There are quite a variety of ADCs in which to choose. Be cognizant of your working conditions and opt for an ADC that works best in your environment.
By Marlon Yarborough
In the late 1980s, the company I worked for was approached by a gentleman named Beanie Acosta from a Waste Management facility in Southern Louisiana. His operators were having difficulty spreading the thick, sticky “gumbo mud”, indigenous to the area, evenly over their active working face. We were able to manufacture an alternative daily cover tarp that not only solved their coverage problem, but also sped up their closing time. This style ADC tarp was referred to as the “Beanie Blanket” in the industry for many years and demonstrated the value of an alternate daily cover before the majority of landfills ever used any type of daily cover.
Pre Subtitle D, my job consisted of convincing landfill managers, supervisors and operators that their facility would greatly benefit by using ADC. This, of course, was before the U.S. EPA made it mandatory for each class I sanitary landfill to cover their active working face at the close of business every day. I believe the most common question posed to me after my opening sales pitch was, “Why the heck would I want to do that?” Of course “heck” was rarely the chosen word in this question. It took a good bit of persuading, but I was able to get my point across well enough that many landfills started using our cover tarps.
Then, Subtitle D was issued by the U.S. EPA in late 1992, which addressed and made mandatory many very important regulatory issues regarding landfills in the U.S. Among these issues, included the mandatory usage of daily cover. Daily cover is defined as a 6″ minimum layer of compressed soil or earth, that is laid on top of each day’s deposit of waste on an operational landfill site. Its function is to control disease, vectors, blowing litter, odors, scavenging and fires. It also allowed for the use of alternative type daily cover material to be used in lieu of the earthen material. This made my job a little easier.
It did not take long for landfill management to understand that by using the required 6″ of earth to cover their active working face, they were filling their private company’s or municipality’s expensive, lined, profit generating cells with nonprofit generating dirt, sand, clay, and, as Beanie put it, gumbo mud. Why fill valuable airspace that you spend countless hours getting approved for permits and millions of dollars in construction fees with earth that was probably pulled out of the cell in the first place, or even worse, paid for and trucked in from offsite?
Although Subtitle D did allow the use of ADC for cover material, it was loosely defined, and needed to be approved on a case-by-case basis. Since this concept was new to most people, it took quite a while for each modification to be approved through each state’s enforcement agency. In September of 1993, the EPA released their project summary on “The Use of Alternate Materials for Daily Cover at Municipal Solid Waste Landfills”. This outlined many types of ADC that had been approved up to that point, which in turn eased the restrictions and long approval waiting time limits.
Which ADC Will Work Well for Your Landfill?
Basically, ADCs are broken down into two types. Commercially Available Products (non-waste derived materials) include reusable geosynthetic tarps (pull on and automatic tarping system), non-reusable geosynthetic fabric, spray on foams and slurries. Indigenous Materials (waste-derived materials) include certain industries cast off, unused materials that need to be disposed of.
Commercially Available Materials
These materials will have to be purchased, but they also leave no gap between each day’s trash layers, giving you the maximum use of airspace savings. As mentioned above, geosynthetic tarps can be dragged by a piece of equipment, pulled on by hand or laid down using an automatic tarp-rolling machine. Reusable tarps are widely considered to be the quickest and least costly form of the alternate daily covers.
Pull On Tarps
Tarps have been used since the 1980s and are used throughout the industry. Sizes can vary to fit most any size working face. They are, however, subjected to being dragged over the working face, which is a brutal environment. This rough application can quickly damage and shorten the tarp’s life expectancy.
Automatic Tarping Machine
The first ATM was built in the early 1990s. The company saw the potential of using tarps as a daily cover and took it to the next level. Its design improves workers safety and eliminates possible injuries while dragging or maneuvering tarps into place. The tarps are rolled over the working face, thus reducing rips and tears to the fabric. Their self-contained unit, with adjustable mounting brackets, uses dozers or compactors already onsite. Each spool has the capacity to hold up to 300′ of tarps that vary in widths of 20′, 30′, 40′ and 50′. All flame resistant and water resistant tarps are weighted with chain down each edge and cable on each end and every 11′ throughout the body. The crossing cables are attached to each end of the pocket to keep the tarp at its desired width. This weight keeps the tarps in place during high wind situations. Only one machine is needed for even the largest landfill as multiple spools can be easily added for deploying and retrieving tarps. A handy option is the deodorizer system which has a large tank mounted safely on the machine’s frame with durable spray nozzles mounted on the full width of the tarp for complete coverage of your open fork face. Another advantage of this system is that the tarps are reusable and only need to be replaced after 18 to 24 months of use.
Non-Reusable Geosynthetic
Onsite machinery is used to tow specific equipment that places and anchors, with sand or dirt, a thin geosynthetic fabric. The fabric is left in place for the application of the next day’s trash. Since the fabric is non-reusable, it needs to be purchased on a continuous basis.
Spray on ADC
Spray on ADCs are usually slurries or foam. The most common components used are resins, soaps, newspaper, fly ash, wood fiber, clay binders, reinforced fibers, clay binders and polymers. These components are mixed with either water or leachate to its desired consistency using the supplier’s specialized equipment, which is usually towed or skid mounted, but specifically designed to be used with a particular product. The contents are sprayed over the working face in roughly a 1/2″ to 6″ layer. The unit will then need to be properly cleaned for the next day’s use. Application may be difficult in windy or rainy situations. These systems work very well and the product needs to be continuously purchased if used on a daily basis.
Indigenous Materials
Many landfills are able to take advantage of certain industries in their region that produce a waste derived product that needs to be disposed of and has been approved for ADC. Landfill management will have to weigh the option of using this material, which usually always generates less revenue than their normal MSW waste, or use a commercially available ADC that uses no airspace. Some of the more popular of these materials include: fly ash, contaminated soil, foundry sand, shredded tires, paper mill sludge, automobile shredder fluff, shredded green waste and shredded wood waste.
The problem lies in the amount of material that is brought in. If you don’t receive enough of this material, you will need to use earthen material of another form of ADC to finish covering your working face. If you bring in too much material, and spread the product over the working face thicker than required, again, you are filling up your limited airspace availability with a product that generates less than impressive revenue for your company or municipality.
As you can see, there are quite a variety of ADCs in which to choose. Be cognizant of your working conditions and opt for an ADC that works best in your environment. Many landfills employ the use of multiple ADCs. This is probably the best route to take, since variables change on a weekly, or even a daily basis. Since the main objective for every landfill is to save valuable airspace for its highest paying commodity (not dirt), the use of ADC is, after all, a no brainer. | WA
Marlon Yarborough is the sales and marketing manager for Tarpomatic (Canton, OH). He has 26 years of experience in the alternate daily cover industry. He can be reached at (800) 500-5069, via e-mail at [email protected] or visit tarpomatic.com.