Sky High Help

Aaron DeWeese

Satellites transmit more than cable television channels; their signals are helping landfill operators monitor everything from surface emissions to compaction rates - quicker and cheaper than ever before. As with any new technology, however, only a handful of pioneers are braving this new territory.

Here are four examples of how using these higher tech landfill tools have proved to be more accurate and less expensive than relying on older, more traditional methods.

How Tight is it Packed? The Pennsylvania Department of Environmental Protection (PADEP), Harrisburg, requires all landfills in the state to include a current topographic map in its annual report to determine annual compaction rates. In the past, this meant using expensive aerial mapping.

Searching for an alternative mapping method, Bill Binnie, facility engineer at Superior Service's Greentree Landfill in Kersey, Pa., hired in December 1998 Cummings/Riter Consultants Inc., a Pittsburgh-based engineering and hydrogeologic consulting firm, to survey and map his site using Global Positioning Systems (GPS) technology.

"For landfills this size [107.2 acres], aerial mapping used to be the only option," says Williams Smith, a project manager for the consulting firm. "GPS has opened up some alternatives to aerial mapping for landfill managers and engineers."

The survey was conducted in early December 1998 under cold and windy conditions. The GPS survey base station was erected in an open field away from vehicular traffic. Equipped with three Trimble 4800 Total Stations, the engineering field crew set out to map the 93-acre landfill footprint, a 6.2-acre borrow area and an eight-acre regraded area outside the footprint.

Once in place, the equipment was calibrated to the local site datum and grid using several existing site benchmarks. Site calibration was verified by successfully navigating to several site benchmarks.

"Navigating allows you to input the coordinates of a point and the GPS equipment will direct you to the point," Smith says.

Along with the GPS equipment, Cummings/Ritter used real-time kinematic (RTK) techniques to survey the landfill. According to Smith, RTK collected coordinate and elevation data to centimeter accuracy in real-time and, therefore, didn't need to post-process the data.

"Landfills are an ideal setting for using GPS because the sites are open and clear of overhead obstacles that may otherwise obstruct satellite signals," Smith explains. "Our equipment was equipped with 'On-the-Fly' (OTF) initialization, which proved invaluable because the landfill side slopes would occasionally block satellites when walking between survey points causing us to temporarily lose satellite lock. OTF initialization allowed automatic re-acquisition of satellite signals when we were back in view."

Considering the landfill's size, this process would take much longer without OTF, Smith says, since the field crew would have had to return to a known location (benchmark) to re-initialize the instrument.

"Another advantage of real-time surveying is the ability to display a job map on the data collector," Smith notes. "This enables you to verify, 'on-the-fly,' what points have been acquired and minimize gaps in the survey data."

A crew of two collected coordinate and topographic data over the entire landfill. Each person was equipped with a GPS receiver (rover) to independently collect data.

"Using two rovers doubled our productivity and we completed the survey in two days," Smith says.

Newly regraded areas outside the landfill footprint required correlating survey time with a particular satellite configuration. This ensured adequate coverage. According to Smith, satellite configurations were reviewed the night before to help determine when the satellites were in the best position to gather the data.

"Given [December's] short daylight, we confirmed that the equipment worked in the dark," Smith says. "The last several points along the access road were worked in the dark using headlights to illuminate the area. In all, we collected about 4,800 data points."

The active landfill workface was surveyed after regular operational hours to allow for an accurate correlation of volume-to-gate receipts for density monitoring. At the end of each day, all benchmarks and required areas were surveyed by downloading the data collectors to a laptop for viewing. This ensured enough data was gathered for mapping, Smith says.

"Because the survey data was collected in real-time mode, it was downloaded directly into our civil/survey design software for contouring without the need for post-processing," Smith says.

The data was contoured and edited to produce a site topographic map at a scale of 1 inch equals 100 feet, with a 2-feet contour interval. For a newly constructed cell, the recent certification survey was inserted into the site map to complete the landfill footprint's topography.

The land surrounding the surveyed area did not change and existing topography was used for the map. A draft, presentation-quality topographic map was ready in about a week for Superior's review. Mapping for the project was conducted using Softdesk's civil/survey design module along with AutoCAD Release 14.

"In all likelihood, we'll use it [GPS] again," Binnie says. "It was actually less expensive and faster than using a ground survey. It also was just as accurate and actually cheaper than doing a flyover for survey mapping for our annual report."

Testing Your Gas Recently, a GPS system also was used to conduct a surface emissions monitoring of the gas collection system at Martin County, Fla.'s Palm City II Landfill.

Federal air emissions regulations require that the surface concentrations of methane along the entire perimeter of the collection area, as well as along a serpentine pattern spaced 30 meters apart, must be monitored quarterly using an organic vapor analyzer, flame ionization detector or other portable U.S. Environmental Protection Agency (EPA), Washington, D.C-approved monitors.

Joe Curro, senior engineer and project manager for Camp Dresser & McKee (CDM), Cambridge, Mass., was hired by the county to help fulfill this requirement. He explains that corrective measures must be taken if methane concentrations of 500 parts per million are detected. Then, the targeted area must be retested. However, with manual flagging, markers tend to get uprooted, Curro notes, and coordinates become virtually impossible to relocate.

"Once the targeted area is buried, it's almost impossible to find again," Curro says. "And you can't expect lawnmowers to go around every flag. Quarterly surveying gets to be so cumbersome, and you have to redo it [flagging] every time. We needed something to [perform] real-time surveying. We had an earlier hand-held GPS version, but it was only accurate to within 100 feet. That didn't work out for us."

According to Curro, CDM recently purchased a Trimble GPS Pathfinder Pro XRS. Accurate to within 2 feet, the unit is used for gas system compliance surface sweeps, and is more cost-effective than a $12,000 survey, Curro says.

"We bought [the Pathfinder] because we do a lot of surveys," he notes. "We have other GPS applications in our company outside of landfills."

Using GPS and its six to nine satellites, the engineers took two days to survey the 40-acre Martin County site. A permanent landfill landmark is tested every time to ensure GPS coordinates haven't moved.

"We were getting a really good response [from the satellites] both days," Curro says. "As luck would have it, we found a 4-inch circle that was in exceedance with nothing else around it. Now, with the GPS, we can find the exact location of the exceedance next time without having to worry about lost flags."

Before using GPS, surveyors would manually enter survey information into an AutoCAD. Today, the system performs that task automatically each time a point is locked. GPS information then is overlaid on Global Information Systems (GIS) data to create a topographic map. CDM field crews still flag sites, but they are used primarily as visual aids for regulators when they conduct inspections. Curro says it's just easier to point to flags than to go back and explain everything.

"For this type of application, it does not make any sense to survey," he adds.

Help For Closure GIS are another high-tech tool becoming more common in landfill applications. CDM, together with Summit Engineering, Reno, Nev., is incorporating this system into a methodology they are developing to use in landfill closures in the western United States.

First, areas of old earth moving activities (likely to include waste disposal) are identified using photogrammetric analysis of historical aerial photograph stereopairs. Then, the analysis is linked with the GIS to characterize onsite waste disposal activities.

Still in the development stages, the new technology can give project management teams insight into the historical landfill operations. This should help to clarify site characterization activities and streamline closure plan development, according to CDM.

"The stereopairs are used with recent aerial surveys to develop digital terrain models (DTM)," explains CDM project engineer Tracy Bouvette.

The DTMs then are compared electronically to identify areas where past disturbances have occurred and identify contours indicative of cut and/or fill operations. Using stereopairs, the landfill's operational life can be chronicled using the dates.

"We supplemented the DTM analyses with the photo interpretation of historical aerial photograph non-coverages to develop a qualitative assessment of landfill activities for intermediate years between those with stereopair coverages," Bouvette says. "Obtaining correct historical aerials from reliable sources is no small feat, especially if a significant period of time needs to be characterized and numerous coverages are needed to characterize site changes.

"Given that typical historical landfill operations literally are buried beneath the ground and are difficult and expensive to characterize, using photogrammetric and GIS applications to leverage available historical data may be a cost-effective method to streamline landfill closure efforts," she adds.

Compacting GPS Caterpillar, Inc., Peoria, Ill., and Trimble Navigation Ltd., Sunnyvale, Calif., have jointly developed a GPS on-board system for landfill equipment applications. Caterpillar's Computer Aided Earthmoving System (CAES), now available on its compactor models, helps operators maximize compaction by providing real-time planning and surveying information. CAES uses an on-board computer and software, centimeter-level GPS (Trimble's BenchGuide system) and data radios.

The system continuously surveys the site, providing ground elevation information without the need for field surveys, grade stakes or other manual survey inefficiencies.

The system has been used for years in the mining industry, but is just being introduced now to the landfill market, according to Caterpillar officials.

The system's information flow begins in the engineering office, where a design file in the planning software is created. This design represents an area for the landfill equipment operator to cut or fill. It is exported from the planning software in standard AutoCAD DXE format and transported to the office via Caterpillar's METSmanager software. METSmanager sends the design file to the on-board CAES. Then, the operator begins cutting and/or filling to the design plans. Simultaneously, terrain updates are collected on-board using GPS technology. These "snippets" are returned to the office through the radio network.

In the office, the snippets move to another program, called CAESoffice, which is similar to the vehicle display only it shows several vehicles working at the same time. It also combines terrain updates from an entire fleet working in the field into a single up-to-date model of the landfill. As the machines work, the CAESoffice display will show the areas being updated.

For the compactor operator, using CAES is similar to playing a video game, according to Caterpillar. Instead of visually estimating the number of passes a workface needs for sufficient compaction, the operator uses the on-board CAES monitor.

The color of each grid represents the number of passes the compactor has made across an area. Final or design compaction is indicated by green.

The CAES system is designed to work with many different types of equipment, both Caterpillar and competitive, and in several different applications. Currently, systems are available for front shovels (both hydraulic and cable), wheel loaders, track-type tractors, scrapers, motor graders and compactors.

The display for each type of machine is a bit different, but only the onboard software differs between machines.

Using Omega Values Another example of high-tech applications for landfill equipment can be found on BOMAG's new BTM 05 Terrameter compaction control and documentation system, available on two of the company's models. It is designed for subgrade proof rolling and for identifying weak spots in landfill and embankment construction. The unit assesses the entire area and continually measures the material stiffness, settlement, deformation and load-bearing capacity of soil and granular materials.

As the machine passes across the ground, the measuring system continually produces an Omega value, a compaction quality measurement. The Terrameter monitors interaction between the acceleration of the vibrating drum and the dynamic stiffness of the material, which increases as compaction progresses.

Depending on the material type, Omega values between zero and 1,000 are indicated. The higher the Omega value (relative to material type), the better the compaction.

During each measuring pass, the Terrameter calculates the average Omega value and compares it with previous passes. An indicator on the instrument panel displays the average Omega value, while an on-board printer prints data on request and provides a continuous record of all Omega values for the entire compacted area. The printout can display the compaction results as an on-going curve or in 5-meter sections. Poorly compacted spots, represented by low Omega values, can be identified on the printout so that they may be compacted further.

A green light on the control panel indicates the roller is compacting effectively. If the required Omega value is achieved before the green light goes out, the operator may finish compacting the area and print the results. If the average Omega value increasing between two passes is minimal, the green light will go out, signifying that maximum economic compaction has been reached.

The analog instrument console indicates the current travel speed and actual frequency. An electronic unit, located under the operator's seat, stores and processes the acceleration value detected by the transducer unit.

Basically, GIS (Geographic Information Systems) is software for displaying information that is gathered in many ways - GPS (Global Positioning System) being one of them. GIS consists of background maps with features (a road) with attributes (width, surface type, last paving date, type of shoulder material).

These features need to be geographically located on the map. This is done with GPS, which provides latitude and longitude of the feature. In addition, the feature's type and attributes can be entered in the field and all of this data is then transferred to the GIS in the office.