Contaminant Transport Modeling At Underground Gasoline Tanks Sites

Freshwater is a vital commodity. With the ever increasing population and the limited water resources around the world, groundwater is considered one of the strategic supplies of freshwater for agricultural, domestic and industrial uses. Groundwater contamination presents a major environmental hazard. Contamination sources include leaching of agricultural fertilizers and pesticides, leakage from sewers and sewage systems, and spills from underground storage tanks (USTs). Some of these pollutants are biodegradable, such that natural filtration and adsorption may remove part of unsuitable present organisms. On the other hand, chemical contaminants are of persisting nature, and thus more hazardous. One of these is gasoline contamination from USTs, which poses severe contamination problems to the groundwater aquifers. A mathematical and numerical model is developed to simulate the transport and fate of Non-Aqueous Phase Liquids (NAPLs) in near-surface granular soils. The movement of NAPLs through porous medium can be described by a coupled set of non-linear partial differential equations that are generated by combining balance equations with constitutive relationships. Two-phase coupled flow, including hystersis and mass transfer effects, is considered. The behavior of NAPLs through groundwater aquifers is presented, which help for proper remediation. The developed model is used to investigate pollution behavior through saturated zones. Plume migration is presented for two different cases, first when continuous slow rate of NAPL reach the water table and second when large volume of NAPL suddenly reach the water table over relatively short time.