Exploring New Solutions for Landfill Covers

Increased regulatory demands on landfill operators are driving new innovations when it comes to landfill covers. Many are touted as having greater efficiency, requiring less maintenance, costing less and mitigating some post-closure concerns. The products range from sustainable, aesthetically pleasing vegetative designs to multicomponent systems with engineered turf and sand that provide more performance predictability.

Blackstone Environmental designed a system using trees and prairie grasses to pump water out of caps, which Mike Kukuk, the company’s president, says is more economical and sustainable than traditional prescriptive caps, and as effective at reducing water infiltration. Kukuk is among speakers who will be presenting at Landfill Innovative Cover Solutions session on Monday, May 8 at 12:00 PM at WasteExpo 2017 in New Orleans.

The product leverages a technology called evapotranspiration, which combines evaporation with transpiration (plants absorb water and release it through its leaves.)

“A lot of landfills are nearing 30-year post closure dates, and there will be more in the next 10 years or so,” Kukuk says. “Natural vegetation will enable the site to retain aesthetics and requires minimal maintenance when we walk away from it.”

There is no or little mowing required, and while resulting cost savings vary by region, at an early Kansas installation, Hamm Sanitary Landfill, costs were cut in half. It comes with multiple benefits tied to construction and design.

“It’s hard to compact clay on a three-to-one slope,” Kukuk says. “You have to put plastic over the clay and about a foot of good soil. Our cap uses loose soil so it’s easy [to install]. Also by creating a seed bed we enhance evapotranspiration, vegetation growth, and water storage, offering a method that is cheaper to construct and more sustainable.”

Leveraging the right vegetation is important. And there may be trial and error with soils with this relatively new concept.

“There are many covers out there with grass, but not many with trees … There is still more proving out to do in many states. But I think these caps will become more commonplace,” Kukuk says.

Watershed Geosynthetics has a patented final cover system that it says is more predictable in performance and cost than conventional soil covers, says David Cieply, vice president of Watershed Geosynthetics solid waste market of North America. He also will be presenting at WasteExpo.

Ultimately, the technology, called ClosureTurf, cuts post closure maintenance costs by 90 plus percent.

The three-component system includes a geomembrane layer; synthetic turf layer; and specified infill, usually of ASTM C33 sand.

“So you still have the geomembrane liner, but we replace the soil and vegetation with engineered turf and sand,” says Cieply, adding in addition to cost containment, among benefits are improved water quality and more airspace.

In their quest for improvements, the company developed a benchless design to eliminate the need for additional soil used to slow water runoff.

“This has translated to huge cost savings, not only because you use less soil but you do not have to maintain the benches,” he says.

The company has installed more than 45 million sq. ft. of ClosureTurf in over 20 states. The design best fits municipal solid waste and construction and demolition landfills as well as coal combustion residuals operations.

Use of exposed geomembrane covers has grown in popularity over the years, as these structures minimize leachate and control erosion and odor. But they must be able to stand up to harsh climate conditions. A system called Wind Defender has a new way to protect these caps—using aerodynamics rather than the existing system that leverages weights to hold them down.

“Traditional ballast systems include sandbags, ropes and other materials to hold covers down,” says Elliot Pugh, sales manager for Wind Defender who will speak at WasteExpo. “Our Wind Defender system ballasts and protects exposed geomembrane covers. It’s a knitted textile that aerodynamically diffuses wind uplift to prevent the membrane from becoming displaced.”

Pugh says the technology installs faster, is safer and less physically demanding to deal with than traditional systems, which typically require heavy sandbags to be hauled up slopes. And it blocks 60 percent of the ultraviolet rays from the underlying membrane, increasing covers’ lifespan.

“It’s low maintenance, so there are not a lot of repairs needed,” Pugh says. “And the technology stands up to the wind. We’ve experienced wind speeds over 100 miles per hours without failure.”

The Wind Defender system has been installed in over 500 acres throughout the United States and Canada.