Risk Assessment of Stormwater Contaminants Following Discharge to Soil, Groundwater or Surface Water

Abstract

Stormwater runoff from urban areas is significantly polluted with a wide range of substances of environmental concern, and, the environmental impacts associated with wet-weather discharges have received increased attention during recent years. As a result, there are increasing pressures from society to handle stormwater runoff in ways that ensure maximum pollution reduction. The basic challenge for future risk assessment of stormwater contaminants is to ensure that the methodologies used account for information about the local context and produce information that feeds into local decision making processes. It is essential that sound scientific knowledge about the chemodynarnics and toxicity of chemical substances is considered to ensure a minimum level of transparency, and learning from principles developed for risk assessment of chemical substances best ensures this. In the future we will need tools of varying complexity that can be applied on various spatial scales by acknowledging that stormwater projects are often small, have limited budgets and are dealt with by non-experts in chemical risk assessment. Some useful tools would be as follows: • an identification list of those stormwater constituents which can be specifically classified as contaminants following discharge to surface water, groundwater and/or soil; • a database of physica/chemical properties of these contaminants, their environmental fate and effects, their predicted no-effect concentrations, when available, and their treatability (possible removal in various BMPs); • a tool for estimating concentrations of these stormwater contaminants in a sitespecific context; and • a screening tool for identifying in a site-specific context which stormwater contaminants are critical (priority pollutants) following discharge to surface waters, groundwater and/or soils.