Model Changing Conditions, Complex Processes and Uncertainty
Extend a verified layered model when the conceptual site model requires more than routine transport assumptions.
Represent existing contamination, nonlinear chemistry, decay, engineered collection, time-dependent properties and parameter uncertainty while keeping each added assumption visible for review.
Start with the Process That Changes the Decision
Use only the special features supported by the project conceptual model and available evidence.
Add Complexity Only When the Conceptual Model Requires It
Begin with a verified core model. Add one advanced process at a time, document its parameter basis and compare the result with the baseline before combining features.
- Confirm the core layers, boundaries and units first
- State the physical process the feature represents
- Use project-supported or referenced parameter values
- Check limiting cases and expected model behavior
- Report the feature’s effect on the engineering conclusion
Extend the Layered Model for Advanced Conditions
These capabilities address specific processes and uncertainty questions beyond routine model definition and output.
Initial Concentration Profile
Define contamination already present within selected layers at the beginning of the simulation.
Nonlinear Sorption
Use Freundlich or Langmuir relationships when a linear distribution coefficient does not represent sorption behavior.
Biological & Radioactive Decay
Represent applicable first-order loss processes using project-supported decay assumptions.
Passive Sinks
Model a collection or receptor layer that removes contaminant mass reaching its location.
Time-Varying Properties
Change applicable source, layer or system properties across defined periods of the assessment.
Sensitivity Analysis
Vary selected inputs systematically to identify the assumptions that most affect the prediction.
Monte Carlo Simulation
Sample defined parameter distributions to evaluate a range and probability of modeled outcomes.
Combined Scenarios
Use compatible features together when the conceptual model and input evidence support their interaction.
Connect Each Option to Evidence and a Review Question
| Feature | Represents | Required Basis | Review Focus |
|---|---|---|---|
| Initial profile | Contaminant present at time zero | Site characterization and profile interpretation | Does the starting distribution match the assessment date? |
| Nonlinear sorption | Concentration-dependent retention | Freundlich or Langmuir parameters | Are the relationship and concentration range supported? |
| Decay | Biological or radioactive mass loss | Applicable rate and environmental conditions | Could daughter products or changing conditions matter? |
| Passive sink | Mass removal at a collection or receptor layer | Hydraulic and collection-system behavior | Is removal sustained over the modeled period? |
| Time-varying properties | System performance that changes over time | Defined periods and property values | Are transitions and degradation assumptions defensible? |
| Sensitivity | Influence of selected inputs | Baseline and justified ranges | Do the tested ranges cover material uncertainty? |
| Monte Carlo | Probabilistic parameter uncertainty | Distributions, bounds and correlation assumptions | Are probability statements supported by the input data? |
Build Advanced Scenarios without Losing Traceability
Combine features only after their individual effects are understood.
Changing Barrier and Collection Performance
Pair time-varying properties with a passive sink to examine staged degradation, failure or collection-system changes.
Pre-existing Reactive Contamination
Combine an initial profile with supported sorption and decay processes to represent contamination already within the profile.
Uncertainty and Design Comparison
Use sensitivity analysis to identify influential inputs before defining a focused Monte Carlo assessment.
Evaluate Formulations for Less Routine Transport Problems
POLLUTE examples also document specialist applications beyond the seven principal special features.
- Fractured media: represent a bounded transport case where the documented formulation matches the rock system.
- Two-dimensional plane dispersion: evaluate the specific documented configuration; use MIGRATE where a general explicit 2D framework is required.
- Phase change: examine a documented volatile-contaminant system in which phase behavior affects transport.
- Geomembrane and multiphase cases: review the applicable example assumptions before adapting them to a project.
Before Selecting a Specialist Case
- Define the process and decision.
- Confirm dimensional suitability.
- Review the documented example.
- Verify required parameters.
- Test expected limiting behavior.
- Have a qualified professional review the interpretation.
Keep Every Additional Assumption Reviewable
Verify Core Model
Confirm layers, boundaries, units and baseline behavior.
Add One Feature
Introduce the required process separately.
Define Parameters
Document values, ranges and supporting evidence.
Check Behavior
Test limits, trends and physical consistency.
Compare Scenarios
Measure the effect relative to the baseline.
Review and Report
Explain assumptions, uncertainty and decisions.
Use Advanced Features for Specific Engineering Questions
Existing Contamination
Begin from a measured or interpreted concentration profile.
Landfill Systems
Assess changing barrier and collection-system performance.
Reactive Transport
Represent nonlinear sorption and applicable decay processes.
Uncertainty Review
Evaluate influential assumptions and probabilistic outcomes.
Confirm the Feature Fits the Model and the Evidence
- Is the advanced process material to the decision?
- Does POLLUTE’s formulation match the site conceptual model?
- Are required parameters available at an appropriate quality?
- Are units, ranges, distributions and correlations documented?
- Has the feature been tested separately from the baseline?
- Are combined features physically compatible?
- Are uncertainty and limitations visible in the report?
- Has a qualified professional reviewed the final interpretation?
Recommended Evaluation Path
Use a representative project and reproduce one documented example before adapting an advanced configuration.
Review the Documented Features and Examples
Special Features Guide
Review GAEA’s overview of advanced POLLUTE configurations.
Read the Special Features guideCore Features
Confirm the standard model setup, boundaries and results workflow first.
Review POLLUTE Core FeaturesEvaluate the Advanced Features with Your Own Model
Begin with a verified core configuration, add only the required process and compare the result with the baseline.
