Appendices 5-13 - Nautilus Cares - Nautilus Minerals

2.5 Outfall Configuration and Assumptions
This study focussed on quantifying the dilution of the discharge plume under worst-case
conditions and assumptions. This approach (worst-case input data for the modelling) then
quantifies the worst-case extents of dilution. In practice, the results of mixing are expected to be
better than those presented herein. The outfall pipe extends from the surface to approximately
20-30 m above the mound at the Solwara 1 lease site. At the bottom, the pipe will be split into two
discharge pipes, both pointing vertically upwards. The temperature of the discharge will range
from 5.8 °C to 11.4 °C. The two pipes will be located diagonally opposite at the lower end of the
pump module frame, approximately 7.5m apart. It is anticipated that each pipe will be approx. 6 &
5/8" (170mm) internal diameter (I.D.).
Nominal discharge rate will be of the order of 2002.5 gpm through each pipe (i.e., a total discharge
of 4005 gallons/minute) being 5 parts production water and 1 part surface water.
The following parameters were assumed as input to the model.
• Discharge rate of 2002.5 gpm through each of two pipes
• Discharge salinity is the same as the receiving water salinity
• Discharge water temperature range is 5.8 °C to 11.4 °C
• Receiving water temperature is 3 °C
• Discharge pipe diameter is 170 mm internal diameter
• Discharge pipe facing directly upwards at 1,475m below sea level
• Starting concentration of discharge plume after pre-dilution is set to 833,333,333 PPB (part
per billion or 83.3% return production water).
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