A modeling and experimental study of light nonaqueous phase liquid (LNAPL)accumulation in wells and LNAPL recovery from wells

A formulation is presented for numerical modeling of light nonaqueous phase liquid (LNAPL) accumulation in observation wells and LNAPL removal from re covery wells. The formulation includes fluid gravity segregation, changing water and LNAPL levels in the well, and the corresponding changes in fluid storage in the well bore. The method was added to a three-dimensional finit e difference model for hysteretic multiphase flow. The model predictions ar e compared to three-dimensional pilot scale experiments of LNAPL infiltrati on and recovery. Model predictions matched experimental results well, demon strating the validity of the model formulation. Model results indicated tha t soil layering and lack of mechanical equilibrium had a significant influe nce on LNAPL thicknesses in wells. Thus empirical approaches based on assum ptions of soil homogeneity and mechanical equilibrium would not have been a ppropriate for prediction of LNAPL volume from toluene thicknesses measured in wells.