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).
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.