Managing stormwater at sites with contaminated soils or groundwater is challenging because the infiltrated runoff has the potential to transport contaminants in the soil to the groundwater or mobilize contaminants in the groundwater. Stormwater at contaminated sites can be managed by surface capture and treatment, or as infiltration by avoiding contact between runoff and contaminated soils and groundwater. Surface capture includes filtration and sedimentation practices. When considering surface capture and treatment of runoff at contaminated sites, the surface capture treatment system will usually need an impermeable barrier to prevent infiltration and potential mobilization of contaminates in soil or groundwater. When considering stormwater infiltration at contaminated sites, it is essential to develop management options to ensure contaminants are not mobilized. To accomplish this, a project proposer must understand site conditions (e.g. soils, hydrogeology, land use), the nature and extent of contamination (i.e. site conceptual model), and applicable regulations. The following pages provide information on these topics, including case studies and links to additional information and guidance.