standardization of environmental data and information - International ...

Figure 2
The plough-harrow.
1. Results from DISCOL as a basis for further impact
studies
1.1. Assumed mining impacts
Various mining techniques have been developed and some were
tested 9 in the 1970s. However, there was no decision when DISCOL was in
its planning phase as to which type(s) might be used one day. We have
assumed a vehicle carrying a collector at its front end, either towed by the
mining ship or self-propelled, moving on chains. This assumption still seems
to be the most probable. A design that moves the vehicle by two
Archimedes screws and disturbs the sediment in two broad tracks more
than 1 m deep seems to have no future, particularly in view of the
environmental aspects. The vehicle envisaged for mining would move along
the seafloor with a speed of about 1 m per second. This hybrid collector
(combining mechanical and hydrodynamic principles for nodule take-up)
would be 6 m or more in width and would gather nodules from the sediment
surface layer by mechanical means and with the help of water jets 10 . An
unknown percentage of the watery surface sediment, the semi-liquid layer,
would be whirled up and partly entrapped during the collection process
along with the nodules. Deeper sediment layers may be broken up into
lumps, which would be transported in a conveyor-belt collection system.
The vehicle, right behind and supporting the collector, would move with
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