A Composite Model for Assessing Subsurface Transport of Oily Wastes: Verification and Site Application

S. Panday, Y. S. Wu, P. S. Huyakorn, S. C. Wade, and Z. A. Saleem

A composite numerical model incorporating multiphase flow and transport in the unsaturated and saturated zones has been developed for predicting the subsurface migration of oily wastes and dissolved constituents. The composite simulator consists of three major interconnected computational modules: (1) vertical multiphase flow and transport in the unsaturated zone, (2) areal movement of the free-product lens in the saturated zone, and (3) constituent 3-D transport of dissolved chemical in ambient groundwater. The model accounts for all key transport processes including infiltration and ambient flow of NAPL, entrapment of residual NAPL, adsorption, volatilization, degradation, dissolution of chemical constituents, and advective-dispersive transport. Two examples are present d to demonstrate the model verification and site application. The composite model also can simulate biochemical degradation and chemical reactions that produce transformation products. Simulation results obtained using the composite model are compared with a rigorous numerical solution and field observations of crude oil saturations and plume concentrations of total dissolved organic carbon at a spill site in Minnesota. These comparisons demonstrate the ability of the composite model to provide realistic depiction of field-scale situations in a computationally efficient and cost-effective manner.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California