Covering Their Tracks
Landfills turn to daily covers such as tarps and foams to conserve airspace.
Spray-on slurries harden after being applied to a landfill's working face and may be used not only for daily cover but for the intermediate covering of working areas as well. Depending on the manufacturer, the products may consist of either a mix of polymers such as the Pro-Guard and ConCover line of products offered by New Waste Concepts or a cement mortar coating similar to stucco, such as the Posi-Shell System offered by Landfill Service Corp.
Collier County, Fla.'s 280-acre landfill receives between 1,300 to 1,500 tons of MSW per day. For daily cover, the site uses a combination of soil and Posi-Shell, says Daniel Rodriguez, director of solid waste for the county. The combination has been effective at keeping odors under control and keeping birds from picking at the waste. “During the summer months, we have a tendency to use a little bit more soil,” he says. “Over the last 10 months, we've recognized in the neighborhood of $600,000 to $800,000 in savings in soil usage.”
Longer-Term Concerns
Landfills sometimes need to consider more than just daily cover. Often, they need covers on a more interim basis, such as when they need to protect newly constructed landfill cells from rain infiltration or cover cells that are not currently in use, but where additional settlement of the waste may allow the cells to be used again. These covers are sometimes needed for periods lasting between two and five years.
The Millersville Landfill in Anne Arundel County, Md., recently constructed two new subcells, totaling 11 acres. The county originally debated about whether it should build the two cells at the same time, says Stephen Krajcsik, disposal and maintenance manager for the county.
Eventually, county officials decided they would “get an economy of scale by building both together,” he adds. However, that meant that the county would have to protect portions of the newly constructed cells that were not yet in use.
To protect the liners and the leachate collection systems in the yet-to-be-used areas, which feature 200-foot side slopes, the Millersville Landfill uses polyethylene rain-shed covers from Raven Industries. “As part of the construction project, we covered approximately three-quarters of the 11-acre [construction area] with the protective tarps,” Krajcsik says. “The panels came in large segments, and we basically field-seamed them together.”
“We weren't concerned about having them completely water tight,” Krajcsik adds. “We stitched them, sandbagged them, and they were toed in around the perimeter. As we fill [in the space with waste], we peel them back.”
Lynn Merrill is a contributing writer based in San Bernardino, Calif.
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