Reducing Uncertainty in a Phase II ESA with the Triad Approach

The “hidden” and non-homogenous nature of contamination at brownfield sites provides unique challenges to environmental site assessment and cleanup work with significant potential for fatal “flaws” like missing impacted soil or groundwater at a previously determined “clean” site. In order to effectively address the potential financial, environmental, and health related risks associated with this missing information, AEL follows the Triad approach developed by the US Environmental Protection Agency (EPA). This approach allows AEL to manage uncertainty in environmental site assessment and cleanup work at brownfield sites that otherwise could cause excessive or intolerable errors in decision making.

The Triad of project planning; dynamic work strategies; and real time contaminant measurement uses modern technologies and strategies to rapidly and efficiently build a Conceptual Site Model (CSM) tailored to support assessment and remedial decision-making needs. Under Triad, decisions are based on both laboratory and real time site measurements of environmental data guided by the CSM (project plan) and focused by dynamic site specific work strategies. By using this approach the sampling, analytical, and relational uncertainties of that data are rigorously managed in a cost-effective manner.

Systematic Project Planning

Building on the CSM developed during Phase I ESA work, Phase II CSM planning focuses on identification and delineation of areas of environmental concern guided by an understanding of the site’s geological, hydrogeological and contaminant characteristics. Initial sampling data regarding groundwater gradient and direction, soil classification and stratigraphy and contaminant type, concentrations and transport mechanisms in the subsurface are used to modify the CSM and present a more detailed understanding of the site and to identify gaps in the sampling data. When insufficient information exists on the location of impacts AEL establishes a grid sampling pattern in order to ensure adequate site characterization, to cover the whole site (when no historical information is available) or plan a sampling map based on known as well as areas that have little known testing results.

Measuring Results in Real Time

A number of technological advancements in testing for typical contaminant groups like hydrocarbons, volatile organics, and metals have been developed over the past decade. The best of these technologies provide quantitative or semi-quantitative analytical results in real time, are portable and provide analytical results below site action levels. As a result they represent an excellent opportunity to gain valuable site information. The availability of these results while still in the field allow the project engineer to develop and modify their understanding of a site in real time and employ a number of Triad specific dynamic work strategies.

Dynamic Work Strategies

Several dynamic work strategies are available to the project engineer to further refine their understanding of the CSM while still in the field. These include simple techniques like stepping out in a vertical and/or horizontal direction from impacted samples and more robust techniques like developing lower (and upper) investigative limits for a site to determine which sample results represent the greatest “risk” to the understanding of a site if not well defined. Another technique, adaptive cluster sampling, allows for the statistically defensible collection of data for random deposition of contaminants at a site like spent armament test fires, multiple air emission point sources, and cumulative small varied filling of a site. The use of GIS based data maps while in the field from real time site measurements of contaminants also greatly enhances the site understanding and CSM development.

To learn more about real-time site sampling, check out AEL’s posts about site screening and on-site testing.

AEL staff make decisions in the field based on site sampling results.