This chapter illustrated how to present physical systems in mathematical form for the numerical model. This chapter analyzed one-dimensional flow and transport in a saturated confined aquifer contaminated with a TCE spill. Analysis determined that all of the proposed remedial strategies were insufficient. Pumping rates must increase in order for advective transport to overcome dispersive transport in the pump-and-treat scenario. Analysis determined that the bioremediation scenario was unfeasible due to high TCE concentrations.

The example problem presented in this chapter may not be representative of a real world example. The chapter did not address some important factors. First, since the example is one-dimensional, it does not allow for dilution of TCE in the lateral direction. This mixing of neighboring clean groundwater with contaminated groundwater will lower TCE concentrations. Second, the example uses a uniform distribution of TCE at a residual saturation. Real spills can consist of pockets of residual NAPL surrounded by material without residual NAPL. In bioremediation studies, other researchers have used lower aqueous TCE concentrations in the neighborhood of 0.04 mg/L (Semprini, 1993).

Table 5.6.1 presents approximate calculation times required for the simulations using a Gateway computer with a 486DX-33V Intel CPU.

Table 5.6.1 Approximate Computation Times for Various Aquifer Simulations