Background/Objectives

The 2015 Battelle Bioremediation Conference in Miami was earmarked as the “Geology Revolution” in groundwater remediation. Since then, there have been several Battelle Conference Panels on Geology and Environmental Sequence Stratigraphy (ESS). Most recently at the 2023 Bioremediation Conference in Austin, Texas, the panel explored why sites are not reaching remediation goals. Quite often it is because there is not a geologic model for the site and, therefore, the subsurface geology is not well understood.

Approach/Activities

The focus of this panel is the state of the practice of groundwater monitoring wells. We have learned over the years that monitoring wells are not the optimal subsurface investigation tool, primarily because of the development of direct-push sampling and high-resolution site characterization (HRSC) technologies. However, groundwater monitoring wells remain a means for long-term monitoring of the groundwater conditions to satisfy the project data quality objectives and drive the performance of groundwater remediation systems. Groundwater monitoring wells are expensive to install and are long-term investments to meet the requirements of monitoring programs. The challenge is to make sure that each monitoring well adds value to the project. For many sites, monitoring well locations are based solely on two-dimensional groundwater data (e.g., contour maps of groundwater elevation and contaminant concentration or plume maps) and do not take into account a three-dimensional understanding of the site geology and hydrogeology, leading to poor monitoring well placement and design (e.g., screen intervals), which results in ineffective data. Long-term monitoring costs over many years add up and the data are used for critical site management decisions, therefore correct placement and design are important to the success of a project. Proper groundwater monitoring well location and design are the product of a robust geologic model and groundwater CSM and ultimately drives the success, sustainability, and climate resiliency of a groundwater remediation program.

Results/Lessons Learned

• Was information on the regional and local geology researched as part of the project scoping and preparing project plans for the site?
• Is the depositional environment of the subsurface geology at the site understood?
• Are groundwater monitoring well locations based on a robust and up to date geologic model and CSM?
• Consider geophysical methods as a first investigation step to evaluate the groundwater at the site.
• Consider a phased approach using HRSC/temporary grab sample wells to delineate the plume using transects.
• Consider what the impacts the CSM and groundwater monitoring program have on overall project sustainability/climate resiliency.
• The challenge to all is that you “know what the well will tell before you install it”.