3.6.6 Summary. In this discussion we have pointed out in detail the factors that a miner must take into account in selecting a potential mine site and in determining the productive area(s) contained within the boundaries of such a site. Before summing up conclusions based upon these factors, it must again be emphasized that the choice of site and size is a function not only of the physical characteristics of the site, the mining equipment and the processing equipment, but also of the commercial planning of the miner with respect to production rates and term and products to be extracted. The commercial concept of mine site size has often been equated to some proposed legislative "block" size. Mine site size is a product of commercial value judgment. For one miner a half "block" may be sufficient; for another miner five "blocks" are required. "Block" size, on the other hand, is related to the allocation and administration of promising tracts on the floor of the international ocean. Thus, the two terms may interact but cannot be used synonymously without imposing inflexible burdens on commercial enterprise.

It is noted that land mines frequently have a potential of several hundreds of millions of tons of ore. An ocean "block" of 10,000 km2 at a concentration of 2 lbs. per square foot of manganese nodules has a potential of approximately 100,000,000 tons but the availability of this tonnage, as we have shown, is much different than for a land mine.

Our discussion here has to do with the size of mine sites and not directly with the size of "blocks." It is satisfactory to the operator to have a mine site consisting of multiple blocks, provided the conditions for obtaining the blocks are reasonable.

The important thing this study shows is that only a part of the modules on the ocean floor is available to the operator. If the most pessimistic combination of factors (accessibility, dredge efficiency, sweep efficiency, and cutoff grade) is met, then approximately 9% of the nodules in an area could be recovered. If the most optimistic combination shown is met, then approximately 35% could be recovered. If one imagines the very best combination which might be achieved after long and costly engineering development and finding the unique, almost perfect mine site, the expected recovery would be about 58%. In these figures, then, is the essence of the mine site size problem.

The other essential physical feature is, of course,

the concentration of the nodules. We have pointed out in this paper that a most probable concentration is 2 lbs./ft.2.

Finally, the question of the term of production

enters the equation as the remaining vital factor. For the most part, industry would like to think in terms of at least a 40-year mine life.

To illustrate the above, a determination of mine site size is made for a 1-million dry short-ton/year operation with a 40-year life. Other conditions are:

From Figure 20, the required tract size to sustain this operation is about 22,000 km2. (It is noted that the approximate overall nodule collecting efficiency under these conditions is 22%.)

If a 3,000,000-ton operation is contemplated, the required area under these conditions is about 66,000 km2.

In the event the best conditions efficiency of 35% is achieved, the areas drop to 15,500 km2 and 46,400 km2 respectively.

4.

Production Equipment Development/Fabrication

4.1

Definition

Production equipment development/fabrication, in a manganese nodule mining program, is that activity which has as its objective the design, fabrication, installation and test of the equipment, and the development of the techniques,

required to enable economical and dependable removal of the ore from the selected nodule deposit and conversion of that ore to marketable products and includes removal or conversion of ore for the primary purpose of testing equipment or buyer acceptance.

4.2 Activities

Technical and economic planning and equipment development and procurement efforts of the production equipment development/fabrication phase depend heavily on information concerning the ore, the orebody, and its environment derived from the exploration phase effort. The sizing and production rate of the equipment, equipment life determinations, and the design of mining, transportation, and processing systems are highly dependent on the mine site and deposit data derived. The relationship between the durations of the exploration and the production equipment development/fabrication phases must be quite close. The major activities of development, design, test, and evaluation are related to interface with the availability of the critical mine site and deposit data. Likewise, the confirmation of the economic criteria for exploration by mining and processing considerations must be coordinately phased. Not to do so incurs great risks.

The timing of the work of the production equipment phase also depends on the general engineering studies carried on during prospecting and early exploration. The results of prospecting clarify concepts of the nature of the nodule resource and the resulting engineering will, in turn and to an important degree, influence the nature of the deposit sought for exploration. Following from the prospecting data, preliminary engineering determinations will be made of the equipment and technique to work any resulting orebody. Engineering studies, in combination with the early development and test of the mining, processing, and distribution techniques, as well as hardware, would be carried out. Such efforts lead to general concepts and plans that must be particularized to selected orebodies and mine locations depending on the quality of information and the rate at which it is provided during the exploration phase.

Two major time scheduling approaches formulated by one ocean mining developer, which typify the situation, are

designed to assure production equipment phased to and tailored to the exploration data (see Figure 40). The difference between these alternates to the production equipment phase is the degree to which there is simultaneous accomplishment of a number of the required technical and business activities. Other approaches, of course, åre also available and the realism of the selected approach, which will be a recombination of these similar activities, will be highly dependent on the specific successes of the preceding phases of a particular nodule mining program.

For example, a "five-year production equipment" schedule could lead to earliest economic operations. Such a schedule would permit the first full year of production and distribution of product to the market to be completed about 60 months after go-ahead. An important premise is implementation of the comprehensive, say, three-year minimum concentrated prospecting, research, and preliminary equipment development and testing program (General Engineering Studies and Tests Period) which is essentially completed prior to start. Immediately after go-ahead (see Figure 40), verification of the mine site, mining system, processing, marketing, legal/political status and environmental impacts would need to be at a level consistent with the relatively moderate funding requirements of the first few years. Demonstration plant operations will parallel the detailed ore deposit exploration surveys of the exploration phase. Simultaneous with these activities would be the marine equipment final design progressively particularized to the selected deposit and the initial stages of mining equipment fabrication.

During the last months of the second year, demonstration plant operations will have verified the processing plant design based on the nodule composition determined from the completed final evaluation of the mine site, and the resulting information will have been factored into the marine equipment system for receiving the nodules and transporting them to the land-based processing plant.

Such verification and final determination of the commercial and environmental feasibility of the project would overlap commitments made in the second year for the marine equipment and processing plant.

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