Previously, we talked about litter control at landfills. And while litter control is an integral part of managing any landfill, in this article, we are going to take a step back and talk about preventing litter in the first place.
What I’m talking about is developing strategic fill sequence plans that provide sheltered fill areas you can work in during those particularly windy days when most litter is generated. In some cases, this may be as simple as maintaining a pocket that is lower than the rest of the landfill, a protected zone to which you can retreat on those especially windy days. Some landfills have topography that makes this possible; others do not. Landfills that do not have an obviously protected zone would need to create one.
Here is an example: in many Northern climates, blowing wind means drifting snow. Just like litter, you can’t necessarily stop the snow from blowing or from moving when the wind blows. However, by strategically placing the snow-drift fences, you can control where the snow drifts.
Often, we will see snow-drift fences that are set up several hundred yards off the edge or away from an interstate highway, the idea being that the snow should drift away from the highway rather than on the highway.
The thing about these fences is that they don’t catch the snow. If they are properly designed and constructed, they create a calm zone downwind of the fence where the wind velocity drops almost to zero, thus allowing the snow particles to fall to the ground and accumulate. The length of the calm zone can extend up to 15 times the height of the fence, which means a 10-foot-high snow-drift fence could create a drift that extends up to 150 feet downwind of the fence.
Now imagine using the same concept to deal with landfill litter. You would essentially create a wind-lock behind which you could operate the landfill while protecting the active face from the effects of the wind.
Some landfills have effectively done this by purposely constructing soil berms or erecting what are, in effect, snow-drift fences. For the most proactive landfills, these things are integrated into the annual fill sequence plans.
The key is to integrate these types of setups into your fill sequence plans so you have an adequate protected zone that you can move to at any point in time when required due to heavy wind.
Some of what we’ve learned comes from conducting CORE Assessments, where we drill down into the details of the operation. In other cases, we have conducted dedicated wind/litter studies to specifically improve litter control systems.
But, despite the tremendous benefits that come with experience and practice, there is still a major component that comes back to engineering. Litter movement does, in fact, follow some basic laws of physics.
We should note here that while we’re talking about landfills, these concepts apply directly to transfer stations, convenience centers, MRFs, organics-processing facilities…and anyplace else where litter can blow.
The steps outlined below are how we develop an optimized landfill sequence plan that directly addresses litter issues.
First, we would map the site using one of our mapping drones to create a 3D digital model of the landfill’s topography. We would then create and optimize a fill sequence plan that takes into account lots of things such as access, drainage, waste compaction, use of daily cover soil (or ADC), optimum cell geography (the depth, width, and slope of a daily cell), and many other factors that include, not surprisingly, litter control.
Some of the key ingredients often include placement of soil berms and drift fences to provide protected areas within the landfill. Again, this is a critical part of what should go into the thought process as you develop an annual sequence plan for your landfill.
But the process doesn’t stop there. We can then create 3D computer models of each phase of the sequence plans. These models are then processed through Computational Fluid Dynamics software to analyze wind flows to optimize how each phase should be constructed, including the placement of berms and fencing to reduce wind velocity at the working face.
This allows us to play with different designs or parameters for windshield systems where we can adjust the height, slope, and other parameters to make our litter prevention system as effective as possible.
One final note: we fully acknowledge that not all litter can be prevented. If you have waste and you are outdoors, you are going to have some litter. The key is to maximize and customize your litter prevention and control efforts to best address the challenges at your site.