Asphalt is a very inert material that is insoluble in water. However, Asphalt based paving and roofing materials are subject to water runoff from rainfall events. Additionally, bituminous materials are often used to line drinking water reservoirs and in products to line water pipes that supply potable drinking water. Retention ponds are often paved with asphalt to keep liquid industrial waste material from leaching into the soil. Similarly, Asphalt is used to line and cap hazardous waste sites – preventing rainwater from permeating through the hazardous waste and from leaching into groundwater. Research has shown that pollutants in runoff from Asphalt pavements emanate from vehicles that use the pavements, not from the asphalt pavements themselves.