Reducing Uncertainty in a Phase 2 ESA with the Triad Approach

The “hidden” and non-homogeneous nature of contamination at brownfield sites provides unique challenges to environmental site assessment (ESA) and clean-up work. 

What Are The Implications of Brownfield Contamination?

Brownfield contamination ignites potential for fatal “flaws” like missing impacted soil or groundwater at a previously determined “clean” site. 

In order to effectively address the financial, environmental, and health-related risks associated with this missing information, AEL follows the Triad approach developed by the US Environmental Protection Agency (EPA)

What is The Triad Approach?

The Triad approach allows AEL to manage the uncertainty in ESA 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: 

  1. Laboratory and real-time site measurements of environmental data guided by the CSM
  2. Dynamic site-specific work strategies. 

By using this approach, the sampling, analytical, and relational uncertainties of this data are rigorously managed in a cost-effective manner.

[Recommended Reading: Understanding a CSM – The basics in Ontario]

Why Is It Important To Conduct A Phase II CSM?

Phase II CSM builds on the data gathered during Phase I ESA. The objective is to identify and delineate areas of environmental concern guided by understanding the site’s geological, hydrogeological, and contaminant characteristics. 

[Recommended Reading: Are All Phase I ESAs Equal?]

What Type of Site Data Does The CSM Gather?

During Phase II CSM there is plenty of data that is gathered to identify and pinpoint gaps in the initial sampling data including: 

  • Groundwater gradient and direction
  • Soil classification
  • Stratigraphy
  • Contaminant type
  • Subsurface concentrations
  • Subsurface transport mechanisms 

These data points are also utilized to modify the CSM and present a more detailed understanding of the site.

What Happens When There Is Limited Information?

When insufficient information exists on the location of impact, AEL establishes a grid sampling pattern.

The grid sampling pattern helps ensure adequate site characterization is in place to cover the whole site when no historical information is available. From time to time, a sampling map is drafted based on known areas with little known testing results.

How Do You Measure CSM Results in Real-Time?

Several 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 allows the project engineer to develop and modify their understanding of a site in real-time and employ some Triad-specific dynamic work strategies.

What Are Triad-Specific 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, including:

  1. Stepping out in a vertical and/or horizontal direction from impacted samples 
  2. 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.
  3. 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. 
  4. GIS-based data maps while in the field from real-time site measurements of contaminants 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.

Need assistance regarding site sampling results? Call us at (800) 267-4797 or contact us here.

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