Today's Dirt is EPA’s prescriptive cover material, but does it make sense?

By Charles D. Bader

It is estimated that 20%-30% of the material in landfills will be just dirt when they close. Not only is this terribly expensive in terms of lost tipping fees, but it also defeats the nationwide drive to extend the lives of landfills to the maximum possible. This article offers five different answers to this dilemma—all called alternative daily covers (ADC).

Until recently, the true cost of using dirt as a daily cover in landfills had always been hidden by the ready availability of this commodity. The amount needed to add 6 inches of dirt (or, more typically, a foot of dirt) four times a week wasn’t a big cost item on the budget sheet. Often, deals could be worked out so that the dirt cost some landfill operators nothing. But then, as operating costs began rising sharply and local landfills began filling up without a practical way to replace them, some landfill operators began calculating the true value of landfill airspace and the cost penalty of using all this dirt cover each day.

Several years ago, when we last looked at this issue in-depth, David Lowry, landfill manager of the Olinda-Alpha Landfill in Brea, CA, calculated that by replacing dirt cover, his 7,000-tpd landfill would conserve 106,000 cubic yards of space each year. This additional capacity, if used to accept more waste per day, would yield a net present value of increased gate income of more than $10 million before its projected closure date of December 2013. And smaller landfill operators reported significant cost savings too. Tony Knight of New Waste Concepts Inc. in Erie, MI, calculated that for a landfill with an average working face of just 4,000 square feet, the daily 11-inch soil cover totaled 38,519 cubic yards per year. That loss of airspace with nonrevenue-producing soil meant an annual cost of lost revenue of $397,800 and a reduction in the remaining life of the landfill of 44%.

A major step in attaining those savings would be to substitute an ADC that has little or no thickness. And regulations for such ADC products have emerged. The ASTM International’s standard guide for evaluation and selection of ADCs for sanitary landfills (ASTM D 6523-00), assists in the understanding of performance features needed to determine the extent and degree to which different ADCs are able to “control disease vectors, fires, odors, blowing litter, and scavenging, without presenting a threat to human health and the environment,” as intended by EPA regulations.

Today, numerous ADC products meet those standards and are increasing in use. The balance of this article describes five US landfills, all of which are meeting these requirements and realizing significant savings and operational improvements—yet each one is using a different ADC product.

City of Arlington, TX
The city of Arlington’s landfill is a 551-acre, 1,700-tons-per-day site that has been serving the greater Dallas-Fort Worth area since the early 1960s. In 1994, the facility was permitted to conform to the then-new Subtitle D regulations. At the time, the landfill had about 20 years remaining at its current fill rate, but the operators decided to plan ahead both to save costs and extend the life of the landfill. “We’re located in the metroplex between Dallas and Fort Worth,” explains Solid Waste Lease Administrator Bob Weber, “and land values had already begun to get outrageously high. So who could predict 20 years into the future what the costs of a new landfill would be and if we would be permitted to build one? Besides, the nearest reliable source of soil was 100 miles away.”

For this reason, the operators began looking at various other ADCs as a way to conserve airspace. In 1997, the site began a 180-day trial of Soil Equivalent Foam from Rusmar Inc. in West Chester, PA. “Rusmar foam demonstrated its ability to contain odor, maintain foam depth, and eliminate wind-blown material,” Weber says. “And the grooming of the workface by using the self-propelled application machine allowed for a uniform 3-inch-depth cover without increased cost. Bottom line: The savings and improvements we projected at that time were enough that the city was very, very interested in making the change.” Therefore, the city commissioned Rusmar to provide a full turnkey system, and the firm continues to be the ADC of choice at Arlington’s landfill today.

“Soil Equivalent Foam is a water-based, non-hardening product that ships as a liquid concentrate by bulk tanker load,” explains Rusmar’s Rebekah Gormish. “The tanker weighs in on the site’s scales and unloads the concentrate into a bulk storage and dilution system [BSD7000] provided by Rusmar. The BSD7000 is an insulated, heated, 7,000-gallon tank, with a microprocessor and transfer pump to automatically dilute the concentrate and fill the foam unit.

“Soil Equivalent Foam is applied with a Rusmar-provided Pneumatic Foam Unit [which, like all needed equipment, is included in the price of the foam concentrate]. Even for larger sites over 1,000 tons per day, such as Arlington, our self-propelled PFU2500/60 makes alternate daily cover application a one-man process. The operator trams the unit to the BSD7000, hooks up, and inputs the number of gallons of dilute needed. When the operator is ready to apply the foam at the face, he opens two air valves and two chemical valves at the rear of the unit. The operator then sits in the temperature-controlled cab and drives over the face, deploying a 12-foot-wide foam blanket. Coverage can be monitored through Intec cameras on the rear and a monitor in the cab. The concentrate can remain in the storage tank until additional foaming is required, or for a period up to seven days.”

“The foam blanket remains moist throughout its life,” Weber says, “and when covered with additional waste the next day, it collapses, leaving no solid barrier behind. In 2004, that provided us with airspace savings equivalent to $1.2 million in tipping fees as well as savings of $360,000 in dirt acquisition, transportation, and spreading.”

Larimer County Landfill, Fort Collins, CO
The Larimer County landfill is on a 640-acre site, of which half is reserved for the landfill and operations and the other half for the borrow. There was certainly no shortage of soil in the borrow, but when Solid Waste Director Steve Gillette came onboard five years ago, he became concerned about the airspace costs created by adding at least 6 inches of dirt each day as cover. By his calculations, adding this 330 cubic yards of soil each day would significantly reduce the life of the landfill to as little as three years. And at the same time, of course, the daily dumping of 330 cubic yards of soil would use up valuable space that could otherwise generate tipping fees for MSW. Faced with this dilemma, he began looking at various ADCs.

“We have some local conditions that ruled out some otherwise excellent alternative covers,” he recalls. “Perhaps the most important of these was the wind here in Fort Collins. The gusts are so strong that the laying of tarps and film would have been impractical. That, plus some factors such as winter weather and the close proximity of neighboring residences, led us to select TOPCOAT slurry spray from Central Fiber Corporation in Wellsville, KS.”

“TOPCOAT is an alternative daily landfill cover manufactured from post-consumer paper, chemicals, and other proprietary ingredients,” explains Dale Deardorff, market development coordinator for Central Fiber “Thus, all ingredients are nontoxic and biodegradable. In fact, TOPCOAT meets all federal regulations. It’s an easy, inexpensive way to control disease vectors, fires, and odors, blowing litter and scavenging. Sprayed as a slurry, TOPCOAT forms a blanket to control disease vectors, fires, odors, blowing litter, scavenging and erosion.

“TOPCOAT’s convenient one-bag system makes mixing a snap. It’s applied with regular hydroseeding equipment. With TOPCOAT, there’s no mixing time—and no waiting to spray. It takes only about 20 minutes to cover the working face of an average-sized landfill—and TOPCOAT is fully effective as soon as it’s applied.”

Gillette’s experience with TOPCOAT seems to corroborate all of these claims. “Every year since the fall of 2001,” he says, “we’ve been able to put that nonproductive 330 yards’ worth of space to use for our real job here—landfilling MSW. And we can indeed apply it in 20 minutes with our Bowie hydroseeder. We get double duty from the hydroseeder, too. We also use it for temporary slope cover, and if the occasion ever arises, we’ll be able to use it to fight fires.

“Our neighbors are happier, too. We no longer get complaints about blowing litter from them or from the regulators. Nor do we get complaints about odor or scavengers. The seagulls must hate TOPCOAT because they rarely come by anymore.”

Asked to quantify cost savings, Gillette could only say they were “tremendous.” In addition to the airspace savings, he points out, there are the labor savings in laying the slurry blanket in just 20 minutes and not having to dig and transport all that dirt. Where once the landfill needed two scrapers, now it gets on just fine with one. And he knows that he is delaying that day when the landfill finally must be closed.

Craighead County Landfill, Jonesboro, AR
The Craighead County Solid Waste Authority had been placing 6 inches or more of clay as daily cover in its 500-tons-per-day landfill. Four times a week, the operator would spend an hour and a half spreading the clay, and the next morning he would spend another half hour scraping it off. The costs proved to be exorbitant, according to Guy Enchelmeyer, the current executive director of the Authority. In addition to the labor and materials that were being expended, they were facing a shortage of the clay for other purposes. And, of course, there were the costs of using up airspace with this nonproductive material that impeded the garbage-on-garbage approach that their engineers were recommending for bioremediation of the refuse.

For these reasons, the landfill operator decided to replace the clay with an ADC. After evaluating a number of ADC options, Enchelmeyer says, they settled on EnviroCover, manufactured by EPI Environmental Products Inc. of Vancouver, BC. “It has been an ideal product for our application,” he says, “and we have been using it successfully since 1998.”

“EnviroCover is a specially engineered degradable polyethylene film uniquely categorized by the ASTM as a ‘non-reusable geosynthetic,’” reports Kenneth Lee, waste management advisor for EPI’s EnviroCover Division. “It does not require removal or retrieval once it is placed on the working face of a landfill since it is manufactured with our patented ‘pro-degradant’ additive. Degradation of the film is initiated through the exposure to heat, mechanical stress and/or sunlight. Any one of these factors is enough to start the degradation process. When the film is used on the surface of a landfill, all of these exposure conditions are present. Upon its burial, EnviroCover is impermeable within the designed exposure period and helps to minimize rainwater infiltration, thus decreasing undesirable leachate generation. However, the heat and the mechanical stress inside the landfill will sustain the degradation process, and the film will dissolve in 14 to 21 days.

“Moreover, the film maintains extremely good tear and puncture resistance and elongation characteristics during deployment and is designed to meet the mandatory requirements for alternative daily cover. As a degradable film, EnviroCover will not interfere with normal landfill mechanics. Leachate and landfill gas can continue to migrate within the landfill. The waste can continue to degrade and settle, enabling partial recovery of valuable landfill space.”

“Any landfill space recovery from settlement and degradation of the waste is over and above the space savings we get each week from reducing our daily cover from 6 inches or more to nothing as the film dissolves,” Enchelmeyer adds. “We were applying 500 cubic yards of clay to provide that 6 inches of clay cover four times a week. At 1,000 pounds per cubic yard, then, we were landfilling 1,000 tons of clay each week. At our tipping fee of $26 per ton that meant that landfilling clay instead of MSW was costing us $26,000 per week. That was reduced when we started next-day scraping of the clay, but that introduced labor costs to accomplish the scraping. In all, it was taking us at least two hours a day to place and then partially remove our daily cover. With the film it only takes us 15 minutes.”

That rapid deployment is made possible with EnviroCover’s Deployer, which attaches to the landfill’s bulldozer. The Deployer fully automates the waste-covering process by deploying EnviroCover rolls on the waste while simultaneously distributing ballast to anchor the film. It is designed to utilize a variety of ballast, such as sand, gravel, ground tires, glass, and soils, commonly available in landfills. “No condition—not high winds, not rain, not snow or ice—prevents us from deploying the film,” Enchelmeyer says. “We cover our 100-foot-by-50-foot working face in four or five passes. That sure is faster, easier, and cheaper than spreading 500 cubic yards of clay.”

Gallatin County Landfill, Bozeman, Montana
When Larry Pierce became director of solid waste at Gallatin County, the landfill was a “push-and-cover operation,” as he describes it. And there were problems. The landfill operator had been using 6 inches of dirt for daily cover, but there was a growing shortage of soil locally in Montana. Of even greater concern, the facility’s airspace usage was quite high, 15% higher than the already high national average. He concluded that to be really successful, he would have to structure the landfill’s operations around ADC.

Pierce’s attack on the problem involved two steps. The first step was to significantly improve the compaction of the waste from its level of only 780 pounds per cubic yard, well below the national standard of 900. To achieve this, he began to make the slopes more gradual, and today the slopes are 6:1 or less. At the same time, they ran their packers much more aggressively. As a result, their compaction increased to 1,300 pounds per cubic yard last year, and it is currently at 1,402.

The second step was to select an alternative daily cover. Pierce evaluated a number of products and eventually selected clay. But this was not the kind of clay that had plagued Guy Enchelmeyer. It was a specially formulated liquid clay supplied by the Enviro Group Inc. of Greenwood, IN. As described by Enviro Group’s John Garver, “Our Formula 480 Liquid Clay is a biodegradable clay concentrate that combines the properties of minerals and tight film to give both strength and resistance to water. It does not flow when applied, and when it dries, it will stay in place during even the most extreme weather conditions.

“When it is mixed with water, at any of various mixture ratios, a thick film is sprayed in a single application using our spray equipment. A single 55-gallon drum mixed with 2_ times that much of water results in almost 200 gallons of usable product that will typically cover more than 19,000 square feet. When applied, this mixture has a semi-paste consistency. The applied film is a so-called breather type; when it is initially applied, it permits needed ground vapors to escape through the film and at the same time is resistant to water. To date, Formula 480 has proven its effectiveness in landfills for over 10 years. It has many attractive features, the most attractive of which is the amount of money it will save a landfill.”

Pierce has kept extensive cost records that corroborate that claim. “The startup costs were minimal,” he says. “The sprayer that attaches to our track-loader was the major item, costing us $22,000 when we acquired it. And the operating costs are quite reasonable. A truckload of the Formula 480 costs $19,000, and with the 2.5:1 water-to-product ratio we use will last three months. It only takes one employee 15 minutes to apply daily cover. All in all, therefore, our operating costs are only 3–4 cents per square foot. In our most recent fiscal year, our operating costs were $275,119 less than we were experiencing when we were using 6 inches of soil as our daily cover.

“Our savings in airspace potential were even greater. We have calculated that the Fiscal Year 2005 airspace savings resulting from our compaction/ADC program were 46,258 cubic yards compared to our airspace use three years ago when we had the lower compaction and the dirt cover. At our current tipping fee of $21.10 per cubic yard, that represents an annual savings of $976,044. These improvements were very timely, too, since we have increased our daily intake of MSW from 120 tons to 500 tons when another local landfill closed. Every yard of that airspace savings will pay off quickly in fees from this additional MSW intake.”

City of Santa Cruz, CA, Resource Recovery Facility
Santa Cruz’s Resource Recovery Facility includes a small, 200-tons-per-day landfill that has been operating since 1926. In recent years, the operators had been using as much as 12 inches of soil for its daily cover. Because of a deal made in 1998 with a nearby cement plant to get dirt in exchange for shale from one of the landfill’s future cell sites, the dirt was available at no cost. However, when Jose Gamboa came onboard several years ago as superintendent of solid waste, he concluded that the landfill’s airspace penalties were too high even with the “free” soil.

“I wanted to use tarps to meet our daily cover requirements because they wouldn’t consume any airspace,” he says. “But because of the way the landfill had developed, the face was 200-feet-by 40-feet, a size that we felt made the use of tarps impractical. We didn’t give up on tarps, though. Instead, we took steps to reduce the size of the face.”

In 2002, Gamboa did an informal survey of incoming customer traffic. He discovered 80% of his customers were small users and that almost half of these were delivering their waste to the face rather than to the public tipping area that had been established just for small users.

Therefore, he instituted a campaign to divert as many small users as possible to the public tipping area. There, their refuse was sorted to remove recyclables and hazardous waste, and the MSW to be landfilled was put into rolloffs, which were then sent to strategic areas where fill was needed to help shrink the size of the face.

“This approach had a number of advantages, such as diverting a very high percentage of hazardous waste,” Gamboa says, “but perhaps the most useful one from a landfill management standpoint was the fact that we could both shrink and shape the cell for efficient operations. Today, our face is 60% smaller than it was prior to 2003, and its 80-feet-by-40-feet size both lowers our O&M costs for compaction and is amenable to the use of tarps for alternative daily cover. We now can cover our entire area with tarps, which we spread and remove each day with Tarpomatic’s Automatic Tarping Machine.”

According to Tarpomatic Inc. of Canton, OH, each Automatic Tarping Machine (ATM) is custom-fitted to be lifted and transported by the blade of a bulldozer and offers quick and easy hookup. The product uses a hydraulic drive motor and engaging system to wind and unwind the spool with variable-speed control. Spools can be disconnected and reconnected to utilize one ATM with multiple spools. Controls are mounted in the cab of the dozer or compactor to give the operator control of the engine, height and tilt of the spool, and forward/reverse rolling.

This allows for even tracking when winding and unwinding tarps on uneven terrain. The product is designed for 40-foot-wide panels of various lengths. The spool is capable of holding three 40-foot–by–100-foot weighted tarps.

Gamboa makes extensive use of tarps, but they are not the only ADC medium he employs. Depending on availability, he uses greenwaste mulch or ground-up C&D refuse for his daily cover several days each month.

However, he calculates, he uses tarps 77% of the time. And he uses very little dirt. In fact, he says, the use of dirt for daily cover has declined from an average of 38,900 tons per year in 1996-2003 to just 1,600 tons in fiscal year 2005.

This generates substantial savings in airspace utilization, of course, but Gamboa tends to stress other benefits, too. “Eliminating all this dirt enables water to percolate through layers of compacted refuse,” he points out. “This accelerates the decomposing of the organics, providing us with two benefits. First, the process generates methane, and we use that methane to generate enough electricity for 1,200 homes. That means that 10% of the homes in Santa Cruz get their power from our little landfill.

“Second, we calculate that over time this decomposition will enable us to get 40%-60% of our landfill space back. Clearly, this rate of settlement will be much greater and faster than that of a landfill that continues to use dirt for its daily cover.”

Gamboa feels very strongly about this issue. “There is a fundamental flaw in how the EPA and the states have looked at landfill conservation,” he says. “They have extensively supported and regulated the diversion of recyclables and greenwaste from landfills. Here in California, State Act AB939 mandates that landfill life be extended. But neither AB939 nor any other law or regulation I have heard of deals with dirt management despite the fact that in California at least, an estimated 20%-30% of landfill capacity is consumed by counter-productive dirt. Diversion of dirt is still a largely untapped resource for extending landfill life, but no one even keeps records of dirt consumption, much less takes steps to limit it. Why not?”

Why not, indeed?

Based in Los Angeles, Charles Bader writes on diverse technical topics.

MSW - March/April 2006