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Analytic Element Domain Boundary Conditions for Site-Scale Groundwater Flow Modeling Los Angeles Basin.
1U.S. Environmental Protection Agency, Office of Research and Development, 75 Hawthorne St, San Francisco, CA, 94105, USA.
Ground Water
|April 25, 2023
Summary
Physics-based groundwater flow models use boundary conditions (BC) for site cleanup. Analytic element models at the Dual Site demonstrated that while far-field results were stable, near-field flow fields were sensitive to BC choices.
Area of Science:
- Environmental Engineering
- Hydrogeology
- Computational Science
Background:
- Physics-based groundwater flow modeling is crucial for designing effective pump-and-treat systems for contaminated site remediation.
- Numerical modeling methods, including finite differences, finite elements, and analytic elements, necessitate the assignment of boundary conditions (BC) to the model's outer domain.
- Outer boundary conditions often do not align with natural hydrogeologic features, posing challenges in model setup.
Purpose of the Study:
- To demonstrate and evaluate groundwater flow modeling options for assigning boundary conditions (BC) in complex hydrogeologic settings.
- To assess the sensitivity of near-field and far-field simulation results to different BC assignments.
- To investigate the application of analytic element modeling for testing stress-dependent boundaries in pump-treat-inject system design.
Main Methods:
- Utilized physics-based groundwater flow modeling, specifically employing the analytic element method with the AnAqSim software.
- Developed and analyzed models at multiple scales: Dual Site, Los Angeles (LA) Basin, and West Coast Subbasin.
- Applied various boundary condition assignments, including extending model domains and specifying head-dependent flux conditions.
Main Results:
- The pump-treat-inject system at the Dual Site demonstrated effective hydraulic containment.
- Pathline envelopes showed relative insensitivity to the chosen boundary conditions in the simulations.
- Near-field domain groundwater flow fields exhibited sensitivity to the selected boundary condition types.
Conclusions:
- Analytic element modeling is a viable approach for evaluating groundwater flow dynamics and boundary condition impacts.
- Boundary condition selection significantly influences near-field flow fields, necessitating careful consideration in model calibration and design.
- The study successfully demonstrated the use of analytic element modeling for testing stress-dependent boundaries in the context of a Superfund site remediation design.
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