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d. The duration of the operations will be different. Whereas pilot
mining will be a short-term process, commercial mining will be a
continuous process.
4.3. Recommendations for future benthic disturbance
experiments
To assess the environmental impact of nodule mining, it is
necessary to increase the scale of the disturbance, so that it resembles the
commercial mining operation to some extent in terms of sediment
resuspension, altitude of discharge and areal coverage. Some suggestions
for this are given below.
4.3.1. Greater sediment discharge
Commercial mining is expected to remove 3 million t of nodules
over about 300 days per year, which is about 10,000 t per day. Since the
nodules are associated with sediment in the ratio of 1:5, about 50,000 t of
sediment is expected to be disturbed every day. In view of this large volume
of sediment, the capacity of the pumps as well as the discharge from the
disturber must be substantially enhanced to increase the volume of
sediment resuspension in the water column in order to assess the effects of
such a large- scale disturbance.
4.3.2. Altitude of sediment discharge
Since the sediment and debris may be discharged at a buffer
expected to be a few hundred metres above the bottom, sediment
discharge in the future experiments should be at a higher altitude to assess
the effects of dispersion of the plume.
4.3.3. Towing pattern
As observed during INDEX, the actual duration of disturbance is only
24% of the total time of each operation, which is highly time-consuming and
less productive. It would be advisable to devise different towing patterns
that would occupy more space and time on the seabed, resulting in more
area coverage and a greater volume of disturbance. A few examples follow.
a. Linear two-directional - The linear pattern could be followed in two
directions along the disturbance site to avoid loss in transit time.
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INTERNATIONAL SEABED AUTHORITY