REVIEW OF THE SOURCES, FATE AND TRANSPORT OF CONTAMINANTS IN ENGINEERED STORMWATER STRUCTURES

The physiographic setting known as the Atlantic Coastal Plain of the Southeast U.S. (seaward of the Fall Zone) has been “replumbed” over the past four decades due to extensive water management installations commonly known as stormwater (SW) ponds – a recent survey has enumerated >30,000 stormwater ponds in eight coastal counties of South Carolina. Stormwater ponds have proliferated because regulatory policy requires creation of artificial volume in the form of dug ponds and lakes that are sized to sequester a given volume of SW that would be shed from the developed property greater than that under pre-development conditions. This SW runoff is also the main vector of contamination into receiving bodies of water. The contamination in water is present in diverse forms – physical (sediment, nanoparticles, other particulate matter, etc.), chemical (nutrients, trace metals, complex organic chemicals, etc.), and biological (pathogens) forms. Their fate in the environment is governed by complex physical and biogeochemical processes, most of which are well understood in theory (sorption, distribution, transformation and transport). However, there are no holistic studies that address water quality specifically in SW ponds – most existing studies focus on a small subset of processes or contaminants. In rural areas there are some remaining depression wetlands (e.g., Carolina Bays) that may serve as natural analogues to artificial SW basins, yet because of high terrestrial forest productivity in this region, relatively permeable soils and sediments, and flat topography, there are few natural freshwater ponds and lakes. Although, in this region where there is a higher water table, SW ponds tend to operate as wet detention basins. The present study reviews the current state-of-knowledge of SW ponds from a hydrological and contaminant fate and transport perspective with an emphasis on information pertaining to the Southeast Atlantic Coastal Plain. In this setting it is not clear what is the water balance impact and the transport and fate of pollutants into and within SW ponds. Given the need for contaminant reductions in final water receiving bodies, pond designs that explicitly include design elements which actively reduce water contamination need to be considered. More integrative studies are needed.