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Maryland Sand and Gravel Profits From Rare Seam

Fri August 16, 2002 - Northeast Edition
Construction Equipment Guide

A seam of sand running across the Delmarva Peninsula from the Atlantic Ocean to the Chesapeake Bay, plus a fleet of stone-hauling trucks returning empty to Pennsylvania, were the opportunities that have added up to success for a new northern Maryland sand and gravel enterprise. With a strong partnership and the right equipment in place, the business is increasing production and laying plans for even more growth in the future.

Kent Sand & Gravel, near Galena, MD, has been in operation for two years on former farmland on the coastal flats of the northern Delmarva Peninsula.

The company was founded to mine a seam of sand and gravel that was a rare find in the aggregate-poor area. “There is a sand and gravel seam that runs from Baltimore all the way over to Lewes, DE,” said Co-Owner Miles Bennett. “It’s kind of unusual to the area.”

Kent Sand & Gravel mines and sells approximately 500,000 tons (450,000 t) of product a year, including ASTM C33 concrete sand, mason sand, .375-in. (.95 cm) pea gravel and .75-in. (1.9 cm) gravel used in ready-mix concrete.

Early in the operation’s history, Bennett made a fortuitous connection with Haines & Kibblehouse (H&K), the Skippack, PA-based aggregate, concrete and asphalt conglomerate with numerous quarries. H&K was at that time hauling rock to Maryland and Delaware and returning to Pennsylvania with empty trucks. By forming a partnership with H&K, Kent Sand & Gravel gained an experienced partner in the aggregate business and a ready market for as much spec concrete sand as it can produce.

Silt Washing

The sand and gravel seam contains about 15- percent gravel and varying amounts of silt and clay, according to Bennett. “Passing 200 mesh is approximately 10 percent.

“And it’s a very silty clay material that clings, so it has to be washed and separated, and our classifying tank basically separates the material.”

All feed material is first screened through an 8- by 20-ft. (2.4 by 6.1 m) triple-deck inclined vibrating screen fed by a 36-in. by 165-ft. (91.4 cm by 50.3 m) conveyor. A 24-in. (61 cm) GreyStone log washer cleans clay from the gravel, which is then sized to produce the two product sizes by a 4- by 8-ft. (1.2 by 2.4 m) inclined vibrating screen. A 12- by 48-ft. (3.6 by 14.6 m) by GreyStone Aggre-Spec II classifying system with 11 stations sorts sand into the two finished products. A GreyStone 48-in. (122 cm) twin screw washes and dewaters the concrete sand and a GreyStone 44-in. (111.7 cm) single screw washes and dewaters the mason sand. Concrete sand is stockpiled by a 36-in. by 120-ft. (91.4 by 36.6 m) radial stacker; while the mason sand exits the screw onto a 30-in. by 60-ft. (76.2 cm by 18.3 m) radial stacker.

With varying layers of clay and silt in the seam, Bennett appreciates the flexibility of the system to save costly steps when they’re not needed. “Sometimes we’re producing a gravel that doesn’t need to go through the log washer. We can take it off, stockpile it and sell it, and then take the other gravel through the log by itself and stockpile it. Or we can combine them.”

Choosing the Right Equipment

In spite of the fact that other classifying system manufacturers were more established in the area, Bennett said, Kent Sand & Gravel is equipped with a complete system manufactured by GreyStone. “Unlike some of the competitors we looked at, GreyStone uses a lot of standard items on parts that wear out, like bearings, so you don’t have to buy the parts just from them. That was a big plus. We’ve had a lot of people come look at our plant, and they like it.”

Timing was another reason for buying GreyStone washing and classifying equipment. “GreyStone was able to meet our schedule,” Bennett said, “and we saved a season that we otherwise wouldn’t have had.” Kent Sand & Gravel bought its GreyStone equipment from the local dealer, Kemper Equipment, based in Honey Brook, PA, and its sales representative, Greg Donecker.

Dredging for Higher Production

Kent Sand & Gravel was originally set up to classify and wash dry material mined from the surface. The company is now building a new dredge and will start operating it a few hundred yards from the classifier. “We know that we are ultimately going to get a more consistent blend by mining the pit vertically. The dredge is going from basically zero down to 70 ft. We have a solid gravel seam and then we have sand and then a finer sand,” Bennett said.

While switching over to a total dredge operation isn’t painless, Kent Sand & Gravel’s automated Aggre-Spec II Control System is making the process easier by helping to maintain production during the switch. “In the past when we were mining just horizontally with the loaders, it was a little more difficult, but we learned to make a spec product with it. So now we’re learning over again, but we think this is going to be a little bit easier,” Bennett added.

The GreyStone plant is being switched back and forth between hydraulic and dry operation until the complete conversion to dredge feed is finally complete. During dredging operations, 5,000 gal. (1,8927 L) per minute of dredge slurry enters the system. An energy-dissipating pump box slows the feed material and maximizes the amount of retained product entering the tank for classifying. At this higher feed rate, Bennett is planning to increase production capacity.

Backed by the expertise of a classifying and washing equipment manufacturer capable of supplying equipment ranging from single components to complete systems, Kent Sand & Gravel is keeping the Haines & Kibblehouse trucks returning to Pennsylvania filled with high-quality spec sand. And with a steady customer for its concrete sand, Kent Sand & Gravel can focus on increasing production and creating more opportunities for profit and growth.

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