State of the Bay Report 2010-Final - Anchor Environmental

Anchor Environmental
with the rest of the dredged material to achieve appropriate dilution and disposed of on land.
Environmental specifications have been published by the National Ports Authority in which the
potential impacts of this maintenance dredging were outlined and recommendations were proposed
for avoiding, minimizing and controlling the impacts (National Ports Authority 2007). The impacts of
the maintenance dredging are summarized above. It is expected that farther maintenance dredging
at the Mossgas and Multi Purpose terminals will not be required for a further 10 – 20 years (Mr
Lyndon Metcalf, pers. comm.). This is due to the fact that the port is situated in a sheltered area and
most loose sediments were removed during harbour construction. The depth of the port further
reduces sediment transport, which might have otherwise fill in navigation channels more rapidly
(Schoonees et al. 1995).
The third of these dredge events was undertaken in 2009/10 and completed in December
2010, during which 7,300 m 3 of material was removed from an area of approximately 3,000 m 2 at
the end of the cause way, between Caisson 3 and 4 on the Saldanha side of ore jetty (Figure 4.8) (N.
Jansen – Port of Saldanha pers. comm. 2011). The environmental impact assessment for the
proposed dredge event was undertaken by Environmental Resources Management in April 2008.
The purpose of the dredging was to increase the export capacity of the iron ore terminal though the
use of a staggered ship loading arrangement, that enables both ship loaders to operate
independently and simultaneously. The dredged material was used to fill the two scour holes
between Caissons 5 and 6. These were revealed, during a bathymetric survey in June 2007, to have
been caused by the scouring currents produced by the propellers of bulkcarriers while berthing and
un-berthing (ERM 2008). A final report of the outcome of the dredging operation is still to be made
available by Ports of Saldanha (N. Jansen – Port of Saldanha pers. comm. 2011).
Figure 4.8. Location of the maintenance dredging site between Caissons 3 and 4 on the ore terminal.
Transnet has also proposed a Phase 2 Expansion of the Iron ore quay in order to increase its
export capacity from, 45 million tonnes/annum to 90 million tonnes/annum. This will require
extensive dredging of soft sediments, powder calcrete, limestone, calcernite/calcretes and the
removal of 90 000 m 3 granite by underwater blasting (PRDW, 2007a, b). The expansion involves the
development of two new berths on the southern side (Big Bay side) of the iron ore quay.
State of the Bay 2010: Saldanha Bay and Langebaan Lagoon 52