Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:1850:p62
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 1850 (pt 62/117)
Character Range: 518836–521823

study, comprising a review of existing information and consultation with relevant stakeholders to define the objectives of the study and the scope of work
    * development of a CSM of the saturated and unsaturated zones and consideration of how the contaminant fate and transport processes can be represented in a model
    * selection of an appropriate model based on the objectives of the study, the CSM and data availability
    * construction/application of the model and comparison of model results with field data to assess model validity
    * sensitivity analysis to determine which parameters have the most significant influences on the model results
    * uncertainty analysis to take account of uncertainty in the conceptual model, parameter measurement and natural variability of parameters
    * assessment of results and reporting, including assumptions and limitations.
The development of the CSM is a critical step and should identify and consider the relevant aspects of the flow system and the contaminant transport processes likely to be operating. In constructing the CSM, a number of assumptions regarding the system behaviour will need to be made. The assessment should consider whether the assumptions and uncertainties are important, that is, whether it is possible to adopt a relatively simple mathematical model of contaminant transport or, alternatively, whether understanding and definition of the system behaviour is so poor that development/use of a mathematical model is inappropriate, and that the first priority should be to obtain further site-specific information.

A phased approach to using mathematical models is recommended, moving from simple calculations to analytical models and, finally, to numerical models if appropriate. The quality and quantity of the data available should be taken into account when selecting the mathematical model. Where data is limited, complex models are generally not appropriate. In each case the selection of the modelling approach should be justified and appropriate to the available data and understanding of the system behaviour.

Data collection should be an iterative process and linked to the development and refinement of the CSM and the mathematical model. Site-specific data should be obtained whenever possible and, for certain parameters, site-specific data is essential. Literature values may need to be used for some parameters, and the values selected will need to be justified.

Construction/application of a model using parameter data will generally involve a calibration step whereby the model parameters are adjusted within a credible range to achieve the best fit between model results and field data. If an acceptable fit cannot be obtained in this calibration step, the appropriateness of the model, the need for further site-specific data, and the CSM should be reviewed.
When completed, the model should be fully documented, including the objectives of the model, the model code used and its