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Site Assessments

The systematic planning component of the Triad approach can be used as the organizing framework for conducting a site assessment.

During the site assessment (SA) process, information is gathered to determine if there is the potential for contaminants to exist at levels that would pose human health or ecological concerns. The systematic planning component of the Triad approach can be used as the organizing framework for conducting a site assessment. While the use of systematic planning in an SA will not likely lead to immediate cost savings, it can improve the quality of SA decisions and it can set the stage for a more complete application of a Triad approach during subsequent activities at the site if a remedial investigation (or equivalent) is required.

Site assessments involve the compilation and review of a wide range of information regarding the potential contamination status of a site. These data include reports, aerial photographs, interviews with individuals familiar with site activities, historical record reviews, site reconnaissance visits, etc. The process of pulling these disparate sources of information together, organizing material, and drawing conclusions pertinent to the site assessment is equivalent to developing an initial CSM for a site. The details of CSM development from a Triad perspective are discussed in more detail in the section entitled Systematic Planning.

One possible component of a site assessment is a site inspection (SI). A SI typically includes judgmental sampling of media most likely to be affected by contamination. The purpose of judgmental sampling in an SI is to investigate worst case scenarios for contamination presence. The information obtained from those samples may be used to support a decision that no further investigation is warranted for the site. Consequently, the CSM must be capable of supporting that conclusion with an acceptable level of decision uncertainty, assuming the selected sampling locations yield nothing of significance. A properly formulated CSM should be the guide in the selection of sampling locations and the justification for why those locations were selected. Basing a No Further Action (NFA) decision on information collected during an SI is an excellent example of a "weight of evidence" approach to decision-making advocated by the Triad. "Weight of evidence" decision-making will be discussed in more detail in the section entitled Systematic Planning. In this case, the results of limited sampling are combined qualitatively with all of the other information gleaned during an SI to reach NFA conclusions.

At this stage of the process, specific contaminants of concern may or may not be known: knowledge may be limited simply to potential classes of contaminants that could be present (e.g., fuel oil, PCBs, heavy metals, pesticides, chlorinated solvents, etc.). Given the limited nature of sampling, it is seldom cost-effective to implement on-site laboratory capabilities to support an SI. However, real-time measurement techniques can be used to screen samples for the presence of contaminant classes (e.g., immunoassay techniques for PCBs, in situ readings with an XRF for selected metals, etc.), identifying those locations or samples of greatest concern that then can be sent for off-site analysis with techniques that have better specificity and quantification capabilities. This type of screening can result in much greater spatial coverage for a site for the same limited SI characterization dollars.

By its nature, an SI is exploratory, with site conditions often encountered that were not expected. A Triad-based dynamic work strategy is a logical approach to this type of exploration. In this particular case, the dynamic work strategy would reflect the CSM, selecting known locations of interest that should be sampled, but would also identify the types of general site features that might warrant sampling if encountered, and specify actions to be taken if sample screening produces results of concern. The typical action would be flagging a particular sample for more definitive off-site laboratory analysis.

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