Landfill Manager’s Notebook- Basic Operations: Push, Pack, and Cover

It’s funny, you know, how much emphasis we put in to tracking our landfill’s airspace consumption rate-but how little understanding we have of the basic components that control it. When it comes to the technical side of the equation, we have surveyors, engineers, and financial folks who follow proven, accepted procedures for designing landfills, measuring airspace, and managing money.

We come up with detailed reports on in-place density, effective density, airspace utilization factors, compaction ratio, waste compaction density, and cover ratio. All of which are critical benchmarks of landfill performance. They are so critical, in fact, that your landfill’s tipping fee, your salary, your bonus, even your career may hinge on these numbers.

But after all of this effort and scrutiny, we defer the task of doing the work to a black box called operations.

Now, I’m not criticizing landfill operators or supervisors-not by a long shot. I generally find that the folks with the boots and hardhats know their job-and do it well. But I also find that doing it well from one perspective (say, with a focus on clearing the deck quickly to minimize truck wait time) may not be the same perspective that makes for efficient use of airspace.

“Hello, Command Center, this is Landfill: What is the mission?”

Your operations team needs to know what is expected of them-They need a goal. And it’s the landfill manager’s job to set one.

In this economy, with tonnage and revenue down at many landfills, a common goal is to reduce operating and capital costs. But don’t do this by ignoring basic equipment maintenance or cutting operational corners than can actually hurt your bottom line. Instead, do it through increasing the efficiency of your operations, conserving airspace and maintaining regulatory compliance.

There’s little surprise that most of this comes down to the basics of: Push, Pack, and Cover. Let’s take a look.

Push
Pushing trash from where it’s dumped to the active face is a very simple process. So simple we forgot to ask.

Well, OK, it’s really not so simple after all. The machine doing the pushing-usually the dozer operator-must be able to look backward…and forward. What type of waste and how much of it has been dumped on the tipping pad? And where and when should it be pushed in order to fit into the compactor operator’s plan for the daily cell? What have you got…where should it go?

The concept here is that the compactor operator is building something. He or she is constructing a cell. And every load of trash needs to go in the right place at the right time. Otherwise, we make a mess and fail to get the best possible compaction.

The landfill crew-including the spotter, if present-should make a plan, communicate it throughout the day, and work together. And in the midst of that plan, the pusher must be working efficiently.

Here’s a bit of landfill trivia, something learned from conducting a great number of time-motion studies on basic landfill operations. The process of pushing, spreading, and returning will typically take about a minute. And on average, a D8-size bulldozer can push 7 tons of waste with each push. Do the math. That works out to 420 tons of waste per hour. Yep, your dozer has a maximum production rate of around 400 tons per hour.

The next questions are How many tons per day does your landfill receive? and How many hours per day is your dozer working? If your operation is typical, your dozer is spending no more than 25% of its time on production pushes…and the remainder of the day on other “non-value-added” activities.

Don’t believe it? Run your own numbers. But don’t feel bad. This is a good thing. It’s good because it means you have lots of room to make your operation more efficient and save money.

Pack
Forty years ago landfill compactors were rare. Today, they are commonplace. But we still sometimes miss the big picture. The goal is not just to have a landfill compactor: It is to achieve optimum waste compaction. The first sounds right-the second is right.

To achieve optimum compaction, you must have a compactor, have the right compactor, and know how to use it effectively.

There are those people in the industry who know the importance of compaction…and then there are people who actually know compaction.

Jim Caron is one who does. As president of the Caron Compactor Co., he has probably visited more landfills than anyone else on the planet. From a humble start in the late 1960s, when he and his father, Fred Caron, developed the first prototype of the Pactor, Jim’s career as a compaction expert spans nearly 44 years. And during that time he has visited well over 1,000 landfills.

Caron’s company developed the first conical landfill compactor tooth for use on the Kruncher, a pull roller developed around 1970. That same Caron tooth was welded on a Caterpillar 816 in 1972. The

conical tooth style, developed in 1970, has become one of the most common patterns in the waste industry-now used by virtually all compactor wheel manufacturers.

If you want to achieve the highest possible compaction, you too must study compaction. Here are 9 important things to consider:

Pre-pack underlying trash– Before placing the next cell, strip off the previously placed cover soil…right down to the trash-and then run the compactor on that old, underlying trash. Chances are it will be wet and very compactable. Gain some compaction before you even start placing more waste.

Place thin layers– Place all trash in the thinnest possible layer. The type of waste will dictate how thin you can place it, but in every case, thinner is better.

Work flat– Work your compactor flat. It’s easier on the machine and the operator, but more important: It will move faster. This can translate into hundreds of thousands more tooth penetrations per day.

Cross-roll– Trash is not homogeneous. Items will frequently bridge and prevent thorough compaction. By cross-rolling (shift your direction by 90 degrees), you’ll minimize bridging and increase compaction density.

Make long runs– As your compactor works, it will constantly be changing direction: back-and forth…back-and-forth. At every end, it must decelerate, stop, and then accelerate. By setting up the size of your cell to provide longer runs, the compactor spends a greater percentage of time compacting…instead of starting and stopping.

Forget pass counting– It’s true that multiple passes with the machine are necessary for optimal compaction. But the ideal number of passes varies as much as the wastestream. The compactor should work each and every portion of the cell to the point of diminishing return, where additional passes are not producing additional density. Pack it “˜til it’s tight.

Read the trash– Become a student of your wastestream. Every landfill has a unique wastestream, and it varies from day-to-day and even from hour-to-hour. Pay attention to when certain types of trash come in and modify your compaction method to fit the trash.

Look for moisture– One of the most important aspects of reading the trash is to look for wet loads. Being able to mix wet loads with dry paper/cardboard loads is a very important skill, one that if done properly can increase your compaction rate dramatically. Paper and cardboard simply packs better when wet.

Use good teeth– Finally, don’t forget why you purchased a compactor in the first place. It’s the teeth, baby…the teeth. As a general rule, you want a wheel with big teeth-and lots of ’em. Unlike their cousins that work in the soil, landfill compactors do not “walk out” of the trash. That’s because the teeth achieve full penetration with every pass. So more teeth means better compaction. But don’t forget that teeth wear out and have to be replaced. Savvy landfill operators know that robust teeth pay for themselves over and over.

Cover
“…operators of all MSWLF units must cover disposed solid waste with six inches of earthen material at the end of each operating day…” So reads the cover material requirements of the EPA’s Subtitle D, the mother of all landfill regulations.

Daily cover is an operational standard that applies to virtually every landfill. But it’s also the single most costly aspect of most landfills. There is no such thing as 6 inches of daily cover soil. I’ve been measuring landfill efficiency for more than 30 years, and I have never seen a landfill that can cover MSW with 6 inches of soil. Because of the roughness of the trash surface, imperfect grading, and many other factors, it simply takes more than 6 inches. In my experience, the average depth of cover soil required to effectively cover trash…is 16 inches.

That depth of soil, placed across the entire cell every day, amounts to a tremendous loss of airspace, not to mention the cost of excavation, transportation, and placement.

This is why most landfills use one or more forms of alternative daily cover (ADC). And if your landfill isn’t on the ADC train, check it out. You’ll find that the savings far outweigh the cost.

Streamlining your operation takes work, but it isn’t rocket science. It’s just a matter of basics.