DENSE NONAQUEOUS PHASE LIQUID MIGRATION IN A COMPLEX MULTI-AQUIFER SYSTEM

D.B. Stephens, M. Piepho, J.A. Kelsey, M.A. Prieksat, and M.D. Ankeny, Daniel B. Stephens & Associates, Inc., 6020 Academy Road NE, Suite 100, Albuquerque, NM, 87109


ABSTRACT A laboratory experiment was conducted to demonstrate the behavior of dense nonaqueous phase liquid (DNAPL) 1,1,1-trichloroethane (TCA) in a complex aquifer system. The system simulated consists of two unconfined aquifers separated by a low permeable bedrock perching layer that contains a fracture. In contrast to previous work by other researchers of DNAPL migration in hydrostatic conditions, in this experiment, prior to and during the DNAPL release, ground water flow occurs from the upper to lower aquifer via the fracture. Although the experiment illustrates that DNAPL may migrate rapidly in narrow pathways, the observations were predicted rather well by a simplified analytical solution and a numerical simulation with the multi-phase flow and transport code TOUGH-2. With recharge to the lower aquifer occurring through the fracture, a DNAPL pool did not develop prior to its entry into the fracture.

KEYWORDS: nonaqueous phase liquids, transport modeling


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