![]() As we will see, hydraulic mining may be used in these deposits as well. Although these terms may be used interchangeably with dredging or dredge mining, you can’t assume that to be true in all cases. I mention this here because you will sometimes hear or read about placer mining or alluvial mining. These alluvial deposits created by glaciation, are also known as placers. Glaciers once covered a significant portion of the Earth’s surface, and the movement of these glaciers created extensive unconsolidated deposits of materials containing not only sand and gravel, but gold, tin, diamonds, and other heavy minerals. Dredging to remove this material has the additional benefit of deepening the channel or harbor, and sometimes that is the primary purpose of dredging, and the recovery of minerals is a secondary benefit… the “icing on the cake,” so to speak! Gravel can be used sometimes in concrete as well as for a variety of other purposes such as architectural and landscaping purposes. The bottom of rivers, lakes, and harbors is often a good source of gravel. Shortly, we will look at how the payload is moved in a little more detail, but for now, let’s talk for a moment about the kinds of materials that are typically recovered with this method, dredging or dredge mining. Simplistically, the dredge is designed to lift these materials of interest from the bottom up into the dredge. We need to add one more condition, and that is: the material of value on the bottom must be unconsolidated, such as sand and gravel, or it must be very soft. Of course, the only reason for floating a dredge is to recover something of value at the bottom of this body of water. ![]() In many cases, this is a natural body of water such as a river or a lake, but in others, it is a manmade pond or small lake. Accordingly, a dredge requires a body of water in which to operate. The Federal Standard Paper provides guidance on using dredged material as a resource to achieve environmental and economic benefits and is intended as a companion piece to the Beneficial Use Planning Manual.A dredge is the principal piece of equipment used in the dredging method and, essentially, a dredge is a boat containing specialized mining and materials handling components. The Role of the Federal Standard in the Beneficial Use of Dredged Material was developed as a guide for USACE Districts, other federal agencies, state agencies, local governments and private interest groups. Disposal or placement must be consistent with sound engineering practices and meet all federal environmental requirements, including those established under the Clean Water Act (CWA) and the Marine Protection, Research, and Sanctuaries Act (MPRSA). ![]() The Federal Standard is defined in USACE regulations as the least costly dredged material disposal or placement alternative (or alternatives) identified by USACE. The National Dredging Team (NDT) recognizes dredged material as a valuable resource that can be used in environmentally beneficial ways. Most of this dredged material could be used in a beneficial manner instead, such as for nourishment of beaches with clean sand or development of wetland habitats. ports, harbors and waterways is disposed of in open water, confined disposal facilities and upland disposal facilities. ![]() Much of the several hundred million cubic meters of sediment dredged each year from U.S. An important goal of managing dredged material is to ensure that the material is used or disposed of in an environmentally sound manner. ![]()
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