Investigating the Cover-Up

What do you use as an alternative daily cover (ADC) on your landfill? Many operators swear by tarps, while others prefer foam, spray-on slurry mixtures or degradable plastic film.

Most continue to use dirt to supplement commercial ADCs. Some supplement commercial ADCs with green waste, auto fluff, chopped up tires or other material that can be called "recycled" and counted toward diversion goals.

An operator's take on what makes a good ADC depends upon philosophy, site characteristics, availability, state regulations, labor concerns and costs.

In short, with so many options, one operator's nightmare may turn out to be another operator's ideal solution.

"I visited a landfill using degradable plastic, and it was an operational mess," reports one manager. "Seagulls cut through the plastic to get to the refuse. Standing water lay on top. The deployment methods were clumsy. I can't believe it's cost effective."

Nevertheless, John Steward, disposal supervisor of the Sonoma County Central Landfill in Petaluma, Calif., has been using degradable plastic film supplied by EPI Environmental Products Inc., Conroe, Texas, since 1996 with great success.

"We're hooked on plastic," he says. "We lease the application machine at a nominal rate and buy $250,000 worth of plastic a year." According to Steward, the plastic film costs less than paying to excavate and move dirt.

More importantly, the film preserves airspace, a particularly vital concern at Sonoma Central, which has only 20 acres and one to two years of airspace left.

Steward investigated foam, but believes that the heavy rains and winds characteristic of the region would make application difficult.

But rain and wind will affect plastic as well, won't they? Not as badly. The application machine supplied by the manufacturer lays the plastic down and simultaneously drops rows of sand ballast along the length of the cover.

Like most operators, Steward does not believe in a single ADC solution. He sees plastic as a way to cut down on the use of dirt, which he continues to use on the sides of his three-to-one slopes. "We feel the dirt gives a better appearance to the site," he says.

According to Steward, before turning to the plastic film, dirt was consuming about 12 percent of the facility's airspace. Film has cut that in half. Further reductions in dirt come from green waste, which Steward also uses as a daily cover.

"It's not as good-looking as the plastic, and it doesn't hold up as well," he says. "I've had plastic on for two weeks at a time with no problem. I have to re-cover the green waste almost every day."

Why Not Use Tarps? "I'm thinking about trying tarps," Steward says. "But I'm a little worried about how they will work in the wet and windy weather we have here. But we're going to look into it. I think the more options you have available, the better the job you can do."

For many operators with fewer weather concerns, tarps provide the answers to the most pressing daily cover questions: They save airspace, and they don't cost much.

Marlin Yarborough of Airspace Saver Daily Cover, Prairieville, La., says that the majority of landfills using ADCs use tarps. Joe Morse, operations supervisor of Waste Management's Kirby Canyon Recycling and Disposal Facility in Morgan Hill, Calif., is one of them. However, while he relies mainly on tarps, he also uses limited amounts of treated, shredded auto waste and shredded tires.

"Recycled ADCs generate revenue," he says. "Because I use them for cover, I also can divert them and don't have to pay city tax. But I can't charge my full $50 gate rate for those materials, and they take up airspace that's worth $50." Morse does get the full gate rate for green waste, which he uses on the front face of the current fill site, but green waste shows up in small quantities.

However, without proper management, tarps can run up labor costs. Proper fill sequencing and tarp management play a big role. "I'm open six days and closed on Sunday," Morse says. "By the end of the day on Saturday, I have to close out 100 percent, and I can't afford to come in Saturday morning with a couple acres of tarped garbage."

Morse takes in about 1,700 tons of refuse daily and about 10,000 tons weekly. He sequences the daily fills in a way that lets him use no more than four to five tarps.

"We'll fill a square area on a Monday and put soil across the bottom line of that square and two tarps across the inside face," he says. "On Tuesday, we'll move those two tarps across to the outside face of Tuesday's fill, and lay two more tarps down along the bottom line of the fill. So, there are four tarps deployed on both sides of Tuesday's work."

Throughout the week, Morse chases his new garbage with the tarps and backfills the open areas with soil. As green waste shows up, he stockpiles it. When there's enough, he lays it down for a daily cover, pushing the tarps farther down the row. The point is, he must end up with no more than a sliver to close out on Saturday.

"We do this with five operators and myself," Morse says. "I don't have a full-time dirt crew. We're all pushing garbage, handling new construction, and everything else. So, we have to sequence right and keep rotating the tarps.

"If you have a facility with 10 operators, you might be able to use six or eight tarps, wait until Friday, yank all the tarps, and cover everything with soil."

Morse deploys his tarps with existing equipment instead of a deployment machine. "Operationally, I could justify the expense of a deployment machine," Morse says. "One laborer could run it, and the tarps would probably last longer - eight months instead of the three months I get now.

"On the other hand, tarps deployed by machine don't have ballast chains around the edges," he says. "We have high winds here, and I need ballast. I don't want to waste time throwing tires down every night."

Foamy Solutions At the City of Bethlehem Landfill in Bethlehem, Pa., Rusmar Inc., West Chester, Pa., foam ADC saves airspace and also solves a labor problem that can accompany tarps.

Airspace is the key problem for Bethlehem. The site was repermitted in 1993 for 2.5 million cubic yards.

The city then undertook an aggressive construction project, costing $8 million to close a 50-acre segment of the site, $9 million to build new cells, and $2 million for a new leachate collection system and an abatement pumping system for previously unlined areas that had developed pollution problems.

After borrowing nearly $20 million, the city got caught in a competitive war that lowered prices to about $42 a ton on average. It turned to ADCs with the goal of preserving as much $42 airspace as possible. Both tarps and foam were candidates.

"About two years ago, we did a demonstration project with tarps," says Chris Campman, manager of operations. "We were happy with the tarps, but they cost a little more for labor."

It takes about 20 minutes to apply foam at night and about 20 minutes to lay down tarps, he says. "In the morning, you can fill right over top of foam, but you have to remove the tarps which takes about 10 minutes," he says.

Foam requires specialized application equipment, but the sale was structured to include the equipment's price in with the price of the foam. "Foam costs us about 54 cents a pound, and we use about 200 pounds a day," Campman says. "That comes to just about $100 a day."

Because of the special needs of a balefill, the Monmouth County Reclamation Center in Tinton Falls, N.J. also uses foams. The first 20-acre cell of a 100-acre site opened in the fall of 1997. "We're going for the lowest possible airspace consumption possible," says Superintendent John Gray.

"Everything we put into this site is in a high-density, tied bale," he says. "Based on our airspace requirements and the way we stack the bales, we decided to use foam as a daily cover for the vertical face and soil as an intermediate cover on the top of the stacks."

Gray's crew is working a three-to-one sloped vertical face, with staggered steps created by the square bales of refuse. The steps create voids on the vertical face, which if filled with a dirt daily cover, would waste both dirt and airspace.

"Airspace savings and labor savings are the benefits [of foam]," he says. "In terms of cost, dirt and foam seem to be about the same. But dirt also uses airspace."

Creating a Shell At the three-year-old 1,300-acre Atlantic Waste Disposal landfill in Waverly, Va., Director of Operations Jerry Johnson has opted for a spray-on-slurry made of cement type mineral binder called "Posi-Shell," which is supplied by Landfill Service Corp., Apalachin, N.Y. This ADC hardens upon application and breaks up when new trash is dumped on top the next day.

It's similar to foam in terms of application, but different because it is more permanent, Johnson says. "You can leave it for 30 to 60 days with no problems, or you can break it up and put waste back on top. It costs between 60 cents and 70 cents a yard, for everything: labor, the material, and the application equipment."

Johnson says this type of ACD reduces odor, doesn't attract birds and resists wind. Also, he has found that he can use the applicator to spread grass seed, which is used for erosion control on the landfill's slopes.

For landfill operators investigating the best way to run an ADC cover-up, there is no single answer. ADCs come in many different forms, and one, two, three or more will eventually solve the weather, labor, airspace, and cost problems characteristic of your particular landfill.