Stratigraphic Flux – Applying Sequence Stratigraphy and High-Resolution Site Characterization to Find Contaminant Flux

Background/Objectives. The advent of mass flux and high-resolution site characterization methods in recent years has led to more quantitative conceptual site models. Stratigraphic flux combines relative mass flux derived from high resolution site characterization with a sequence stratigraphy perspective on geologic interpretation to provide a framework for classifying and ranking transport potential: transport zones, slow advection zones, and storage zones. The goal of the approach is to develop a 3D stratigraphic flux model to enable stakeholders to understand the controlling influence of aquifer architecture on plume dynamics, thereby improving the reliability and cost-effectiveness of restoration strategies.

Approach/Activities. To demonstrate the utility of the method real-time, high-resolution site characterization methods were used to obtain co-located stratigraphy, permeability, and TCE concentration data in transects downgradient of a former chrome pit. Whole core saturated soil sampling and calculated equivalent groundwater concentrations were performed to map distributions TCE and daughter products, as well as total chrome. Comparative analyses were completed using HPT and vertical aquifer profile groundwater sampling at select locations to verify method results.

Results/Lesson Learned. The 3D stratigraphic flux model showed that significant TCE source mass continues to reside in the saturated clay-rich soils. Groundwater concentrations in the alluvium decreased several orders of magnitude with distance from the source and limited transport was focused in a relatively narrow band in the unconsolidated aquifer. The results from this project suggest that the stratigraphic flux approach is a useful tool for tracking contaminants at sites with complex geology, allowing for targeted remedial approaches.