TREECS provides the user with the capability to conduct sensitivity/uncertainty in Tier 2 analyses. The S/U module in TREECS is based on the SUM3 software (http://mepas.pnl.gov/FramesV1/sum3home.stm) developed by Pacific Northwest National Laboratory (PNNL) which uses Monte Carlo with Latin Hypercube Sampling (LHS). Additional information will be provided here once the TREECS for Tier 2 analyses software is nearer deployment.
The S/U module will allow the user to declare selected inputs as uncertain or sensitive. Statistical distributions and the distribution parameters must be specified for each uncertain input. The user also defines which outputs to monitor to assess variability, such as sediment and groundwater MC concentrations for specified years. The number of Monte Carlo realization simulations are also specified. Following the Monte Carlo simulations, the S/U module calculates the cumulative probability distributions of the monitored outputs and attributes of those distributions. For example, the user can examine the upper and lower 95% confidence limits of predicted sediment concentrations versus time as shown in the figure below.