Landfill Manager’s Notebook: Eliminate Tracking and Dust

Dec. 1, 2011

When we think about muddy landfill roads, our thoughts often focus on getting trucks safely in-and out. Generally, we’re successful if nobody gets stuck.

But from a compliance standpoint, regulators are often less concerned about a truck getting stuck than they are about those trucks tracking mud onto public roads outside the landfill. Tracked mud, sometimes referred to as track-out, can create a driving hazard and, when it dries, can become a major source of dust. Of course, this can quickly move beyond landfill compliance into the realm of DOT and law enforcement.

So landfills go to great effort to eliminate track-out, focusing either on cleaning the trucks/tires as they exit the site, or on cleaning up the tracked mud before it becomes a big problem.

Cleaning Trucks/Tires

Mud grates, wheel-wash, or truck wash systems are used to clean the trucks on their way out.  These systems range from the low-cost, low-impact mud grates to complex, automated wheel-wash or truck-wash systems.

Mud grates (a.k.a., rumble plates or mud plates) consist of rows of metal rails placed across the outbound lane in one or more locations. As vehicles cross the grate, the tires bounce across the rails and the mud drops off. They feel much like the rumble strip along the edge of some highways. And, the larger and more aggressive the rails, the more effective they are at removing mud. 

However, they also act as speed bumps and so trucks tend to slow down when crossing them.  Often, trucks will drive around the mud grates, rather than across them. To prevent this, a soil berm, ditch, or concrete K-rail can be used to force drivers to stay in their lane.

Mud grates consist of rows of metal rails (i.e., steel channel welded together). They are often 8-10 feet wide and are constructed of 3-inch by 12-inch or 4-inch by 12-inch steel channel welded together. Twelve-inch channel allows them to be easily cleaned with a flat shovel-something that must be done regularly in order to maintain their effectiveness.

Mud grates perform well at small, low traffic sites. But, as noted, they can quickly fill with mud and lose their effectiveness. Also, because drivers will typically slow down as they approach a mud grate, very little mud is removed from the tires. What remains is then progressively removed as the truck exits the landfill and accelerates to highway speed. Overall, mud grates should be considered as one part of the solution-not all of it.

Wheel-wash or truck-wash systems are much more effective. However, they require more maintenance-especially in very cold climates where freezing is an issue.  In extreme cold, they simply cannot be used.

Of course they also generate wastewater that must be dealt with.

Wheel-wash and truck-wash systems are considered the Cadillac method for preventing track-out.

Cleaning the Exit Road

Other facilities pass on the truck/tire cleaning approach and instead, focus their effort on cleaning the outbound road. If the outbound road is gravel, a motor grader may be used to periodically scrape off the mud. On a paved road, a water truck and/or sweeper may be used to keep the road clean. 

During very wet periods, the mud may be more fluid than solid. In those cases, a sweeper is not very effective and using the water truck may create issues with surface runoff.

In those situations, consider using a squeegee. No, I’m not suggesting you heist one from a local gas station. We’re talking an industrial size squeegee. If your exit road is paved, try this: Create a giant squeegee by splitting a truck tire (lengthwise along the tread) and then bolting it between the moldboard and cutting edge on a motor grader. By leaving 3-4 inches of rubber protruding below the cutting edge, the grader operator can effectively clean mud off of a paved road.

Speed Cleaning

This is the hands-off way of removing mud from vehicles. For this to work effectively, your landfill must have a have long, paved exit road, where trucks can get up to relatively high speed before exiting the site. Otherwise they’ll continue slinging mud out on the highway.

In order for trucks to self-clean, they must reach speeds of 30 to 40 miles per hour. Of course, this is a direct conflict with safe speed limits posted at most landfills.

If you elect to use this method, you’ll also need to clean the exit road on a regular basis to prevent the tracked mud from extending onto the public roads outside the landfill.

Prevention

As an alternative to removing the mud from the trucks and the roadway, you might want to do more along the lines of prevention. Placing more gravel or rubble on the deck can help keep trucks out of the mud in the first place. Of course, there may be a significant cost associated with purchasing gravel unless your landfill is fortunate enough to receive lots of good, clean rubble or asphalt grindings.

You’ll also want to modify your operation at the unloading area so as to keep heavy equipment from tracking mud back onto the deck. Some landfills use a wheel loader to push trash to the edge of the deck, where a dozer or compactor can get to it.

While prevention may sound better than cleaning, the choice will probably come down to economics. Unless you are under a regulatory mandate to use a specific type of method to prevent track-out, most landfills choose the method that gets the job done for the lowest cost.

About the Author

Neal Bolton

Neal Bolton is a civil engineer with 37 years of experience in heavy construction and landfill operations. He recently presented a four-part webinar series, “Process Improvement for Solid Waste Facilities,” through Forester University.