BEN SCHOEMAN DOCK BERTH DEEPENING Specialist ... - Transnet

SS mg/l
Boxplot for TSS
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60
40
20
0
BSB
BST
DDB
Figure 8: Suspended sediment (SS) concentrations measured in the Port of Cape Town
at ~4 monthly intervals from September 2005 to September 2006. The measurement
sites were Ben Schoeman Dock (BS), Duncan Dock (DD), the synchro-lift area of the
Victoria/Alfred Basin (VA) and the entrance to the Royal cape Yacht Club (YC), Samples
were taken from the surface (T) and bottom (B) of the water column. The data were
provided by CSIR, Stellenbosch.
DDT
Sample
VAB
VAS
YCB
YCT
5.2.2.2 Nutrients and eutrophication
Inorganic nutrient concentrations within the Port of Cape Town are mediated by water
volume exchanges with the greater Table Bay area and stormwater supplies (CMS
1995b). Median concentration values (Table 9) are largely similar to those expected for
Table Bay (e.g. Chapman and Shannon 1985) but, as pointed out by CMS (1995b) mask
point sources of nitrate- and ammonium-nitrogen within the harbour. The former includes
stormwater flows into Duncan Dock, the repository of all city bowl stormwater, and the
latter this source, and various operations in the Alfred Basin including the synchro-lift,
fish factories and previous oil storage sites (CMS 1995b).
Table 9: Median concentrations (µM/l) of inorganic nutrients in Cape Town harbour in
July and August 1994 (from CMS 1995b)
Entrance Alfred Basin Victoria Basin Duncan Dock Ben
Schoeman
Dock
July
NH 4 +NH 3 7.00 10.78 7.45 7.20 6.58
PO 4 1.80 1.86 1.99 1.60 1.78
NO 3 19.19 17.56 19.33 16.87 18.33
August
NH 4 +NH 3 1.52 6.64 4.58 4.06 3.65
PO 4 0.93 1.20 1.30 1.08 1.30
NO 3 8.79 13.11 12.00 11.74 12.28
Table 9 shows that higher ammonium-nitrogen concentrations occur in the Alfred Basin
but that phosphate-phosphorus and nitrate-nitrogen are more equally spread throughout
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