Classification and Disposal of Hazardous Chemical Waste

The system for classification and disposal of hazardous chemical waste developed by EPA under RCRA does not apply to all wastes that contain hazardous chemicals. For example, wastes that contain dioxins, polychlorinated biphenyls (PCBs), or asbestos are regulated under the Toxic Substances Control Act (TSCA). In addition, the current definition of hazardous waste in 40 CFR Part 261 specifically excludes many wastes that contain hazardous chemicals from regulation under RCRA, including certain wastes produced by extraction, beneficiation, and processing of various ores and minerals or exploration, development, and use of energy resources. Thus, the waste classification system is not comprehensive, because many potentially important wastes that contain hazardous chemicals are excluded, and it is not based primarily on considerations of risks posed by wastes, because the exclusions are based on the source of the waste rather than the potential risk. 

Wastes have been classified for decades for a variety of purposes. This Section discusses the historical development of classification systems for radioactive and hazardous chemical wastes and the resulting classification systems in use at the present time. The relationship between waste classification and requirements for disposal of different classes of hazardous waste is emphasized. The framework for this discussion is the top-level system for waste classification in the United States shown in Figure 4.1. Within this framework, it is first determined whether a waste is nonhazardous (e.g., municipal waste) these wastes are not addressed in this Report. If a waste is deemed hazardous, it is so classified due to the presence of radionuclides or hazardous chemicals. Mixed radioactive and hazardous chemical waste is not a separate class of waste. However, mixed waste has been an important concern as a result of differences in requirements for management and disposal of radioactive and hazardous chemical wastes. Section 4.1 addresses classification and disposal of radioactive waste, and is followed by discussions of classification and disposal of hazardous chemical waste in Section 4.2 and approaches to management of mixed radioactive and hazardous chemical waste in Section 4.3. Finally, Section 4.4 summarizes previous NCRP recommendations relevant to waste classification. 

Classification and disposal of hazardous chemical waste is based mainly on EPA regulations and guidance developed under RCRA,... 

The similarities are of the following kinds. First, neither classification system includes a general class of exempt waste. Second, neither classification system is comprehensive, because the classification system for radioactive waste distinguishes between fuel-cycle and NARM waste and the classification system for hazardous chemical waste excludes many potentially important wastes that contain hazardous chemicals. Third, any waste must be managed and disposed of in a manner that is expected to protect public health and the environment. In addition, the approach to disposal of hazardous chemical waste under RCRA, which emphasizes monitoring of releases from disposal facilities and an intention to maintain institutional control over disposal sites for as long as the waste remains hazardous, is applied to disposal of uranium or thorium mill tailings under AEA. 

Unfortunately, however, it is difficult for anyone to fully comprehend the existing classification systems for radioactive and hazardous chemical wastes. These systems are not based on clearly stated principles from which a logical and transparent classification system might follow, and the two systems approach classification and disposal of hazardous waste in different ways. The systems intermix legal and technical considerations in ways that sometimes defy logic. A few examples of the incongruities in the waste classification systems that result in a lack of transparency and difficulties in comprehension are described below. 

There also are two important differences. First, the classification system for radioactive waste from the nuclear fuel cycle includes different classes that are defined based essentially on the source of the waste. In addition, some classes of fuel-cycle waste (e.g., high-level waste) often, but not always, contain higher concentrations of radionuclides than other classes (e.g., low-level waste) and, thus, pose a greater hazard in waste management and disposal. The classification system for hazardous chemical waste does not distinguish between hazardous wastes based on their source, with the exception of the K list of wastes from specific sources. Additionally, hazardous chemical wastes are not further classified based on their relative hazard (i.e., there is only one class of hazardous chemical waste). 

NCRP s recommendations on classification of hazardous wastes are intended to address deficiencies and inconsistencies in the separate systems for classification and disposal of radioactive and hazardous chemical wastes in the United States summarized previously. The most important of these include ... 

The states of Washington and California have considered a classification of hazardous chemical waste based on risk and have developed a category of extremely hazardous waste (California, 1999 Mehlhaff et al., 1979 NAS/NRC, 1999b). However, the requirements for treatment and disposal of extremely hazardous waste differ little from those applied to other hazardous waste. Thus, the designation of a class of extremely hazardous waste based on relative hazard has had little effect on waste management and disposal. 

Under current EPA regulations, a chemical waste is either hazardous or it is not, and there is no further classification of hazardous chemical waste with respect to the degree of hazard. Some states have defined classes of hazardous chemical waste (e.g., extremely hazardous waste) but, in practice, the requirements on management and disposal of all hazardous wastes have resulted in essentially the same approaches being used regardless of hazard. When a hazardous chemical waste is mixed with a nonhazardous solid waste, the entire waste is classified as hazardous unless the former is a characteristically hazardous waste that does not contain any listed waste and mixing with the nonhazardous waste removes the hazardous characteristic. 

A risk-based waste classification system would be established by focusing on risks that arise from disposal of hazardous wastes. Thus, the amounts of hazardous chemical wastes that would be acceptable for near-surface disposal over the longer term would need to be evaluated. While NCRP believes that many hazardous chemical wastes would continue to be acceptable for near-surface disposal, it should be anticipated that this will not be the case for some wastes that contain high concentrations of heavy metals e.g., see Okrent and Xing (1993). As a result, some hazardous chemical wastes could be classified as high-hazard (see next section), and such a classification also could also mean that perpetual institutional control will be required at some existing burial sites. 

Over the last several decades, separate classification systems have been developed for radioactive and hazardous chemical wastes based on a variety of considerations, the most prevalent being the source of the waste. These classification systems have served their intended purpose of facilitating development of health-protective strategies for waste management and disposal reasonably well. However, they have exhibited a number of shortcomings and undesirable ramifications, which indicate that a new approach to classification of hazardous wastes would be beneficial. 

The primary purpose of this Report is to present NCRP s recommendations on classification of hazardous wastes. The Report is directed at a multidisciplinary audience with different levels of technical understanding in the fields of radiation and chemical risk assessment and radioactive and chemical waste management. Anew hazardous waste classification system is proposed that differs from the existing classification systems for radioactive and hazardous chemical wastes in two fundamental respects. First, hazardous waste would be classified based on considerations of health risks to the public that arise from disposal of waste. Hazardous waste would not be classified based, for example, on its source. Second, the classification system would apply to any hazardous waste, and separate classification systems for radioactive and hazardous chemical wastes would not be retained. In the proposed system, waste would be classified based only on its properties, and the same rules would apply in classifying all hazardous wastes. 

This Section summarizes the separate classification systems that have been developed for radioactive and hazardous chemical wastes. Impacts of the two classification systems on management and disposal of mixed wastes are also described. 

Management and disposal of many wastes that contain hazardous chemicals are regulated by the U.S. Environmental Protection Agency (EPA) under authority of the Resource Conservation and Recovery Act (RCRA). In the classification system for hazardous chemical wastes specified in 40 CFR Part 261, waste is classified as hazardous by its characteristics or by listing. 

The existing classification systems for radioactive and hazardous chemical wastes in the United States and approaches to disposal of... 

The term mixed waste refers mainly to waste that contains radionuclides regulated under AEA and hazardous chemical waste regulated under RCRA. Dual regulation of mixed waste has no effect on classification, management, and disposal of the hazardous chemical component or on classification of the radioactive component. The effects of dual regulation of mixed waste on management and disposal of the radioactive component are summarized as follows ... 

Classification systems for radioactive waste and requirements for disposal of different classes of radioactive waste have been developed largely independently of classification systems and disposal requirements for hazardous chemical waste. This Section has discussed the classification systems for radioactive and hazardous chemical wastes and the relationships between waste classification and requirements for disposal. Impacts of the different systems for waste classification and disposal on management and disposal of waste that contains... 

Some existing waste classification systems are quantitative. For example, the concentrations of radionuclides defining the different subclasses of low-level radioactive waste that is generally acceptable for near-surface disposal are clearly stated in the regulations (NRC, 1982a), as are the quantitative conditions defining ignitable, corrosive, reactive, and toxic hazardous chemical wastes (see Section 4.2.1.1). 

The proposed framework for risk-based classification of all radioactive and hazardous chemical wastes developed in Section 6.2.2 represents waste classification in its broadest, most general terms. Thus, this classification system can be viewed as the highest level of a possible hierarchy of hazardous waste classifications (e.g., see Figure 4.2). Further subclassification of these broadly defined waste classes may be desirable for such purposes as protection of workers during waste operations, protection of public health and the environment following waste disposal, and development of efficient methods of waste management taking into account the characteristics of actual wastes. 

The provision of the National Energy Policy Act (NEPA, 1992) that prohibits NRC from establishing dose criteria that could be used to exempt radioactive wastes from licensing requirements for disposal clearly is an impediment to development of generally applicable exemption levels for radioactive waste. An exempt class of radioactive and hazardous chemical waste is the cornerstone of the risk-based waste classification system developed in this Report, and any legal and regulatory impediments to establishment of generally applicable exemption levels would need to be removed. 

---