For every municipal landfill owner, maximizing capacity is not only a mandatory, long-term objective, but a daily one as well. Though there is a temptation to stick with long-standing practices, new technologies also have their place. Operators today are using computer-based technologies — global positioning systems (GPS), geographic information systems (GIS) and computer-aided design (CAD) — to extract every cubic yard of airspace out of their landfills.

GPS

GPS was developed by the U.S government and uses a constellation of orbiting satellites that transmit precise microwave signals. Ground-based receivers use the signals to determine the receivers' current location and velocity. A GPS receiver on a compactor transmits landfill surface and machine position data to a portable receiver on the landfill, which then relays the information to a computer terminal at the landfill office. The computer integrates the field data with the geometric configuration of the landfill.

In essence, GPS and its related accessories provide the compactor operator a real-time, computer-generated graphic of the landfill surface and the precise location of his machine. By sensing the changes in elevation and slope (grade) as the compactor moves across the trash, the operator is provided, in real-time, a graphic confirmation of when optimum density of the trash has been reached and when the surface is at the required grade. As a result, the operator works more effectively, neither under-compacting nor over-filling the trash. Compared to the conventional “seat-of-the-pants” method, which relied more on an operator's accumulated experience, the use of GPS results in less wasted airspace.

Prices for a GPS compactor system usually start at around $125,000, depending upon the brand. If that sounds expensive, contrast that with the value of the landfill airspace that can be saved. Wasting just 12 inches of airspace over a 20-acre area at a density of 1,200 pounds per cubic yard (lb/cy) and a tip fee of $28 per ton results in more than $500,000 in lost revenue. Charlotte County, Fla., determined it could potentially realize up to $9 million in additional revenue over a 16-year period with just a 10 percent increase in compaction density afforded by a GPS-based program.

GIS

GIS software integrates data and information management, mapping functions, and analytic tools. It is widely used by local, state and federal agencies as well as private companies to manage natural resources, utility infrastructure and logistical planning operations. Landfill managers have shown increasing interest in this powerful tool because it is a perfect fit for their complex facilities, which have large amounts of data to collect and maintain.

The power of a GIS is its ability to contain all of the critical data on components such as networks of groundwater monitoring wells, surface water stations, landfill gas collection systems and leachate collection systems in one database. Typically, this information is in multiple formats, scattered between computers, file cabinets, loose files — even inside of employees' heads. When employees move on, agencies can lose years of landfill records.

With a GIS, this data can easily be assimilated into common files. A few keystrokes by a facility manager reveals the history of any landfill gas (LFG) well, including flow, temperature, gas quality, maintenance and repair aspects, age, and exact location on the landfill. A similar level of detail is available for pumps, valves, leachate transmission systems, leachate treatment facilities, potable water supplies and sanitary sewer systems. An owner can even review his applicable permits or check to see if a particular issue has been evaluated and reported.

With a GIS, monitoring groundwater becomes vastly more useful and effective with the potential to save owners substantial costs, particularly when contamination from the landfill or other facilities is suspected. The powerful automated mapping functions built into a GIS allow for the creation of highly accurate, detailed hydrogeologic maps, integrated into the exact topographic features of the site. As with a LFG well, all of the information on the monitoring network is readily available. Taken as a whole, GIS provides managers and their consultants a level of efficient data management and detail that has not been previously available.

What does this have to do with extending landfill life? Plenty. For example, gas collection systems and leachate re-injection points for bioreactor systems can be located precisely where they will do the most good, helping to maximize decomposition of the waste fill and laying the groundwork for possible future reuse of some of that space. Coupled with timely surveying of the landfill surfaces at these points, a more accurate measurement of the volume reductions at these points is available to the manager. System adjustments are then more effective and result, over time, in more precise management of the waste fill and resulting airspace.

The monitoring well network at a landfill is an early warning to potentially big problems. If quality trends are missed or misinterpreted and groundwater contamination is more severe than perhaps thought, the continued growth of the landfill could be significantly affected. The regulatory agency could require corrective action, which could include restricting waste disposal in certain areas. Worse, it could prohibit waste disposal completely and require premature closure of certain areas of the landfill.