In September 2017, the U.S. Environmental Protection Agency published a Technical Issue paper for groundwater, with co-authors including me and my Burns & McDonnell colleagues Mike Shultz and Colin Plank. It introduced Environmental Sequence Stratigraphy (ESS) as a best practice for environmental site management at complex contaminated groundwater sites. Since then, the recognition of ESS as a best practice has increased dramatically, helping to improve decision-making and guide development and implementation of environmental remediation projects.
Early adopters now have the opportunity to leverage the results of ESS evaluations and enhancements to improve remediation performance throughout the project life cycle.
The immediate benefit comes from the ability to prepare more reliable and detailed conceptual site models (CSM), which are used as the basis for selecting remedies and designing remedial actions at complex sites. This is an excellent start, but it does not represent a “finished” or static product. ESS technology has much more to offer.
Building a Robust CSM
Mapping the subsurface and optimizing the site cleanup strategy are crucial to maximizing value and minimizing cost throughout the life cycle of a remediation project.
CSMs have historically provided a very conceptual, sometimes cartoonish presentation of the subsurface and contaminant distribution. The ESS-enhanced approach results in a far more quantitative CSM that reduces uncertainty, risk and cost. We take existing data and apply the science of stratigraphy in careful detail to create a description of the subsurface that is geologically sound and directly addresses the heterogeneities that govern contaminant distribution and transport. These mechanisms have a direct and dramatic effect on the feasibility and effectiveness of most remediation technologies.
Leveraging Life Cycle Updates
Maximizing the value of the ESS evaluation depends on recognizing that the ESS-enhanced CSM is an evolving conceptual model, refined through an iterative process as the remediation project advances.
The ESS process begins by engaging a trained stratigrapher to develop a detailed description of the subsurface. This initial CSM can then be used during site investigation and groundwater monitoring phases to make significant decisions about where monitoring wells should be installed and what data should be collected. As the field work is conducted and subsurface data are collected, the quantitative CSM is continually refined.
When conducting feasibility studies to evaluate cleanup alternatives, the detailed CSM is used to identify the critical uncertainties that impart risk to project success. In addition, the CSM often reveals valuable opportunities to optimize remediation efforts by focusing on specific contaminant mass storage zones, transport pathways or other site-specific features.
Quantitative insights can be further developed for each phase of the remediation process, from the initial studies through design, optimization and ultimately setting the pathway to project closure. As subsurface uncertainties are progressively reduced, the possibilities for cost savings and expediting project completion are greatly enhanced.
Anyone challenged by a site with contaminated groundwater can benefit from this scientific approach. The insights into geology, hydrology and chemistry can be substantial, but optimal implementation depends on the efforts of an integrated team of practitioners applying ESS concepts throughout the project life cycle.
Want to know more about how ESS is revitalizing the geological approach to groundwater remedies?