Spatial approaches for subsurface sample design, characterization, and decision support

Sampling, characterization, and remediation of the subsurface can be a complicated and costly endeavor. The addition of depth leaves many of the sampling and scanning technologies targeted at surface designs unable to provide meaningful data. For this reason methods such as MARSSIM are not always applicable at depth. Physical characteristics of the subsurface can be heterogeneous and unlike the surface often impossible to fully observe. Costs associated with sampling are prohibitive and often result in inadequate data sets. Additionally, information comes in a number of qualitative and quantitative forms including geology, historical records, and previous sampling efforts. Without a decision framework that can encompass these varying influences, assessors often resort to ad-hoc methods for making decisions. These decisions can be sub-optimal and lack a defensible process. Well organized decision support tools based on standardized approaches have the capability of creating transparent and reproducible outcomes. Due to the spatial nature of environmental contamination, decision support and modeling tools such as the freeware Spatial Analysis and Decision Assistance (SADA) which consider this spatial element are particularly useful in creating sample designs, visualizing or modeling site conditions, and evaluating remedial designs. SADA incorporates a number of major mainstream tools including data analysis, risk assessment, visualization, GIS, sample design, remedial design, and cost/benefit analysis. SADA can be used for either surface or subsurface applications. The software provides an open but guided modeling and decision environment that ties these major modeling features together under the umbrella of decision support. SADA provides a guided flow through the major elements of environmental analysis: initial sample design, data analysis, risk assessment, spatial modeling, remedial design, secondary sample designs, and confirmatory sampling or monitoring. Subsurface examples are used to present methods from each of these elements and highlight the use of a decision support tool from cradle to grave. Emphasis is given to methods that efficiently characterize and evaluate remedial alternatives with particular decision goals in mind. SADA is developed by the University of Tennessee and funded by the Nuclear Regulatory Commission, the Environmental Protection Agency, and the Department of Energy. A free copy may be obtained at http://www.tiem.utk.edu/~sada/.