Optimization of monitoring information analysis and of monitoring design plans in support of rational decision making for short- and long-term stewardship

This project addresses issues related to use of information analysis techniques and results for influencing regulatory practices. As an example, regulatory agencies currently require contaminated groundwater to be remediated to drinking water standards (DWS), in order to minimize health risk for potentially exposed individuals. However, in certain situations, background groundwater concentrations of one or more of the Constituents of Concern (COC) may be above the DWS, making it problematic to achieve DWS based clean-up standards. In such cases, it is reasonable to propose alternative remediation endpoints, based on background groundwater concentrations of the COC. This project continues developing and evaluating methodologies for identifying background levels of COC in different media, and for different regions.

When dealing with the various facilities of U.S. Department of Energy's (DOE) nuclear complex, the distinction between impacted and unimpacted (background) levels of Contaminants of Concern (COC) has to consider several complicated features of the nature of contamination: there are no recognized areas or monitoring locations on the site that have been designated as completely unimpacted; there are large spatial gaps in the monitoring of the overall groundwater quality; there are several spatially separated sources; the resulting plumes have intermingled; there are different sources for different Contaminants of Concern; and there is contamination from activities prior to the establishment of SRS. The problem of identifying background levels falls in between defined structure and predominant randomness. There is structure in the form of plumes and spatial/temporal trends, but also randomness (or variability) due to the mixing and degradation of plumes; intermittent and fluctuating sources; and interaction of pollutants with soils (such as leaching of metals due to acid pollution). Varying sampling, analysis and reporting procedures, and a large proportion of non-detects for several critical Contaminants of Concern, add to the complexity of analysis. Distributions for Contaminants of Concern are neither perfectly unimodal nor clearly bimodal. The problem has to be resolved by developing methodologies that combine and adapt existing statistical and geostatistical tools, because no single conventional approach is able to achieve the necessary distinctions.

This project can impact regulations specifying the environmental monitoring effort at DOE sites by identifying both redundancies and data gaps in current environmental monitoring practices. Identification of redundancies suggests changes in regulations pertaining to environmental monitoring and lead to more cost efficient ("optimal") monitoring programs that do not compromise the information content of the data. Identification of data gaps highlights deficiencies in the monitoring program and suggests additional monitoring leading to improved spatial and temporal resolution of contaminant concentrations.