In the 1930s and 40s, compaction and use of a daily cover were the primary features that differentiated a sanitary landfill from a dump. Daily covers were introduced as part of an all-purpose control measure for perpetual problems like fires, blowing litter, odors, vermin and other disease-carrying vectors such as mosquitoes.
Traditional Daily Covers
In a typical sanitary landfill, waste is dumped, spread, and compacted over a landfill’s active face. At the end of the day, the active face is covered, often with a “traditional” daily cover, namely, a layer of soil which is then compacted. The soil layer is mandated to be at least six inches deep, but 12”-16” is the average because soil is difficult to spread evenly over the waste layer. On the following day, waste is dumped over the dirt layer and the process is repeated.
Using soil for daily cover is effective, but there are a lot of operational costs associated with using soil for this purpose:
- Suitable soil can be expensive and may be hard to obtain from local sources
- Shipping soil from outside sources adds to the base cost.
- Expensive equipment is necessary to spread the soil cover
- Fuel, labor, equipment, and maintenance for the equipment add to the cost.
- Labor and overtime costs, since applying the soil cover usually requires several hours of work each day after the landfill has stopped accepting material.
- The significant volume of landfill (referred to as airspace) occupied by dirt rather than waste represents a loss of potential revenue.
Some landfill operators advocate for scraping off soil used for daily covers prior to adding more waste. This practice reduces wasted airspace and eliminates potential issues with lateral migration of leachate and gases. While this works for some operations, the additional step does add time and complexity to daily management tasks.
Alternative Daily Covers
In response to these challenges, alternatives to the daily application of soil have been developed, and today, the term Alternative Daily Cover (ADC) refers to the use of any material other than soil as a daily cover for sanitary landfills. While alternative materials must fulfill the same functions as a traditional daily cover, they are intended to save time and money by eliminating the need to excavate soil, haul it to the site, store it, and go through the arduous process of applying it. Over time, the materials accepted as ADC have varied from state to state, but have included:
- foam products
- geosynthetic fabric or panels
- processed green material
- sludge and sludge-derived materials
- ash and cement kiln dust materials
- treated auto shredder waste
- contaminated sediment
- foundry sands
- energy resource exploration and production wastes
- compost materials
- processed construction and demolition waste
- mixed shredded tires and shredded paper sludge
- spray-applied cement
In today’s environment, focus has shifted to a broader concern with long-term environmental effects and sustainability. Some of those materials are no longer accepted as ADCs, while others are probably on their way out. New materials, improved practices and changing economic climate all influence landfill design and management. It’s critical for operators, engineers, and lawmakers to keep an open mind and an eye on best practices and new technology as our knowledge about waste management evolves.
