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Development of a Systematic Methodology for Optimally Designing Vegetative Systems for Remediating Contaminated Soil and Ground Water

Principal Investigators
J.C. Tracy, T.J. Van Lent, and V.R. Schaefer, South Dakota State University


Goal: The goal of this project is to develop a systematic approach to the design and management of vegetative remediation schemes and to implement this approach in a decision support system that can be used by environmental professionals to evaluate the potential use of vegetative systems for remediating a contaminated site.

Rationale: Several previous and current research projects have investigated the potential for vegetation to aid in remediation of soils and ground water that are contaminated near the soil surface. One of these projects produced models that can predict the fate of hazardous organic substances in the root zone of a soil. Preliminary comparisons between developed models and laboratory experiments were favorable, yet two significant modeling limitations were observed. First, the models could only simulate a limited number of contaminant degradation processes. Second, the models require a large amount of information about a site where vegetation is being considered as a remediation option. These limitations could prevent use of the models in predicting potential benefits of a vegetative remediation system designed by environmental professionals involved in soil and ground water remediation projects. To overcome these limitations requires development of a methodology that can synthesize the required modeling data from information that is available about a remediation site and use the model to systematically arrive at an efficient remediation design.

Approach: Objectives of this project related to the efficient design of vegetative remediation systems will be achieved by developing a general methodology based on systems theory. This involves forming a systems statement that includes the quantitative definition of goals of the remediation project, design variables that can be manipulated to attain these goals, and practical and legal constraints that limit attainment of these goals. Several conventional and heuristic solution procedures will be used to solve the systems statement. The most robust and computationally efficient procedures will be selected for continued use in this project. Once developed, the design procedure will be applied to a field site within U.S. EPA Regions VII and VIII that has near surface soils and ground water contaminated with hazardous organic substances. Then a graphically-based decision support system will be developed from this design experience for future use by environmental professionals.

Status: Anaerobic degradation is a significant element in degradation of TCE and TCA; hence, the models must provide a mechanism to simulate anaerobic degradation of contaminants to produce valid simulations. To this end, the model is being modified to include anaerobic degradation processes which are used when the simulated dissolved oxygen content of the soil water drops to near zero conditions. To allow for easier future model modification and use of site-specific degradation simulations, the current computer code is being reworked into a more efficient object-oriented programming style. It has been decided that an attempt to design a vegetative remediation system at the Riley County Landfill will be undertaken. An initial planting of alfalfa has taken place. Exploration and evaluation of alternative algorithms for solving complex optimization problems has begun. This project is in its first year.

Clients/Users: This project will be of interest to government agencies, such as the U.S. Department of Defense and U.S. Department of Energy, and to industry.

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