Groundwater flow modeling provides critical insights throughout the life cycle of an effective remedy. During the creation of a conceptual site model (CSM), information about the location and movement of groundwater can assist in identifying the source of contamination and assessing plume concentrations and behavior. During remedy design, an in-depth understanding of subsurface groundwater provides basis for alternatives comparison and allows us to select cost- and labor-effective remedies. During implementation and closure, groundwater models provide insights about how we measure performance and outcomes.
Since its inception, groundwater modeling has been used as a tool to help understand and predict the behavior of groundwater as it makes its way through the subsurface. Early attempts at modeling were made using physical models constructed of materials like those found in the subsurface. The use of sand table models then shifted to electrical models that used the movement of electricity through circuits and resistors as an analogy for the movement of water through various types of subsurface materials. These early models were difficult to adapt based on new information gathered during field investigations. The age of modern computing gave rise to computer programs such as MODFLOW that allowed more ease in updating and calibrating groundwater models. As computing power and programming advanced, the graphical user interface made these adjustments to models and experimentation with various working hypotheses rapid and more intuitive.
Currently, groundwater models and the prevalence of three-dimensional interpretation and visualization platforms has vastly increased our ability to synthesize large amounts of data and rapidly incorporate them into groundwater flow models. This enables us to rapidly distill site data into a working CSM. These initial site conceptual models serve as the starting point for groundwater flow models. The groundwater flow models are then used to probe the CSM for data gaps that should be addressed during site related activities. As these data gaps are filled, the newly generated data is rapidly assimilated into the groundwater model, which is updated to reflect the new information, until ultimately the data gaps are filled and the CSM is a robust representation of the real-word, site conditions.
During this process of CSM refinement and groundwater modeling, the groundwater model can often be used to help to identify likely sources areas based on groundwater contaminant concentrations and plume concentrations. In some cases, the modeling will identify sources in locations not previously suspected. This can enhance the approach to groundwater remediation by focusing remediation efforts in areas where they will have the greatest impact.
Modeling is also used to evaluate the impact of multiple remedial options and help to develop cost benefit analyses for the potential remedial options to be employed at a site. These cost-benefit analyses also typically include an assessment of cleanup time frames that can be used to develop the most cost-effective option for addressing sites within the relevant regulatory framework.
The use of groundwater flow models in developing comprehensive conceptual site models cannot be overemphasized. Groundwater modeling is an effective tool for use at every step in the evaluation and remediation of an impacted site. The insights offered by engaging in the modeling process provide more rapid and effective investigation and cost-effective remedy selection.