AquaResource Contributes Modeling Expertise to California Superfund Site Investigation

AquaResource applied a complex groundwater flow model to evaluate regional hydrogeologic data gaps.  As part of a characterization and contamination assessment at a superfund site in Southern California, AquaResource provided expert groundwater modeling services to help integrate available data and evaluate existing data gaps into a three-dimensional flow model. A regional-scale model was developed to characterize the interconnection of the site-scale groundwater flow with the larger system.  The site, located in a recharge area on top of a mountain complex, is underlain by a complex series of faulted, folded and fractured sandstone and shale formations.

To capture the complexities of the flow system, a state of the art model was developed using FEFLOW to rigorously follow steeply sloping bedding planes trending off-site.  FEFLOW was used to facilitate the finite element mesh conforming to the irregular faulted and folded layer structure with over 2.9 million discrete finite elements.

Through the model application a greater understanding of the regional groundwater flow system that determines potential contaminant pathways can be achieved.  The analysis approach taken is to use the model results and the insight provided to highlight the most pertinent data gaps such that further field work could be targeted in those areas that are most beneficial to characterizing the groundwater flow and contaminant transport system.  The fractured nature of the sandstone and shale units results in low matrix conductivity values with potentially much higher fracture conductivity.  Uncertainty analysis is essential to quantify the potential range of flow solutions.  The analysis approach taken is to use the model results and the insight provided to highlight the most pertinent data gaps such that further field work could be targeted in those areas that are most beneficial to characterizing the groundwater flow and contaminant transport system.  The fractured nature of the sandstone and shale units results in low matrix conductivity values with potentially much higher fracture conductivity.  Uncertainty analysis is essential to quantify the potential range of flow solutions.