eden breakwater wharf extension project

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

Page iii

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


Page 1

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.

http://www.epa.nsw.gov.au/pesticides/ccos.htm


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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


Page 14

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:




propelled;


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:




propelled;


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.


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APPENDIX A - DRAWING 301020-07698-MA-DWG-3002 REV A


Page 20

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

Advisian / 3

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

Advisian / 4

Dredging Particulars

Advisian / 5

• 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

Advisian / 6

Project Location/ Offshore Disposal Area

Advisian / 7

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

Advisian / 8

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



5 = expected lowest cost

Advisian / 9

Safety to Persons and Property

Advisian / 10

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

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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.

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The presentation contains the professional and personal opinions of the presenter, which are given in good faith. As such, opinions presented herein may not always necessarily reflect the position of Advisian as a whole, its officers or executive.

Any forward-looking statements included in this presentation will involve subjective judgment and analysis and are subject to uncertainties, risks and contingencies—many of which are outside the control of, and may be unknown to, Advisian.

Advisian and all associated entities and representatives make no representation or warranty as to the accuracy, reliability or completeness of information in this document and do not take responsibility for updating any information or correcting any error or omission that may become apparent after this document has been issued.

To the extent permitted by law, Advisian and its officers, employees, related bodies and agents disclaim all liability—direct, indirect or consequential (and whether or not arising out of the negligence, default or lack of care of Advisian and/or any of its agents)—for any loss or damage suffered by a recipient or other persons arising out of, or in connection with, any use or reliance on this presentation or information.

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eden breakwater wharf extension project

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