Potential contamination of groundwater from Cu, Pb, and Zn in wet detention ponds receiving highway runoff

Abstract

Heavy metals (Cu, Pb, Zn) in highway runoff entering detention ponds are removed by physical, chemical and biological processes, and concentrate in the bottom sediments. Soluble metal fractions percolate into the bottom sediments and produce a potential for contamination of groundwater. Therefore, a two-year research project was supported by Florida Department of Transportation (FDOT) and Federal Highway Administration (FHWA) to study the fate and migration of those metals in bottom sediments of six wet detention ponds, located in Florida. Sorption, molecular dispersion, and pilot studies were conducted from these ponds. The results showed that the flow of metals through the bottom sediments is a very slow process. Most of these metals are retained in the top 15-20 cm of sediments and saturation of this layer may take years. Removal of accumulated bottom sediments at time intervals averaging 25 years would be sufficient to minimize the potential contamination of groundwater. Also existing models were modified to simulate metal transport through the bottom sediments in wet detention ponds.