In the past number of years, regulatory agencies have come to consider risk-based site closures an acceptable cleanup strategy. The old-school approach relied upon a standard set of exposure assumptions expressed through default cleanup criteria that were applied to every site. This meant that they had to be conservative enough to be protective of human health and the environment in every possible site setting. While this provided clear guidelines, it was not always practical or even possible for these standards to be met, and many times the default criteria were overly conservative. Because of this, more and more state regulatory agencies have come to accept risk-based closures.
A major difference between risk-based closure and the traditional approach is that risk-based closure is based on site-specific exposure conditions. The primary objective of risk-based closures is preventing human or ecological exposure at unacceptable health levels, and because of this, it is possible that soil and groundwater cleanup may not even be necessary if the levels of contamination do not pose a risk to human health or the environment. However, if contamination is left in place a series of institutional and engineered controls are necessary to ensure that site conditions at the time of closure remain constant.
Following the issuance of documents officially recognizing risk-based cleanup approaches, the environmental consulting and legal community jumped on the opportunity to apply these methods as a cost saving measure. For example, consultants will argue that if contaminated groundwater is not being used for drinking water, there should be no drinking water exposure pathway; or because no one would be coming into physical contact with the contaminated water, there should be no dermal contact exposure pathway.
While this may seem to make sense, it is not an argument that is easy for regulatory agents to support. If all contaminated sites were handled this way, little to no cleanup would occur and contaminant conditions would continue for decades. This leaves little confidence to regulatory agents that the site’s long-term risks will be managed. Additionally, as the regulation of institutional and engineered controls becomes more stringent, the cost of these long term stewardship efforts is beginning to rival the cost of actual cleanup activities.
In the long run, it is best to actively remediate source areas and create a long-term monitoring strategy. This is the approach used by EnviroForensics, and we have obtained more regulatory closures of sites contaminated with dry cleaning solvents in the last five years than any other company. President and CEO, Stephen Henshaw, further details this approach in his article “Risk-Based Site Closures Should Include Remediating the Source Area” (as seen in the March 2014 issue of Cleaner & Launderer).