GasSim is a probabilistic model. This means the uncertainty in particular model parameters can be represented in a model simulation to provide a measure of the effect of the uncertainty of the input parameters in the model outputs. GasSim uses a Monte Carlo simulation technique to select values for parameters in the model by random selection from a user-defined range of potential inputs. This process is repeated many times to give a range of output values. Users are guided via a graphical representation of the conceptual model to enter site specific values into the relevant parts of the model.

New to GasSim 2 is:

• Cellular filling, full spatial representation of cells and individual gas plant;
• All gas plant have individual emissions simulated and the facility to turndown
  flares or engines;
• Automated assessment of atmospheric impacts at Tier 1 (screening), and a fully
  Environment Agency compliant Tier 2 atmospheric dispersion model based on
  the USEPA's AERMOD;
• Representation of landfills and landraise landforms;
• Flexibility to simulate adjacent landfills and include or exclude impacts from
  these, to represent e.g. non-IPPC permitted cells providing fuel for utilisation plant.

GasSim 2 outputs can be divided into six sections:

• Gas Generation and Emissions - GasSim 2 determines the quantity of gas
  generated and fugitive emissions on a cell by cell basis. Cells can exhibit
  different engineering, and the history of capping, sacrificial gas collection
  and permanent gas collection systems can be represented.
• Atmospheric Dispersion of fugitive and combustion plant emissions;
  Tier 1 screening; Tier 2 AERMOD dispersion; and export to Tier 3 models.
  Flares and gas engines of various designs can be represented.
• Lateral Migration - concentration versus distance graphs for individual cells
  of different engineering designs;
• Pollution Inventory Reporting for gas emissions;
• Global Impact - the global warming potential of greenhouse gas emissions;
• Exposure Concentrations in mg/kg (bodyweight)/day to specific receptors.

The current version of GasSim is Version 2.0. Contact the Golder Associates
Help Desk for information about software upgrades