Framework for Waste Classification

The basic element of the recommended framework for a comprehensive and risk-based waste classification system is the assumption that any waste that contains sufficiently small amounts of radionuclides or hazardous chemicals should be classified as exempt, or essentially nonhazardous. Waste that contains greater amounts of hazardous substances then would be classified as nonexempt, and further classification of nonexempt wastes, based also on the amounts of hazardous substances present, would be appropriate. 

Limits on amounts of hazardous substances in each waste class would be calculated based on values of the so-called risk index for each hazardous substance in the waste and the composite risk index for mixtures of hazardous substances. For the purpose of describing the recommended framework for a risk-based hazardous waste classification system, the risk index is generally defined as  

The modifying factor in the risk index represents any considerations of importance to waste classification other than those that are directly incorporated in the calculated risk from disposal and the specified allowable risk. The modifying factor can take into account, for example, the probability of occurrence of assumed exposure scenarios used in classifying waste, uncertainties in the assessment of risk from disposal and in the data required to evaluate the risk index, levels of naturally occurring hazardous substances in surface soil and their associated health risks to the public, and the costs and benefits of different means of waste disposal. The modifying factor is discussed further in Section 6.3.3. 

1 Exempt Waste. The class of exempt waste embodies the concept that there are amounts of hazardous substances in waste which are so low that the associated risks to the public for any method of disposal generally would not be of concern. Thus, if waste that contains radionuclides were classified as exempt, the waste could be disposed of as if it were nonradioactive, and similarly for waste that contains hazardous chemicals or mixtures of the two. Further, mixed wastes that contain exempt amounts of radionuclides could be managed based on their hazardous chemical content, and vice versa. 

NCRP believes that different classes of waste should be defined in relation to general types of disposal systems that presently exist or are likely to be developed in the future. In accordance with current waste disposal practices, the exempt class of waste (essentially non-hazardous) thus is defined as any waste containing sufficiently small amounts of hazardous substances that the waste would be generally acceptable for disposal in a municipal/industrial landfill (or equivalent) for nonhazardous materials. This type of disposal facility is regulated under Subtitle D of RCRA (1976). 

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Process of Implementing the Waste Classification System. Taken together, the framework for waste classification discussed in Section 6.2 and the risk index developed in Section 6.3 and this Section constitute the foundations of a comprehensive and risk-based hazardous waste classification system. Such a waste classification system could be established by regulatory authorities using the following general process ... 

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