As part of a cooperative research program with the National Oceanic and Atmospheric Administration, the Environmental Protection Agency, and the U.S. Fish and Wildlife Service, the Bureau of Mines contracted for an environmental assessment on onshore waste disposal that is expected to occur with the development of commercial deep seabed mining. Three classes of process and four classes of waste disposal techniques were identified, and five sites were selected as representative of first-generation nodule operations. Each site- process-disposal technique combination was compared against potential effects to determine important characteristics of the rejects and the sites. Regulatory requirements were also considered at each site to identify important issues and their effect on the permitting process. The principal conclusions are (1) uncertainties in the regulatory regimes for hydrometallurgical process tailings, primarily regarding classification as hazardous wastes; (2) slags from nodule processing that are expected to be inert and relatively easy to dispose of at all sites; and (3) additional physical and chemical information on properties of rejects from all processes that will be necessary to predict environmental effects.