Getting Your Bearings

Bryan Griesbach

Most people have used a global positioning system (GPS) device for routine travel, but very few landfill operators have integrated GPS technology into their landfill operations. The technology can be used for surveying, in-cab machine grade control and, most importantly, to maximize density, thereby increasing the return on landfill cell development capital and slowing the rate of airspace depletion.

This article provides an overview of the evolution of GPS technology in the landfill industry, starting with basic surveying functions and progressing up to site-wide wireless mesh radio systems that provide two-way data sharing for GPS-enabled machines, as well as remote data access and management.

At the end of the article, a brief financial self-analysis will allow you to determine what level of investment in GPS technology is feasible for your facility. Given the steadily-increasing value of airspace, it's likely that GPS has already reached a price point that makes it an attractive investment.

Stage 1: Surveying

Every landfill manager understands the importance of grade control in maintaining proper stormwater control around the working face, facilitating site drainage and preserving functional roadways. Grade control is equally critical when working on outside slopes: Under-filling slopes results in a loss of airspace while over-filling may result in a notice of violation for exceeding permit boundaries. Correcting slope filling errors can be costly, requiring the placement of thin waste-lifts of just a few feet of waste or relocating waste overfills. Stage 1 GPS technology helps landfills managers meet their surveying needs, which many sites currently meet through the use of costly third-party surveyors. Stage 1 GPS technology allows for one-person surveying, construction staking, cut/fill marking and attribute locating. The equipment used includes a small GPS unit or "rover" (hand-held or attached to a surveying rod for greater accuracy) and a base station.

The rover orients itself using the same satellites used by automotive and hiking GPS units. But to achieve survey-grade accuracy, it needs the base station as an additional point of reference. The base station utilizes real-time kinematic (RTK) calculations to further refine the satellite GPS signal, transmitting survey-grade coordinates back to the rover. In some locations, RTK networks are operated and maintained by the state department of transportation or private entities, eliminating the need for a site-specific base station. With a cost range of $25,000 to $50,000, Stage 1 GPS technology offers landfill managers a timely and cost-effective way to become self-sufficient for most surveying needs.

Stage 2: Basic Grading

One of the obvious problems of relying on grade stakes is the difficulty of maintaining those stakes while operations are taking place. Stage 2 GPS technology solves this issue by putting the grade control information into the cab of machines operating on the working face.

In addition to an RTK base station, the machines are equipped with an antenna that can receive GPS and RTK data, along with a cab-mounted user interface monitor that indicates the current grade, final topography and the locations of previously marked critical site assets. In addition, some Stage 2 systems may provide compactor operators with information relative to how many passes the machine has made over a given area.

Stage 2 GPS technology typically costs $80,000 to $100,000 total, or approximately $50,000 additional per machine if you are enhancing an existing Stage 1 system, and eliminates the need for grade staking and re-staking. However, it does not allow for the collection or retrieval of any location data from the machine for later analysis.

Stage 3: Advanced Features and Static Connectivity

Stage 3 GPS technology provides a compactor operator with additional data, including an indication of waste deflection as the landfill compactor passes over each placed layer (this is a user defined function, but typically two feet of waste). Some Stage 3 systems may provide an avoidance zone warning, alerting machine operators as they approach geo-tagged gas wells or other key landfill elements.

More importantly, Stage 3 technology is capable of capturing and storing machine location data. This gives the landfill manager the opportunity to manually collect data from the machine for analysis. This requires that data to be transferred from the machine to the office using a USB flash drive. The resulting data can be incorporated into various software programs to provide volumetric calculations or to review an operator's productivity.

Stage 3 technology costs approximately $120,000 to $150,000, but it is the first level of GPS technology that is capable of providing the landfill manager the ability to routinely capture the volume information necessary to calculate airspace utilization.

Stage 4: Advanced Features and Real-Time Connectivity

Stage 4 GPS technology takes a giant step forward from Stage 3 with the addition of a wireless mesh radio network, allowing multiple machines to share real-time data. This is very important on working faces where GPS is incorporated into multiple compactors, ensuring that the machines do not duplicate their efforts.

Another huge advantage of Stage 4 technology is the ability to provide two-way data communication between the office and the field. This network supports the real time collection and analysis of the machine location data by a remote computer, eliminating the need to manually gather, download and compile the data sets from each individual machine.

The two-way data communication also allows the landfill manager or engineer the ability to remotely update the topographic file sets used by the machine operator. In addition, the system can be remotely accessed for training, support or data management functions.

The price range for implementing Stage 4 GPS technology is typically $150,000 to $200,000, depending on the complexity of the site and number of GPS-enabled machines.

What's the Payback?

Increasing your landfill density is a lot like getting an expansion, minus the permitting and development costs or the need to hold public hearings.

This is a simplified financial model that focuses on the additional return on cell-development capital. It does not attempt to quantify the additional operational savings associated with on-site surveying (Stage 1), proper slope placement from in-the-cab grade control (Stage 2), or the positive impact on depletion and accrual rates with density increases (Stages 3 & 4).

Every landfill will operate under a different set of variables, so for this analysis, please assume the following parameters:

Landfill Cell Development Cost: $200,000/acre
Average Depth of Waste: 80 feet
Average Gate Rate: $25.00/ton
Annual Volume: 280,000 tons/year (approx. 1,000 tons/decade)
Current Density: 1,500 pounds per cubic yard (lb/cy)

Of course, GPS technology is only a tool, not a cure-all. The actual results that a landfill experiences will depend on many factors. However, it is not unusual for a landfill to increase its density by more than 10 percent using this technology. As shown in the chart on p. 20, the cost of a full Stage 4 GPS system will be recovered by the additional revenue going into just one acre of landfill if a 10 percent density increase is achieved.

Conclusion

GPS technology has advanced rapidly in recent years. Regardless of the stage of implementation, it provides a vital tool for the machine operator, landfill manager and landfill engineer to use collectively to get the greatest possible returns from their landfill.

Bryan Griesbach, P.E. is the landfill business development manager for GeoShack North America. Contact him at (800) 444-5661 or [email protected].

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