Classification of existing wastes

Second, waste that contains hazardous substances is classified based on considerations of health risks to the public that arise from waste disposal. The existing classification systems for radioactive and chemical wastes in the United States are not based primarily on considerations of health risks to the public. Rather, classification of hazardous wastes has been based primarily on the source of the waste or the presence of particular hazardous substances. The absence of risk-based waste classifications has had a number of undesirable ramifications ... 

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 Report is concerned with classification of hazardous waste for purposes of disposal. However, the principles and concepts embodied in the waste classification system could be applied in classifying hazardous materials for any other purpose. The classification system is intended to be applied to hazardous waste prior to disposal. It is not intended to be applied to screening or ranking of contaminated sites, including existing hazardous waste disposal sites, because these activities involve site-specific considerations that cannot be included in a generally applicable waste classification system. However, any wastes exhumed from contaminated sites that then require disposal would be included in the waste classification system. 

The recommended risk-based waste classification system has important implications in three areas (1) the resulting classification of existing radioactive and hazardous chemical wastes, (2) subclassification of the basic waste classes, and (3) changes in existing laws and regulations that would be required to implement such a classification system. 

Significant portions of existing waste classification systems are not based on the primary objective of ensuring that the risk that arises from waste disposal is acceptable. 

DOE s high-level wastes as if they were among the most hazardous of all radioactive wastes. However, the concentrations of hazardous substances in some of these wastes are similar to those in low-level radioactive waste that is normally intended for disposal in near-surface facilities. In contrast, some chemical wastes that are highly hazardous, compared with other wastes, and nondegradable are being sent to near-surface disposal facilities. Both of these situations occur largely because of the source-based aspects of existing waste classification systems. 

Waste classification systems are not transparent or defensible. There exist numerous classification systems for different wastes having a variety of bases and implementation rules that are not tied to any consistent set of principles. As a consequence, the overall classification of hazardous waste is not transparent to... 

There is sufficient information available to allow NCRP to anticipate the classification of a number of existing wastes that would... 

As indicated by the current subclassifications of existing waste classes summarized above, a variety of waste properties could be used to develop meaningful subclassifications of broadly defined waste classes. These properties include, for example, waste volumes, levels of decay heat and external radiation, and the long-term persistence of the hazard posed by waste constituents. Subclassifications of waste classes also could be based on the presence of particular hazardous substances. However, if the broadly defined waste classes are based on risk, as in the classification system proposed in this Report, the intrinsic toxicity of hazardous substances normally would not provide a basis for subclassification, because this property already is accounted for in determining the basic classification of any waste. Examples of possible approaches to subclassifying the basic waste classes are discussed in the following paragraphs. 

The existing classification system for radioactive waste in the United States is depicted in Figure 1.1. This classification system is in the form of a hierarchy of basic waste classifications and waste subclassifications. 

As part of this study, proposed radioactive waste classification systems that differ from the existing classification system in the United States were reviewed and evaluated. Of particular interest is the classification system currently recommended by the International Atomic Energy Agency (IAEA). This classification system and the disposal options for each waste class are summarized in Table 1.2. The basic waste classification system consists of exempt waste, low-and intermediate-level waste, and high-level waste. 

NCRP undertook a study of waste classification because of the importance and visibility of hazardous waste management in the United States coupled with the observation that the existing classification systems for hazardous wastes are increasingly complex and inefficient. This determination led to the independently conceived alternative approach to hazardous waste classification described in this Report. 

The existing waste classification systems are becoming increasingly complex as additional waste streams are incorporated into a patchwork system that is not based on a consistent set of principles. Some wastes are classified based on their source (i.e., the nature of the process or facility that produces them), some based on their composition, and some based on their physico-chemical characteristics. 

The principles of waste classification presented in this Report do not address a framework for subclassification of hazardous wastes. However, the relationship of existing subclassifications to the proposed framework is discussed. 

Section 4 presents detailed information on existing classification systems for radioactive and hazardous chemical wastes, the relationships between waste classification and requirements for waste disposal, and the impacts of waste classification systems on management and disposal of mixed wastes. This Section also summarizes previous NCRP recommendations relevant to waste classification. 

Section 7 then addresses the implications of the recommended risk-based waste classification system. By assuming key parameters (e.g., values of acceptable risk, characteristics of exposure scenarios) and applying the system to a variety of example waste streams, the question of how existing wastes would be classified in the new system is investigated. This Section also summarizes the legal and regulatory ramifications of the proposed hazardous waste classification system. 

The discussions of classification of radioactive and hazardous chemical wastes and management of mixed waste in Sections 4.1 to 4.3 are presented in considerable detail to facilitate understanding of these issues by readers who may not be knowledgeable in these areas. The existing hazardous waste classification systems and the historical developments underlying them are complex. NCRP believes that an appreciation of these complexities is important in gaining an understanding of the need for a new hazardous waste classification system and the benefits it would provide. 

Previous sections have presented technical and historical information on radiation and chemical risk assessment and on classification of radioactive and hazardous chemical wastes. This information provides important perspectives for establishing the foundations of a new hazardous waste classification system. Before establishing these foundations, it is useful to specify the attributes that an ideal waste classification system should possess. The following sections identify the desirable attributes of a waste classification system including that the system should be risk-based, it should allow for exemption of waste, and it should be comprehensive, consistent, intrinsic, comprehensible, quantitative, compatible with existing systems, and flexible. These attributes should be recognized as goals that are not all likely to be fully realized in a practical waste classification system. 

---