BEN SCHOEMAN DOCK BERTH DEEPENING Specialist ... - Transnet

system
Impact Assessment Table
No
Mitigation
Mitigation
Regional
2
Medium
2
Extent Intensity Duration Consequence Probability Significance Status Confidence
Regional Medium Longterm
High Probable HIGH -ve Medium
2 2
7
3
Longterm
3
High
7
Improbable MEDIUM -ve Medium
6.2.1.9 The effect of noise from the dredging activities on biological organisms in the
harbour
During dredging operations, noise may have an impact on marine organisms in the
harbour such as benthic invertebrates and fish; seabirds foraging on fish may also be
affected. Noises generated during dredging originate from the dredger's engines,
dredging pumps and the clatter of coarse material passing through suction pipes and
depositing in the dredger hoppers. Marine invertebrates have been shown to be
relatively insensitive to low frequency sound whilst fish appear able to accommodate
moderate sound levels (Keevin and Hempen 1997). Foraging seabirds such as
cormorants may avoid the sound source should it reach levels sufficient to cause
discomfort but these birds do not appear to be common in the Ben Schoeman Dock
Basin although they do occur and forage around the harbour entrance.
Cape Fur Seals do occur in the harbour but seem to be habituated to ship related
noises. Note that these animals are very mobile and can move out of the area if any
discomfort is generated. The effects of dredger generated noise would therefore appear
to be negligible. The potential impact is assessed as:
Nature of impact – Noise from the dredging activity may disturb marine invertebrates,
fish, seabirds or mammals
Extent – Local
Duration – Short-term potential effects extend over the duration of the dredging activity
Intensity – Low
Probability – Improbable
Status of impact – Negative
Degree of confidence – High
Significance – Insignificant due to low intensity and short duration
Mitigation – Not considered to be necessary due to the low significance
Impact Assessment Table
No
Mitigation
Extent Intensity Duration Consequence Probability Significance Status Confidence
Local Low Shortterm
Very Low Improbable INSIGNIFICANT -ve High
1 1
3
1
Mitigation n/a n/a n/a n/a n/a n/a n/a n/a
6.2.1.10 Effects of dredging in the Ben Schoeman Dock Basin on endangered seabirds
The endangered or threatened seabirds that may occur in the Ben Schoeman Dock
Basin are African penguins, crowned and cape cormorants. Of these only the latter has
been seen in the respective area with most observations of the birds being towards the
harbour entrance where they actively pursue prey as opposed to roosting on harbour
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