The use of STOMP to evaluate the impact of heterogeneity on LNAPL pool configuration

Subsurface contamination by light non-aqueous phase liquid (LNAPL) is a widespread problem. A common LNAPL contamination is gasoline from leaking underground storage tanks (LUST). Heterogeneities in the media properties play a crucial role for defining the LNAPL movement and distribution in the subsurface. Hence, enhanced understanding of light non-aqueous phase liquid (LNAPL) movement into heterogeneous porous media is important for the effective design of remediation strategies. Numerical simulations are important tools for the understanding of subsurface multi-phase flow and transport processes. The numerical simulator Subsurface Transport Over Multiple Phases (STOMP) was used to simulate two-phase flow in porous media in an unconfined aquifer. The simulations was conducted with the water-oil (w-o) mode of the of the multi-fluid flow simulator STOMP. Two different patterns of layered heterogeneity were used for the simulation of LNAPL movement in an unconfined aquifer. The first pattern (P1: coarse - fine - coarse) showed the maximum LNAPL distribution occurred in the capillary fringe region just above the water table in the fine sand layer region. The second pattern (P2: fine - coarse -fine) showed the LNAPL spreading just above the capillary fringe region not even reaching the capillary zone. The main controlling factor determining the final LNAPL movement and distribution in the layered heterogeneous pattern (P1: coarse - fine - coarse) and (P2: fine -coarse - fine) was capillary pressure and permeability of the media present.