State of the Bay Report 2010-Final - Anchor Environmental

published by the NOAA. Both lead and copper concentrates are exported from Saldanha Bay and it
was hypothesised that the overall increase of metal concentrations was directly associated with the
export of these metals. Detailed studies examining the origin of the metals present in the Bay
revealed that other metals occurring in Saldanha Bay are mostly of natural origin, except for the area
adjacent to the Multi-purpose Quay where elevated concentrations are associated with ore dust fallout
occurring during loading and unloading activities. Cadmium concentrations have been found to
occur in naturally high concentrations in the organic rich sediments of the near shore zone of the
southern Benguela (including Saldanha Bay area).
The temporal variations in the concentration of iron in sediments around the ore jetty in
Saldanha Bay can be seen in (Figure 6.22). The concentration of iron increased between 1999 and
2004 at sites 14 and 15 which are closest in proximity to and on the downwind side (of the
predominant SE winds) of the multi-purpose terminal. This may have been due to increases in
volumes of ore handled or increases in losses into the sea over this period, or simply reflects
accumulation of iron in the sediments over time. There was a reduction in the concentration of iron
in the sediments at most sites on the Small Bay side of the ore jetty between 2004 and 2010.
Dredging took place at the multi-purpose terminal in 2007 and the removal of iron rich sediment at
site 15 is probably the reason for the dramatic decrease in iron concentration recorded at this
station between 2008 and 2008 sampling. Sediment iron concentration at this site did increase to
the highest levels yet recorded in 2009, but decreased again in 2010 samples.
The concentrations of iron around the ore jetty and multi-purpose terminal in Saldanha Bay
decreased progressively at all sites between 2009 and 2010, which is encouraging and either
indicates a reduction in the input of iron or an improvement in flushing of the sediments in this area.
Transnet has implemented numerous new and improvements to existing dust suppression ion
measures in recent years (SRK 2009, Viljoen et al. 2010). Dust suppression mitigation measures
implemented since mid 2007 include conveyer covers, a moisture management system, chemical
dust suppression, surfacing of roads and improved housekeeping (road sweeper, conveyer belt
cleaning, vacuum system, dust dispersal modeling and monitoring) amongst others. The volume of
ore handled at the bulk terminal has increased from around 4.5 million tons per month during 2007-
2008 to around 6.5 million tons during 2009-2010 (~50% increase), yet the concentration of iron in
the sediments at sites adjacent to the jetty have remained stable or decreased. This does suggest
that the improved dust control methods implemented since 2007 have been successful in reducing
the input to the marine environment. Ongoing monitoring of sediment iron concentration will reveal
if this reduction can be sustained at the anticipated higher volumes of ore handling in the near
future.
Much concern was expressed over the possible contamination of the Bay and Lagoon by
trace metals following the dredge event at Salamander Bay between 2009 and 2010. The trace
metal concentrations in sediment collected from Donkergat and Salamander Bay were determined
during the impact assessment process (Robinson 2010). It was revealed that none of the metals
detected exceeded the ERL value, however the ratios of Cu:Al, Pd:Al and Ni:Al in Salamander Bay
were found to exceed those reported in Big Bay and Langebaan Lagoon in 2008. The 2010 survey
results revealed that both copper and nickel concentrations increased at sites BB29 and LL38
(nearest to Salamander Bay) between 2009 and 2010 (Figure 6.23). Lead concentrations were found
to increase dramatically at LL38, while lead was not detected at BB29. Increases in copper
concentration were noted throughout the Big Bay and it is therefore unlikely that the dredge event
lead to this increase at these sites. Furthermore the Cu:Al ratios at these sites are not elevated in
relation to other sites in Big Bay and Langebaan Lagoon suggesting that the driver of this increase in
Cu concentration may not be anthropogenic.
State of the Bay 2010: Saldanha Bay and Langebaan Lagoon