Using ArcGIS to Monitor the Effect of Water Table Fluctuations on the Behavior of Nonaqueous Phase Petroleum

A conceptual model was created using ArcGIS to analyze and illustrate the behavior of light nonaqueous-phase petroleum (LNAPL) in a heterogeneous aquifer system under an active petroleum refinery. The information obtained was used extensively to demonstrate the influence of water table fluctuations on apparent product thickness in site monitoring and recovery wells. The ArcView Spatial Analyst extension was used to contour groundwater elevations and LNAPL thickness as recorded during site-gauging events. The charts and contour maps created were used to compare ground-water elevation and product thickness data for the same month exactly two years apart (April 2000 and April 2002). Data collected from April 2000 was recorded during a period of long-term high water table conditions. By contrast, data from April 2002 was collected during long-term low water table conditions, a result of a severe regional drought. To further visualize the overall extent and thickness of the product plume across the site during periods of high- and low-water conditions, a three-dimensional model using the ArcView 3D Analyst extension was created in ArcGIS. Currently, the model is being used to visualize product behavior, analyze seasonal and climatic effects to anticipate potential changes in product recovery rates, and support the design of appropriate remedial systems across the site.

Courtesy of Langan Engineering and Environmental Services, Inc.