Sanitary landfills are an indisposable aspect for maintaining sanitary living conditions. "Every year Americans discard, directly and indirectly, an amount of waste equal in weight to the Statue of Liberty",(McBean et al.,7). With this in mind, the need for landfills is very apparent.
The Virginia solid waste regulations define a sanitary landfill as "an engineered land burial facility for the disposal of solid waste which is so located, designed, constructed, and operated to contain and isolate the solid waste so that it does not pose a substantial present or potential hazard to human health or the environment."
Most landfills are owned and operated by private corporations or municipalities. Private landfills usually are run by waste management industries. Municipal landfills are typically under the authority of local governments, or in other words, the public sector. In some cases, municipal landfills are operated by a single local government entity. Other times, several local governments combine resources to create an authority. These authorities in turn manage a single sanitary landfill.
From a Federal standpoint, there were no regulations governing the construction and operation of sanitary landfills until 1993. Individual states may have had regulations on the books concerning the operation of landfills. In 1988 The State of Virginia adopted it's own solid waste regulations. In 1991, the federal government passed a law under Subtitle D regarding construction and operation of sanitary landfills. These laws were implemented in October of 1993. After this, almost every state adopted their own implementation plan. These state implementation plans are required to be as stringent or tougher than the federal guidelines.
An adequate lining system is a necessary component for any sanitary landfill. "The liner is designed as a barrier to intercept leachate and to direct it to a leachate collection system", (McBean et al.,207). Collection and treatment of this leachate must occur to prevent contamination of local groundwater.
Here we have permeable liner placed over top another synthetic. This liner allows for stone to be applied without fear of tearing the impermeable synthetic. In the upper left hand corner is a leachate collection pipe.
There are several different types of liners that may be used in a sanitary landfill. The major consideration when deciding on a material for the liner is its permeability, and what type of leachate will be exposed if the liner leaks. The first types of liners that were used were those constructed of natural materials. The most popular of natural materials was clay. "High clay content was considered useful not only for low permeability but also for potential contaminant retardation; clay has an ability to attenuate many of the chemical constituents found in leachates" (McBean et al., 207).
Machines compact the clay to meet required density and depth. (Photo courtesy of Schnabel Engineering Associates, Inc.)
When synthetic liners were introduced, many people thought that if two synthetic liners were put down, there would be virtually no leaking. However, any breach of the liner will allow leachate to flow through the torn liner, especially if the material below has a high permeability. The standard for today calls for two liners, one synthetic and one consisting of clay.
Virginia regulations require a double liner system. The clay portion of the liner must have a minimum of two feet in thickness and a permeability less than 1x10^-7 cm per second. The synthetic portion must have a thickness of 60-mil (about 4.5mm) and should be compatible with the solid waste and the leachate. Utilizing a double liner system including natural compounds and synthetics allows for the use of the best that each system has to offer. Clay has a very low permeability and can not be torn or subject to holes. Synthetics have a permeability that is virtually zero. By placing the synthetic on top of the clay we arrive at the best possible solution.
Looking right to left we find the bottom clay liner, the top double synthetic liner, and then gravel being applied. (This photo is from the Hoechst Celanese Landfill in Narrows, Va. Courtesy of Schnabel Engineering Associates, Inc.)
The permeability of the bottom layer of the liner must be lower than the top liner. Leachate can not be allowed to sit between the two liners and accumulate. This would eventually degrade the liner system and cause it to work ineffiecently. Therefore the synthetic liner is usually always placed on top of the clay liner.
video clip of installation of liner This movie
shows workers rolling out the synthetic liner.
Here, a worker welds two strips of synthetic together to ensure no leachate can escape.(Photo courtesy of Schnabel Engineering Associates, Inc.)
The vehicles at the bottom of the picture are compacting the clay layer to specifications before applying the synthetic.
With new regulations and strict controls on what goes in our landfills, hazardous chemicals and dangerous substances have almost been eliminated from sanitary landfills. According to Justin Babendrier (Research Associate, Virginia Tech) about 1% of all waste in a sanitary landfill is hazardous but with the dilution factor of 99% trash it has no great effect. Regulations and advanced capping systems have also limited the amount of water entering the landfills, minimizing leachate volume and it's associated waste products.
When we look at these facts, it seems as though we have accomplished something. When we take a closer look however, one has to wonder what that is. Water flowing through the ground aids in the natural degradation process of trash. The big problem designers faced was the fact that many harmful substances were found in sanitary landfills. When water percolated through, harmful substances dissolved in the water and eventually contaminated aquifers. With strict regulations the amount of contaminants being placed in the landfills has been reduced. Regulations also require that the landfills be capped so that no water may enter. Now we have landfills full of trash that can go a very long time with only minimal degradation.
Send comments or suggestions to:
Student Authors:
and Kathleen Naiman
Faculty Advisor: Daniel Gallagher, dang@vt.edu
Copyright © 1998 Daniel Gallagher
Last Modified: June 7, 1998
