Most landfills use soil to cover their garbage. Even landfills that use ADC will use some soil. It's a necessary, functional part of any well-run landfill: It provides a level of protection from disease vectors, litter, and infiltration.
It's also a regulatory requirement.
From this perspective, using cover soil is a good thing. Unfortunately, like many other "good" things, if you're not careful, you can overdo it. In fact, overuse of cover soil is the single largest "unnecessary" waste of airspace and money at most landfills.
One of the main reasons that landfills use too much cover soil is tradition: "Hey, that's the way we've always done it."
A second reason is to keep the landfill looking clean: Using lots of cover soil is certainly one way to avoid getting violations for exposed waste. It's just not the most efficient way to avoid being cited.
Another reason for using too much cover soil is to justify your investment in a machine. So, the city council finally approved your purchase of a new scraper. But with it came the "unspoken" stipulation that, "OK, we gave you guys a scraper. Now you'd better be using it!"
If you're under this kind of pressure and running the scraper (or any other machine) just because you have it, you're likely wasting money. Remember: sunk costs are sunk. You can't operate your landfill efficiently if you're trying to justify yesterday's expenditures.
Make your decision for efficiency based on today's choices.
Here's a quick-look example of how much money cover soil can cost.
More than one-year (300 days), you'd spend $15,000 on soil and "waste" airspace worth $150,000.
That 'extra' soil costs $165,000 per year.
This is no small potatoes. You could prepare an acre of landfill liner for that kind of money. Or hire four or so people.
Also significant is that when you keep dirt out of the landfill, you're saving more room for trash.
The 50 cu yds of extra soil (per day)—that's just two or three scraper loads--in the example represents a small fraction of that applied at many landfills, which may use 20 or 50 or more loads of soil each day! So cutting that down by two or three doesn't take too much work. Often it's just a matter of realizing how important it is ...and of course, knowing how to do it.
This seemingly simple point —of realizing how important cover soil is—is easy to acknowledge but hard to realize.
I once was at a landfill where the site manager's main function appeared to be to save money on cutting edges. He spent oodles of time looking for good deals on cutting edges. He bought used, he bought cheap, he bought hard facing, As a result, he probably spent less on cutting edges than did anyone else in the landfill business. His efforts were successful. He was feeling smug until the day he calculated just how successful his efforts were.
The bottom line?
The total saving for the five machines that used cutting edges was $1.78 per day. That's it. All of his work to cut costs on cutting edges would barely buy a cup of coffee! By comparison, many landfills are wasting hundreds or thousands of dollars per day through the misuse of cover soil.
Over the next few weeks, we'll look at some ways to identify if you're using too much soil. We'll explore changes you can make to minimize your landfill's soil use. And finally, we'll help you to set up the tracking system(s) to make sure that your modifications are working.
Neal Bolton, a registered engineer, author of "The Handbook of Landfill Operations," and principal of Blue Ridge Services, provides operational consulting for landfills in the U.S. and abroad. He can be reached at firstname.lastname@example.org.