Formatted Title
Utilizing Electrical Hydrogeology to Create More Meaningful Conceptual Site Models (CSMs)
Background/Objectives
Vertical borings and monitoring wells are the most commonly used methods to characterize environmentally impacted sites. These methods are useful to help characterize horizontal distribution of contaminants and geologic layers. However, the industry has found that vertical tools are largely inadequate to locate and evaluate discrete vertical features and flow paths, which can significantly contribute to contaminant migration and distribution in the subsurface.
Electrical hydrogeology involves the use of specialty scanning technology, designed specifically for the environmental industry, to generate continuous 2-D subsurface electrical images across a project site and detect discrete vertical geologic features and migration pathways. This process has been used over the last two decades at sites in varying alluvial and bedrock geology for initial ultra-high resolution site characterization (Ultra-HRSC) and more robust remedial design characterization (RDC), resulting in more meaningful conceptual site models (CSMs). These data have also been collected temporally as 4-D datasets, to evaluate ongoing contaminant migration and/or effectiveness of remediation.
Approach/Activities
At a DNAPL site in fractured volcanic rock, electrical hydrogeology was successfully utilized to track preferential contaminant flowpaths related to geologic structures underlying the site. Identifying the deformation zone, faults, and fractures allowed these high flow zones where most of the contaminant migration was occurring to be targeted for remediation in a more effective manner. A process for successful management of these big data projects included 2-D/3-D data integration and visualization of multiple lines of evidence (including historical site data and follow up ground truthing confirmation drilling data), to allow robust virtual and/or in person collaboration by project team/stakeholders.
Results/Lessons Learned
Resulting 3-D data integrated with one-dimensional (1-D) point drilling data has provided insight into the complex contaminant distribution, subsurface microbial activity, and varying effects from remediation attempts. The integrated subsurface scanning data and confirmation drilling datasets provided sufficient data density and targeting ability, to be able to accurately determine origin and vertical extent of contaminated zones. This knowledge facilitated accurate CSM development and set the stage for focused and successful remediation.