The sediments of Bayou Trepagnier, at the western border of the La Branche wetlands, were contaminated with heavy metals in industrial waste water discharged before the Clean Water Act. Our study of the Pb, Cr, Cu, and Zn content of sediments and associated pore waters at 27 sites along the bayou began in June of 1994. At the beginning of this study, cooling water and storm water runoff from the Shell Norco Manufacturing Complex entered the bayou at its headwaters. This effluent was diverted to the Mississippi River in late February of 1995 as required by the EPA. The effluent, which is warm and slightly brackish, counted for only a small fraction of the water feeding the bayou with the major portions being rainwater runoff from the neighboring swamp along with tidal and wind-driven inputs from Lake Pontchartrain. A profile of the conditions of the bayou in 1994, along with updated monthly analyses for metals dissolved in bottom water samples before and since the diversion, will be presented. It appears that the change in water chemistry due to the removal or the plant discharge has not caused a significant release of contaminates currently sequestered in the sediments
