Dredging involves the periodic removal of accumulated bottom sediments from waterways. In the Great Lakes this is usually done to maintain adequate water depths for safe and efficient navigation of vessels. Dredging is done also to enlarge or deepen existing navigation channels and recreational harbors. The U.S. Army Corps of Engineers (the Corps) is authorized to maintain more than 130 navigation-related projects in the Great Lakes, nearly all of them commercial and recreational harbors and navigation channels. Many of these projects require periodic dredging. Sometimes dredging is also necessary for waterfront construction, utilities placement and cleanup of contaminated sediments. Much of Great Lakes dredging is undertaken in response to soil erosion and sedimentation from rivers and streams. Efforts to control soil erosion and sedimentation from land uses around the Great Lakes are on the rise and may help reduce overall dredging needs. Beneficial use is the use of dredged material as a resource instead of disposing of it as a waste.