States make their own rules about alternative daily cover (ADC) materials for use by landfills. And while different states have different rules, all states approach the issue of regulating ADC materials in more or less the same way.
All states set requirements and approve ADC materials that meet those requirements. A landfill manager who comes up with an innovative idea for an ADC material may apply to the state and demonstrate how that material meets the requirements. If the appropriate state authorities agree, the material will be approved for use in the landfill.
“Pennsylvania is one of the leaders in terms of technological advances and regulatory requirements related to daily cover,” says Tim O'Donnell, general manager of Republic Services' Modern Landfill in York, Pa.
Pennsylvania's ADC regulations state: “A uniform cover of the approved daily cover material shall be placed on exposed solid waste at the end of each working day or at the end of every 24 hours, whichever interval is less. The composition of the daily cover material shall meet the following performance standards. The daily cover shall:
Prevent vectors, odors, blowing litter and other nuisances.
Cover solid waste after it is placed without change in its properties and without regard to weather.
Be capable of allowing loaded vehicles to successfully maneuver over it after placement.
Be capable of controlling fires.
Be consistent with the waste acceptance plan of the facility (if the facility isn't permitted to take the material, it cannot be used as an ADC).
Pennsylvania's regulations also require that landfills maintain a five-day supply of cover material on site.
Generally speaking, the regulations require the use of daily cover to promote safe working conditions in the landfill and to prevent landfilled waste and associated odors from harming or becoming a nuisance to neighboring communities. To date, Pennsylvania has approved nearly 20 ADC materials. They include foam, sludge-derived synthetic soils, water treatment sludge, fly ash, river dredge material, municipal incinerator ash, metal processing sludge, C&D waste fines and paper sludge.
Also: foundry sand, tarps, steel mill slag, steel mill scale, coal ash, mine spoil, refractory materials, auto-fluff, contaminated soils and Posi-Shell, a thin, spray-on cement-based product.
The Pioneer Crossing Plan
Landfills build daily cover strategies around materials approved by their states. At the Pioneer Crossing Landfill in Birdsboro, Pa., General Manager Thomas O'Conner has used three of the state's 16 approved ADC materials: foam, tarps and contaminated soils. Of the two commercial ADCs, O'Conner prefers tarps. And he uses contaminated soils whenever those materials become available.
Pioneer Crossing, which is owned by Audubon, Pa.-based J.P. Mascaro & Sons, takes in an average of 1,550 tons of solid waste per day. Two tarps, each 80 feet by 60 feet, provide daily cover for the relatively small daily disposal area required for that volume of solid waste.
Prior to 1999, the facility used foam. “But we found there was a lot of waste with foam,” O'Conner says. “The disposal sites would get too large, and we would tend to foam areas outside the daily disposal area. In addition, there were costs to repair and replace damaged application equipment.”
In 1999, O'Conner carried out a one-year demonstration project with tarps and earned approval from Pennsylvania's Department of Environmental Protection. He finds that tarps offer several benefits important to Pioneer Crossing.
“They are relatively simple to deploy,” he says. “They require no special equipment to put out. We don't use an automated system. Our employees deploy the tarps. They satisfy all of the state's requirements for ADC. At $875 for a tarp that lasts several months, they are cost-effective.”
“The biggest benefit is the savings on air space,” O'Connor adds. “We net about 0.80 tons per cubic yard of in-place density, and tarps take up literally no airspace.”
Drawbacks of tarps include exposing employees to the waste as they deploy the tarps, O'Conner says. Tarps can tear as they are pulled across waste, and they can be difficult to deal with on windy days. Landfill personnel use a sewing machine to repair the occasional tears.
“Foam and tarps are the only commercial daily covers that we have used,” O'Conner says. “However, we also use contaminated soils as they become available — that, of course, is cost-effective,” since the facility charges a tipping fee to accept those materials and then puts them to productive use.
Some landfills have found that automatic tarp deployment devices can lengthen the life of tarps, reduce labor, and, over time, reduce costs even more.
Menu Of ADCs
General Manager Tim O'Donnell has worked out a basic menu of daily covers that make sense for the 5,000 ton per day Modern Landfill in York County, Pa., which requires about an acre's worth of daily cover each day. “Our menu always includes a component of clean soil, which I think is superior to all other covers,” he says. “Aesthetically, it is superior, and I have a cheap source close by.
“We use several alternative covers where it makes sense,” he adds. “We have two regular ADC sources for incinerator ash and auto shredder fluff, which we use for economic reasons — they produce revenue. And we use tarps. I like tarps because they consume no airspace. They are probably the cheapest of the commercial ADCs.”
At one time, most landfills used six-inches of clean soil as a daily cover. During construction, large quantities of clean soil were excavated and stockpiled.
“But as landfills got bigger, the cover story changed,” O'Donnell says. “Larger landfills tend to deplete on-site soils and make it necessary to look elsewhere for cover material. If there is no dirt on site then you have to buy it. That's when ADCs became important.”
O'Donnell goes on to say that his first instinct is to find ADCs that produce revenue, such as incinerator ash, auto fluff and foundry sand. Another revenue-generating material that is receiving a lot of attention today is construction and demolition fine, a soil-like material left over when construction and demolition materials are processed for recycling.
O'Donnell also pays for commercial ADCs for certain daily cover applications. “In my opinion, commercial ADCs have one great advantage over the others: they conserve airspace,” he says. “Tarps take up no space at all, and they can be reused.”
At the end of each day, O'Donnell puts together a daily cover menu. Flat surfaces that will be driven on the next day receive clean soil, which provides the best seal and the sturdiest base. The slope of the working face, which won't be driven over, receives ADCs.
Which ADCs? Depending on availability, cost and revenue, application procedures, effectiveness and the preparation of the waste surface, O'Donnell makes his selections.
“I might role out a tarp on slopes that aren't very smooth,” he says. “In areas where we will ultimately grow grass, we'll take more time to prepare the surface and use ash or auto fluff.”
“My chief concern in selecting ADCs is aesthetics,” O'Donnell adds. “At various times over the years, we have tried to minimize the use of soil. After doing that, I would think that it didn't look as good as I want it to look. In my opinion, the success of a landfill has a lot to do with what the surrounding community thinks of you. The old days of only worrying about what goes on inside the gates are gone.
“As landfill operators, we must consider and evaluate the performance of daily covers. As members of a community, we have to be concerned with the impressions we create and what our neighbors think of us. That's why I think aesthetics are critical.”
Michael Fickes is a contributing writer based in Cockeysville, Md.