Amended sediment caps are covers placed on top of contaminated sediment in rivers, streams, bays and lakes to keep people and wildlife from being exposed to contaminants. Like conventional caps, amended caps act as barriers between contaminated sediment and overlying clean sediment and water. However, amended caps also contain added materials called “amendments” that treat contamination. Amended sediment caps often are used with other cleanup methods, such as dredging (digging up and disposing of contaminated sediments). They can treat sediment contaminated with organic chemicals, like petroleum products, PCBs, pesticides and solvents, and metals.