2025 CSDMS meeting-134
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Contaminant Transport Characterization at Los Alamos National Laboratory using a Vadose Zone Vapor Plume Model
Debbie Sulca,
Los Alamos National Laboratory Los Alamos New Mexico, United States. dfsulca@lanl.gov
Monitoring of subsurface contaminants by N3B Los Alamos, indicates new locations of contaminant leakage below Material Disposal Area L (MDA L) at Los Alamos National Laboratory (LANL). The spread of legacy waste poses a concern of volatile organic compounds (VOCs) reaching the regional groundwater. The purpose of this work is to locate and quantify leak sources at MDA L and estimate the effect of contaminant removal periods on the plume using the LANL-developed finite volume multiphase simulator (FEHM) for gas transport modeling. The most prevalent contaminant in the plume is 1, 1, 1,- trichloroethane (TCA) and this species is used as a tracer to track plume movement in the model. The grid resolution is 10m horizontally and ranges from 1m to 25m vertically, with the higher resolution close to the surface. The model domain is set to LANL atmospheric pressure, constant temperature of 15C, and constant relative permeability set to 0 and 1 (-) for liquid and vapor, respectively. This work simulates saturation-dependent vapor diffusion of TCA via an isothermal two-phase (air-water) process. Over 140,000 nodes set the initial and boundary conditions related to pressure, saturation, and flow data (source/sink parameters). Readjustment of TCA concentrations will take place from November 30, 2016, to May 25, 2023 within the model. Soil vapor extraction (SVE) measurement periods at MDA L will be reflected in the simulations. Post-simulations, short-term SVE will be simulated to compare against SVE data from May 2024.
