You might be surprised to learn that while the basic attraction of ADC–its ability to save airspace–remains in terms of material and methodology, ADC has continued to mature. There are more options today than ever before.

By Neal Bolton

Regulatory Issues
Getting Back to Basics
Priorities Are Changing
Recommendations for Regulatory Change
The Bottom Line

If you’re running a typical landfill, chances are you’ve been using alternative daily cover (ADC) for a few years now. Perhaps you even experimented with several different types of ADC before finding the one (or ones) that works best for your operation. But now the honeymoon’s over, and using ADC is just part of the daily grind.

It’s like buying a new car. At first, you wash it twice a week and threaten the life of anyone who dares to think they can actually eat in it. But after a while, the shine wears off, and it becomes a chore to even pump gas.

It’s difficult to tell precisely when it happened, but at some point your ADC program lost its "new car smell." Now it just smells like … well, like everything else at the landfill.

For all of those landfills out there stuck in an ADC rut, listen up.

The list of ADC materials now includes not only manufactured products, such as tarps, film, and spray-on material, but also an ever-increasing arsenal of diverted wastes. In addition to the more common things, such as shredded woodwaste and greenwaste and petroleum-contaminated soil, some landfills are using chipped tires or unprocessed yardwaste (it’s just spread on the slope and track walked).

Some coastal landfills even suggest that seagulls be approved ADC. But alas, at this point in time, no regulators have approved that method.

As confusing as all these choices might be, the benefit of having more options is that landfills can now, more than ever before, customize an ADC program that meets site-specific needs. For example, you can now add aesthetics to your ADC selection criteria.

Far from being scientific, or even performance-based, some landfills require ADC to meet certain aesthetic criteria. To meet this need, AMCON developed two new ADC tarp colors (sand and olive green). In an industry where both out-of-sight and out-of-mind are good places to be, using an aesthetically pleasing tarp is one more step away from a snow-white tarp that announces, "LANDFILL HERE!"

Naturally, some of those changes are a result of a competitive landfill industry demanding competitive ADC options. Many of these changes are economic and directly translate to a better bottom line.

It is said that necessity is the mother of invention. So it’s not too surprising to find that where landfill operators find it necessary to save airspace, they will invariably invent new ways to do it. But it might surprise you to know, especially in an article about ADC, that some landfills use less soil and save airspace–without using ADC. At least without using it in the traditional sense.

Yes, many landfills that operate 24 hours per day are not using ADC to cover the face at all, because regulations that require waste to be covered at the end of each operating day don’t apply too well to landfills where the operating day never ends. At around-the-clock landfills, cell construction might start on Monday and end on Friday or Saturday. So aside from a small amount of soil or ADC used on the top and side, the cell is only covered once per week.

Also, as ADC use increases, and as landfill operators and landfill regulators become more knowledgeable about ADC, things aren’t as black and white as they used to be. Something that looked simple in theory has now, in practice, become more complicated.

What criteria must ADC meet in order to be suitable at a specific landfill? Do typical ADC materials always work as a satisfactory replacement for 6 in. of soil? And, when it comes to that, what the heck is the purpose of 6 in. of daily cover soil anyway? Finally, is it realistic to assume that every landfill can (and should) be using ADC?

The answers to these kinds of questions must be addressed from a regulatory, operational, and economic standpoint.

Regulatory Issues

From a regulatory standpoint, there are a number of issues that can impact a landfill’s ability to use ADC.

Conflicting Regulations

Is it possible? Can the words "conflicting" and "regulations" be used in the same sentence? Of course.

For example, in many rural areas in California, residents are required to clear a 50-ft. fire break around their homes, removing all flammable vegetation. But because one area was also home to an endangered species of mouse, another agency’s regulations would not allow those residents to cut or remove any native vegetation. In those situations, the residents often found themselves in a regulatory bind, stuck between a mouse and a brush fire.

The same thing can happen at landfills. Many landfills are required to reduce the amount of "waste" they bury. One of the primary ways to do this is to divert and/or process material that might otherwise be "waste" into a usable ADC material. In states that have set aggressive recycling goals, ADC provides a valuable opportunity to obtain diversion.

Here’s how it works: Suppose that certain materials (e.g., greenwaste) come into the landfill. If it is buried, it’s classified as waste. If it’s set aside and used as ADC, it’s classified as diverted (recycled) material and the landfill gets credit for diverting it. Does this conflict with the original purpose of ADC, which was to save landfill space? Depending on whom you ask, it might.

For example, in California there is much discussion in the landfill industry regarding abuse and overuse of ADC. Some folks contend that landfills are using too much ADC, going well beyond the task of covering garbage, simply to boost diversion numbers. At the same time, however, others argue that in order to be equivalent to daily cover requirements (6 in. of soil), some types of ADC (e.g., shredded woodwaste) need to be thicker than 6 in.

Complicating matters (as if they need to be more complex), the California Integrated Waste Management Board (CIWMB) preapproved many types of materials for use as ADC. But some of these materials, while approved by the CIWMB, might not be approved by other regulatory agencies (the Water Quality Control Board, Fire Department, and so on).

Is California the only place where regulations can conflict? Unfortunately, no. Landfill regulators everywhere are trying to get a handle on ADC. As a result, landfill operators sometimes see ADC compliance as a moving target.

No Set Standards

Another problem related to ADC is the lack of industrywide standards. What’s acceptable at one landfill might not be acceptable at another. This creates a difficult situation for landfill operators, especially those who operate multiple landfills. This also creates a problem for ADC manufacturers who try to market specific materials to a wide range of landfills.

Unfortunately, developing consistent statewide or even national standards isn’t as easy as it sounds. Remember, cover soil and ADC are supposed to help protect human health and the environment. At first glance this sounds simple: We need one set of goals for all landfills. But by necessity these items are prioritized differently in different parts of the country.

At remote landfills, an ADC material’s ability to control litter might be less of an issue than it would be at a landfill surrounded by a residential development. Perhaps at a remote landfill, fire prevention is more important. Or in areas that receive lots of precipitation, ADC selection might be based more by its ability to shed water than by its ability to prevent flies.

These and myriad other issues create difficulties for those who manufacture, use, and regulate ADC.

Regulator Vs. Operator

Forget idealism, let’s get real. Operators and regulators look at things differently. This doesn’t mean that one is right and the other is wrong. It’s just that when you have one side setting the standards and the other side paying to implement the standards, there will be conflict. Go figure.

Sure, with effort from both sides, it need not be a major problem. But in some cases, the communication gap can make the Grand Canyon look like a ditch.

If you’re a landfill operator, using ADC is a good thing. It saves money. It saves airspace. It’s a no-brainer. But for a regulator, approving a landfill to use ADC could mean more work in terms of watching, testing, and monitoring the performance of various types of ADC material. There is also an increased risk. If a problem develops with a certain type of ADC, the regulatory agency might share responsibility; after all, it gave its approval! And that’s the upside.

On the downside, allowing a landfill to use ADC might increase the potential for a "problem" landfill to have more problems. In fact, I’ve talked with regulators who said, "We haven’t approved ADC for certain landfills because historically the landfill hasn’t even been able to properly cover with soil. If we approve the use of ADC, it will just further complicate our ability to regulate the landfill."

Getting Back to Basics

Amid all the issues surrounding ADC, it’s important that we don’t forget why we’re using it in the first place.

My grandfather used to talk about what it was like growing up on a ranch in New Mexico in the early 1900s. With no refrigeration, they kept their perishable food (meat, milk, and so on) in a "cool house." The cool house was in fact a small sod building kept cool by running water pumped by a windmill through a trough that ran along the inside walls before finally flowing outside to the cattle watering trough.

Thus cooled by the well water–around 50°F, even in summer–their cool house provided the luxury of refrigeration, even 90 years ago. But to keep their food cold, there was one requirement: They had to live beside a windmill.

Fortunately for most of us today, refrigeration is something we can take for granted. If your neighbors said, "We just built a windmill in the backyard so we can keep our food cold," you’d think they were crazy–and they might just be. The fact is, we don’t need windmills and well water anymore to keep food cold. Things have changed.

By the same token, we need to keep an eye on the changes that have occurred in the landfill business that relate to the practical use of ADC. Are we judging different types of ADC based on current reality, or are we building windmills where we don’t need them?

To answer these questions, let’s get back to basics. What is the purpose of daily cover anyway? It should help prevent fires, litter, vectors, infiltration, odors, and so on, as should ADC. The question is: How has our industry changed in regard to these issues? And are the traditional priorities we’re accustomed to as important as they used to be?

Prevent Fires. Sure, 6 in. of cover soil can help prevent the rapid spread of a landfill (surface) fire. And if a large area of the landfill is covered with wood chips or other flammable material, a surface fire could spread quickly. But today landfill fires aren’t as common as they once were. Part of the reason is that an ever-increasing percentage of the wastestream is passing through a transfer station or MRF before it goes to the landfill. Waste screening (load checking) efforts also help prevent landfill fires by keeping "hot" loads (i.e., BBQ or fireplace ashes) out of the landfill. As a result, for many landfills, fire concerns have dropped a few notches on the priority scale.

Another issue is fire control for subsurface landfill fires. In my experience, I find this to be a big issue with many regulators. Certainly ADC materials removed daily provide no internal fire protection. Nor would flammable materials, such as shredded woodwaste or chipped tires, do much to stop a fire. In many cases, however, the "textbook" image of the landfill’s interior being made up of parallelogram cells, each with a nice 6 in. of daily cover, is false. By the time the dozer or compactor finishes pushing, spreading, and compacting today’s waste up against yesterday’s slope, the 6 in. of daily cover that was once in place has been scattered and lost. The inside of most landfills comprises a mixture of waste and soil, with the emphasis on mixture.

Prevent Litter. Yes, 6 in. of daily cover soil, if applied promptly, can help prevent litter. But at many landfills, recycling continues to reduce the amount of paper and plastic going to the landfill; hence, less litter. And when it comes to litter prevention, most types of ADC work just as well as cover soil.

Landfill operators are a creative group. Where a 24-hour landfill might use less ADC to save airspace, another landfill might use more ADC–to prevent litter. For example, some landfills have found that a light sprinkle of foam applied periodically during the day helps tack down blowing litter.

Prevent Flies. It has been shown through various tests that fly larva cannot emerge through 6 in. of daily cover soil. These tests are in fact the basis for our 6-in. daily cover soil standard. But again, in most cases, whether or not a landfill uses ADC doesn’t seem to have much impact on fly concentrations.

Infiltration. Reducing infiltration and promoting runoff are often on the list of benefits provided by daily cover soil. But under close inspection, how well does daily cover soil perform in this regard?

Daily cover soil is seldom impermeable. Thus, in terms of preventing infiltration, it’s only purpose is to retain as much moisture as possible (up to its field capacity) and then discard this moisture via evaporation or evapotranspiration. In this regard, some types of ADC (e.g., shredded greenwaste) can likely hold more water than soil.

Also, because it is often loose, roughly graded, and porous, daily cover soil doesn’t shed water very well. In fact, when it comes to promoting runoff, an ADC tarp would do a much better job.

Prevent Odors. Daily cover soil can help prevent landfill odor, as can many of the more common ADC materials. But when it comes right down to it, how many landfills have a nuisance odor problem that would be solved by daily cover soil but not by ADC? Chances are, not many.

As far as that goes, isn’t it likely that those particularly smelly loads could be covered faster–and perhaps more effectively with foam than with soil?

Priorities Are Changing

There are many other reasons why landfills must place 6 in. of daily cover soil. But I would propose that in recent years there has been a shift in priorities. We are seeing some traditional landfill issues (e.g., fires, flies, odor, and litter) being shadowed by the much larger issues of airspace conservation, recycling/diversion, and aesthetics.

Does this mean we don’t care about landfill fires anymore? Not at all. But in terms of the bigger picture, they aren’t the common problem they once were. The same holds true for many of the other reasons why we have used 6 in. of daily cover soil.

As individuals, as professionals, as an industry, we need to adjust our "whys" and "hows" to line up with today’s reality.

Recommendations for Regulatory Change

Is there hope? Can landfills expect to solve the problems of inconsistent standards or conflicting regulations? Can we successfully focus on the current priorities? Yes, but not necessarily through more regulations.

It’s likely that trying to establish consistent state or even national ADC standards is not the total solution. In order to work, such rules would have to be very broad and flexible. Thus, by their very nature, they would require lots of interpretation by local or regional regulators. Here we are back to fuzzy, unclear standards.

The fact is, much of the burden for establishing standards lies with landfill operators. These are the folks who will have to decide which types of ADC are economically feasible and which ones aren’t. Once this is defined, manufacturers and regulators will do their respective best to meet industry needs and affirm that specific types of ADC successfully meet daily-cover standards.

With this in mind, the solution needs to be developed on a site-by-site or perhaps regional basis. Because what works in Omaha might not work in Seattle, or Phoenix, or anywhere else.

We are even now in the midst of this process. Individual landfills across North America are, through trial and error, finding the best ADC solution. Sometimes it’s hard to tell if it’s more trial or more error. But through this process, they’re finding what works best for them.

And in nearly every case, manufacturers are stepping up to the plate with appropriate products and regulators are fielding whatever comes their way. But again, the key is that the landfill operators are the ones who must decide what works for them.

The Bottom Line

From an operations standpoint, landfills that use ADC must juggle a variety of issues. These almost always include airspace savings, ADC cost, climate, ease of deployment, regulatory approval, and in some cases even aesthetic acceptability. When it comes to implementation, however, every landfill will have a unique, site-specific ADC program.

It’s one story, with many different interpretations. It’s like this:

One night my wife and I were reading to our kids the story about the princess and the pea. It’s the story of a young girl who shows up at the castle on a cold and stormy night. She tells them she’s a princess, but rather than take her word for it, they decide to give her a test. To prove she was indeed a princess, they had her sleep on top of 20 mattresses under which was placed one small pea.

The next morning she said she hadn’t slept a wink all night because the bed was so bumpy. This proved she was a princess. Obviously, the point of the story was that princesses are so very delicate and sensitive, they can feel a small pea, even through 20 mattresses. It was a very simple story. We all heard the same words. One would expect that we’d all reach the same conclusion.

By the time we finished the story, however, one of our boys (who was 3 years old at the time) had a serious frown on his face. When we asked him how he liked the story, he replied, "The story was OK, but it wasn’t very nice of that princess to pee in her bed."

It’s like that with ADC. We all might hear the same story (or have the same ultimate goals), but there will have to be different interpretations for every landfill.

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