appendix 1 clause no. 1 full report...this report has been jointly prepared by pat flanagan...

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5 July 2018Acad No. 3527-SK21C

3527-SK21C

NORTHERN SANDS DMPA

CAIRNS SHIPPING DEVELOPMENT

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GENERAL ARRANGEMENT

DEVELOPMENT CONSULTANTS PROJECT MANAGERS ENGINEERS PLANNERS

(07) 4031 3199CAIRNS

(07) 4944 1200MACKAY

(08) 8943 0620DARWIN

(07) 4724 5737TOWNSVILLE

www.flanaganconsulting.com.au

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SECTION B

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1 November 2018Acad No. 3527-SK15E

3527-SK15E

NORTHERN SANDS


(07) 4031 3199CAIRNS

(07) 4944 1200MACKAY

(08) 8943 0620DARWIN



Dredge Material Placement

End of Week 1Cross Sections

1:1000H / 1:200V

LEGEND

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SECTION C

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3527-SK15E

NORTHERN SANDS


(07) 4031 3199CAIRNS

(07) 4944 1200MACKAY

(08) 8943 0620DARWIN





1:1000H / 1:200V

LEGEND

SECTION A

SECTION B

SECTION C

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3527-SK15E

NORTHERN SANDS


(07) 4031 3199CAIRNS

(07) 4944 1200MACKAY

(08) 8943 0620DARWIN




At 6 Months from StartCross Sections

1:1000H / 1:200V

LEGEND

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SECTION B

SECTION C

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3527-SK15E

NORTHERN SANDS


(07) 4031 3199CAIRNS

(07) 4944 1200MACKAY

(08) 8943 0620DARWIN




Bunds RemovedCross Sections

1:1000H / 1:200V

LEGEND

SECTION A

SECTION B

SECTION C

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3527-SK15E

NORTHERN SANDS


(07) 4031 3199CAIRNS

(07) 4944 1200MACKAY

(08) 8943 0620DARWIN





1:1000H / 1:200V

LEGEND

SECTION A

SECTION B

SECTION C

A1 Full Size


3527-SK15E

NORTHERN SANDS


(07) 4031 3199CAIRNS

(07) 4944 1200MACKAY

(08) 8943 0620DARWIN




At Time of Ultimate SettlementCross Sections

1:1000H / 1:200V

LEGEND

CAIRNS SHIPPING DEVELOPMENT PROJECT

Northern Sands DMPA

Site Water and Materials Balance Assessment

(i)

TABLE OF CONTENTS

2.1 Volume Assessment .......................................................................................................................................... 3 2.2 Production estimates ......................................................................................................................................... 4

9.1 In-situ Material Volume ................................................................................................................................... 20 9.2 Additional water volumes ................................................................................................................................ 24 9.3 Material properties and settling characteristics ........................................................................................... 24 9.4 Material Dry Density ........................................................................................................................................ 25 9.5 Contingency Volume Summary ..................................................................................................................... 28 9.6 Contingency Measures Summary ................................................................................................................. 29

Cairns Shipping Development Project Revision: Final NorthernSands DMPA Date: November 2018 Document: R-PF4265 - SWMBA - Final Page 2 of 31

1.0 OBJECTIVES

The placement of the soft clays at the Northern Sands DMPA requires the soft clays materials dredged from the Trinity Inlet Shipping Channel to be transported to a pump-out facility located approximately 3 km off shore from the mouth of Richter’s Creek and pumped via approximately 8 km of submerged, floating and terrestrial pipeline to the Northern Sands DMPA. The dredging and placement of material in the DMPA is required to be conducted in the period May to September (inclusive). It is anticipated that the dredging programme will be completed within 12 weeks. To allow for the maximum consolidation period prior to the onset of the 2020 wet season, it is intended to commence dredging in early May 2019, with targeted completion by end of July 2019.

To allow for the construction of the delivery pipeline, placement and water management facilities and discharge pipeline in the period February to April 2019, it is intended to construct the temporary bunds in the period November 2018 to January 2019.

This Site Water and Materials Balanace Assessment report has been prepared to demonstrate that the proposed Northern Sands Dredge Material Placement Area has the capacity to accept and manage the “bulked up” soft clay material resulting from dredging of the Cairns Shipping Channel.

The operation and management of the DMPA is required to:

Have capacity to receive the volume of dreged soft clays

Meet the prescribed Water Quality limits for discharge of tailwater to the Barron River.

Operate at a min 600mm freeboard between top operating level and the bund crest levels.

Avoid the potential for overtopping due to accumulated rainfall during operations

Minimise the risk of remobilisation of placed dredged materialsdue to a Baron River Flood event

The water and materials assessment has been based on a conservative allowances for:

the volume of material to be dredged,

production and dredging duration estimates provided by an experienced dredging consultant and

placement simulations to determine placed densities and consolidation over time.

The report also includes a sensitivity analysis of likely changes to volumes, operating durations and placed density.

This report has been jointly prepared by Pat Flanagan Principal of Flanagan Consulting Group a Registered Professional Engineer (RPEQ No 2170) with 39 years of practice as a civil engineer providing engineering advice and services, and Alan Vico General Manager Planning and Infrastructure a professional engineer with 24 years experience involved in maintenance and capital dredging, reclamation and Port development activities

.


2.0 SOFT CLAY VOLUMES AND PRODUCTION RATES

2.1 Volume Assessment During the preparation of the revised Draft EIS (refer Chapter A2 Project Background) the volume of material; to be dredged was established using a 3-dimensional (3D) surface model of seabed levels obtained from Hydrographic Survey of the existing channel and proposed widening areas undertaken following the 2016 annual maintainance dredging campaign.

The total volume of capital dredge material was calculated as the volume between the approved maintenance dredging levels and the proposed capital design dredge levels.

The Calculated volumes of dredge materials for the proposed channel profile were as follows:

total volume of capital dredge material – 791,064 m3

volume of ‘soft’ clays in capital dredge volume – 698,755 m3

volume of ‘stiff’ clays in capital dredge volume – 92,309 m3

In addition to the measured volume the Revised Draft EIS included contingency volume allowances taking the total dredge volume to 1,000,000m3 consisting of 900,000 m3 of soft clays and 100,000 m3 of stiff clays to allow for survey accuracy and dredging tolerance. The soft clay contingency also included for potential additional siltation that might occur, in the channel widening and extension areas as well as existing channel areas not subject to annual maintenance dredging, between the time of the survey and the anticipated mid-2019 dredge date. A worst case contingency estimate was made for dredging volumes for the DMPA concept design and impact assessment purposes.

A review of the channel batter slope design, dredge volumes and contingency was carried out between August and October 2018. This utilised further Hydrographic Surveys conducted by Ports North following the 2017 and 2018 annual maintenance dredging, a study of erosion profiles in the area of the outer channel widening and afull Port and channel multibeam survey by Port Of Brisbane in September 2018. Further geotechnical slope stability assessment was also undertaken by Golder Associates, based on a review of existing channel batter slopes and the geotechnical investigations completed for the revised Draft EIS since the original batter slopes were adopted.

The resulting channel batter slope design changes are as follows;

Batters to be cut from the channel toe lines at the new design depth of RL -8.8m LAT rather than fromthe deeper insurance depths as originally proposed.Channel Batter slope adjustments from 1:4 to 1:2 in stiff clay Channel Batter slope adjustments from 1:4 to 1:2 for soft clay less than 4-6m high and to 1:3 for soft clay more than 4-6m high

The above design refinements result in a significant dredge volume reduction. For the purposes of a most likely pre-capital dredging surface level the post 2017 maintenance dredging survey profile has been adopted and the volume from this surface to the refined design lines remeasured by both Golder Associates and Ports North’s Registered Hydrographic Surveyor, using 3D volume models. Golders measured volumes are as follows;

total volume of capital dredge material – 539,864 m3

volume of ‘soft’ clays in capital dredge volume – 466,138 m3

Volume of ‘soft’ clay above the approved maintenance dredging levels in the existing channel – 118,321m3

volume of ‘stiff’ clays in capital dredge volume – 73,726 m3

volume of ‘stiff’ clays the above the approved maintenance dredging levels in the existing channel –3,672 m3

Total Volume between 2017 survey surface and the revised channel design – 661,858 m3


The project will need to accommodate the measured volume of 3,672 m3 of stiff clay within the approved maintenance dredging zone as it will need to be dredged by the Backhoe Dredge deployed for the project. Whilst further maintenance dredging of soft clay was undertaken in the period of August and November 2018 and is programmed to occur again in April 2019 some contingency volume is still required for soft clay for variations in the surface profile from the assumed post 2017 maintenance dredging surface as well as sediment that will continue to fall into the channel during the 3 month capital dredging. A contingency volume was adopted based on results of post–dredge surveys from 2015-2018 and the last 20 years of historical yearly siltation data.

For the purposes of re-assessment of the Northern Sands DMPA capacity and performance the assumed volume of soft clay to be accommodated was 700,000 to 740,000 in-situ m3. It is noted that this volume aligns well with what was the measured volume as described above and also aligns well with the basis of the ’best likely case’ Revised Draft EIS assessments.

2.2 Production estimates Akuna Dredging has prepared a production estimate for the dredging of the soft clays. The production estimate was included as Appendix Z of the revised draft EIS and is included as Appendix A for ease of reference. TheAkuna production estimate considered the optimal equipment spread using a 5,600m3 Trailer Suction Head Dredge (TSHD) “Marieke” and a 44,475 kW floating booster station DI 509.

Akuna considered the production rates for an insitu soft clay volumes of 710,000m3 and 900,000m3.

The Akuna production rates have been based on 24/7 dredging operation with 80% utilisation rates based on allowances for down time for bunkering, technical, weather and shipping and other delays. The production rate is based on 135 operational hours/week. This results in a total duration of dredging of 10 weeks for the 710,000m3 scenario and 12 weeks for the 900,000m3 scenario.

Akuna has allowed for a small proportion (approx. 2%) of the insitu soft clays to remain in the channel through bed levelling activities.

The dredging contract will include a requirement for the dredging to be completed in a 12 week period notwithstanding that the targeted in-situ volume to be dredged (740,000m3) is less than the 900,000m3 able to be dredged in that period. This will allow for higher production rates to be achieved early in the dredging campaign and for a slower production rate towards the end of the campaign to ensure achievement of tailwater Water Quality standards when the relative proportion of water volumes within the DMPA is reduced.

The total pumping mixture is based on the addition of water to the in-situ dreged material volume to facilitate pumping of the material through the 8km delivery pipeline. This results in the in-situ dredged material being “bulked up” by a factor of 2.66. Based on the adopted average in-situ density of 960kg/m3 the density of the slurry material delivered to the DMPA is 360kg.m3. Delivery of the planned in-situ volume to be dredged to the DMPA will require 284 loads over the 12 week period. Based on achieving production rates of 4 loads per day over the first 9 weeks of the campaign the production rate can slow to an average of 1.5 loads per day over the last 3 week period. Prior to the delivery of each load the delivery pipline is required to be “primed” by filling with seawater (Akuna estimate is 5,253m3/load). Following placement the delivery pipeline is required to be “flushed” (Akuna estimate is 4,202m3/load).


Akuna’s production estimates indicate the following pumped volumes will be required to deliver the dredged soft clays to the DMPA:

Filling pipeline 1,489,225 m3

Pumping mixture 1,968,400 m3

Clearing Pipeline 1,191,267m3

Total Water and Mixture 4,648,893m3

These production volumes and rates were adopted for the water and materials balance modelling and for dredge material placement simulation used to predict consolidation of the placed dredge material over time.


3.0 NORTHERN SANDS DMPA The Northern Sands DMPA is an existing pit which is a consequence of historic sand extraction activities on the Barron Delta. Sand extraction in the proposed DMPA will be completed prior to the hand over of the DMPA site to Ports North for the purposes of placement of the dreged material. Sand extraction and other approved activities associated with the Northern Sands operation will continue on site external to the DMPA area.

At the anticipated time for earliest commencement of placement (May 2019), the volume of the void below nominal ground level (RL 3.5m AHD) is estimated to be approximately 2,230,000m3. with a surface area of approximately 40 Ha.

The estimated volume of the “bulked up” dredge material is approximately 1,970,000m3. A minimum 1 m depth of water above the placed material level to facilitate placement is required at completion of placement. This relates to a required volume of approximately 400,000m3 (20% of placed material volume. The DMPA is required to have a minimum freeboard of 600mm from top operating level to the top of the containment. This equates to a volume of approximately 240,000m3.

Therefore the total capacity (including freeboard) required to accommodate the placed material is approximately 2,610,000m3.

The existing void capacity will be enhanced via the construction of temporary bund walls, with a crest level of RL 4.5m AHD which will provide a total volume of 2,630,000m3. The bunded void will provide sufficient capacity to accept the “bulked up material” and the volume of retained water required to meet WQ limits prescribed for discharge of displaced fresh water from the void, transport water and supernatant generated by the consolidation of the placed material as well as a min 600mm freeboard.

After the preparation of the Revised Draft EIS and supplementary Report detailed survey and geotechnical investigation have been undertaken to advance the design of the DMPA bunds. The bund alignment has been based on required setbacks of the toe of the bund from the edge of the void to ensure stability of the bund.

The ground levels surrounding the void vary as a result of historic extraction and waste management activities on the site. Mounds (up to RL 9.0) adjacent to the Barron River currently exceed the approved land form for the site (Mounds to RL 5.0 are permitted along the souther Boundary of Lot 5). As part of the development of the DMPA these mounds will be reduced to the approved height of RL 5.0. Bunds are only required where the surface level is lower than RL 4.5. As the land levels vary around the perimeter of the void, based on a notional surface level of RL 3.5, the bunds where required will have a nominal height of 1.0m..

The general arrangement for the proposed bunds is shown in Figure 1


Figure 1 – Northern Sands DMPA General Arrangement

(Sketch 3527 – Sk 21D full size copy in Appendix B)

Detailed engineering plans consistent with the General arrangement for the construction fo the DMPA voids will be submitted with an Opertaional Works Application to Cairns Regional Council.)


4.0 WATER AND MATERIAL BALANCE MODEL A daily input / output Water & Materials model has been prepared based on the estimated in-situ dredge material volumes, the production estimates prepared by Akuna and the proposed operating regime. The modelling is very conservative as it does not take into account any material settlement during the 12 week dreging campaign.

The 740,000m3 of in-situ dredge material equates to approx. 2,000,000m3 of slurry transported to the void. The delivery rate is based on 4 loads/day for the first 9 weeks (approx. 90% delivered ) and then the balance(10%) placed over the final 3 weeks at an average of 1.5 loads /day.

The placement operating regime provides for the equivalent volume of prime water, slurry material and flush water to be pumped out from day 1 untill the placed material surface approaches to within 1.0m of the lake level. The water level is maintained at 1.0m above placed surface until completion of placement.

The output from the water and material model based on average daily inputs for the 84-day duration of the dredging and placement campaign are attached in Appendix C.

The Weekly summary of the model outputs are shown in Table 1 below:

Time of Placement

Cumulative Volume of Material Imported

Cumulative Volume of

Water Imported

Cumulative Imported Material /

Water

Daily Water

Take off

Level of Material

Level of Water

Depth of

Water Over

Freeboard

to RL 4.5m

Week Day

(m3) (m3) (m3) (AHD m)

(AHD m) (m) (m)

1 7 194410 264740 459150 65593 -3.885 1.000 4.885 3.500 2 14 388820 529480 918300 65593 -2.345 1.000 3.345 3.500 3 21 583230 794220 1377450 65593 -1.480 1.000 2.480 3.500 4 28 777640 1058960 1836600 65593 -0.770 1.000 1.770 3.500 5 35 972049 1323700 2295749 65593 -0.110 1.000 1.110 3.500 6 42 1166459 1588440 2754899 37820 0.520 1.520 1.000 2.980 7 49 1360869 1853180 3214049 37820 1.135 2.135 1.000 2.365 8 56 1555279 2117920 3673199 37820 1.725 2.725 1.000 1.775 9 63 1749689 2382660 4132349 37820 2.270 3.270 1.000 1.230

10 70 1822593 2481938 4304530 14183 2.460 3.460 1.000 1.040 11 77 1895496 2581215 4476711 14183 2.650 3.650 1.000 0.850 12 84 1968400 2680493 4648893 14183 2.835 3.835 1.000 0.665

Table 1 - Weekly Placed volumes and levels


The the general arangement for the DMPA together with the level /volume /area outputs for the DMPA are shown in Figure 2.

Figure 2 – Northern Sands DMPA Placemnt Zone Plan and volumes

(Sketch 3527 – Sk 14G full size copy in Appendix D)

Time series cross sections of the DMPA at end of each week are shown in Sketch 3527-15E sheets 1-12 attached in Appendix E.

The Water and Materials Balance Assessment indicates that the operating water level will start increasing from day 38 and will rise above RL 3.5 (such that the bunds start to function as a containment structure) at about day 72 and will reach a maximum level of RL 3.835m AHD on Day 84. Based on the top of Bund at RL 4.5m AHD the mandated minimum freeboard of 600mm is not compromised during placement.

Following the completion of placement the water level is maintained for a period of 4 weeks to allow access for PASS validation and treatment (if required) of placed material. The pond will be allowed to settle for a period of 1 week and then dewatered completely over the following week. Within 6 weeks of completion of placement the dewatered placed material will be exposed sunlight to encourage drying and hardening of the surface layers.

The bunds will function as a containment structure from day 72 until dewatering (within 6 weeks of end of placement).

This will be a period of approx 54 days (84-72 + 6x7). That is a 8 week period that could occur in the period August to November inclusive (coincident with the driest period of the year).


Based on the requirement to complete the dredging campaign in the period May to September (inclusive) and allowing for a 12 week dredging programme , the earliest and latest timing milestones during the placement are shown in Table 2:

Earliest Start Latest Start Start of Bund Construction Late Nov 2018 1 April 2019 Completion of Bund Construction 22 Dec 2018 Mid MY 2019 Start of dredging 1 May 2019 1 July 2019 End of dredging 31 July 2019 30 Sept 2019 Material achieves RL 0.0 7 June 2019 7 August 2019 Material level week 9 RL 2.270 7 July 2019 7 September 2019 Material level week 12 RL 2.835 31 July 2019 30 September 2019 Water level at RL 1.0 till 7 June 2019 7 August 2019 Water level at week 9 RL 3.270 7 July 2019 7 September 2019 Top Water Level at Week 12 RL 3.825 31 July 2019 30 September 2019

Table 2 – Milestones for Placement Programme


5.0 PLACEMENT SIMULATION As well as the conservative (no allowance for settlement during placement) Input-Output model, BMT JFA undertook simulation modelling of the placement of the soft clay materials using the BMT developed “Dredge Material Containment Assessment Tool” (DMCAT) with the estimated volumes and production rates and the adopted water management strategy as input. The model computes both settlement of the introduced suspended material, via a series of vertical 1-D computational cells coupled to a quasi 1-D steady horizontal flow model, as well as the consolidation of settled material. The settling and consolidation model parameters were calibrated with laboratory testing by settling column tests and slurry consolidometer tests respectively.

An explanation of the placement simulation undertaken is provided in BMT_JFA’s Technical Note TN-1545.00-2 included in Appendix F.

The following key results were obtained from the simulations:

An average placed dry density at the completion of the dredging campaign (short-term) of 320 kg/m3

was obtained with a settled bed level of +3.2m AHD. This figure includes the material trapped in suspension at the completion of the dredging campaign, as the solids rapidly settle out of the suspension to form the bed surface.

An average placed dry density at the start of the wet season (1 December) of 385 kg/m3 was obtained with a settled bed level of +2.2m AHD.

An average placed dry density at 18 months of 585 kg/m3 was obtained, with a settled bed level of +0.4m AHD.

The proposed containment area, with MOWL at RL 3.9 enclosing a storage volume of 2,401,000 m3,has sufficient capacity to contain the dredged material (882,649m3 with an in-situ dry density of 0.96t/m3).

Whilst the model outputs indicate periods of exceedances of water quality thresholds near the end of the program, this can be managed through implementation of management measures. Particular attention is likely to be required over the last week of the campaign.

It is expected that suitable tailwater discharge quality can be achieved with the nominated pond capacity. Measures to further address potential intermittent discharge water quality exceedances include:

Active management of water levels (and hence available capacity) in the pond by drawing down water levels as much as is practical in advance of periods when the discharge water quality is forecast to exceed allowable discharge quality limits.

Short term, temporary water level increases (through raising the boards in the weir box) will increase retention times and assist in settlement of fine material to improve tailwater quality.

Reduction in dredge production rates, either via prolonged cycle times, or temporary standby for the dredge.

Given the limitations of the placement simulation model as identified by BMT- JFA the results of the simulation are considered conservative and appear to understate the placed density at the completion of the dredging campaign. This is considered likely a result of conservatism introduced in the settling column sample preparation and suite. By comparison the predicted density of the dredge mixture at the end of the delivery pipe, based on the selected dredge plant and likely additional pump water, is 360kg/m3 which is greater than the simulation output. For the purpose of predicting the timeline for placement and settlement the levels identified in the daily input/out model (Appendix C ) have been adopted for the placement period and projected based on the BMT-JFA consolidation modelling results for 6 months and 18 months from start of placement.


6.0 ANTICIPATED WATER AND PLACED MATERIAL LEVELS A summary of the water and placed material level over the period of placement, 6 months and 18 months following comencement of placement are shown in Table 3.

Level (AHD) Volume to Level Surface Area at Level Comment

(m) (m3) (m2) 4.5 2,635,906 411,276 Bund Crest level 4.0 2,431,409 406,631

3.835 2,364,449 405,007 Top of water at end of placement 3.5 2,229,313 398,303 3.0 2,031,552 392,284

2.835 1,967,039 389,688 Top of material at end of placement

2.5 1,837,416 384,131

If surface is crusted, material level at which Bunds may be lowered to

RL3.5 or natural gound which ever is higher

2.2 1,722,913 379,361 Top of material 6 months after dreging starts

2.0 1,647,343 340,798

1.5 1,479,610 329,406

If surface is "wet", material level at which Bunds may be lowered to

RL3.5 or natural gound which ever is higher

0.4 1,128,038 310,965 Top of material 18 months after dreging starts

1.0 1,317,288 319,884 Assumed GW level at start of placement

0.5 1,159,211 312,511 0.000 1,004,895 304,705 Lowest Groundwater Level -0.5 855,396 292,826

-0.770 777,275 285,901 Top of PASS at end of placement -0.9 740,332 282,412 Top of material at final settlement

-1.110 681,719 275,560 Level of pass 6 months from start of dredging

-2.065 445,287 213,723 Level of pass 18 months from start of dredging

-2.5 360,014 178,424

-2.920 292,039 145,125 approx level of PASS at final settlement

-3.5 226,995 93,827 -4.0 185,631 72,823

Table 3 – Summary of water and placed material levels over time


As part of the preparation of a Flood Risk Assessment BMT assessed the potential for remobilisation of the placed material in the event of a Barron River Floed event. The remobilisation Risk assessment concluded that : “…a minimum of 2m of water cover during an inundation event is required for minimum loss of sediment from the containment area. This is achieved by incorporating the lowered bund section and allowing the containment area to fill consistent with increasing flood heights until the bund is overtopped during and inundation event (>20%AEP or > 5-year ARI)”

This assessment indicates that the bunds can be lowered to RL 3.5 or natural surface level (whichever is highest) when the placed material has settled to RL 1.5m. It is anticipated that this will occur following the 2019/20 wet season. A time line of anticipated water, placed material and bund crest levels for earliest and latest start time is shown in Figure 3 below:

Figure 3 – Northern Sands DMPA Placement Settlement Timeline

(Sketch 3527 – Sk 38A - full size copy in Appendix G)


7.0 SURFACE WATER MANAGEMENT The DMPA will be exposed to seasonal rainfall over its anticipated 2 year life. Its exposure to and capacity to accommodate seasonal rainfall will varyover its operational life. BMT have undertaken an analysis of rainfall records in the local to establish the potential rainfall exposure with the results presented in BMT Memorandum dated 27 October 2018 attached in Appendix H. The proposed surface water management regime for the DMPA involves the following works

For 1st wet season prior to placement, leave a section of bund along the southern boundary (Ch 3010 – 3100) unconstructed as a preferential outflow (rainfall) /inflow (flooding) path. Post wet season preferential flow path sections to be raised to RL 4.5m. Post dewatering – reduce section of bund along the southern boundary (Ch 3010 – 3100) to RL 3.5 as a preferential outflow (rainfall) /inflow (flooding) path. Allow 2nd wet season water level in Lake to rise via accumulated rainfall to up to RL 3.5 to minimise remobilisation risk in the event of a flood Provide pump out capacity post wet season to dewater the void to encourage dry season surface crusting Post 2nd wet season when material settled to below RL 1.5m remove bunds to Natural surface or RL 3.5m whichever is higher except for approved land form at RL 5.0 along southern boundary of Lot 5. Spread excess bund material as fill adjacent to bunds to allow NS land form to fall towards the lake.

The design for each stage is shown on Skecthes 3527-SK59-62 included in Appendix I. A summary of the stages of operations and the exposure and response to rainfall events is set out in Table 4


Stage Management Responsibility Exposure Design Rainfall

1 Pre-placement Bunds constructed

Ports North Nov 2018 - April 2019 (1st Wet Season)

Bunds to R4.5m . Preferential flows paths by not building the bund (ch 3010 -3100 invert at RL 2.8) along southern boundary of Lot 2 to allow Inflow and out flow

Void is permable to ground water. Air space available to crest level is 3.5 m. Air space has capacity to accomodate the highest cumulative wet season rainfall (3110mm) recorded in the 77 year history of Rainfall records at Cairns Aero Sataion No 31011. The void has the capacity to accommodate the cumulative rainfall in a 1% AEP season. Preferential flow paths will outlet to Barron River when water level reaches RL 2.8. The DMA will spill through the preferential flow path in the event of greater than 1.8m of cummulative rainfall. This depth exceeds the maximum rainfall ever recorded in individual months from Novemer to April. No active intervention required to management rainfall events. It is noted that whilst there is some debate on the accuracy of the actual levels, the quantum of seasonal increase and decrease in water heights provides an indication of how the lake responds to rainfall and time period over which the water flows out of the lake in the dry season. Seasonal lake water level increases over the monitored period (2011 to 2016) appear to be in the order of 0.5m to 1.5m. Overtopping of the bund crest is a very low probability


2 During Placement until dewatering

Dredging Contractor

May 2019 - October 2019 (Dry season)

Bunds to completed to RL 4.5m. Tailwater Weir Boxes in place to allow decanting of tailwater . Weir boards max level @ TOL RL 3.9m

Air space available to crest level reduces from 3.5m to 600mm by end of placement and maintained till dewatering when discharge pipeline is decommissioned . In the anticipated period when the void airspace is at is lowest July to October the void has the capacity to accommodate the highest ever recorded rainfall in each month . Dredging Contrators pump out capacity > 80 ML /day can handle dewatering of rainfall from a 200mm rainfall event in 24 hours . Air space has capacity to accomodate the highest cumulative dry season rainfall (644) recorded in the 77 year history of Rainfall records at Cairns Aero Sataion No 31011. The void has the capacity to accommodate the cumulative rainfall in a 1% AEP dry season taking into account evaporation losses at 5mm /day. Overtopping of the bund crest is a very low probability

3 Post Placement

Ports North November 2019 - October 2020 (2nd Wet Season & 2020 Dry season)

Provide preferential inflow/outflow paths to BR by cutting bund down to RL 3.5m along southern boundary of Lot 2 (ch 3010 -3100 )

Air space increases to >1.6m following dewatering. The capacity of the air space will progressively increase as the material settles. Th air space has the capacity to accommodate in excess of the 1% AEP event for each month from November to April. Preferential flow paths to BR are provided by cutting bund down to RL 3.5m along southern boundary of Lot 2 (ch 3010 -3100 ). Provide pump capacity post wet season to progressivly reduce water level in void to expose placed material surface to encourage crusting. Allow wet season rainfall to accumulate to RL 3.5m to minimise. “…a minimum of 2m of water cover during an inundation event is required for minimum loss of sediment from the containment area. This is achieved by incorporating the lowered bund section and allowing the containment area to fill consistent with increasing flood heights until the bund is overtopped during and inundation event (>20%AEP or > 5-year ARI)

During the wet season, rainfall will be allowed to accumulate to RL 3.5m AHD to reduce differential levels between flood stage height and void lake level. A


Barron River flood will inundate the void when the flood stage height reaches >RL 3.5m (50% AEP) through preferential flow paths for drainage.

If Flood occurs early in the wet season when lake levels are low, Inflow locations will be designed to be baffled/dissipated to prevent jetting and disturbance of placed material. Pump capacity post wet season will be used to progressively reduce the water level in void to expose placed material surface to encourage crusting, reducing the ability for resuspension. Provide pumping capacity post wet season to progressively achieve a dewatered surface until placed material settles below dry season groundwater level.

4 Final land form

Northern Sands

November 2020 - April 2021 ( 2nd wet season post placement ) and onwards for subsequent dry and wet seasons.

Bunds removed to natural surface or RL 3.5m or approved land form level RL 5.0 ( southern boundary of Lot 5)whichever is the highest.Preferential drainage paths to Barron River to be provided along southern boundary of Lot 2 (ch 3010 -3100 invert at RL 2.8)

Lake Level will rise with accumulated rainfall and drain to Barron River through preferential flow paths along southern boundary of Lot 2 (ch 3010 -3100 invert at RL 2.8). Lake level will eventually fall through evaporation to groundwater level

Table 4 – DMPA Operating Regime


8.0 CONSEQUENCE CATEGORY ASSESSMENT

The DMPA is an existing void produced as a consequence of historic sand extraction activities on the Barron Delta. The existing void does not have sufficient capacity to accommodate the “bulked up” dredge material and the required water volumes to facilitate placement and achievement of the prescribed tailwater water quality requirements.

The existing void capacity will be enhanced via the construction of temporary bund walls, with a crest level of RL 4.5m AHD which will provide a total volume of 2,630,000m3 to provide sufficient capacity to accept the “bulked up material”, the volume of retained water, transport water and supernatant generated by the consolidation of the placed material as well as a min 600mm freeboard at top operating level.

The Water and Materials input / output model identifies that the placed material reaches a top level of RL 2.835m which is below notional surrounding ground levels which are generally at RL 3.5m. When the water level in the DMPA rises above notional ground level at about day 70 it starts to function as a containment structure. When water level reaches the top operating level ( RL 3.835) the bunds are retaining a depth of approximately 335mm of water with an approximate volume of 154 ML.

The water levels are maintained at 1m above placed material level for a period of 6 weeks until it is dewatered. Consequently the DMPA functions as a containment structure for a period of approximately 8 weeks.

The DMPA acts as a containment structure at and immediately following the completion of placement of the dredge material (Stage 2) and has the potential to act as a containment structure during the wet season following completion placement (stage 3) due to the potential containment of accumulated wet season rainfall.

Notwithstanding the short duration of this function, the State Governments Manual for Assessing Consequence Categories and Hydraulic Performance of Structures (March 2016) sets out the requirements for assessing hazard consequence and hydraulic performance for “regulated structures” constructed as part of an Environmentally Relevant Activities. Section 2.1.1 of the manual sets out exemptions for structures that are excluded from the requirements of the manual.

The proposed Bunded DMPA can be designed, constructed and managed to:

• Contain fluids for no longer than 24 months,

• Minimise “site specific” risks of seepage,

• Minimise Passage of the wetting front, and

• Prevent and then minimise the potential for fluids overtopping.

However, as it will be required to contain up to 150ML above notional ground level (RL3.5m AHD) at a top operating level of 3.835m AHD, and potential 390ML if permitted to fill to bund crest level, it cannot meet the exemptions set out in section 2.1.1 of the Manual which limit the storage volume to 5ML.


Therefore, the bunded early containment structure works could be considered a regulated structure and a Consequence Category Assessment (CCA) is required for the following failure event scenarios:

• Failure to contain – seepage

• Failure to Contain – Overtopping

• Dam BreakGiven the volume of water contained is greater that the volumens for which

A Consequence Category Assessment(CCA) in accordance with the Guidleines prepared by Neil Collins of BMT(ref: R.B23336.003.00 November 2018 is attached as Appendix J.

The BMT CCA arrives at the following conclusion:

The analysis indicates that proposed DMPA works in conjunction with specific seasonal operation and bund design incorporating methods for managing void water levels results in a low risk for all specific CCA catagories.

The assessment of the risks each of the repscribed failure events against the three criteria of harm to Humans, The environment and property for both stages 2 & 3 are summarised in Table 5.

Failure Event Scenarios

Human Health General Environmental Harm

General Economic Loss or property Damage

Dam Break LOW LOW LOWOvertopping LOW LOW LOWSeepage LOW LOW LOW

Table 5 – Consequence Category Assessments


9.0 SENSITIVITY AND CONTINGENCY

The key dependant parameters and processes in the assessment of the capacity and performance of the Northern Sands DMPA (and inputs to the BMT-JFA Placement Simulation) are:

In-situ volume of material to be dredged and placed at Northern Sands; Prime, pump and flush water added to deliver the material to the NS DMPA; Material Properties (fine/coarse content) and settling characteristics; Material dry density – In-situ, placed and settled, consolidated post placement.

The basis of the adopted values and sensitivity and inherent contingency factors for each of the parameters are described in the following sections along with and available management contingency measures.

9.1 In-situ Material Volume 9.1.1 Sedimentation Process Assessment

The material volume has been derived by 3D Model computation of the 2017 post – maintenance dredging Hydrographic Survey. The survey covers the existing channel and batters as well as the area of proposed widening. As such the required dredge material volume to be accommodated in the NSDMPA will vary dependent of the amount of ongoing siltation accretion and/or erosion in these areas as well as the effectiveness of subsequent maintenance dredging campaigns prior to the commencement of the CSDP capital dredging.

A recent review of literature, mapping and survey work has indicated the western side of the channel, proposed for the widening, is subject to ongoing long-term erosion, particularly on the bend and transit area where the major portion of the widening dredge volume is required. The Aus-Chart map overlay shown in Figure 4 depicts the natural movement of sediment in Trinity Inlet near the channel. For a distance of around 1800m, the 5m contour moved 150m between 1983 and 2001. This equates to a rough volume of 500,000m3 of natural seabed having been eroded away.

Figure 4 - Aus-Chart map overlay


Figure 5 shows cross sections of this erosion profile form a 2001 survey of the area.

Figure 6 2001 survey cross sections

Figure 6 shows cross sections of this erosion profile form a 2018 survey of the area.

Figure 6 2018 survey cross sections


Whilst a full channel length erosion and accretion study has not been carried out this process was concluded in the outcomes of the 5 year JCU - ARC Grant Project, “The Environmental Sedimentology of Trinity Bay, Far North Queensland, (Carter et al, 2002), which outlined the sediment movement processes and sediment fraction rates including the resulting erosion adjacent to the Shipping channel and deposition adjacent the Esplanade.

9.1.2 Seabed profile post – maintenance dredging

The recent trend in channel maintenance dredging program outcomes within the footprint of the existing channel is illustrated in Table 6 below.

Table 6t Dredge survey results

The improvement from 2015 reflects a variation to the annual permit limit processed in 2015 and intent to clear the approved maintenance dredging volumes prior to the capital dredging. It is noted that following the August 2018 dredging the dredge returned from refit in late October for four days of maintenance dredging of the eastern batter removing a further 20,000cu.m approximately. The post 2017 survey condition has therefore been chosen as a safe likely condition at the time of commencement of the project. Ports North has also requested scheduling of the TSHD Brisbane for next channel maintenance dredging in April – May 2019 immediately prior to the capital dredging to ensure this is at least the case.

Post-dredge Survey

Quantity of material above maintenance

target depth 2015 195,493 m3 2016 62,585 m3 2017 45,430 m3

August 2018 46,293 m3


9.1.3 Survey Accuracy

The hydrographic surveys conducted by Ports Norths Registered Surveyor utilise single beam sounder equipment and data processing software that tend to bounce off the high points and spatially interpolates between survey run lines. By comparison multi-beam survey equipment has greater surface profiling capability including seeing into the seabed trenches. A post dredge survey commissioned by Ports North in September 2018 using the Port of Brisbane Multi beam survey equipment yielded a dredge volume of approximately 30,000 cubic metres less.

9.1.4 Overflow Dredging

The volume calculation also makes no deduction for the overflow dredging quantity predicted and modelled in the EIS. In order to effectively and efficiently dredge the required volume and profile some dredging in overflow mode is necessary. This will result in loss of fine sediment in passive plumes which will escape the dredge area. This was assessed in the Revised Draft EIS for best likely and worse likely cases. The best likely case was based on 10 minutes overflow dredging per load for the 710,000 soft clay volume dredged by TSHD for delivery to Northern Sands.

The Hydrodynamic Modelling Report included as Appendix AG in the Revised Draft EIS provides the following (refer sections 6.2.3-6.3)

Overflow fines spill – 80% Overflow fine spill dynamic plume to channel seabed – 85% (Passive Plume dispersed is therefore 12%) Passive Plume Source Rate - 144.3 kg/s

For the purposes of conservative volume sensitivity for the NS DMPA the following calculations are applicable;

10 minutes per load gives – 86.5 tonnes/load 284 loads modelled for 740,000 TSHD dredge volume gives – 24,500 tonnes Assuming 960kg/cubic metre in-situ gives – 25,500 in-situ cubic metre losses.

A volume contingency of 25,500 in-situ cubic metres is therefore inherent in the assessment.

In conjunction with the above, the volume assessment presented in section 2.1 indicates sensitivity to increased volume capacity requirements at Northern Sands is extremely unlikely and the dredged material volume required to be accommodated likely to be significantly less than the capacity.

The overall dredge volume contingency measure available to ensure the environmental compliance of the project in terms of Northern Sands Volume capacity remains to simply cease dredging when the capacity is reached. \


9.2 Additional water volumes

The designed dredge sequence and delivery process has been derived by Akuna Dredging Solutions.

Dredge sizes at either end of the feasible size range were examined in terms of the load and pump out characteristics. The adopted dredge for both the Input / Output Water & Materials model and the BMT-JFA simulations has been offered by one of the shortlisted dredging tenderers and other tenderers have offered similar dredge sizes and characteristic confirming these assumptions.

The above will be confirmed with detailed equipment specifications to be provided by the Dredging Contractors in the submission of tenders.

Contingency measures should more water volume be experienced include varying the pump speeds to adjust water intake requirements, additional booster pump/s (the 5 shortlisted tenderers suggest only one or two required), diverting a proportion of the prime water direct to the Barron River.

9.3 Material properties and settling characteristics

The Input / Output Water & Materials model assumes no settling during placement. Similarly the BMT-JFA simulations are based on settling column tests that measure the total time for settling out of the fines from the supernatant water. In reality there will be a volume of coarse material that will settle immediately and hence reduce the volume void consumed.

The sand contents tested in the revised project dredge area are as per Table 7 below and average 10.2% overall. (refer data in Appendix C1 of Appendix E to the Supplementary Report)

Deepening Area Widening Area

Sample Location

% Coarse (>75um)

Sample Location

% Coarse (>75um)

GS1 17 GS3 33 GS2 6 GS8 5 GS9 15 GS13 61

GS11 3 GS22 7 GS12 1 BH2 4 GS14 2 BH3 9 GS15 1 BH5 1 GS16 1 BH7 6 GS17 13.5 BH8 8 GS18 7 GS19 3 GS20 11

Averages 7 15

Table 7 Coarse Fractions


The maximum surface water level allowable in the DMPA with RL 4.5m bund crest levels and 0.6m freeboard is RL 3.9m AHD. By varying the sand content for a range of possible dredge volumes the bulking factors (Volume increase from channel to pipe discharge into DMPA) that can be accommodated in the surveyed DMPA Volume are as per Table 8 below. Another way of presenting the contingency volume associated with this is for a 10% sand content in 740,000 cu.m of dredged material another 60,000 cu.m (8%) could be accommodated at the assumed delivery pipe bulking factor of 2.66.

In-situ Volume of Dredge Material

% sand mass

content

Max Bulking Factor which does not reduce Freeboard

740,000 0% 2.69 740,000 5% 2.78 740,000 10% 2.88 700,000 0% 2.84 700,000 5% 2.94 700,000 10% 3.05 640,000 0% 3.11 640,000 5% 3.22 640,000 10% 3.35 584,000 0% 3.41 584,000 5% 3.54 584,000 10% 3.68

Table 8 Impact of % Sand on Buliking Factor

9.4 Material Dry Density 9.3.1 In-situ Density

The BMT-JFA simulations were based on an average in-situ dry density of material to be dredged and pumped to the NSDMPA of 960 kg/cubic metre.

This included a level of conservatism on the Golder Associates test results summary reported in sections 6.2 and 6.3 of Appendix E to the Revised Draft EIS for ‘’Sediment” and “Mud” as follows;

Sediments (as mainly confined to the existing channel deepening area) - dry densities around 0.7 t/cu.m (range 0.43 to 1.12 t/cu.m)

Mud (as expected to be predominant in the widening areas) - dry densities around 0.9 t/cu.m (range 0.55 to 1.24 t/cum)


The test results from sample locations within the current proposed dredging footprint, which are reasonably well placed along the channel in terms of representing the relative dredge volumes in each segment, are presented in Table 9 below.

Deepening Area Widening Area

Location Average Dry Density Location Average Dry

Density GS1 0.75 GS3 1.10 GS2 0.55 GS8 0.84 GS6 0.80 GS13 1.10 GS7 0.81 GS22 1.04 GS9 0.75 BH2 0.90

GS11 0.59 BH3 0.83 GS12 0.57 BH5 1.01 GS14 0.67 BH7 1.04 GS15 0.74 BH8 1.03 GS16 0.59 GS17 0.70 GS18 0.79 GS19 0.70 GS20 0.74

Averages 0.70 0.99

Table 9 Dry Densities by segment

The above test data for the existing channel (deepening) area is well supported by the last 18 years of detailed data acquired from pre and post dredge surveys and TSHD Brisbane dredge logs demonstrating a high level of consistency as per Table 10 below.

Table 10 TSHD Brisbane Dredge Logs

Year Dredge Wet Load (m3) Dry Load (T) in-situ cu.m removed

apparent in-situ dry density

Comment on outliers and filtered averages

Adjust for assumed 12% of fines (75%) lost

2001 Brisbane 752,270 341,945 357,121 0.96 Trial dredging following dredge launch 2002 Brisbane 927,939 298,484 198,016 1.51 Split program 3 months apart2003 Brisbane 757,900 201,663 408,672 0.49 0.49 0.542004 Brisbane 965,229 248,618 480,815 0.52 0.52 0.572005 Brisbane 655,045 221,417 355,342 0.62 0.62 0.692006 Brisbane 585,754 244,857 347,447 0.70 0.70 0.782007 Brisbane 466,098 156,377 193,708 0.81 0.81 0.892008 Brisbane 438,182 155,347 155,801 1.00 uncharacterist low vol / budget year2009 Brisbane 594,398 150,347 244,910 0.61 0.61 0.682010 Brisbane 708,923 177,505 274,876 0.65 0.65 0.712011 Brisbane 736,631 205,990 397,568 0.52 0.52 0.572012 Brisbane 719,220 220,880 194,981 1.13 split campaign 2 months apart2013 Brisbane 866,894 283,552 366,754 0.77 0.77 0.852014 Brisbane 822,225 336,795 531,953 0.63 0.63 0.702015 Brisbane 946,211 316,910 497,678 0.64 0.64 0.702016 Brisbane 804,726 306,802 416,559 0.74 0.74 0.812017 Brisbane 779,414 258,482 358,095 0.72 0.72 0.80

Total 12,527,059 4,125,971 5,780,296Average 736,886 242,704 340,017 0.77 0.65 0.71

Minimum 438,182 150,347 155,801 0.49 0.49 0.54Maximum 965,229 341,945 531,953 1.51 0.81 0.89

Range


The above adjustments for overflow dredging are consistent with the allowances made in all the EIS studies and reports.

A detailed assessment of dredge volumes with in 250m segments in the existing (deepening area) and widening area indicate these relative volumes are close to 50% each ( 51% to 54% measured in the deepening area for total material and capital material respectively). This suggests a numerical average of the two areas of 0.85 t/cu.m is most likely and the adopted figure of 0.96 t/cu.m has an inbuilt contingency of approximately 13%.

With the re-design of channel batters the proportion of dredge material in the widening has significantly decreased from the 70-80% (mud) assumed by BMT –JFA in their (conservative) selection of a composite “Mud” sample settling column results for calibration of the model.

Measures available to manage this risk include monitoring of dredge pump intake densities (as modern dredges are equipped for) and tracking the level of the drag heads to ensure the lower density surface layers are being dredged as opposed to bulk dredging from the deeper denser underlying layer. Equipment Specifications and methodologies for these monitoring options have been requested in the request for tender document.

9.3.2 Placed, Settled and Consolidated Density

The Input / Output Water & Materials model assumes material delivery at 0.36 t/cu.m and no settling during placement and therefore there are no performance sensitivities in this regard for the placement phase.

The limitations of the BMT- JFA placement simulation model as identified in section 5 above are further detailed in the report in Appendix F. The depth averaged placed density result of the simulation of 0.32 t/cu.m is considered conservative and appears to understate the placed density at the completion of the dredging campaign. This is considered likely a result of conservatism introduced in the settling column sample preparation, laboratory testing and model calibration as described in a review by Golder Associates summarised as follows;

Some test durations were ceased earlier but all results were trending towards the range of around 0.35 t/cu.m to 0.45 t/cu.m Golder undertook similar short term column tests in 1995 of the channel material with settled dry density at 600 hours of 0.42 t/cu.m It is noted that in settling column tests drainage during consolidation can only occur upwards in the column whereas during consolidation in the DMPA drainage can occur horizontally as well. Therefore drainage and consolidation in the DMPA is expected to be much faster than in the test columns Consolidation in the DMPA is also expected to be faster due to the weight of material placed above the lower depths in the DMPA (much deeper than model cell average depths) As sample preparation for the column tests were advised as including high energy power drill mixing it is possible this may have been to the point where particle shear occurred, dispersing flocs of clay and silt into individual particles. Dredging and pumping is not expected to impart sufficient energy and agitation to break the flocs. Indications are that dredged materials as pumped into the TSHD hopper exhibit rapid dewatering pointing to a flocculated material state being retained.

By comparison the predicted density of the dredge mixture at the end of the delivery pipe, based on the selected dredge plant and likely additional pump water, as per the Input / Output Water & Materials model is 360kg/m3 which is greater than the BMT- JFA placement simulation model output but appears reasonably conservative in light of Golder Associates review comments above.


Management measures include monitoring and equipment selection and control as per the measures outlined in sections 9.2 and 9.4 above and also minimising disturbance of placed material via multiple placement locations, horizontal diffusers, and placement as close as possible to the placed material surface.

9.5 Contingency Volume Summary

A summary of the contingency volumes inherent in the adopted target volume, at the completion of dredge material placement, is presented in Table 11 below. The items are listed in order of occurrence and percentages ascertained above successively applied to the remaining volume only (that is - not compounded)

Item / Volume % in-situ cu.m

Total Maximum DMPA Placement Requirement 740,000

Contingency amounts based on most likely case Excess above measured total material volume above design of 661,858 cu.m at post-dredge 2017 survey 11%

78,142

Single beam versus Multi-beam survey allowance 5%

30,000

Overflow dredging loss (N/A to sand content below) 3%

21,773

Sand Content of 10% by mass 8%

51,232

In situ dry density assumptions (13% on 90% fine material) 12%

65,386

Total contingency amount 33%

246,533

Table 11 Contingency Volumes

The above still does not include any volume improvement due to erosion 2019 maintenance dredging result nor settling of fine material occurring during placement.


9.6 Contingency Measures Summary

There are a number of fundamental contingency measures for addressing the volume capacity risk at the NS DMPA in addition to those described above. A summary of all significant contingency measures is in Table 12 below.

Table 12 Summary of Contingency Measures

Item / Description Timing Documented in

Minimise remaining maintenace dredge volume with early 2019 campaign

April /May 2019POB Qld Ports

Preliminary 2019 Program

Multibeam surveys in dredge areasPre, during and post

dredgingTender Doc - Survey

Spec.

Monitor Overflow dredging durationsdaily summary of all

loadsTender Doc - Reporting

Spec.

Minimise added water volume through pump and booster selection and diversion of prime water if practical

Tender review and award

Tender Doc - Methodology and

Equipment Schedules

Monitor dredge intake density and drag head level During dredging Tender Doc - Reporting

Spec.

Even placement and minimise disturbance of placed material via multiple and flexible delivery points

During dredging & placement


Equipment Schedules

Optimise water quality draw off levels by use of weir boxes each end of void and with adaptable draw off levels


Tender Doc - Drawings, Methodology and

Equipment Schedules

Monitor DMPA fill surface level at fortnightly intervals with dual frequancy single beam sounding to detect upper suspended material and settled material levels


Tender Doc - Survey and reporting Specs.

Timing controls to assist in settlement including additional weeks added for reduced production rates, VSD pumps, directing dredge load origin, minor standown, daily standown, weekly standdown


Tender Doc - Pricing & Equipment schedules

Minimise over-dredging by strict tolerances, payment and rectification contract conditions


Tender Doc - Payment and Tolerance clauses

Dredge volume management by settling minimum target depths to be achieved follwed by an additional insurance volume equivalent to the approved target depths if still available


Tender Doc - Payment and Tolerance clauses

Maximise use of bed - levelling equipment where efficent and effective



Equipment Schedules

Cease Placement if NS DMPA capacity consumed End of placement Approval conditions


10.0 CONCLUSIONS The site water and materials balance assessment concludes that the operation and management of the DMPA will:

Have capacity to receive the volume of dreged soft clays

Meet the prescribed Water Quality limits for discharge of tailwater to the Barron River.

Operate at a min 600mm freeboard between top operating level and the bund crest levels.

Avoid the potential for overtopping due to accumulated rainfall during operations

Minimise the risk of remobilisation of placed dredged materials due to a Barron River Flood event

Cairns Shipping Development Project Queensland

Camp Mountain, April 2017

The Cairns Shipping Development Project is a capital dredging programme undertaken by Ports North, which has undergone various phases of scope definition and EIS stages.

On Thursday 23th March 2017, Ports North requested Akuna Dredging Solutions, after previous advice on the spill rates for the plume modelling in May 2014 and the preliminary assessment of the proposed plant and methodologies for the dredging of the “soft” and “stiff” Clays in February 2017, to produce a production and budget cost estimate for the TSHD scope of work.

The information sets received on 13th, 25th and 27th January 2017, mainly containing geotechnical reports and various drawing and sketches of the dredge and land basedmaterial disposal areas and the additional information on lines and levels received on7th April 2017, formed the basis of the production and cost estimate as described in this report. The received data set has been detailed in the section ‘Documents received’ of this report.

The soil characteristics for dredging have been based on the Golder Associatesassessments of the various Geotechnical Investigations as well as the Geophysical Investigation of which no copy has been received. The data provided and summarised by Golder in their ‘Assessment of Material proposed for Dredging’ of 16th January 2017, has been used as the basis for this report.

The production and budget cost estimate, as detailed in this document, have been based on the most optimal equipment spread, being the 5,600 m3 TSHD Marieke and the 4,475 kW floating booster station DI 509.

The specifications of the dredging spread utilized during the actual project execution will depend on factors like the dredging market, equipment availability, the project assessment of the contractors invited to submit a proposal and the tender evaluation of the Client.

Ports North, who are presently working on the Environmental Impact Study for the channel development project, are now in the process of writing the dredging methodology, duration and inputs for modeling to be undertaken for the impact assessment. The project has been re-designed and downsized to make the option for land disposal feasible. The downsized plan is to dredge less than 1,000,000 m3 in total, of which about 100,000 m3 might be “stiff” Clay.

Ports North is close to settling on a site north of Cairns in the Barron River Delta to accommodate the “soft” material and a site up the Trinity Inlet to accommodate the “stiff” Clays.

The timing for the dredging is now likely start in the 2019 dry season. Note is made of the Consultant team’s “stiff” and “soft” classification based on simply whether the clay is the yellow (alluvial) clays or the grey/black marine sedimentary deposits. This is based on seismic interpretations and is not based on the strength tests taken which, in many cases, show only soft-firm at the top of the “stiff” layers.

The production and budget cost estimate requested from Akuna Dredging Solutions Pty Ltd only covers the dredging operations with the TSHD for the removal of the “soft” Clay layers and disposal of the material via pumping ashore to the Northern Sands Quarry pond.

The total gross quantities has been based on two options:Option 1: total dredged quantity of 800,000 m3, of which 710,000 m3 “soft” material with the TSHD and 90,000 m3 “stiff” material with the BHD.Option 2: total dredged quantity of 1,000,000 m3, of which 900,000 m3 “soft” material with the TSHD and 100,000 m3 “stiff” material with the BHD.

The details on the scope of work and activities are to be included in the estimate.

The production and budget cost estimate is to be relatively high level without any cost minimization and will be part of the overall project budget at this stage for the purpose of economic justification and funding applications.The cost estimate will not incorporate project contingencies.

The deliverables were to be presented in a report. The report was requested at the shortest delivery timing possible and preferably not later than 18th April 2017.

Ports North has made the following reports, drawings, sketches and information available initially for the preliminary review of the methodologies and later for the production and budget cost estimate.The following data set was used for the calculations as highlighted in this report:

Document Title

13th January 2017

1546223-008-R-Rev0 Dredge Materials – Cairns Shipping Development Project Issued by Golder Associates Pty Ltd for Flanagan Consulting Group 16 December 2016

921-004-A Revised draft EIS Channel – General Arrangement Issued by Ports North 12 December 2016

No reference 2015 Channel Widening Proposal – 100 meter Channel EIS Design Issued by Ports North 12 August 2016

3527-SK02, SK03 Various drawings of Northern Sands Quarry Issued by Flanagan Consulting Group 11 November 2016

3527-SK01 Arial of Wah Day Area Issued by Flanagan Consulting Group 4 November 2016

No reference Spread sheets with dredged quantities – target depths Issued by Ports North 13 January 2017

No reference Arial of Stiff Clay Disposal Site Issued by Ports North 25 January 2017

No reference Arial of Yorkeys Pipeline route – Barron Delta – Northern Sands Issued by Ports North 25 January 2017

25th January 2017

137632122-001-R-Rev0 Preliminary Geotechnical Investigation – Factual Report – Cairns Shipping Development Project (EIS) – Trinity Inlet, Cairns Issued by Golder Associates Pty Ltd for Ports North September 2013

1546223-006-R-Rev0 Draft Stage 1B Marine Studies – Cairns Shipping Development Project Issued by Golder Associates Pty Ltd for Flanagan Consulting Group 26 August 2016

1546223-008-R-Rev1 Assessment of Materials Proposed for Dredging – Cairns Shipping Development Project Issued by Golder Associates Pty Ltd for Flanagan Consulting Group 16 January 2017

3527-SK04 Drawings of Northern Sands – Option 1 Issued by Flanagan Consulting Group 20 January 2017

No reference Channel long-sect material props Issued by Ports North 25 January 2017

No reference Northern Beaches Pump out Location Issued by Ports North 25 January 2017

No reference Northern Sands pipeline options Issued by Ports North 25 January 2017

27th January 2017

3527-SK06 Wah Day DMPA Issued by Flanagan Consulting Group 19 January 2017

3527-SK01A Wah Day DMPA Issued by Flanagan Consulting Group 19 January 2017

AUS0264 Admiralty Chart – Trinity Inlet

No reference Backhoe, barge and tugboat information

7th April 2017

Soft copies of excerpts of the following reports and/or summaries containing:1. Golder’s Report extract with dredge volumes for design channel2. Spreadsheet with above volumes factored up pro-rata to 900,000 m3 for TSHD.3. Aerial mark up of existing channel target depths4. Existing channel target depth table5. Dredging Quantities table with the proposed TARGET depths as “New Design Level” including insurance and overdredging allowance. Note the Design Declared Depth is 8.8m over the whole channel.

Note: Ports North made the above-mentioned information available in soft copy format.

The above-received information has been taken to be the opinion of the issuing partiesand has not been independently verified or checked.

The soil characteristics of the material to be dredged have been derived from the three above-mentioned Golder reports received on the 25th January 2017.In particular the Appendix C of the 26th August 2016 report was very useful in obtaining a further understanding of the soil characteristics of the “soft” and the “stiff” clays.

The theoretical quantities to be dredged and the split between “soft” and “stiff” as mentioned in the 16th January 2017 Golders report have been taken as facts.The split has been based on approx. 52km of longitudinal lines and traverse seismic survey lines, presumably executed in 2016, of which no details were provided.

Seismic Reflection Survey (sub-bottom profiling) shows layers and no characteristics, is prone to signal absorption and scattering, shows multiple reflections and with whichdiscontinuities will reflect part of the signal.Seismic Refraction Survey measures the seismic velocity of the sub soil and requirescomplex data acquisition and interpretation.Aquares Resistivity Survey can measure to approx. 25-meter below sea floor depth in marine environments producing a high-resolution data set. The system is not effected by absorption and scattering and presents a qualitative and quantitative 4D geomodel.

It is assumed that the split between “soft” and “stiff” Clay has been based on a Seismic Reflection Survey executed over the “stiff” Clay areas.

The materials to be dredged by the TSHD in the inner harbour and the entrance channel has been evaluated and split into the below mentioned 2 soil types. The following area/soil split up has been based on previous and recent informationmade available:

Very soft silty Clay, medium to high plasticity.PP range <10 to 50 kPa average 15 kPaS vane all values < 10 kPa average < 10 kPaIn situ Shear vane range 4 to 10 kPa average 8 kPaMoisture content average 86Liquid Limit average 64Plastic Limit average 40

Clay < 2 mu 37%Medium Silt < 20 mu 70%Silt < 60 mu 91%Fine Sand < 200 mu 98%

Bulk Density range 1.10 to 1.63 t/m3 average 1.34 t/m3

This material characteristic is predominantly found in the top layers of the dredge area and will be dredged by the TSHD in one operation with the under laying soft clay layer.

Soft silty Clay, medium to high plasticity. PP range 20 to 50 kPa average 35 kPaS vane all values +/- 10 kPa average 10 kPaIn situ Shear vane average 14 kPaMoisture content average 66Liquid Limit average 49Plastic Limit average 29

Clay < 2 mu 61%Medium Silt < 20 mu 94%Silt < 60 mu 98%Fine Sand < 200 mu 98%

Bulk Density range 1.30 to 1.69 t/m3 average 1.54 t/m3

This material characteristic is predominantly found in the lower layers of the dredge area and will be dredged by the TSHD in one operation with the overlaying soft clay layer.The majority of the material dredged will consist of the very soft silty Clay.

The above-mentioned materials are to be dredged by the TSHD and pumped ashore at the Northern Sands Quarry area.The “soft” Clay will be removed by the TSHD prior to the dredging of the “stiff” Clay by the Backhoe Dredger in order to avoid double mobilisation of the Backhoe spread.

During the dredging of the “soft” Clay, the TSHD will also remove the intermediate firm silty Clay layer, leaving only the “stiff” Clay to be dredged by the Backhoe dredger in a later stage.This reducing of the “stiff” Clay could be driven by the restrictions of the storage area and most probably for economic reason, which will be assessed by comparing the BHD production and costs estimate with this TSHD production and budget cost estimate.

The Golder summary Report of 16th January 2017 makes note of the occurrence of sand layers in the Inner harbour as encountered in a number of boreholes. The thickness of the sand layers varies between 0.2 and 0.75 m, however the extent of the sands has not been assessed. It is noted that the shell contents within the sands were inferred to range from 20 to 40% of the total mass on visual observation.This fine to coarse-grained Sand will presumably be dredged by the TSHD during the “soft” Clay dredging operations. The pumping ashore of fine to coarse grained Sand with 20 to 40% shell content will require more pumping power as the critical velocity will be higher than for pumping “soft” Clay.The production and cost estimate for the TSHD has been based on the soft silty Clay with only small quantities of max. 300 m sand.

The January Golder Summary Report concluded that the majority of the PASS material has sufficient neutralising capacity to classify them as self-neutralising PASS.The Golder Report also notes the locations where PASS material without sufficient neutralising capacity has been identified and it is assumed that all material within these nominated locations will be treated as PASS.

The total quantity of PASS material is assessed to be 247,892 m3.

The dredging of this PASS material by the TSHD will be given priority and will be dredged in an early stage in order to cover this material with self-neutralising PASS material at the Northern Sands Quarry pond. This dredging sequence needs to beaddressed in the TSHD Dredge Management.It is assumed that all dredged material disposed of in the Northern Sands Quarry willremain under water.

The dredging methodology as envisaged at this time and date has been based on the disposal of the capital dredged material in onshore disposal areas, while the maintenance dredging component will still be placed in the offshore material relocation area.

The most economic on-shore disposal solution would be to find an area at a short pumping distance and close-by to the dredging area. This would have opened up opportunities to dredge the “stiff” Clay, together with the “soft” Clay of those areas, with a Cutter Suction Dredger and the “soft” Clay in the entrance channel with a Trailing Suction Hopper Dredger and pumping all materials ashore over a relatively short pumping distance into the same area.

This option seems not to be feasible and the Northern Sands Quarry solution has beenassessed in this report.

The selection of the TSHD has been based on the revised design, which now has anarrower channel, restricting the overall length of the TSHD to be deployed. The length of the most economic TSHD Marieke will not allow her to turn in the 100 meter wide channel, not for safety reasons as well as for probable additional re-suspension of soft material due to propeller wash and bow-thruster agitation flows.

The TSHD Marieke has been selected mainly for her overall length and loaded draught, but also in view of her pumping ashore capabilities.

TSHD Marieke

Year built 2006 IHCLOA [length over all] 97.5 m LBP [length between perpendiculars] 85.0 mBreadth 21.6 mDepth 7.6 mDredging draught 7.1 m Hopper capacity 5,320 - 5,600 m3

Total installed power 6,776 kWPump shore power 4,050 kWPropulsion sailing 4,050 kW Propulsion dredging 3,450 kW Bow Thruster 450 kW Dredge pipe(s) 1x1000mmLocation dredge pipe Port side aft Discharge pipe dia 900 mm Sailing speed unrestricted 12.8 knots

Net Tonnage 1,501 TGross Tonnage 5,005 T Dead Weight Tonnage 8,387 T

Based on the calculations for the required pumping power and the calculated location of the booster station, the following floating booster station was selected for the production and budget cost estimate.

BOOSTER STATION DI 509

Year built 1987 / 2006 Pontoon:Length overall 58.5 m Breadth overall 18.3 mMoulded depth 3.8 mDraught 2.5 m Booster pump: Total installed power 4,935 kWPump power 4,475 kW

The dredging of the inner harbour requires a high degree of manoeuvring which requires ample propulsion and bow-thruster power.The dredging of the entrance channel requires turning at specific areas with the same requirements on the TSHD specifications.

The widening of the entrance channel requires dredging of soft Clays along and on top of the batters, which will be executed dependent on the tide, which has resulted in the calculated loading times for the various areas. This operation not only requires good seamanship but also adequate manoeuvring power.

As a result of the “very limited overflow dredging” preference in the soft silty Clay theTSHD Marieke is assessed as having the largest hopper capacity possible.

With a maintained dredged insurance depth of the Cairns Shipping Channel and Harbour of 8.3 m- CD or deeper and a tidal range of 0.7 m at MLWS and 2.55 m at MHWS, the TSHD Marieke will have a UKC of at least 1.5 meter at all times within the present channel boundaries.

The dredging of the shallow batters will be executed at the beginning of the loadingcycle and during high water. This will accommodate the TSHD Marieke to dredge at approx. -3.5 m CD with the support of the tugboat with sweepbar to bring the batters down.

The production estimate for the gross dredged quantities of 710,000 and 900,000 situ m3 has been attached to this report.

The inner harbour and entrance channel dredge area has been divided in 8 distinct areas.

The plan view of the areas to be dredged and the quantity spread sheets would assume that there might be sufficient options to sweep large quantities with the sweepbar. However when studying the cross sections it is obvious that there is not much depth below the proposed channel design level to accommodate such an optimisation.The majority of the material needs to be dredged by the TSHD Marieke and disposed of at the Northern Sands Quarry area.Based on the cross sections an assessment has been made of the quantity that could be swept in the deeper areas.

The average hopper load for the various areas is calculated based on the average depth, the occurrence of ‘stiff’ Clay in the area and the effect of spot hunting.

The effective loading time for all areas has been calculated to be 35 minutes with 5 minutes overflow to replace the “softer” top layer and to improve the overall loaded density in the hopper.

The LMOB [Lean Mixture Over Board] and turning times are assessed based on the layout of the to be dredged areas. The LMOB is instrumental to achieve the assessed average hopper load.

Some areas, specifically in the entrance channel, have steep and high banks, which will not facilitate the option to turn the TSHD Marieke during and/or after the loadingprocess, at the most optimal location. These required additional sailing times are incorporated in the cycle times.

The calculated sailing times between the dredging area and the pumping ashore mooring location have been based on the sailing speed limitations as laid down in the Port of Cairns speed restrictions, being 10 knots seaward of beacon 15, 8 knots inward of beacon 15 and an assumed safe sailing speed of 6 knots at the inner harbour.Due to the squat effect at the remainder of the sailing route a restricted sailing speed of 11 knots with a full load and 12 knots empty has been calculated.

The requirement has been expressed not to have the TSHD staying in position at the pump ashore location using its own propulsion.Therefor additional time has been calculated to anchor or moor the TSHD after which the floating pipeline coupling procedure can be started.

The pumping ashore will start with filling the pipeline with water, after which the booster station will be added, followed by adding mixture from the TSHD.When the hopper is empty water is pumped to the Northern sands area to clean the pipeline before the pumping operation is stopped.

The weekly delays are assessed based on the local circumstances:The weather delay has been based on the Cairns wave heights and periodsNo cyclone delays are includedThe shipping delay has been assumed to be 6 hrs/week. This needs to be checked as no information has been made available to asses this delay item.

The above explained cycle time elements and the operational hours per week resulted in the weekly production for the various areas and the execution duration.

The dredging spread will consist, apart from the above mentioned TSHD Marieke and the floating booster station DI 509, out of the following supporting equipment.

A multicat/shoalbuster with a bollard pull of 45T will be deployed at the pump ashore location to support the TSHD Marieke with the anchoring/mooring operations and the floating pipeline coupling activity.The multicat/shoalbuster will be used for the bunkering of the floating booster station and will be moored along the booster station when not operational.The multicat/shoalbuster will be working day and night shift.

A tugboat with a bollard pull of 25T will be deployed for the sweepbar operations. The tugboat will be working in dayshift only.

A launch, with 460 kW propulsion, will be deployed for the survey operations and the transport of personnel. The launch will be working in dayshift and will be on standby during the night shift.

A small spreader pontoon with 4 winches and a diffuser will be used at the Northern Sands Quarry for the controlled disposal of the pumped material.

The pumping ashore mooring location for the TSHD Marieke will be at the -8 m LATcontour line.

An under keel clearance of at least 1 meter at any tide was assumed not only to accommodate for the ships wave movements but also for the restraint of the seabed agitation due to the propeller wash.

The following pipeline lengths have been assessed based on the available information:Self-Floating pipeline, with a minimal length for a moored/anchored TSHD, being 200 meterSubmerged pipeline, with the booster incorporated, being 3,000 meter

Landline, with bends and possible pipe bridge, being 4,800 meterFloating pipeline, at the Northern Sands area, being 300 meter

The calculations with the pumping power of the TSHD Marieke and the booster station DI 509 indicate a location of the booster station at approx. 2,400 meter behind the TSHD and thereby approx. 800 meter from the shore.The pontoon of the DI 509 has sufficient freeboard to incorporate her in the submerged pipeline at this location.

The pumping ashore process will start with the TSHD Marieke pumping water soon after being coupled to the floating line. Once the water has passed the booster station, the booster engineer will engage the pumps and start assisting with the pumping process.Once the pipeline is filled and water has reached the reclamation, the TSHD crew will start the process of pumping the material from the hopper. Once the hopper is almost empty the pipeline is cleaned with water in order to avoid blockage when the next load is pumped.

This process will result in a vast amount of additional water to be pumped to the Northern Sands Quarry area.Calculations of this process have been made in the production sheets for the 710,000 and 900,000 m3 options indicating the expected volume of water and mixture pumped and the resultant dilution factor.

A pond filling method with a spreader pontoon equipped with a diffuser and sufficient floating line will reduce the suspended solids in the higher layers of the pond and thereby create the greatest possibility to stay within the set Total Suspended Solids trigger values. Further study and assessment is required.

The pumping of the fine to coarse Sand layers with the mentioned shell content of 20 to 40% might not be possible as the pumping of coarse Sand and particularly shells will require a much higher pipe velocity and resulting pumping power in order to avoid the tendency to block the pipeline.The calculations show that we can accommodate a small quantity of max. 300 msand to be pumped mixed with the soft silty Clay.

The mobilisation and demobilisation cost estimate is based on the following assumptions:

The TSHD Marieke from and back to SingaporeThe Booster DI 509 from and back to Singapore towed by the Shoalbuster on her own keelThe Shoalbuster from and back to Singapore towing the booster DI 509The Tugboat from and back to BrisbaneThe Launch locally hired in Cairns or close surroundingsThe various pipeline components from and back to Batam

All costs include preparations, port clearance, transportation and AQIS hull cleaning.

The details, general information and cost principles have been attached to this report and will form an integral part of the report and the estimates.

It should be noted that the budget cost estimate is based on 1Q2017 price levels.

The M&R and D+I calculations for the TSHD Marieke and the floating booster station DI 509 are based on the indexed CIRIA valuation for 2017.

Crew costs are based on the 2017 EBA rates and safe manning levels for pumping ashore operations.

The fuel costs are based on the Brisbane Bunker Prices of 13th April 2017, beingtrending to 600 US$/MT.

The exchange rate € - AUD used in the calculations is set to 0.7

Environmental monitoring has not been incorporated in the scope of work nor in the budget cost estimate.

Dredging of the gross quantities only, no overdredging has been allowed for in the calculations.

No cyclone events or cyclone moorings are part of the budget cost estimate.

The deployment of a bed levelling device will be the prerogative of the dredging contractor and will depend on his selected work method, the equipment deployed and the availability of a bed leveller, also called a sweep bar operation.

The bed leveller will optimise the dredge efficiency, especially when the firmer intermediate Clay layers are dredged with a TSHD, and as an extra will slightly minimise the dredged quantity.

The bed leveller or sweep bar also is essential to move material from the top of the batters to the toe area for further dredging by the TSHD.Bed levelling will result in transporting material in front of a sweep bar over relativelyshort distances, in the order of 20 to 100 meter, depending on the soil to be moved and the configurations of the sweep bar arrangement and the power of the tugboat.

The sweepbar operation has been incorporated in the presented production estimate and budget cost estimate.

The installation of the delivery pipe for the pumping ashore operations to the Northern Sands Quarry area will require a proper route investigation to define whether there will

be adequate space to install the pipeline. Special attention will have to be given to the public safety, as the pipeline will be infringing on areas open to the public.

No clearing operations have been incorporated in the budget cost estimate.

The production and budget cost estimate is based on the data made available and calculations based on this information.

Jack HC KerklaanAkuna Dredging Solutions Pty Ltd

Camp Mountain, 17th April 2017

Attachments:

General Information and Cost PrinciplesProduction estimatesCost estimates

CAIRNS SHIPPING CHANNELApril 2017

GENERAL INFORMATION and COST PRINCIPLES

The cost level of the estimate is based on prices at 1Q2017.

The M&R and D+I calculations for the TSHD and the Booster station are based on the indexed CIRIA valuation for 2017.

Crew costs are based on the 2017 EBA rates and safe manning levels for pumping ashore operations.

The fuel costs are based on the Brisbane Bunker Prices of 13 April 2017, being 600 US$/MT.

The exchange rate € - AUD used in the calculations is 0.7

The mobilisation/ demobilisation costs are based on the following assumptions:TSHD from and back to Singapore on own keelBooster station from and to Singapore towed by the Multicat/ShoalbusterMulticat/shoalbuster from and back to Singapore on own keel and towing the booster stationTugboat from and to Brisbane on own keelLaunch local hire in Cairns or close surroundingsPipelines and spreader pontoon from and back to Batam

Costs include preparations, port clearance, transportation and AQIS hull cleaning.

Pipeline, all with a diameter of 900mm, with lengths of:Floating pipeline, short length for a moored TSHD, being: 200 mSubmerged pipeline, with the booster in the line, being: 3,000 mLandline, with bends and pipe bridge(s), being: 4,800 mFloating line, at the Northern Sand area with a small spreader pontoon, being: 300 m

Installation of floating pipeline, submerged pipeline and booster station with the Multicat and Tugboat.Assumed sufficient beach space available to weld the various submerged pipeline sections.

Installation of landline.Assumed pipeline route is cleared and accessible for installation crew and equipment.

Site establishment and preliminariesDocuments and approvals by Management Staff only working from their head office

Site and survey staff, partly expat and partly localLocally rented office.No workshop foreseen due to the small quantity and the soft material.

The following operations of the dredging spread are the bases of this cost estimate:TSHD 5,600m5, Marieke type, dredging in channel areas and pumping ashore. Operational 135 hrs/week.Booster station, DI509 4,475 kW type, positioned in the submerged line. Operational 40 hrs/week.Multicat, 45T Bollard Pull Shoalbuster type, for anchoring and coupling TSHD and bunkering booster. Day and Night shift.Tugboat, 25T Bollard Pull type, for sweepbar operations. Dayshift only.Launch, 460 kW type, for survey and personnel transport. Dayshift working and standby during nightshift.Small spreader pontoon, with 4 shore winches, at the Northern Sands Quarry.

Operational DelaysWeather delay based on Cairns wave heights and periods, approx. 10% being 12 hrs/week.No cyclone delays included nor cyclone moorings in the costs.Shipping delays assumed 6 hrs/week. Needs to be checked, no information made available.

Booster locationCalculations show that the booster needs to be approx. 800 meter offshore. Booster pontoon has sufficient freeboard.

Pumping with 4,050 kW TSHD and 4,475 kW booster result in above critical velocity in the dia 900mm pipeline.Small quantities of 300 mu sand can still be transported. No shells.Northern Sands pond level assumed at RL 3.5 m AHD.

TSHD pumping ashore mooring location seaward of the - 8m LAT contour line

TSHD sailing speedsAs per the Port of Cairns speed restrictions: 10 knots seaward of B15, 8 knots inward of B15 and 6 knots in Port.Due to squat effect unrestricted full load speed 11 knots and unrestricted empty speed 12 knots.

Pre-sweeping with tugboat is assumed to be 1.5 weeks before operations with the TSHD start.According to the cross-sections there is not much depth below the proposed channel design level to sweep material into. Majority of material need to be dredged and transport to the Northern Sands Quarry.Shallow batters to be swept partly before and during the dredging operations.

LMOB (Lean Mixture Over Board) and sailing to turning areas are incorporated in the production estimate.Overflow of 5 minutes at the end of the loading cycle.

Environmental monitoring has not been incorporated in the scope of work nor in the costs.

Dredging of indicated gross quantity only, no overdredging allowed for in the calculations.

CAIRNS SHIPPING CHANNELDREDGED QUANTITY GROSS 710,000 m3

April 2017PRODUCTIONS

Service Hours / week 168Delays / week 33

Bunkering 4Technical 8Weather 12OperationalShipping 6Blockage/debrisOther delays 3

Operational Hours / week 135

Cycle times and weekly productionDredging area Smith Creek Crystal Bend TOTAL

Swing basin Swing basinFrom Chainage 10,800 11,500 13,250 14,500 16,500 18,500 20,500 22,500To Chainage 11,500 13,250 14,500 16,500 18,500 20,500 22,500 24,500

QuantityGross (incl. OD) situ m3 43,243 36,980 15,284 148,371 259,712 166,709 33,411 6,290 710,000By Sweep bar % - 5 5 5 - - 10 5

situ m3 - 1,849 764 7,419 - - 3,341 315 13,687By TSHD situ m3 43,243 35,131 14,520 140,952 259,712 166,709 30,070 5,976 696,313

Layer thickness m 0.8 0.8 - 1.3 0.8 0.3 0.3 - 0.5 0.3 - 0.8 0 - 0.8 0.1Load in Hopper situ % 40 42 40 47 48 50 42 38

situ m3 2,240 2,352 2,240 2,632 2,688 2,800 2,352 2,128

Cycle:Loading min 35 35 35 35 35 35 35 35Overflow min 5 5 5 5 5 5 5 5Lean Mixture Over Board min 6 10 55 31 22 16 34 105Turning min 15 11 5 5 5 5 8 5Sailing to turning area min - - 7 - 20 28 24 -Sailing Loaded min 95 85 66 58 51 44 38 33Anchoring min 10 10 10 10 10 10 10 10Coupling min 5 5 5 5 5 5 5 5Filling pipeline min 25 25 25 25 25 25 25 25Pumping mixture min 36 37 36 38 38 38 37 35Cleaning pipeline min 20 20 20 20 20 20 20 20Sailing Empty min 92 82 63 55 48 42 35 31Total Cycle min 344 325 332 287 284 273 276 309

Trips per week 23.5 24.9 24.4 28.2 28.5 29.7 29.3 26.2

Weekly productionHopper m3 /week 52,744 58,619 54,651 74,283 76,665 83,077 69,026 55,783

Duration weeks 0.82 0.60 0.27 1.90 3.39 2.01 0.44 0.11 9.52

Total munber of loads 19.3 14.9 6.5 53.6 96.6 59.5 12.8 2.8 266

Northern Sands QuarryVolume pumped

Filling pipeline m3 101,351 78,417 34,031 281,155 507,250 312,579 67,120 14,742 1,396,646Pumping mixture m3 135,520 106,110 45,504 375,463 671,889 407,246 90,823 19,460 1,852,015Cleaning pipeline m3 81,081 62,734 27,225 224,924 405,800 250,064 53,696 11,794 1,117,317Total water and mixture m3 317,952 247,261 106,759 881,542 1,584,939 969,889 211,640 45,996 4,365,978

Situ m3 (check) 43,243 35,131 14,520 140,952 259,712 166,709 30,070 5,976 696,313Dilution factor 6.35 6.04 6.35 5.25 5.10 4.82 6.04 6.70 5.27

CAIRNS SHIPPING CHANNELDREDGED QUANTITY GROSS 900,000 m3

April 2017PRODUCTIONS

Service Hours / week 168Delays / week 33

Bunkering 4Technical 8Weather 12OperationalShipping 6Blockage/debrisOther delays 3

Operational Hours / week 135

Cycle times and weekly productionDredging area Smith Creek Crystal Bend TOTAL

Swing basin Swing basinFrom Chainage 10,800 11,500 13,250 14,500 16,500 18,500 20,500 22,500To Chainage 11,500 13,250 14,500 16,500 18,500 20,500 22,500 24,500

QuantityGross (incl. OD) situ m3 54,815 46,877 19,374 188,076 329,212 211,321 42,352 7,973 900,000By Sweep bar % - 5 5 5 - - 10 5

situ m3 - 2,344 969 9,404 - - 4,235 399 17,350By TSHD situ m3 54,815 44,533 18,405 178,672 329,212 211,321 38,117 7,574 882,650

Layer thickness m 0.8 0.8 - 1.3 0.8 0.3 0.3 - 0.5 0.3 - 0.8 0 - 0.8 0.1Load in Hopper situ % 40 42 40 47 48 50 42 38

situ m3 2,240 2,352 2,240 2,632 2,688 2,800 2,352 2,128

Cycle:Loading min 35 35 35 35 35 35 35 35Overflow min 5 5 5 5 5 5 5 5Lean Mixture Over Board min 6 10 55 31 22 16 34 105Turning min 15 11 5 5 5 5 8 5Sailing to turning area min - - 7 - 20 28 24 -Sailing Loaded min 95 85 66 58 51 44 38 33Anchoring min 10 10 10 10 10 10 10 10Coupling min 5 5 5 5 5 5 5 5Filling pipeline min 25 25 25 25 25 25 25 25Pumping mixture min 36 37 36 38 38 38 37 35Cleaning pipeline min 20 20 20 20 20 20 20 20Sailing Empty min 92 82 63 55 48 42 35 31Total Cycle min 344 325 332 287 284 273 276 309

Trips per week 23.5 24.9 24.4 28.2 28.5 29.7 29.3 26.2

Weekly productionHopper m3 /week 52,744 58,619 54,651 74,283 76,665 83,077 69,026 55,783

Duration weeks 1.04 0.76 0.34 2.41 4.29 2.54 0.55 0.14 12.07

Total munber of loads 24.5 18.9 8.2 67.9 122.5 75.5 16.2 3.6 337

Northern Sands QuarryVolume pumped

Filling pipeline m3 128,473 99,404 43,137 356,394 642,992 396,227 85,082 18,687 1,770,396Pumping mixture m3 171,786 134,508 57,681 475,939 851,689 516,227 115,128 24,666 2,347,625Cleaning pipeline m3 102,778 79,523 34,510 285,115 514,394 316,982 68,066 14,949 1,416,317Total water and mixture m3 403,037 313,436 135,328 1,117,448 2,009,075 1,229,435 268,276 58,303 5,534,339

Situ m3 (check) 54,815 44,533 18,405 178,672 329,212 211,321 38,117 7,574 882,650Dilution factor 6.35 6.04 6.35 5.25 5.10 4.82 6.04 6.70 5.27

CAIRNS SHIPPING CHANNELDREDGED QUANTITY GROSS 710,000 m3 April 2017

ESTIMATE

Description Unit Qty. Rate Amount

MOBILISATIONTSHD Marieke Lump Sum 1 1,378,227 1,378,227TSHD Booster DI509 Lump Sum 1 381,428 381,428MULTICAT Lump Sum 1 1,304,097 1,304,097TUGBOAT Lump Sum 1 185,988 185,988LAUNCH Lump Sum 1 43,251 43,251Pipelines and spreaderpontoon Lump Sum 1 1,975,762 1,975,762TOTAL MOBILISATION 5,268,752

INSTALLATIONBooster station Lump Sum 1 315,102 315,102Pipelines Lump Sum 1 1,769,458 1,769,458TOTAL INSTALLATION Lump Sum 2,084,560

SITE ESTABLISHMENT and PRELIMINARIESDocuments and approvals Weeks 4.0 42,867 171,469Staff preparations Weeks 4.0 114,559 458,238Survey Staff for in-survey Weeks 3.5 29,399 102,895Survey launch and equipment Weeks 3.5 105,850 370,475Pre-sweeping with sweepbar Weeks 1.5 142,761 214,141TOTAL ESTABLISHMENT and PRELIMINARIES Lump Sum 1,317,218

DREDGINGTSHD Marieke Weeks 9.5 720,041 6,854,380TSHD Booster DI509 Weeks 9.5 304,730 2,900,852MULTICAT for TSHD mooring and booster Weeks 9.5 294,946 2,807,717TUGBOAT for sweepbar operations Weeks 9.5 142,761 1,359,002LAUNCH for survey and personnel transport Weeks 9.5 93,085 886,120Pipelines and spreaderpontoon Weeks 9.5 78,287 745,243TOTAL DREDGING 15,553,314

DREDGE MANAGEMENTStaff Weeks 9.5 113,734 1,082,685Survey Weeks 9.5 33,930 322,995TOTAL MANAGEMENT 1,405,680

SITE CLEARANCEStaff site clearance Weeks 4.0 114,559 458,238Survey Staff for out survey Weeks 2.0 29,399 58,797Survey equipment Weeks 2.0 105,850 211,700Post-sweeping with sweepbar Weeks 1.0 142,761 142,761Booster station Lump Sum 1 206,735 206,735Pipelines dismantling Lump Sum 1 1,093,695 1,093,695TOTAL SITE CLEARANCE 2,171,926

DEMOBILISATIONTSHD Marieke Lump Sum 1 790,924 790,924TSHD Booster DI509 Lump Sum 1 206,932 206,932MULTICAT Lump Sum 1 838,475 838,475TUGBOAT Lump Sum 1 129,775 129,775LAUNCH Lump Sum 1 27,184 27,184Pipelines and spreaderpontoon Lump Sum 1 1,555,590 1,555,590TOTAL DEMOBILISATION Lump Sum 3,548,880

TOTAL PROJECT ESTIMATE 31,350,331

CAIRNS SHIPPING CHANNELDREDGED QUANTITY GROSS 900,000 m3 April 2017

ESTIMATE

Description Unit Qty. Rate Amount

MOBILISATIONTSHD Marieke Lump Sum 1 1,378,227 1,378,227TSHD Booster DI509 Lump Sum 1 381,428 381,428MULTICAT Lump Sum 1 1,304,097 1,304,097TUGBOAT Lump Sum 1 185,988 185,988LAUNCH Lump Sum 1 43,251 43,251Pipelines and spreaderpontoon Lump Sum 1 1,975,762 1,975,762TOTAL MOBILISATION 5,268,752

INSTALLATIONBooster station Lump Sum 1 315,102 315,102Pipelines Lump Sum 1 1,769,458 1,769,458TOTAL INSTALLATION Lump Sum 2,084,560

SITE ESTABLISHMENT and PRELIMINARIESDocuments and approvals Weeks 4.0 42,867 171,469Staff preparations Weeks 4.0 114,559 458,238Survey Staff for in-survey Weeks 3.5 29,399 102,895Survey equipment Weeks 3.5 105,850 370,475Pre-sweeping with sweepbar Weeks 1.5 142,761 214,141TOTAL ESTABLISHMENT and PRELIMINARIES Lump Sum 1,317,218

DREDGINGTSHD Marieke Weeks 12.1 720,041 8,688,652TSHD Booster DI509 Weeks 12.1 304,730 3,677,137MULTICAT for TSHD mooring and booster Weeks 12.1 294,946 3,559,078TUGBOAT for sweepbar operations Weeks 12.1 142,761 1,722,679LAUNCH for survey and personnel transport Weeks 12.1 93,085 1,123,251Pipelines and spreaderpontoon Weeks 12.1 78,287 944,674TOTAL DREDGING 19,715,471

DREDGE MANAGEMENTStaff Weeks 12.1 113,734 1,372,418Survey Weeks 12.1 33,930 409,430TOTAL MANAGEMENT 1,781,849

SITE CLEARANCEStaff site clearance Weeks 4.0 114,559 458,238Survey Staff for out survey Weeks 2.0 29,399 58,797Survey equipment Weeks 2.0 105,850 211,700Post-sweeping with sweepbar Weeks 1.0 142,761 142,761Booster station Lump Sum 1 206,735 206,735Pipelines dismantling Lump Sum 1 1,093,695 1,093,695TOTAL SITE CLEARANCE 2,171,926

DEMOBILISATIONTSHD Marieke Lump Sum 1 790,924 790,924TSHD Booster DI509 Lump Sum 1 206,932 206,932MULTICAT Lump Sum 1 838,475 838,475TUGBOAT Lump Sum 1 129,775 129,775LAUNCH Lump Sum 1 27,184 27,184Pipelines and spreaderpontoon Lump Sum 1 1,555,590 1,555,590TOTAL DEMOBILISATION Lump Sum 3,548,880

TOTAL PROJECT ESTIMATE 35,888,657

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7 November 2018Acad No. 3527-SK21D

3527-SK21D

NORTHERN SANDS DMPA

CAIRNS SHIPPING DEVELOPMENT

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(07) 4944 1200MACKAY

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20181116 TN-1545.00-2 Rev 2 Page 1

Technical Note

Project Number: POR1545.00 Project Name: CSD Project, Revised Draft EIS

Date: 16/11/18 Doc Ref: TN-1545.00-2

Client: Ports North

Subject: Dredge Material Placement Assessment –Northern Sands DMPA

1 Introduction

The key objective of this work is to simulate the placement of 740,000m3 of soft clay dredgematerial into the NS DMPA to determine if the discharge WQ limits can be achieved and toprovide advice on improvements to water management opportunities which may be available.

This Technical Note has been prepared to document outcomes of the DMPA simulation for theNorthern Sands site.

2 Material Characterisation and Laboratory Testing

Full details of the material characteristics and laboratory testing are as previously reported inChapter 4 of the “Dredging and Dredge Material Placement Assessment Report”, which formedAppendix AC of the revised draft EIS for the Cairns Shipping Development Project (BMT JFAConsultants, 2017). The results from the sample analysis of the composite samples areprovided in Table 2-1 below.

Table 2-1: Summary of Geotechnical Index Properties for Composite Samples

Property Composite #1(Widening “Muds”)

Composite #2(Deepening “Sediments”)

Clay Plasticity Highly Plastic Highly Plastic

Liquid Limit (%) 56 70

Plastic Limit (%) 21 27

Plasticity Index (%) 35 43

Apparent Particle Density (t/m3) 2.73 2.65

Organic Content (%) 3.5 4.3

% Fines (<60μm) 90% 98%

20181116 TN-1545.00-2 Rev 2 Page 2

3 DMPA Concept Plan and Management Strategies

3.1 Concept Layout and Performance Criteria

The DMPA concept developed by Flanagan Consulting Group (FCG) are shown in FCGSketch 3527- SK 21D; Water Management Strategies were provided in the worksheet NorthernSands - Storage Volumes Revised design 750K immediate take off 1m water cover 9-3 weeks180919.xlsx and associated drawing 3527 DESIGN CASE tin JFA 19092018.dwg.

Key details are as follows:

Maximum Bund Height: 4.5m AHD

Maximum Operating Water Level (MOWL): 3.9m AHD

Storage volume at 3.9m AHD is: 2,401,000m3

The DMPA simulation is based on:

Insitu volume of dredged material 750,000m3 (Soft Material). 740,000m3 are dredgedby the TSHD and pumped to the DMPA (the difference remains in channel afterlevelling with sweep bar/plough).

Relocation of tailwater discharge point after placement of PASS material.

- No internal weirs of bunding within the DMPA

- Dredge material will enter the DMPA from the eastern end initially for the disposalof the PASS material (266,000m3), with a tailwater discharge point at the westernend. The dredge material inflow point will then relocate to the western end for theremainder of the dredge program, with the tailwater discharge point to be located atthe eastern end

Minimum tailwater discharge level is +1.0m AHD.

The dredge material is discharged below water level, just above the formed bed levelin order to reduce the distribution of fines through the water column and assist in earliersettlement of the material.

Settling and Consolidation properties of in-situ material will be based on calibratedComposite #1 (‘Muds’) from previous DMPA simulations (BMT JFA 2017)

Design performance requirements for tailwater quality is to limit

- Acute exceedance - Turbidity < 50NTU (83.5 mg/l)1

1 Laboratory testing of the samples revealed the following relationship between turbidity and suspendedsolids TSS (mg/l) = 1.67 x Turbidity (NTU). Refer Section 4.2.4 of the “Dredging and Dredge MaterialPlacement Assessment Report” (BMT 2017)

20181116 TN-1545.00-2 Rev 2 Page 3

4 DMCAT Numerical Modelling

4.1 Model description

Numerical simulations were conducted using the BMT developed Dredged MaterialContainment Assessment Tool (DMCAT) to assess the proposed dredged material placementactivity. In summary, the model consists of a vertical 1-D numerical model for the settling andconsolidation of suspensions coupled to a quasi 1-D steady horizontal flow model. Inputsconsist of the placement area geometry, a time history of the inflow characteristics (i.e. flowrate and sediment concentrations), and calibrated sediment settling and diffusion parameters(calibrated using the laboratory test results). The model returns the expected concentrationand composition of the placed material and the outflow material. The corresponding keyperformance output parameters are the dry density of the placed material at the completion ofthe dredging campaign, and the suspended sediment concentration in the supernatant outflow.For the purpose of distinguishing between sediment carried in suspension and the settledplaced material, a concentration threshold of 100 kg/m3 is applied (concentrations greater thanthis may still be flowable mud).

4.2 Geometry

The model geometry for the DMPA was derived from the supplied storage volume table(Attachment A), along with supplied bathymetric and terrestrial survey data. For the purposesof reproducing the filling process from RL 1.0 to RL 3.90, a trapezoidal model shape wasassumed. The shape of the trapezoid was determined as best fit to the staging profile with thecalculation cell, which produced sufficiently accurate estimates of storage volume betweenthese elevations.

Figure 4-1: Placement storage volume vs water level as detailed in “Northern Sands - StorageVolumes Revised design 750K immediate take off 1m water cover 9-3 weeks 180919.xlsx” (blue)compared with volumes used in DMPA simulation (red)

-15

-10

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0

5

10

0 500 1000 1500 2000 2500 3000

WSL

(mAH

D)

Volume (000m3)

Target Model

20181116 TN-1545.00-2 Rev 2 Page 4

Figure 4-2: Schematic Example of DMCAT Simulation Geometry relative to Northern Sands Site

4.3 Inflow and Water Levels

The DMPA inflow time series consists of a sequence of bulk inflow rates and durations withassociated sediment concentrations. The following details were produced based on theprovided worksheet - Northern Sands - Storage Volumes Revised design 750K immediate takeoff 1m water cover 9-3 weeks 180919.xlsx.

Table 4-1: Dredge Program / Inflow Details

Dredging Stage 1 2 Total

Dredging Duration (wks) 9 3 12

No. Cycles 252 42 294

Cycle Duration (mins) 360 720

Filling pipeline (mins) 25.30 25.30

Pumping mixture (mins) 36.58 36.58

Cleaning pipeline (mins) 20.24 20.24

Pumping downtime (mins) 277.87 637.87

Filling pipeline flowrate (m3/s) 3.46 3.46

Pumping mixture flowrate (m3/s) 3.05 3.05

Cleaning pipeline flowrate (m3/s) 3.46 3.46

Mixture Solids Concentration (kg/m3) 360.92 360.92

Total Solids Mass Pumped (t) 608,914 101,486 710,400

Total Solids Volume Pumped (m3) 634,286 105,714 740,000

20181116 TN-1545.00-2 Rev 2 Page 5

The DMPA water level in the numerical model is controlled in three stages:

From days 0 to 30, water level is maintained at +1.0m AHD (inflow volume = outflowvolume)

From days 30 to 68, tailwater discharge rate is set to less than the inflow rate, whichproduces a water level of +3.9m AHD at day 68.

From days 68 to 84, water level is maintained at +3.9m AHD (inflow volume = outflowvolume)

As the model estimates the placed density at the time of placement (which is lower than thedensity at completion of dredging) and incorporates reproduced geometry (refer section 4.2above), some minor adjustments to the days and rate of fill (relative to the water qualitymanagement) are required in order to comply with the placement constraints (material toremain submerged).

Figure 4-3: Time series of water level during placement

4.4 Simulation Period and Outputs

Outcomes from the DMPA simulations are reported at:

the end of the dredging campaign to estimate short term placed density; and

6 months after the start of dredging: to estimate expected consolidation prior to thecommencement of the following wet season.

18 months after the start of dredging: to estimate expected consolidation in the mediumterm