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Polychlorinated dibenzo-p-dioxins and dibenzofurans (dioxin) are extremely persistent in the environment, and can affect human health at low concentrations for many years. As a result of dioxin found in fish and crab tissue, a seafood consumption advisory was issued by the Texas
Department of Health in September 1990 for the upper portion of Galveston Bay and the Houston Ship Channel System (HSC) in Texas. Subsequently, the HSC system was placed on the §303(d) list and a Total Maximum Daily Load (TMDL) study was initiated. Due to the complexity of the HSC system
hydrodynamics coupled with the complicated nature of dioxins, sophisticated modeling was desired to assess sources and transport of contaminants and to develop load allocations. This paper presents the results of a two-dimensional coupled hydrodynamic-water quality model developed to calculate
load allocations and to predict the response of the system to various loading scenarios. The hydrodynamics of the Houston Ship Channel System were modeled using the RMA2 WES 4.5 Program in a two-dimensional mode. The hydrodynamics were coupled to a water quality model for the channel developed
using the U.S. EPA Water Quality Analysis Simulation Program (WASP7). The WASP7 model was applied using both surface water and benthic layers. Long-term average concentrations of dioxin in water were used to determine load allocations on a water quality segment basis. Preliminary model results
indicate that contaminated bottom sediment is the major contributor of dioxin to the water column (≥80%), while industrial and municipal effluents contribute less than 5% to the load in the system. Results also indicate that some segments of the HSC might act as a “reservoirs”
for dioxin mass and that contamination is expected to persist for a long time. A summary of the model calibration and load scenario runs will be presented along with the load allocations.
Proceedings of the Water Environment Federation is an archive of papers published in the proceedings of the annual Water Environment Federation® Technical Exhibition and Conference (WEFTEC® ) and specialty conferences held since the year 2000. These proceedings are not peer reviewed. WEF Members: Sign in (right panel) with your IngentaConnect user name and password to receive complimentary access.