Samuel M. Rohr


Landfill operation has changed a lot in the last few decades, and while it has increased in scope and become more environmentally friendly, it has also become more expensive and complicated. With these evolving requirements, come new and useful tools to meet the changing needs of the landfill operator. One of the newest tools is the landfill GPS system, typically supplied as an add-on to a compactor or landfill bulldozer, and now offered by virtually all heavy equipment manufacturers that sell such equipment.  Landfill GPS systems allow operators to track construction on the working face, monitor compaction in real time, and produce timely progress and efficiency reports. The ability to see what is happening on the surface of a landfill minute to minute and react more quickly based on this feedback gives an operator a significant advantage over others who can only react based upon periodic site surveys. Hence, what was once considered a luxury add-on to heavy equipment is fast becoming a less expensive and more common standard item, available to a wider range of landfills.  What follows is an overview of the usefulness of GPS systems to the modern landfill.


GPS Systems Guide Construction

GPS Systems at the most basic level, provide the position of the machine or machine blade to the operator.  On top of this, they also provide the position of the machine relative to the landfill cell’s final and interim designs. Operators can then check their progress towards the current design at will. This is the first and most basic job of a landfill GPS system.


Perhaps the most useful application of this information is in using airspace efficiently.  Airspace conservation is essential to profitability in the landfill industry and there are many tools offered to site managers that promise to extend the life span of a site. GPS systems have become an essential part of the modern landfill operator’s airspace conservation toolkit. The most crucial part of closing a cell, from the compactor or bulldozer operator’s perspective, is building the outer slope accurately. So, how does a machinery operator know when they are nearing the edge of their design? In the past, a landfill manager may pay an outside surveyor come out and place stakes, or they may use their own instruments and crew to manually check their own grades.  This process would have to be repeated many times as the cell grew in size. Staking is both expensive and time consuming, and it necessitates that work stop in that area while the survey is conducted.  If a site either overbuilds or underbuilds an exterior slope because surveys weren’t conducted on time or frequently enough, fixing the problem can be very expensive. A landfill GPS system gives the real-time position of landfill machinery on site and today’s operators and management can check their grades at will, eliminating staking and preventing over and underbuilding. With an onboard compactor or bulldozer GPS system, the landfill manager and machine operator can ensure that they fill to top-of-waste grade before moving the working face to another area. This ensures that every cubic yard of airspace is filled with revenue-generating waste, eliminates under-filling and reduces the amount of final cover material required.


GPS systems are also useful as a construction tool on a day-to-day basis, whether or not the working face is near the cell’s designed extents.  Landfill management can now more easily design lifts and set interior slopes to ensure hill stability and proper water drainage, by setting them on the onboard GPS system’s computer. Additionally, bulldozers outfitted with GPS systems can be used to cut off trucks and spread waste in consistent thin layers, over areas that are ready for new waste, as indicated by the compactor.


GPS Systems Assist Compaction

Optimum compaction that results in the highest waste density possible is an important aim of every site, and assisting compactor operators by providing real-time feedback is another duty of a landfill GPS system. GPS technology has evolved from a simple tracking and measurement tool to a system that teaches operators how to use their heavy equipment effectively to compact waste. A seasoned compactor operator can develop a feel for his or her machine and will over time learn to use the compactor more efficiently.  However, this still involves a certain amount of guesswork. GPS technology adds a level of certainty to the compaction process that isn’t possible by any other means.


The earliest landfill GPS systems approached this task by relying on a simple two-dimensional pass counting method to improve compaction. These systems would count every time the compactor passed over a specific area, keeping a tally for the entire working face. When the preset number of passes was met in a certain area, the GPS system would tell the operator the surface there was fully compacted.  This method can be used to increase waste density, but it has limitations.  On one hand, if the pass count is set very high, a compactor operator following this guidance will effectively compact the softest waste, such as wet MSW, but they will end up making more passes than needed over the harder material, such as ash or C&D.  Ultimately, this extra effort results in wasted fuel and added machine wear, because of the inherent imprecision of the pass-counting method. Landfill compactors are a significant investment for any site and use a tremendous amount of fuel. Operational inefficiency isn’t to be taken lightly.


To solve this problem, modern GPS systems no longer guide the compaction process via pass-counting. Newer systems use a truly three-dimensional measurement that indicates how much the surface is moving beneath the machine in each area. This movement is referred to in the industry as surface deflection. This information provides compactor operators with an actual measurement of how much vertical movement occurs on each pass, instead of just keeping a count.  When movement decreases to within a configurable threshold, operators are said to have reached the “practical point of refusal”, meaning that it is no longer efficient to pass over that area, further passes will only waste effort and fuel. With this info at hand, compactor operators can then make an informed decision about whether or not to continue to pass over an area, instead of relying on a one-size-fits-all pass count, or “eyeballing it”. With additional on-screen information about the layer thickness, the GPS system takes all of the guess work out of the equation to give operators the information they need to maximize waste density and achieve the optimum compaction possible with their waste stream and equipment. In-place waste density may climb further, as much as 25 percent over several years.


Reporting and Monitoring

The final duty of a landfill GPS system is to provide management with oversight and reporting that enables them to manage their machinery more efficiently. Almost all modern landfill GPS systems installed today are networked in some capacity, allowing the office to see what is happening on the working face, and centrally collecting data on machinery movement.  In the past, landfill management would have to monitor the efficiency either directly via a foreman’s visual oversight, or indirectly via a machine metric such as engine hours and fuel use. Now, similar to over-the-road consumer GPS systems which are already providing the vehicle’s operator with a position for their use, these GPS systems use that same functionality to track the vehicle’s position and produce movement reports. Unlike consumer GPS equipment, however, GPS equipment for landfill use is much more accurate. Consumer-grade GPS equipment is accurate to plus or minus five feet, whereas landfill-grade equipment is accurate to plus or minus three-quarters of an inch.  With this accuracy, landfill GPS equipment provides survey-grade position measurements, making it possible to produce maps of the surface traversed by the machinery and calculate the volume of waste buried daily and the amount of remaining airspace in the current cell. Adding input from the truck scales, management can calculate their own waste density, without waiting until the end of the month, quarter or year for outside surveyor feedback. The larger the site, the faster the surface changes, and the more urgent this feedback is to the landfill manager’s effective operation of his site.


Real-Time Feedback

Today’s landfill operators using GPS systems on their bulldozers and compactors essentially have a sophisticated construction, survey and monitoring tool at their fingers, which gives them the real-time feedback that they and their staff need in order to be more efficient and work more accurately. Landfill and machine operators are no longer constrained by their surveying budget and schedule, and can take on more of the monitoring themselves, resulting in better airspace use, less fuel usage and machine wear and higher waste densities. What was once only a tool available to the largest sites with the biggest budgets is now becoming a tool more affordable to the majority of landfills, and well worth a second look.


Samuel M. Rohr is the Director of Sales and Marketing for GeoLogic Computer Systems, in Waterford, MI. He can be reached at (248) 335-8863 or e-mail [email protected].