In today's race toward ultimate landfill efficiency, alternative daily cover is no longer just a staple of landfill operations.

By Neal Bolton

For those in the know, the creative use of alternative daily cover (ADC) has become a yardstick for measuring the performance of landfills. Many landfills that have made the decision to use ADC are now looking at the various choices out there and asking, "How can ADC be used in the most creative and cost-effective manner?” The answer that many landfill managers are coming up with is by selecting various types of ADC based on an individual landfill's needs or goals.

Many people speak English, but few can put words together as effectively as Abraham Lincoln or Winston Churchill did. We all wear clothes, but Jacqueline Kennedy and Princess Diana set a whole new standard.

Along those same creative lines, some landfills are using the basic ingredients of tarps, films, sprays, greenwaste, and other types of ADC to cook up some very innovative and efficient combinations.

So how are those trend-setting landfills using various types of ADC to work smarter? Let's start by reviewing some of the more common types of manufactured ADC materials.

Photo: Puente Hills Landfill

Tarps
Tarps are one of the most common types of manufactured ADC and one of the most versatile. Depending on your specific wants, needs, and budget, you can choose from thin, thick, woven, non-woven, and a variety of colors including white, brown, and green.

Small tarps can be placed manually, but this method often requires workers to walk in the trash. For safety's sake that's not a good idea. Placement of large tarps requires some machine assistance. Often, large tarps are simply dragged into place by operators who see this method as quick, cheap, and easy—until they have to replace the torn tarps. A better method is to use an excavator and spreader bar to lift the tarps into place. This method is much easier on the tarps.

Perhaps the most efficient method for placing tarps is offered by the Tarp-O-Matic system. Because of this system's ability to gently place and retrieve tarps, some Tarp-O-Matic users report tarps lasting through 18 or more months of regular use.

Film
Film machines roll out a thin sheet of plastic and then trickle sand, gravel, or soil on top to hold it in place. Film is quick and easy to place, but of course you must purchase the film. If your goal is to keep workers out of the trash, maximize runoff, and avoid having to retrieve a tarp that's covered with a foot of fresh snow, you may want to consider film.

Photo: Puente Hills Landfill

Sprays
Many landfills use spray-on ADC. These materials offer great flexibility in terms of access and application. Some utilize a cement-based mix. Others may use recycled newspaper. Each has pros and cons. All sprays offer the ability to cover oddly shaped areas as easily as those cells with textbook geometry. Also, with spray-on materials, you can easily adjust the thickness of the application in anticipation of a big rainstorm or to provide extra protection for an area that you won't get back to for a longer-than-normal period of time.

Waste-Derived Material
Additionally, a wide variety of ADC materials derive from diverted waste. These include greenwaste, C&D, contaminated soil, chipped tires, auto-shredder fluff, and many more.

Similarly, if you're interested in using a waste material for ADC but don't know where to start, try contacting your state regulatory agency and ask them what other landfills in your state are using.

Trade journals, conferences, and organizations like SWANA are a good source of information on the types of manufactured and waste-derived ADC materials that are available. You may also want to check the Internet. I recently typed in the search words alternative daily cover and landfill on an Internet search engine and got 6,300 hits. There's a lot of information out there.

Or you may simply look at what's coming into your landfill right now.

A decade after the start of the California gold rush, miners in western Nevada were still looking for gold but becoming frustrated with a slate-gray muck that kept plugging up their sluice boxes and other mining equipment. Finally somebody had it assayed and it turned out to be rich in silver. The resulting Comstock Lode produced billions (in today's dollars) of riches—and it started with a material that was in the way and a hassle to deal with.

Many of the materials that we now use for ADC (i.e., greenwaste, woodwaste, chipped tires, etc.) were once perceived as problem materials.

Sure enough, when it comes to ADC there are lots of choices. But, like a person standing in front of a big buffet, the challenge is making the right choices.

We'll start by considering some of the many factors that might influence a landfill's choice of ADC:

• Ability to serve the community
• Availability and capability of a specific material
• Method of increasing recycling
• Provides lowest cost option
• Potential to develop multiple sources of revenue
• Ability to match ADC to local climate conditions
• Ability to mitigate specific problems or issues

Many of these criteria are complementary. For example, a landfill may use a certain type of ADC because it is readily available. But that same material may also provide additional revenue and help increase diversion. Medicine doesn't always have to taste bad, and, when it comes to ADC, you don't always have to give up something to get something else.

Photo: Sonoma County Landfill

Availability and Capability of a Specific Material
Frequently, a landfill will use a specific material for ADC for the simple reason that it's available. This is a straightforward and often cost-effective approach.

When we think of availability, often the first thing that comes to mind is greenwaste. For many landfills, availability makes greenwaste a logical nominee for use as ADC.

But don't run off thinking that we're simply talking about greenwaste. In fact, not all landfills have a ready flow of greenwaste. But it's likely that most landfills have something that is available and that could function as ADC. Look around at other industries in your area with your eye on by-products that might work as ADC.

Also, consider the capabilities of various types of ADC. Processed greenwaste may be inexpensive but won't do much in terms of keeping rain and snowmelt out of the landfill. If your goal is to maximize surface runoff, a film or tarp system would probably work best. However, none of these items will work very well when it comes to fire protection. It really comes down to a decision of what works best at your landfill.

Method of Increasing Recycling
Recycling is important, and being able to use what would otherwise be trash (i.e., greenwaste) as ADC makes good sense—to a point. But filling your landfill with processed woodwaste and calling it ADC is really nothing more than glorified disposal. In some cases, overuse of certain types of ADC has been a problem. Thus, the term beneficial use becomes an important measure of whether or not a material is truly being recycled.

If your landfill has more ADC material than you need, look for other beneficial uses for those materials. Some possibilities are discussed at the end of this article.

Provides Lowest Cost Combination
Amid all this innovation and creativity we must remember that business is still business—even for landfills. And regardless of what we do, it must make economic sense. Mixing and matching ADC to find the lowest cost option makes good sense.

Tom Reilly, western regional engineering manager for Waste Connections, says, "For us, tarps are the most economical ADC option. So we primarily use tarps wherever they are permitted.”

He adds, "Typically we use greenwaste as our second choice.” However, the company found that, at the landfills where there was a lot of greenwaste, there was a tendency to use it too much and end up wasting airspace.

Getting back to a typical landfill's roots, Reilly continues, "Airspace is the most valuable commodity we have, so we're making a concerted effort to save it.”

Certainly ADC is a big part of the effort to save airspace.

Staying on that track, Waste Connections is using various other forms of ADC. For example, at one of its landfills, it is using processed construction material (i.e., shingles). This not only provides another ADC option, but also helps the local county's diversion effort.

Potential to Develop Multiple Sources of Revenue
ADC is most often used because it saves airspace and may cost less to place than soil. But remember that economics works both ways, and for most folks, while saving money is good, making money can be even better. Yes, in many cases, ADC can also generate revenue. And, even in cases where the fee charged for these materials is less than the landfill's normal tipping fee, the added benefit of increased diversion and avoidance of state disposal fees can help make up the difference.

Some landfills, especially those with a soil shortage, are looking for customers with waste materials that can be used as ADC and also generate revenue. It's likely that many of the materials now used for ADC might never have been tried and approved if it weren't for their ability to generate revenue.

Can this cause misuse or abuse of ADC? Sure. A few landfills have sometimes used excessive amounts of ADC—particularly greenwaste—to increase perceived diversion and avoid waste disposal fees. But in most cases the value of airspace is the check that keeps ADC use in balance.

As you attract more ADC, check your permit to make sure that your total tonnage received (Waste + ADC) doesn't violate your permit. Depending on your permit and the situation, ADC tons may be counted right along with disposed waste tonnage.

Ability to Match ADC to Local Climate Conditions
Regardless of what type (or types) of ADC you decide to use, be sure that it meets the needs of your landfill.

In Fort Collins, CO, Stephen Gillette, director of solid waste for Larimer County, says that "Topcoat [a spray-on material manufactured by Central Fiber Corporation] is our preferred form of ADC.”

Larimer has been using it for three years. It was selected because of its ability to hold up in the high winds common to the county's landfill. While the landfill closes when the winds exceed 30 mph, the ADC must stay in place. "It has worked well for us,” Gillette says, " even through a recent period of 70-mile-per-hour winds.”

He explained that they also reviewed film and tarps but felt that the winds would create problems for those materials.

Larimer County selected Topcoat based on cost, convenience, and its ability to stand up to the windy conditions at the landfill. Another benefit is that the mixture doesn't set up like some other spray products. Gillette goes on to explain, "We mix up a batch prior to going to the landfill, and if it's not all used that day, we use it the next. We keep it in the shop so that freezing isn't a problem.”

Asked about the cost of the material, he notes that "it uses recycled newspaper, and as paper prices go up, so do our material costs. But on the other hand, our MRF also generates more revenue as the paper prices go up, so it all balances out.”

Larimer also utilizes crushed glass (from its MRF) as ADC. Gillette notes, "We mix the crushed glass with soil because there are some homes in the area and we don't want the glitter.”

Regardless of what type of ADC it uses, the Larimer County Landfill is required to use soil every fifth day.

This requirement to use soil every several days does not stop the creative flow of some landfills. For example, at one county-owned landfill, greenwaste was historically used as ADC. However, it is also required to periodically cover the waste with soil. The problem was that the landfill had a serious soil shortage. How did it respond? On the soil days, it would first cover with greenwaste, then with soil. A waste of time, you say? Not for the landfill. By placing a layer of greenwaste before placing the soil, it was able to easily strip and remove virtually all the soil when it came time to move back into that area and place the next lift of trash.

As a result, it used ADC, wasted very little soil, and still met the regulatory requirements for cover.

Photo: Keifer Road Landfill

Alternatives for Alternative Daily Cover
There are only 26 letters in our alphabet, yet it's estimated that the English language contains over 3 million words. With the wide variety of ADC materials available today, it's likely that new, creative combinations will continue to appear as the landfill industry develops.

Greenwaste
If you want to get more out of the ADC options available today, look around your landfill, even to the point of looking beyond ADC. For example, consider processed greenwaste. For some time now, landfills have justified the purchase, lease, or periodic contracting of a grinder to process greenwaste for composting and, of course, use as ADC. However, there are many other beneficial uses for processed greenwaste.

Many landfills utilize processed greenwaste as ground cover, as erosion control, and even as a soil amendment that can be tilled into a lifeless soil to help develop usable topsoil.

Wood chips and processed greenwaste are also used by savvy landfill managers to provide temporary repair for a muddy road or tipping pad. If you haven't tried this yet, you might be surprised at how well it works.

For landfills in the northern states where soil freezes, making excavation of cover soil difficult, consider placing shallow soil stockpiles on top of the landfill and then cover them with a few feet of processed greenwaste. The heat of the landfill and insulation capabilities of the greenwaste may help keep the soil thawed.

Manufactured ADC Products
Is spray-on ADC limited to covering trash? It certainly is not. I've talked with several landfill managers who also use their spray machines as hydroseeding machines for applying seed, fertilizer, and mulch.

Sprayed materials can also be used to help stabilize soil stockpiles or ditch banks and minimize erosion.

Tarps and/or film could also be used for much more than ADC. Consider the benefits of covering a soil stockpile so you can always have some dry soil available for cover, even during the wet season. This can be extended to include contaminated soil or other materials that could cause problems with surface water if left uncovered.

Bill Glick, western regional sales representative for Tarp-O-Matic Inc., notes that they have even installed a permanently mounted system to cover a transfer pit at a C&D landfill. During the day, vehicles dump in the pit and an excavator loads out to trucks, and at the end of the day, the entire pit is covered with a tarp.

Finally, it's important that we get past the limitation imposed by the name alternative daily cover. The fact is many landfills are using these alternative cover materials to provide waste coverage for a week, a month, or even longer. There are a variety of issues that landfills have to address before gaining approval from local regulators to leave ADC in place for extended periods of time. These include the ability of the specific ADC to

• provide fire protection;
• prevent infiltration;
• minimize odors;
• control litter;
• prevent or discourage vectors; and
• look clean and sanitary.

And, while the only thing that works just like soil is soil, for some situations certain types of ADC may perform much better than soil. It's usually up to the landfill manager to find the best solution and make the case to the regulators.

The wide selection of ADC options available to landfill managers offers a lot of creative opportunity. If you're still looking at ADC as putting a round peg in a square hole, maybe it's time to drill out the hole or whittle down the peg. More than likely there is some ADC combination that can work for you.

Neal Bolton is a consultant specializing in landfill operations and management. He is principal of Blue Ridge Services in Atascadero, CA, and author of The Handbook of Landfill Operations.

MSW - March/April 2005