The Regeneration Game

Powerscreen Warrior screens help rejuvenate landfill operation in Washington DC

Formed in 1985, Washington DC-based Potomac Landfill Inc. are taking an innovative approach to extending the life of their landfill operations. Five years ago, more than 75% of the company’s 52.8-acre landfill area was full, leaving only 12.8 acres for future use.

Now, by mining and recycling construction and demolition material that was buried between 60 and 120ft deep around 30 years ago, Potomac have set an agenda to breathe new life into a 26-acre area. The waste materials on site include: wood; ferrous and non-ferrous metals; plastics; concrete; cardboard; tyres; and dirt suitable for use as fill or topsoil. Non-recyclables are returned to the landfill, where they now take up far less space.

At the same time, this leaves room for new construction and demolition materials to be transported 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 strictly operate construction landfill, and do not accept residential or commercial garbage.

Among the key factors contributing to the success of the operation are a track-mounted Powerscreen Warrior 1800 screen, a track-mounted Warrior 2400 – Powerscreen’s newest and most advanced dry screen – and a 20-man portable picking station.

‘It’s working out every bit as well as we’d hoped,’ explained Potomac general manager Richard Campbell. ‘We reckon 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 that 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.’

Although originally used to screen both new and mined materials in conjunction with the picking station, the Powerscreen Warrior 1800 is now being utilized to primarily to remove dirt from mined debris.

‘The Warrior 1800 is fitted with a fingered screen which is good for mined materials that have a lot of dirt mixed in,’ commented landfill operations manager William Lewellen. ‘It’s great for getting the fines out; as both incoming new debris and mined materials that have had the dirt removed by the machine are then processed through the Warrior 2400, which is a heavy-duty machine with an extra-large hopper.

‘The larger screen is also equipped with optional punch plates instead of fingers; so dirt and small materials fall through, while the most worthwhile recyclables remain. This means there is very little clogging, and any that does occur is easy to free up. Punch plates have been used a lot in Ireland and other foreign countries, but not much in the US.’

Mr Lewellen further explained that the Warrior 1800 has a standard rubber feed belt, which is fine for mined materials containing high dirt content. The Warrior 2400, however, has an optional metal feed belt, which is said to be 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 on it.

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

Screened materials from the discharge conveyor on the Warrior 2400 are deposited on to a belt that runs through a portable, 74ft long picking station with up to six large dumpsters positioned under it. Each dumpster is designated for a recyclable material: typically two for wood, two for metal, one for concrete and one for cardboard.

Depending on volume, 12 to 20 workers standing alongside the belt 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 belt at the far end of the station into a stockpile and are then removed by a front-end loader.

‘Before we bought the Warrior 1800 in 2009, we looked at various types and brands of screening equipment,’ recalled Mr Lewellen. ‘First, we tried a trommel, but it clogged far 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 and found that many manufacturers and dealers would give us a lot of information and promises about their equipment, but only Powerscreen Mid-Atlantic brought a machine in – the Warrior 1800 – 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 to 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.

Mr Lewellen continued: ‘When Powerscreen introduced the Warrior 2400 in 2010; we saw it as the perfect partner to the 1800 for our landfill operation. Powerscreen Mid-Atlantic recommended the punch plates and metal feed belt. As a result, our Warriors are efficient, dependable, and require very little maintenance.’

In 2010 Potomac produced 27,000 tonnes of recyclable materials that did not have to be landfilled. ‘We are one of only two construction landfills in Virginia that are mining old landfill materials,’ said Mr Campbell. ‘It has been incredible how well our two Powerscreen Warriors have handled the different types of materials we’ve thrown at them.’

Indeed, the Powerscreen Warrior 2400 is designed for tough service in large-scale quarrying and mining applications and 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 tonnes/h, depending on materials and conditions. The Powerscreen Warrior 1800 is a smaller, equally versatile machine designed for medium to large applications.

For further information visit: www.powerscreen.com