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Mining 30 year old construction debris rejuvenates Potomac landfill operations

Potomac Landfill, Inc. began operations in 1985, not far from Washington, DC. By 2006, more than 75% of the 52.8-acre landfill area of the 96-acre site was full, leaving only 12.8 acres for future use. Since then the company has been taking an innovative approach to extending the life of the landfill. By mining and recycling construction and demolition material that was buried 60 to 120 feet deep between 25 to 30 years ago, Potomac is breathing new life into a 26-acre area. Included are wood, ferrous and non-ferrous metals, plastics, concrete, cardboard, tires, and dirt that is suitable for use as fill or topsoil. Non-recyclables are returned to the landfill, where they now take up far less space.

This leaves room for new construction and demolition materials trucked in daily by local construction, demolition and excavation contractors. Both the mined and the incoming materials are thoroughly screened to remove usable dirt and recyclables. Potomac is strictly a construction landfill. The company does not accept residential or commercial garbage.

A track-mounted Powerscreen® Warrior 1800 purchased new in 2009, a track-mounted Warrior 2400—Powerscreen’s newest and most advanced dry screen—purchased new in 2010, and a 20-man portable picking station are the key factors in the tremendous success of the operation.

"It’s working out every bit as well as we’d hoped," says General Manager Richard Campbell. "We figure the combined mining, screening and picking station operations will add another 20 to 25 years to our landfill, plus we salvage a lot of recyclable materials we can sell for profit and to help preserve the environment.

"In the old days, practically all the incoming C&D debris—except for some of the very largest pieces of wood, concrete and metal that were picked out by hand—was dumped into a hole and covered up. That’s the 26-acre site we’re now mining."

The Powerscreen Warrior 1800 is used primarily to remove dirt from mined debris. Originally it was used to screen both new and mined materials in conjunction with the picking station.

"The Warrior 1800 is fitted with a fingered screen, which is good for mined materials that have a lot of dirt mixed in," says landfill Operations Manager William ‘Tom’ Lewellen. "It’s great for getting the fines out. Both incoming new debris and mined materials that have had the dirt removed by the Warrior 1800 are processed through the Warrior 2400, which is a heavy-duty machine with an extra-large hopper and is equipped with optional punch plates instead of fingers; so dirt and small materials fall through, while the most worthwhile recyclables remain. Thus, there is very little clogging, and any clogs that do occur are easy to free up. Punch plates have been used a lot in Ireland and other foreign countries, but not much in the U.S."

Lewellen further explained that the Warrior 1800 has a standard rubber feed belt, which is fine for mined materials with their high dirt content. The Warrior 2400, however, has an optional metal feed belt, which is much better for handling the new, incoming construction debris. The metal belt gives smoother operation, has a larger screen area, is more durable than rubber, and materials are less likely to get hung up in it.

Lewellen emphasized that portability is also important, "Moving either Warrior takes just the push of a button and off it goes. The tracks easily handle rough, uneven ground; they don’t get mired down in mud like wheels do; and the 2400 has individual hydraulic jack-up legs for quick, easy levelling."

"Screened materials from the Warrior 2400’s discharge conveyor are deposited onto a beltline that runs through a portable, 74-foot-long picking station with up to six large dumpsters positioned under it. Each dumpster is designated for a recyclable material: typically two for woods, two for metals, one for concrete, and one for cardboard. Depending on beltline volume, 12 to 20 workers standing alongside the beltline in the station pick out recyclable materials, which are dropped into the dumpsters below. Filled dumpsters are removed by truck as needed and replaced with empties Junk materials to be landfilled drop off the beltline at the far end of the station in a stockpile and are removed by a front-end loader.

"Before we bought the Warrior 1800 in 2009," Lewellen says, "we looked at various types and brands of screening equipment. First we tried a trommel, but it clogged way too much. We also tried other kinds of equipment that were not satisfactory, including a star screen that wouldn’t do what the manufacturer said it would. It simply wasn’t designed for our kind of application, though we still use it sometimes in a secondary capacity.

"So we continued our search. We found that manufacturers and dealers would give us a lot of information and promises about their equipment, but only Powerscreen Mid-Atlantic, the Powerscreen distributor headquartered in Kernersville, NC, brought their machine—the Warrior 1800—in for a demo on site, processing our material. They also took me to a landfill in North Carolina to see a Warrior 1800 working and talk to the owner about it. Based on all that, buying the 1800 was an easy decision, and has proven to be a very wise investment.

"When Powerscreen introduced the Warrior 2400 in 2010, we saw it as the perfect partner to the 1800 for our purposes," Lewellen explained. "Powerscreen Mid-Atlantic recommended the punch plates and metal feed belt. Our Warriors are efficient, dependable, and require very little maintenance."

"Using the two Warriors and the picking station has doubled our production," Campbell added. "In 2010 Potomac Landfill Inc. produced 60 million pounds of recyclable materials—that is, materials that did not have to be landfilled. We’re one of only two construction landfills in Virginia that are mining old landfill materials. It has been incredible how well our two Powerscreen Warriors have handled the different types of materials we’ve thrown at them.

"We have an excellent relationship with Powerscreen Mid-Atlantic," said Campbell. "We get good, timely service as needed, and we can call on them at any time for advice, whether it relates to Powerscreen equipment or to Potomac Landfill operations and screening in general."

The Powerscreen Warrior 2400 is designed for tough service in large scale quarrying and mining applications. It can handle larger feed sizes and throughputs. It features a heavy-duty incline screen with a high amplitude, triple-shaft drive mechanism, lending it to screening, scalping, two- or three-way splitting, and stockpiling materials such as aggregates, C&D waste, topsoil, coal and iron ore. It is rated up to 800 tph, depending on materials and conditions. The Powerscreen Warrior 1800 is a smaller, equally versatile machine designed for medium to large applications.

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