EPA's Region 6 Office
Serving: Arkansas, Louisiana, New Mexico, Oklahoma, Texas, and 66 Tribal Nations
The U.S. EPA's BIOPLUME III model was applied to simulate the natural attenuation of PCP and naphthalene in groundwater under the processes of advection, dispersion, sorption, and biodegradation.
The modeling process was initiated with the formulation of modeling alternatives, derived from analysis of the site characterization. Within this context, compilation, inspection, and interpretation of available data have resulted in a conceptual model of the groundwater system.
Calibration started with the design of the model grid and the preparation of an input file by assigning initial and boundary conditions and other data pertinent to the execution of the BIOPLUME III computer code. Model runs were initiated, followed by interpretation of simulation results and comparison with observed data. The results of these simulations are used to further improve the concepts of the groundwater system and the values of the hydraulic and biodegradation parameters. Sensitivity runs were performed to assist in the calibration procedure.
After the calibration had been concluded satisfactorily, the calibrated model was used to predict the future groundwater flow and contaminant transport.
Because the calibration process for the ground water model showed the plumes to be essentially in steady state and has been so for 30 years, for any period going forward, the plume configuration is stable. PCP and naphthalene contamination will continue to be limited to within an approximate 185 feet travel distance outside of the remaining source areas, while all other PAHs will be essentially stationary. Contamination will not enter the Bayou in the future, much less extend to off site receptors.