During the investigation of possible financial penalties of deep ocean mining pollution mitigation the major threats to the marine environment were identified and means to minimize damage proposed. This paper defines the major threats: the benthic plume of suspended particulate matter comprised of macerated marine biota and disturbed seabed sediments, and the surface plume of ingested benthic matter and abraded manganese nodule. Techniques for minimizing the disturbance of the seabed and limiting ingestion of benthic material in the dredge pipe and means for controlling the surface plume to limit possible damage to the euphotic zone of the water column are developed. The author concludes by recommending that the industry test and the scientific community evaluate the effectiveness of the proposed pollution mitigation approaches.
In mid 1978 the MIT Sea Grant Program published "A Cost Model of Deep Ocean Mining and Associated Regulatory Issues" by J. D. Nyhart, et a1. 1 which was promptly used, and abused, by many of the delegations participating in the United Nations' Law of the Sea Conference to forecast earnings of a hypothetical company in the emerging deep ocean mining industry. Simultaneously, the Office of Marine Minerals of the National Oceanic and Atmospheric Agency (NOAA) was proceeding to plan and scope regulations to control the new industry and to protect the marine environment if they were designated as the responsible government agency by U.S. legislation long under consideration in the Congress. The potential costs (capital and operating) of equipment in the system to protect the environment were not identified or estimated in the model making economic evaluation of possible environmental regulations impossible. Since mid 1978 the author has been investigating these potential costs.
NOAA has also been responsible, since 1972, for an extended environmental effort which developed into the Deep Ocean Mining Environmental Studies (DOMES). The work was done in two distinct phases: a series of "baseline studies" resulting in the accurate definition of the pristine or "before mining" seabed and ocean in the proposed mining area, and a series of data gathering and observation voyages to assess the impact on the marine environment of the industry at-sea mining system tests. The DOMES program workshops and reports2 have provided the basic data for this paper and the above-cited research.
The two successful small scale deep ocean mining system tests completed in 1978 and 1979 and the one currently being conducted are all hydraulic dredging systems. A surface ship provides a working platform used to store and handle a three mile pipeline from the sea surface to the seabed. Either air-lift or submerged in-line pumps provide the dredging lift energy. A seabed collector, or dredge head, is towed across the ocean floor separating the manganese nodules from the sediments and feeding them into the dredge pipe and thence to the mining ship. Environmental concerns focus on the seabed, in the area of the collector, and on the sea surface in the area of the mining ship.
