BEN SCHOEMAN DOCK BERTH DEEPENING Specialist ... - Transnet

6 IMPACT IDENTIFICATION AND ASSESSMENT
6.1 Impact evaluation criteria
In the marine environment a disturbance can be relatively short-lived (e.g. accidental
spill of toxic material which is diluted in the water column below threshold limits within
days) but the effect of such a disturbance may have a much longer lifetime (e.g. the
toxin affects the gills of fish and thus reduces their survival chances). The assessments
and rating procedures below address the effects and consequences rather than the
cause or initial disturbance alone. In this report, the word impact thus describes the
disturbance and the effect(s) this disturbance may have on the environment.
Van Ballegooyen et al. (2006) used a simulation modelling approach to predict the
behaviour and distributions of suspended sediments, associated contaminants and
discharged sediments associated with the proposed dredging of the Ben Schoeman
Dock basin. The approach used in this assessment has been to select the apparent
worst case scenarios and to evaluate the associated ecological impacts. The approach
is thus essentially conservative.
In this assessment the protocol specified by SRK Consulting which is described below
has been followed.
The significance of the predicted potential impacts is described as:
Insignificant: The potential impact is negligible and will not have an influence
on the decision regarding the proposed activity;
Very Low:
The potential impact is very small and should not have any
meaningful influence on the decision regarding the proposed activity;
Low:
The potential impact may not have any meaningful influence on
the decision regarding the proposed activity;
Medium:
Where the impact could have an influence on the environment that
should influence the decision regarding the proposed activity;
High:
Where the impact is such that it will affect a decision regarding
the proposed activity: or
Very High: Where the impact could have a 'no-go' implication (for example, if
the predicted impact exceeded legislated limits) and would require modification of the
project design or alternative mitigation to reduce the impacts to acceptable levels, if at all
possible.
The assessment of impact significance is based on:
Nature of impact: This reviews the type of effect that a proposed activity may exert
on the environment including the assessment of 'what would be affected and how'.
Extent:
This indicates whether the impact is local and limited to the
immediate area (15 yrs).
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