QUAY STREET SEAWALL UPGRADE - Auckland Council · The alternative seawall upgrade proposed...

CLIENT: AUCKLAND TRANSPORT

PROJECT: DOWNTOWN INFRASTRUCTURE DEVELOPMENT PROGRAMME ECI

CONTRACT NO. 365-18-534-PS

LOCATION: AUCKLAND

PROJECT NO.: DN1158

QUAY STREET SEAWALL

UPGRADE

TITLE: ALTERNATIVE CONSTRUCTION METHODOLOGY FOR RESOURCE CONSENT – JET

GROUT COLUMNS

Revision History: A

Rev Date Description By Approved

A 21/09/2018 ECI Draft Methodology Based On No Design Information

JM JG

B 19/10/2018 Revised according to comments KC JG

Document number: DN1150

Downer Infrastructure Jet Grouting Methodology Project No DN1158 Contract No. 365-18-534-PS Revision B

AUCKLAND TRANSPORT Date 19/10/2018

TABLE OF CONTENTS

1. INTRODUCTION 3

PROJECT BACKGROUND AND OVERVIEW 3 PROPOSED QUAY STREET SEAWALL UPGRADE 4 THIS REPORT 4

2. ASSUMPTIONS 5

3. GENERAL DETAILS APPLICABLE TO ALL SECTIONS 6

SERVICES 6 SITE SETUP 6 JET GROUT COLUMNS 7

4. INDICATIVE PROGRAMME 13

5. PRINCES WHARF SECTION 14

KEY INFORMATION 14 STAGING, SITE ACCESS, PEDESTRIAN AND TRAFFIC MANAGEMENT 15 JET GROUTING DURATION 16 CONSTRUCTION METHOD 16 OBSTRUCTIONS 17 JET GROUTING PLANT 17

6. FERRY BASIN SECTION 18

KEY INFORMATION 19 STAGING, SITE ACCESS, PEDESTRIAN AND TRAFFIC MANAGEMENT 19 JET GROUTING DURATION 21 CONSTRUCTION METHOD 21 OBSTRUCTIONS 21 JET GROUTING PLANT 21 SEAWALL FACING 22 WALER BEAM 23 GROUND ANCHORS 23

SCOUR PROTECTION 23

7. APPENDICES 24

APPENDIX A – JET GROUTING EQUIPMENT 25

APPENDIX B – STAGING DRAWINGS 29



1. INTRODUCTION

Downer – Soletanche Bachy has been engaged by Auckland Transport (AT) to provide an alternative construction methodology to support resource consent applications for the upgrade of the Princes Wharf and Ferry Basin sections of the existing Quay Street seawall.

AT would like to seek resource consent for an alternative seawall design and construction methodology (referred to as the jet grout column option) for the Princes Wharf and Ferry Basin sections of the Quay Street seawall upgrade project (Seawall Project), in addition to the current proposal submitted to Auckland Council. This is a result of the Early Contractor Involvement (ECI) phase of the Seawall Project, where alternative seawall upgrade options have been considered.

The alternative seawall upgrade proposed primarily involves the installation of jet grout columns in the Quay Street road reserve, landward of the existing seawall. The Ferry Basin section also includes works in the coastal marine area, including a new facing to the existing seawall, a waler beam and ground anchors. A rock protecting toe or concrete mattress for scour protection is also proposed in the Ferry Basin section.

The proposal is now to seek resource consent for both the original methodology as submitted and the jet grout column option, for the Princes Wharf and Ferry Basin sections, so that AT has the option to implement either of the options for each section. In summary, consents are currently being sought to authorise the following seawall upgrade options for the three seawall sections:

- Princes Wharf section: Palisade wall OR Jet grout columns

- Ferry Basin section: Post and panel wall OR Jet grout columns

- Queens Wharf to Marsden Wharf section: Palisade wall

This report provides detail regarding indicative construction methodology for the jet grout column option to support the Princes Wharf and Ferry Basin resource consent applications, while a separate report (Auckland Transport Quay Street Seawall Upgrade Construction Methodology for Resource Consent, prepared by Alta, dated 16 April 2018, and referred to as the “Alta Report”) addresses the palisade wall and post and panel wall options.

The construction methods developed are to be flexible enough regarding the final design and provide sufficient information to allow consent conditions to be established.

The Quay Street seawall extends from the western side of Lower Hobson Street to the Western side of Marsden Wharf at the Downtown Ferry Terminal in Central Auckland. The seawall forms the harbour edge of a historical reclamation, which supports Quay Street and the services contained within the road corridor.

It has been established that the existing seawall does not meet current design standards for seismic performance, and that there are sections that are in need of general repair due to scour damage to the surface of the seawall. There is also the opportunity to create resilience to future climate and changing use patterns, particularly the impacts of ship wash as ferry and cruise ship operations intensify their activity.

While the Quay Street seawall upgrade is part of the overall plan for Downtown Auckland, it is also now an important enabler of the wider Downtown Infrastructure Development Programme (Downtown Programme) to ready the precinct for the America’s Cup (AC36) and Asia-Pacific Economic Cooperation (APEC) events in 2021.

The Downtown Programme is a result of a collaboration between AT, Auckland Council and Panuku Development Auckland. The Programme includes a number of projects as part of overall improvements to the city centre. In addition to the upgrade of the Quay Street seawall, the Programme includes relocation of Piers 3 and 4, a proposed Downtown Public Space, a proposed mooring dolphin at the end of Queens Wharf, and proposed streetscape works and bus facilities in Quay Street.

PROJECT BACKGROUND AND OVERVIEW



The proposed seawall has been divided into four sections for the purpose of resource consent applications and construction, as follows (from west to east):

- Princes Wharf section

- Ferry Basin section

- Ferry Building section

- Queens Wharf to Marsden Wharf section

A separate resource consent application is being made for each of the sections, and each section will be constructed as a standalone project once consented. The sections may therefore be constructed sequentially, or there may be some overlap in the construction programme, and this report considers the effects of these scenarios.

Resource consent applications for the Princes Wharf, Ferry Basin and Queens Wharf to Marsden Wharf sections have been lodged.

Design options are still being considered for the Ferry Building section and the resource consent application for this section will be lodged at a later date.

This report contains details relevant to the jet grouting methodology, working space requirements, resources, staging and programme for two sections of the Quay Street seawall:

- Princes Wharf section

- Ferry Basin section

Each section is discussed in detail, but in general the method considers traffic and access requirements, sequencing and staging to maximise efficiency and the associated environmental effects. The base sequencing is indicative and may differ depending on the final design.

PROPOSED QUAY STREET SEAWALL UPGRADE

THIS REPORT



This report provides indicative details of the jet grout column construction methodology based on the current design information and these details may vary following further design development.

The key assumptions are:

- Traffic on Quay Street will be reduced to two car lanes, one bus lane and a bi-directional cycle lane;

- Pedestrian access will be maintained adjacent to the site for Princes Wharf and Ferry Basin sections;

- Auckland Harbour Board fence red lamp posts and the World War I Memorial Beacon will remain in place for the Princes Wharf section and the Auckland Harbour Board fence will potentially be temporarily relocated for the Ferry Basin section;

- The eastern and western Kiosks located in the Ferry Basin section will potentially be temporarily relocated;

- The Ferry Basin section will have works on the seaward side and landward side of the existing seawall;

- Tree 18 for the Princes Wharf and Ferry Basin section will be retained during construction works;

- Construction hours will be generally within the daytime periods prescribed in Rule E25.6.28 of the Auckland Unitary Plan Operative in Part (AUP), Monday to Saturday, and concrete cutting will not be undertaken on Sunday;

- The jet grouting programme has been based on using up to a maximum of three rigs (one for gravity grouting (refer to Section 3.3.1) and two for jet grouting (refer to Section 3.3.2), depending on the final quantity of jet grouting columns) with support plant working in line to maintain space for general plant and truck access. These three rigs would be located within the Princes Wharf section, or the Ferry Basin section, or across both sections;

- Each jet grouting rig is associated with a jet grouting plant; and

- Jet grouting plants are to be located within the working area of the Princes Wharf and Ferry Basin sections.

2. ASSUMPTIONS



Ideally services will be relocated in advance of the jet grouting works commencing.

In the event that services are not re-located at the time of construction, the jet grout column design could be adapted around the existing services and a PVC casing will be installed to protect services in place.

The following services and street furniture has been identified for relocation, protection or design adaptation (i.e. the location of jet grout columns being adapted); stormwater, water, sewer, gas, Chorus, high voltage and low voltage power cables, traffic signals, traffic loops, traffic counters, CCTV cables, lighting columns, way-finding signs, seating, rubbish bins, tree planters, up light and emergency telephones.

Historic train tracks have been identified exiting the Ports of Auckland area in the Queens Wharf to Marsden Wharf section and they may be present in the Princes Wharf and Ferry Basin sections also. These potentially may continue under the existing footpath and into the proposed jet grouting layout. If this assumption is correct, the train tracks will need to be removed.

During services relocation or identification, working areas up to 100m in length may need to be established, requiring temporary diversion of both traffic and pedestrians. Plant, including up to 20 tonne excavators, would be required as well as hydro excavation where working around live services.

Each site would be enclosed with a timber hoarding, 2.4m high. It is intended that all existing concrete pavers would be uplifted, where possible, and these will be stored at an offsite location and re-used upon completion of the project. A 400-500mm thick metaled surface will be laid to provide a level area for plant to operate on. Street furniture, lighting and signs will be removed and temporarily relocated where required. Trees will be temporarily removed for safekeeping and reinstated to suitable tree pits once works are complete.

Existing drains can be covered or relocated to maintain stormwater flows. The site perimeter will also have a temporary asphalt bund, or similar, installed around it to redirect external stormwater flows from site, and also avoid any spillage (such as from grout or drilling fluid) from works areas into public areas.

3. GENERAL DETAILS APPLICABLE TO ALL SECTIONS

SERVICES

SITE SETUP



Jet grout columns are a ground improvement technique that uses a soil and grout mixture to form colums in the soil, improving the structural strength of the soil. Based on experience on the adjacent City Rail Link (CRL) project, grout mixing can be achieved in most of the soils present at the proposed seawall upgrade alignment. Where basalt boulder layers are present, jet grouting may not be feasible, and a gravity grouting (pre-drilling) operation will be required (described in Section 3.3.1) to overcome this hard layer of ground.

Jet grouting (described in Section 3.3.2) will be used in areas where basalt is not present. These methods are described below.

A gravity grouting operation called “pre-drilling” is required for jet grout columns located in the vicinity of the existing seawall, where there is the presence of basalt gravels and boulders. The gravity grouting process is outlined in Figure 1 and involves two main steps described below:

- Step 1: Pre-drilling with a drilling rig from the existing ground level through the basalt boulders layer to identify the extent of this layer; and

- Step 2: Sending a thick grout (bentonite (<5%) mix with cement and water) while extracting rods to backfill the predrilled hole and fill any voids within the basalt boulders.

The predrilling diameter shall be sufficient for the further jetting operation (approximately 200mm diameter is proposed).

Figure 1: Gravity grouting process

The jet grouting operation has to be scheduled several days after the gravity grouting operation. This is to leave enough time for the grout in the pre-drilled hole to set and to avoid any grout mixing between holes already drilled and grouted. The grout/bentonite mix is a low strength mix enabling the jet grout to pass through and install the jet grout column below and above this layer as shown in Figure 2 Jet grout column is to be adapted based on the actual layer of basalt as per Figure 1.

JET GROUT COLUMNS

3.3.1 Gravity Grouting



Figure 2: Jet grout column adapted to basalt layer

Jet grouting is a construction process that employs a high kinetic energy jet in a circular motion, to break down the soil formation, erode the soil particles into suspension and mix the in-situ soils with cement grout.

The jet grouting process is outlined in Figure 3 and involves three distinct physical processes;

1. Breaking down the soil formation using a very high-velocity jet in a circular motion;

2. Introducing and incorporating a binder to the soil suspension in the form of a grout (cement);and

3. Displacing excess material to the surface as spoil.

During the jet grouting process, the withdrawal speed of jet grouting tools is controlled by an on-board computer directly installed on the rig. The withdrawal speed is usually low, and the on-board computer can adjust the withdrawal speed if necessary.

Figure 3 Jet Grouting process

3.3.2 General description of Jet Grouting



The nozzles are essential parts of the jet grouting process. They are located on the drilling tool (Figure 4) and on the “monitor” (which can also be referred to as the “jet grouting tool” and is located between the drilling tool and last rod at the bottom of the drill string) (Figure 5). The small diameter of the nozzle combined with the high pressure pump increases the flow and pressure of the fluid (water or grout) to cut the soil in place and allow mixing of grout with the soil in suspension.

Figure 4: Drilling tool equipped with nozzle Figure 5: “Monitor” (Jet grouting tool) equipped with nozzle

The parameters for the jet-grouting process and the designed final strength of the treated soil depend on a number of characteristics including:

- Type and geotechnical properties of the soil to be treated;

- Radius of action of the jet needed to achieve the required size of the mixed in place structure;

- The required mechanical post-treatment soil properties; and

- Site constraints.

Prior to starting the jet grouting process, a trial may be performed in order to validate and adjust the anticipated jet grouting parameters. These parameters include:

- Pressure and flow rate of the fluid.

- Rotation of the jet grouting tools.

- Withdrawal speed.

- Nozzle diameter

- Grout composition.

These characteristics are controlled at the end of the trial by the following method:

- Diameter checking by coring and Cyljet which is a method of analysing the form of the column using a resistivity test creating a picture of the column below ground as per the example shown in Figure 6.

Figure 6: Example of Cyljet result on jet grout column



- Strength checking by Unconfined Compressive Strength (UCS) testing on cored samples, grout samples and spoil samples.

The jet grouting plant (one per jet grout rig) is comprised of the following equipment:

- 1 High pressure pump (type Soilmec 7T450 or similar) (1 Figures 7 & 8)

- 1 Mixing plant (Type TWM30 or similar) (2 Figures 7 & 8)

- Horizontal or vertical cement silo (3 Figures 7 & 8)

- 1 generator or a transformer to supply the electricity

Figure 7: Example of Jet grouting plant set-up on CRL1 (Auckland)

The jet grouting rig is a Comacchio MC12 (4 Figure 8), or similar, rotary drilling machine equipped with a long mast extension and is specially fitted for jet grouting. The rig is equipped with an on-board computer (Jean Lutz or similar) to control jet grouting parameters and good execution of the column.

Other equipment used in the jet grouting process include:

- Drilling rig for the pre-drilling

- Spoil pit

- Water treatment plant or de-sanding unit (to re-use the water of the pre-drilling and pre-jet)

- Excavator and trucks for spoil removal

- Peristaltic pump (spoil pump) for the spoil transfer between the rig and the spoil pit

- Water tank for storage (5 Figure 8)

- Telehandler.

3.3.3 Plant and Equipment set-up



Figure 8: 3D drawing of jet grouting equipment per rig (Spoil pits will be located within the working area)

The jet grouting process is outlined in Figure 9 and involves four (4 No.) main steps described below.

Figure 9: Jet grouting work sequence

3.3.4 General Jet Grouting methodology

1 2 3 4



Step 1 “Drilling”: The drilling will be done using the pre-jet method whereby water is pumped under reduced pressure from the jet grouting plant to the jetting tools (monitor and drilling tools). The purpose of the pre-jet is to pre-cut the ground in place in order to improve the jet grouting operation, and to reach the required diameter.

Steps 2 & 3 “Jetting”: Once the required depth is reached with the pre-jet (slightly deeper than the design depth), the jet grouting process is undertaken whereby grout is substituted for the water and the pressure is increased. The jet grout column is formed from the bottom to the top. The operator will then transfer control of the rig to the on-board computer system, which will control the upward withdrawal speed. This will ensure that the rods are rotated slowly upward as they are extracted forming a column of ‘soil-cement grout mix’ with the grout evenly distributed throughout the treated volume. Waste material from the process, which is a mix of soil, water and binder (the grout), is recovered at the surface and pumped to the spoil pit before being taken away for disposal (using vacuum trucks for liquid or regular trucks for solid material).

Step 4 Primary secondary “hit and miss”: For the general sequence, the jet grouting columns process is to be implemented by the “hit and miss” approach to optimize overlaps between the columns. As shown in Figure 10 below, for each row of columns the hit and miss approach involves the primary columns being installed first, allowing them to set, and then installing the secondary columns.

Figure 10: Primary secondary “hit and miss” sequence

The maximum volume of grout per column (based on the deepest column proposed) will be approximately 40-45m3 resulting in a production of waste spoil per column of up to 50m3.

Environmental management measures to minimise the environmental impact of the construction works will be addressed in the Environmental Management Plan (to be certified by Council prior to construction starting) and the Environmental Management and Response Plan (EMRP) for the jet grout column option (to be lodged with the jet grout consent application). However, an overview of environmental management measures are provided below:

The noise emitted by the equipment is mainly related to the jet mixing plant and the rig. To ensure that the construction noise limits are met, acoustic barriers will be installed where necessary. This is addressed in greater detail in the addendum to the Marshall Day Acoustics Report, dated Spetember 2018 and the Draft Construction Noise and Vibration Management Plan.

Water management:

Water arising on site as part of the jet grouting process (i.e. from pre-drilling, pre-jet, and cleaning water) can be treated on site using a water treatment plant, or similar, and disposed of in spoil pits. Alternatively, water could be treated and discharged to the existing sewer network in the event that a Trade Waste consent application to Watercare is successful.

Cement for the grout mix will be stored in silos close to the mixing plant. These will have high level alarms and pressure sensors to ensure that the silos are not over filled or over pressurised

3.3.5 Environmental Risk Managment

Noise control:

Cement Storage



during the delivery of cement. Air filters will also be maintained to prevent any unauthorized discharges of cement dust to air.

Cement will be delivered by tanker to the site and trained operators will ensure that the delivery of cement from the tanker to the silo is undertaken following correct procedures.

Several measures are proposed to be implemented at site in order to control the grout spillage:

- Washing of tools at each rod removal will occur on top of the spoil collection box with the mix of water and grout being directly pumped to the pit via the peristaltic pump.

- Installation of a permanent bunded wall around the jet grouting plant slab and installation of sump pit equipped with a permanent submersible pump within the bunded walls.

- Regular inspection of grouting lines.

- Fuse hose is to be installed on the grout line in order to control any leaks in case of over pressurization (hose burst). A fuse hose is a section of sacrificial hose which controls the location of a hose burst.

- Pre-drilling and pre-jet is to be used as a check control for potential grout spillage into the sea. As the system works in a close loop any loss of water will be quickly identified and investigated to confirm ay spillage into the sea or other location.

- A Spill Response Plan will be in place with trained staff to deal with the unlikely event of a grout spill.

It will take approximately 27 weeks per section for construction with key construction milestones detailed in the table below. Durations are based on one jet grouting rig and one pre-drilling rig per section. If two jet grout rigs are used, the timeframe for jet grouting execution will be less.

Section of work Princes Wharf Ferry Basin

Construction

Mobilisation Up to 4 Weeks Up to 4 weeks

Jet Grouting execution Up to 20 Weeks Up to 20 weeks

Demobilisation Up to 3 Weeks Up to 3 Weeks

Jet grout spillage control:

4. INDICATIVE PROGRAMME



Figure 11: Initial concept design for jet grouting

The Princes Wharf section of the seawall is approximately 105m long and runs through the road reserve adjacent to Princes Wharf in front of the ANZ building at 131-139 Quay Street.

Design of the jet grout columns is still to be finalised but the initial concept design, as shown in Figure 11, indicates that the layout will be a maximum of five rows of columns comprising 1.4m diameter columns, spaced at 1.2m centres north-south so that there is a 200mm overlap between the columns in that direction.

In the east-west direction, the columns are proposed to be spaced at 3.0m centres. While the alignment of the columns, number of rows, diameter of the columns and spacing may change with the final design, the overall size of the footprint of ground treated with jet grout columns is unlikely to be larger than shown.

Indicative Duration

Assuming 1 jet grouting rig & 1 gravity grouting rig

Up to 20 weeks for construction

Up to 7 weeks for mobilisation and demobilisation of site

Likely Plant Requirements Jet grouting rig: 1 or 2 rigs, depending on final quantity of jet grout columns

Pre-drilling (gravity grouting) rig: 1 rig

High pressure pump: 1 per rig

Mixing plant: 1 per rig

Cement silos: 1 vertical silo of 60 T or 2 horizontal silos of 30T per rig

Excavator: 1 per rig

Forklift: 1 per rig

Storage container: 1 per rig

Spoil pit: 3 to 8 containers per rig

Water storage: 1 tank per rig

Water treatment plant: 1 per rig

5. PRINCES WHARF SECTION

KEY INFORMATION



Likely Staff Requirements Supervisor x 1

Site engineer x 1

Rig operator: 1 per rig

Safety officer x 1

Welder x1

Mechanic x 1

Helpers: 2 per rig and 1 per jet grouting plant

Pump operator: 1 per rig

STMS x 2

Vehicle Movements

Assuming three rigs

(2 jet grouting & 1 gravity grouting)

Cement delivery: 2 to 6 movements per day

Spoil removal: 8-24 movements per day

Miscellaneous: 0-8 movements per day

Figures 12 and 13 shows the site layout and the phasing for the Princes Wharf section of works. Timber hoardings will be placed around all site boundaries with the site running from east to west. The site layout maintains three traffic lanes and a bi-directional cycle lane on Quay Street. Pedestrian access will be maintained along the northern side of Quay Street.

Two-way vehicle access would be maintained to Princes Wharf, providing one lane in and one lane out. This access would be alternated between the current entrance and exit lanes as jet grouting columns are to be installed in this location, as indicated in Figures 12 and 13. Princes Wharf access will be maintained on the western side during completion of the jet grouting phase 1 (Figure 12). Once phase 1 is completed, the working area will be adapted as per Figure 13 and a hose bridge (small protection structure) is to be installed on the road in order to protect the lines connected between the jet grout plant and the jet grouting rig during completion of phase 2.

Vehicle entrances to the site would be at either end of the works area. This would allow traffic to move through the site, entering from the western end and exiting from the eastern end. Appropriate traffic management would be required at each side of this work area. The traffic related to the jet grouting works would mainly be confined to cement delivery and spoil removal. Based on the location of the jet grout plant this access can be adapted to suit stakeholder requirements.

STAGING, SITE ACCESS, PEDESTRIAN AND TRAFFIC MANAGEMENT



Figure 12: Site layout phase 1

Figure 13: Site layout phase 2

The jet grouting duration is based on up to two columns per jet grout rig per day depending on the final design. In the event that two jet grout rigs are utilised, up to four columns per day could be constructed and this would reduce the duration.

The jet grouting columns will be constructed approximately 6m behind the existing seawall in the western section (Figure 14) and up to about 36m behind the seawall in the remaining section (Figure 15).

Figure 14: Western section Figure 15: Eastern section

JET GROUTING DURATION

CONSTRUCTION METHOD



On the western side, where basalt boulders may be encountered, works will be undertaken following both the gravity and jet grouting method, as described in Sections 3.3.1 and 3.3.4. However, where columns are about 36m landward of the existing seawall, the gravity grouting operation may not be required depending on the location of basalt boulders, and works will be undertaken as described above in Section 3.3.3 without pre-drilling.

At the end of each jet grouting column, the working area will be cleaned with a backhoe before setting up the rig on the next column.

In the event of any obstructions encountered during the jet grouting operation, the jet grouting rig will be moved away and then the pre-drilling rig can be used to overcome them. This is done by the pre-drilling rig drilling through the obstruction to allow jet grouting to continue

If the obstacle cannot be dealt with (e.g. steel, reinforced concrete or wood is encountered) contingency measures are to be agreed on a case by case basis and can include the addition of jet grout columns around the obstacle.

To provide context and size information, Appendix A includes pictures of plant similar to that likely to be used on this section of the works. An indicative jet grouting plant set up is shown above in Figures 12 and 13. The final location of the jet grouting plant will be determined following detailed design, however, it will be located within the construction zone of Princes Wharf section or Ferry Basin section. If the jet grouting plant is located on ground to be improved with jet grout columns, it will be relocated during the jet grouting operation in order to install columns located under the first location of the jet grouting plant area.

OBSTRUCTIONS

JET GROUTING PLANT



Figure 16: Initial concept design for jet grouting

The Ferry Basin section of the seawall runs along Quay Street in front of the current location of Piers 3 and 4, a distance of approximately 90m. Jet grouting columns are to be constructed landward of the existing seawall.

A new facing (up to approximately 500mm wide) of either shotcrete or concrete panels is proposed to be installed on the seaward side of the existing seawall. Ground anchors are proposed to be installed through a waler beam located on the new facing. The final number of ground anchors installed, if required, will be determined during detailed design. However, at this stage it is assumed that anchors will be required approximately every 3m on a 45-degree angle back into the existing ground. Finally, a rock toe for scour protection will be installed at the toe of the new seawall facing. Preliminary design for the Ferry Basin section is outlined in Figure 17 below.

Design of jet grouting is still to be finalised but the initial concept design, as shown in figure 16 indicates that the layout will be five rows of columns comprising 1.4m diameter columns, spaced at 1.2m centres north-south so that there is 200mm overlap between the columns in that direction. In the east-west direction the columns are proposed to be spaced at 3.0m centres. While the alignment of the columns, number of rows, diameter of the columns and spacing may change with the final design, the overall footprint of ground treated with jet grout columns is unlikely to alter significantly.

Figure 17: Ferry Basin design section

6. FERRY BASIN SECTION



Indicative Duration Up to 20 weeks for construction

Up to 7 weeks for mobilisation and demobilisation of site

Likely Plant Requirements Jet grouting rig: 1 or 2 rigs, depending on final quantity of jet grout columns

Pre-drilling (gravity grouting) rig: 1 rig

High pressure pump: 1 per rig

Mixing plant: 1 per rig

Cement silos: 1 vertical silo of 60 T or 2 horizontal silos of 30T per rig

Excavator: 1 per rig

Forklift: 1 per rig

Storage container: 1 per rig

Spoil pit: 3 to 8 containers per rig

Water storage: 1 tank per rig

Water treatment plant: 1 per rig

Likely Staff Requirements Supervisor x 1

Site engineer x 1

Rig operator: 1 per rig

Safety officer x 1

Welder x 1

Mechanic x 1

Helpers: 2 per rig and 1 per jet grouting plant

Pump operator: 1 per rig

STMS x 2

Vehicle Movements

Assuming three rigs

(2 jet grouting & 1 gravity grouting)

Cement delivery: 2 to 6 movements per day

Spoil removal: 8-24 movements per day

Miscellaneous: 0-8 movements per day

Figure 18 shows the site layout for the Ferry Basin section of works. Timber hoarding will be placed around all the site boundaries with the site running from the end of the jet grouting in Princes Wharf to the Ferry Building.

There are three possible construction scenarios for the proposed upgrade of the Ferry Basin seawall section:

KEY INFORMATION

STAGING, SITE ACCESS, PEDESTRIAN AND TRAFFIC MANAGEMENT



• Scenario 1: Piers 3 and 4 remain in their current form, with ferries continuing to use thesestructures during construction;

• Scenario 2: Piers 3 and 4 have been previously deconstructed as part of a separate project, andferries utilising Piers 3 and 4 relocated away from the works area; or

• Scenario 3: some of Piers 3 and 4 have been deconstructed as part of a separate project, butsome of Piers 3 and 4 remain in their current form. Ferries continue to use the piers that remain.

Scenario 1: Piers 3 and 4 remain in their current form, with ferries continuing to use thesestructures during construction

During the construction of Jet grout columns public access will be maintained largely in its

current form. Subsequently the works in the coastal marine area will be undertaken.This phase involves closing public access to most of the wharf area in the Ferry Basin, while maintaining access to ferry services on Piers 3 and 4.

In order to construct the anchors, waler beam and facing temporary light structure supported byexisting seawall structure will be put in place In addition, a slot up to 5 m wide will bedeconstructed in the deck of the existing wharf structure immediately adjacent to the existingseawall to allow construction of the coastal marine works. The wharf and public space will bereinstated at the completion of the works under Scenario 1.

Scenario 2: Piers 3 and 4 have been previously deconstructed as part of a separate project,and ferries utilising Piers 3 and 4 relocated away from the works area

The prior removal of Piers 3 and 4 would allow the wharf structure to be deconstructed up to theexisting seawall, thus enabling working space and laydown area to be provided in the CMA onone or more barges as an option for the CMA works. Some landside working would also occurfor this seaward construction option, such as access for concrete trucks and other materialdeliveries.

The seaward method assumes all the existing wharf has been removed. Alternatively,construction under Scenario 2 may be undertaken entirely from land, with the exception of thetemporary light structure as described for Scenario 1 above. Scenario 2 could be constructedfrom the landward side regardless of whether the wharf structure has been removed or not. Thewharf will be reinstated as part of a separate project under Scenario 2.

Scenario 3: Some of Piers 3 and 4 have been deconstructed as part of a separate project,but some of Piers 3 and 4 remain in their current form. Ferries continue to use the piersthat remain

This scenario is a combination of Scenarios 1 and 2, whereby some of Piers 3 and 4 have beendeconstructed but others remain. This would enable the area of wharf adjacent to thedeconstructed piers to be removed (as may occur for Scenario 2), with the area of wharf adjacentto the operational piers remaining (as for Scenario 1). Construction may be undertaken from boththe landward and seaward side of the seawall.

For each of these scenarios, pedestrians may be diverted along the southern side of Quay Street,and three traffic lanes (including bus lane) and a bi-directional cycleway on Quay Street

The landward option would involve having site entrances and exits at either end of the project,allowing trucks to enter and exit at either end. Dependent on which location is used, the truckswould need to reverse into or out of the site, being marshalled by traffic controllers. Due to thewidth of the site, there is insufficient space for through traffic.

Construction in this area may require the western kiosk and eastern kiosk to be relocated. It isunderstood that tree 18 will remain in place throughout the works. This will require protection andpruning to minimise its impact on the works. All other trees in this area will be relocated. Accessto the shops at 131 Quay Street will be maintained.

Three traffic lanes and a bi-directional cycle lane would be maintained on Quay Street.

Vehicle entrances to the site would be at either end of the works area. This would allow traffic to move through the site, entering from the western end and exiting from the eastern end. Appropriate traffic management would be required at each site access of this work area. The



traffic related to the jet grouting works would mainly be confined to cement delivery and spoil removal. Based on the location of the jet grout plant this access can be adapted to suit stakeholder requirements.

Figure 18: Site layout

As per Princes Wharf section, basalt boulders may be encountered in the Ferry Basin section. Due to the location of the columns, works will be undertaken following both the gravity and jet grouting method, as described in Sections 3.3.1 and 3.3.4.

At the end of each jet grouting column, the working area will be cleaned with a backhoe before setting up the rig on the next column.

In the event of any obstructions encountered during the jet grouting operation, the jet grouting rig will be moved away and then the pre-drilling rig can be used to overcome them. This is done by the pre-drilling rig drilling through the obstruction to allow jet grouting to continue

If the obstacle cannot be dealt with (e.g. steel, reinforced concrete or wood is encountered) contingency measures are to be agreed on a case by case basis and can include the addition of jet grout columns around the obstacle.

To provide context and size information, Appendix B includes pictures of plant similar to that likely to be used on this section of the works. An indicative jet grouting plant set up is shown above in Figure 18. The final location of the jet grouting plant will be determined following detailed design, however it will be located within the construction zone of Princes Wharf section or Ferry Basin section. If the jet grouting plant is located on ground to be improved with jet grout columns, it will be relocated once during the jet grouting operation in order to install columns located under the first location of the jet grouting plant area.

JET GROUTING DURATION

The jet grouting duration is based on up to two columns per rig per day depending on the final design. In the event that two jet grout rigs are utilised, up to four columns per day could be constructed and this would reduce the duration.

CONSTRUCTION METHOD

OBSTRUCTIONS

JET GROUTING PLANT



A new facing for the existing seawall is required for this section of work. Either concrete panels or shotcrete are proposed:

- Concrete panels: Concrete panels will be installed one at a time. Installation will likely be using a crane to pick up precast panel from the delivery truck or preferably from lay down area / stockpile of previously delivered panels. Divers will likely be required to monitor the precast panel being lowered into position. The top of precast panel installed will require worker access or potentially divers to release the lifting device.

- Shotcrete: For the bottom part (generally below mid tide level) of the facing, divers may be required to complete the works using specific concrete (shown in figure 19 as special concrete) for works done under water. For the upper part (generally above the mid tide level), facing works are to be done from platforms as shown in Figure 19, directly installed on the existing deck structure if still in place. If the existing deck structure is already removed, a temporary platform propped from the land side (supported by the existing seawall) will be installed to execute work at low tide. In both scenarios, the platform will be equipped with a specific device to capture any water or solids discharged during the shotcrete operation. Shotcrete is to be used to construct the new seawall facing. Prior to the shotcrete operation, the existing seawall is to be cleaned (Hydroblasting, and removing concrete by hand tools) , then the wire mesh will be fixed on the existing seawall keeping a sufficient concrete cover between the mesh and the existing seawall. The shotcrete is applied in various layers to meet the required thickness of the new facing. All equipment will be located on the existing footpath of the Ferry Basin section, or over temporary platforms.

-

Figure 19: Platform for shotcrete

SEAWALL FACING



A waler beam is proposed on the face of the existing seawall to allow anchors to be constructed through the seawall. The waler beam will require false works or similar, that may utilise the existing wharf structure or temporary propping from the sea floor or the existing seawall.

A working platform with safety fencing will be required.

The waler beam will be constructed using falsework or similar to support the soffit and allow the subsequent placement of reinforcement, side shutters and concrete. The falsework may include a working platform for access and reinforcement may be partially prefabricated for ease of installation. Concrete will be placed using a pump.

Ground anchors are proposed to be installed through a waler beam located on the new seawall facing on about a 45-degree angle and cored through the facing and the seawall so that they are embedded approximately 6m into the East Coast Bays Formation (ECBF) rock. This gives an anchor length of up to about 25m. Productivity of 1 or 2 anchors per day is assumed.

The coring and drilling period of the anchors will likely be around 5 hours per anchor.

Environmental controls will need to be in place for grouting of the anchors and if water is used for the drilling a method of collecting and treating this will be required. To reduce the risk of environmental contamination it is recommended that the existing wharf remains in place to act as a deck to retain any materials on site. If the existing wharf is not in place, a temporary platform or similar, can be used to retain materials. This will be determined following detailed design.

Anchors will likely be installed from the land side using a drilling rig (the same as used for gravity grouting).

Upon completion of the seawall facing and ground anchors, scour protection will be placed at the toe of the new facing. Either a rock protecting toe or a concrete mattress are proposed:

- Rock protecting toe: This will consist of an underlayer and primary rock armour layer, both overlying a geotextile filter fabric. This will likely be placed with long reach excavators (as required) from either the landside or from a barge, depending on the area requiring reinstatement;

- Concrete mattress: A concrete mattress is shown in Figure 20 below. Mattress panels are premade in rolls, which are lifted down into the sea using an excavator or a crane. The concrete mattress is formed by divers rolling out the geosynthetic mattress fabric underwater. This is zipped together and pump filled with flowable, small aggregate concrete.

Figure 20: Concrete mattress opened after 20 days into sea

WALER BEAM

GROUND ANCHORS

SCOUR PROTECTION



Appendix A Jet grouting equipment

Appendix B Staging Drawings

7. APPENDICES



APPENDIX A – JET GROUTING EQUIPMENT



Figure 1. Jet grouting rig with long mast equipped (24m in height), Vertical silos (16m in height)

Figure 2. High pressure pump



Figure 3. Mixing plant with horizontal silos (7.5m in height)



Figure 4. Container for spoil (pit)

Figure 5. Precast of prefab spoil pit



1 - Princes Wharf Stage 1 2 - Princes Wharf Stage 2 3 – Ferry Basin

APPENDIX B – STAGING DRAWINGS

QUAY STREET SEAWALL UPGRADE - Auckland Council · The alternative seawall upgrade proposed...

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