This course should provide landfill owners, managers, operators, consultants, regulatory agency specialists and others interested in the solid waste industry with the latest information regarding the development, design, operation, closure and long-term maintenance of landfills. The course also is intended to raise the awareness of issues relevant to successfully operating a landfill, but is not intended to provide detailed technical calculations.
The sanitary landfill originally was conceived in the 1960s as a planned method of solid waste disposal. Prior to that, municipal solid waste generally was disposed of in some type of organized or unorganized fashion in open dumps. The waste may not have been covered, and it likely was burned as part of the disposal practice. In the 1970s, initiatives were aimed at improving solid waste disposal practices.
The classical definition of a sanitary landfill is an engineered facility for the disposal of municipal solid waste (MSW) designed and operated to minimize public health and environmental impacts. The typical landfill consists of several cells in which the waste is systematically placed. The landfill base usually consists of a liner that minimizes the leakage of liquid waste materials from the landfill into the groundwater system. As the waste is built up in layers it is covered daily to prevent paper, dust or odors from escaping into the environment. The entire system is a very sophisticated facility that requires millions of dollars to build, and the services it provides often is valued at millions of dollars per year.
Shift in Landfill Numbers
The number of landfills in the United States significantly declined between 1970 and 2001. In Wisconsin, for example, at one point there were more than 5,000 local land disposal sites. There now are approximately 40 municipal waste landfills and approximately 40 industrial waste landfills in the state.
As the concept of sanitary landfilling spread across the United States, dumps were systematically closed and waste was moved to larger consolidated facilities that operated in a more organized manner. Then as older facilities became obsolete or were filled, the nation gradually began to increase its reliance on bigger, consolidated regional landfills that serve a wide area and a large population.
Since 1989, the number of municipal solid waste landfills in the United States has declined from 7,379 to 2,216 in 1999. During that same period, the average amount of waste received by a landfill has increased from 92 tons per day to 300 tons per day. Sanitary landfilling has improved environmental and health protection systems.
Today, smaller disposal facilities still exist in less populated parts of the country. For instance, small, 10- to 20-ton per day facilities exist in certain rural areas. Nevertheless, the trend has been toward regionalization. [See state distribution in “Number of Landfills” in PDF file]
Of the facilities currently in operation, most were constructed in the past 10 to 15 years. All are regulated under federal and state standards that mandate extensive environmental, management and financial controls.
The typical landfill will operate between 10 and 20 years. During this time, waste that is placed in the landfill will undergo complicated decomposition processes. These processes will result in the release of liquids that must be contained at the base of the landfill, and the release of gases that must be managed as they escape through the landfill’s cover.
Many options are available to operate specific disposal facilities. These include various methods of preparing the waste before it arrives at the landfill, compaction procedures for waste placed in a landfill and alternatives for managing the leachate and gas that emanate from the waste. Each of these aspects of the landfill will be detailed throughout the 12-month course.
During the 20-year period from approximately 1975 to 1995, landfill development and operation underwent radical changes regarding the application of technologies. These changes included the development of sophisticated groundwater monitoring systems, implementation of liner leachate collection systems, the installation of geosynthetic covers and the introduction of large waste compaction equipment.
The most recent innovations have been associated with developing alternative cover materials that are installed during the landfill’s final closure. Alternative earthen covers, which have been researched extensively at the University of Wisconsin, have been used in the western part of the United States and have provided a great cost savings when compared with geosynthetic membranes.
Another technical innovation that is receiving attention is the efficient recovery of landfill gas to achieve regulatory compliance with new air pollution control standards and to recover valuable energy.
The third area of technical advancement is the development of bioreactor landfills. This is when a landfill essentially is operated as a treatment facility and the natural decomposition process that occurs in a landfill is accelerated to reduce waste volume and to increase the amount of waste that can be placed into the landfill. Bioreactors are expected to reduce long-term emissions from the landfill into the groundwater or the atmosphere. Several bioreactor landfills currently are being operated on a limited basis in the United States. There also is significant interest in bioreactor landfills in Western Europe.
In the past decade, more attention has been placed on better management strategies to help operate larger landfills more profitably. The best facilities use the latest business practices, in addition to the latest technologies. For instance, GPS (Global Positioning Satellite) instrumentation, which can instantaneously record the location and compaction of waste, can help landfill operators run their facilities more efficiently.
In general, business strategies have focused on maximizing the amount of waste that can be placed within the permitted volume of the landfill. The strategies also are in-line with environmental objectives, so that regulatory issues do not interfere with the facility’s operation. After all, a landfill is an important asset in the public works infrastructure of a community.
Solid waste disposal in landfills is highly regulated. The federal government, through the Resource Conservation and Recovery Act (RCRA), specified that landfills must meet certain minimum standards. Initially, standards were developed for hazardous waste landfills, then a few years later, RCRA designated standards for municipal waste landfills.
In general, municipal waste landfills are required to have some type of liner at the base and a protective cover over the waste after a landfill site is closed. Landfill operations also must be extensively monitored. Additionally, the regulatory standards limit the amount of material that is allowed to be released into the groundwater and into the air. Subsequent lessons will describe these regulations in more detail.
Needless to say, landfill operations are highly regulated, and it is the facility owner’s responsibility to comply with the regulatory standards.
Changing Ownership Trend
The business climate associated with landfill operations has changed in recent years, concurrent with the increase in recycling programs and with the implementation of new regulations that have increased the capital costs associated with developing a landfill. Specifically, as smaller landfills have been consolidated into larger landfills, there has been a tendency for these landfills to be operated by private companies as opposed to municipal waste authorities. Private companies also have merged into larger private companies, which has led to further consolidations the industry.
Industry consolidation is expected to continue as smaller, private waste collection companies and landfill operators sell-out to larger companies.
Alternatives to Landfilling
Over the course of the next 30 years, as well as from 1970 until the present, other solid waste management practices will be implemented. These practices include recycling waste back into new products, composting waste and using byproduct materials as soil amendments, and incineration.
Yet as alternate solid waste handling processes are developed, it is very clear that a well-designed, -operated, and -managed landfill will remain important to local communities as they seek to better manage their solid waste.
Even recycling systems, for example, still have residues that must be landfilled. A recycling program that is operating properly can recover 20 to 40 percent of the municipal solid waste from a community, leaving 60 to 80 percent to be landfilled.
Composting municipal solid wastes generally converts 1/3 of the material into a usable product, leaving 1/3 of the material to be landfilled and 1/3 of the material to decompose. These proportions may be lower if the waste stream contains a higher-than-normal proportion of construction and demolition (C&D) waste.
Waste-to-energy systems (WTE) and incinerators generally create residue of between 10 and 20 percent that must be landfilled. Usually, incinerator ash also must be placed into a special waste landfill segregated from the normal municipal waste that would be taken to a sanitary landfill.
Landfill Development, Operation and Closure
The life of a landfill extends over many years and involves several phases:
Phase 1: Site Selection and Investigation. During this phase, sites for a proposed landfill are evaluated from a geotechnical standpoint, as well as from a variety of environmental factors. Concurrent with this evaluation is initiation of a public participation program, to openly communicate with the public and minimize potential landfill opposition.
Phase 2: Design and Regulatory Approval. Detailed plans and specifications are prepared, regulatory approvals and financial commitments are received, and construction is initiated.
Phase 3: Site Construction. This involves development of the support facilities, and the development of the landfill’s first one or two cells.
Phase 4: Operation. The landfill is opened and operated over a period of years. As cells are filled, additional cells are constructed. Essentially a landfill operation is a long-term construction project.
Phase 5: Site Closure. As the cells within the landfill are filled to capacity, that area is closed. The landfill then is monitored for a minimum of 30 years.
Phase 6: Long-Term Care. Regulatory standards require an owner to monitor the landfill for 30 years after closure. If environmental problems are detected, the owner is responsible for taking remedial action. During the long-term care period, the owner also is responsible for any facility maintenance.
When developing sanitary landfills, environmental protection is one of the most important issues. A properly designed and operated sanitary landfill can minimize impact on the environment, maintaining:
•Groundwater Quality. If the base of the landfill is not properly lined, the waste material in the landfill can escape into the groundwater. Regulatory standards provide that most landfills be constructed with a combination of low-permeability compacted soil and geomembranes. This provides a high degree of protection, but the soil and geomembranes must be carefully designed and installed.
•Wetlands and Streams Protection. Surface runoff from landfills can be detrimental to adjacent wetlands and streams. Both chemical and sediment contamination are a concern. With proper design and operation, both of these concerns essentially can be eliminated.
•Air Quality. Several mechanisms exist that can affect air quality at landfills. Odors from the waste are the most frequently cited air quality concern. Other considerations are gaseous emissions direct from the waste, and the release of methane gas from the decomposition process that takes place within the landfill. Additionally, there are concerns about blowing paper. And if the landfill should catch on fire — which seldom occurs — the situation can be difficult to manage and can result in significant local impacts on air quality.
Landfill gas is a combination of methane and carbon dioxide that, if trapped in an enclosed space, can result in an explosion. The danger results from landfill gas migrating underground into buildings. A number of these have occurred over the years, so management practices must be implemented to control the danger of explosive gases.
A growing concern regarding landfills is the emission of methane, a greenhouse gas. Landfills have been cited as a significant source of methane. Consequently, control mechanisms are being mandated at the national level.
As landfills have become larger in size, landfill heights have significantly increased. This has given rise to slope stability concerns. Higher and longer slopes can fail and cause catastrophic results.
This is an even more significant concern in areas where there is seismic activity. Some areas of the western United States, the East Coast and New York are subject to earthquake activity that can potentially cause slope failure at a large landfill.
Slope stability also is an issue at landfills that receive specialized waste. If these wastes contain significant amounts of water, the slope instability increases.
A landfill poses many potential hazards for workers. Materials brought to a landfill may be hazardous, and workers need to be protected from materials in the waste that may be sharp or infectious. Worker protection also should extend to limiting exposure to dust that may emanate from the waste, and to providing hearing protection when operating equipment.
Additionally, materials may spontaneously catch on fire or explode. This has not happened very often, but there have been cases where this has had devastating effects. An incinerator in Ohio that received a solvent material is one example.
To ensure safety, workers must be careful when they are walking on the site. Vehicle paths must be clearly marked to ensure that no one is in the way of moving equipment. Workers also should be protected against exposure to extreme weather, such as high summer temperatures and low winter temperatures. Finally, workers must be protected from construction accidents that can occur when assembling liners, working in trenches or working on other types of construction activities.
Developing a new landfill, or even expanding an existing landfill, can be a very sensitive issue for the community. Public concerns about landfills have caused enough controversy in some cases to prevent the development or the expansion of a site. Therefore, it is very important that public concerns be quickly addressed in an appropriate manner to preserve the opportunity to continue developing and/or operating a landfill site. Well-managed sites have established procedures by which they communicate frequently with the neighbors and other constituents who live in the site vicinity.
While the United States and Western Europe have implemented state-of-the-art landfill technologies that provide a high degree of environmental protection, this has not been the case in other parts of the world. In Eastern Europe, Africa and the Far East, there are many examples of very poorly operated waste disposal systems. In many countries, the municipal solid waste simply is dumped in locations that have a significant impact on the water resources environment. In large metropolitan areas in developing countries, for example, there have been major accidents that have resulted in a substantial loss of life. These accidents either have been a result of waste material landslides or explosions and fires that have occurred within the landfill.
In the developing countries and in Eastern Europe, there is a significant interest in developing better waste disposal practices to improve community development. The waste disposal practices that are being implemented generally focus on how to better handle the waste to provide a reasonable degree of protection for the environment. Nevertheless, they still do not provide the same level of protection that is associated with landfills in the United States, Europe, Japan and Australia.
Generally, the priorities for developing better land disposal facilities in developing countries is to limit the amount of hazardous material entering the facility, to stop burning waste in the facility and to provide protection to surface and groundwater resources. This may or may not include the installation of a liner under the waste disposal facility.
Philip O’Leary and Patrick Walsh are professors with the Solid and Hazardous Waste Center at the University of Wisconsin-Madison.