Assessing and Managing Water Quality Impacts of Urban Stormwater Runoff 1

Considerable controversy exists on the real, significant water quality/beneficial use impacts of urban area and highway stormwater runoff-associated constituents. While this runoff contains a variety of potentially toxic constituents, such as heavy metals and certain organics, at concentrations that could be adverse to aquatic life in the receiving waters for the runoff, a number of studies, including those of the authors, have found that the heavy metals in residential street and highway stormwater runoff are in nontoxic forms. Further, it has been found that while stormwater runoff from many urban areas is toxic to aquatic life, that toxicity is due to pesticides used on residential properties. This paper reviews the work of the authors, and the literature pertinent to the reliable assessment of the water quality significance of heavy metals and other constituents in urban area stormwater runoff that occur at total concentrations that potentially could be adverse to aquatic life and other beneficial uses of the receiving waters. Guidance is provided on an Evaluation Monitoring approach that focuses stormwater runoff monitoring on assessing the real impacts of chemical constituents and pathogen-indicator organisms in runoff waters as they may impact the aquatic life-related beneficial uses of the receiving waters. Also, guidance is provided on the approach that should be used to develop technically valid, cost-effective best management practices (BMPs) to manage real, significant water quality impacts of stormwater runoff-associated constituents.