Appendices 5-13 - Nautilus Cares - Nautilus Minerals

1 Introduction
This report presents the results of numerical modelling of underwater sound levels from a
proposed deep-sea mining operation in the Bismarck Sea (see Figure 1), and a discussion
of the likely impacts of these levels on any marine mammals in the area.
Although there would be a variety of sound sources involved in such an operation, the
most significant are likely to be the cavitation noise produced by the thrusters on the
surface vessel, and noise produced by the subsea mining machine as it grinds the rock
face. Cavitation noise is well understood and therefore predictable with a reasonable
degree of confidence, and forms the focus of this report.
Conversely, the subsea mining machine is a unique device being constructed specifically
for this operation. It is likely to produce an acoustic spectrum with prominent peaks in a
harmonic series based on the frequency corresponding to the rate at which cutting teeth
strike the rock face. However, the likely acoustic source level, and the rate of decay of
the spectrum with frequency are unknown, and the uniqueness of the device means that
any estimates of these parameters will have such large uncertainties that they are of no
practical use. Consequently, the likely effects of noise produced by the machine have not
been quantified.
5