A New Method of Delineating Three-Dimensional Capture Zones with Models

Abstract

The Air Force Center for Environmental Excellence operates several groundwater remediation systems at the Massachusetts Military Reservation (MMR). These systems involve multiple extraction and injection wells designed to provide complete or partial hydraulic containment of contaminant plumes. It is important in the design and optimization of these systems to be able to accurately delineate their hydraulic capture zones, which are three-dimensional and irregularly shaped. Traditional delineation techniques are based on visual identification of the envelope of pathlines leading to the extraction wells, the pathlines being generated by either backward or forward particle tracking in the simulated flow field. A new technique being used at the MMR involves forward tracking of particles from a dense three -dimensional array of starting locations without actually plotting the pathlines. Instead, the particle-tracking outcome is used to define a grid-based three-dimensional continuum of capture parameter, which can then be contoured in two-dimensional projections or otherwise rendered visible by three-dimensional visualization software. The resulting capture parameter is a three-dimensional scalar field that can be considered a quantitative spatial property of the flow regime. It can be combined with other scalar fields defined in the same grid, such as the concentration field, for visualization or for volumetric calculations. Arithmetic comparisons of capture parameter arrays generated at different pumping rates are also useful in sensitivity analysis.