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Proposed Deepening, Lengthening and Widening of Berth 203 to 205, Pier 2, DCT, Port of Durban – DEA
Ref: 14/12/16/3/3/2/275
Draft EIA Report i
AMENDED
EIA REPORT
03 June 2014 [NEAS REF NO: DEA/EIA/0000988/2012
DEA REF NO: 14/12/16/3/3/2/275]
Deepening, Lengthening and Widening of Berth 203 to 205, Pier 2, Container Terminal, Port of
Durban
P.O. BOX 1673
SUNNINGHILL
2157
147 Bram Fischer Drive
FERNDALE
2194
Tel: 011 781 1730
Fax: 011 781 1731
Email: [email protected]
Amended EIR - Proposed Deepening, Lengthening and Widening of Berth 203 to 205, Pier 2, DCT, Port of
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EXECUTIVE SUMMARY
Transnet National Port Authority (TNPA) plans to upgrade Berths 203 to 205, Pier 2, Container
Terminal, Port of Durban. Berth 203 to 205 are the key container berths in the Port, however, the
existing Blockwork Quay wall structure along Pier 2 Berth 203 to 205 was designed in the 1970s
to support dockside cranes with the lifting capacity of 4 tonnes. The quay walls are presently
operating beyond their original design limitations. Recent studies have concluded that the existing
quay walls do not meet the minimum Eurocode 7 Safety Standards and that there is a risk of
potential quay wall failure (PRDW, 2011). Vessel sizes have also increased since the original
terminal was constructed and Berth 203 to 205 cannot therefore safely accommodate fully-laden,
new-generation, container vessels due to insufficient water depth at these berths. At present
these vessels enter and exit the Port partially laden and during the high tide window. This creates
an unsafe operating condition and the risk exists that vessels could run aground. TNPA has
proposed the deepening, lengthening and widening of Berth 203 to 205 in order to improve the
safety of the berths as well as to improve the efficiency of the Port.
The proposed upgrade would include the following activities:
The westward lengthening of Berth 205 by 170m;
The eastward lengthening of Berth 203 by 100m;
The seaward widening of Berths 203 to 205 by 50m;
The deepening of the berth channel, approach channel, and vessel turning basin from
the current -12.7m CDP to -16.5m CDP;
Three technical options are to be considered namely, the Caisson option, Sheet Pile
option and Deck on Pile option. In the case of the Caisson option, a trench will need to
be excavated to -19m CDP;
The construction of caissons, storage of sheet piles or precasting of elements of the
Deck on Pile at Bayhead Lot 10;
The offshore disposal of dredge material;
The offshore sand winning for infill material; and
The installation of new Ship to Shore (STS) cranes and associated infrastructure.
Nemai Consulting was appointed by TNPA to undertake the requisite Environmental Authorisation
Process for the Proposed Berth 203 to 205, Pier 2 upgrade. The proposed development
triggers activities listed in Government Notices No. R. 544, R. 545 and R. 546. Hence, a full
Scoping/EIA study, as per the August 2010 Environmental Impact Assessment (EIA)
Regulations promulgated in terms of the National Environmental Management Act, 1998 (Act
No. 107 of 1998) is necessary.
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In addition, a Dumping at Sea Permit as per the National Environmental Management: Integrated
Coastal Management Act, 2008 (Act 24 of 2008), is required to dispose of dredged material at an
offshore disposal site.
A Mining permit for dredging of material offshore for infill purposes will also be required as per the
Mineral and Petroleum Resources Development Act, 2002 (Act No. 22 of 2002).
The final EIA report was submitted to DEA on 5 August 2013. On 21 October 2013 DEA issued a
letter stating that the final EIA report was rejected. DEA requested additional information before a
decision could be taken. There were two main areas which required additional information (Refer
to Appendix A for a copy of the DEA letter dated 05/08/14):
1. Impact on the Central Sandbank; and
2. The Climate Change Study.
The Specialists reviewed existing reports in light of the comments raised by DEA. The following
reports were compiled in response to the DEA letter:
1. Ecological Risk Assessment pertaining to the Estuarine Habitat in Durban Bay by
Extension of the Central Sandbank – Anchor Environmental and CSIR;
2. Feasibility Study (FEL3) for the Deepening of Berths 203 to 205, Port of Durban –
Extension of Sandbank Engineering Risk Assessment Revision D (ZAA
1370/RPT/040REVD) – ZAA Engineering; and
3. Feasibility Study (FEL3) for the Deepening of Berths 203 to 205, Port of Durban – Design
Report – Effects of Climate Change on Engineering Design Revision F
(ZAA/1370/RPT/028REVF).
On 28 February 2014, the revised reports were presented to the Units within DEA that raised their
concerns. Based on the outcome of the meeting, DEA provided additional correspondence
regarding their requirements on 22 April 2014 (Refer to Appendix A for a copy of the DEA letter
dated 22/04/14).
The aforementioned studies were updated with the latest comments from DEA. The final reports
are contained in Appendix B1-3 and are summarised in Chapter 5 of this report. The findings of
this study have been used to deal with all the comments raised by the DEA. The letters from
DEA, Specialist Studies and the Additional Information Report is available for public review from 2
June 2014 to 2 July 2014 (30 days) to allow all I&APs to provide comments.
The Ecological Risk Assessment Report (Anchor Environmental and CSIR, 2014), concluded that
given the long term engineering stability of the proposed new sandbank habitat, initial
colonisation, succession and the establishment of an ecologically functioning benthic community
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is certain. Further, given the proximity of this sandbank to the existing Central Sandbank and its
similarity in terms of structure, granulometry and hydrodynamic characteristics, it is highly likely
that a similar biological community will develop. Minor differences should be expected and will
probably beneficially increase benthic diversity in the Bay. Successful establishment of benthic
biota will result in profitable utilisation of the created habitat by higher trophic level organisms (fish
and birds). Fish especially will benefit from the creation of additional shallow intertidal and
subtidal habitat. These habitats are the primary feeding areas for juvenile estuarine dependent
species utilising Durban Bay as a nursery. Shallow subtidal area is especially important. The
present configuration and bathymetry of Durban Bay, with a strong predominance of deep water
habitat or intertidal habitat, and limited shallow subtidal habitat, reduces its value as a fish
nursery. Shallow water offers juvenile fishes protection from predation by piscivorous fishes
(Blaber 1987, Ruiz et al. 1993). Such habitat is limited in Durban Bay at low tide, leaving juvenile
fishes susceptible to predation. The proposed sandbank extension results in significant increases
in these shallow water habitats and will fulfil an ecological role that is congruent with the Bay’s
ecological value as an estuarine embayment. Indeed in the long term it will improve the systems
ecological value.
The Extension of Sandbank Engineering Risk Assessment report (ZAA Engineering, 2014a)
summarised the work that has been carried out as part of the FEL‐3 study and has addressed in
particular the engineering issues, with respect to the extension of the central sandbank, raised by
the Department of Environmental Affairs in its letter Ref 14/12/16/3/3/2/275 signed on 21 October
2013 and issued in response to the initial EIA Report, by means of the following:
A comprehensive Risk and Mitigation Analysis covering both the construction of the
extension and the maintenance of the sandbank during the operational phase of the new
container terminal at Pier
Development of a Method Statement for the construction of the sandbank
Hydrodynamic and morphological analyses of the Port of Durban using DELFT‐3D to
determine the short and long term stability and form of the extended sandbank, including
the effects of wave penetration, wind and currents due to tidal movements and other
effects. These studies indicate that the extended sandbank will be stable and that it will
not endanger the stability of the existing sandbank during construction, or during
operation of the container terminal. It also indicates that flows will not change in the area
of the Little Lagoon and this, combined with the sheet pile protection to be installed, will
ensure that the Little Lagoon is not disturbed.
Hydrodynamic analyses have been carried out to assess the levels of turbidity and total
suspended solids (TSS) that will result from the dredging operations and the studies
have confirmed that levels will be within acceptable limits.
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Geotechnical finite element analyses have been carried out using the computer
programme PLAXIS to ensure the stability of the sandbank extension.
An extensive on site geotechnical investigation (involving Cone Penetrometer Testing
with pore water pressure data (CPTu) and proof drilling and logging) has been carried
out to determine the nature and suitability of the sands that will be dredged from the
basin, for use in the construction of the sandbank extension.
Comprehensive dredging analysis and design has been carried out.
This report showed that all risks were mitigated to a ‘’minor’ impact.
The Effects of Climate Change on Engineering Design Report (ZAA, 2014b) reviewed and
summarised available literature on parameters affected by climate change that are relevant to the
marine engineering design for this project. The IPCC, (2013) Climate Change 2013, has been
adopted as the primary reference for this report. This is in agreement with IPCC AR4 (2007),
together with the scaled up ice sheet discharge allowance, projected from 2095 to 2100. This has
been supplemented by guidelines produced by UK Climate Projections Report June 2009
(UKCP09) and the National Committee on Coastal and Ocean Engineering, Engineers Australia.
The parameters listed below are those that can be affected by climate change and are relevant to
the marine engineering design. These parameters have been taken into consideration in the
design of the proposed quays and associated dredging works:
Long term sea level rise
Storm surge (wind setup, pressure deficit, wave setup)
Temperature
Wind (including tropical cyclones)
Currents
Waves
Rainfall
Ocean acidification
The study demonstrates that the chosen cope level of +4.25m CDP is sufficient, providing a
freeboard of 0.324m over and above the allowed for accumulation of various upper bound
increases for climate change affected parameters.
The risks and vulnerability of the new quays to climate change, and in particular sea level rise and
storm surge, have been minimised and that the selected cope height of 4.25 m originally
proposed by Transnet for this project is safe, conservative for its design life of 50 years from the
projected completion date of 2019 and that a safe freeboard will still exist. In fact, given the year
2100 projection values, the structure is likely to be safe for a further 32 years after 2069. In all
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cases this is in the event of the simultaneous occurrence of all factors affecting the water level in
the Port.
Various improbable extreme scenarios (e.g. UKCP09 H++) have been taken into account when
evaluating the design in terms of contingency planning in the event of these extreme scenarios.
Other climate change affected parameters such as wind, rainfall and ocean acidification have
been taken account during the design of the quay structures, storm water system and concrete
specification.
The threat of flooding during the construction phase has been evaluated and we conclude that
construction will not adversely affect the current levels or increase the risk or vulnerability to
flooding.
Based on the additional risk and vulnerability assessment studies undertaken to address DEA’s
comments, the Central Sandbank Extension is deemed a rational and acceptable mitigation
measure that has a high likelihood of success in terms of colonisation and succession. In terms of
engineering design, DELFT-3D models have shown that the Sandbank Extension is stable and
will require no long term maintenance. Mitigation measures have been provided in this Annexure
as well as the monitoring protocol required to determine the baseline thresholds. The Sandbank
Extension has a very low likelihood of failure, however should this happen, the ecological
implications would be similar to the original Option 3C dredge footprint (5.6% loss of habitat and
associated loss of functioning). The biggest socio-economic impact of this loss would be related
to recreational and subsistence fishing (due to the loss of nursery habitat). However, it should be
noted that the Central Sandbank Extension will increase nursery habitat and thus will have a
positive socio-economic impact in this regard.
In regards to Climate Change, risk and vulnerabilities of the Port to changes in Climate have been
taken into account through the engineering design.
Thus, with the selection of the quay wall alternatives, dredge footprint and offshore sand winning
site, the adoption of the mitigation measures included in the Amended EIA Report and original
EIA report and the dedicated implementation of the suite of EMPrs, it is believed that the
significant environmental aspects and impact associated with this project can be suitably
mitigated. With the aforementioned in mind, it can be concluded that there are no fatal flaws
associated with the project and that authorisation can be issued, based on the findings of the
specialists and the impact assessment, through the compliance with the identified environmental
management provisions.
The extension of the Central Sandbank will be monitored over a period of 5 years from the day
the extension is created. Any deviations will be discussed with an Environmental Monitoring
Committee. Should the extension of the sandbank not meet 80% of the baseline conditions then
offset measures will be considered in consultation with DEA.
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TITLE AND APPROVAL PAGE
Project name: Proposed Deepening, Lengthening and Widening of Berth 203 to 205,
Pier 2, Container Terminal, Port of Durban
Report Title: Proposed Deepening, Lengthening and Widening of Berth 203 to 205,
Pier 2, Container Terminal, Port of Durban – Amended EIA Report
Authors: D Naidoo, Vanessa Stippel (nee Brueton), Donavan Henning and R
Maharaj
Additional Specialists: Dr B Clark, Dr. S Weerts and Dr J Zietsman
Authority reference No.: NEAS REF NO: DEA/EIA/0000988/2012, DEA REF NO:
14/12/16/3/3/2/275
Status of report: Draft
Date of issue: 03 June 2014
Prepared By: Nemai Consulting
Client: Transnet National Ports Authority
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AMENDMENT PAGE
Date Nature of Amendment Amendment No. Signature
June 2014 Draft for Public Review 1
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TABLE OF CONTENTS
EXECUTIVE SUMMARY .............................................................................................................. ii
TITLE AND APPROVAL PAGE ................................................................................................. vii
AMENDMENT PAGE ................................................................................................................. viii
TABLE OF CONTENTS .............................................................................................................. ix
LIST OF TABLES ........................................................................................................................ xi
LIST OF FIGURES ...................................................................................................................... xi
LIST OF APPENDICES ............................................................................................................. xiii
LIST OF ACRONYMS AND ABBREVIATIONS ......................................................................... xiv
DEFINITIONS OF KEY TERMS ................................................................................................. xvi
1 PURPOSE OF THIS DOCUMENT ......................................................................................... 19
2 DOCUMENT ROADMAP ....................................................................................................... 20
3 PROJECT MILESTONES ...................................................................................................... 25
4 SUMMARY OF ADDITIONAL SPECIALIST STUDIES .......................................................... 26
4.1 Comments from DEA ............................................................................................................. 26
4.2 Ecological Risk Assessment pertaining to the Estuarine Habitat in Durban Bay by Extension of
the Central Sandbank – CSIR and Anchor Environmental ....................................................... 29
4.2.1 Specialist ................................................................................................................... 29
4.2.2 Main Findings ............................................................................................................ 30
4.3 Feasibility Study (FEL3) for the Deepening of Berths 203 to 205, Port of Durban – Extension of
Sandbank Engineering Risk Assessment (ZAA1370/RPT/040REVD) – ZAA Engineering ....... 35
4.3.1 Specialist ................................................................................................................... 35
4.3.2 Main Findings ............................................................................................................ 36
4.4 ..... Feasibility Study (FEL3) for the Deepening of Berths 203 to 205, Port of Durban – Effects of
Climate Change on Engineering Design (ZAA1370/RPT/028REVF) – ZAA Engineering ......... 51
4.4.1 Specialist ................................................................................................................... 51
4.4.2 Main Findings ............................................................................................................ 51
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5 SUMMARY OF RESPONSES PROVIDED ............................................................................ 63
5.1 Central Sandbank .................................................................................................................. 63
5.2 Climate Change Issues .......................................................................................................... 75
5.3 Re-use of Dredge Material ..................................................................................................... 79
5.4 Alien Invasive Species ........................................................................................................... 81
5.5 Stability of the Sandbanks ...................................................................................................... 81
5.6 Mitigation Measures and Monitoring ....................................................................................... 82
6 SUMMARY OF ADDITIONAL MITIGATION MEASURES ..................................................... 96
6.1 Central Sandbank .................................................................................................................. 96
6.1.1 Management and Minimization of Habitat Loss ......................................................... 96
6.1.2 Management of Central Sandbank* ........................................................................... 97
6.1.3 Management of Central Sandbank Dredging ............................................................. 98
6.1.4 Management of Central Sandbank Extension .......................................................... 100
6.1.5 Management of stabilization of the toe of the Extended Sandbank .......................... 101
6.1.6 Offset Plan .............................................................................................................. 101
6.2 Avifauna ............................................................................................................................... 101
6.3 Dredging and Dredge Disposal ............................................................................................ 102
6.3.1 Management of Dredger .......................................................................................... 102
6.3.2 Management of Turbidity ......................................................................................... 102
6.3.3 Management of Transportation of Dredge Spoil to Disposal site ............................. 103
6.3.4 Management of Disposal of Dredge Spoil at the Disposal Site ................................ 104
6.3.5 Management of Ballast Water ................................................................................. 105
6.4 Climate Change ................................................................................................................... 105
6.4.1 Climate Change Adaptation ..................................................................................... 105
6.4.2 Climate Change Mitigation ...................................................................................... 106
6.5 Little Lagoon ........................................................................................................................ 108
6.5.1 Management of Fencing and Restricted Access of Sensitive Environmental Features
108
6.5.2 Management of Little Lagoon .................................................................................. 108
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6.5.3 Management of Turbidity at the Little Lagoon .......................................................... 108
6.6 Monitoring to Mitigate Impacts of Turbidity ........................................................................... 109
7 AMENDED EIA REPORT CONCLUSIONS AND RECOMMENDATIONS ........................... 114
7.1 Best Practicable Environmental Option (BPEO) ................................................................... 114
7.2 Environmental Impact Statement ......................................................................................... 116
7.3 Amended EIA Report Recommendations ............................................................................. 122
8 REFERENCES ..................................................................................................................... 123
LIST OF TABLES
Table 1: Locations for review of Draft EIA Report ........................................................................ 19
Table 2: Document Roadmap of Additional Information Requested by DEA – 21 October 2013 . 20
Table 3: Document Roadmap of Additional Information Requested by DEA – 22 April 2014 ....... 22
Table 4: Summary of Comments and Responses ....................................................................... 63
Table 5. Solubility of oxygen in seawater (mg/L) under constant pressure (one atmosphere) for a
range of salinities and temperatures (Source: DWAFR 1995)........................................ 91
LIST OF FIGURES
Figure 1: CPTU’s and Calibration Borehole Locations ................................................................. 38
Figure 2: Existing configuration at Berth 205 end of Pier 2, prior to Berth Deepening (Note sea
water is removed from the picture for the purposes of clarity ....................................... 41
Figure 3: Dredge Basin and stabilise with scour protection as appropriate and construct sandbank
extension .................................................................................................................... 42
Figure 4: Install new Caisson quay wall....................................................................................... 42
Figure 5: Pre‐Berth Deepening: Long term 50year ‐ Mean total transport ................................... 46
Figure 6: Option‐3H Post‐Berth Deepening: Long term 50year ‐ Mean total transport ................. 47
Figure 7: Section A‐A (Central Sandbank Slope) Analysis .......................................................... 48
Figure 8: Section B‐B (Turning Basin Slope) Analysis ................................................................. 49
Figure 9: Section E‐E (Western Scour Protected Slope) Analysis ............................................... 50
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Figure 10: 1990 to 2100 sea level rise projections (after IPCC, 2001b; 2007b)2 with IPCC (2013)
Climate Change 2013, The Physical Science Basis, Summary for Policy Makers Ref
(16) 0.82 metres at 2100 ............................................................................................. 54
Figure 11: Existing Quaywall ....................................................................................................... 55
Figure 12: Post Construction – Year 2019 ................................................................................... 55
Figure 13: End of Structure Design Life – Year 2069 .................................................................. 56
Figure 14: Post Structure Design Life – Year 2100 ..................................................................... 56
Figure 15. Graphic demonstration of procedures for monitoring environmental impacts and
recovery. ..................................................................................................................... 84
Figure 16: Institutional Arrangements: Roles & Responsibility ..................................................... 85
Figure 17: Preferred Option Combination – Caisson Quay Wall with Option 3G Dredge Footprint.
.................................................................................................................................. 115
Figure 18: Area 1a (Preferred Sand Winning Area (Adapted from Maitland, 2012). .................. 116
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LIST OF APPENDICES
Appendix Description
Appendix A Correspondence from DEA:
1. Letter from DEA dated 21 October 2013
2. Letter from DEA dated 22 April 2014
Appendix B Specialist Studies:
1. Ecological Risk Assessment pertaining to the Estuarine Habitat in
Durban Bay by Extension of the Central Sandbank – Anchor
Environmental and CSIR;
2. Feasibility Study (FEL3) for the Deepening of Berths 203 to 205,
Port of Durban – Extension of Sandbank Engineering Risk
Assessment Revision D (ZAA 1370/RPT/040REVD) – ZAA
Engineering; and
3. Feasibility Study (FEL3) for the Deepening of Berths 203 to 205,
Port of Durban – Design Report – Effects of Climate Change on
Engineering Design Revision F (ZAA/1370/RPT/028REVF).
Appendix C Proof of Notification
1. Emails
2. SMSES
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LIST OF ACRONYMS AND ABBREVIATIONS
AR4 Assessment Report 4
As Arsenic
Cd Cadmium
CDP Chart Datum Port
Chl-a Chlorophyll -a
CO2 Carbon Dioxide
CPTu Pore water pressure
Cr Chromium
CSIR Council for Scientific and Industrial Research
Cu Copper
DEA Department of Environmental Affairs
EA Environmental Authorisation
ECO Environmental Control Officer
EIA Environmental Impact Assessment
EIR Environmental Impact Report
EMC Environmental Management Committee
EMPr Environmental Management Programme
EO Environmental Officer
FEL3 Feasibility 3
GCM General Circulation Model
GHG Greenhouse Gases
GPS Global Positioning Service
Hg Mercury
I&APS Interested and Affected Parties
IAEA International Atomic Energy Agency
IPCC Intergovernmental Panel on Climate Change
Km kilometre
mg milligrams
Ni Nickel
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Pb Lead
RCP Representative Concentration Pathways
SLR Sea Level Rise
STS Ship to Shore
TEU Twenty Foot Equivalent Unit
TNPA Transnet National Ports Authority
TSD Trailing Suction Dredger
TSS Total Suspended Solids
UK United Kingdom
UKCP UK Climate Projections
US United States
Zn Zinc
цm micrometres
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DEFINITIONS OF KEY TERMS
Alternatives In relation to a proposed activity, alternatives refer to the different means of meeting
the general purpose and requirements of the activity, which may include
alternatives to:
The property or location where it is proposed to undertake the activity;
The type of activity to be undertaken;
The design or layout of the activity;
The technology to be used in the activity;
The operational aspects of the activity; and
The option of not implementing the activity.
Bathymetry The sea bed “topography” derived from measurements of depths of water.
Benthic Referring to organisms living in or on the sediments of aquatic, estuarine and
marine habitats.
Benthos The sum total of organisms living in, or on, the sediments of aquatic habitats.
Biodiversity The variety of life forms, including the plants, animals and micro-organisms, the
genes they contain and the ecosystems and ecological processes of which they are
a part.
Biogeochemistry The study of the relationship between geochemistry of a region and the biology in
that region.
Biomass The living weight of a plant or animal population, usually expressed on a unit area
basis.
Biota The sum total of the living organisms of any designated area.
Chart Datum A reference point linked to the low water mark (ordinary spring tide) and used for
measuring sea water depth. In South Africa, a unique Chart Datum is identified for
each port. Chart Datum is defined by the Hydrographer as 0.913 metres below land
levelling datum.
Chart Datum Port Chart Datum Port is defined by Transnet National Port Authority as 0.900 metres
below land levelling datum.
Community An assemblage of organisms characterized by a distinctive combination of species
occupying a common environment.
Community
composition
All the types of taxa present in a community.
Community
structure
All the types of taxa present in a community and their relative abundances.
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Contaminant Biological (e.g. bacterial and viral pathogens) and chemical introductions capable of
producing an adverse response (effect) in a biological system, seriously injuring
structure and/or function.
Cope Line The outer edge of the quay wall.
Crustacea A highly diverse class of organisms containing crabs, shrimps, lobsters, isopods,
amphipods etc.
Detritus Unconsolidated sediments composed of both inorganic and dead and decaying
organic material.
Dewatering To remove water from an object, in this case sediment.
Dragline An excavating machine with a digging bucket attached by cables to a long jib and
operated by being dragged back toward the machine by another cable.
Echinoderms Phylum of marine invertebrates that includes sea urchins, starfish, brittle stars, sea
cucumbers. All are characterized by tube feet and five-part radially symmetrical
bodies.
Endangered A taxon is regarded as endangered when it faces a high risk of extinction in the wild.
This is defined as a 20% probability of extinction within 20 years.
Environment The biophysical, social, economic, cultural, political and historical context within
which people live and within which development takes place.
Environmental
impact
A change resulting from the effect of an activity on the environment, whether
desirable or undesirable. Impacts may be the direct consequence of an
organisation’s activities or may be indirectly caused by them.
Environmental
impact
assessment
Environmental Impact Assessment means a systematic process of identifying,
assessing and reporting environmental impacts associated with an activity.
Epifaunal Organisms, which live at or on the sediment surface being either attached (sessile)
or capable of movement.
Habitat The place where a population (e.g. animal, plant, micro-organism) lives and its
surroundings, both living and non-living.
Infauna Animals of any size living within the sediment. They move freely through interstitial
spaces between sedimentary particles or they build burrows or tubes.
Interested and
affected party
Individuals or groups concerned with or affected by an activity and its
consequences. These include the authorities, local communities, investors, work
force, consumers, environmental interest groups and the general public.
Isopod Any of various small terrestrial or aquatic crustaceans with seven pairs of legs
adapted for crawling.
Lithogenic Derived from rocks and/or soils
Macrofauna Animals which are greater than 1 mm.
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Macrophyte A member of the macroscopic plant life of an area, especially of a body of water;
large aquatic plant.
Molluscs A phylum of organisms containing snails, mussels, oysters.
Piscivorous Feeding on fishes.
Pollution The introduction of unwanted components into waters, air or soil, usually as result of
human activity; e.g. hot water in rivers, sewage in the sea, oil on land.
Population Population is defined as the total number of individuals of the species or taxon.
Recruitment The replenishment or addition of individuals of an animal or plant population
through reproduction, dispersion and migration.
Re-suspension A renewed suspension of particulates.
Sediment Unconsolidated mineral and/or organic particulate material.
Significant impact An impact that by its magnitude, duration, intensity or probability of occurrence may
have a notable effect on one or more aspects of the environment.
Sipunculids Small unsegmented marine worm that when disturbed retracts its anterior portion
into the body giving the appearance of a peanut.
Species A group of organisms that resemble each other to a greater degree than members
of other groups and that form a reproductively isolated group that will not produce
viable offspring if bred with members of another group.
Suspended
material
Total mass of material suspended in a given volume of water, measured in mg/l.
Taxon (Taxa): Any group of organisms considered to be sufficiently distinct from other such groups
to be treated as a separate unit (e.g. species, genera, families).
Toxicity The inherent potential or capacity of a material to cause adverse effects in a living
organism.
Turbidity Turbidity is the attenuation of light in water caused by the sum of suspended
particles and any dissolved chemicals in the water which may alter the passage of
light through scattering (generally inorganic and organic particles) and/or absorption
(generally particulate or dissolved biological material).
Vulnerable A taxon is vulnerable when it is facing a medium risk of extinction in the wild in the
medium-term future, defined as a 10% probability of extinction within 100 years.
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1 PURPOSE OF THIS DOCUMENT
On 05 August 2013 the final Environmental Impact Assessment (EIA) Report was submitted
to the Department of Environmental Affairs (DEA) for review and authorisation. On 21
October 2013 Nemai Consulting received a letter from DEA stating that the final EIA report
was rejected. The Department requested additional information before it could make a
decision. Refer to Appendix A for a copy of the letter dated 21/10/14.
The Specialists presented the revised reports to DEA on 28 February 2014. Subsequently,
DEA provided additional correspondence regarding their requirements in a letter dated 22
April 2014. Refer to Appendix A for a copy of the DEA letter dated 22/04/14.
The purpose of the Amended EIA Report is twofold:
1. To fulfil the requirements raised DEA in the letters dated 21 October 2013 and 22
April 2014; and
2. To allow Registered Interested and Affected Parties an opportunity to review the
Amended EIA Report for a period of 30 day from 03 June 2014 to 03 July 2014
This Amended EIA Report is available for public review on the project website
(www.berth203to205expansioneia.co.za).
It is also available at the following locations:
Table 1: Locations for review of Draft EIA Report
No. Location Address Tel. No.
1. The Seafarers Club 1 Seafarers Road, Bayhead, Durban 031 466 1326
2. Central Reference
Library - Durban
10th Floor, Liberty Towers, 214 Dr Pixley
KaSeme Street, Durban 031 322 4414
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2 DOCUMENT ROADMAP
The Document Roadmap below provides details on how the comments raised by DEA were
taken into account in the Amended EIA Report. The purpose of this table is to ensure that all
DEA’s requests have been met.
Table 2: Document Roadmap of Additional Information Requested by DEA – 21 October 2013
Chapter Title Requirement from DEA
(21/10/2013) Details of how comment
has been addressed Included
1. Purpose of this Document
– –
2. Document Roadmap – –
3. Summary of Additional Specialist Studies
What are the baseline and thresholds of acceptable change against which monitoring will take place? Ecological Risk
Assessment pertaining to the Estuarine Habitat in Durban Bay by Extension of the Central Sandbank – CSIR and Anchor Environmental Feasibility Study (FEL3) for the Deepening of Berths 203 to 205, Port of Durban – Extension of Sandbank Engineering Risk Assessment Revision D (ZAA 1370/RPT/040REVD) – ZAA Engineering
What actions are proposed should the monitoring results detect change?
What are the socio-economic and ecological implications should the proposed mitigation measure prove unsuccessful?
Consideration must be given on how realistic and practical the mitigation measure is. Consideration must be given on what costly commitment and assurances have been provided by the applicant.
Gaps, uncertainties and assumptions must clearly be reported.
Climate Change Risks such as sea level rise and storm surges must be addressed.
Feasibility Study (FEL3) for the Deepening of Berths 203 to 205, Port of Durban – Design Report – Effects of Climate Change on Engineering Design Revision F (ZAA/1370/RPT/028REVF).
Climate Change Risk and Vulnerability Assessment to adequately address how sea level rise and coastal storm surges will be addressed during construction and operational phase of the proposed development
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Chapter Title Requirement from DEA
(21/10/2013) Details of how comment
has been addressed Included
4. Summary of Responses
What are the baseline and thresholds of acceptable change against which monitoring will take place?
What actions are proposed should the monitoring results detect change?
What are the socio-economic and ecological implications should the proposed mitigation measure prove unsuccessful?
Consideration must be given on how realistic and practical the mitigation measure is. Consideration must be given on what costly commitment and assurances have been provided by the applicant.
Gaps, uncertainties and assumptions must clearly be reported.
Climate Change Risks such as sea level rise and storm surges must be addressed.
Climate Change Risk and Vulnerability Assessment to adequately address how sea level rise and coastal storm surges will be addressed during construction and operational phase of the proposed development
Long Term Maintenance burden must be considered.
Provided in Summary of Responses
5. Additional Mitigation Measures
- -
6. Conclusions and Recommendations
- -
Appendix A – Letter from DEA
Appendix B – Additional Specialist Study Reports
Appendix C – Proof of Public Participation
You are required to amend the EIA report to include the above and make the amended report available to all registered interested and affected parties for a 30 day commenting period.
A 30 Day public review period will be provided. All proof of notification to registered I&Aps is provided.
Appendix D – Comments and Responses
All comments received during the review period will be submitted to DEA.
In final Report
Table 3 contains the requirements of the DEA set out in the letter dated 22 April 2014.
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Table 3: Document Roadmap of Additional Information Requested by DEA – 22 April 2014
Chapter Title Requirement from DEA
(22/04/2014) Details of how comment
has been addressed Included
1. Purpose of this Document
– –
2. Document Roadmap – –
3.
Summary of Additional Specialist Studies
Re-use of dredging material is international best practice. The report should provide examples and references thereof.
Ecological Risk Assessment pertaining to the Estuarine Habitat in Durban Bay by Extension of the Central Sandbank – CSIR and Anchor Environmental
Consideration must be given to the chemical pollutants of the dredge material.
Information regarding climate risks, sea level rise impacts and storm surges must be included in the report.
Feasibility Study (FEL3) for the Deepening of Berths 203 to 205, Port of Durban – Design Report – Effects of Climate Change on Engineering Design Revision F (ZAA/1370/RPT/028REVF).
4.
The stability of the newly created sandbank and cutaway were exhausted tested and it was found that the new design would be more stable than the current layout.
Feasibility Study (FEL3) for the Deepening of Berths 203 to 205, Port of Durban – Extension of Sandbank Engineering Risk Assessment Revision D (ZAA 1370/RPT/040REVD) – ZAA Engineering
5.
The revised report should provide examples and references showing that there are no risks regarding the establishment of alien invasive species.
Ecological Risk Assessment pertaining to the Estuarine Habitat in Durban Bay by Extension of the Central Sandbank – CSIR and Anchor Environmental
6. Summary of Responses
The report should provide examples and references of reuse of dredging; Consideration must be given to the chemical pollutants of the dredge material; Information regarding climate risks, sea level rise impacts and storm surges must be included in the report; The stability of the newly created sandbank and cutaway were exhausted tested and it was found that the new design would be more stable than the current layout; The revised report should provide examples and references showing that there are no risks regarding the establishment of alien invasive species; and Mitigation measures to be provided.
Provided in Summary of Responses
7.
Additional Mitigation Measures
Quarterly or more frequent monitoring would be undertaken for 5 years
Provided in the Summary of additional mitigation measures Silt levels in the water column must
be maintained at ‘moderate’ levels
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Chapter Title Requirement from DEA
(22/04/2014) Details of how comment
has been addressed Included
and silt screens must be used while dredging wherever possible
The little lagoon would be specially protected during construction and afterwards
Minimized disturbance on sandbanks during construction including:
No construction workers allowed on Sandbank;
Dredging within 100m of the Sandbank to be undertaken during winter;
No dredging to be done at night;
Dredging within a 100m should be done as far as possible at only site at a time;
A significant portion of Central Sandbank must remain untouched during dredging;
Qualified Environmental Offices need to monitor construction activities;
Reporting to the DEA must be frequent and reporting of disturbances must be almost in a real time basis; and
If mitigation and rehabilitation measures fail then offset measures need to be discussed.
Specific mitigation procedures will need to form part of the Dumping at Sea Permits. New best practices measures and standards gazetted in 2012 must be used in the assessment of the Dumping at Sea Permit.
A monitoring programme should include sandbank morphology, sediment granulometry and organic content, benthic macrofauna, avifauna and levels of pollutants. Monitoring must be undertaken intensely for 2 years and continue less intensely for another 3 years.
Adaption and mitigation measures which may be of importance to infrastructure (in terms of climate change) must be addressed.
8. Conclusions and Recommendations
- -
Appendix A – Correspondence from DEA (21 October 2013 and 22 April 2014)
Appendix B – Additional Specialist Study Reports
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Chapter Title Requirement from DEA
(22/04/2014) Details of how comment
has been addressed Included
Appendix C – Proof of Public Participation -
-
Appendix D – Comments and Responses
-
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3 PROJECT MILESTONES
The following milestones have been reached to date during the EIA process:
1. The Application for Environmental Authorisation was submitted to the
Department of Environmental Affairs (DEA) on 10 February 2012.
2. DEA approved the Scoping Report on 27 August 2012.
3. The final EIA report was rejected by the DEA on 21 October 2013. The DEA
requested additional information on the Central Sandbank and Climate Change
issues.
4. Additional specialist studies were undertaken. This information was presented to
the DEA on 28 February 2014. A letter provided by the DEA on 22 April 2014
provides a summary of the discussions and additional information requirements.
5. The Additional Information Report, Specialist Studies and Correspondence from
DEA are available for public review for a period of 30 days (03 June 2014 to 03
July 2014).
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4 SUMMARY OF ADDITIONAL SPECIALIST STUDIES
4.1 Comments from DEA
The comments received from DEA on 21 October 2013 can be summarised as follows:
Central Sandbank Information Requests
• What are the baseline and thresholds of acceptable change against which
monitoring will take place?
• What actions are proposed should the monitoring results detect change?
• What are the socio-economic and ecological implications should the proposed
mitigation measure prove unsuccessful?
• All the potential risks and mitigation measures associated with the creation of the
Portion of Central Sandbank as a mitigation measure must therefore be fully
assessed and be addressed in the amended report.
• Consideration must be given on how realistic and practical the mitigation
measure is.
• Consideration must be given on what costly commitment and assurances have
been provided by the applicant.
• Gaps, uncertainties and assumptions must clearly be reported.
• Long Term Maintenance burden must be considered.
In order to address these comments the following two studies were compiled and are
summarised in Chapter 5.2 and 5.3.
1. Ecological Risk Assessment pertaining to the Estuarine Habitat in Durban Bay by
Extension of the Central Sandbank – Anchor Environmental and CSIR; and
2. Feasibility Study (FEL3) for the Deepening of Berths 203 to 205, Port of Durban
– Extension of Sandbank Engineering Risk Assessment Revision D (ZAA
1370/RPT/040REVD) – ZAA Engineering.
Climate Change Information Request
• Climate Change Risks such as sea level rise and storm surges must be
addressed.
• A Climate Change Risk and Vulnerability Assessment to adequately address
how sea level rise and coastal storm surges will be addressed during
construction and operational phase of the proposed development.
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To address these comments, one additional study was undertaken:
1. Feasibility Study (FEL3) for the Deepening of Berths 203 to 205, Port of Durban
– Design Report – Effects of Climate Change on Engineering Design Revision F
(ZAA/1370/RPT/028REVF).
This report is summarised in Chapter 5.4.
The comments received from DEA on 22 April 2014 can be summarised in the following
manner:
Re-Use of Dredge Material
• Re-use of dredging material is international best practice. The report should
provide examples and references thereof.
• Consideration must be given to the chemical pollutants of the dredge material.
In order to address these comments the following two studies were compiled and are
summarised in Chapter 5.2 and 5.3.
1. Ecological Risk Assessment pertaining to the Estuarine Habitat in Durban Bay by
Extension of the Central Sandbank – Anchor Environmental and CSIR; and
2. Feasibility Study (FEL3) for the Deepening of Berths 203 to 205, Port of Durban –
Extension of Sandbank Engineering Risk Assessment Revision D (ZAA
1370/RPT/040REVD) – ZAA Engineering.
Climate Change
• Information regarding climate risks, sea level rise impacts and storm surges must
be included in the report.
• Mitigation measures to be provided.
To address these comments, one additional study was undertaken:
1. Feasibility Study (FEL3) for the Deepening of Berths 203 to 205, Port of Durban –
Design Report – Effects of Climate Change on Engineering Design Revision F
(ZAA/1370/RPT/028REVF).
This report is summarised in Chapter 5.4.
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Mitigation Measures and Monitoring
• Quarterly or more frequent monitoring would be undertaken for 5 years
• Silt levels in the water column must be maintained at ‘moderate’ levels and silt
screens must be used while dredging wherever possible
• The little lagoon would be specially protected during construction and afterwards
• Minimized disturbance on sandbanks during construction including:
o No construction workers allowed on Sandbank;
o Dredging within 100m of the Sandbank to be undertaken during winter;
o No dredging to be done at night;
o Dredging within a 100m should be done as far as possible at only site at a
time;
o A significant portion of Central Sandbank must remain untouched during
dredging;
o Qualified Environmental Offices need to monitor construction activities;
o Reporting to the DEA must be frequent and reporting of disturbances must
be almost in a real time basis; and
o If mitigation and rehabilitation measures fail then offset measures need to
be discussed.
• Specific mitigation procedures will need to form part of the Dumping at Sea
Permits. New best practices measures and standards gazetted in 2012 must be
used in the assessment of the Dumping at Sea Permit.
• A monitoring programme should include sandbank morphology, sediment
granulometry and organic content, benthic macrofauna, avifauna and levels of
pollutants. Monitoring must be undertaken intensely for 2 years from the day
when the sandbanks are created and continue less intensely for another 3 years.
• Adaption and mitigation measures which may be of importance to infrastructure
(in terms of climate change) must be addressed.
In order to address these comments the following two studies were compiled and are
summarised in Chapter 5.2 and 5.3.
1. Ecological Risk Assessment pertaining to the Estuarine Habitat in Durban Bay by
Extension of the Central Sandbank – Anchor Environmental and CSIR; and
2. Feasibility Study (FEL3) for the Deepening of Berths 203 to 205, Port of Durban
– Extension of Sandbank Engineering Risk Assessment Revision D (ZAA
1370/RPT/040REVD) – ZAA Engineering.
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3. Feasibility Study (FEL3) for the Deepening of Berths 203 to 205, Port of Durban
– Design Report – Effects of Climate Change on Engineering Design Revision F
(ZAA/1370/RPT/028REVF).
Mitigation measures have been discussed in all three studies. Further, a summary of
mitigation measures regarding dredging, Central Sandbank, Little Lagoon, Avifauna etc. will
be included in Chapter 7.
4.2 Ecological Risk Assessment pertaining to the Estuarine Habitat in Durban Bay
by Extension of the Central Sandbank – CSIR and Anchor Environmental
4.2.1 Specialist
Specialists
Organisation: Anchor Environmental Coastal Systems Research Group, CSIR
Name: Dr Barry Clark Dr Steven Weerts Dr. Brent
Newman
Qualifications: Ph.D. Marine Biology, 1997, University of
Cape Town
BSc (Hons) Marine Biology, 1991, University
of Cape Town
PhD. - PhD
No. of years
experience:
21 18 17
Affiliations Professional Natural Scientist, registered
with the South African Council for Natural
Scientific Professions
Professional member of the South African
Institute of Ecologists and Environmental
Scientists
South African representative to the
SURVAS Network
Member of the International Association
of Impact Assessors
Member of the Subsistence Fisheries Task
Group
Member of the Subsistence Fisheries
Advisory Group
Member of the South African Network for
Coastal and Oceanic Research (SANCOR)
Economics Task Team
CERM N/A
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4.2.2 Main Findings
This section provides a summary of baseline thresholds and ecological risks of the Central
Sandbank Extension (CSIR and Anchor Environmental, 2014), as contained in Appendix
B1.
4.2.2.1 Summary of the EIA Ecological Assessment:
A summary of the Ecological Assessment undertaken during the EIA including the Anchor
Environmental, 2012a, 2012b and 2012c as well as CSIR, 2012a and b. was provided. The
most salient points are listed below:
The ecological assessment addressed all risks to major fauna and flora groups
such as microalgae (phytoplankton), invertebrates (benthic invertebrates and
zooplankton), fish and birds.
Risks to macrophytes (such as mangroves) were deemed negligible.
Quantitative assessments of habitat losses and gains were undertaken and
initially the only tidal banks to be impacted were the Central Sandbank and the
Little Lagoon. This involved the loss of intertidal sandflat as well as sloping
subtidal sandbank. Losses due to scour protection were also noted.
Mitigated design options resulted in Option 3H which had the lowest impact in
terms of habitat losses and resulted in a slight increase in Sandbank habitat
through the Sandbank extension.
Low intertidal and shallow subtidal sandbank habitats have high value in terms of
nursery habitat for estuarine fishes and crustaceans. Option 3H results in gains
in these areas.
Changes in hydrodynamics were found to result in some changes to bed sheer
stressed. However in terms of structural changes to benthic habitats these are
largely insignificant except in the area near the Berth 205 which is expected to
become coarser in nature.
Results indicated that changes in water fluxes associated with the development
across most of the Port would be minimal and significant long term changes ti
water and sediment quality were deemed unlikely.
Although Option 3H would result in a modified ecosystem functioning in
comparison to the present layout, its residual impact would be neutral if the
Sandbank extension was successful and may even result in a residual positive
impact.
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Potential impacts associated with elevated suspended sediment concentrations
in the water column and toxicity of heavy metals, hydrocarbons and
polychlorinated biphenyls were also assessed. The findings showed that the
concentrations of metals and organic chemicals in sediment within and near the
dredge footprint were very low and thus there was a very low probability that
chemicals released during the dredging process would be present in the water
column at toxic levels.
Hydrodynamic modelling to assess the impact of suspended sediment
concentrations in the water column were also undertaken. The findings show that
the concentrations would reach 80mg/l in the immediate vicinity of the dredge
head but at the Central Sandbank, concentrations would not exceed 50mg/l
which is in the medium risk category for microalgae, invertebrates and fish.
Due to the fact that suspended sediment concentrations along the east coast
estuaries are naturally higher than in coastal waters and thus local fauna tend to
be quite tolerant of these conditions, it was concluded that 50mg/l would be in a
low significance range (although sediment concentrations should be carefully
monitored).
4.2.2.2 Ecological Risk Assessment – Baseline Thresholds of Acceptance Change
Baseline thresholds need to be established in order to confirm the defined
maximum/minimum water quality thresholds, to confirm the biotic community composition on
the existing sandbank and to allow comparisons after the sandbank extension which show
whether the extension has been successful.
These thresholds will be determined from ecological baseline data that will be collected over
a period of 12-24 months prior to the start of the project.
The baseline assessments will focus on the following components:
Physico-chemical (habitat) variables:
Total Suspended Solids (TSS);
Salinity;
Temperature;
Dissolved Oxygen;
Sediment Grain Size Distribution;
Organic Carbon Content; and
Trace metal content in sediment (Cd, Hg, As, Cr, Cu, Pb, Ni, Zn).
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Faunal and floral assemblages:
Benthic microalgae (microphytobenthos);
Benthic macrofauna;
Ichythyfauna; and
Avifauna.
Please note the variables in bold and underlined agree with the recommendations of the
DEA Letter – 22 April 2014. All other variables are included as additional requirements.
The methods for obtaining these baseline data was described in detail and can be reviewed
in the Specialist report in Appendix B1.
Details on primary impact vector was also provided as well as the general baseline values.
The main impact is expected to be levels of suspended sediment and/or organic material in
the water column which affect living organisms by reducing levels of dissolved oxygen in the
water column. Based on Steffani et al. (2003), low risk is seen to be <20mg/l; medium risk is
seen to be 20mg/l-80mg/l and high risk is >80mg/l.
Based on this, during construction phase, monitoring will ensure that suspended solids
remain below 50mg/l and that oxygen levels do not drop below 5mg/l (99% of the time or
more than 1 minute in every 60 minutes) or 6mg/l (95% of the time or 3 minutes in every 60
minutes). Should the monitoring show that turbidity or dissolved oxygen exceed these
recommendations, then dredging will stop until levels have declined below this point. Silt
curtains are also recommended should these thresholds be frequently exceeded. In addition,
choking of the dredge hopper overflow is also suggested so that the fluid level in the hopper
is maintained and as a result no air is taken down with the suspension leaving the hopper.
The approach for assessing the rate of recovery of the newly created portion of the Central
Sandbank is also provided and will be based on the concept of bioequivalence. The number
of species, abundance and/or biomass of the organisms in question at the rehabilitation site
should be at least 80% of the measured pre-impact baseline levels (and/or those at
comparable control stations) and must remain this way for at least two years before the site
can be considered rehabilitated. Monitoring will take place for at least 5 years.
4.2.2.3 Ecological Risk Assessment – What actions are proposed if the monitoring
results detect change?
As discussed above, the main impact during the construction phase is related to turbidity
and dissolved oxygen.
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However, a number of mitigation measures have been provided and suspended solids will
be controlled in three ways.
The dredge hopper overflow will be choked with a fully automated computerised
process controller to ensure that there is a constant fluid level in the hopper is
maintained and thus no air is taken down with the suspension. This has been
shown to significantly decrease turbidity in surrounding waters.
The concentration of suspended solids in the Bay area will also be controlled via
the use of silt curtains.
Monitoring is the last measure. Should the monitoring show that these levels
exceed acceptable levels, then dredge operations will be halted immediately until
levels have declined below threshold levels.
4.2.2.4 Ecological Risk Assessment – What are the socio-economic and ecological
implications should the proposed mitigation measure prove unsuccessful?
In the event that the proposed mitigation measure (i.e. Sandbank extension) proves
unsuccessful, the estimated impact is estimated to be equivalent to those associated with
Design Option 3C which was originally assessed in the EIR. This would result in a net loss of
6.4% of existing intertidal and subtidal area. High intertidal area near the Little Lagoon would
be lost (14.2%) but offset by an increase in low intertidal area (1.3%) resulting in a zero net
loss of tidal sandbank at the Little Lagoon.
Losses of sandbank would also result in further losses of ecological goods and services as
the sandbank habitat in Durban Bay has already been reduced to only 14% of its original
extent.
At best, the ecological losses would be directly proportional to the habitat losses (i.e. 5.6%
loss of sandbank will result in a 5.6% loss of associated ecological function). This impact
may however be disproportionally large due to the fact that so much of this habitat has been
affected in the past.
Socio-economic implications are difficult to predict as the socio-economic benefits cannot be
explicitly quantified. The primary value of the sandbank habitats is their ecological function
as estuarine nursery habitat and thus the primary socio-economic benefit is related to
recreational and subsistence fisherman. The planned habitat development would increase
this habitat and would likely have a positive socio-economic benefit.
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4.2.2.5 Ecological Risk Assessment associated with the creation of a Portion of
Central Sandbank
Ecological risk assessment relies on sound ecological rationale and knowledge of habitats
and species involved, review of available scientific literature and consideration of appropriate
case studies.
The ultimate measure of ecological success is whether or not the habitat is used beneficially
by the appropriate biota and fulfils its intended function. In Durban Bay, the invertebrate
benthic fauna are fundamental and the main issues that need to be assessed is will the
colonisation take place naturally?, how long will it take?, in what abundance will species
establish populations? And will succession to a functional ecological community take place
naturally?
In the context of this study, the majority of biota typical of the sandbank habitat have pelagic
larval forms that are widely dispersed in the water column by currents. Thus in Durban Bay,
a ready source of larvae is available for colonisation of the newly created suitable habitat
(Section 5.3 will provide more detail on the engineering design of this suitable habitat). The
sandprawn, Callichirus kraussi, does not have a planktonic larval stage but relies on young
which are hatched and developed in parent burrows and then tunnel off of these burrows. A
post-larval dispersive stage does occur however and quick generation times and strong
recruitment are indicative that C. kraussi would recruit strongly onto the newly created
sandbank habitat with high confidence.
Colonisation by invasive alien species is not predicted to be a threat due to the high salinities
in the area as well as the fact that one of the main invasive species required hard surfaces
and thus will not colonise sandbank habitat.
Further, due to the proximity of the new sandbank to the original sandbank as well as the
fact that the proposed sandbank extension will be created using locally sourced material
provide further surety of the ecological success of the extension. In addition, sediments
which have to be removed from the Central Sandbank unavoidably, will be used to ‘cap ‘the
newly created habitat and will contain invertebrates which will fast-track the process.
Numerous experimental studies as well as field studies suggest that benthic colonisation will
take between 3 months and 2 years. A number of studies are explained in more detail in the
Specialist Study.
Examples of local engineered estuarine habitats are provided. The first is that of the
Mhlathuze Estuary. Tidal changes brought about by changes in tides resulted in a huge
increase in the mangroves of the area. The Little Lagoon in the Port of Durban is also known
as a biodiversity hotspot however, this area was artificially created in the 1970s by the
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expansion of Port facilities which truncated a shallow channel through the sandbanks and
thus created an open basin.
Based on the long term engineering stability, the initial colonisation, succession and
establishment of an ecologically functioning benthic community is certain. Further, given the
proximity of the sandbank to the existing sandbank and its similarity in terms of structure,
granulometry and hydrodynamic characteristics, it is highly likely that a similar biological
community will develop. Successful establishment of benthic biota will result in profitable
utilisation of the created habitat by birds and fish. It will also provide shallow juvenile feeding
areas. The current bathymetry of the Bay has a strong predominance of deep water or
intertidal habitat and shallow subtidal habitat is limited which reduces the nursery function of
the Bay. The proposed extension will thus fulfil an ecological role that is congruent with the
Bay’s ecological value as an estuary and thus in the long term will improve the system’s
ecological value.
4.3 Feasibility Study (FEL3) for the Deepening of Berths 203 to 205, Port of Durban –
Extension of Sandbank Engineering Risk Assessment (ZAA1370/RPT/040REVD)
– ZAA Engineering
4.3.1 Specialist
Specialist
Organisation: ZAA Engineering Projects and Naval Architecture (Pty) Ltd
Name: Dr John Zietsman
Qualifications: BSc (CivEng), UCT, MSc (Ocean Eng) University College London, PhD
University of London
No. of years experience: 39
Affiliations PrEng,
FSAICE,
MICE,
MRINA (overseas),
MSNAME,
FSAAE,
CEng
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4.3.2 Main Findings
This section provides a summary of the Sandbank Extension Risk Assessment. It also
provides details on the proposed design of the Sandbank as well as the findings of key
modelling studies. The full report is contained in Appendix B2.
This report summarised the work that has been carried out as part of the FEL3 study and
has addressed in particular the engineering issues, with respect to the extension of the
central sandbank, raised by the Department of Environmental Affairs in its letter Ref
14/12/16/3/3/2/275 signed on 21 October 2013 and issued in response to the initial EIA
Report, by means of the following:
A comprehensive Risk and Mitigation Analysis covering both the construction of
the extension and the maintenance of the sandbank during the operational
phase of the new container terminal at Pier
Development of a Method Statement for the construction of the sandbank
Hydrodynamic and morphological analyses of the Port of Durban using DELFT‐
3D to determine the short and long term stability and form of the extended
sandbank, including the effects of wave penetration, wind and currents due to
tidal movements and other effects. These studies indicate that the extended
sandbank will be stable and that it will not endanger the stability of the existing
sandbank during construction, or during operation of the container terminal. It
also indicates that flows will not change in the area of the Little Lagoon and this,
combined with the sheet pile protection to be installed, will ensure that the Little
Lagoon is not disturbed.
Hydrodynamic analyses have been carried out to assess the levels of turbidity
and total suspended solids (TSS) that will result from the dredging operations
and the studies have confirmed that levels will be within acceptable limits.
Geotechnical finite element analyses have been carried out using the computer
programme PLAXIS to ensure the stability of the sandbank extension.
An extensive on site geotechnical investigation (involving Cone Penetrometer
Testing with pore water pressure data (CPTu) and proof drilling and logging) has
been carried out to determine the nature and suitability of the sands that will be
dredged from the basin, for use in the construction of the sandbank extension.
Comprehensive dredging analysis and design has been carried out.
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This report has demonstrated how the Risk and Mitigation Process will be managed and how
all the technical engineering risks have been and will continue to be managed to
internationally acceptable levels.
4.3.2.1 Quantities and Materials
The estimated quantity of sand to be dredged and placed is approximately 1,300,000 m3.
Based on the geotechnical investigations that have been conducted, in particular as
recorded in ZAA 1370‐RPT‐031 ‐ Soil Material for Reclamation of the Central Sandbank, it is
expected that approximately 300,000 m3 of this sand will be newly reclaimed material from
the designated off‐shore borrow areas and the major portion of 1,000,000 m3 will come from
material selected from the dredging of the basin to ‐16,5 m CDP. This should result in
efficiencies of scale and time, as it removes the requirement for each load of dredged
material to be dumped out to sea and in turn material to be imported at a later stage for
reclamation. The area circled in red below has been shown to have suitable sand/silt/clay
mix of approximately 90% sand and 10% silt/clay to a depth of approximately 6m below
seabed level for use in building the extension of the sandbank. The volume associated with
the outline area is approximately 600,000 cubic metres. Approximately 400 000 cubic metres
of suitable material will also be available from the existing fill and sandbank area that will be
excavated and dredged for the proposed extension to Berth 205.
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Figure 1: CPTU’s and Calibration Borehole Locations
The maximum fines content (smaller than 63 μm) of the material used for hydraulically
placed fill is usually limited to approximately 10% for load bearing fill (Ref. 6 of Report 1370‐
RPT‐031). However since the reclaimed area has no bearing load other than its own self‐
weight which is further reduced due to the slope being submerged, the above percentage
may be increased to a level of less than 30%, On the basis described above, the clay‐rich
zones are excluded and sand‐rich zones are identified as potential borrow sources for
reclamation. To the greatest extent possible, the sediment texture (grain size and sorting) is
critical for success and sand fill must be compatible with native sandbank sand.
This requirement applies to fill as delivered to the reclamation site, and not necessarily to in‐
situ material in the borrow area. Sampling on‐board the dredgers to check the grading of
material is required to confirm that the required specification for fill delivered to the site is
satisfied. Samples shall also be taken at the reclamation site, to check if segregation of
material has occurred during placing, with a view to ensuring that the fines are well
distributed within the reclamation.
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4.3.2.2 Summary of Sandbank Creation Method
The method of dredging and construction of the sandbank extension may therefore be
summarized as follows:
Set up a survey programme, determining setting out points of the area to be
filled. This must be compared with previous surveys and the baseline agreed.
Conduct a video survey of the existing slopes for record purposes.
Set up pollution control measures – refer to Section 7.2 below.
Install sheet piling at the Berth 205 extension end of Pier 2 to ensure that the
central sandbank and the little lagoon area are secured from any disturbance.
Mobilize and commission suitable dredging equipment, marine operating staff,
diving crews and support boats. The anticipated dredging equipment is a Trailing
Suction Dredger (TSD), fitted with discharge pumps and floating hoses from a
bow coupling.
Dredge clean reclaim material from designated and approved borrow site
offshore or as part of other dredging work for the project.
Provide samples for confirmation of suitability of material on a continuous basis
through laboratory grading analysis
Place sandbags along the line of the new toe of the extended sandbank to form
a low retaining structure. Bio‐degradable sandbags will be used
Place a further row of sandbags along the existing toe of the sandbank at the ‐
12.8 m CDP level. This is intended to prevent material flowing down the slope at
too fast a rate and flowing outwards along the bottom. More than one row of
these bags may be required
Set up silt curtains as described below
Provide diffusers at the ends of hoses to reduce flow velocities and prevent
scouring
Pump the reclaim material from the dredger through floating hoses along the line
of the present top edge of the sandbank. Monitor the deposition of sand behind
the sandbag retaining structure in a sequence so that the area is filled evenly in
layers along the face of the sandbank and rises in layers from below. This
procedure will reduce entrainment of sand in the water column and thus reduce
turbidity.
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Controlled even placement of thin layers of fill on the reclamation site is
necessary to avoid shear failure of the underlying layers and the formation of
mud waves.
Layers will be staggered, with control being exercised to ensure a sufficient
leading edge for the underlying layer in relation to the layer being formed
Monitor turbidity in the water column and adjust deposition rates or suspend
operations as needed.
Fill to the pre‐determined level, with periodic dives providing video records of the
new profile.
Conduct interim and acceptance surveys for confirmation of final levels achieved
and for measurement of quantities.
The dredged material will be placed on the area of extension of the sandbank in sections
confined by means of silt curtains. These silt curtains will have the following properties:
Sourced from reputable manufacturers with a proven track record.
Designed for the specific application and shall follow the manufacturer’s
recommendations and guidelines for setting up and maintaining such items as
well as guidelines for installation and safety measures.
For use in areas where tidal currents are present
Curtains will be deployed so that the size of individual paddocks will not exceed
one week’s work.
Curved shapes will be preferred as they are less susceptible to wave damage.
Curtains will be extended to the bottom of the waterway in tidal or moving water
conditions, a heavy woven permeable filter fabric or tide flaps shall be designed
into the curtain to relieve pressure on the curtain wall.
Silt curtains will only be used in conditions of slow to moderate currents, stable
water levels, and relatively shallow water depths.
Operations within silt curtains will not continue in current velocities greater than 2
knots unless there are unusual circumstances, as in all but the slowest current
flows, curtains will billow out in the downstream direction, allowing water to pass
beneath the curtain, thereby reducing the effective skirt depth.
Extra length (up to 10‐20 percent) and depth (slack) of curtains shall be included
in designs to allow for tidal fluctuations and exchanges of water within the
curtain.
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Special designs by the suppliers shall be provided for applications of curtains at
the required depths of 16 to 18 m or with currents exceeding 1.5 knots to ensure
that loads on curtains and mooring systems are not excessive and result in
failure of standard construction materials.
It should be noted that
o High winds can lift large curtains out of the water like a sail.
o Curtains can sink due to excessive biological or silt fouling on the fabric.
The number of joints in the curtain will be minimized – a minimum continuous
span of at least 15m shall be provided between joints.
Curtains will be a bright colour (yellow or International Orange) to enhance
visibility for vessels.
In tidal situations, where currents move in both directions, anchors will be
attached on both sides of the curtain to hold the curtain in place and to not allow
a curtain to overrun the anchors and pull them out when the tide reverses.
Anchor lines will be attached to the flotation devices.
Care will be taken during removal of silt curtains to avoid and minimize re‐
suspension of settled solids.
The sequence of installing sheet piling to secure the stability the Little Lagoon and the
central sandbank in the 205 extension area, prior to dredging, followed by dredging and
installation of the caissons, is shown in the following sequence of Figures.
Figure 2: Existing configuration at Berth 205 end of Pier 2, prior to Berth Deepening (Note sea water
is removed from the picture for the purposes of clarity
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Figure 3: Dredge Basin and stabilise with scour protection as appropriate and construct sandbank
extension
Figure 4: Install new Caisson quay wall
4.3.2.3 Engineering Risk and Mitigation Summary
A Risk and Mitigation summary is provided below in regards to the Central Sandbank
Expansion. With mitigation all risks are reduced to ‘rare’ and ‘minor’ except for the fact that
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high swells at sea will cause delays in the schedule. Although the impact with mitigation is
‘minor’, the likelihood remains ‘almost certain’.
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4.3.2.4 Central Sandbank Morphological Study Summary
The study also provides a summary of the Central Sandbank morphological study.
A morphological acceleration factor has been applied to a 10 day simulation to effectively
illustrate the effect of erosion and sedimentation on the central sandbank, after a 50 year
period. This simulation has been performed for both scenarios, and has been repeated for
the Option 3H scenario with the effects of ocean waves omitted.
It has to be noted that the varying wind directions and velocities used for this 10 day period,
are typical for a spring season (actual recorded data for early October 2012 has been used).
Hence the accelerated results more closely represent what might be expected after a 50
year long spring season. The main purpose of these simulations is to compare pre‐ and
post‐construction scenarios and ascertain whether or not construction of the sandbank
extension resulted in significantly different erosion and deposition.
Figure 5: Pre‐Berth Deepening: Long term 50year ‐ Mean total transport
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Figure 6: Option‐3H Post‐Berth Deepening: Long term 50year ‐ Mean total transport
Comparing for all scenarios, it may be seen that in each case, there are no discernable
differences in erosion and depositional trends for the sandbank or the Little Lagoon.
Sedimentation for the post construction scenario (Option 3H), appears to be marginally
higher in all cases, while total maximum erosion depths are very similar. This is attributable
to the larger sandbank providing increased surface area for erosion although the rate of
erosion may be equal.
4.3.2.5 Geotechnical Stability Analysis and Design Stable Slope Analysis
A geotechnical finite element analysis of the central sand bank has been undertaken using
the computer programme PLAXIS. Details of the analysis are provided in ZAA 1370‐RPT‐
041, Ref(10) in Annexure ‐2.
The analysis predicts that sandbank slopes of 1:4 will be stable, with an adequate factor of
safety. This has been confirmed by studying the existing central sandbank slopes, which
have a stable slope of 1:4.
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Figure 7: Section A‐A (Central Sandbank Slope) Analysis
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Figure 8: Section B‐B (Turning Basin Slope) Analysis
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Figure 9: Section E‐E (Western Scour Protected Slope) Analysis
In conclusion, slope stability analysis using PLAXIS 2D 2012 has been carried out for the
new and existing sandbank slopes through all the construction phases during reclamation of
the central sandbank. Analysis has been conducted within the framework of Eurocode 7
Design Approach 1. All slopes have been designed to ensure adequate factor of safety
against failure. A double anchored sheet pile wall ensures stability of the existing sandbank
during installation of the caisson quay wall forming the western wall of the basin.
4.3.2.6 Geotechnical Field Study to Select Sand for Construction of the Sandbank
Extension
Geotechnical investigations have been completed by ZAA in the proposed dredged basin
area, as reported in ZAA 1370‐RPT‐031 Soil Material Reclamation for the Central Sandbank.
The objectives of the investigations were to determine the composition and distribution of the
soils and their basic engineering properties including their consistency. An estimation of the
different material type volumes was then undertaken.
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The report presents the results of the investigations covering the entire area to be dredged,
but it also focuses on the properties, quantities and suitability of the soils in the dredge area
that could be used for construction of the sandbank extension.
The report makes use of extensive exploration, soils testing and expert evaluations from
earlier investigations in the dredge area, turning circle and central sandbank, in particular
those by the CSIR, Prestedge Retief Dresner Wijnberg Consulting Port and Coastal
Engineers (PRDW) and Hatch Mott MacDonald Goba JV (HMGJV).
The report is supplemented by ZAA 1370‐RPT‐004 Dredging Design and Survey report
which is relevant to the entire area to be deepened in the Durban Harbour during this
project.
4.4 Feasibility Study (FEL3) for the Deepening of Berths 203 to 205, Port of Durban –
Effects of Climate Change on Engineering Design (ZAA1370/RPT/028REVF) –
ZAA Engineering
4.4.1 Specialist
Specialist
Organisation: ZAA Engineering Projects and Naval Architecture (Pty) Ltd
Name: Dr John Zietsman
Qualifications: BSc (CivEng), UCT, MSc (Ocean Eng) University College London, PhD
University of London
No. of years experience: 39
Affiliations PrEng,
FSAICE,
MICE,
MRINA (overseas),
MSNAME,
FSAAE,
CEng
4.4.2 Main Findings
This section provides a summary of the effects of climate change on the engineering design.
The full report is contained in Appendix B3.
This report explains the basis of the approach that has been adopted in the Project Design
Premise to account for the effects of long term climate change on the marine engineering
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design of the proposed Berth 203 to 205 Berth Deepening Project at Pier 2 in the Port of
Durban. The report was originally produced in response to a query raised by an Interested
and Affected Party (IAP) during a public meeting which was part of the Environmental Impact
Assessment (EIA) process. The EIA process and the application for an Environmental
Authorisation (EA) to authorise the project are vital components of the planning and
execution of this upgrade project.
The report further addresses the issues raised by the Department of Environmental Affairs in
its letter Ref 14/12/16/3/3/2/275 signed on 21 October 2013 issued in response to the initial
EIA Report.
The report does not purport to be a research paper on the subject of climate change and sea
level rise (SLR). The report reviews and summarises the available literature relating to
parameters affected by climate change that are relevant to the marine engineering design for
this project.
The parameters listed below are those that can be affected by climate change and are
relevant to the marine engineering design. These parameters have been taken into
consideration in the design of the proposed quays and associated dredging works:
Long term sea level rise
Storm surge (wind setup, pressure deficit, wave setup)
Temperature
Wind (including tropical cyclones)
Currents
Waves
Rainfall
Ocean acidification
Various components of the design are affected by the above listed parameters. The report
summarises the impacts of the climate change affected parameters on the design of these
components. The various components affected are:
Selection of cope level for new quays - An important aspect of the design of a
quaywall is to establish a safe level for the top of the quaywall (the cope level).
This report explains how the design has more than adequately taken account of
sea level rise in terms of the reports published by recognised international
experts.
Structural design of new quay walls and quay furniture
Storm water management plan
Concrete design for durability
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4.4.2.1 Sea Level Rise
Sea level has changed greatly over history and reached a level of about 120 meters below
current sea level at the Last Glacial Maximum 19,000-20,000 years ago. Last Glacial
Maximum refers to a period in the Earth's climate history when ice sheets were at their
maximum extension, between 26,500 and 19,000–20,000 years ago, marking the peak of
the last glacial period. During this time, vast ice sheets covered much of North America,
northern Europe and Asia.
Melting of the ice sheets during the Holocene Period, (generally accepted to have started
approximately 12,000 years BP (before present day), caused sea levels to rise, but climate
has been fairly stable over the Holocene and the graph (Figure 3.1.1.1) indicates minimal
change over the last 4,000 years.
There has been approximately 0.17m of sea level rise in the 20th century and an
accelerating trend is predicted in the 21st century.
Comparisons between Sea Level Rise for Southern Africa (based on approximately 30 years
of South African tide gauge records) and global tide gauge records, show substantial
agreement with global trends (Mather, 2008). Linear and nonlinear sea-level changes at
Durban, South Africa have been reported on by A.A. Mather, (Coastal and Catchment
Policy, Co-ordination and Management, eThekwini Municipality), in which the tide records
between 1970 and 2003 for Durban, South Africa, have been analysed to determine the
extent of recent linear and nonlinear sea level trends in the light of predicted global sea-level
rise. The linear trends of monthly mean sea level revealed a sea level rise of 2.7 mm ± 0.05
mm / year and the yearly mean sea-level trend revealed a rise of 2.4 mm ± 0.29 mm / year.
Nonlinear trends varied between –1 mm and +8 mm / yr. These findings are similar to
recently published results of global sea level rise calculations over the last ten years derived
from worldwide tide gauge and TOPEX / Poseidon altimeter measurements, which range
between 2.4 mm and 3.2 mm / year.
It can thus be concluded that the local South African rate of Sea Level Rise falls within the
range of global trends and for long-term design purposes the global sea level rise projections
(refer to section 2.2.3 below) are directly applicable to South Africa. It is noted that an
analysis of tide gauge records around South Africa (Mater et al, 2009) revealed a minor
variation in regional sea level trends (west coast vs. east coast) however these are
considered relatively minor in comparison to uncertainties in the long term global predictions.
The IPCC Climate Change 2013 predictions for Global Mean Sea Level Rise to the year
2100 ranges from 0.26m to 0.82m for the various Representative Concentration Pathways
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(RCP) scenarios. For RCP8.5, the worst case scenario, a likely range of 0.45m to 0.82m is
predicted by 2100.
The upper bound predictions (both in terms of worst case scenario RCP and the upper
bound value within the RCP8.5 range), Climate Change 2013, Physical Science Basis,
Summary for Policy Makers, serves as the basis for design for this project. This is in
agreement with IPCC AR4 together with the scaled up ice sheet discharge, projected from
2095 to 2100.
The design life of the structures is until 2069 and using the 95% upper bound envelope, a
sea level rise value of 0.48m is predicted. Although the rate of change is expected to
increase over time, due to the uncertainties associated with the rate of increase and to be
conservative, we have assumed a linear increase between 1990 and 2100. Therefore a
value of 0.58m in 2069 has been conservatively adopted for the design criteria for the
project.
Figure 10: 1990 to 2100 sea level rise projections (after IPCC, 2001b; 2007b)2 with IPCC (2013)
Climate Change 2013, The Physical Science Basis, Summary for Policy Makers Ref (16) 0.82
metres at 2100
A sensitivity analysis has been undertaken investigating the probable water levels based on
climate change increases using 2100 increase predictions. Using a SLR of 0.79m and a
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storm surge value of 0.828m (based on a 20% increase due to climate change), the
maximum water level predicted is +4.205m CDP.
The figure below shows the present situation, where the cope level is at +3.72m CDP. This
figure shows that the current level allows for the full tidal range, waves and storm surge, as
well as 443mm of freeboard.
Figure 11: Existing Quaywall
The figure below shows the new design with a cope level of +4.25mCDP with the tidal range,
waves and predicted storm surge after completion of construction in the year 2019. The
freeboard at that time relative to the latter parameters is 973mm.
Figure 12: Post Construction – Year 2019
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The figure below shows how the new design with the cope level at +4.25m CDP deals with
the tidal range, waves, the predicted storm surge and sea level rise at the end of the design
life in the year 2069. At that time the freeboard will be approximately 324mm.
Figure 13: End of Structure Design Life – Year 2069
The figure below shows the situation in the year 2100, 31 years after the end of the design
life. The extreme water level at that time is due to sea level rise, tidal range, waves and
storm surge and the freeboard will be approximately 15mm.
Figure 14: Post Structure Design Life – Year 2100
At all times during construction of the new quays, which is estimated to take approximately 5
years, i.e. to about 2019, the old quays will remain in place and the new quays will be built in
front of them and to a level some 14% higher. The cope height of the existing quays at Pier 2
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is at +3.72 m CDP. This has proved to be entirely adequate for storm, wave and tidal
conditions since their construction some 60 years ago and it is predicted that they will remain
adequate during the construction life of the project.
Where there are currently no existing quays or in some small areas where the top of the
existing quays will be demolished, Pier 2 and its inland structures will be protected by sheet
piles while the new quays are constructed. There is thus no vulnerability or risk of flooding
during the construction period.
4.4.2.2 Wind
There is generally low confidence in predictions of future wind speed changes. Several
model studies have suggested increased average and/or extreme wind speeds but some
studies point in the opposite direction. The changes in both average and extreme wind
speeds may be seasonally variable, but the details of this variation appear to be model-
dependent. IPCC predicts that future tropical cyclones will likely become more severe with
greater wind speeds.
In response to growing awareness of disasters that can result from climate change, the
International Atomic Energy Agency (IAEA), released a safety guide in 2003 detailing flood-
related hazards to nuclear power plants on coastal and river sites. The safety guide
suggests that newly constructed plants should account for an increase in wind strength of
between 5-10 percent over the 100 year life span of a nuclear plant due to the effect of
climate change. This recommendation appears to be based more on the dire consequence
of the failure of a nuclear plant rather than based on a statistical and proven model.
Nonetheless it is deemed prudent to make allowance for a possible increase in wind
strength.
The upper bound recommendations from the IAEA have been adopted for this project,
namely a 10% increase in wind strength over a 100 year life span. The design life of this
project is 50 years therefore a 5% increase in wind strength has been allowed for in this
project over and above the residual 1:50 year wind speed.
4.4.2.3 Storm Surge
Storm surge is an abnormal rise of water generated by a storm, over and above the
predicted astronomical tides. Storm surge is produced by water being pushed toward the
shore by the force of the winds moving cyclonically around the storm (wind set up) together
with the low barometric pressure associated with intense storms causing a rise in sea water
level. The US National Weather Service, who have records of extreme storm surge events,
state that the wind setup component is the primary component accounting for 95% of the
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total storm surge with the low pressure component accounting for only 5% of the storm
surge.
Both the wind setup component and the low pressure component are a factor of the wind
speed. The wind setup is proportional to the square of the wind speed i.e. (wind speed)2,
whilst the low pressure component is directly proportional to the wind speed.
As stipulated in section 2.1 above, the design approach has been to first determine a current
residual value for storm surge based on a statistical analysis of historic data, and then
increase this value to account for climate change.
PRDW, 2003, analysed the tide records for the Port of Durban for the period 1972 to 2001
and compared these with astronomical tide predictions, the difference between the two
giving the storm surge value. A statistical analysis on these results revealed an increase in
tide level of 0.69m for a 1:100 year storm surge event. Although the project design life is 50
years, the 1:50 year event value is not available and we have therefore conservatively
adopted the 0.69m value as the residual value for storm surge.
To calculate the effect of climate change ZAA have used the 5% increase in wind speed as
explained in section 2.3.2 above and applied this percentage to the components affecting
storm surge.
Increase in storm surge = (1.05)2 * 0.95 (Wind setup) + 1.05 * 0.05 (Low pressure) = 1.1
Therefore a 10% increase is applied to the residual storm setup value.
i.e. Design criteria storm setup value = 0.69 x 1.1 = 0.759 m
4.4.2.4 Temperature
Future downscaled projections for changes in temperature are available for the Durban
region. According to the Durban 2010/2011 Municipal Climate Protection Programme report,
downscaled projections “suggest that an increase of 1.5-2.5 °C in mean annual temperature
by 2045-2065”. The projections are summary values produced by the University of KwaZulu-
Natal and presumably informed by the IPCC AR4 GCM data.
4.4.2.5 Rainfall
Short duration design rainfalls and their relative intensity (mm/hr) are relevant to the design
of the storm water management system for the project. The frequency of these storms is of
less relevance to the design of the storm water management system.
Limited information is available on the predicted increase in rainfall intensity in the Durban
area. Statistically downscaled data for precipitation is generally regarded as less reliable
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than that for temperature. The Durban 2010/2011 Municipal Climate Protection Programme
report that “Rainfall is likely to increase slightly overall, but this rainfall will fall over shorter
time periods, which means that streamflows will be higher and faster”.
The recently released “Durban Climate Change Strategy - Water Theme Report: Draft for
Public Comment, January 2014” recommends increasing designs by 10% or even more as a
precaution against increased extreme events under future climatic conditions.
4.4.2.6 Ocean Acidification
Ocean acidification is the term given to the decrease in the pH of the Earth's oceans, caused
by the uptake of anthropogenic carbon dioxide (CO2) from the atmosphere. As CO2
dissolves into the oceans, rivers and lakes, some of it reacts with the water to form carbonic
acid. The potential impact of this acidification on the concrete quay wall has been examined.
4.4.2.7 Risk and Mitigation Summary
This report has reviewed and summarised available literature on parameters affected by
climate change that are relevant to the marine engineering design for this project. The IPCC,
(2013) Climate Change 2013, has been adopted as the primary reference for this report.
This is in agreement with IPCC AR4 (2007), together with the scaled up ice sheet discharge
allowance, projected from 2095 to 2100. This has been supplemented by guidelines
produced by UK Climate Projections Report June 2009 (UKCP09) and the National
Committee on Coastal and Ocean Engineering, Engineers Australia. A Bibliography is
contained in the Annexure.
This report clearly demonstrates that the chosen cope level of +4.25m CDP is sufficient,
providing a freeboard of 0.324m over and above the allowed for accumulation of various
upper bound increases for climate change affected parameters.
This indicates clearly that the risks and vulnerability of the new quays to climate change, and
in particular sea level rise and storm surge, have been minimised and that the selected cope
height of 4.25 m originally proposed by Transnet for this project is safe, conservative for its
design life of 50 years from the projected completion date of 2019 and that a safe freeboard
will still exist. In fact, given the year 2100 projection values, the structure is likely to be safe
for a further 32 years after 2069. In all cases this is in the event of the simultaneous
occurrence of all factors affecting the water level in the Port.
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Various improbable extreme scenarios (e.g. UKCP09 H++) have been taken into account
when evaluating the design in terms of contingency planning in the event of these extreme
scenarios.
Other climate change affected parameters such as wind, rainfall and ocean acidification
have been taken account during the design of the quay structures, storm water system and
concrete specification.
The threat of flooding during the construction phase has been evaluated and we conclude
that construction will not adversely affect the current levels or increase the risk or
vulnerability to flooding.
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5 SUMMARY OF RESPONSES PROVIDED
5.1 Central Sandbank
Table 4: Summary of Comments and Responses
Comment from DEA Response
What are the baseline
and thresholds of
acceptable change
against which
monitoring will take
place?
The approach to be adopted for assessing the rate of recovering of the
newly created portion of the Central bank and for determining when this
area can be considered to be fully recovered is known as the test for
bioequivalence and was developed by researchers in New Zealand -
McDonald & Erickson (1994). The approach is to define two areas to be
bioequivalent if the mean density of a particular organism or organisms at
suite of impacted sites (the newly created sandbank) exceeds a
predefined percentage (in this case 80%) of the mean density at a
reference or control sites (on the existing sandbank area) for a defined
time interval (in this case 2 years). Conversely, a site is said to be
impacted or disturbed until the selected variable(s) exceed(s) the
predefined level over a defined time interval. This procedure was
developed for testing the equivalence of drugs (Kirkwood 1981, Westlake
1988) but has since been adopted for other biological sciences as well
(Dixon & Garret 1992, McDonald & Erickson 1994). Full details of the test
are contained in McDonald & Erickson (1994).
The predefined percentage is necessarily site- or situation-specific, but the
value of 80% seems to have attained fairly wide acceptance (McDonald &
Erickson 1994, Underwood 1996). Similarly, the number of successive
intervals over which this value should be achieved is site- and situation-
specific but also depends on the sampling interval. Transnet is in the
process of establishing an ecological baseline for the central sandbanks
and will monitor recovery of the extension to these banks until such time
that recovery can be deemed complete in terms of the test for bio-
equivalence described above. The baseline assessment will be conducted
over a period of 12 months and will focus on the following components:
Physico-chemical (habitat) variables
Total Suspended Solids (TSS)
Salinity
Temperature
Dissolved Oxygen;
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Comment from DEA Response
Sediment grain size distribution
Organic carbon content
Trace metal content in sediment (Cd, Hg As, Cr, Cu, Pb, Ni, Zn)
Faunal and floral assemblages
Benthic microalgae (microphytobenthos)
Benthic macrofauna
Fish
Birds
Baseline water quality characteristics will be established by taking water
quality measurements at a suite of 20 stations distributed in the navigation
channel adjacent to Berth 203-205 and in the main channel of the port
adjacent to the central sand bank. This will include a number of control
stations that will serve as reference stations in the future that will be
located outside of the influence of the proposed project activities (piling,
dredging, and sandbank construction). Daily water quality measurements
(salinity, temperature, dissolved oxygen and turbidity) will be taken at high
tide with a hand-held water quality meter (Hach HQ40d) at the surface and
bottom over a five day period each season (autumn, winter, spring,
summer) (total of 800 measurements over 12 months).
Baseline sediment characteristics will be established through collection of
sediment samples from 50 stations (10 supratidal, 20 intertidal and 20
subtidal) distributed on top and sides of the existing Centre bank in the
Port of Durban on four occasions (autumn, winter, spring, summer) over
the course of one year. Intertidal samples will be collected with a hand
corer (10 cm diameter) and subtidal samples collected with a Van Veen
grab. Samples will be placed in sampling jars on ice immediately after
collection and submitted to an SANAS accredited analytical laboratory for
determination of grain size distribution, organic and trace metal (Cd, Hg
As, Cr, Cu, Pb, Ni, Zn) content.
The baseline assessment for benthic microalgae biomass will be
undertaken through collection and analysis of sediment samples from the
same stations as for the sediment monitoring activities in accordance with
methods prescribed by Pinckney & Zingmark (1993). Sediment cores will
be taken by slowly inserting a plastic pipe of known diameter (≈20 mm),
either directly into the sediment (in the case of the intertidal samples) or
into the contents of the grab (in the case of the subtidal samples) down to
a depth of 40 mm. The top of the pipe will then be plugged with a bung
and a spatula inserted under the bottom of the tube, before it is slowly
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withdrawn from the sediment. Samples will then be placed in sampling
jars on ice, protected from light, and submitted to an analytical laboratory
where microalgae biomass will be estimated as total chlorophyll (Chl a)
according to the methods of Whitney & Darley (1979), Dandonneau &
Neveux (2002) and Seuront & Leterme (2006).
The baseline assessment for benthic macrofauna characterisation will be
undertaken through collection and analysis of macrofauna samples from
the same stations as for the sediment monitoring activities. Samples will
be collected at four occasions over the year (autumn, winter, spring,
summer). Intertidal samples will be collected at spring low tide by inserting
a large (18 cm diameter) corer into the sediment to a depth of 30 cm,
plugging the open end, extracting the core and transferring the contents to
a 1 mm mesh bag. The mesh bag will be agitated until all the fine
sediment has been removed and the remaining contents placed in a
sample jar together with 5% formalin. Subtidal samples will be collected at
corresponding times (autumn, winter, spring, summer) using a Van Veen
grab deployed from a small inflatable boat. In all cases, macrofauna from
the samples will be extracted from the residual sediment in the lab,
identified to species level, counted and weighed (wet weight).
The baseline assessment of fish populations along the margins of the
centre bank will be undertaken using a 30 m beach seine net with 12 mm
stretched mesh. At least five hauls will be made on either side of the
centre bank on four occasions during the year (autumn, winter, spring,
summer). All fish and invertebrates collected in the net will be
enumerated, weighed and measured, and if possible, returned to the sea
alive.
The baseline assessment of birds utilising the centre bank will entail
counting all birds present on the Centre Bank once a month for 12 months
over spring-low tide periods. Numbers of birds of each species will be
recorded within a series of belt transects spanning the centre bank. These
belt transects will be oriented parallel to the shoreline of Centre Bank
along its southern and northern edges to form a series of blocks which will
extend from the waters’ edge up to the middle of Centre Bank. Counts will
be conducted with the aid of binoculars and telescope within a six hour
period.
Standard univariate and multivariate techniques will be used to describe
baseline characteristics for the benthic macrofauna, fish and bird
communities both in terms of abundance and biomass (fish and
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macrofauna only). Univariate measurements will include total species,
species diversity, evenness and richness for intertidal and subtidal areas
and for each season and for the entire baseline period under assessment.
Multivariate analyses will employ techniques used in Plymouth Routines in
Multivariate Ecological Research (PRIMER) (Clarke and Warwick 2001),
specifically non-metric multidimensional scaling and cluster analyses, k-
dominance curves and an analysis of the characteristic and distinguishing
species (SIMPER) of macrofauna and fish at Centre Bank.
Once construction of the new sections of the central sandbank are
complete, monitoring of the recovery of this area will commence and will
be conducted in the same manner as for the baseline assessment. The
rate of recovery will be assessed in accordance with the test of
bioequivalence as described above. Monitoring will continue until such
time that the mean density of organisms in each of the above groups
(microalgae, macrofauna, fish, and birds) on the newly created sandbank
area is at least 80% of the mean density on the existing sandbank area,
averaged over a period of two years.
In addition to this, the following water quality parameters will be monitored
at a depth of 2 m at at least three stations along the southern edge of the
Centre Bank and at at least one station in Little Lagoon during the
construction (dredging) phase of the project:
Total Suspended Solids (TSS)
Salinity
Temperature
Dissolved Oxygen
Data from the turbidity monitoring instruments will be available in real time
to the person coordinating dredging activities.
What actions are
proposed should the
monitoring results
detect change?
The following actions are proposed to mitigate impacts of dredging
(suspension of silt) on Durban Bay:
Installation of ‘Silt Curtains’ at the dredge burrow pit during
dredging to contain turbidity levels in the surrounding waters. The
lower end of the ‘skirt’ of the silt curtains will rest upon the
seafloor, and the top of the ‘skirt’ will be kept be above the water
surface.
The dredge hopper overflow will be choked with a fully-automated
computerized process controller that can ensure dynamic
adjustment of the valve in the overflow funnel which chokes the
flow in such a way that a constant fluid level in the hopper is
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maintained and, as a result, no air is taken down with the
suspension leaving the hopper. This has been shown to
significantly decrease turbidity in the surrounding waters.
Minimise the time period over which the dredging operation is to
take place, to avoid the daily re-suspension of sediments.
If, in spite of these mitigation measures, turbidity levels exceed a threshold
level of 50 mg/l-1 at any of the monitoring stations referred to above,
during the dredge operations, the following actions will be implemented:
Dredging operations will be halted immediately and will not
recommence until levels have declined below threshold levels.
What are the socio-
economic and
ecological implications
should the proposed
mitigation measure
prove unsuccessful?
In the event that the proposed mitigation measures (construction of
additional sandbank area on the Central sandbank) prove unsuccessful,
the proposed development will result in the net loss of approximately 6%
of the existing intertidal area on the Centre Bank area or 3% of the total
existing intertidal-sand flat area in Durban Bay. However, it must be
recognised though that intertidal-sand-flat habitat in the Port of Durban has
already been reduced to only 14% of its original extent (Allan et al. 1999).
Thus, the remaining intertidal sand flat area is recognised as being
extremely important to the ecological functioning of the Port of Durban
(Newman et al. 2008; Weerts 2010). These banks are considered to be
very important for birds, juvenile fishes, and invertebrate populations in the
Bay and indeed the region as a whole (Day & Morgan 1956; Cyrus &
Forbes 1996; Forbes et al. 1996, McInnes et al. 2005, Weerts 2010). Any
further loss of this habitat type must be avoided or effectively mitigated.
It is not possible to quantify the precise ecological or socio-economic
implications of the loss of this habitat area should the mitigation measures
prove unsuccessful. The reason for this is two-fold. One the one hand it
can be argued that the newly created sandbanks may not as good as the
existing habitat area and thus will result in a proportional loss (up to a
maximum of 3%) in habitat for invertebrates, fish and birds populations in
the Bay as a whole. One the other hand it could be argued that any loss in
habitat area could result in a disproportionately large impact on populations
of affected species owing to the fact that this type of habitat (intertidal and
shallow subtidal sandbank) has been so severely reduced within the Port
of Durban already, that the affected species may be close to some sort of
tipping point which could result in a much larger reduction in their
population size. For example, McInnes et al. (2005) argue that “potentially
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half the waterbird population of Durban Harbour could be negatively
impacted as a result of any modification of [the central sandbank].” This,
they argue, is because the intertidal sand banks play a critical role in
providing food in the form of invertebrates (macrofauna) to many bird
species.
It is the opinion of the marine specialists on the project team that the based
on evidence from previous attempts of this nature (both in the Port of
Durban and elsewhere) that the likelihood of successfully replacing habitat
lost through this development is good and hence ecological and socio-
economic costs are likely to be low or even negligible.
All the potential risks
and mitigation
measures associated
with the creation of the
Portion of Central
Sandbank as a
mitigation measure
must therefore be fully
assessed and be
addressed in the
amended report.
It is not possible to directly assess potential risks and mitigation measures
associated with the creation of the portion of the Central Sandbank without
relevant experimental evidence which is not feasible or even permissible in
this instance. However, it is possible to assess the potential risks and
mitigation measures indirectly through sophisticated computer simulation
modelling (as has been performed by both the CSIR and ZAA Engineering
projects and Naval Architects (Pty) Ltd as part of this EIA) and through
comparison with similar initiatives that have been undertaken elsewhere.
We were also able to collect a good deal of indirect evidence pertaining to
the likely success or failure of the mitigation measures proposed in this
study in respect of ecological recovery by reviewing available evidence in
the international literature. The results of this review suggest very strongly
that the likelihood of success is high and that faunal colonisation (by
macroinvertebrates at least) is likely to take place in a fairly short space of
time (months to years rather than decades). Summary information on
eight case studies from estuaries or shallow water marine systems are
presented below:
Evens et al. (1998) investigated the recolonisation of an existing
intertidal mudflat by macroinvertebrates and birds in the Tees
Estuary, England following restoration of tidal inundation. He
reported that a stable macroinvertebrate population had developed
after a period of 3 years. The actual success of restoring the
mudflats, however, could not be evaluated as no baseline data
were available prior to tidal inundation ceasing for comparative
purposes.
Ray (2000) reported on creation and colonisation of an artificial
mudflat made of dredge spoil on the coast of Maine, USA. In this
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instance an artificial mudflat was created and its macroinvertebrate
community assessed and compared to an adjacent reference site
over a period of five years. The study found that diverse and
complex infaunal assemblages were able to establish themselves
on the mudflats constructed of dredged materials, and that within
three years the communities on constructed flats resembled those
on the natural flats.
Brooks (1983) reported on colonisation of dredged sediments on a
dredge spoil disposal site located at 20 m depth in Long Island
Sound. He found that three months after final capping of the
disposal site the numbers of benthic macrofauna individuals and
species present and were “roughly comparable” to those at the
reference stations and that after 15 months the number of
macrofauna individuals and species were significantly higher than
reference sites and in the predisposal reference collections.
Bolam & Whomersley (2005) reported on changes in physical
parameters and recovery of benthic macrofauna in dredge spoil at
three beneficial use schemes in estuaries in south-east England.
They found that environmental parameters (sediment redox
potential, and water, organic carbon and silt/clay contents) and
univariate community attributes (total individuals and species,
diversity, evenness and biomass) had attained reference levels at
two schemes but that assemblages differed significantly in terms of
species composition at all three schemes. (Note our concern
though with this approach articulated above)
Bolam et al. (2004) found that recolonisation of 1 m2 of defaunated
sediments resulted in recovery of univariate indices after only three
months and community structure after 6–12 months on a mudflat
in south-east England.
Beukema et al. (1999) reported that number of species and
individuals took 6 and 12 months to recover, respectively, following
the defaunation of larger areas (120 m2) of mudflat in the Dutch
Wadden Sea.
Vogt (2010) reported on experimental restoration of the Big Egg
Marsh in Jamaica Bay, New York City harbour. He reported on
recovery of salt marsh vegetation and macrofauna on artificial
islands constructed from dredge spoil. He found that the project
was a success in that the dredge spoil had been successfully
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transforming into a silty and organic saltmarsh soil, that a dense
cover of smooth cordgrass had developed on the islands, and that
an “appropriate” animal community had become established.
Bolam and Whomersley (2004) found that the diversity, abundance
and species richness of two mudflat communities created from
dredged material near Jonesport, Maine, had re-established the
levels found at reference mudflats after two years.
Literature on the impacts and colonisation of offshore (deepwater) dredge
spoil disposal areas provides a similar perspective. Studies in the OSPAR
maritime area (North-East Atlantic) for example, indicate recovery rates for
species richness, abundance and diversity amongst macrofaunal
communities to range from 3 months to 2 years (Stronkhorst et al. 2003;
Bolam and Rees, 2003; CEFAS, 2005; Bolam et al. 2006a; b; Bolam &
Whomersley 2005; Van Dalfsen & Lewis 2006).
Risks and Mitigation Measures determined as part of ZAA Engineering
(2014a) are provided below:
High Turbidity and Total Suspended Solids (TSS) during dredging and
placement of sand bank extension
Mitigation:
Hydrodynamic and morphological analyses of dredging operation
have been carried out to determine whether the turbidity and TSS
concentration levels will be significant. The numerical model has
been set up using the Delft3D suite of tools to simulate the
interaction between the following processes: water level variation
due to tides, flow patterns within the port, wind and waves. The
approach adopted in the study has been to compare the
conditions at and near the seabed before, during and after
completion of the works, including : dredging in the harbour and
offshore; offshore disposal; construction of new quay structures
and scour protection.
Bed shear stresses and suspended solids concentrations have
been used to evaluate the hydrodynamic impacts during and after
completion of the works, compared with the present conditions.
The results of the study indicate that there will be no significant
negative impacts during or after completion of the works, either to
the main sandbank within the Port or to the beaches and coastline
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outside the Port, compared to the status quo.
Special dredging equipment or procedures will be implemented to
reduce turbidity levels. It is anticipated that turbidity levels during
and after dredging and dumping will be less than the accepted
medium to low risk levels.
The turbidity and TSS are closely monitored during the dredging
process and dredging is temporarily suspended if turbidity and
TSS are close to the safe upper bound levels specified in the
Dredging Contract.
The dredge monitoring procedure used has been tested and
proven through use in the Cape Town berth deepening project in
the Ben Schoeman Dock.
Allowance has been made in the Dredging Contract Schedule to
cater for delays due to turbidity control.
The upper bound turbidity levels specified in the contract are
levels that are safe for all marine life.
Dredging operations cause sand bank to slip at the Berth 205 extension
end and the existing sandbank and the Little Lagoon area is damaged
Mitigation:
A sheetpile wall is designed and installed to international
standards.
Geotechnical and structural Finite Element analyses using PLAXIS
have been undertaken and these confirm that the design sheetpile
wall will provide the necessary stability to the existing Central
Sandbank.
Anchor pull‐out tests are being carried out to ensure that the
parameters assumed in the design of the sheet piling are safe and
realistic. The parameters being used are based on other recent
anchor pull‐out tests.
Scour protection has been designed to and will be installed in
compliance with international accepted standards.
Dredging operations cause sandbank extension to slip and the existing
Central Sandbank is damaged.
Mitigation:
The sandbank extension is designed with slopes not exceeding
existing stable slopes.
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Geotechnical Finite Element analyses have been undertaken to
ensure that the slopes of the sandbank extension is stable.
The sand bank extension is constructed using the approved
Method Statement and is supervised to ensure that the extension
slopes will remain stable during construction. The method of
construction includes the use of baffle walls and berms to prevent
any slippage during construction.
If a local slip does occur it is repaired using normal maintenance
dredging.
The sandbank extension has been designed so that the existing
Central Sandbank will not in any way be affected by a slip of the
extension during or after construction.
High swell conditions at sea Delay in dredging schedule during
construction
Mitigation:
Allow for schedule delays in construction programme.
Obtain regular weather reports and plan accordingly.
Damage to Central Sand Bank extension due to Climate Change resulting
inter alia in changes in sea level and increase in frequency and severity of
storm surge. Extension is eroded more than existing sandbank would have
been and/or slips into dredged basin and large amounts of sand deposited
in dredged basins and channels
Mitigation:
Hydrodynamic and morphological analyses of anticipated severe
storms and variations in sea level have been carried out to
demonstrate that the stability of the sandbank extension will be at
least equal to that of the existing sandbank. The numerical model
has been set up using the Delft3D suite of tools to simulate the
interaction between inter alia the following processes: water level
variation due to changes in sea level caused by climate change,
storm surges and tides, flow patterns within the port, wind and
waves. Extreme wind velocities have been increased by a factor of
10% over current extreme levels.
If the sandbank is damaged, or a slip occurs, it is repaired during
maintenance dredging.
Extension has been designed so the existing Central Sandbank
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cannot be damaged due to damage of the sandbank extension.
Damage to Central Sandbank extension due to inclement weather, wind,
waves, currents and storm surge. Extension slips into dredged basin and
large amounts of sand deposited in dredged basins and channels
Mitigation:
Perform numerical simulations to Dredge material out of the basin
and repair damaged area. Central Sand Bank
and Little Lagoon area protected by sheetpile wall during
construction and by caissons after construction.
Contract dredging procedures specify the limits of weather
conditions for dredging activities.
If a slip occurs it is repaired during maintenance dredging.
Extension has been designed so the existing Central Sandbank
cannot be damaged by damage to the sandbank extension.
Consideration must be
given on how realistic
and practical the
mitigation measure is
and hat costly
commitment and
assurances have been
provided by the
applicant.
The risk assessment (above) shows that with mitigation nearly all risks are
reduced to ‘unlikely’ and ‘minor’. In addition the following should be noted:
Modelling of the Central Sandbank Extension stability shows that
comparing for all scenarios, it may be seen that in each case,
there are no discernable differences in erosion and depositional
trends for the sandbank or the Little Lagoon. Sedimentation for the
post construction scenario (Option 3H), appears to be marginally
higher in all cases, while total maximum erosion depths are very
similar. This is attributable to the larger sandbank providing
increased surface area for erosion although the rate of erosion
may be equal. A simulation omitting any wind and wave effects
reveals that close to zero erosion takes place over the sandbank.
A geotechnical finite element analysis of the central sand bank has
been undertaken using the computer programme PLAXIS. Details
of the analysis are provided in ZAA 1370‐RPT‐041. The analysis
predicts that sandbank slopes of 1:4 will be stable, with an
adequate factor of safety. This has been confirmed by studying the
existing central sandbank slopes, which have a stable slope of 1:4.
Hydrodynamic and morphological analyses of the Port of Durban
using DELFT‐3D to determine the short and long term stability and
form of the extended sandbank, including the effects of wave
penetration, wind and currents due to tidal movements and other
effects. These studies indicate that the extended sandbank will be
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Comment from DEA Response
stable and that it will not endanger the stability of the existing
sandbank during construction, or during operation of the container
terminal. It also indicates that flows will not change in the area of
the Little Lagoon and this, combined with the sheet pile protection
to be installed, will ensure that the Little Lagoon is not disturbed.
Hydrodynamic analyses have been carried out to assess the levels
of turbidity and total suspended solids (TSS) that will result from
the dredging operations and the studies have confirmed that levels
will be within acceptable limits.
Geotechnical finite element analyses have been carried out using
the computer programme PLAXIS to ensure the stability of the
sandbank extension.
An extensive on site geotechnical investigation (involving Cone
Penetrometer Testing with pore water pressure data (CPTu) and
proof drilling and logging) has been carried out to determine the
nature and suitability of the sands that will be dredged from the
basin, for use in the construction of the sandbank extension.
Comprehensive dredging analysis and design has been carried
out.
Gaps, uncertainties and
assumptions must
clearly be reported.
Gaps and uncertainties have been provided in each specialist report.
Long Term Maintenance
burden must be
considered.
Modelling of the Central Sandbank Extension stability shows that
comparing for all scenarios, it may be seen that in each case, there are no
discernable differences in erosion and depositional trends for the sandbank
or the Little Lagoon. Sedimentation for the post construction scenario
(Option 3H), appears to be marginally higher in all cases, while total
maximum erosion depths are very similar. This is attributable to the larger
sandbank providing increased surface area for erosion although the rate of
erosion may be equal. A simulation omitting any wind and wave effects
reveals that close to zero erosion takes place over the sandbank. Based
on this there is no long term maintenance burden in regards to the Central
Sandbank (maintenance dredging as part of Port operations will be
required).
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5.2 Climate Change Issues
Comment from DEA Response
Climate Change Risks
such as sea level rise
and storm surges must
be addressed.
The parameters listed below are those that can be affected by climate
change and are relevant to the marine engineering design. These
parameters have been taken into consideration in the design of the
proposed quays and associated dredging works:
Long term sea level rise
Storm surge (wind setup, pressure deficit, wave setup)
Temperature
Wind (including tropical cyclones)
Currents
Waves
Rainfall
Ocean acidification
Various components of the design are affected by the above listed
parameters. The report summarises the impacts of the climate change
affected parameters on the design of these components. The various
components affected are:
Selection of cope level for new quays - An important aspect of
the design of a quaywall is to establish a safe level for the top
of the quaywall (the cope level). This report explains how the
design has more than adequately taken account of sea level
rise in terms of the reports published by recognised
international experts.
Structural design of new quay walls and quay furniture
Storm water management plan
Concrete design for durability
A Climate Change Risk
and Vulnerability
Assessment to
adequately address
how sea level rise and
coastal storm surges
will be addressed during
construction and
operational phase of the
proposed development.
Risk and vulnerability has been taken into account in the engineering
design. Please see Chapter 5.4 and Appendix B3 for more detail.
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Comment from DEA –
22 April 2014
Response
Information regarding
climate risks, sea level
rise impacts and storm
surges must be
included in the report.
Information regarding climate risks including the following parameters
were included in the Effects of Climate Change on Engineering Design
Report:
Long term sea level rise
Storm surge (wind setup, pressure deficit, wave setup)
Temperature
Wind (including tropical cyclones)
Currents
Waves
Rainfall
Ocean acidification
A summary of the report can be found in Chapter 5.4. The full study is
contained in Appendix B3.
Mitigation measures to
be provided.
Mitigation measures were summarised in Chapter 5.4. and are contained
in Appendix B3. In addition, Risks and Mitigation Measures determined as
part of ZAA Engineering (2014a) are provided below:
High Turbidity and Total Suspended Solids (TSS) during dredging and
placement of sand bank extension
Mitigation:
Hydrodynamic and morphological analyses of dredging operation
have been carried out to determine whether the turbidity and TSS
concentration levels will be significant. The numerical model has
been set up using the Delft3D suite of tools to simulate the
interaction between the following processes: water level variation
due to tides, flow patterns within the port, wind and waves. The
approach adopted in the study has been to compare the
conditions at and near the seabed before, during and after
completion of the works, including : dredging in the harbour and
offshore; offshore disposal; construction of new quay structures
and scour protection.
Bed shear stresses and suspended solids concentrations have
been used to evaluate the hydrodynamic impacts during and after
completion of the works, compared with the present conditions.
The results of the study indicate that there will be no significant
negative impacts during or after completion of the works, either to
the main sandbank within the Port or to the beaches and coastline
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outside the Port, compared to the status quo.
Special dredging equipment or procedures will be implemented to
reduce turbidity levels. It is anticipated that turbidity levels during
and after dredging and dumping will be less than the accepted
medium to low risk levels.
The turbidity and TSS are closely monitored during the dredging
process and dredging is temporarily suspended if turbidity and
TSS are close to the safe upper bound levels specified in the
Dredging Contract.
The dredge monitoring procedure used has been tested and
proven through use in the Cape Town berth deepening project in
the Ben Schoeman Dock.
Allowance has been made in the Dredging Contract Schedule to
cater for delays due to turbidity control.
The upper bound turbidity levels specified in the contract are
levels that are safe for all marine life.
Dredging operations cause sand bank to slip at the Berth 205 extension
end and the existing sandbank and the Little Lagoon area is damaged
Mitigation:
A sheetpile wall is designed and installed to international
standards.
Geotechnical and structural Finite Element analyses using PLAXIS
have been undertaken and these confirm that the design sheetpile
wall will provide the necessary stability to the existing Central
Sandbank.
Anchor pull‐ out tests are being carried out to ensure that the
parameters assumed in the design of the sheet piling are safe and
realistic. The parameters being used are based on other recent
anchor pull‐ out tests.
Scour protection has been designed to and will be installed in
compliance with international accepted standards.
Dredging operations cause sandbank extension to slip and the existing
Central Sandbank is damaged.
Mitigation:
The sandbank extension is designed with slopes not exceeding
existing stable slopes.
Geotechnical Finite Element analyses have been undertaken to
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ensure that the slopes of the sandbank extension is stable.
The sand bank extension is constructed using the approved
Method Statement and is supervised to ensure that the extension
slopes will remain stable during construction. The method of
construction includes the use of baffle walls and berms to prevent
any slippage during construction.
If a local slip does occur it is repaired using normal maintenance
dredging.
The sandbank extension has been designed so that the existing
Central Sandbank will not in any way be affected by a slip of the
extension during or after construction.
High swell conditions at sea Delay in dredging schedule during
construction
Mitigation:
Allow for schedule delays in construction programme.
Obtain regular weather reports and plan accordingly.
Damage to Central Sand Bank extension due to Climate Change resulting
inter alia in changes in sea level and increase in frequency and severity of
storm surge. Extension is eroded more than existing sandbank would have
been and/or slips into dredged basin and large amounts of sand deposited
in dredged basins and channels
Mitigation:
Hydrodynamic and morphological analyses of anticipated severe
storms and variations in sea level have been carried out to
demonstrate that the stability of the sandbank extension will be at
least equal to that of the existing sandbank. The numerical model
has been set up using the Delft3D suite of tools to simulate the
interaction between inter alia the following processes: water level
variation due to changes in sea level caused by climate change,
storm surges and tides, flow patterns within the port, wind and
waves. Extreme wind velocities have been increased by a factor of
10% over current extreme levels.
If the sandbank is damaged, or a slip occurs, it is repaired during
maintenance dredging.
Extension has been designed so the existing Central Sandbank
cannot be damaged due to damage of the sandbank extension.
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Damage to Central Sandbank extension due to inclement weather, wind,
waves, currents and storm surge. Extension slips into dredged basin and
large amounts of sand deposited in dredged basins and channels
Mitigation:
Perform numerical simulations to Dredge material out of the basin
and repair damaged area. Central Sand Bank
and Little Lagoon area protected by sheetpile wall during
construction and by caissons after construction.
Contract dredging procedures specify the limits of weather
conditions for dredging activities.
If a slip occurs it is repaired during maintenance dredging.
Extension has been designed so the existing Central Sandbank cannot be
damaged by damage to the sandbank extension.
5.3 Re-use of Dredge Material
Comment from DEA –
22 April 2014
Response
Re-use of dredging
material is international
best practice. The
report should provide
examples and
references thereof.
The Ecological Risk Assessment found that in other parts of the world tidal
sand- and mudflat creation and restoration initiatives have been
undertaken with the expressed purpose of increasing this valuable habitat
type; e.g. USA (Levin et al. 1996, Ray, 2000), UK (Evans et al. 1998),
Japan (Lee et al. 1998; Ishii et al. 2008) and Australia (French et al. 2004).
In many cases this has involved the use of dredged materials. The
beneficial use of dredge spoil for use to create habitat is well established
and has been proved to successfully used invertebrates, fishes and bird
fauna. Indeed, the beneficial use of dredge spoil rather than disposal at
sea is widely regarded as best management practise for dredge spoil
disposal. This has long been realised and reported upon in the scientific
literature (Rhoads et al. 1978, Bolam and Whomersley 2003, 2005, Bolam
and Rees 2003, Yozzo et al. 2004).
Further, successful Habitat Creation/Restoration using dredged materials
has occurred in USA in the following locations:
Polar Island, Maryland
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Lake Worth, Florida (Munyon Island, Peanut Island, Snook Island
and Johns Island)
Sonoma Baylands, San Fransico Bay, California
Deer Island, Mississippi
Craney Island, Virginia
Port Fourchan, Louisiana (Maritime Forest Ridge in Bayous
Cochon and Moreau and Baoyou DuPont Ridge)
Tennessee - Tennessee‐Tombigbee Waterway, Mississippi
Mobile Battleship Park, Alabama
Galveston Bay, Texas
Big Egg Marsh, New York Harbour
Jamaica Bay Marsh Islands, Brooklyn New York (Elders Point East
Marsh and Elders Point West Marsh)
Successful Brownfields Restoration has taken place at the following
locations in USA
Runyan Shipyard Penscola, Florida
New Jersey:
o Riverwinds Golf Course on Delaware Bay
o Prologis Port Reading Business Park
Flushing Airport, New York,Wetlands Brownfield Restoration
White Island, Brownfield Restoration
Fort Mifflin, Pennsylvania
Bark Camp Demonstration Project, Pennsylvania
Maple Beach area of Bristol Township, Bucks County, PA.
Dream Park, Logan Township, Gloucester County, New Jersey
A list of references is provided below.
1. Eurosion Case Study, Essex Estuaries (United Kingdom),
Colcester Borough Council, EUCC, 2003
2. Beneficially Using Dredged Materials to Create/Restore Habitat
and Restore Brownfields, and Team Collaborative Efforts that have
Achieved Success: Examples/Case Studies, Craig Vogt, May 2010
3. Development of Macrofaunal Communities on Dredged Material
Used for Mudflat Enhancement: a Comparison of Three Beneficial
Schemes after One Year, S.G. Bolam, P Whomersly, Marine
Pollution Bulletin, Elsivier, 2004
4. PIANC Working Group 1 1998: Management of Aquatic Disposal
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of Dredged Material
5. PIANC Report No 104 – 2009 Dredged Material as a Resource
Consideration must be
given to the chemical
pollutants of the dredge
material.
Potential impacts associated with elevated suspended sediment
concentrations in the water column and toxicity of heavy metals,
hydrocarbons and polychlorinated biphenyls were also assessed. The
findings showed that the concentrations of metals and organic chemicals
in sediment within and near the dredge footprint were very low and thus
there was a very low probability that chemicals released during the
dredging process would be present in the water column at toxic levels.
More detail on the sediment quality within the dredge footprint was
provided in the final EIA report and was addressed by the CSIR (2012b).
However, as requested by the DEA letter – 22 April 2014, the chemical
pollutants of these sediments have been taken account in the Port as well
as at the Dredge Disposal Site. Mitigation measures at the Dredge
Disposal site are provided in the suite of EMPrs but are also summarised
in this report.
5.4 Alien Invasive Species
Comment from DEA –
22 April 2014
Response
The revised report
should provide
examples and
references showing that
there are no risks
regarding the
establishment of alien
invasive species.
Colonisation by invasive alien species is not predicted to be a threat due to
the high salinities in the area as well as the fact that one of the main
invasive species required hard surfaces and thus will not colonise
sandbank habitat.
5.5 Stability of the Sandbanks
Comment from DEA –
22 April 2014
Response
The stability of the
newly created sandbank
The Extension of the Sandbank – Engineering Risk Assessment report
took into account the findings of the Geotechnical finite element analyses
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and cutaway were
exhausted tested and it
was found that the new
design would be more
stable than the current
layout.
have been carried out using the computer programme PLAXIS to ensure
the stability of the sandbank extension. The findings show that all slopes
have been designed to ensure adequate factor of safety against failure. A
double anchored sheet pile wall ensures stability of the existing sandbank
during installation of the caisson quay wall forming the western wall of the
basin.
A Morphological Study was also undertaken to determine the changes (if
any) of erosion and deposition at the Central Sandbank. Comparing for all
scenarios, it may be seen that in each case, there are no discernable
differences in erosion and depositional trends for the sandbank or the Little
Lagoon.
Sedimentation for the post construction scenario (Option 3H), appears to
be marginally higher in all cases, while total maximum erosion depths are
very similar. This is attributable to the larger sandbank providing increased
surface area for erosion although the rate of erosion may be equal.
Hydrodynamic and morphological analyses of the Port of Durban using
DELFT‐3D to determine the short and long term stability and form of the
extended sandbank, including the effects of wave penetration, wind and
currents due to tidal movements and other effects. These studies indicate
that the extended sandbank will be stable and that it will not endanger the
stability of the existing sandbank during construction, or during operation
of the container terminal. It also indicates that flows will not change in the
area of the Little Lagoon and this, combined with the sheet pile protection
to be installed, will ensure that the Little Lagoon is not disturbed.
5.6 Mitigation Measures and Monitoring
Comment from DEA –
22 April 2014
Response
Quarterly or more
frequent monitoring
would be undertaken for
5 years
Baseline thresholds need to be established in order to confirm the defined
maximum/minimum water quality thresholds, to confirm the biotic
community composition on the existing sandbank and to allow
comparisons after the sandbank extension which show whether the
extension has been successful.
These thresholds will be determined from ecological baseline data that will
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be collected over a period of 12-24 months prior to the start of the project.
The baseline assessments will focus on the following components:
Physico-chemical (habitat) variables:
Total Suspended Solids (TSS);
Salinity;
Temperature;
Dissolved Oxygen;
Sediment Grain Size Distribution;
Organic Carbon Content; and
Trace metal content in sediment (Cd, Hg, As, Cr, Cu, Pb, Ni,
Zn).
Faunal and floral assemblages:
Benthic microalgae (microphytobenthos);
Benthic macrofauna;
Ichythyfauna; and
Avifauna.
A graphic depicting how such a process may play out in the case of this
project is shown in Figure 18 below The blue and purple line represents
the average number of individuals or species at a suite of stations on the
existing sandbank distant from the impact (dredge) area (Control 1) and a
second group in close proximity to the area where the new sandbank
habitat will be created (Control 2), respectively. The red line represents
average abundance at a suite of stations on the newly created sandbank.
The dots on each line represent average values derived from discrete
samples collected at quarterly intervals (every 3 months) at these
respective sites. The horizontal dotted lines on the diagram represent
abundance for all the Control 1 stations (which are located far from the
impact site Control 1) average across the full time period of the study, and
the 80% level for these sites.
Sampling at the control stations will commence at 12-24 months before the
commencement date of the project and will continue until it can be
established that the biota at the control stations in close proximity to the
impact site (Control 2) and that on the newly established sandbank area
have recovered to a level that corresponds to at least 80% of the average
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level measured at Control 1 (the lower dotted line).
Sampling at the stations on the newly established sandbank will
commence immediately after construction is complete (denoted by the
vertical dotted line on the left side of the diagram) and will continue until
the abundance at these sites exceeds the 80% level at Control 1 for at
least five years (denoted by the vertical dotted line in the centre of the
diagram). Note that in this diagram abundance at the control station in
close proximity to the impact site (Control 2) dropped during the
construction phase but recovered again shortly thereafter.
Figure 15. Graphic demonstration of procedures for monitoring
environmental impacts and recovery.
Minimized disturbance
on sandbanks during
construction including:
• No construction
workers allowed on
Sandbank;
• Dredging within
100m of the
Sandbank to be
undertaken during
winter;
• No dredging to be
done at night;
• Dredging within a
These mitigation measures are included in the suite of EMPrs. Mitigation
measures related to the Central Sandbank, Avifauna, Dredging and
Disposal etc. have also been included in this report.
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100m should be
done as far as
possible at only site
at a time;
• A significant portion
of Central
Sandbank must
remain untouched
during dredging;
•
Qualified Environmental
Offices need to monitor
construction activities;
The EMPr makes provision for a qualified Environmental Control Officer
and an Environmental Officer for the Contractors. Roles and
responsibilities are summarised below:
A high-level outline of the institutional arrangements for the implementation
of the EMPs is provided in Figure 19.
Figure 16: Institutional Arrangements: Roles & Responsibility
Environmental Control Officer
The Environmental Control Officer (ECO) is a, competent (minimum of 3
years’ experience) and independent representative, who acts on as the
Environmental Monitoring Committee (EMC) monitoring representative for
the conducting of independent audits and performing a secretariat function
for the EMC.
The ECO will undertake bi-weekly inspections of the site and at least three-
monthly full compliance auditing against the EMP and Environmental
Authorisation. The aforementioned reports will be submitted to the Project
Manager, EMC and DEA for their records.
The ECO will also check the following:
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The record of environmental incidents (spills, impacts, legal
transgressions, etc.) as well as corrective and preventive actions
taken;
The public complaints register in which all complaints are recorded, as
well as actions taken; and
Results from the environmental monitoring programme (turbidity,
sandbank expansion biodiversity monitoring, water quality; air quality
etc.).
Contractor’s Environmental Officer
The primary role of the competent Environmental Officer (minimum of 3
years’ experience) is to coordinate daily environmental management
activities of the Contractor on site.
Specific responsibilities of the Environmental Officer, who will be on site,
will include the following:
Aiding the Contractor to comply with all the project’s environmental
management requirements;
Assisting the Contractor in compiling Method Statements;
Facilitating environmental activities and environmental awareness
training of all persons on site;
Exercise an internal compliance management system on behalf of the
Contractor;
Inspect the site as required to ensure adherence to the management
actions of the EMP and the Method Statements;
Ensuring that environmental monitoring (air quality, water quality, etc.)
is being undertaken;
Complete Site Inspection Forms on a regular basis;
Provide inputs to the regular environment report to be prepared by the
ECO (as required);
Liaise with the construction team on issues related to implementation
of, and compliance with, the EMP;
Maintain a record of environmental incidents (spills, impacts, legal
transgressions etc) as well as corrective and preventive actions taken;
and
Maintain a public complaints register in which all complaints are
recorded, as well as action taken.
Reporting to the DEA The ECO will undertake bi-weekly inspections of the site and at least three-
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must be frequent and
reporting of
disturbances must be
almost in a real time
basis
monthly full compliance auditing against the EMP and Environmental
Authorisation. The aforementioned reports will be submitted to the Project
Manager, EMC and DEA for their records.
The following sentence has been added to the EMPrs to ensure that the
DEA is aware of all disturbances:
The bi-weekly inspection must be submitted to the DEA within 7 days
of the inspection. Should any non-compliances be noted, they must
be submitted to the DEA within 24 hours of the incident.
If mitigation and
rehabilitation
measures fail then
offset measures
need to be discussed
As discussed at the meeting with DEA on 28 February 2014. Should the
extended monitoring (5 years from the day the construction of the
sandbank is extended) not find that abundance at the Extended Sandbank
reaches 80% of the average level measured at the control sites (on the
undisturbed area of the Sandbank), Transnet will enter into discussions
with the DEA regarding the potential for an offset. However, this measure
is not expected to be required for the following reasons:
Colonisation and succession of soft substrate benthic fauna has been well
studied in marine and estuarine systems, mostly in projects involving
dredging and dredge spoil disposal, but also in the context of in beach
nourishment and tidal flat habitat creation. Initial colonisation will be
dominated by opportunistic species. Based on the work of Pearson and
Rosenburg (1978) and Rhoads et al. (1978), Newell et al. (1998) proposed
a model of benthic recovery from disturbance (dredging) that involves
sharp increases in both number of species and abundance of organisms to
above that of baseline or control communities. This initial colonisation
comprises opportunistic species which generally reach a peak in
population numbers within six months. Models such as this are widely
accepted in the scientific literature, and are based on sound ecological
theory as well as empirical observations. Opportunistic species as initial
colonisers are, by virtue of the life histories and biology, either quick to take
advantage of new resources and/or exploiting resources in the absence of
competitors (Thistle 1981). Numerous experimental studies involving field
manipulation of sediments have shown very quick initial colonisation of
defaunated sediments. Botter-Carvalho et al. (2011) found colonisation to
occur very quickly with some species recruiting within one day, but others
obviously taking longer. Abundances at treatment sites were generally not
statistically different from those at control sites within six months. In
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reviewing other studies of colonisation of defaunated sediments in the
subtropics they found abundance of macrofauna to recovery within periods
ranging from 2 weeks to 14 months, while species richness recovered
within 4 months to >19 months.
This concurs well with results from field studies of benthic colonisation and
succession after disturbance. Recovery rates of benthic communities in
these cases have been found to vary widely (Newell et al. 1998, Desprez
2000, Kotta et al. 2009, and references therein). Moreover, different
aspects of the community may recover at different rates. Desprez (2000)
cited several recolonisation studies where numbers of species and
abundance recovered quickly after dredging (within 12 months) but
biomass recovered at a slower rate. Similar findings were reported by
Newell et al. (2004). These studies were in temperate systems and in the
subtropical Durban Bay markedly slower biomass recovery is unlikely.
Other works have reported more rapid and complete recolonisation within
much shorter periods. Guerra-García et al. (2003) reported recovery within
about six months of dredging fine sediments in a small harbour while Van
Dolah et al. (1984) noted even quicker recovery (within three months) after
dredging soft estuarine muds.
While colonisation of defaunated sediments and recovery of total faunal
abundances and species richness can, and usually does occur rapidly,
recovery to a similar community as that at reference or undisturbed
sandbanks often takes longer. Published ranges of recovery periods
following dredge disposal in marine and estuarine systems vary but are
typically between nine months and four years (Bolam and Rees 2003).
Some studies have found shorter recovery of the benthic community (e.g.
six months, Guerra-García et al. 2003) while others have found much
longer recovery rates, although this is frequently related to long term
changes in habitat, such as changed sediment granulometry (e.g. Boyd et
al. 2005) or tidal elevation (e.g. Bolam and Whomersley 2003).
Summary information on a number of other case studies from estuaries or
shallow water marine systems is presented below:
Evens et al. (1998) investigated the recolonisation of an existing
intertidal mudflat by macroinvertebrates and birds in the Tees
Estuary, England, following restoration of tidal inundation. He
reported that a stable macroinvertebrate population had developed
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after a period of 3 years. The actual success of restoring the
mudflats, however, could not be evaluated as no baseline data
were available prior to tidal inundation ceasing for comparative
purposes.
Ray (2000) reported on creation and colonisation of an artificial
mudflat made of dredge spoil on the coast of Maine, USA. In this
instance an artificial mudflat was created and its macroinvertebrate
community assessed and compared to an adjacent reference site
over a period of five years. The study found that diverse and
complex infaunal assemblages were able to establish themselves
on the mudflats constructed of dredged materials, and that within
three years the communities on constructed flats resembled those
on the natural flats.
Brooks (1983) reported on colonisation of dredged sediments on a
dredge spoil disposal site located at 20 m depth in Long Island
Sound. He found that three months after final capping of the
disposal site the numbers of benthic macrofauna individuals and
species present and were “roughly comparable” to those at the
reference stations and that after 15 months the number of
macrofauna individuals and species were significantly higher than
reference sites and in the predisposal reference collections.
Bolam and Whomersley (2005) reported on changes in physical
parameters and recovery of benthic macrofauna in dredge spoil at
three beneficial use schemes in estuaries in south-east England.
They found that environmental parameters (sediment redox
potential, and water, organic carbon and silt/clay contents) and
univariate community attributes (total individuals and species,
diversity, evenness and biomass) had attained reference levels at
two schemes but that assemblages differed significantly in terms of
species composition at all three schemes. (Note however, the role
of potentially confounding variables as articulated above).
Bolam et al. (2004) found that recolonisation of 1 m2 of defaunated
sediments resulted in recovery of univariate indices after only three
months and community structure after 6-12 months on a mudflat in
south-east England.
Beukema et al. (1999) reported that number of species and
individuals took 6 and 12 months to recover, respectively, following
the defaunation of larger areas (120 m2) of mudflat in the Dutch
Wadden Sea.
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Vogt (2010) studied experimental restoration of the Big Egg Marsh
in Jamaica Bay, New York City harbour. He reported on recovery
of salt marsh vegetation and macrofauna on artificial islands
constructed from dredge spoil. He found that the project was a
success in that the dredge spoil had been successfully
transforming into a silty and organic saltmarsh soil, that a dense
cover of smooth cordgrass had developed on the islands, and that
an “appropriate” animal community had become established.
Bolam and Whomersley (2004) found that the diversity, abundance
and species richness of two mudflat communities created from
dredged material near Jonesport, Maine, had re-established the
levels found at reference mudflats after two years.
Literature on the impacts and colonisation of offshore (deep water) dredge
spoil disposal areas provides a similar perspective. Studies in the OSPAR
maritime area (North-East Atlantic) for example, indicate recovery rates for
species richness, abundance and diversity amongst macrofaunal
communities to range from 3 months to 2 years (Stronkhorst et al. 2003;
Bolam and Rees, 2003; CEFAS, 2005; Bolam et al. 2006a; b; Bolam and
Whomersley 2005; Van Dalfsen and Lewis 2006).
Silt levels in the water
column must be
maintained at
‘moderate’ levels and
silt screens must be
used while dredging
wherever possible
It is anticipated that during construction (dredging) phase of the project, the
primary impact vector will be levels of suspended sediment and/or organic
material in the water column. High levels of suspended sediment and
organic material can affect living organisms by reducing levels of dissolved
oxygen in the water column (mediated through the decomposition of
organic matter or release of hydrogen sulphide), by blocking the
transmission of light through the water column (thereby affecting
phytoplankton and macrolagal production), by blocking the gills or feeding
apparatus of filter feeding organisms (invertebrates, fish and sharks), or by
smothering benthic organisms. (Note that surveys of the dredge sediment
conducted as part of the EIA study (CSIR 2012a) have indicated that levels
of trace metals and other contaminants in the dredge sediments are low
and pose minimal risk to marine organisms). Thus, the focus during the
construction (dredging) phase of the project will be on ensuring that
suspended sediment levels in the water column adjacent to the sandbanks
do not exceed a defined threshold risk level of 50 mg/L and that oxygen
levels in the water column do not drop below 5 mg/L (99 % of the time) and
below 6 mg/L (95 % of the time).
These threshold risk level has been derived from the work of Steffani et al.
(2003) and from the South African Water Quality Guidelines (DWAF 1995).
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Steffani et al. (2003) provided guidelines for concentrations of suspended
solids in relation to the risk they pose to benthic marine invertebrates,
which are considered to be amongst the most sensitive organisms to
elevated suspended sediment levels given that they are mostly sedentary
and are unable to move away from the source of impact, as follows:
Low risk: < 20 mg.L-1
Medium risk: 20-80 mg.L-1
High risk, requiring mitigation: > 80 mg.L-1
The defined threshold risk level of 50 mg/L lies at the centre of the
medium risk range as posed by Steffani et al. (2003).
The dissolved oxygen of water is a non-conservative property; solubility of
oxygen in water being dependent on the salinity and temperature of the
water (DWAF 1995). The South African Water Quality Guidelines provide
the following data on solubility of oxygen in seawater under constant
pressure (one atmosphere) for a range of salinities and temperatures
(Table 5). Cells spanning the typical range in temperature and salinity in
the Port of Durban and corresponding oxygen saturation values are
highlighted in grey on this table. From this it is clear that under ideal
conditions (i.e. 100% saturation), levels of dissolved oxygen would vary
between 6.3 and 8.2 mg/L under the influence of changing temperature
and salinity alone. For this reason the SA Water Quality Guidelines
recommend that the target levels for dissolved oxygen in the coastal zone
off the south and east coasts should not fall below 5 mg/L (99 % of the
time) and below 6 mg/L (95 %) of the time. These are also the defined
threshold risk levels that have been adopted for this study as well.
Table 5. Solubility of oxygen in seawater (mg/L) under
constant pressure (one atmosphere) for a range of salinities and
temperatures (Source: DWAFR 1995).
Temperature
Salinity
25x10-3
30x10-3
35x10-3
40x10-3
10 9,621 9,318 9,024 8,739
11 9,412 9,117 8,832 8,556
12 9,210 8,925 8,648 8,379
13 9,017 8,739 8,470 8,210
14 8,830 8,561 8,300 8,046
15 8,651 8,389 8,135 7,888
16 8,478 8,223 7,976 7,737
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17 8,311 8,064 7,823 7,590
18 8.151 7,910 7,676 7,449
19 7,995 7,761 7,533 7,312
20 7,846 7,617 7,395 7,180
21 7,701 7,479 7,262 7,052
22 7,561 7,344 7,134 6,929
23 7,426 7,214 7,009 6,809
24 7,295 7,089 6,888 6,693
25 7,168 6,967 6,771 6,581
26 7,045 6,849 6,658 6,472
27 6,926 6,734 6,548 6,366
28 6,810 6,623 6,441 6,263
29 6,698 6,515 6,337 6,164
30 6,589 6,410 6,236 6,066
With this in mind the following protocol is proposed during the dredging
operations:
1. Continuous monitoring should be undertaken of turbidity and
dissolved oxygen levels at a point immediately adjacent to the
Central Sand Bank, between the bank and the dredger and/or
dredge hopper, and at a point immediately adjacent to Little
Lagoon at a point between the Lagoon and the dredger and/or
dredge hopper (hereinafter referred to as “the designated
monitoring stations”), during the dredge operations.
2. Data from such monitoring work should be available in real time to
the person coordinating dredging activities.
3. Dredging operations should be halted immediately if (a) turbidity
levels exceed a threshold level of 50 mg/L and/or (b) if levels of
dissolved oxygen are observed to drop below 5 mg/L for more than
1 minutes in every 60 minutes (1.7% of the time) or below 6 mg/L
for more than 3 minutes in every 60 minutes (5% of the time), and
should not recommence until levels have declined below this point.
4. If turbidity frequently exceeds or levels of dissolved oxygen
frequently drops below threshold levels at the designated
monitoring stations, ‘Silt Curtains’ should be deployed at the
burrow pit as a mitigation measure. The lower end of the ‘skirt’ of
the silt curtains must be allowed to rest upon the seafloor, and the
top of the ‘skirt’ must be above the water surface.
5. Turbidity should also be minimised by choking the dredge hopper
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overflow with a fully automated system. In this scenario, a
computerized process controller ensures dynamic adjustment of
the valve in the overflow funnel which chokes the flow in such a
way that a constant fluid level in the hopper is maintained and, as
a result, no air is taken down with the suspension leaving the
hopper.
The little lagoon would
be specially protected
during construction and
afterwards
Continuous monitoring should be undertaken of turbidity and dissolved
oxygen levels at a point immediately adjacent to Little Lagoon at a point
between the Lagoon and the dredger and/or dredge hopper during the
dredge operations.
The purpose of this monitoring location is to ensure that there is no impact
on the Little Lagoon. Additional mitigation measures to protect the Little
Lagoon are included in the Suite of EMPrs. However the findings of the
specialists suggest that the main potential impact is related to increased
turbidity due to dredging.
The following additional mitigation measures are suggested to minimise
impacts related to turbidity:
1. Dredging operations should be halted immediately if (a) turbidity
levels exceed a threshold level of 50 mg/L and/or (b) if levels of
dissolved oxygen are observed to drop below 5 mg/L for more than
1 minutes in every 60 minutes (1.7% of the time) or below 6 mg/L
for more than 3 minutes in every 60 minutes (5% of the time), and
should not recommence until levels have declined below this point.
2. If turbidity frequently exceeds or levels of dissolved oxygen
frequently drops below threshold levels at the designated
monitoring stations, ‘Silt Curtains’ should be deployed at the
burrow pit as a mitigation measure. The lower end of the ‘skirt’ of
the silt curtains must be allowed to rest upon the seafloor, and the
top of the ‘skirt’ must be above the water surface.
3. Turbidity should also be minimised by choking the dredge hopper
overflow with a fully automated system. In this scenario, a
computerized process controller ensures dynamic adjustment of
the valve in the overflow funnel which chokes the flow in such a
way that a constant fluid level in the hopper is maintained and, as
a result, no air is taken down with the suspension leaving the
hopper.
Specific mitigation
procedures will need to
form part of the
Noted. During public consultation, Ulric Van Bloemestein from DEA:
Oceans and Coasts requested that certain best practices be included in
the Suite of EMPrs. These include the following:
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Dumping at Sea
Permits. New best
practices measures and
standards gazetted in
2012 must be used in
the assessment of the
Dumping at Sea Permit.
A GPS record must be kept. This record must include:
o Time of departure from the dredge site
o Time of arrival at the disposal site
o Position of the vessel at the time of starting to discharge
dredge spoil.
o Heading and speed of the vessel at the time of starting to
discharge the dredge spoil.
o Position of the vessel at the time of completion of the
discharge of dredge spoil.
o Heading and speed of the vessel at the time of completion of
discharging of dredge spoil.
The daily track plot must be recorded electronically on a compact disc
in ASCII format.
This information must be provided to the ECO on a weekly basis.
The ECO must be notified immediately if there is an incident whereby
there is dumping of material outside the designated zone. The daily
track plot must also be provided immediately if there is an incident.
The hoppers must have load indicator equipment on board to ensure
that the hopper doors are not leaking and that no part of the load is
being deposited anywhere other than the designated disposal site.
Load Indicator data must be provided to the ECO on a weekly basis.
The load indicator graph shall be marked with the date and number of
each load.
Details of the load indicator equipment must be provided to the ECO
prior to commencement of operations.
The dredger must dispose dredge material in such a way that no large
mounds are produced.
The contractor must set up a matrix of the site to ensure there is even
dumping distribution and no disposal should occur at locations where a
sediment load has been deposited within the last week.
The dredger must dispose of sediment in as thin a layer as possible.
The volumes of disposal must be recorded and provided to the ECO
weekly. This will also be provided to the EMC on a monthly basis.
This mitigation measures will also be included in the submission for the
Dumping at Sea Permit. Measures and Standards gazetted in 2012 will
also be taken into account.
A monitoring
programme should
include sandbank
Noted. The following will be monitored as part of the baseline survey and
then during and after construction:
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morphology, sediment
granulometry and
organic content, benthic
macrofauna, avifauna
and levels of pollutants.
Monitoring must be
undertaken intensely for
2 years and continue
less intensely for
another 3 years.
Physico-chemical (habitat) variables
Total Suspended Solids (TSS)
Salinity
Temperature
Dissolved Oxygen
Sediment grain size distribution
Organic carbon content
Trace metal content in sediment (Cd, Hg As, Cr, Cu, Pb, Ni, Zn).
Faunal and floral assemblages
Benthic microalgae (microphytobenthos)
Benthic macrofauna
Fish
Birds
Adaption and mitigation
measures which may be
of importance to
infrastructure (in terms
of climate change) must
be addressed.
The Effect of Climate Change on Engineering design shows that the
chosen cope level of +4.25m CDP is sufficient, providing a freeboard of
0.324m over and above the allowed for accumulation of various upper
bound increases for climate change affected parameters.
This indicates clearly that the risks and vulnerability of the new quays to
climate change, and in particular sea level rise and storm surge, have been
minimised and that the selected cope height of 4.25 m originally proposed
by Transnet for this project is safe, conservative for its design life of 50
years from the projected completion date of 2019 and that a safe freeboard
will still exist. In fact, given the year 2100 projection values, the structure is
likely to be safe for a further 32 years after 2069. In all cases this is in the
event of the simultaneous occurrence of all factors affecting the water level
in the Port.
Various improbable extreme scenarios (e.g. UKCP09 H++) have been
taken into account when evaluating the design in terms of contingency
planning in the event of these extreme scenarios.
Other climate change affected parameters such as wind, rainfall and ocean
acidification have been taken account during the design of the quay
structures, storm water system and concrete specification.
The threat of flooding during the construction phase has been evaluated
and we conclude that construction will not adversely affect the current
levels or increase the risk or vulnerability to flooding.
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6 SUMMARY OF ADDITIONAL MITIGATION MEASURES
Please note that these mitigation measures are an extension of the suite of EMPrs
presented in the Final EIA Report.
6.1 Central Sandbank
6.1.1 Management and Minimization of Habitat Loss
Minimise habitat loss of the Central Sandbank.
Ensure strict monitoring protocol is developed for Sandbank extension and recreated
seagrass beds.
Strict adherence to the Dredge Footprint Option 3H which involves the creation of a
Central Sandbank extension results in a slight increase in sandbank habitat.
Dredger track plots of dredging activity must be provided daily during the dredging of the
Dredge footprint and cross checked against the Dredge Footprint Option 3H by the
Contractor, EO and verified by the ECO.
The ECO should be onsite during the dredging of the Central Sandbank.
The contractor should produce a matrix for the Central Sandbank area to be dredged.
Photographs should be taken of each grid plot prior to dredging.
The contractor should produce a detailed method statement for dredging of the Central
Sandbank area.
A detailed pre-construction photographic record of dredging of the Central Sandbank
should be undertaken by the ECO.
Undertake a feasibility study for the additional mitigation measure of the creation of a
shallow subtidal area in the newly created Sandbank extension.
If feasible, submit separate EMP for the Establishment of Seagrass beds and attempt to
establish Zostera capensis (seagrass) beds.
The use of environmentally less damaging methods of scour protection should be
investigated (such as use of softer protection measures such as porous geotextiles or
meshes that allow recruitment of appropriate biota.
Long term stability of the Sandbank extension should be monitored.
o Bathymetric/topographical surveys should be undertaken one week after and
then one month after the completion of dredging. Thereafter, surveys should be
undertaken every six months.
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Monitoring of ecological succession of the Sandbank extension is also essential. The
elements to be monitored include:
o Sandbank morphology (for bathymetric/topographical survey above);
o Sediment granulometry and organic content;
o Water physic-chemisty (in situ measurement including dissolved oxygen, turbidity
and chlorophyll levels;
o Benthic macrofauna and sandprawn densities;
o Ichthyofauna; and
o Avifauna.
As part of the seagrass bed creation, Zostera establishment, health and coverage should
be monitored (if feasible).
6.1.2 Management of Central Sandbank*
Ensure that the Central Sandbank incurs minimal indirect impacts associated with Berth
Infrastructure construction.
Stabilisation/retaining temporary sheet piles should be used for the Berth 205 extension
instead of the excavation of a stabilising slope.
The recommendations of the Storm Water Management Plan must be taken into
account.
During the construction phase of the extension of Berths 205 through to 203, cut‐off
drains are to be provided to collect stormwater in the affected areas which will be routed
temporarily and drained into adjacent stormwater system of the existing quay. This
stormwater system will apply to the sequence of three stages so that the existing
stormwater system at Berth 204 will accommodate the stormwater of the affected areas
of Berth 205. Likewise, the affected areas of Berth 204 will be accommodated by the
existing stormwater system of Berth 203.
The existing outlet pipes are to be blocked off separately during each construction stage
to ensure that the majority of the existing outlet pipes are operational at all times.
Sufficient additional temporary stormwater drain pipes will be provided to accommodate
extreme events.
Minimal changes to Durban Bay hydrodynamics through the choice of Dredge Footprint
Option 3H.
Use of Sheet Piles to stabilise the western edge of Berth 205 during excavation of the
Caisson trench which limits changes to port layout and related hydrodynamics.
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Install scour protection to prevent future erosion, if required (and related further changes
to hydrodynamics of Durban Bay).
Conduct water quality monitoring at Central Sandbank and Little Lagoon.
All diffuse pollution sources to be managed to prevent pollution of the Estuary.
Storage area and ablution facilities to be located 100m from edge of the estuary.
No waste water to be released to the Estuary.
Ensure proper storage of material (including fuel, paint) that could cause water pollution.
Ensure proper storage and careful handling of hazardous substances with spill
prevention materials at hand.
Barges and dredging machinery to be maintained to prevent any oil and diesel pollution
during waterside construction activities.
Adequate environmental awareness to ensure construction labourers do not pollute
Durban Bay Estuary.
Spill management method statements for insitu concrete works (such as Soft Piling) to
be developed) to ensure adequate management of any spills.
o Ensure all water quality and pollution general mitigation measures are adhered
to.
o Ensure all mitigation measures contained in the Dredge Footprint and Disposal
EMP are adhered to.
o Ensure Sandbank Extension is undertaken prior to dredging of the western edge
of Central Sandbank adjacent to Berth 205 is removed.
o Ensure monitoring of the Sandbank Extension is undertaken as per the Pre-
Construction and Sandbank Extension EMP.
o Minimise disturbance to avifauna by ensuring noise minimisation measures are
implemented.
o Barricading and restricted access to be maintained to prevent unauthorised
access to Central Sandbanks during construction.
o Environmental awareness training to emphasise the importance of Central
Sandbanks.
o Zero tolerance policy regarding impacts to Central Sandbanks labourers.
6.1.3 Management of Central Sandbank Dredging
Minimise habitat loss of the Central Sandbank.
Ensure strict monitoring protocol is developed for Sandbank extension and recreated
seagrass beds.
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Ensure no long term erosion of the Central Sandbank occurs.
Strict adherence to the Dredge Footprint Option 3H which involves the creation of a
Central Sandbank extension results in a slight increase in sandbank habitat, and the
provision of a Caisson quay wall along the western edge of Berth 205 to ensure no long
term erosion.
Dredger track plots of dredging activity must be provided daily during the dredging of the
Dredge footprint and cross checked against the Dredge Footprint Option 3H by the
Contractor, EO and verified by the ECO.
The ECO should be onsite during the dredging of the Central Sandbank.
The contractor should produce a matrix for the Central Sandbank area to be dredged.
Photographs should be taken of each grid plot prior to dredging.
The contractor should produce a detailed method statement for dredging of the Central
Sandbank area.
Immediately prior to dredging of the Central Sandbank area, a walk down of each grid
square should be undertaken. Any biota which can be relocated to different areas within
the Central Sandbank should be moved. Details of relocated biota should be recorded
including information on location as well as a photographic record.
Environmental monitoring specialists should be on site during dredging of the Central
Sandbank area so to provide expert advice if required.
A detailed photographic record of dredging of the Central Sandbank should be
undertaken by the ECO.
Undertake the additional mitigation measures of the creation of a shallow subtidal area in
the newly created Sandbank extension and attempt to establish Zostera capensis
(seagrass) beds.
The use of environmentally less damaging methods of scour protection should be
investigated (such as use of softer protection measures such as porous geotextiles or
meshes that allow recruitment of appropriate biota.
Monitoring of ecological succession of the Sandbank extension is also essential. The
elements to be monitored include:
o Sandbank morphology (for bathymetric/topographical survey above);
o Sediment granulometry and organic content;
o Water physic-chemisty (in situ measurement including dissolved oxygen, turbidity
and chlorophyll levels;
o Benthic macrofauna and sandprawn densities;
o Ichthyofauna; and
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o Avifauna.
As part of the seagrass bed creation, Zostera establishment, health and coverage should
be monitored.
Long term stability of the Sandbank extension should be monitored.
o Bathymetric/topographical surveys should be undertaken one week after and
then one month after the completion of dredging. Thereafter, surveys should be
undertaken every six months.
o If any long term erosion does occur, the ECO, Project Manager, and EMC should
be notified immediately.
An emergency protocol should be development by specialists prior to dredging to ensure
there is an adequate mitigation programme to prevent further erosion, should any occur.
The slopes of the dredged area and scour protection placement must be done accurately
so to ensure immediate stabilisation of the area.
Temporary sheet piles should be used along the western edge of Berth 205 in order to
act as a retaining or stabilising wall during dredging.
6.1.4 Management of Central Sandbank Extension
Minimise disturbance to Central Sandbank area adjacent to Sandbank extension area.
Continuous monitoring should be undertaken of turbidity levels at a depth of 2 m at least
three stations along the southern edge of the Centre Bank and at least one station in
little lagoon during the Central Sandbank Extension. Data from the turbidity monitoring
instruments should be available in real time to the person coordinating dredging
activities.
Dredging operations should be halted immediately if turbidity levels exceed the proposed
threshold level of 50 mg/l-1 at any of the monitoring stations and should not recommence
until levels have declined below this point.
Pumping shall be controllable in rate so that it can be slowed if turbidity levels rise. It is
expected that pumping can be maximized over both high and low tide periods, but may
have to be reduced as tidal flows in both directions increase. In particular turbidity during
tidal flows away from the sandbank and towards the new basin must be strictly controlled
to prevent sand flowing back into the newly dredged areas.
Floating containment curtains extending well into the water will be required to restrict
movement of the more turbid water until it has settled.
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Pump the reclaim material behind the sandbag retaining structure in a sequence so that
the area is filled evenly and rises in layers from below. This procedure will reduce
entrainment of sand in the water column and thus reduce turbidity.
Ensure that all monitoring results are provided to the ECO and EMC and DEA as
required.
All monitoring is to be carried out by experts (trained marine biologists/ecologists).
6.1.5 Management of stabilization of the toe of the Extended Sandbank
Ensure Extended Sandbank is correctly stabilised.
Place sandbags along the line of the new toe of the extended sandbank to form a low
retaining structure.
Bio‐degradable sandbags would be preferred.
6.1.6 Offset Plan
As discussed at the meeting with DEA on 28 February 2014, should the extended monitoring
(5 years from the day the construction of the sandbank) not find that abundance at the
Extended Sandbank reaches 80% of the average level measured at the control sites (on the
undisturbed area of the Sandbank), Transnet will enter into discussions with the DEA
regarding the potential for an offset plan.
6.2 Avifauna
Ensure minimal disturbance to avifauna during construction.
Minimise Central Sandbank habitat loss.
Minimise impacts due to turbidity.
Infill dredged area of Centre Bank to meet adjacent to the quay wall of the west end of
Berth 205 and extend Centre Bank sand bank south as proposed in Option 3H of the
Dredging Layout (ZAA Engineering Projects & Naval Architects, 2012). This will result in
a net gain of intertidal sand flat.
Undertake all dredging within 100 m of the Centre Bank intertidal-sand flats during winter
when bird abundances are lower and Palearctic migrants are away (if possible).
When dredging within 100 m of Centre Bank intertidal-sand flats, do not dredge at
multiple sites concurrently, but only at one area at a time with a single dredger.
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No dredging operations should be conducted between sunset and sunrise within 100 m
of Centre Bank intertidal-sand flats including the infilling of sand up to the new quay wall
of Berth 205 and southward enlargement of Centre Bank.
Continuous monitoring should be undertaken of turbidity levels at a depth of 2 m at least
three stations along the southern edge of the Centre Bank and at least one station in
little lagoon during dredging operations. Data from the turbidity monitoring instruments
should be available in real time to the person coordinating dredging activities. Dredging
operations should be halted immediately if turbidity levels exceed the proposed threshold
level of 50 mg/l at any of the monitoring stations and should not recommence until levels
have declined below this point.
If turbidity frequently exceed threshold levels at the monitoring stations adjacent o the
central sand bank and/or in little lagoon during dredging operations, use of ‘Silt Curtains’
at the burrow pit may be necessary. The lower end of the ‘skirt’ must be allowed to rest
upon the seafloor, and the top of the ‘skirt’ must be above the water surface.
Choking the dredge hopper overflow with a fully automated system is also
recommended. In this scenario, a computerized process controller ensures dynamic
adjustment of the valve in the overflow funnel which chokes the flow in such a way that a
constant fluid level in the hopper is maintained and, as a result, no air is taken down with
the suspension leaving the hopper. This results in a significant decrease in turbidity.
Minimise the time period over which the dredging operation is to take place, to avoid the
daily re-suspension of sediments.
6.3 Dredging and Dredge Disposal
6.3.1 Management of Dredger
Ensure only Trailer Suction Hopper Dredger (TSHD) or Cutter Suction Dredger (CSD)
are used.
Ensure TSHD or CSD are maintained in good order.
6.3.2 Management of Turbidity
Ensure that the Total Suspended Solids (TSS) standard which has been developed for
the Port of Durban is not exceeded (50mg/l)
Ensure that Total Suspended Solids (TSS) standard which has been developed for the
Offshore Sand Winning Site is not exceeded (20mg/l).
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Continuous monitoring should be undertaken of turbidity levels at a depth of 2 m at least
three stations along the southern edge of the Centre Bank and at least one station in
little lagoon during dredging operations. Data from the turbidity monitoring instruments
should be available in real time to the person coordinating dredging activities.
Dredging operations should be halted immediately if turbidity levels exceed the proposed
threshold level of 50 mg/l at any of the monitoring stations and should not recommence
until levels have declined below this point.
If turbidity frequently exceed threshold levels at the monitoring stations adjacent to the
central sand bank and/or in little lagoon during dredging operations, use of ‘Silt Curtains’
may be necessary. The lower end of the ‘skirt’ must be allowed to rest upon the seafloor,
and the top of the ‘skirt’ must be above the water surface.
Choking the dredge hopper overflow with a fully automated system is also
recommended. In this scenario, a computerized process controller ensures dynamic
adjustment of the valve in the overflow funnel which chokes the flow in such a way that a
constant fluid level in the hopper is maintained and, as a result, no air is taken down with
the suspension leaving the hopper. This results in a significant decrease in turbidity.
Turbidity levels at three stations around the Offshore Sand Winning site are to be
monitored continuously for at least two months prior to the start of the sand winning and
dredge spoil disposal operations and should continue for a minimum of two months after
all operations have ceased.
At no point should the turbidity levels exceed the established maximum threshold of 20
mg/L at the Offshore Sand Winning Monitoring Sites. All dredging/disposal operations to
cease until the turbidity levels have fallen below 20 mg/L.
The use of a Campbell Scientific TMS185 wireless turbidity monitoring station is
recommended and should be set to notify appointed personnel via text message should
turbidity levels exceed the maximum established threshold during dredging and disposal
operations .
All monitoring is to be carried out by experts (trained marine biologists/ecologists).
Minimise the time period over which the dredging operation is to take place, to avoid the
daily re-suspension of sediments.
All monitoring reports to be provided to ECO, EMC and DEA.
6.3.3 Management of Transportation of Dredge Spoil to Disposal site
Ensure detailed records regarding the transportation of dredge spoil are kept.
Ensure minimal leaking of dredge material outside disposal site.
Minimise likelihood of incidents where dumping of material outside disposal site occurs.
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A GPS record must be kept of the route followed by the hopper. This record must
include:
o Time of departure from the dredge site
o Route followed by the vessel from dredge site to disposal site (GPS track)
o Time of arrival at the disposal site
o Position of the vessel at the time of starting to discharge dredge spoil.
o Heading and speed of the vessel at the time of starting to discharge the dredge
spoil.
o Position of the vessel at the time of completion of the discharge of dredge spoil.
o Heading and speed of the vessel at the time of completion of discharging of
dredge spoil.
o Route followed by the vessel on the way back to the dredge site (GPS track)
The daily track plot must be recorded electronically on a compact disc in ASCII format.
This information must be provided to the ECO on a weekly basis.
The ECO must be notified immediately if there is an incident whereby there is dumping
of material outside the designated zone. The daily track plot must also be provided
immediately if there is an incident.
The hoppers must have load indicator equipment on board to ensure that the hopper
doors are not leaking and that no part of the load is being deposited anywhere other than
the designated disposal site.
Load Indicator data must be provided to the ECO on a weekly basis. The load indicator
graph shall be marked with the date and number of each load.
Details of the load indicator equipment must be provided to the ECO prior to
commencement of operations.
6.3.4 Management of Disposal of Dredge Spoil at the Disposal Site
Ensure detailed records regarding disposal of dredge spoil are kept.
Ensure dredge material is only disposed within the permitted site.
Ensure only permitted volumes of dredge disposal are disposed.
Ensure dredge spoil is disposed of in a thin layer as practicable.
Ensure even distribution of dumping of dredge spoil.
Ensure minimal mortality of benthos at disposal site.
A GPS record must be kept. This record must include:
o Time of departure from the dredge site
o Time of arrival at the disposal site
o Position of the vessel at the time of starting to discharge dredge spoil.
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o Heading and speed of the vessel at the time of starting to discharge the dredge
spoil.
o Position of the vessel at the time of completion of the discharge of dredge spoil.
o Heading and speed of the vessel at the time of completion of discharging of
dredge spoil.
The daily track plot must be recorded electronically on a compact disc in ASCII format.
This information must be provided to the ECO on a weekly basis.
The ECO must be notified immediately if there is an incident whereby there is dumping
of material outside the designated zone. The daily track plot must also be provided
immediately if there is an incident.
The hoppers must have load indicator equipment on board to ensure that the hopper
doors are not leaking and that no part of the load is being deposited anywhere other than
the designated disposal site.
Load Indicator data must be provided to the ECO on a weekly basis. The load indicator
graph shall be marked with the date and number of each load.
Details of the load indicator equipment must be provided to the ECO prior to
commencement of operations.
The dredger must dispose dredge material in such a way that no large mounds are
produced.
The contractor must set up a matrix of the site to ensure there is even dumping
distribution and no disposal should occur at locations where a sediment load has been
deposited within the last week.
The dredger must dispose of sediment in as thin a layer as possible.
The volumes of disposal must be recorded and provided to the ECO weekly. This will
also be provided to the EMC on a monthly basis.
6.3.5 Management of Ballast Water
Ensure compliance with TNPA’s Ballast water management plan.
A detailed method statement regarding Ballast Water management to be produced.
6.4 Climate Change
6.4.1 Climate Change Adaptation
At present, Transnet (and the TNPA) does not have a port wide approach or
methodology to assessing and incorporating climate change risks such as sea level rise
and coastal storm surge. Assessment of these issues is undertaken at an individual
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project level, via Transnet’s project lifecycle planning process. The Effects of the
Climate Change on Engineering Design must therefore ensure that the effects of climate
change have been taken into account.
From a climate change adaptation perspective, the development options may be viewed
as more favourable than the “No Development” option as it will allow for climate change
adaptation criteria to be incorporated into the Berths 203 – 205 design parameters. The
present structures were designed at a time when climate change adaptation criteria were
not typically included in design parameters.
6.4.2 Climate Change Mitigation
The selection of development scenario (i.e. No Development, Partial Development or
Full Development) does not meaningfully impact on the GHG projections (either
cumulative total for 2012/13 – 2024/25 period or annual emissions by 2024/25).
Recommended GHG mitigation initiatives during the construction phase include:
o Requiring major contractors to report on their GHG emissions for the construction
phase.
o Requiring major contractors to provide a carbon mitigation plan, as part of the
construction planning activities, and as part of their overall environmental
management plan.
o Ensuring that the sources and quantities of major construction materials are
reported (i.e. steel and cement) to allow for tracking of GHG emissions associated
with these materials.
Key GHG mitigation initiatives targeting international maritime sector emissions include:
o Ensuring that the Berths 203 – 205 can readily accommodate the largest sized
container vessels possible (assuming that this is acceptable from a broader
environmental perspective).
o Adoption of an incentive programme to encourage the use of the most modern and
low carbon container vessels at Berths 203 - 205, such as the WPCI’s ESI
programme.
o Expanding TNPA’s GHG inventory to include reporting on international maritime
vessels docking at Berths 203 – 205.
o Implementing measures to address GHG emissions not captured in this
assessment i.e. cold ironing for vessels at Berths 203 – 205 (if not already
implemented).
Key GHG mitigation initiatives targeting land-based freight transport emissions include:
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o Massive expansion in the freight rail share of container transport flowing in and out
of Pier 2 (i.e. Berths 203 – 205), as compared to truck freight. The current share for
rail freight is estimated at 15% of TEUs. A minimum target of a 50% share should
be aimed for by 2024 and, ideally, closer to 85%.
o Continued investment in lower emission diesel electric locomotives operating the
container freight route to/from Pier 2 and a strategy of decarbonisation of the
electric traction network in relation to the freight rail servicing Pier 2.
o Implementation of GHG data gathering systems that allows for the generation of
freight rail corridor specific emission factors (i.e. kg CO2 per tonne-km or TEU-km
for specific freight rail corridors).
o Minimum standards and enforcement thereof for air emissions from freight trucks
handling cargo at Berths 203 – 205.
o Establishment of a Clean Truck Programme or similar incentive scheme aimed to
encourage replacement of older trucks with newer and lower GHG emitting
vehicles. This should not be implemented in a way that penalises marginal
operators (who cannot necessarily afford new vehicles), but could take the form of
a grant scheme, soft loan finance scheme or similar for qualifying truck freight
operators.
Damage to Central Sand Bank extension due to Climate Change resulting inter alia in
changes in sea level and increase in frequency and severity of storm surge. Extension is
eroded more than existing sandbank would have been and/or slips into dredged basin
and large amounts of sand deposited in dredged basins and channels
o Hydrodynamic and morphological analyses of anticipated severe storms and
variations in sea level have been carried out to demonstrate that the stability of the
sandbank extension will be at least equal to that of the existing sandbank. The
numerical model has been set up using the Delft3D suite of tools to simulate the
interaction between inter alia the following processes: water level variation due to
changes in sea level caused by climate change, storm surges and tides, flow
patterns within the port, wind and waves. Extreme wind velocities have been
increased by a factor of 10% over current extreme levels.
o If the sandbank is damaged, or a slip occurs, it is repaired during maintenance
dredging.
o Extension has been designed so the existing Central Sandbank cannot be
damaged due to damage of the sandbank extension.
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6.5 Little Lagoon
6.5.1 Management of Fencing and Restricted Access of Sensitive Environmental
Features
Ensure access to sensitive environmental features is restricted.
Ensure that access and fencing is maintained throughout the construction period.
Restrict access to Little Lagoon and ensure fences are maintained.
Ensure adequate signage of sensitive environmental features.
Maintain barricading/ fencing around sensitive environmental features.
Maintain adequate signage of sensitive environmental features.
Avoid any disturbance to demarcated sensitive environmental features.
Suitably experienced personnel to approve and monitor the fencing and restricted
access of sensitive environmental features.
6.5.2 Management of Little Lagoon
Ensure that the Little Lagoon is protected and incurs minimal negative impact to
resource quality.
Ensure nursery function of the Little Lagoon is not impacted.
Comply with the requirements of the National Environmental Management: Biodiversity
Act (No. 10 of 2004), National Forests Act (No. 84 of 1998), Natal Nature Conservation
Ordinance 15 of 1974 and Animal Protection Act (No. 71 of 1962).
Proper access control to be maintained to prevent access to Little Lagoon.
Stringent and dedicated control of poaching.
No fishing allowed.
Photographs of protected and sensitive fauna species must be displayed in the
construction camp to heighten awareness.
6.5.3 Management of Turbidity at the Little Lagoon
Continuous monitoring should be undertaken of turbidity and dissolved oxygen levels at
a point immediately adjacent to the Central Sand Bank, between the bank and the
dredger and/or dredge hopper, and at a point immediately adjacent to Little Lagoon at a
point between the Lagoon and the dredger and/or dredge hopper (hereinafter referred to
as “the designated monitoring stations”), during the dredge operations.
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Data from such monitoring work should be available in real time to the person
coordinating dredging activities.
Dredging operations should be halted immediately if (a) turbidity levels exceed a
threshold level of 50 mg/L and/or (b) if levels of dissolved oxygen are observed to drop
below 5 mg/L for more than 1 minutes in every 60 minutes (1.7% of the time) or below 6
mg/L for more than 3 minutes in every 60 minutes (5% of the time), and should not
recommence until levels have declined below this point.
If turbidity frequently exceeds or levels of dissolved oxygen frequently drops below
threshold levels at the designated monitoring stations, ‘Silt Curtains’ should be deployed
at the burrow pit as a mitigation measure. The lower end of the ‘skirt’ of the silt curtains
must be allowed to rest upon the seafloor, and the top of the ‘skirt’ must be above the
water surface.
Turbidity should also be minimised by choking the dredge hopper overflow with a fully
automated system. In this scenario, a computerized process controller ensures dynamic
adjustment of the valve in the overflow funnel which chokes the flow in such a way that a
constant fluid level in the hopper is maintained and, as a result, no air is taken down with
the suspension leaving the hopper.
Monitoring will be the last measure. A clearly defined management action has been
identified if, in spite of control measures noted above, TSS levels during the dredge
operations exceed a threshold level of 50 mg.L-1 or dissolved oxygen levels drop below
5 mg/L (>1% of the time) or below 6 mg/L (>5%) at any of the monitoring stations,
Dredging operations will be halted immediately and will not recommence until levels
have declined below threshold levels.
6.6 Monitoring to Mitigate Impacts of Turbidity
The baseline thresholds of acceptable change for each of these aspects will be derived from
ecological baseline data that will be collected over a period of 12 months prior to the start of
the project, along with ongoing monitoring at control stations outside of the zone of impact
during and after the end of the construction period (sediment and biota only). The baseline
assessment will focus on the following components:
Physico-chemical (habitat) variables
Total Suspended Solids (TSS)
Salinity
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Temperature
Dissolved Oxygen
Sediment grain size distribution
Organic carbon content
Trace metal content in sediment (Cd, Hg As, Cr, Cu, Pb, Ni, Zn).
Faunal and floral assemblages
Benthic microalgae (microphytobenthos)
Benthic macrofauna
Fish
Birds
Baseline water quality characteristics will be established by taking water quality
measurements at a suite of 20 stations distributed in the navigation channel adjacent to
Berth 203-205 and in the main channel of the port adjacent to the Central Sandbank. This
will include a number of control stations that will serve as reference stations in the future that
will be located outside of the influence of the proposed project activities (piling, dredging,
and sandbank construction). Daily water quality measurements (salinity, temperature,
dissolved oxygen and turbidity) will be taken at high tide with a hand-held water quality meter
(Hach HQ40d) at the surface and bottom over a five day period each season (autumn,
winter, spring, summer) (total of 800 measurements over 12 months).
Baseline sediment characteristics will be established through collection of sediment samples
from 50 stations (10 supratidal, 20 intertidal and 20 subtidal) distributed on top and sides of
the existing Central Sandbank in the Port of Durban on four occasions (autumn, winter,
spring, summer) over the course of one year. Intertidal samples will be collected with a hand
corer (10 cm diameter) and subtidal samples collected with a Van Veen grab. Samples will
be placed in sampling jars on ice immediately after collection and submitted to an SANAS
accredited analytical laboratory for determination of grain size distribution, organic and trace
metal (Cd, Hg As, Cr, Cu, Pb, Ni, Zn) content.
The baseline assessment for benthic microalgae biomass will be undertaken through
collection and analysis of sediment samples from the same stations as for the sediment
monitoring activities in accordance with methods prescribed by Pinckney and Zingmark
(1993). Sediment cores will be taken by slowly inserting a plastic pipe of known diameter
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(≈20 mm), either directly into the sediment (in the case of the intertidal samples) or into the
contents of the grab (in the case of the subtidal samples) down to a depth of 40 mm. The
top of the pipe will then be plugged with a bung and a spatula inserted under the bottom of
the tube, before it is slowly withdrawn from the sediment. Samples will then be placed in
sampling jars on ice, protected from light, and submitted to an analytical laboratory where
microalgae biomass will be estimated as total chlorophyll (Chl a) according to the methods of
Whitney and Darley (1979), Dandonneau and Neveux (2002) and Seuront and Leterme
(2006).
The baseline assessment for benthic macrofauna characterisation will be undertaken
through collection and analysis of macrofauna samples from the same stations as for the
sediment monitoring activities. Samples will be collected at four occasions over the year
(autumn, winter, spring, summer). Intertidal samples will be collected at spring low tide by
inserting a large (18 cm diameter) corer into the sediment to a depth of 30 cm, plugging the
open end, extracting the core and transferring the contents to a 0.5 mm mesh bag. The
mesh bag will be agitated until all the fine sediment has been removed and the remaining
contents placed in a sample jar together with 5% formalin. Subtidal samples will be
collected at corresponding times (autumn, winter, spring, summer) using a Van Veen grab
deployed from a small inflatable boat. In all cases, macrofauna from the samples will be
extracted from the residual sediment in the lab, identified to species level, counted and
weighed (wet weight).
The baseline assessment of fish populations along the margins of the Central Sandbank will
be undertaken using a 30 m beach seine net with 12 mm stretched mesh. At least five hauls
will be made on either side of the Central Sandbank on four occasions during the year
(autumn, winter, spring, summer). All fish and invertebrates collected in the net will be
enumerated, weighed and measured, and if possible, returned to the sea alive.
The baseline assessment of birds utilising the Central Sandbank will entail counting all birds
present on the bank once a month for 12 months over spring-low tide periods. Numbers of
birds of each species will be recorded within a series of belt transects spanning the Central
Sandbank. These belt transects will be oriented parallel to the shoreline of the bank along
its southern and northern edges to form a series of blocks which will extend from the waters’
edge up to the middle of Central Sandbank. Counts will be conducted with the aid of
binoculars and telescope within a six hour period.
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It is anticipated that during construction (dredging) phase of the project, the primary impact
vector will be levels of suspended sediment and/or organic material in the water column.
High levels of suspended sediment and organic material can affect living organisms by
reducing levels of dissolved oxygen in the water column (mediated through the
decomposition of organic matter or release of hydrogen sulphide), by blocking the
transmission of light through the water column (thereby affecting phytoplankton and
macrolagal production), by blocking the gills or feeding apparatus of filter feeding organisms
(invertebrates, fish and sharks), or by smothering benthic organisms. (Note that surveys of
the dredge sediment conducted as part of the EIA study (CSIR 2012a) have indicated that
levels of trace metals and other contaminants in the dredge sediments are low and pose
minimal risk to marine organisms). Thus, the focus during the construction (dredging) phase
of the project will be on ensuring that suspended sediment levels in the water column
adjacent to the sandbanks do not exceed a defined threshold risk level of 50 mg/L and that
oxygen levels in the water column do not drop below 5 mg/L (99 % of the time) and
below 6 mg/L (95 % of the time).
These threshold risk level has been derived from the work of Steffani et al. (2003) and from
the South African Water Quality Guidelines (DWAF 1995). Steffani et al. (2003) provided
guidelines for concentrations of suspended solids in relation to the risk they pose to benthic
marine invertebrates, which are considered to be amongst the most sensitive organisms to
elevated suspended sediment levels given that they are mostly sedentary and are unable to
move away from the source of impact, as follows:
Low risk: < 20 mg.L-1
Medium risk: 20-80 mg.L-1
High risk, requiring mitigation: > 80 mg.L-1
The defined threshold risk level of 50 mg/L lies at the centre of the medium risk range as
posed by Steffani et al. (2003).
The SA Water Quality Guidelines recommend that the target levels for dissolved oxygen in
the coastal zone off the south and east coasts should not fall below 5 mg/L (99 % of the
time) and below 6 mg/L (95 %) of the time. These are also the defined threshold risk
levels that have been adopted for this study as well.
With this in mind the following protocol is proposed during the dredging operations:
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1. Continuous monitoring should be undertaken of turbidity and dissolved oxygen levels
at a point immediately adjacent to the Central Sand Bank, between the bank and the
dredger and/or dredge hopper, and at a point immediately adjacent to Little Lagoon
at a point between the Lagoon and the dredger and/or dredge hopper (hereinafter
referred to as “the designated monitoring stations”), during the dredge operations.
2. Data from such monitoring work should be available in real time to the person
coordinating dredging activities.
3. Dredging operations should be halted immediately if (a) turbidity levels exceed a
threshold level of 50 mg/L and/or (b) if levels of dissolved oxygen are observed to
drop below 5 mg/L for more than 1 minutes in every 60 minutes (1.7% of the time) or
below 6 mg/L for more than 3 minutes in every 60 minutes (5% of the time), and
should not recommence until levels have declined below this point.
4. If turbidity frequently exceeds or levels of dissolved oxygen frequently drops below
threshold levels at the designated monitoring stations, ‘Silt Curtains’ should be
deployed at the burrow pit as a mitigation measure. The lower end of the ‘skirt’ of the
silt curtains must be allowed to rest upon the seafloor, and the top of the ‘skirt’ must
be above the water surface.
5. Turbidity should also be minimised by choking the dredge hopper overflow with a
fully automated system. In this scenario, a computerized process controller ensures
dynamic adjustment of the valve in the overflow funnel which chokes the flow in such
a way that a constant fluid level in the hopper is maintained and, as a result, no air is
taken down with the suspension leaving the hopper.
Monitoring will be the last measure. A clearly defined management action has been
identified if, in spite of control measures noted above, TSS levels during the dredge
operations exceed a threshold level of 50 mg.L-1 or dissolved oxygen levels drop
below 5 mg/L (>1% of the time) or below 6 mg/L (>5%) at any of the monitoring
stations, Dredging operations will be halted immediately and will not recommence
until levels have declined below threshold levels.
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7 AMENDED EIA REPORT CONCLUSIONS AND
RECOMMENDATIONS
7.1 Best Practicable Environmental Option (BPEO)
Based on the recommendations of the additional specialist studies, no change to the BPEO
is suggested. A summary of the recommended BPEO is provided below:
The Caisson quay wall alternative was selected due to the following factors:
Poor soil conditions along the quay wall;
Safety considerations;
Low maintenance requirements;
No cathodic protection or specialist coating requirements;
Caissons built within the Port of Durban (at Lot 10) and can be floated into
position and thus no insitu casting of piles is required.
Dredge material from the dredge footprint can be used for the infill of the
Caissons and behind the quay wall at Berth 205 and thus reduces the volume of
dredge material to be disposed of; and
Environmental specialists did not have a preference in terms of quay wall
alternatives.
The Caisson quay wall will be used in combination with Dredge Footprint Option 3G. This
option was selected for the following reasons:
1. The provision of the Caisson quay wall along the western edge of Berth 205 prevents
long term erosion between the Little Lagoon and western edge of Berth 205.
2. The provision of the Central Sandbank Expansion results in a 0.03% net gain in
Central Sandbank habitat. This increases the area of shallow subtidal and interidal
habitats, which are ecologically important, by 49.7% and 4.1% respectively.
3. The use of dredge material in the creation of the Central Sandbank Expansion
decreases the volume to be disposed at the Offshore Disposal Site.
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Figure 17: Preferred Option Combination – Caisson Quay Wall with Option 3G Dredge Footprint.
Offshore Sand Winning will still be necessary. This will take place within Area 1 as
recommended by the Marine Biodiversity Specialist. Further, dredging will be contained
within a sub-area within Area 1 as suggested by the Maritime Archaeologist (Area 1a).
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Figure 18: Area 1a (Preferred Sand Winning Area (Adapted from Maitland, 2012).
This option was selected for the following reasons:
2. Area 1 is more disturbed than Area 2 and the overall impact is likely be less significant
as this site has been used for dredge disposal in the past.
3. Although Area 1 has a known wreck, dredging will be contained to the northern strip
(Area 1a) as shown above and thus there is a lower probability of uncovering potential
Underwater Heritage Sites.
Further, as discussed in the Project Description (Chapter 9), Bayhead Lot 10 will be used at
the site camp, concrete batching area, temporary storage of fuel area etc.
7.2 Environmental Impact Statement
A study undertaken by Transnet (2009) showed that the existing blockwork quays of Berths
203 to 205, (designed in the 1970s), do not meet the required Eurocode 7 minimum
standards of safety and thus risk potential quay wall failure. This resulted in pre-feasibility
study being undertaken by PRDW (2011) which assessed seven possible quay wall
alternatives. These were assessed using a multi-criteria analysis and based on a number of
factors, three quay wall alternatives were selected for further analysis, namely, Caisson,
Sheet Pile and Deck on Pile. An assessment of alternative quay walls was then undertaken
by ZAA (2012). The Caisson option was highlighted as the most appropriate option due to
several factors including, the geotechnical conditions on site, improved safety and stability,
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decreased maintenance requirements and no cathodic protection or specialised protective
coating requirements.
An Economic Impact Assessment was undertaken and found that if the expansion does not
occur significant loss of handling capacity of 284 108 TEUS carried on vessels too large to
be berthed if the depth at Berth 203 – 205 is not increased in the short term. This has a
direct spend loss impact of R1961m, induced spend of R1569m, port related employment
loss of 852 jobs and total employment loss of 3530 over the period of 2016 – 2020.
However, there was some concern regarding the impacts of the proposed project on Durban
Bay Estuary and the Central Sandbank. This led to a number of meetings including a
specialist integration meeting, where the environmental specialists and engineering project
team were provided with an opportunity to discuss the dredge footprint. The need to prevent
long term erosion and decrease habitat loss of the Central Sandbank resulted in a number of
dredge footprint alternatives. These were assessed by numerous studies including the
“Potential Long Term Impact on the Central Sandbank Study” (CSIR, 2012), the Estuarine
Biodiversity Study (Anchor Environmental, 2012a) and the Avifauna Impact Assessment
(Anchor Environmental, 2012c).
These discussions resulted in further discussions and modification of the dredge
alternatives. Further, ZAA (2012a) undertook new ship turning simulations and discussions
with the Port Harbour Master. Through a decrease in the berth channel width, a mitigation
measure of the Central Sandbank Expansion was added (Option 3D). This was further
modified and resulted in Option 3G. This option results in a 0.03% net gain in habitat and no
further expected long term erosion.
The Central Sandbank Study (CSIR, 2012a) found that some residual impact was expected
but that through the mitigation measures, the overall magnitude of this impact was low. The
Estuarine Biodiversity study and Avifauna Study (Anchor Environmental, 2012a and c) found
that habitat loss was the most significant impact. Through the addition of the Central
Sandbank Expansion, this impact was mitigated. In terms of open water habitat loss and soft
bottomed benthic habitat loss, the Estuarine Impact Assessment found that this impact was
not significant due to the disturbed nature of the dredge footprint (i.e. where maintenance
dredging has disturbed the soft-bottomed habitat). Further, the proposed infilling will not
change the tidal prism in such a way to effect water or sediment quality.
Modelling of turbidity was also undertaken by ZAA (2012b) in order to determine the impact
of dredging on turbidity within Durban Bay. The findings show that turbidity levels are
expected to be below medium to high risk levels. This impact was also verified by the
Estuarine Biodiversity Specialist. Sediment Analysis was undertaken by the CSIR (2012c) in
order to determine the quality of sediment within the dredge footprint. Heavy metal
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concentrations were below warning levels and no toxic effects are expected. The findings of
this study suggest that the dredge material is safe for offshore disposal and should not pose
a significant threat to organisms at the disposal site.
The proposed project also includes the offshore sand winning for infill material. The offshore
sand winning study (Anchor Environmental, 2012b) found that Area 1 was previously
disturbed and was likely to re-colonise within 1-2 years. The impact on soft-bottomed benthic
fauna was not thought to be significant. Modelling of changes in bed shear stress (and
resultant possible erosion) of North and South Beach was also undertaken for Offshore
Disposal Site. Turbidity and changes in bathymetry will be greatest at the Offshore Disposal
Site and thus only this was modelled, however the results were used to add value to the
Offshore Sand Winning Study. No change in bed shear stress was noted (ZAA, 2012b).
Further, modelled turbidity for disposal (and thus for sand winning which results in less
sediment loading of the water) showed that turbidity was highest at the point of disposal but
dispersed quickly to levels which were below the medium to high risk levels.
Two Underwater Heritage Impact Assessments were undertaken, namely for the dredge
footprint within the Port of Durban and for the two potential sand winning sites (Area 1 and
Area 2). One known shipwreck (a 30 feet steel hull of a wreck called Stuart’s wreck) was
found in Area 1. Numerous magnetometer anomalies were found in both sites. These are
thought to be of low significance. The Maritime Archaeologist has suggested a portion of
Area 1 be made available for dredging of infill material. Within the Port of Durban, no
landside archaeological features will be impacted as the infrastructure on site is less than 60
years old. Some magnetic anomalies were noted within the Port but these could not be
verified. Based on this, the specialist has recommended that the dredging may take place as
long as certain mitigation measures are taken into account. These are provided in the suite
of EMPrs.
The Ecological Risk Assessment Report (CSIR and Anchor Environmental, 2014),
concluded that given the long term engineering stability of the proposed new sandbank
habitat, initial colonisation, succession and the establishment of an ecologically functioning
benthic community is certain. Further, given the proximity of this sandbank to the existing
Central Sandbank and its similarity in terms of structure, granulometry and hydrodynamic
characteristics, it is highly likely that a similar biological community will develop. Minor
differences should be expected and will probably beneficially increase benthic diversity in the
Bay. Successful establishment of benthic biota will result in profitable utilisation of the
created habitat by higher trophic level organisms (fish and birds). Fish especially will benefit
from the creation of additional shallow intertidal and subtidal habitat. These habitats are the
primary feeding areas for juvenile estuarine dependent species utilising Durban Bay as a
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nursery. Shallow subtidal area is especially important. The present configuration and
bathymetry of Durban Bay, with a strong predominance of deep water habitat or intertidal
habitat, and limited shallow subtidal habitat, reduces its value as a fish nursery. Shallow
water offers juvenile fishes protection from predation by piscivorous fishes (Blaber 1987,
Ruiz et al. 1993). Such habitat is limited in Durban Bay at low tide, leaving juvenile fishes
susceptible to predation. The proposed sandbank extension results in significant increases
in these shallow water habitats and will fulfil an ecological role that is congruent with the
Bay’s ecological value as an estuarine embayment. Indeed in the long term it will improve
the systems ecological value.
However if after 5 years of monitoring it is found that abundance at the Extended Sandbank
does not reache 80% of the average level measured at the control sites, Transnet will enter
into discussions with the DEA regarding the potential for an offset plan.
The Extension of Sandbank Engineering Risk Assessment report (ZAA Engineering, 2014a)
summarised the work that has been carried out as part of the FEL‐3 study and has
addressed in particular the engineering issues, with respect to the extension of the central
sandbank, raised by the Department of Environmental Affairs in its letter Ref
14/12/16/3/3/2/275 signed on 21 October 2013 and issued in response to the initial EIA
Report, by means of the following:
A comprehensive Risk and Mitigation Analysis covering both the construction of the
extension and the maintenance of the sandbank during the operational phase of the
new container terminal at Pier
Development of a Method Statement for the construction of the sandbank
Hydrodynamic and morphological analyses of the Port of Durban using DELFT‐3D
to determine the short and long term stability and form of the extended sandbank,
including the effects of wave penetration, wind and currents due to tidal movements
and other effects. These studies indicate that the extended sandbank will be stable
and that it will not endanger the stability of the existing sandbank during
construction, or during operation of the container terminal. It also indicates that
flows will not change in the area of the Little Lagoon and this, combined with the
sheet pile protection to be installed, will ensure that the Little Lagoon is not
disturbed.
Hydrodynamic analyses have been carried out to assess the levels of turbidity and
total suspended solids (TSS) that will result from the dredging operations and the
studies have confirmed that levels will be within acceptable limits.
Geotechnical finite element analyses have been carried out using the computer
programme PLAXIS to ensure the stability of the sandbank extension.
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An extensive on site geotechnical investigation (involving Cone Penetrometer
Testing with pore water pressure data (CPTu) and proof drilling and logging) has
been carried out to determine the nature and suitability of the sands that will be
dredged from the basin, for use in the construction of the sandbank extension.
Comprehensive dredging analysis and design has been carried out.
This report showed that all risks were mitigated to a ‘’minor’ impact.
The Effects of Climate Change on Engineering Design Report (ZAA, 2014b) reviewed and
summarised available literature on parameters affected by climate change that are relevant
to the marine engineering design for this project. The IPCC, (2013) Climate Change 2013,
has been adopted as the primary reference for this report. This is in agreement with IPCC
AR4 (2007), together with the scaled up ice sheet discharge allowance, projected from 2095
to 2100. This has been supplemented by guidelines produced by UK Climate Projections
Report June 2009 (UKCP09) and the National Committee on Coastal and Ocean
Engineering, Engineers Australia..
The parameters listed below are those that can be affected by climate change and are
relevant to the marine engineering design. These parameters have been taken into
consideration in the design of the proposed quays and associated dredging works:
Long term sea level rise
Storm surge (wind setup, pressure deficit, wave setup)
Temperature
Wind (including tropical cyclones)
Currents
Waves
Rainfall
Ocean acidification
The study demonstrates that the chosen cope level of +4.25m CDP is sufficient, providing a
freeboard of 0.324m over and above the allowed for accumulation of various upper bound
increases for climate change affected parameters.
The risks and vulnerability of the new quays to climate change, and in particular sea level
rise and storm surge, have been minimised and that the selected cope height of 4.25 m
originally proposed by Transnet for this project is safe, conservative for its design life of 50
years from the projected completion date of 2019 and that a safe freeboard will still exist. In
fact, given the year 2100 projection values, the structure is likely to be safe for a further 32
years after 2069. In all cases this is in the event of the simultaneous occurrence of all factors
affecting the water level in the Port.
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Various improbable extreme scenarios (e.g. UKCP09 H++) have been taken into account
when evaluating the design in terms of contingency planning in the event of these extreme
scenarios.
Other climate change affected parameters such as wind, rainfall and ocean acidification
have been taken account during the design of the quay structures, storm water system and
concrete specification.
The threat of flooding during the construction phase has been evaluated and we conclude
that construction will not adversely affect the current levels or increase the risk or
vulnerability to flooding.
Based on the additional risk and vulnerability assessment studies undertaken to address
DEA’s comments, the Central Sandbank Extension is deemed a rational and acceptable
mitigation measure that has a high likelihood of success in terms of colonisation and
succession. In terms of engineering design, DELFT-3D models have shown that the
Sandbank Extension is stable and will require no long term maintenance. Mitigation
measures have been provided in this Annexure as well as the monitoring protocol required
to determine the baseline thresholds. The Sandbank Extension has a very low likelihood of
failure, however should this happen, the ecological implications would be similar to the
original Option 3C dredge footprint (5.6% loss of habitat and associated loss of functioning).
The biggest socio-economic impact of this loss would be related to recreational and
subsistence fishing (due to the loss of nursery habitat). However, it should be noted that the
Central Sandbank Extension will increase nursery habitat and thus will have a positive socio-
economic impact in this regard.
In regards to Climate Change, risk and vulnerabilities of the Port to changes in Climate have
been taken into account through the engineering design.
Thus, with the selection of the BPEO for the quay wall alternatives, dredge footprint and
offshore sand winning site, the adoption of the mitigation measures included in the Amended
EIA Report and original EIA report and the dedicated implementation of the suite of EMPrs, it
is believed that the significant environmental aspects and impact associated with this project
can be suitably mitigated. With the aforementioned in mind, it can be concluded that there
are no fatal flaws associated with the project and that authorisation can be issued, based on
the findings of the specialists and the impact assessment, through the compliance with the
identified environmental management provisions.
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7.3 Amended EIA Report Recommendations
The following key recommendations, which may also influence the conditions of the
Environmental Authorisation (where relevant), accompany the Amended EIA for the Berth
203 to 205 Expansion:
1. The mitigation measures contained in additional specialist studies must be taken into
account;
2. Baseline monitoring as described in CSIR and Anchor Environmental (2014) must be
undertaken;
3. The Sandbank Extension must be undertaken as set out in ZAA Engineering
(2014a);
4. Monitoring during the Sandbank Extension and Dredging must be undertaken as per
CSIR and Anchor Environmental (2014) requirements;
5. Transnet will enter into discussions with the DEA regarding the potential for an offset
plan if after 5 years the extended sandbank does not meet the required
abundance;and
6. All mitigation measures regarding climate change must be taken into account as per
ZAA Engineering (2014b).
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