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.

Guidance and advocacy from the U.S. Environmental Protection Agency (EPA) and ASTM International have made CSM development a best practice in the remediation industry (EPA 542-F-11-011 and ASTM E2532-06). Further, they have defined the current state of the practice in which CSMs are largely descriptive in nature and evolve as needed to address risk and the remedial actions required. This approach satisfies some stakeholder needs for flexibility, assimilation and integration of data to drive project decision-making. However, updating and improving the CSM remains reactive and contemplates a mostly static, descriptive model. The approach does not equip stakeholders with the predictive data or tools needed from the start to see the horizon ahead and operate within a quantitative framework in which data works continuously and transparently toward the goal of site closure. This is where the proactive approach of a process-based CSM stands out.

Efficient development and utilization of a process-based CSM can be facilitated using a digital site management tool. These tools link project datasets and software tools in a collaborative, digital format that allows project staff, owners, operators and stakeholders to easily access the process-based CSM throughout the project life cycle. This provides a highly efficient and cost-effective medium for teams to collaborate on every phase of the project, representing a significant improvement over individual project file sharing. This innovation improves quality and efficiency while facilitating new opportunities for remedy optimization.

Collectively, the process-based CSM and digital site management tool move the dynamic mechanisms that drive remediation performance to the fore, incorporating these into early stages of site decision-making. Combining a progressive, process-based site management strategy with advanced technology is improving the remediation process, from start to finish, by delivering focused remediation solutions that leverage the unique characteristics of each site. This approach reduces the cloud of uncertainty — including overall cost and risk — to deliver precise, predictable results.

 

Remediation project success hinges on a proactive approach that uses a process-based conceptual site model to inform each step of the remediation process.

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John Hesemann is a principal remediation engineer at Burns & McDonnell, where he leads the firm’s remediation technical practice. He leads multidisciplinary project teams and supports nationwide remediation strategy development, technical execution and thought leadership.