DEPARTMENT OF INDUSTRY - LANDS
Eden Breakwater Wharf Extension Project Final Dredging Plan
301020-07698 – MA-PLN-0002
26 August 2016
Level 12, 141 Walker Street, North Sydney NSW 2060 Australia Telephone: +61 2 8923-6866 Facsimile: +61 2 8923-6877 www.worleyparsons.com ABN 61 001 279 812 © Copyright 2016 WorleyParsons Services Pty Ltd
DEPARTMENT OF INDUSTRY - LANDS EDEN BREAKWATER WHARF EXTENSION PROJECT FINAL DREDGING PLAN
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CONTENTS
1 INTRODUCTION ................................................................................................................ 1
1.1 Context ................................................................................................................................ 1
2 PROJECT PROPOSAL ...................................................................................................... 2
2.1 Location and Extent of Proposed Dredging ........................................................................ 2
2.2 Sedimentation and Survey Tolerance ................................................................................ 2
2.3 Geotechnical Information .................................................................................................... 3
2.4 Design Profiles in OTR Materials ........................................................................................ 4
2.5 Design Profiles in Rock and Rock-Like Materials ............................................................... 5
2.6 Material Quantities .............................................................................................................. 5
2.7 Scour Protection ................................................................................................................. 6
3 SEDIMENT CHARACTERISTIC ......................................................................................... 7
3.1 Physical Characteristic ....................................................................................................... 7
3.2 Geochemical Characteristic ................................................................................................ 7
3.3 Potential Acid Sulfate Soils ................................................................................................. 9
4 DREDGING METHODOLOGY ......................................................................................... 10
4.1 Findings of Earlier Report ................................................................................................. 10
4.1.1 Dredging Plant Options ........................................................................................ 10
4.1.2 Disposal Options .................................................................................................. 11
4.1.3 Commentary on Present Status ........................................................................... 11
5 DETAILED DESIGN WORKSHOP ................................................................................... 13
5.1 Comparison of Options ..................................................................................................... 16
6 CONCLUSION .................................................................................................................. 17
7 REFERENCES ................................................................................................................. 18
APPENDIX A - DRAWING 301020-07698-MA-DWG-3002 REV A ................................................. 19
APPENDIX B – DREDGE METHODOLOGY WORKSHOP REPORT ............................................ 20
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1 INTRODUCTION This document presents the Final Dredging Plan for the Eden Breakwater Wharf Extension project
(Project). Dredging is required in the maneuvering area and the berth pocket, to enable the expected
cruise ships and other vessels to safely arrive and depart from the berth at all states of the tide.
1.1 Context This document supplements the Concept Design Dredging Plan Reference 301020-07698-MA-PLN-
0001 dated 22 July 2015. The earlier plan (July 2015) identified a broad range of options for the
disposal of the dredged material.
Refinements have been made to the design of the berths and basin. These changes do not
fundamentally alter the outcomes of the earlier plan (July 2015). However, safety, environment,
schedule and cost considerations warrant a review of the dredging scope and support for a Sea
Dumping Permit (SDP) application.
This document contains a:
Description of the final design solution;
Summary of sediment characteristics;
Review of the July 2015 dredging equipment and work methods;
Evaluation of combined TSHD and BHD dredges versus BHD only leading to shorter
execution period.
Further recommendations to improve outcomes
There are no changes which affect the earlier plan’s disposal destination. Some elements of the
earlier plan are repeated herein where relevant for completeness.
Breakwater Wharf
Multipurpose Jetty
Multipurpose Jetty
Mooring Jetty
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2 PROJECT PROPOSAL
2.1 Location and Extent of Proposed Dredging The design footprint proposed for the dredging is shown in Drawing 301020-07698-MA-DWG-3002
Rev A contained in Appendix A.
A design dredge level of -10.5 m CD was adopted in the earlier plan. The basis of this estimate is
contained in the earlier plan and derived using a maximum vessel size equal to the 311m length
Voyager Class. This vessel has a draft of 8.8m.
The final design maintains a design dredge level of -10.5m CD and accommodates a maximum
vessel length of 325m. This includes the Norwegian Breakaway Class vessels which have a draft of
8.6m. Further dynamic mooring analyses (refer WorleyParsons Report no. 301020-07698-MA-REP-
0003, dated 8 August 2016) have confirmed that there is sufficient under-keel clearance for both
Voyager Class and the Norwegian Breakaway Class vessel during all states of tide. These are the
largest vessels able to use the berth.
The width of the dredge pocket has also been verified by separate navigation simulations undertaken
at the Smartship facility (refer to Smartship Eden Breakwater Wharf Extension Simulation Report
prepared for WorleyParsons Services, 21 September 2015).
2.2 Sedimentation and Survey Tolerance There are no inflowing sediment carrying rivers near the site. Therefore, sources of sedimentation
would be mainly littoral drift and re-distribution of material from propeller action.
The isopach diagram contained in the earlier plan indicated a uniform distributed average accretion of
approximately 0.2 m over the 4 year period in between 2011 and 2015.
The final design adopts an allowance of 0.3 m in addition to that provided by the overdredging
required to achieve the designed profile to survey tolerance. A typical survey tolerance for precision
bathymetric surveys is within 0.1m depending on the weather conditions at the time the work is
undertaken.
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2.3 Geotechnical Information The sediment is predominantly sand with some silt, clay and gravel, and shallow weathered and
fractured rock located at the north eastern end of the site. The sand is generally very loose to loose,
with some areas that are medium dense.
The location of the boreholes and rock level encountered from the March 2015 fieldwork by Tectonic
is shown in Figure 2-1
For a design dredge level of -10.5 m CD plus overdredging, rock would be encountered around the
area of BHT1 (top of rock level at -5.7 m CD), BHT6 (top of rock level at -6.75 m CD) and extending
generally south-west towards BHT9 (top of rock level at -13.4 m CD).
Drawing 301020-07698-MA-DWG-3002 Rev A contained in Appendix A shows the dredge zones
and indicative rock footprint area at the proposed dredge depth of -10.5m CD.
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Figure 2-1: Location of boreholes and level to rock surface shown as yellow text (Tectonic, 2015) (NE – not encountered, i.e. no rock was encountered in the corresponding borehole)
2.4 Design Profiles in OTR Materials The available geotechnical information indicates the other than rock (OTR) material removed within
the dredging footprint will be predominantly sand with some silt and clay. The sand is generally very
loose to loose, with some areas that are medium dense. A maximum slope of 1 in 10 (vertical to
horizontal) is adopted in the final design dredge batters in sandy materials. Where scour protection is
necessary a typical batter slope of 1 in 3 has been adopted.
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2.5 Design Profiles in Rock and Rock-Like Materials The final design adopts a 1 in 1 slope in bedrock and a nominal 3m bench in front of the existing
sheet pile cells.
2.6 Material Quantities The final dredge basin design comprises two zones. Zone 1 contains rock and rock-like materials
underlying a shallow bed of sediments. Zone 2 is expected to comprise of sediments only.
The dredging quantities for these materials are provided in Table 2.1 and are based on the following
final design criteria:
Dredge basin level (clearance depth) -10.5m CD
Dredge basin at scour protection mattress (refer Section 2.7) -11.5 m CD
Dredge basin at sediment trap (refer Section 2.8) -12.5 m CD
Overdredge allowance (average) 0.5 m
Table 2.1: Preliminary dredging quantities
Zone Materials Description
Total Volume to dredge line and level,
(m3)
Approx. volume of rock to dredge line and level, (m3)
Approx. volume of
OTR to dredge line and level,
(m3)
Estimated overdredge,
(m3)
Total Volume
including overdredge allowance,
(m3)
1
OTR, rock and rock-like materials
15,000 6,000 9,000 3,500 18,500
2 OTR 158,000 0 158,000 55,000 213,000
Totals 173,000 6,000 167,000 58,500 231,500
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2.7 Scour Protection
Scour protection will be needed over a portion of the berth pocket to protect existing and new structures from undermining or loss of structural integrity from scouring forces associated with ship propulsion systems, and tug operations.
Installation of a scour mattress requires localised deepening of 1.0m to allow for thickness of the mattress and tolerances for future maintenance dredging if required. Scour protection will not be required to protect rock batters or other areas of the dredge basin where scouring will not impact on existing structures.
Scour protection will be installed immediately following dredging works and by the dredging contractor.
2.8 Sediment Trap
The proposed dredge plant will not be able to access the seabed below the outer end of the Multipurpose Jetty. Therefore, a 1V in 10H batter slope above the toe line cannot be formed near the seaward end of the Multipurpose Jetty. A natural slope which is steeper than 1 in 10 is expected to form following dredging. To allow for gradual infilling over the years following dredging, a sediment trap has been incorporated into the final design.
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3 SEDIMENT CHARACTERISTIC A summary of the sediment characteristics are provided below based on the results and findings as
outlined in the Eden Breakwater Wharf Extension, Sediment Sampling and Analysis Plan
Implementation Report (Australasian Marine Associates, 1 October 2015, Rev 1).
3.1 Physical Characteristic The physical characteristics of the sampled sediments are summarised in Table 3.1.
The sediments are dominated by the sand fraction with a mean of 83% sand with minor components
of clay and silt (maximum of 11% of silt and clay) and variable percentage of gravels of up to 32%.
Table 3.1 Summary of Sediment Particle Size Analyses
Cla
y (<
2 µm
) (%
)
Silt
(2-6
0 µm
) (%
)
Sand
(6
0 µ
m-2
mm
) (%
)
Gra
vel
(>2
mm
) (%
)
Cob
bles
(>
6 cm
) (%
)
No of Samples 44 44 44 44 44
Mean 5 2 83 10 <1
Standard Deviation 2 1 10 9 -
Maximum 8 4 96 32 <1
Minimum 1 <1 61 1 <1
3.2 Geochemical Characteristic Key findings on the geochemical characteristic of the sediments are outlined below:
95% upper confidence limit (UCL) concentrations of the mean for the potential contaminants
of concern were below their respective National Assessment Guidelines for Dredging (NAGD)
(2009) Screening Levels with the exception of tributyltin (TBT);
95% UCL of the mean concentration for tributyltin (TBT) (normalised for 1% Total Organic
Carbon) was above the NADG Screening Level but below the Sediment Quality High Values.
This was due to several elevated TBT concentrations reported in the surface sediments at
some sites. The highest normalised TBT concentration of 113.5 µg/kg was reported at Site 5
located approximately 100 m from the existing multipurpose jetty and approximately 400 m
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from the slipway. The other sites were located closer to the existing multi purposes jetty and
greater than 100 m from the slipway;
It was concluded in the AMA report that such TBT levels were likely resulting from general
boating activities and not directly related to boat maintenance activities at the slipway
Further elutriate tests returned TBT concentrations below the detection limit of the analytical
equipment (< 2 ng/L). These results confirm that the bioavailability of TBT is low and that the
TBT is likely to be tightly bound to the organic material present in the sediment;
All samples had organochlorine pesticide concentration below the Limit of Reporting;
One individual concentration of silver exceeding the NAGD Screening Level and the 95%
UCL of the mean concentration for silver was below the NAGD Screening Level;
95% UCL of the mean concentrations for the potential contaminants of concern were below
the General Solid Waste CT1 (contaminant threshold) and National Environment Protection
Measure (NEPM) Health-based Investigation Level (HIL) A (for low density residential
including a sizeable garden which represents the land-use category with the most exposure).
The Environmental Protection Authority of NSW, under the Environmentally Hazardous Chemicals
Act 1985, has issued a Chemical Control Order (CCO) In Relation to Organotin Wastes. The CCO
sets controls on the disposal of all solid or liquid organotin wastes generated during the application or
removal of antifouling paint. The EPA states that:
“The CCO only applies to dredged sediments contaminated with organotin where these are
clearly associated with facilities used to apply or remove organotin products (this is likely to
include, for example, sediments immediately adjacent to slipways).”
(http://www.epa.nsw.gov.au/pesticides/ccos.htm)
As the sediments proposed for dredging as part of the Eden Breakwater Wharf Extension are not
directly adjacent to the local slipway and has a 95% UCL of the mean concentration level of TBT
below the Sediment Quality High Values, the CCO is not considered to be applicable to the dredged
sediments.
Based on these findings, Australasian Marine Associates concluded the sediments are considered
suitable for dredging and either offshore or onshore disposal.
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3.3 Potential Acid Sulfate Soils All of the sediment samples (45 samples) returned a net acidity of less than 0.02% oxidisable sulfur.
Australasian Marine Associates concluded that the acid production potential of the sediments is low.
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4 DREDGING METHODOLOGY
4.1 Dredging Plant Options
The Concept Dredging Plan compared the use of a Backhoe Dredge (BHD), Cutter Suction Dredge
(CSD) or Trailer Suction Hopper Dredger (TSHD) working independently over the entire dredge
footprint.
The report recommended a medium sized BHD for the following main reasons:
Availability of three vessels of this type operating in south east Australia and New Zealand
The three BHD’s are expected to be able to dredge most, if not all, of the fractured rock that
may be encountered without secondary pre- treatment.; and
The material can be dredged at or near its natural moisture content to minimise the
generation of plumes.
The report also concluded that
The use of a CSD was possible, although limited by available land areas on the nearby
shoreline to contain and dewater the dredged materials which contain typically 70 percent
water and 30 percent solids.
The use of a TSHD was also limited to areas where there was adequate sea room to
manoeuvre and dredge to the required profile. Also, a TSHD cannot dredge rock like
materials and is expected to generate higher levels of turbidity than a BHD through dredging,
overflow and the action of the propellers if operated economically.
The TSHD dredges by pulling a drag head across the seafloor, mobilising the seabed material into
the water column, while sucking the subsequent water and suspended material up through the drag
head. This mixture of water and dredged material is then pumped through external pipes into a
hopper. Heavier particles settle to the bottom of the hopper and lighter particles remain in suspension
within the hopper. Once the hopper is full of water, the hopper is typically allowed to overflow with the
low-density mixture overflowing back into the sea, while continuing to capture the denser material
within the hopper. This reduces the number of trips required from the dredge area to the offshore
disposal area and therefore reduces the overall duration of the dredging campaign. Sediment is
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introduced into the water column from the TSHD near the seabed at the drag head and from propeller
wash, and near the surface from the overflow.
4.2 Disposal Options
The Concept Dredging Plan contains a comprehensive assessment of options for disposal or
beneficial use of dredged materials. These options included:
Part use onsite as fill for the proposed berth extension on leeward side of existing
breakwater;
Part use offsite as fill at northern end of Eden Harbour for proposed carpark, Cocora Beach
nourishment, disposal or stockpile at the former BP tank farm site and disposal/stockpile at
Imlay Street opposite the port;
Land disposal;
Sea disposal at Yallumgo Cove; and
Offshore disposal.
The report identified that in the absence of large onshore ODSs offshore disposal was the only
feasible option. This situation is unchanged for the final dredge plan.
4.3 Commentary on Present Status
Since the Concept Dredging Plan some refinements have been made to the design of the dredge basin including:
The berth pocket has been defined (refer to Drawing 301020-07698-MA-DWG-3002 Rev A - Appendix A)
Some 231,500 m3 (net) of dredged materials is expected to require dredging. This includes an average over-dredge allowance of 0.5m over an area of 116,500 m2 but excludes contingency from sedimentation since the time of the most recent hydrographic survey (2015).
Approximately 6,000 m3 of rock or rock like materials is included in the above figure.
Given the above volumes and current industry knowledge, further consideration was given to the safety, environmental, schedule and cost aspects of the Work.
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A Workshop held on the 4th August, 2016 reviewed the proposed work method (i.e. BHD and hopper barges) identified in the Concept Dredging Plan. The outcomes of this evaluation are contained in Section 5.
4.4 Secondary Pre-treatment of Rock
The final design will require dredging of bedrock at the inshore end of the berth pocket. Initial consultation with the dredging industry has determined that the most likely available dredge plant will be able to remove this rock with minimal need for pretreatment. However, there is always a risk that rock within the dredging envelope proves difficult to extract by direct dredging and requires some form of pre-treatment prior to removal by the dredge. Common types of mechanical pre-treatment include rotating drums “Drumcutter” which act similar to a road header and ripper devices which act similar to onshore excavator ripper attachment.
Rotating drums cutters are independently powered and vary in size from about 150kW to over 400kW and these attach to the end of the dredge boom which exerts a downward pressure on the rock surface in combination with the rotary motion of the drum’s cutters to break down the rock to manageable sizes for later removal by the dredge.
The ripper device is a single or multi-pronged tine attached to the boom of the dredge. This device relies entirely on the capacity of the dredge to disintegrate rock. Ripper tines can also be incorporated into rock dredging buckets.
Secondary pre-treatment may be required in isolated locations within Zone 1.
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5 FINAL DESIGN WORKSHOP, 4 AUGUST 2016
The final design workshop was undertaken to compare the relative pro’s and con’s for a dual dredge
spread (using a BHD in combination with a TSHD) compared to a single medium sized BHD
operating independently. The principal objective of the workshop was to establish if the
environmental assessment process, related studies and tender documents are to allow for potential
use of a TSHD to undertake part of the dredge works.
The workshop assumptions were as follows:
The TSHD would be sourced locally (Australia or NZ based)
Safety was rated as a priority over environmental performance, schedule and cost
Environmental performance was rated a priority over cost
No changes to the disposal location which is in open waters, 6nm from the site and
approximately 60m water depth
Predominant upper sediments comprising materials being sands (>80%) as per Section 3.1.
For all options, work would be carried out on a 24 hours, 7 days a week basis. A shorter duration
time is beneficial in reducing any risk of harm to the environment, regardless of the dredging method.
5.1 Description of Dredge Methodology Options
5.1.1 Option 1 BHD (Base Case) The backhoe dredger excavates material and places into the accompanying hopper barge(s). The
material is then transported and disposed by bottom dumping in the marine disposal area. This
method generally requires two barges to facilitate continuous dredging. For a disposal ground within
6.0 nautical miles, each barge would require a hopper capacity of 900 to 1200 m3. The BHD removes
material at or near its natural moisture content to minimise the generation of plumes. The BHD is an
essential component of the dredge project as it will be the only effective means of removing rock.
Typical plant likely to be used to fulfil the above dredge method includes:
Medium BHD currently in use in the region (equivalent to approx. 200 tonne excavator and up
to 10m3 bucket capacity);
Two appropriately sized barges (i.e. 900 m3 to 1,200 m3) in size either towed by tugs or self-
propelled; and
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Appropriately sized tugs or work boats to assist with dredger positioning, move barges and
take barges offshore as necessary.
In addition to the base case option of using a BHD for dredging and hopper barge to transport the
material to the offshore spoil ground, there are two additional methods which are considered
viable/feasible for dredging work at Eden. These are described below:
5.1.2 Option 2 BHD + TSHD (Single handling method) This involves bulk dredging of OTR materials using the TSHD and use of the BHD and hopper barges
to remove rock and sediments near existing structures and in areas where the TSHD cannot
manoeuvre. It is envisaged the TSHD would undertake most of the dredging of Zone 2 and the BHD
would dredge Zone 1 and a portion of Zone 2, including areas alongside the existing Multipurpose
Jetty and Breakwater Wharf. In this scenario both dredges would transport dredged materials directly
to the Offshore Disposal Site (ODS). The BHD would require two barges in the order of 900 to
1200m3 for efficient operation and one tow vessel. A towed barge would achieve up to 6 knots in
open waters. Accordingly, return transit times of 2 to 3 hours would be expected for each barge
movement.
The single handling method:
Reduces barge movements to ODS, increases the safety of dredge operations and reduces
the risk to other users.
Has the potential to reduce the execution time by up to 30% to approximately 10 weeks; and
Reduces the overall cost of the works by up to 20% compared to the base case method.
Typical plant likely to be used to fulfil the above dredge methods include:
Medium BHD currently in use in the region (equivalent to approx. 200 tonne excavator and up
to 10m3 bucket capacity);
Two appropriately sized barges (i.e. 900 m3 to 1,200 m3) in size either towed by tugs or self-
propelled;
Appropriately sized tugs or work boats to assist with dredger positioning, move barges and
take barges offshore as necessary; and
TSHD such as the MV Brisbane (2,900m3 hopper capacity).
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5.1.3 Option 3 BHD + TSHD (Partial Double-handling method) In order to maximise overall safety during the works, this method uses the TSHD to deliver most (if
not all dredged materials to the ODS. Most of the material would be bulked out direct by the TSHD.
Material in areas inaccessible or containing material too hard for a TSHD would be dredged by the
BHD and loaded into hopper barge(s). The hopper barge(s) would bottom dump the material in deep
water within the dredging footprint in an area accessible by the TSHD. Any large rock that cannot be
handled by the TSHD would either be disposed of elsewhere within the site (e.g. along the lee side of
the breakwater) or at the ODS.
The partial double-handling method:
Minimises barge movements to ODS, maximises the safety of dredge operations and
minimises the risk to other users.
Has the potential to reduce the execution time by up to 50% to approximately 6 weeks;
Reduces the overall cost of the works by up to 30% compared to the BHD option; and
Requires a temporary stockpile site within the dredge footprint. A suitable site which could be
considered in the environmental impact assessment would be the lee-side of the existing
breakwater in between the fender line of the proposed wharf and the toe line of the
breakwater. This site is in approximately 8m of water, and is sufficiently clear from moorings
and other marine structures to allow continued access to these assets.
Typical plant likely to be used to fulfil the above dredge methods include:
Medium BHD currently in use in the region (equivalent to approx. 200 tonne excavator and up
to 10m3 bucket capacity);
Two appropriately sized barges (i.e. 900 m3 to 1,200 m3) in size either towed by tugs or self-
propelled;
Appropriately sized tugs or work boats to assist with dredger positioning, move barges and
take barges offshore as necessary; and
TSHD such as the MV Brisbane (2,900m3 hopper capacity).
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5.2 Comparison of Options
Each of the three options were compared and scored on the following criteria in the form of a Multi-Criteria Decision Analysis (MCDA) process. This provides a structured method for determining the relative merits of options which are used to inform a decision on which options to consider further in environmental assessment studies.
Each option can be compared in regard to the following criteria:
1 Safety of Construction 2 Environmental Performance 3 Cost
Inputs and outputs from the MCDA process are contained in Reference 301020-07698-MA-REP-0011, contained in Appendix B. Figure 5-1 contains the summary findings.
Figure 5-1 – MCDA Options Analysis Output
Criterion Importance (Weight) / 101. Safety 10 Please key in yellow cells
2. Environmental 8
3. Cost 6
Dredging Options Description
1. S
afet
y
Wei
ghte
d S
core
2. E
nvi
ron
men
tal
Wei
ghte
d S
core
3. C
ost
Wei
ghte
d S
core
SUM RANK
A. Backhoe Dredger (medium)Medium BHD undertakes all dredging and
disposal off-shore2 20 4 32 2 12 64 3
B. Backhoe Dredger and TSHD (single handling)
TSHD to bulk out sands and BHD to clean-
up, dredge rock and tight corners not
accessible by TSHD
3 30 3 24 4 24 78 2
C. Backhoe Dredger and TSHD (double handling)
BHD to dredge rock and tight corners not
accessible by TSHD and stockpile within
the dredge footprint in deep water for
TSHD to transport to offshore disposal site
5 50 2 16 5 30 96 1
Note:
(a) Cost assumes approx. 230,000 cu.m of dredged materials (including 10,000m3 of rock).
Scoring Guide Scores range from 0 = Unsatisfactory, to 5 = Excellent
1. Safety
Score 5 if option offers highest safety to construct
Score 0 if option is not safe to construct
2. Environmental
Score 5 if option has only positive environmental effects
Score 0 if option is detrimental to the surrounding environment
3. Cost
Score 5 for option with lowest overall cost
Score 0 for option with highest cost
Score other options the resultant scale
Criteria Affecting Dredging Equipment
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6 CONCLUSION
The detailed design workshop determined that there are significant benefits to be realized by allowing the bulk of the dredging work to be undertaken by a TSHD working in combination with a BHD.
These benefits extend to improved safety of dredging operations, time and cost savings. Options 2 and 3 also offer potential improved environmental outcomes as these options involve a reduced timeframe for dredging activities at the site.
The final dredge plan concludes that further dredge plume modelling and other environmental assessment studies should consider all three options for the project.
Subject to further environmental assessment studies, it is recommended that TSHD plant not be precluded from the RFT process. This will ensure the minimum execution risk and best value for money outcomes for the project.
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7 REFERENCES
Australasian Marine Associates (2015), Eden Breakwater Wharf Extension Sediment Sampling and
Analysis Plan Implementation Report, prepared for NSW Trade and Investment (Crown Lands), 1
October 2015.
Commonwealth of Australia (2009), National Assessment Guidelines for Dredging, Canberra.
MHL (2007), Eden Harbour Wave Study, Report MHL1742, August 2007.
PIANC (2014), Harbour Approach Channels Design Guidelines, PIANC Report No. 121.
Smartship (2015), Eden Breakwater Wharf Extension Simulation Report prepared for WorleyParsons
Services, 21 September 2015
Tectonic (2015), Geotechnical Investigation Factual Report, Breakwater Wharf Extension Eden,
NSW, Report for Australasian Marine Associates, Report no. 15001-004-Rev0, 24 April 2015.
WorleyParsons (2016), Eden Breakwater Wharf Extension Dynamic Mooring Analysis of Cruise
Vessels at Berth prepared for Department of Industry (Lands), 8 August 2016.
WorleyParsons (2015), Eden Breakwater Wharf Extension Project, Dredging Plan prepared for NSW
Trade and Investment (Crown Lands), 22 July 2015.
DEPARTMENT OF INDUSTRY - LANDS EDEN BREAKWATER WHARF EXTENSION PROJECT FINAL DREDGING PLAN
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APPENDIX A - DRAWING 301020-07698-MA-DWG-3002 REV A
DEPARTMENT OF INDUSTRY - LANDS EDEN BREAKWATER WHARF EXTENSION PROJECT FINAL DREDGING PLAN
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APPENDIX B – DREDGE METHODOLOGY WORKSHOP REPORT
(Ref 301020-07698-MA-REP-0011-A)
www.advisian.com
Eden Port Development ProjectBreakwater Wharf Extension
Dredging Methodology Review
Workshop 4 August 2016
Doc: 301020-07698-MA-REP-0011-A
Advisian / 2
Attendees
• Andrew Dooley – Project Manager - Department of Industry – Lands
• Ron Hutchinson – Baggerman Associates – Dredging Advisor
• Paul Moses – Principal Maritime Engineer – Project Manager – Design
• Mike Crandell – Construction Manager – Advisian – EBWE
Safety Moment
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Meeting Objective & Agenda
OBJECTIVE:
To discuss whether or not to allow the use of TSHD in combination with a BHD for dredging works. This decision needs to be made to inform other investigations and
the RFT.
AGENDA:
1. Context
2. Dredging Particulars
3. MCA Assessment
4. Conclusion
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Dredging Particulars
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• Material Bank Volumes (allowing for average 0.5m overdredging)
• Circa average 80% sand fractions in OTR
• Circa average 10% silt and clay fractions in OTR
• Circa average 10% gravel and cobble fractions in OTR
• Circa 6000 m3 bedrock
• Circa 173,000 m3 total dredge volume over 116,500 m2
• Say 231,500m3 including overdredging allowance
• Disposal site in open waters
• 6Nm from site
• 60m water depth
Proposed Dredging GA
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Project Location/ Offshore Disposal Area
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Options
OPTION:
A. Backhoe Dredger
B. Backhoe Dredger and TSHD
C. (single-handling)
D. Backhoe Dredger and TSHD
E. (double-handling)
DESCRIPTION:
Medium BHD undertakes all dredging and disposal off-shore
TSHD to bulk out sands and BHD to clean-up, dredge rock and tight corners not accessible by TSHD
BHD to dredge rock and tight corners not accessible by TSHD and stockpile within the dredge footprint in deep water for TSHD to transport to offshore disposal site
Hard rock could either be taken to sea by barges or disposed of along breakwater toe
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Criteria
CRITERION:
A. Safety
B. Environment
C. Cost
SCORING:
0 = unacceptable safety risk to persons and property
5 = negligible risk of harm to persons and property
0 = unacceptable environmental risk
5 = negligible environmental risk
1 = more than 200% of the lowest expected cost (LEC)
2 = more than 175% of the LEC
3 = more than 150% of the LEC
4 = more than 125% of the LEC
5 = expected lowest cost
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Safety to Persons and Property
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Activity Description Medium Backhoe Dredge BHD Trailer Dredge (TSHD)
Mobilisation
• transport to site
• set up
Operations
• Loading dredge/barges
• Transportation to sea / return
• dumping at sea
• surveys and monitoring
Port Operations
• Fishing Fleet
• Tugs
• Recreational
• Authorities
Existing wharves
similar
similar
Less safe, barges need to be loaded even
Less safe as slower, weather dependent
similar
more surveys due to longer duration
longer period more potential conflicts
similar
similar
similar
Inherently more stable ocean-going vessel
Can handle adverse weather and seas
Similar
Slightly better safety
Improved safety to port vessels
similar
Safety to Environment
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Activity Description Medium Backhoe Dredge BHD Trailer Dredge (TSHD)
Water Quality
• turbidity
• remobilisation of contaminants
• fuel and oil spills
• other waste
Aquaculture
• water quality impacts
• impact on spat
Habitat and flora
• smothering of seagrasses
• smothering of macroalgae
• smothering of sub-tidal reef
Fauna
• smothering sessile filter feeders (eg mussels,
oysters, sponges, ascidians, corals)
• impacts of plant on mobile fauna (eg fish,
marine mammals, turtles, seabirds)
• -noise and vibration
• -vessels collision
• -lighting
• -entanglement in lines
• -cable strike
Best available, lowest risk
Lower risk
Similar
Similar
Best
Best
minimal risk
minimal risk
minimal risk
Best
Less control
inferior
Less control
Inferior
Inferior
inferior
inferior to BHD in fine materials
Higher risk
Similar
Similar
Inferior
Inferior
Higher risk
Higher risk
Higher risk
Inferior
Slightly better
Better
Better
Better
Better
better
MCA Outcomes
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Conclusions
Advisian / 14
Decision to be made according to consensus or otherwise by Lands if no clear outcome is apparent.
A clear consensus was formed
Dredge Strategy to consider the 3 possible options and this information to feed into the EIS studies.
DISCLAIMER
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