What Makes Remediating Complex Sites So Difficult and Costly?
Date Posted: August 4, 2020
Posted In: Discussion,
by John Hesemann, Principal Remediation Engineer, Burns & McDonnell
As noted in a 2013 report from the National Research Council of the National Academies, the restoration of contaminated groundwater remains a significant technical and institutional challenge across the globe, despite billions of dollars of investment in over 30 years of intensive contaminant remediation efforts. Many of the sites that still require cleanup are considered complex due to their size, recalcitrant contaminants of concern — particularly complex combinations of contaminants — and/or complex hydrogeologic conditions.
Though these complex sites only comprise about 10% of the remaining remediation sites, they are predicted to account for approximately 70% of the total cleanup costs. This disproportionate cost-to-site ratio is common for many corporations burdened with remediation portfolios that continue to consume resources and pose ongoing risks.
For most of these sites, the existing conceptual site model (CSM) — the framework serving as the basis for remediation strategy and design development — fails to account for the range of possible mechanisms and processes that sustain and control the persistence of groundwater contamination plumes. This often results in costly, protracted remediation efforts that fail to achieve objectives within the anticipated timeframe. Identifying and quantifying the specific processes that affect contaminant behavior and remedy effectiveness for a given site is crucial to setting realistic objectives and designing cost-effective remedial actions.
The need to establish the dynamic processes at work in the impacted groundwater system — not just site conditions at a given point in time — has created a paradigm shift toward a process-based CSM. The distinguishing feature of a process-based CSM is its ability to use what is known about the geologic framework, contaminant characteristics and aquifer properties to begin identifying and characterizing the key dynamic processes early in the project life cycle. This allows these processes to be included in the CSM so they can begin driving project decision-making and strategy development. This is transformative because the data necessary to quantify dynamic processes are now conceptually as important as conventional, static site characterization elements. From a portfolio management perspective, the process-based CSM supports the implementation of focused, cost-effective remedies that deliver predictable results.