Remedial efforts at Superfund sites across the country focus on groundwater contaminant plumes that have been produced by contributions from multiple parties. Allocating cleanup costs between the parties in a fair and equitable manner can be a problem of substantial complexity. Considerable time and money may be spent determining the amount of contamination attributable to each party in order to apportion liability. Contaminant plumes that have evolved over long periods of time may affect large volumes of groundwater and require extensive remediation. Pump and treat remedial costs are driven by both the volume of water extracted and the mass of contaminants removed. Allocation methods based solely on the mass of contaminants contributed by each party are inadequate in this setting since they do not account for both components of the remedial costs. This paper presents an approach for equitably allocating remedial costs when addressing overlapping or commingled groundwater plumes. The method accounts for the major elements driving the costs of remediating dispersed contaminant plumes.

}, issn = {1527-5922}, doi = {10.1006/enfo.1999.0006}, url = {http://dx.doi.org/10.1006/enfo.1999.0006}, author = {Marryott, R. A. and Sabadell, D. P. and D. P. Ahlfeld and Harris, R. H. and Pinder, G. F.} } @article {18148, title = {Computer-facilitated groundwater remediation design}, journal = {Technology: A Journal of Science Serving Legistative, Regulatory, and Judicial Systems }, volume = {6}, year = {1999}, month = {01/1999}, pages = {453-473}, chapter = {453}, abstract = {Conflicts about groundwater contamination can be resolved using groundwater modeling and optimization techniques. At Toms River, New Jersey, disagreements among stakeholders regarding the appropriate design of a groundwater remediation strategy were resolved by using optimal-design techniques to demonstrate the infeasibility of designs that required certain physical limitations. Through negotiations in a series of public meetings wherein the results of these analyses were presented, a hydraulic containment design was eventually adopted and implemented by all stakeholders. The question remained, however, as to whether an alternative strategy based on acceptable risk rather than total plume containment would be appropriate. A new approach that permits investigation of this alternative strategy indicates that a design using risk-based constraints could be considerably different from that currently implemented. The analysis also demonstrates the relative cost of considering containment by hydraulic gradient versus risk reduction through mass removal. In the former, environmental risk is minimized by assuring an inward gradient around the plume perimeter. In the latter, the goal is to control risk while removing contaminant mass.

}, issn = {1072-9240}, url = {http://www.ingentaconnect.com/content/cog/tech/1999/00000006/F0030004/art00021}, author = {Karatzas, G. P. and Pinder, G. F. and D. P. Ahlfeld} } @article {18184, title = {Optimal ground-water remediation methods applied to a superfund site: from formulation to implementation}, journal = {Groundwater}, volume = {33}, year = {1995}, month = {01/1995}, pages = {58{\textendash}70}, chapter = {58}, abstract = {A hydraulic control optimization model is applied to the conceptual and implementation analysis of a ground-water remediation system in coastal New Jersey. The site is modeled using a distributed parameter finite-difference model containing 36,000 nodes within five layers. The conceptual problem is to determine the feasibility of producing a capture zone which encompasses the entire existing plume while recharging all extracted water within property boundaries in such a way that the recharged water satisfies criteria on its fate. The conceptual analysis problem is formulated as a linear program in which the total extraction pumping is minimized, and requirements are placed on hydraulic heads and gradients in both horizontal and vertical directions. A requirement is also made that all extracted water be recharged to the subsurface. The model is used for determination of the feasibility of the remediation concept. Details of constructing constraints for a large-scale formulation are presented. The concept of constraint calibration, using particle tracking to insure that constraints are producing desired results, is introduced and demonstrated. The optimization formulation is used for detailed implementation analysis of the remediation system. A number of techniques for modifying elements of the conceptual model results, such as unrealistically small pump rates, are described. The optimization approach is found to be useful for determining the feasibility of the remedial strategy at this site and for producing results which can be used as a starting point for detailed analysis of the remediation strategy.

}, issn = {1745-6584}, doi = {10.1111/j.1745-6584.1995.tb00263.x}, url = {http://dx.doi.org/10.1111/j.1745-6584.1995.tb00263.x}, author = {D. P. Ahlfeld and Page, R. H. and Pinder, G. F.} } @article {18214, title = {A fast and accurate method for solving subsurface contaminant transport problems with a single uncertain parameter}, journal = {Advances in Water Resources}, volume = {15}, year = {1992}, month = {01/1992}, pages = {143-150}, chapter = {143}, abstract = {A new approximate random sampling method is described for numerical solution of the contaminant transport equation where a single uncertain parameter is present. The solution consists of the probability distribution of concentration at any point in space and time as a function of the uncertain parameter. The method is based on a limited sampling of the parameter space and subsequent interpolation of the information obtained at the sample points. This interpolation produces a complete approximation of a function that relates the random parameter and the concentration. The interpolation is performed using Hermite polynomials which require function and derivative information at each sample point. The theory is developed and an example of the computation of the distribution of concentration resulting from the distribution of a single effective conductivity is presented. Numerical results suggest that this method may be one to two orders of magnitude faster than a conventional Monte Carlo approach in solving this stochastic problem while yielding comparable accuracy.

}, keywords = {groundwater, hermite, interpolation, Monte Carlo, simulation modeling, transport, uncertainty}, issn = {0309-1708}, doi = {10.1016/0309-1708(92)90041-Y}, url = {https://doi.org/10.1016/0309-1708(92)90041-Y}, author = {D. P. Ahlfeld and Pinder, G. F.} } @article {18250, title = {Contaminated groundwater remediation design using simulation, optimization, and sensitivity theory: 1. Model development}, journal = {Water Resources Research}, volume = {24}, year = {1988}, month = {03/1988}, pages = {431{\textendash}441}, chapter = {431}, abstract = {The problem of designing contaminated groundwater remediation systems using hydraulic control is addressed. Two nonlinear optimization formulations are proposed which model the design process for the location and pump rates of injection and extraction wells in an aquifer cleanup system. The formulations are designed to find a pumping system which (1) removes the most contaminant over a fixed time period and (2) reduces contaminant concentration to specified levels by the end of a fixed time period at least cost. The formulations employ a two-dimensional Galerkin finite element simulation model of steady state groundwater flow and transient convective-dispersive transport. To make the optimization problems computationally tractable sensitivity theory is used to derive a general relationship for computing the derivatives of an arbitrary function of the simulation outputs with respect to model inputs. This relationship is then applied to the convective-dispersive transport equation.

}, issn = {1944-7973}, doi = {10.1029/WR024i003p00431}, url = {http://dx.doi.org/10.1029/WR024i003p00431}, author = {D. P. Ahlfeld and Mulvey, J. M. and Pinder, G. F. and Wood, P. F.} } @article {18252, title = {Combining physical containment with optimal withdrawal for contaminated groundwater remediation}, journal = {Advances in Water Resources}, volume = {10}, year = {1987}, month = {12/1987}, pages = {200-204}, chapter = {200}, issn = {0309-1708}, doi = {10.1016/0309-1708(87)90029-7}, url = {https://doi.org/10.1016/0309-1708(87)90029-7}, author = {D. P. Ahlfeld and Mulvey, J. M. and Pinder, G. F.} } @article {18256, title = {Designing optimal strategies for contaminated groundwater remediation}, journal = {Advances in Water Resources}, volume = {9}, year = {1986}, month = {06/1986}, pages = {77-84}, chapter = {77}, abstract = {The problem of locating pumps and setting pump rates to most effectively stabilize and remove a plume of contaminated groundwater at a hazardous waste site is examined. Nonlinear optimization methods are combined with convective-disperisve transport simulation in a unit response matrix type of optimization formulation.

Constraints are used which guarantee that the contaminant plume is removed by limiting the concentrations at nodal points in the domain at a future time. Additional constraints explicitly require that concentrations not increase in the area outside the initial plume boundary. The effectiveness of alternative formulations are examined by performing numerical experiments using a hypothetical aquifer.

The experiments show that computational costs are dominated by the repeated simulations required for computation of constraint gradients and are proportional to the number of pump sites under consideration. This characteristic of the formulation and algorithm used, limits the use of the approach to problems where the number of potential pump sites is relatively small.

}, issn = {0309-1708}, doi = {10.1016/0309-1708(86)90013-8}, url = {https://doi.org/10.1016/0309-1708(86)90013-8}, author = {D. P. Ahlfeld and Mulvey, J. M. and Pinder, G. F.} }