT S-518AX scavenger separator

Automation

Allen Bradley RS View 32 and RS logics 5000
Ronan Belt Scales nuclear density belt scale
Siemens DSIII Sitrans pressure transmitters

Miscellaneous

G.I.W. LSA 400-hp pump
G.I.W. LSA 125-hp pump
Cutler-Hammer Advantage motor controls
Dodge Torque Arm II TA52115h25 speed reducers
Dodge head, snub and tail pulleys
Marathon Electric IEEE 841 motors
(2) 11- × 80-ft Emery-Winslow truck scales
(2) Volvo 220-E loaders
(2) 141-ft-long Conveyor Components Co. transfer conveyors
(2) 87-ft-long SEW eurodrive pedestal stacking conveyors