Since 1992, the US Environmental Protection Agency’s Subtitle D has mandated that at the end of each operating day, landfills must cover the working face with material to deter fire, odor, vectors, blowing litter, and pests. 6 inches of soil was commonly used for this daily cover, but landfill soils suitable for daily cover are not always readily available, and therefore must be purchased and transported to the site. This increases operational cost, traffic in and around the landfill, and the generation of dust. The manpower and equipment required in obtaining, storing, spreading, compacting, and recovering large quantities of soil as daily cover may not be the most economical use of these resources.
Thus, when the EPA began approving alternative materials in 1993, the market opened wide. Since then, manufacturers have continued to improve their materials to eliminate any issues associated with their use and enhance their performance.
ADCs are grouped by renewable and replaceable (tarps) and hydraulically applied (sprays, foams, and films). All strive toward the same goals: odor control, containment of blowing litter, protection from birds and insects, and saving air space.
“All of these products are used to maximize the available landfill space and increase its operational life span,” says Joshua Bruno, product manager for Finn Corp., which produces units that mix and spray various hydraulically applied ADCs.
Hydraulically applied ADCs consist of either wood fiber, paper fiber, or a combination of both, with an adhesive component of polysaccharide or polymer compounds. This enables the product to adhere to the waste in the landfill while reducing any chance of blowing debris. Improvements to hydraulically applied products include better coverage, adhesion, and odor eliminators, Bruno says.
“Prior to the use of ADCs, the most common practice to cover the waste was the specified amount of topsoil that was normally obtained from the site or nearby area,” recaps Bruno. “Sometimes, landfills would try to scrape some of the soil layer off before they started each day, but they would never remove the entire layer.” In other cases, landfills would start the new cell right on top of each soil layer. Over time, the soil layers would add up, wasting space and shortening the operational life span of the cell. “With the use of ADCs, they are able to cover the material in the same fashion, but with a fraction of the material and used space. With the use of ADCs, you can gain the same coverage [as 6 inches of dirt] with one-quarter inch of the applied material. Thinner layers of ADC cover over each cell leads to increased usable space within each landfill.”
Class 1 landfills did not have to cover with 6 inches of soil at the close of business daily before Subtitle D, states Marlon Yarborough, sales and marketing manager for Tarpomatic Inc. Once the only material used and still widely accepted, dirt is falling out of favor at many landfills due to the cost and labor involved, not to mention the airspace lost. “Alternate daily cover is an accepted program now.” But, he adds, getting approval for covers from local government used to be a “major obstacle.” It is a much easier process now.
Tarps have been popular since the 1980s, and the introduction of their automatic tarping machines in the 1990s made the job easier. Tarpomatic’s version is a self-contained unit that attaches to a dozer blade or a trash compactor blade to spool the tarp out over the working face which alleviates the dragging of tarps. It is operated by remote control.
The Tuff Tarp tarps are constructed of high-density woven polyethylene, coated on both sides to shed water. “The tarps are woven, then laminated top and bottom with a coating. We changed the fabric to make it stronger and heavier and longer-lasting,” explains Yarborough. With an LDPE coating, the fabric is both water-resistant and flame-resistant and offers a 24–36-month life span. “Too much flame retardant in polyethylene weakens the fabric; not enough won’t pass regulations.”
The tarps are weighted with chains in the long side edge pockets and crossing cable pockets every 11 feet to solve the problem of wind blowing them off. Each spool has a capacity for up to 300 linear feet of weighted tarp in 20-foot, 30-foot, 40-foot, or 50-foot widths. Tarp lengths can vary, from six 50-foot, to three 100-foot rolls, or two 150-foot rolls depending on the customer’s need. Because their machines are capable of unhooking a spool and picking up a new one with another tarp on it, Yarborough says many landfills keep one machine for multiple spools. He also reveals that the design of the machine changed to balance and ride better on the blade.
“Our product covers all the bases,” concludes Yarborough, noting that their machine is suitable for all landfills. Perhaps the biggest advantage of the ATM is the safety factor because it eliminates the danger of employees walking through trash to spread cover every afternoon. Instead, Tarpomatic’s automatic tarping machine utilizes a tier four Caterpillar diesel engine to deploy and retrieve the tarps. By utilizing their product, the life of the tarp is drastically extended.
The Wind Beneath My Wings
Not only are reusable tarps deployed by a tarp deployment system safer; they are also effective, efficient, and affordable. “For what typically takes over three hours to load, haul, dump, and spread enough dirt to cover a working face, a tarp deployment system can cover in 20 minutes with one operator,” explains Shannon Harrop, sales and marketing manager with the tarpARMOR Division of Southwestern Sales Co. “Soil is replaced with reusable—and ultimately recyclable—polypropylene tarps.”
Nevertheless, the effectiveness of reusable tarps is sometimes questioned in windy environments. “Wind can prove to be challenging,” acknowledges Harrop, “but using reusable tarps in windy environments has been solved by using the patented tarpLOX Cable Ballast System.” In fact, he adds, “when used with properly designed internal ballast cables, tarps have actually proven to be one of the most effective cover methods.”
Tarps equipped with tarpLOX have frequently been specified at landfills known for high winds, such as the plains of Kansas and landfills along the California coast that are subjected to gusting Santa Ana winds.
Harrop says that tarps equipped with tarpLOX have even remained unmoved through severe storms. In March 2018, the port of Darwin, Australia, got smashed by Tropical Cyclone Marcus, with winds up to 80 miles per hour. According to a testimonial from a customer, the landfill operators had deployed tarps, using a tarp deployment system machine from tarpARMOR the day before the storm hit; the following day, they expected to find the tarps somewhere in the Kakadu National Park but were pleasantly surprised to find they hadn’t moved.
The materials include woven polypropylene tarps, 7/8-inch diameter steel ballast cables weighing 1.4 pounds per foot, and the reusable steel tarpLOX connector. Deployment is accomplished by the tarpARMOR TDS machine.
Wind is one significant challenge that has been overcome by the use of a properly equipped tarp deployment system. Harrop says cost and odor issues have also been overcome. “Cost can be an obstacle, but is overcome with efficient reusable tarps deployed with an automated tarping machine.” With a typical average life span of 2.5 years for properly ballasted tarps deployed with an automated tarping machine, the cost to cover with tarps is often the most cost-effective method at less than half a cent per square foot per day. Costs are further reduced by saving labor.
Odor issues can be overcome with optional equipment installed on an ATM, such as odor neutralizer spray systems that control odors at the working face. Optional systems include spray pump, reservoir, and nozzles that are factory-installed along the length of the tarp machine frame and controlled via wireless remote to spray a path 30–40 feet wide across the working face. This allows operators to neutralize odor at the same time the working face is covered with tarps to close the working face for the day. The working face can also be sprayed each morning as tarps are rolled back.
Film at 11
Nevertheless, tarps have numerous detractors. They require a lot of work, manpower, and time. In bad weather, they can be hard to put down or take up. When they are removed, they let emissions escape. They aren’t cost-effective for big landfills. Some tarps require specific equipment from the manufacturer for deployment, which adds to the cost. They may not cover the entire working face.
Sprays face challenges too: they require prep time to mix the slurry. They freeze in cold climates. It can be difficult to get complete coverage all the way around, creating a shadow effect on the far side. You have to clean the system after use. Rain can wash it off. Severe weather (wind, rain, snow, freezing temperatures) can delay or prevent thorough application.
One way to overcome these issues, according to J.D. Mohr, business development & marketing executive for Epi Environmental Products Inc., is to use non-reusable geosynthetic film. “It solves many issues. It is not affected by rain. There’s no mixing, no prep, no cleanup afterward. It produces a complete impermeable barrier.”
Enviro Cover is a uniquely non-reusable polyethylene film developed to meet EPA requirements to control disease vectors, fires, odors, blowing litter, and scavenging without presenting a threat to human health or the environment. It promotes water runoff, minimizes the generation of leachate, and controls the escape of odors and gas emissions at the surface of the waste.
The film is a proprietary polyethylene that meets ASTM standards and is available in different thicknesses: 1.25 mil and 1.75 mil (the most popular). The chosen thickness depends on the type of waste, Mohr says: Commercial and C&D like a heavier film. Coverage with the 1.25 mil film is approximately 134,000 square feet. With the 1.75 mil, it’s roughly 93,500 square feet.
The film comes on a roll 18 inches wide and is deployed like a big roll of saran wrap by a rubber track machine that drives over the working face. “As you drive over the working face, it deploys off the roll and deposits ballast,” details Mohr. Ballast—sand or dirt—discharges via a conveyer belt and helps hold down the film. Once the film goes down, you can put the next day’s waste on top for continuous containment that provides space savings.
On windy days, Mohr says the roll can be raised or lowered, and more ballast added. “The California canyons have high winds, but they have no trouble using this.” Each region has different issues. For example, Alaska is cold and Louisiana is rainy. The film keeps rainwater from infiltrating to minimize leachate generation.
The non-reusable film leaves no toxic by-products and doesn’t require handling after being in contact with the waste. It lasts up to four weeks and is mechanically destroyed by placing the next day’s waste on top of it so it provides a continuous barrier to control, prevent, and reduce the escape of odors, gas, and vapor emissions from the landfill cell, while also minimizing the risk of fires by limiting air intrusion. Because it does not require removal, there is continuous control over landfill odor and gas emissions. Methane gas remains trapped for utilization and further processing, which removable tarps cannot facilitate.
Mohr claims that the system is cost-competitive, especially if the location owns spray-on equipment. Additional cost savings are achieved because there’s no need to purchase soil, prep a solution, or clean up after spraying. It also minimizes rainwater infiltration, thereby reducing leachate handling costs.
When compared with using soil, the film increases the airspace utilization rate of a landfill. Daily cover costs are lower, in part because the film eliminates the operating costs of acquiring, storing, moving, spreading, compacting, and recovering of soils and reduces landfill equipment capital costs, noise and dust generation, and labor costs because only two people are required for an application.
The working face generates odor, but odor complaints are reduced because the film creates an impermeable barrier between the waste and the environment. EC film stays in place, as opposed to temporary tarps that are removed in the morning, unleashing the gas and vapors trapped underneath.
Still in the early stages of development, the Enviro Cover Deployer Model 800 is a self-propelled applicator built on a rubber track carrier with a tight turning radius, but other applicators may be used.
A Better Look
For 30 years, New Waste Concepts Inc. has developed products to suppress dust, VOCs, odors, and gases for the solid waste and other industries. “We offer a spectrum of cover materials,” sums up Milton Knight, CEO and founder.
Their cellulose-based product absorbs moisture up to eight times its weight and creates a film that can reduce the intrusion of water and the escaping of gas. “By changing the polymer’s nature, we’re able to create a better film-forming, which helps control odor and minimizes evaporation,” explains Knight.
Benefits include the fact that it’s a quicker solution. “It takes less time to close the working face, so the landfill can accept waste longer,” says Knight. “It extends the time they can remain open.” There’s also no shut-down in high-wind conditions, as there can be with other ADCs.
It fits any size and shape of working face, as opposed to tarps that may leave some areas uncovered. The film is ideal for big sites that use a lot of cover. It also works better on slope applications than tarps, reducing the volume of water going into the landfill because it absorbs some rain. “Tarps have a difficult time in heavy rain,” observes Knight. “The water pools and the tarps tear.”
The product can be left in the machine; there is no set time. It’s flexible and durable and lasts up to one year, making it economical. Knight estimates that a tarp is about the same price as NWCI’s product, which is less expensive than foam. “Toledo and Cincinnati save $400,000–$600,000 a year in labor and other costs by using our product.”
And, he adds, “our product improves the look.”
Obstacles inherent in the use of ADCs include price, deployment, ballast, and longevity, Brad Uthe, I&E regional manager for JMI Covers, believes. While synthetic ADCs are more costly than soil, he says that many facilities have learned to calculate the life expectancy of those covers and work the numbers into their budgets. “The good news is, other than the cover itself, the landfills typically have all of the equipment needed to deploy and remove these types of covers.”
J&M Industries has invested in new products and techniques to increase the life span as well as the effectiveness of ADCs. Materials include both permeable and waterproof products that are available in fire retardant versions. “Additional reinforcement methods have been developed to take the stress that is incurred during the deployment and removal of the products, as well as to increase the longevity of the parent material,” explains Uthe.
Internal ballast can be added to products to eliminate the need for ballasting the product after it is deployed, saving both time and money. J&M specializes in custom covers to allow the landfills to specify exactly what material they want to use and the configuration of the cover. Uthe says this is flexibility not available in off-the-shelf products.
J&M’s products are fabricated using woven polyethylene, woven coated polyethylene, woven polypropylene, and coated vinyl. They are available in fire retardant versions and weights from 6 ounces to 18 ounces per square yard and are typically deployed using the equipment available onsite, whether that is a compactor, dozer, or front-end loader.
“The covers are fabricated with heavy duty ‘D’ rings on all corners and at various intervals around the perimeter,” continues Uthe. “Operators simply hook up to the cover, using log chains or straps, and pull the cover into position.” Removal is accomplished in the same fashion. “Synthetic covers not only save time and money over traditional soil covers; they also increase the ever more important air space that is available to the site.”
Using soil takes up air space. In addition, Jared Watson, business development manager for Rusmar Inc., points out that allowing soil to consume “six inches of landfill every day is expensive.” It’s also a lot of work: Crews have to excavate the soil and load it into dump trucks to haul it to the working face, where dozers push the soil into place. “It takes a lot of time, manpower, and machines.”
Sprays use a hydroseeder towed by a dozer or other machine that requires 2–3 guys and must be cleaned and maintained—and sprays don’t control odors, Watson states.
Rusmar combines a cover material—RusFoam ADC, a non-hardening protein-based foam that can be adjusted to last from overnight to over a weekend by changing the dilution ratio and the depth of coverage—with application equipment and storage and dilution equipment to effectively meet the performance criteria of Subtitle D.
RusFoam OC is a daily cover that creates a uniform, flexible, and impenetrable mechanical barrier that seals in odors, volatile organic compounds, volatile nitrogen compounds (such as ammonia), volatile sulfur compounds (such as H2S), and fugitive dust. RusFoam LM provides a long-term solution, while RusFoam LM forms a latex membrane that will provide control for up to six months.
“It’s like a soap concentrate,” explains Watson. “Just add water and mix.” The protein-based foam has the texture of shaving cream and is pressurized with air. No cleanup is necessary; the leftover material can sit in a tank 3–4 days. “Some keep the tank full all the time because it can help suppress fires.”
It solves a lot of problems, Watson believes. It’s “not bothered by wind or weather. Tarps have water runoff, but rain leaches through our cover; we can control it.” Because it dissipates every day, it doesn’t consume air space.
The material is applied by a self-propelled, single-operator application unit that will cover a 28,000-square-foot working face with a single fill in 40 minutes. It’s the second new-design machine, this time a proprietary design, Morooka-based rubber track machine that rides over the trash, leaving a blanket of foam behind.
A customized version was created for Waste Management, featuring a spray gun on the front and a controller in the cab “for areas you can’t drive over,” says Watson. It sprays both sides to avoid shadowing. It’s a one-man, one-machine operation that is faster than most alternatives.
Customers don’t have to buy Rusmar’s machine, Watson adds.“We give it to them and maintainit for them.” They even install a storage tank and a shed for mixing. The storage and dilution system is designed for bulk deliveries. The system automatically dilutes the concentrate and pumps the desired volume of diluted material to the machine, which uses compressed air to generate 50,000 gallons of foam per fill. The foam expands and seals, he notes.
Although Watson says, “You have to have an effective cover, not just the cheapest product,” he points out that their product is more affordable now. “We can match the cost of any spray.” This is a new machine and new technology that Watson deems necessaryfor large landfills. “This is where the industry is going.”
“It’s a value proposition,” suggests Knight. “ADCs should help reduce operating costs: fuel, labor, maintenance of yellow iron…” Savings has become even more of an issue, he believes, because of the pressure recycling has put on landfills.
Bruno believes that the main obstacle for ADCs is the initial cost, including materials, equipment, and manpower. To keep costs in check, he says most landfills review their inventory of equipment and determine which ADC will work best and also keep their costs down. For example, “if a landfill has a surface roller or compact roller, they may decide to employ a net or tarp-style ADC, but if they own a HydroSeeder unit, they may move forward with a different ADC.”
“Alternative Daily Cover options should be reevaluated periodically due to the increasing cost of the applied cover product,” advises Harrop. One-time-use products such as film, foam, or mortar mixes can be significantly more costly than reusable options like tarps. “The more costly options are sometimes accepted because they are still more economical than using soil for cover, but far less economical than reusable tarps.”
Harrop believes that objective cost analysis and comparison of cover methods will reveal that reusable tarps are the most cost-effective and efficient cover option. Others contend that sprays, foams, and films are closing the gap while providing more efficient cover.
Knight expresses concern regarding the quality of cover since the cost was driven down and the number of suppliers shrank. “I’m not sure the enthusiasm and focus are the same today.” Nevertheless, it’s important to get complete coverage that stands up to wind, weather, fire hazards, birds, and insects from a cost-effective product. Where once dirt was all that was used, and despite the fact that it’s hard to change minds, ADCs have become widely accepted and effective.