Vadose Zone & Groundwater Contaminant Modeling
Vadose (unsaturated) zone lies above the groundwater table and controls how water and contaminants migrate vertically downward. Groundwater flow models are tools used to conceptualize, quantify, and predict how groundwater moves through subsurface geologic materials under natural and engineered conditions. Models are based on physical laws, hydrogeologic characterization, and numerical solution methods. Contaminant fate and transport modeling evaluates the movement of chemicals through the vadose zone and groundwater via: advection, dispersion, molecular diffusion, sorption/desorption, biodegradation/transformation, volatilization, and phase partitioning. AA GeoEnvironmental reviews whether these mechanisms are represented at a level of complexity justified by available data and project objectives.
Models reviewed by AA GeoEnvironmental include:
- One-dimensional and multi-dimensional vadose zone models.
- Numerical models (finite difference or finite element).
- Coupled vadose zone–groundwater models.
- Steady-state and transient simulations.
- Scenario-based and sensitivity analyses.
Our reviews meticulously examine each element of the model’s design and construction, including the conceptualization of CSM, calibration processes, simulation scenarios, sensitivity analyses, quantification of uncertainty in model predictions, and validation procedures.
Vadose zone, groundwater flow, and contaminant modeling are commonly applied to:
- Environmental Site Assessment (Phase II and beyond).
- Vapor intrusion and indoor air evaluations.
- Remedial feasibility and performance assessment.
- Long-term contaminant plume behavior evaluation.
- Source longevity and attenuation analyses.
- Support for monitored natural attenuation (MNA) evaluations
AA GeoEnvironmental evaluates whether the numerical model is consistent with:
- Site stratigraphy, observed field data, and heterogeneity.
- Hydrogeological framework and flow directions.
- Source characteristics and release mechanisms.
- Monitoring well network design and data coverage.
- Temporal variability and boundary conditions.
- Parameter sensitivity, assumptions, uncertainties, and limitations.
Model review is often strengthened by integration with: geochemical data interpretation, statistical evaluation of contaminant concentration trends, and data quality. AA GeoEnvironmental applies an integrated approach to ensure modeling results are consistent with multiple lines of evidence.
What this Service Is
- Third party peer-review interpretation of subsurface analytical and numerical models.
- Evaluation of model- input parameters, uncertainties, assumptions, and limitations.
- Support for defensible model conclusions.
What this Service Is Not
- Model construction/reconstruction, development or ownership.
- Regulatory permitting or approval.
- Legal, compliance, or decision-making authority.
The decision-making, regulatory compliance, and model-development responsibilities remain entirely with the clients..