Technical Basis for Also Using Health-Risk Assessment to Establish Contaminant Boundaries for Corrective Action Units (CAUs) of the Underground Test Area (UGTA) at the Nevada Test Site (NTS)

Daniels, J I ; Tompson, A F

Lawrence Livermore National Laboratory

关键词: 63 Radiation, Thermal, And Other Environmental Pollutant Effects On Living Organisms And Biological Materials;    Drinking Water;    99 General And Miscellaneous//Mathematics, Computing, And Information Science;    Us Epa;    Public Health;   

DOI  :  10.2172/15008030
RP-ID  :  UCRL-TR-201702
RP-ID  :  W-7405-ENG-48
RP-ID  :  15008030

美国|英语

来源: UNT Digital Library

【 摘 要 】

This technical basis document serves two purposes. First, it provides a detailed discussion of the rationale and procedures suitable for deriving a risk-based contaminant boundary that will protect public health unambiguously, along with examples that are intended as illustrative only to facilitate understanding. Second, it explains the benefits of using such information as the framework for fostering risk communication to educate, inform, and enlighten, and importantly, to fully disclose the goals and structure of contaminant boundaries. To determine a contaminant boundary within a CAU, standards or criteria must be adopted that establish whether groundwater is safe or unsafe for public (and worker) use. For purposes of this discussion, drinking water consumption is considered the pathway of exposure. However, in practice, a realistic land-use scenario must be described and agreed upon before a prospective, realistic risk-based calculation is performed. Otherwise, it will not be clear whether consumption of drinking water is a even appropriate. For example, the future land use that is defined may not even permit access to the contaminated water (e.g., denial of use by law and stewardship; or a lack of accessibility), and in that situation there would be no exposure and no potential health consequences. Taking into consideration that consumption of the groundwater is feasible, the groundwater is deemed unsafe if it contains radionuclide contamination that exceeds the criteria that the United States Environmental Protection Agency (EPA) considers in establishing regulatory standards for drinking water contaminants, including radionuclides generally (i.e., a target range for lifetime excess-cancer risk that is not to exceed 10{sup -4} [1/10,000] and ideally is less than 10{sup -6} [1/1,000,000]) (see EPA, 2000a). Thus, the maximum contaminant levels (MCLs) for substances in drinking water are considered to be health-protective and generally are derived on the basis of acceptable level of risk. Revision 1 to Appendix VI, Section 3 of the Federal Facility Agreement and Consent Order (FFACO, 1996; as amended) even stipulates that the contaminant boundary for a CAU is to be determined by modeling groundwater flow and radionuclide transport over the next 1,000 y, with uncertainty considered. Such modeling will identify over the entire 1,000-y period the spatial extent of radionuclide-contaminated groundwater, created by nuclear tests, that is above background conditions and exceeds the National Primary Drinking Water Regulations (NPDWRs) for radionuclides. These NPDWRs were developed as a requirement of the Safe Drinking Water Act (SDWA) and have been referred to as SDWA standards or as MCLs for radionuclides.