When it rains, stormwater flows across the ground, such as parking lots and roads, and picks up contaminants along the way by washing it off of these surfaces. These contaminants enter the stormwater system through catchbasins, ditches or by flowing directly into stormwater management ponds, creeks and rivers. Catchbasins are the metal grates that are installed to be flush with the ground surface in low points along the curbline of roads and on parking lots. Common contaminants include oils and lubricants, detergents, food waste, degreasers and other hazardous materials that are not stored or disposed of properly.