Atwood, D. F. & Gorelick S. M. (1985). "Hydraulic gradient control for groundwater contaminant removal." Journal of Hydrology, 76. 85 - 106.
The article addresses the problem of contaminant ground water plume and proposes a two stage planning procedure to select the best wells and schedules to contain the contaminant plume, while a second system of wells removes the contaminated water. The study contemplates the use of linear programming, groundwater flow and solute transport simulation.
The study case is located in Rocky Mountain Arsenal near Denver, Colorado. The contaminated ground water is result of military and industrial uses. The groundwater modeling was based in previous studies (Konikow, 1975, 1977, and Trescott et. al. 1976), which considered the two-dimensional flow in a heterogeneous isotropic aquifer. The solute transport was combined with groundwater simulation flow, based on the advection-dispersion equation. The objective of the modeling was to compute the field velocity in order to locate the plume boundary relative to the potential gradient control wells.
The stage II of the procedure is select best wells and rates of pumping/recharge, which was done by a linear programming approach combined with ground water flow simulation. The optimization framework minimizes the total pumping/recharge over time subject to hydraulic constraints that force the gradient to be toward the center contaminant removal well. The objective function and constraints are:
where [R] = matrix of gradient response coefficients at gradient check locations; {u} pumpage vector; uc = pumping rate at central removal well; {v} = recharge vector; {e}T= row vector of 1’s; and {g} = known right-hand-side vector reflecting the target gradients.
The main important results are the developed of a procedure for aquifer restoration. The procedure is general and can be applied in other situations. The author outlines two methodologies contributions: “the manner in which the problem is linearized and the extension of the concept of drawdown responses to hydraulic gradients responses”. The linearization was possible due the division of the problem into two parts.
Marcio
ResponderExcluirMy concern is with the frequency of dilution during the cleanup. It would be understandable if the plume was diluted after 75% or 80% removal. I don't know how the procedure was carried out or for how long.
Still, I know that it's unrealistic to think that 100% of the contaminant will be removed. With our present technology, there will be residual. At best, what we should aim for is that the concentration of the residual won't be detrimental to human health or to that of the local ecosystem.