Near-surface facilities

Low-hazard waste any nonexempt waste that is generally acceptable for disposal in a dedicated near-surface facility for hazardous wastes. 

Most low-level waste, except high-activity, longer-lived waste that is anticipated to be produced in small volumes, is intended for disposal in a near-surface facility. The acceptability of near-surface disposal for most low-level waste is based primarily on assessments of the long-term performance of such facilities, which indicate that the health risks to the public, including future inadvertent intruders, should be acceptable. 

All wastes classified as hazardous under RCRA, including properly treated toxic waste that is still considered hazardous, are intended for disposal in near-surface facilities regulated under Subtitle C of RCRA. EPA has developed detailed technical requirements on waste treatment and the siting, design, operation, and closure of disposal facilities. Thus, when viewed in relation to intended disposal technologies, there is basically only one class of hazardous chemical waste, regardless of the amounts of hazardous substances present i.e., a waste either is hazardous or it is not. 

Second, generic and site-specific assessments of near-surface disposal facilities for radioactive waste have shown that allowable doses to hypothetical inadvertent intruders usually are more restrictive in determining acceptable disposals than allowable doses to individuals beyond the boundary of the disposal site. This conclusion is based on predictions that concentrations of radionuclides in the environment (e.g., ground-water) at locations beyond the site boundary usually should be far less than the concentrations at the disposal site to which an inadvertent intruder could be exposed, owing to such factors as the limited solubility of some radionuclides, the partitioning of radionuclides between liquid and solid phases, and the dilution in transport of radionuclides in water or air beyond the site boundary. More people are likely to be exposed beyond the site boundary than on the disposal site, but acceptable disposals of radioactive waste in near-surface facilities have been based on assessments of dose to individuals, rather than populations. 

High-hazard waste Any nonexempt waste that generally requires disposal system more isolating than dedicated near-surface facility for hazardous wastes1 Concentrations of any hazardous substances that exceed limits for low-hazard waste... 

Low-Hazard Waste. Waste classified as low-hazard would be generally acceptable for disposal in a dedicated near-surface facility for hazardous wastes. Limits on concentrations of hazardous substances in low-hazard waste would be derived based on an assumption that the risk or dose to a hypothetical inadvertent intruder at a disposal site should not exceed acceptable (barely tolerable) levels. 

Most radioactive waste currently classified as low-level waste and most hazardous chemical waste would be classified as low-hazard waste, based on the expectation that these wastes would be generally acceptable for disposal in dedicated near-surface facilities for hazardous wastes. A possible exception is hazardous chemical waste that contains relatively high concentrations of heavy metals, which could be classified as high-hazard waste. 

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. 

Inadvertent human intrusion into hazardous waste. Inadvertent human intrusion is relevant to disposal of virtually all hazardous substances, especially in near-surface facilities. Typical scenarios assume that an unknowing individual (1) digs or drills into the waste and brings some of it to the surface where it is then available for dispersal and uptake, or (2) lives on the disposal site after waste has been exhumed or the cover removed, and consumes contaminated plant and animal products. Scenarios for inadvertent intrusion usually are assumed to occur after some period of active institutional control over the disposal site, which is typically 100 to 300 y. Intrusion scenarios are not very sensitive to site-specific parameters because the nature of intrusion (by digging or drilling) effectively bypasses the site-specific protection features, such as small amounts of groundwater,... 

Under current law and regulations, particular disposal systems generally are not required for any waste class, but only certain systems are authorized in law. Disposal systems other than those listed, such as greater confinement disposal at depths intermediate between a near-surface facility and a geologic repository, may be used for some wastes. 

These considerations lead to an important conclusion regarding the relationship between classification of fuel-cycle wastes and requirements for their disposal—namely, that the selection of acceptable systems for disposal of fuel-cycle wastes does not depend on the definitions of waste classes. Rather, the types of disposal systems that are expected to provide adequate protection of public health (e.g., a near-surface facility or a geologic repository) are selected based on the radiological properties of waste, essentially without regard for how the waste is classified. Thus, general requirements for disposal are not affected by the qualitative, source-based, and ambiguous definitions in the classification system for fuel-cycle waste. 

Intermediate-level waste is waste with high concentrations of intermediate-level, short-lived waste or intermediate-level, long-lived waste (IAEA, 1981). Such waste would be suitable for disposal in a near-surface facility incorporating engineered barriers and would include higher-activity Class-B and Class-C waste, as defined in NRC s 10 CFR Part 61 (NRC, 1982a). 

This proposal differs from the others discussed previously in that the first three waste classes all would include waste that is generally acceptable for disposal in a near-surface facility. However, these three classes differ in the extent to which engineered barriers would be relied upon to inhibit migration of radionuclides and exposures of inadvertent intruders. 

Essentially all solidified hazardous chemical waste is intended for disposal in near-surface facilities, with prescribed actions to prevent unacceptable releases of hazardous material (e.g., leachate collection and treatment). However, these facilities have been developed and operated essentially without consideration of the potential long-term risks posed by the waste in the absence of active monitoring and maintenance, including potential risks to future inadvertent intruders, or the requirements on site closure and release from institutional control that would ensure long-term protection of public health and the environment. 

Another desirable attribute of a waste classification system that is a corollary of the system being risk-based is that it treat wastes that pose similar health risks consistently. A chemically hazardous waste estimated to pose a certain risk should be in the same waste class as a radioactive waste that poses an equivalent risk, and similarly for mixed waste. Consistency also implies that wastes posing similar risks could be disposed of using essentially the same technology (municipal/industrial landfill, licensed near-surface facility for hazardous waste, or geologic repository). 

DOE intends to dispose of its mixed defense transuranic waste at WIPP. This facility is located hundreds of meters underground in a bedded salt formation, which clearly is much more isolating and protective than the near-surface facilities in which most RCRA hazardous waste is currently emplaced. Nonetheless, the... 

The basic framework for the waste classification system developed in this Report is depicted in Figure 6.1. Starting with the objectives that the classification system should apply to any waste that contains radionuclides or hazardous chemicals and that all such waste should be classified based on risks to the public posed by its hazardous constituents, the fundamental principle of the proposed system is that hazardous waste should be classified in relation to disposal systems (technologies) that are expected to be generally acceptable in protecting public health. This principle leads to the definitions of three classes of waste, and to quantification of the boundaries of the different waste classes based on considerations of risks that arise from different methods of disposal. The boundaries normally would be specified in terms of limits on concentrations of hazardous substances. At the present time, nearly all hazardous and nonhazardous wastes are intended for disposal in a near-surface facility or a geologic repository, and these are the two types of disposal systems assumed in classifying waste. The three waste classes and their relationship to acceptable disposal systems are described in more detail in Section 6.2. 

Given the assumed types of disposal systems (near-surface facilities or geologic repositories), waste would be classified as exempt, low-hazard, or high-hazard based on the magnitude of its risk index,... 

Low-hazard waste. NCRP recommends that low-hazard waste be defined as any nonexempt waste that is generally acceptable for disposal in a dedicated near-surface facility for hazardous wastes. Examples of such facilities include licensed or permitted for disposal of low-level radioactive waste under AEA (1954) or disposal of hazardous chemical waste under Subtitle C of RCRA (1976). 

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