APPLICABILITY OF SHARP-INTERFACE MODELS FOR NAPL TRANSPORT .1. INFILTRATION

A sharp-interface, or piston flow model is developed for nonaqueous phase liquids (NAPL) flow through the unsaturated zone. This model, which assumes saturated plug flow downward from the surface, is verified through comparison with an immiscible-phase model that includes capillarity effects in the formulation. Although significant assumptions are included in the sharp-interface model, it may be useful for initial screening and in obtaining an order-of-magnitude estimate of the time of travel of NA-PL in the unsaturated zone. In the absence of data for calibration, guidelines are introduced for estimating the model's parameters.