Technological advances in field analytical methods combined with experiences gained from historical hazardous waste site cleanup work have led to the EPA's Triad approach to hazardous waste site characterization, remediation, and closure.
For the last three decades, the United States has confronted the task of characterizing and remediating hazardous waste sites with environmental media and infrastructure (soil, surface water, ground water, buildings) that were contaminated from past activities. Cleanup activities are regulatory-driven. While the specifics and terminology differ from regulatory program to program, the general cleanup process is the same. Sites are identified, assessed for their potential risk to human or ecological receptors, remedial options reviewed, and actions taken if warranted. At each step of the process, critical decisions are made. Primary among these is the conclusion that portions of a site either pose a contamination concern and so require action, or that they do not. These decisions are based on data collected from the site, data that usually take the form of samples analyzed to determine the presence and level of potential contaminants of concern. Sampling and analysis programs are a critical component of every step of the cleanup process since their results are the foundation for each decision made.
In general, environmental cleanup programs have been criticized for their cost, duration, and efficacy (or lack of it). The way data collection programs have been conducted is partly to blame. Traditional sampling and analysis programs rely on work plans that dictate how many samples will be taken and where, and what laboratory analyses will be conducted on those samples. Turn-around times for laboratory analyses were usually measured in weeks with per sample costs at times running into the four figures. Error reduction focused on removing as much analytical error as possible from sample analyses, but ignored significantly greater decision errors introduced by basing decisions on a limited number of samples. When surprises were encountered in resulting data sets (e.g., contamination encountered where none was expected), site managers were left with the difficult choice of staging another expensive round of sampling, or basing decisions on incomplete data.
The past decade has seen significant advancements in data collection technologies and measurement systems. For many contaminants of concern it is now possible to obtain information about their presence and level in "real-time", or quickly enough to potentially affect the progress of sampling work. Advancements in Global Positioning Systems allow rapid determination of spatial locations. Direct push technologies provide a quicker and cheaper method for retrieving subsurface samples, and provide the possibility for pushing sensors into the ground for in situ measurements. In addition, over the last thirty years the cleanup professional community has gained a much better understanding of likely contamination scenarios, and the environmental fate and transport processes that determine the future state of contaminated sites. This knowledge, combined with technology advancements, opens the way for a new approach to address the uncertainty associated with hazardous waste site decision-making, and the design and implementation of sampling programs to support those decisions.
The EPA has coined the term "Triad" to refer to this approach. EPA believes that implementation of the Triad can potentially lead to faster and more cost effective hazardous waste site remediation, while at the same time improving the overall decision-making process and ultimately achieving the final goal of hazardous waste site programs: safe return of sites for productive use.