Stochastic Assessment of Groundwater Contamination Risks From Onshore Gas Development Using Computationally Efficient Analytical and Numerical Transport Models

Regulators require the gas industry to assess the risks of unintentional release of chemicals to the environment and implement measures to mitigate it. Industry standard models for contaminant transport in aquifers do not explicitly model processes in the unsaturated zone and groundwater models often require long run times to complete simulation of complex processes. We propose a stochastic numerical-analytical hybrid model to overcome these two shortcomings and demonstrate its application to assess the risks associated with onshore gas drilling in the Otway Basin, South Australia. The novel approach couples HYDRUS-1D to an analytical solution to model contaminant transport in the aquifer. Groundwater velocities and chemical trajectories were derived from a particle tracking analysis. The most influential parameters controlling solute delivery to the aquifer were the soil chemical degradation constant and the hydraulic conductivity of a throttle soil horizon. Only 18% of the flow paths intercepted environmental receptors within a 1-km radius from the source, 87% of which had concentrations of <1% of the source. The proposed methodology assesses the risk to environmental assets and informs regulators to implement measures that mitigate risk down to an acceptable level.

Effects of Using Air Curtains on Energy Consumption During Cooling Season Under Different Climate Conditions

In zones separated by doors with many entrances and exits, it is crucial in terms of energy consumption to protect the conditioned air in the indoor environment from the effects of outside air. The increase in door dimensions and opening frequency make this effect even more evident. Various methods are used to prevent leakage of outside air into the indoor environment. In this study, we investigated the effects of using air curtains on energy consumption during the cooling season in a factory building. The door width and height in this building, which has a high story height, were also large. These 26 doors must remain open all the time because of the production process. With a transient model developed on Transient System Simulation Tool (TRNSYS) coupled with Contaminant Transport Analysis Software (CONTAM), we showed the effects of using the air curtains in different climate conditions. As a result, we demonstrated that using air curtains will provide great savings, especially in cities with high cooling requirements.

Development of Smoothed Particle Hydrodynamics for Simulation of Flow and Contaminant Transport on Natural Urban Terrain and Streams

Smoothed Particle Hydrodynamics (SPH) method is proposed, as an alternative mesh-free approach to model all components of rainfall, surface runoff, fluid flow and contaminant transport with the representation of contaminant and fluid, as particles. By doing so, contaminant particles can be traced for the motion within runoff or fluid flow, even in the form of minute concentration which is difficult to render in conventional Eulerian grid methods. Weakly compressible SPH (WCSPH) is selected with cubic spline kernel, and the incorporation of Large Eddy Simulation (LES) representing turbulence effect. Various SPH diffusion formulations have been reviewed and selected. The selected SPH formulation for contaminant concentration is validated against analytical diffusion equation with boundary conditions of solid wall or free surface. The validated method is applied to calculate the overland flow and the contaminant transport on a model terrain and a real terrain geometry. The real terrain is a part of the city of Teluk Intan in Perak, Malaysia and is simulated using digital elevation model (DEM) data retrieved from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global Water Body Dataset (ASTWBD) for ground elevation and channel surface.