Today, the brownfield site of Herr’s Island in Pennsylvania has been renamed Washington’s Landing and is home to a marina, office buildings, and an exclusive townhouse development. In order to achieve this transformation, the soil contaminated with hazardous waste was encapsulated with an impermeable barrier and buried under tennis courts. Even as communities around the world push toward a zero waste future, we are still going to need a safe way to dispose of waste that cannot be reused, recycled, or composted. This includes municipal waste, hazardous waste, and nuclear waste.

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The most common and often most economical choice for municipal solid waste disposal is the sanitary landfill, which consists of a lined pit constructed and managed in ways to minimize environmental impacts (Figure 12.25). A bottom liner provides a barrier between the waste in the landfill and soils and groundwater. In the modern landfill, this liner is made of thick, tough plastic placed over a layer of packed clay, which acts as an additional barrier between the waste and local soil and groundwater. Immediately above the liner is a layer of porous gravel or sand, through which water that has seeped down through the waste in the landfill passes easily until it reaches the plastic landfill liner. This seepage, called leachate, flows along the top of the liner to a low point called a sump, where leachate can be pumped out and treated. Because leachate may contain many hazardous substances, groundwater in the vicinity of the landfill should be tested on a regular basis, to ensure that the bottom liner has maintained its structural integrity and is not contaminating local water supplies.

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Once the basic structure of the landfill is in place, filling it becomes a relatively simple task. Garbage trucks unload their contents into an open part of the landfill, where bulldozers compress and spread the material as much as possible. At the end of each day, a layer of soil is placed over the day’s trash collection, which prevents the wind from blowing lighter materials away and protects it from scavenging birds and other animals. The layers of soil also help to dampen unpleasant odors emanating from the waste. Daily additions to the landfill continue until the pit reaches its capacity. At that point, the landfill is capped, usually with successive layers of clay, subsoil, and topsoil, which will be planted with vegetation chosen to reduce erosion.

Even after sanitary landfills are filled and capped with layers of clay and soil, they are not waterproof. Rainwater and water from melting snow can continue to percolate through the soil and through the buried waste, emerging as leachate, which will need to be collected and treated.

The RCRA requires that hazardous wastes be treated before disposal to reduce the danger they pose to the environment. Predisposal treatments involve a variety of physical, chemical, or biological processes to reduce the threat hazardous wastes pose to the environment.

Burning, or incinerating, some types of hazardous waste can reduce the dangers of certain kinds of waste and cuts back on its volume. For example, burning medical wastes will kill any biological pathogens that may be contaminating the waste. Also, the toxicity of some chemical wastes can be reduced by incineration at very high temperatures, up to 1,200°C (2,200°F). As in the case of MSW, however, the by-product of incineration, ash, will require testing and disposal.

Landfills intended for disposal of hazardous wastes must be secure and therefore must meet much stricter design and management standards than municipal landfills. Under RCRA, the EPA requires a double liner for hazardous waste landfills and a double leachate collection and removal system (Figure 12.26a). Such landfills must also include a leak detection system and ways to prevent the run on and runoff of storm water. Once a hazardous waste landfill is filled and covered, removal of leachate must continue until it is no longer produced. Ongoing monitoring for leaks and for groundwater contamination is also required. Approximately 10% of hazardous waste disposed in the United States is stored in secure landfills. RCRA prohibits the storage of liquid hazardous wastes in landfills.

Natural or excavated depressions can be used as surface impoundments for temporarily storing or treating liquid hazardous wastes (Figure 12.26b). These structures must have double liners, a system for collecting and removing leachate, and a leak detection system. They must be regularly monitored, inspected, and eventually sealed.

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Of the liquid hazardous waste disposed of in the United States, approximately 90% is injected into wells drilled into deep rock formations (Figure 12.26c). Deep well injection is regulated by RCRA and the Safe Drinking Water Act of 1974. The average depth of deep injection wells is 1,200 meters (4,000 feet), far below the level of groundwater supplies. The EPA requires that deep injection wells be located in areas with stable geology and without fractures that might allow injected waste to migrate upward and contaminate drinking water supplies. The drilling and casing of deep injection wells also include multiple safety features to minimize the chance of groundwater contamination.

Nuclear reactors around the world continue to produce waste, yet the problem of waste disposal remains unresolved. Several countries at the forefront of nuclear energy technology favor deep geological storage of intermediate- and high-level nuclear waste. Despite the consensus among these nations, there is only one deep geological disposal site that is currently licensed and operating, the Waste Isolation Pilot Plant (WIPP) located in the United States near Carlsbad, New Mexico.

The WIPP facility, which stores defense-related, intermediate-level nuclear waste in thick salt deposits, has been in operation since 1999. However, given the uncertainty associated with the Yucca Mountain nuclear repository (see page 372), the United States is without a permanent disposal site for high-level nuclear wastes generated by civilian power plants.

While the United States continues its search for alternatives to Yucca Mountain, Finland and Sweden are going forward with the development of deep geological disposal in bedrock. Disposal at a site on an island in southwest Finland is planned to begin in 2020. A different type of geology is being developed for nuclear waste disposal in France, a deep clay formation east of Paris, which geologists estimate has been stable for millions of years. The French repository is planned for opening in 2025. However, the incident at Fukushima in Japan (see Chapter 9, page 283) reminds us that much can happen to influence such plans.

In the aftermath of that accident, Germany decided to eliminate plans for developing nuclear power and to phase out its existing reactors. While such phase-outs, if they occur, will not eliminate the need for nuclear waste disposal, they will reduce the long-term need for disposal space. In the meantime, as geologists, politicians, lawyers, judges, and environmental activists debate and study the issue, the amount of radioactive waste in “temporary” storage continues to accumulate, like all those shells that Native Americans piled up near Oakland, California.