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Surprisingly, the cleanup of a severely polluted site, such as Love Canal (see Chapter 12), fell outside any existing legislative authority at the time, including the Resources Conservation and Recovery Act, which is focused on current and future management of hazardous wastes. Authority to address historical contamination required additional legislation. As we saw in Chapter 12, the U.S. Congress passed the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), or Superfund Law, in 1980. The first goal of the Superfund program is to identify sites where contamination of air, soil, and water by hazardous substances has been sufficient to threaten human health or harm the environment. Sites sufficiently contaminated are placed on a “National Priorities List,” which in 2011 included more than 1,350 sites in the United States. Once these sites are identified, the second objective of the program is to reduce threats to human health and the environment, generally by cleaning the site of hazardous substances. The third goal is to discover those responsible for the contamination and seek payment for site cleanup.

This groundbreaking piece of legislation gave the EPA the authority to assign responsibility for a contaminated site and demand financial assistance in its remediation. This law was the beginning of efforts all over the country to clean up toxic waste sites. In the case of the Love Canal, Occidental Petroleum, which owned the Hooker Chemical company, agreed to pay $129 million in restitution. The most toxic area was dug up and reburied with a plastic liner and the neighborhood’s empty streets were enclosed by a chain link fence to prevent entry.

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The Superfund Act has also led to the cleanup of many other toxic sites around the country. In 2002 the EPA and General Electric signed an agreement to begin removing PCBs from a 64-kilometer (40-mile) section of the upper Hudson River (Figure 13.38). The first steps in the process involved sampling the length of the river to identify the locations of the most contaminated sediments, building the processing and transportation facilities, and developing detailed plans for the massive project. During the early stages of the work, public concerns were identified and they influenced the way the project was carried out. For example, barges and trains were used to transport dredged sediments out of the Hudson River Valley to address concerns over increased traffic congestion on highways. Also, in response to fears of future contamination, all parties agreed to store toxic sediments outside of the Hudson River Valley in approved hazardous waste repositories.

The plan for dredging was divided into two phases. Phase 1 would involve one season (May to November) of dredging followed by a year spent evaluating the results of the dredging operations. The evaluations, peer-reviewed by independent experts, would be used to determine whether dredging had removed PCBs. Reviewers would also assess whether the dredging had mobilized unacceptable amounts of PCBs into the river ecosystem, which was a serious concern raised by the public and by environmental scientists. Based on the findings, adjustments in techniques could be made to improve the cleanup process. If the results of Phase 1 were acceptable, the project would move into Phase 2, which would involve dredging the remainder of the site.

Phase 1, completed in 2009, resulted in the removal of approximately 215,000 cubic meters (283,000 cubic yards) of PCB-contaminated sediments from a 9.7-kilometer (6-mile) section of river near Fort Edward on the upper Hudson. While the amount of material removed from the river was enormous, the operation was done with precision, with the location and depth of dredging guided by a satellite navigation system. The work employed over 500 people and dredging went on 24 hours a day, 6 days a week, with up to 12 dredging crews working simultaneously (Figure 13.39). The dredged material, which filled 626 hopper barges measuring 59.5 meters by 10.7 meters (195 feet by 35 feet), was transported by rail to a disposal site in Texas. To reduce the possibility of releasing any residual PCBs, the dredged areas were later covered, or “capped,” with 150,000 tons of clean fill material. During dredging operations, the river was continuously monitored to assure that PCB concentrations did not exceed the 500 parts per trillion safe limit specified by the U.S. Safe Drinking Water Act.

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Based on independent expert review of the process and results of Phase 1 in 2010, along with comments from the public, the EPA went forward with plans for Phase 2. Planners project that Phase 2 will remove an additional 1.8 million cubic meters (2.4 million cubic yards) of contaminated sediments. Phase 2, scheduled for completion in the fall of 2015 at an estimated cost of approximately $750 million, will be followed by another phase involving habitat restoration along the shoreline and in dredged areas, as well as data collection to evaluate the success of the project.

Rather than cleaning up a polluted site by moving massive amounts of contaminated soil or sediment to a hazardous waste facility, environmental scientists can use organisms to decontaminate soils, sediments, and groundwater aquifers. This approach to pollution cleanup, called bioremediation, can save physical work and money.

When the bioremediation process involves plants, it is called phytoremediation (Figure 13.40). Scientists have identified hundreds of hyperaccumulator plants that accumulate heavy metals in their tissue. Consider that excavating 30 centimeters (1 foot) of soil contaminated with lead from 4 hectares (10 acres) would require removing 18,200 metric tons (20,000 tons) of soil. By contrast, using plants to extract the same amount of lead from the soil would require safely disposing of just 455 metric tons of plant biomass, or 1/40th the amount of soil that would otherwise have been removed. In addition, the monetary costs would be a small fraction of what it would cost to excavate, transport, and store more than 18,000 metric tons of contaminated soils.

In places where groundwater has been contaminated with solvents, gasoline, and other organic compounds, bioremediation has been used to decontaminate aquifers. Many organic chemicals that were once believed to be resistant to breakdown by microbes can be metabolized by some component of a microbial community. Sometimes they need to be coaxed to multiply and do their work by adding nutrients, reducing or increasing oxygen availability, or adding particular energy sources (e.g., sugar) to the aquifer (Figure 13.41). Using such techniques, environmental scientists have successfully decontaminated polluted aquifers in situations previously considered physically or economically impossible.