November-December 2000

From Satellites to Surface Sweeps: Using the Global Positioning System in LFG System Monitoring

Thanks to the militaryís high-technology developments, monitoring landfills is now more accurate and less expensive.

When the United States Department of Defense (DOD) developed the global positioning system (GPS), it probably did not envision that the higher technology would prove useful to the solid waste industry. However, the introduction of GPS - a multiple satellite-based positioning system operated by the DOD - to the public has not only revealed its applicability to everyday life, but to industry, municipalities, and commercial activities. A system initially developed to provide warriors with real-time location of troops and targets now aids in landfill surveying and sweeping.

Civilian Uses for GPS

GPS is mostly used for navigation purposes. The aviation industry employs GPS to guide pilots along the course of their routes, helping them to avoid bad weather and collisions. With the introduction of GPS to the public, more people now realize the benefits of the technology for recurring tasks. Wilderness hikers routinely use GPS to guide them through remote areas, providing the added benefit of the hikerís accurate location in the event of an emergency. Utilities use GPS to locate cable connection boxes, underground valves, and other features that might become hidden in vegetative growth. Municipalities have begun mapping assets, such as hydrants, signposts, and guardrails. In the solid waste industry, facility owners use GPS for landfill gas (LFG) monitoring, realizing savings from reduced manual labor, and the improved accuracy of data collection and repetitive reporting.

Improving Monitoring Accuracy

Many landfills face stringent guidelines mandated under the US Environmental Protection Agencyís New Source Performance Standards (NSPS) for MSW landfills. The NSPS require that certain landfills install an active LFG control system. Although control regulations and methods vary among states, all states restrict methane emissions levels and set operating efficiencies for LFG combustion. Periodic LFG monitoring is required to demonstrate compliance with LFG system operating regulations.

Surface methane emissions monitoring (surface sweeping) is required on a periodic basis at NSPS sites and, increasingly, at non-NSPS sites. Camp Dresser & McKee Inc. (CDM) of Cambridge, MA, pioneered the use of GPS in performing surface sweeping, saving both time and money. Using GPS, CDM documents the LFG system for regulatory compliance to determine if LFG, in excess of NSPS limits, is escaping from the landfill. GPS also accurately locates any damaged areas needing repair. By precisely locating these areas, repair crews can perform repairs efficiently without extensive searching for the fault. This method of landfill monitoring is used in a fully integrated program of gas monitoring and collection system balancing and tuning.

The Old vs. the New

In the past, LFG monitoring was often performed haphazardly. In its most primitive form, monitoring occurred by simply walking around the site, observing distressed vegetation or other signs of LFG emissions. Today, readings are often taken at points showing a need for attention, with little or no positive means for accurately locating areas in need of repair. In a higher level of accuracy, surveying crews traverse a site, marking the landfill in about 300-ft. increments. Another crew then walks the site, following the marker stakes while monitoring for gas emissions along the surface. While this method is a common and accurate method for monitoring, it is not entirely efficient. Stakes become uprooted and displaced between sweeping occurrences, mandating another site survey for the next sweep. This is a costly process, and there is no guarantee that the original survey crew will plot the exact points again.

During a routine sweep by either of the above methods, a repair crew flags those areas that demonstrate excessive emissions. The flags are also frequently disrupted or removed, however, particularly by grass mowers, making it difficult for the repair crew to identify the dig location. This results in excessive site disruption or digging up multiple areas to find the one area that needs attention.

Using GPS greatly simplifies the process. During the landfill sweep, the monitor wears a backpack containing the GPS equipment and carries a padlike device approximately the size of a large, handheld calculator. The technician also carries a flame-ionizing detector (FID), pointing it toward the ground to detect gas emissions. If the surveyor finds an excess of allowable emission limits during a routine surface methane sweep, he or she hits a button that plots its exact location using GPS. Points along the NSPS-mandated 300-ft. grid are also recorded in the same manner. After surveying a site, landfill owners can return to a database and print out a plot of the landfill, noting locations where problems might occur.

Access to Inaccessible Sites

In many cases of LFG surveying at closed sites, crews must traverse areas overgrown with vegetation. To minimize the need to clear site vegetation, GPS can be used to navigate around the areas of heavy vegetative growth and obtain the desired samples - often with no need for extensive site clearing and with minimized danger to survey crews and technicians.

Accuracy Increases Efficiency

By using GPS, landfill owners can more accurately identify spots that might need attention. For example, if a technician locates an area that indicates leaking gas, he or she can plot the exact location of the needed repair. When the repair crew arrives to make repairs, which could be days later, they are able to locate the exact spot, eliminating needless disruption to the land. Currently available GPS equipment can locate points within +/-1 ft., real time, increasing the chances that technicians will survey the same point each time monitoring is required.

Using GPS also saves clients time and money. An experienced crew of four, utilizing the survey/sweep method of gas monitoring, can take up to a week to survey a 30-ac. landfill. Using GPS cuts in half the number of people required for monitoring and can reduce the surveying time from a week to less than a day. With a landfill generally required by NSPS to undergo a minimum of three quarterly monitoring sweeps the first year after a gas system start-up, the savings add up.

Database Management

During the landfill sweep, the monitor wears a backpack containing the GPS equipment and carris a padlike device and a FID, pointing it toward the ground to detect gas emissions.

Data collected from the landfill sweep goes directly into a database, which can be accessed for geographic information system (GIS) or situation modeling purposes. Because the information is in an electronic form, it is easily entered into the GIS database, saving the time of manually plotting sweep data on a map of the landfill for regulatory purposes.

Using this higher technology for plotting simplifies submitting forms to regulatory agencies. Many layers of data can be combined to generate the specific site plan(s) required for inclusion into the site monitoring report(s).

GPS in Action

CDM currently uses GPS to monitor several sites, utilizing a $12,000 Trimble GPS system combined with company-owned FID equipment. CDM has been performing landfill sweeps for several solid waste clients, saving them thousands of dollars by providing more accurate monitoring and reporting and increasing the accuracy of locating areas in need of repair.

In response to odor complaints from neighbors, as well as for compliance with NSPS, Martin County, FL, contracted CDM to design and install an LFG collection and flaring system for closure of part of the countyís landfill. Six passive, solar-powered flares were designed and installed to treat isolated gas emissions from a series of leachate collection and pumping wells as an interim measure until a permanent collection system could be installed. Later, vertical gas collection wells, gas collection connections to four leachate pumping stations, and an open flare capable of handling 600 standard ft.³/min. of LFG were installed as a permanent gas control system. CDM routinely monitors the site using GPS and generates reports using the GPS database.

In addition to using GPS for plotting the sweep grid, CDM also uses it to navigate the grid, making it easier for the technicians to walk the site and hit routine monitoring points. System repairs were pinpointed to within 1 ft.², greatly improving the efficiency of repair operations.

For St. Lucie County, FL, CDM designed an LFG collection and flare system to remove gas from sections of the countyís landfill that were closed or where final grade had been reached. Because landfill operation will continue for a number of years, CDM designed the system to handle the ultimate gas design flow rate and to expand in phases as the need arises. The LFG system consists of vertical gas collection wells, with gas collection from four leachate pump stations, a series of leachate collectors, and an open flare. Condensate reaches the leachate pump stations through a series of gravity drains and pumps. The condensate is mixed with the leachate and pumped to a nearby treatment facility. CDM used GPS to perform the routine surface sweeping of the site and proved that monitoring can proceed from quarterly to annually.

Minimizing Disruptions to Sites

LFG monitoring at the Yarmouth site is accomplished by outfitting a golf cart with the GPS and FID.

GPS is especially helpful for monitoring sites involving landfill reuse. Site owners invest significant funds in closure and reuse plans to make a site an enjoyable place for the community. Former landfills now take the form of town parks, golf courses, and playing fields. It is important to minimize disruption to these sites during monitoring purposes to ensure that the new use can continue to operate simultaneously with routine landfill monitoring. GPS minimizes disruption to the sites because it identifies any LFG system componentsí exact locations and thus allows monitoring personnel to complete their tasks without closing sections or all of a site.

Working for the town of Yarmouth, MA, CDM uses GPS to monitor its recycled 57-ac. landfill, which now operates as a golf course. Because it is a recreational site, CDM installed the active LFG collection system was installed entirely underground, with all wellheads, control valves, pump stations, and monitoring points in protective vaults. Although facility users see no part of the system, it is easily accessible for maintenance and repair.

Using GPS enables a technician to perform LFG without flags or stakes, which would disturb the tee areas or greens by impeding play. Monitoring is accomplished by outfitting a standard golf cart with the GPS and FID, allowing monitoring operations to blend with the activities on the golf course. When it is necessary to locate the siteís hidden monitoring points, valves, or pump stations, the technician only needs to recall the locationís coordinates using GPS, then proceed to that location.

Conclusions

The use of GPS is another instrument in the toolbox of landfill monitoring professionals. Once the exclusive tool of military field commanders, GPS has become a useful tool for landfill operating and monitoring operations. Haphazard and/or expensive methods of monitoring sites for compliance with NSPS or other regulations are a thing of the past. Increased accuracy through the use of GPS, combined with the ability to download GPS data directly into multiple report formats, has resulted in cost savings that can be passed on to landfill owners. Repair operations can be accomplished quickly, accurately, and safely thanks to the precise location of areas in need of repair. Unnecessary disruption of neatly landscaped areas on reused sites can be eliminated as a result of precise location data for operational features. Monitoring operations can be performed without disruption of activities on closed sites. Exposure of field personnel to the potentially hazardous environment found on some sites is greatly reduced, adding to the safety of field operations.

The uses for GPS appear limitless and are just now being tapped for use in landfill operations and monitoring, offering site owners not only a more cost-effective monitoring method, but making it easier for them to meet regulatory demands.