The Application of Sequence Stratigraphy to the Investigation and Remediation of LNAPL-Contaminated Sites

The heterogenous and complex nature of soil and groundwater systems leads to significant technical challenges in remediating Light Non-Aqueous Phase Liquid (LNAPL) contamination and achieving cleanup goals within reasonable timeframes. Therefore, implementing a correlation approach that adequately addresses subsurface heterogeneity between sampling locations is critical for effective management of LNAPL-contaminated sites. In traditional LNAPL remedial investigations in clastic environments, correlation has typically been conducted using ‘lithostratigraphy’, which connects like-lithologies without recognizing the heterogeneity of subsurface sediments between boreholes. The resulting ‘layer cake’ stratigraphy of the subsurface is often too simplistic and inadequate for developing effective remedial strategies. In contrast, the sequence stratigraphic approach (supported by facies analysis) provides a more realistic subsurface correlation based on the predictable distribution of sediments in different depositional environments. The three-dimensional geologic framework derived from sequence stratigraphy can be used to map the heterogeneity between coarse- and fine-grained units across multiple scales and beyond the existing site data set. Moreover, this framework can be integrated with site hydrologic and chemical data to identify sediments with high- and low-fluid transmissive properties. This chapter demonstrates how a sequence-stratigraphy-based conceptual site model can be used to identify preferential LNAPL migration pathways and inform effective remedial decision-making.