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(420) Geospatial Decision Frameworks for Determining Sample Design and Areas of Concern in Ecological Risk Assessment. Stewart, Robert1, Purucker, Tom1, Jones, Brenda2, Welsh, Chris1, 1 2 ABSTRACT- The availability of desktop contouring and visualization packages facilitates the effective use of explicit, geospatially based decision frameworks in practical ecological characterization and risk assessment. These decision frameworks support identification of areas of concern by combining a ecological decision goal with the results of a geospatial analysis. Examples of a geospatial analysis includes contour maps, probability maps which quantify the spatial likelihood of exceeding a given value, and estimation variance maps. These results also serve as a basis for a number of secondary sampling designs aimed at refining the characterization and decision making process. Two frameworks for determining areas of concern or establishing a remedial design are presented. In the first approach known as the block scale, each point on the contoured map that exceeds the decision criteria is remediated. This is a fairly conservative approach that is well suited to defining hotspot areas. The second method, site scale, approaches the remedial design issue from the exposure unit perspective. Here the areas of highest contamination are remediated until the site wide exposure concentration falls below the decision criterion. In addition, to remedial frameworks, five sampling design algorithms are presented that explicitly assign new sample locations in a tertiary or secondary sampling. These include designs that sample where the largest data gaps appear, where hotspots are likely to be, and where the most uncertainty about exceeding a criteria exists. These methods not only refine the characterization process but can also refine the two decision frameworks described herein. Examples for each of these techniques are presented along with some straightforward cost benefit approaches. These techniques can impact the decision criteria choice itself as well as affect the total number of samples to take. Key words: decision-making, sampling, remediation, contouring |
