Groundwater and settlement monitoring and contingency plan- Canopy removal and utilities division

Auckland City Rail Link In association with:

ENABLING WORKS CONTRACT 2 GROUNDWATER AND SETTLEMENT MONITORING AND CONTINGENCY PLAN Separable Portion 3 – Canopy Removal and Utilities Diversion Revision: 1 FINAL 9 February 2018

COMMERCIAL IN CONFIDENCE

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Connectus Project #: 2719 Client: CRLL

Groundwater and Settlement Monitoring and Contingency Plan SP3 Revision: 1, Date: 9 February 2018

Table of Contents

.................................................................................................. 3 Document information ............................................................................................................................. 3 Revision History ....................................................................................................................................... 3 Glossary of Terms ................................................................................................................................... 7 1

Introduction ............................................................................................................................ 8 1.1

Scope

1.2

Purpose of Groundwater and Settlement Monitoring and Contingency Plan

10

1.2.1

Objectives of the GSMCP

10

1.2.2

Performance Standards during Construction

10

1.2.3

Predicted Performance

11

1.3

GSMCP Authors

11

1.4

Consent Requirements

12

2

Project Description .............................................................................................................. 15 2.1

3

4

8

Summary of Construction Methodology

15

2.1.1

Canopy removal along the western side of Albert Street (between Victoria St and Wellesley St) 15

2.1.2

Trench excavation, ground support and spoil handling

15

2.1.3

Relocate/install/abandon underground utilities

15

2.1.4

Trench backfilling

15

Existing Environment ........................................................................................................... 16 3.1

Land Use and Topography

16

3.2

Geology

16

3.3

Hydrogeology

16

3.3.1

Groundwater System

17

3.3.2

Groundwater levels

17

3.3.3

Groundwater Flow Direction

17

3.4

Existing Buildings and Structures

18

3.5

Existing Basements

18

3.6

Existing Utilities

18

Overview of Monitoring & Reporting Requirements ............................................................ 19 Page 4

Connectus Project #: 2719 Client: CRLL

Groundwater and Settlement Monitoring and Contingency Plan SP3 Revision: 1, Date: 9 February 2018

4.1

Construction Stages

19

4.2

Notification and GSMCP Certification

19

4.3

Data Collection and Reporting Requirements

20

4.4

Independent Building Assessor (IBA) Reporting Requirements

20

4.5

Roles and Responsibilities

23

5

Groundwater Monitoring Plan .............................................................................................. 25

6

Settlement Monitoring Plan ................................................................................................. 25 6.1

Introduction

25

6.2

Building Condition Surveys

25

6.2.1

Building Monitoring Locations

25

6.2.2

Building Condition Surveys and Visual Inspections

26

6.2.3

Pre-construction Surveys

26

6.2.4

During-Construction Surveys

26

6.2.5

Post-Construction Surveys

27

6.3

6.4

6.5 7

Monitoring Ground, Buildings

27

6.3.1

Ground Survey and Building Monitoring Locations

27

6.3.2

Pre-construction Settlement Monitoring

27

6.3.3

During-Construction Settlement Monitoring

27

6.3.4

Post-Construction Settlement Monitoring

27

Utilities and Infrastructure Monitoring

28

6.4.1

Pre-Construction

28

6.4.2

During Construction

28

6.4.3

Post Construction

28

Settlement Trigger Levels

28

Response, Mitigation and Contingency Plan....................................................................... 29 7.1

Introduction

29

7.2

Response to Alerts

29

7.2.1

29

Settlement Alerts

7.3

Response to Alarms

30

7.4

Response to Building Damage

30

7.5

Mitigation Options

31

7.5.1

Design Validation

31

7.5.2

Mitigation of Effects

31

7.5.3

Contingency Measures

31

8

Monitoring and Contingency Plan Review ........................................................................... 32 8.1

General Review of the GSCMP

32 Page 5

Connectus Project #: 2719 Client: CRLL

8.2

Groundwater and Settlement Monitoring and Contingency Plan SP3 Revision: 1, Date: 9 February 2018

Review of Monitoring and Contingency Requirements

32

Appendix A: Drawings .......................................................................................................................... 34 Instrumentation Monitoring Network Plans

34

Appendix B: Settlement Trigger Levels ................................................................................................ 36 Appendix C: Assessment of settlement effects ..................................................................................... 40

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Connectus Project #: 2719 Client: CRLL

Groundwater and Settlement Monitoring and Contingency Plan SP3 Revision: 1, Date: 9 February 2018

GLOSSARY OF TERMS Term

Definition

AC

Auckland Council

AT

Auckland Transport

ATS

Automatic Total Station

BCS

Building Condition Survey

CBD

Central Business District

CEMP

Construction Environmental Management Plan

CEP

Construction Execution Plan

CPEng

Chartered Professional Engineer

CRL

City Rail Link

CRLL

City Rail Link Ltd

CSA

Construction Support Area

ECBF

East Coast Bays Formation

EMS

Environment & Sustainability Manager

GNS

Geological and Nuclear Sciences

GSMCP

Groundwater and Settlement Monitoring and Contingency Plan

IBA

Independent Building Assessor

LQS

Lower Queen Street

m RL

Metres reduced level

TG

Tauranga Group

QE2S

Queen Elizabeth II Square

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Connectus Project #: 2719 Client: CRLL

Groundwater and Settlement Monitoring and Contingency Plan SP3 Revision: 1, Date: 9 February 2018

1 INTRODUCTION 1.1

SCOPE

The City Rail Link (CRL) project comprises the construction, operation and maintenance of a 3.4 km underground passenger railway, running between Britomart Station and the North Auckland Rail Line in the vicinity of Mt Eden station.

This Groundwater and Settlement Monitoring and Contingency Plan (GSMCP) relates to CRL Contract 2 Separable Portion 3 (SP3; the Project) which involves the removal of existing building canopies from four buildings and diversion of underground utilities within the Albert Street road corridor from Victoria Street West to Wellesley Street West. The Project includes trenching and is expected to take 12 months to complete.

Figure 1 outlines the extent of works for the Project.

This project is being delivered by Connectus, a joint venture of McConnell Dowell Constructors Limited and Downer New Zealand Limited. The GSMCP has been prepared by AECOM New Zealand Limited (AECOM) for Connectus and forms part of the Construction Environmental Management Plan (CEMP) for the Project.

The relevant resource consent for the GSMCP is Water Permit R/REG/2016/1892 for the Take and Diversion of Groundwater (the Consent).

The Consent will expire 35 years after the consent commences unless it has been surrendered or been cancelled at an earlier date.

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Connectus Project #: 2719 Client: CRLL

Groundwater and Settlement Monitoring and Contingency Plan SP3 Revision: 1, Date: 9 February 2018

Figure 1 Extent of Project Works

From PTA (26 May 2017).

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Connectus Project #: 2719 Client: CRLL

1.2

Groundwater and Settlement Monitoring and Contingency Plan SP3 Revision: 1, Date: 9 February 2018

PURPOSE OF GROUNDWATER AND SETTLEMENT MONITORING AND CONTINGENCY PLAN

1.2.1

Objectives of the GSMCP

The objectives of the GSMCP are to: a) So far as reasonably practical, avoid any damage that affects serviceability of structures and services; and b) To remedy or mitigate any adverse effects (including cumulative effects) associated with dewatering/excavation and excavation activities required for the CRL tunnel construction.

This GSMCP, prepared in general accordance with Conditions 82 to 129 of the Consent described below (Section 1.4), outlines the Project requirements for: 

The monitoring of groundwater and settlement effects outlined in the Assessment of Environmental Effects (AEE) report;



A framework for developing monitoring and mitigation procedures to minimise the effects of settlement on existing structures;



Building condition survey review.

The GSMCP is required to be certified by Auckland Council (AC) at least 20 working days prior to the commencement of dewatering/excavation. No dewatering/excavation on the subject site shall commence until certification from AC is provided.

This GSMCP may be varied (including the frequency of monitoring), subject to certification of the variation by AC, and shall be implemented for the periods specified in the Consent.

1.2.2

Performance Standards during Construction

Further to the objectives of the GSMCP as described above, the following performance standards are specified within the Consent: Within the 5mm settlement contours on the drawings in Appendix 1, all excavations, dewatering systems, retaining structures and associated works (including backfilling) for the CRL construction must be designed, constructed and maintained so as to avoid any damage that exceeds the Serviceability Limits of buildings, structures and services.

Beyond the 5mm settlement contours on the drawings in Appendix 1, the Consent Holder must ensure that the damage to masonry buildings due to the Project works, including excavations, dewatering systems, retaining structures and associated works (including backfilling), does not exceed the “negligible” category extent detailed in Table 1 below and has only negligible effects on piled buildings, structures and services.

The predicted settlement and building assessment is included in Appendix C.

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Connectus Project #: 2719 Client: CRLL

Table 1 Overview of the Burland Scale

1.2.3

Groundwater and Settlement Monitoring and Contingency Plan SP3 Revision: 1, Date: 9 February 2018 1

Predicted Performance

These performance standards will be achieved through the design of the Project, and the effects of dewatering/excavation will be mitigated through the procedures and actions provided in Sections 5, 6, and 7 of this GSMCP. During the detailed design of the Project the predicted effects of settlement arising from the final ground support design have been assessed and are documented in Assessment of Settlement Effects attached as Appendix C. Based on this assessment damage to buildings from the Project is predicted to fall within the “Negligible” damage classification.

1.3

GSMCP AUTHORS

This GSMCP has been prepared under the direction of a senior qualified person (Geotechnical Professional), Kevin Anderson BEng(Hons) CPEng. Kevin is an Associate Director – Geotechnical at AECOM. He has a Bachelor degree in Civil Engineering, is a Chartered Professional Engineer and has over 21 years’ experience in geotechnical assessment including considerable experience in undertaking, managing, and reporting on geotechnical investigations for public and private sector clients.

1

Burland J B (1997), Assessment of risk of damage to buildings due to tunneling and excavation, Earthquake Geotechnical Engineer ing, Ishihara (ed), Balkema, Rotterdam, pp. 1189-1201.

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Connectus Project #: 2719 Client: CRLL

1.4

Groundwater and Settlement Monitoring and Contingency Plan SP3 Revision: 1, Date: 9 February 2018

CONSENT REQUIREMENTS

Table 2 outlines the resource consent conditions specific to the GSMCP for Water Permit R/REG/2016/1892 and how these are addressed within this GSMCP.

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Connectus Project #: 2719 Client: CRLL

Groundwater and Settlement Monitoring and Contingency Plan SP3 Revision: 1, Date: 9 February 2018

Table 2 GSMCP conditions for Water Permit R/REG/2016/1892 and the relevant sections of this document

Consent Condition Consent Duration

82 83

Performance Standards 84

Brief Condition Description

Section Addressed in

The dewatering and diversion consent and water permit 46500 shall expire 35 years after the consent commences.

Section 1

All excavation and associated works shall be designed, constructed and maintained to avoid any damage that affects serviceability of structures and services.

Section 1.2.2

Beyond the 5mm settlement contour, damage to buildings from the Project shall not exceed “negligible damage” category extent (Burland, 1995) beyond the predicted settlement values.

Section 1.2.2, Appendix C

96 97

Section 1.2.1 and 4.2 GSMCP requirements for certification by AC (timeframes and peer review)

Section 4.2

98 99

Section 1.2.1 and 4.2 Dewatering is not to commence until certification from the Manager is provided.

Section 5

The GSMCP, required by Condition 97, shall include the requirements of the Consent including, but not limited to, the following: a. an “as built” survey plan of all monitoring locations

Section 1, 6.2.1 and 6.3.1, Appendix A Section 3 (Existing Environment)

b. full details of the existing groundwater environment, surveys and monitoring required by the Consent Groundwater and Settlement Monitoring and Contingency Plan ("GSMCP")

Section 4 (Overview of Monitoring and Reporting Requirements) Section 6 (Settlement Monitoring Plan)

100

c. details on the timing and frequency of the required surveys and monitoring relative to the commencement of dewatering/excavation and the completion of dewatering/excavation;

Relevant details are outlined in: Section 4.1 and Table 3

d. details outlining the effects on groundwater

Section 5

e. alert and alarm triggers for each ground and building deformation mark

Section 6, Appendix B

f. details of contingency measures to be implemented if alert or alarm triggers are exceeded including a Response Plan.

Section 7

g. identification of any adjacent services susceptible to damage and details of any pre and post construction monitoring or inspection;

Section 6.4

i. details of monitoring proposed to be at all adjacent buildings against cumulative settlement effects;

Section 1, 6.2.1 and 6.3.1, Appendix A

j. identification of, and monitoring of, existing basements which could be subject to potential flooding from post-construction groundwater mounding.

Section 3.5

k. review of the proposed monitoring frequency, and alarm and alert trigger levels in Appendix B (following the construction building condition surveys required by Condition 109) to confirm they are appropriately set to ensure the “slight” damage category will not be breached.

Section 8.2

101

The GSMCP may be varied, including frequency of monitoring, subject to the certification by AC.

Section 1.2.1 and 8

102

Once certified, the GSMCP shall be implemented for the periods specified in the conditions of the Consent.

Section 1.2.1

103

The Consent Holder shall advise the Manager, in writing, of the date of the proposed Commencement of Dewatering.

Prior to the commencement of dewatering/excavation, the Consent Holder shall employ an independent senior qualified person to undertake a detailed pre-construction condition survey, of all buildings specified in Section 6.2.1 to confirm their existing condition, subject to the approval of the property owner. The survey shall include, but not be limited to, the following: a. any information about the type of foundations; b. existing levels of damage considered to be of an aesthetic or superficial nature;

Building Inspection

c. existing levels of damage considered to affect the serviceability of the building where visually apparent and without recourse to intrusive or destructive investigation; 109

d. a professional opinion as to whether observed damage may or may not be associated with actual structural damage; e. susceptibility of the building or structure to further movement; f. specific assessment of building damage from the predicted total settlement shown in Appendix C and with reference to the trigger levels identified in Appendix B; g. review of proposed alarm and alert trigger levels to confirm they are appropriately set and movement less than trigger levels set will not exacerbate damage, and whether the monitoring frequency and locations of monitoring points are adequate; and h. photographic evidence of (b) and (c).

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Section 6.2

Connectus Project #: 2719 Client: CRLL

Groundwater and Settlement Monitoring and Contingency Plan SP3 Revision: 1, Date: 9 February 2018

Consent Condition 110

111

Brief Condition Description

Section Addressed in

The processes required should access to a property owned by a third party be declined (or unreasonable terms imposed) to undertake monitoring, surveys or inspections

Section 6.2.3

Any condition survey undertaken in accordance with Condition 109, or any other condition surveys undertaken by the Consent Holder, shall be undertaken as follows:

Section 6.2

a. The senior qualified person shall be identified in the CEMP (required by Condition 36); b. Contact owners of those buildings and structures where a condition survey is to be undertaken to confirm the timing and methodology for undertaking a pre-construction condition survey; c. Record all contact, correspondence and communication with owners and this shall be available on request for the Council; d. Provide the building condition survey or structure condition survey report to the relevant property owner and the Council within 15 working days of the survey being undertaken; e. Undertake a visual inspection during construction if requested by the building or structure owner where a pre-construction condition survey has been undertaken; f. Develop a system of monitoring the condition of existing buildings or structures which is commensurate with the type of the existing building or structure and the proximity of the project works in order to assess whether or not construction activities are compromising the structural integrity of the building or structure.

Building Inspection 112

Should the pre-construction building condition survey and assessment highlight greater sensitivity of buildings than envisaged by the application, then implement additional measures.

Section 6.2

113

Carry out a visual inspection of the ground and external building facades of the listed buildings to monitor any deterioration or movement of any deterioration or movement of any preexisting cracks.

Section 6.2.4

114

Keep a record of the time, date and any observations for each inspection

115

Timing of post-construction building condition survey. Survey to cover the matters identified in Condition 111.

116

Additional building condition surveys at the request of AC.

117

Subject to Condition 125, the requirement for any such condition survey will cease 6 months after the Completion of Construction, unless the requirements of Condition 115 have not been met and subject to a consistent pattern of deformation records having been obtained in this period in which no evidence of adverse effects is apparent.

Section 6.2.5 Section 7

Establishment and maintenance of a settlement monitoring network (ground settlement and building movement monitoring marks) to detect any deformation: a. The minimum scope of settlement monitoring Ground Surface and Building Monitoring

119

b. Subject to the owners’ approval, at least two sets of building movement monitoring marks shall be located on each building c. The final location and number of building movement monitoring marks shall take into account the building type and size, accessibility to survey the marks and risk of damage from ground settlement and the effects of differential settlement from the predicted settlement values.

120

Monitoring frequency and duration, and baseline monitoring records.

Section 6 Appendix A

Section 6.3, Table 4

In response to the event of any Alert or Alarm trigger level exceedance (ground surface, building and/or groundwater levels**) the following shall occur: a. Notify AC and the IBA within 24 hours; b & c. If alert values are exceeded, a senior qualified person shall assess the works constructed up to that time and provide a report to AC within one week. Measures (if any) to be implemented are to be as identified in the GSMCP. d. If alarm values are exceeded, the process outlined in Condition 124b shall be undertaken. The report shall also include any recommendations for remedial actions if required in order to complete construction. These recommendations shall be implemented prior to recommencing works.

Section 7.2.2

e. Where alarm levels are exceeded, remedial recommendations and actions of the IBA may also be considered. This shall be implemented, unless the building owner(s) request in writing that the construction works are to be completed in accordance with the report prepared under Condition 124d.

Section 7.3

125

The required response and repairs should any damage to buildings, structures or services be caused wholly or in part by the exercising of the Consent

Section 7.4

126

AC shall be advised in writing within ten working days of Completion of Dewatering.

Section 4.2

127

AC shall be advised in writing within ten working days of Completion of Construction.

Section 4.2

128

Compilation, comparison and submission frequency to AC of all data collected during the monitoring programme.

Section 4.3

129

The conditions of the Consent may be reviewed by AC

Section 8

124 Contingency

Reporting

Review Condition - Water Permit R/REG/2016/1892

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Figure 8

Connectus Project #: 2719 Client: CRLL

Groundwater and Settlement Monitoring and Contingency Plan SP3 Revision: 1, Date: 9 February 2018

2 PROJECT DESCRIPTION This section presents a summary of the Project works that relate to the matters required to be addressed by the GSMCP. A detailed description of the construction methodology is provided in the Project CEMP. The relevant construction period for this GSMCP occurs from the time that dewatering/excavation commences (Section 2.1)

2.1

SUMMARY OF CONSTRUCTION METHODOLOGY

The Project involves excavating a trench along Albert Street, between Wellesley and Victoria Street, to relocate underground services. This will simplify the future construction of the proposed Aotea train station. The excavation for the Project (i.e. SP3) is approximately 200m long, 4m deep and 1.5m wide.

To complete the excavation, overhanging canopies attached to the adjacent buildings will be amended.

Generally, the Project works undertaken will consist of: 1.

Canopy removal along the western side of Albert Street (between Victoria Street and Wellesley Street)

2.

Trench excavation, ground support and spoil handling

3.

Relocate/install/abandon underground utilities

4.

Backfill the trench and reinstatement the road pavement.

2.1.1

Canopy removal along the western side of Albert Street (between Victoria St and Wellesley St)

The initial stage of construction for the Project involves the removal of canopies. Figure 1 shows the location and staging of the canopy removal.

2.1.2

Trench excavation, ground support and spoil handling

The trench will be approximately 4m deep, 1.5m wide and 200m long. It will predominantly be within well compacted fill overlying stiff Tauranga Group alluvium. The ground support for the trench will be a proprietary system providing positive ground support.

2.1.3

Relocate/install/abandon underground utilities

Network utility operators that will be affected by the works include Vector Electricity and Communications, Vector Gas, Chorus, Auckland Council, Watercare and Vodafone. The method of relocating, protecting and supporting each utility has been developed in consultation with the relevant utility operator and depends on the type of utility and its location.

2.1.4

Trench backfilling

The trench backfill will be placed progressively as the utility works are completed and the temporary ground support removed. The pavement will then be reinstated.

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Connectus Project #: 2719 Client: CRLL

Groundwater and Settlement Monitoring and Contingency Plan SP3 Revision: 1, Date: 9 February 2018

3 EXISTING ENVIRONMENT 3.1

LAND USE AND TOPOGRAPHY

The Wellesley to Victoria Street section of the Project is situated in the Auckland Central Business District (CBD). The CBD is a high density built-up urban environment and New Zealand’s largest city centre, with no natural ground surface evident. Current land uses above ground along the Project alignment include high density commercial and office buildings, residential and visitor accommodation, retail, restaurants and bars. Numerous underground services (utilities) are present within the CBD and Project Area.

The topography of the CBD is characterised by ridges and valleys and has a gentle sloping topography, dropping from south to north towards the coast. Intersecting streets strike east-west down the valley slopes to Queen Street (e.g. Victoria and Wellesley Streets) and are steep relative to Albert Street.

3.2

GEOLOGY

Geological and Nuclear Sciences (GNS) has published a 1:50,000-scale geological map of the 2 Auckland urban area . The general vertical stratigraphic sequence comprises the following, in chronological order (oldest to youngest): 

East Coast Bays Formation (ECBF): is present at depth, which forms the local basement rock.

The ECBF is characterised by alternating sandstone and siltstone beds with a completely weathered (residual soil) upper surface. The unweathered rock is fractured to a varying degree.



Tauranga Group Sediments (TG): alluvial and marine sediments comprising peat, mud, silt, sand and gravel, which unconformably overlie the ECBF. These are present as unconsolidated sediments that are frequently interlayered and may form discrete lenses at some locations.



Albert Park Volcanics: Basalt and scoria produced from Albert Park Volcano form considerable thicknesses within the CBD, particularly on the eastern side of Queen Street, into the Queen Street Valley. Volcanic ash deposits of variable thicknesses are present at discrete locations overlying the Tauranga Group and ECBF throughout the Project area.



Fill: asphalt or concrete pavement forms the ground surface and is underlain by granular base coarse, sub-base and/or variable fill materials. Fill materials may comprise re-worked natural soils (silts, sands and gravels) or waste materials such as ash, clinker and demolition rubble.

The thickness of each unit varies across the Project area. Site specific geology has been determined from boreholes and other site investigations in the vicinity of the Project and has been documented in factual and interpretive reports.

3.3

HYDROGEOLOGY

Key aspects of the hydrogeology are summarised here.

2

Kermode, L. O. 1992: Geology of the Auckland urban area. Scale 1:50 000. Institute of Geological & Nuclear Sciences Geological Map 2. Lower Hutt, New Zealand, Institute of Geological & Nuclear Sciences Ltd. 1 sheet + 63 p.

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Connectus Project #: 2719 Client: CRLL

3.3.1

Groundwater and Settlement Monitoring and Contingency Plan SP3 Revision: 1, Date: 9 February 2018

Groundwater System

Two key groundwater systems have been identified for the Project: Shallow perched system - within the Tauranga Group sediments, upper weathered ECBF and local volcanic ash/fill materials. This system comprises numerous perched and isolated water tables, supported by lenses of low permeability materials and the weathered ECBF. Areas of saturation are expected to be laterally discontinuous.

Deeper (regional) groundwater system – within the ECBF this aquifer underlies the shallow perched groundwater system and is a continuous zone of saturation. In areas of higher topography, some perching on discrete mudstone layers may be present within the ECBF. Seasonal groundwater level variations are likely to be less pronounced within the regional groundwater system than for the upper perched units, with water level records indicating a delayed response to rainfall.

Groundwater flow in both systems is generally in a northerly direction toward the Waitemata Harbour.

Locally, groundwater flow is interpreted to be influenced by topography, promoting flow to the northeast toward the Queen Street Valley.

Buildings along this part of the alignment that have drainage systems all report little if any discharge.

3.3.2

Groundwater levels

Groundwater Levels within the shallow perched aquifer and regional ECBF are described below: Perched groundwater - water levels in the Tauranga Group and volcanic deposits near Victoria Street have been recorded at approximately 15 m RL. Significant water level responses occur in the perched units after rainfall events, with about 0.4 m increase in water level following a rainfall event. Seasonal groundwater level variations are likely to be about 2.0m.

Where encountered, perched groundwater heads in the shallow system of 1 to 2 metres have been recorded, with this expected to be variable as a function of material heterogeneity and presence of services/basements which act to drain the shallow groundwater. The perched water tables are associated with more permeable lenses and are not laterally continuous, and this restricts the volumes of water contained in these units and the lateral migration of water in comparison to the regional aquifer below.

Regional ECBF Aquifer- groundwater levels within the regional system are approximately 5 m lower than levels in the overlying perched system. The following regional ECBF water levels have been measured and are subject to seasonal variation: 

Victoria Street – between approx. 6 and 8 m RL (16 – 19 m depth).



Wellesley Street – approx. 10 m RL (15 m depth)

Seasonal groundwater level variations are likely to be less pronounced than for the upper perched units, with water level records indicating a delayed response to rainfall.

3.3.3

Groundwater Flow Direction

Groundwater generally follows a subdued expression of topography. However, localised differences between shallow perched groundwater and the deeper regional flow area are expected as follows: Perched groundwater – variable groundwater flow is expected within the shallow perched system as a function of material heterogeneity, the influence of drainage to service trenches/basements and the palaeotopography of the ECBF. A component of water flowing in the perched system will recharge the underlying regional aquifer. The perched groundwater regime is complex and has already been extensively modified from its natural condition by the extensive building development, filling and existing utilities acting as drains and connections between lenses.

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Connectus Project #: 2719 Client: CRLL

Groundwater and Settlement Monitoring and Contingency Plan SP3 Revision: 1, Date: 9 February 2018

Regional ECBF Aquifer –groundwater flow in the regional aquifer is generally in a northerly direction toward the Waitemata Harbour. Locally, groundwater flow is interpreted to be influenced by topography, promoting flow to the northeast toward the Queen Street Valley.

3.4

EXISTING BUILDINGS AND STRUCTURES

The types of buildings encountered along and adjacent to the Albert Street section (between Victoria and Wellesley Street) are multi-storey piled structures that are used for a mix of residential, entertainment, commercial and retail.

The following buildings are of interest and have had individual settlement assessments and building condition surveys. These are: 

Auckland Council Tower – 135 Albert Street



SKYCITY Convention Centre – 109 – 125 Albert Street



Manhattan Apartments – 101 – 107 Albert Street



AA Centre – 99 Albert Street

3.5

EXISTING BASEMENTS

The following list outlines the basements present adjacent to the excavation: 

Auckland Council Building – 4 levels



SKYCITY Convention Centre – 4 levels



Manhattan Apartments – 1 level



AA Centre – 1 level

As shown in Appendix C, the size and depth of excavation is much smaller than the depth of basement and size of existing foundations.

3.6

EXISTING UTILITIES

There are a number of network utilities which run across or close to the trench excavation. The utilities expected to be encountered include stormwater, wastewater, potable water, electricity, telecommunications and gas. Due to the variable age of all utilities within the CBD, it is expected that the condition of these utilities will likely be variable and will not be known until they are exposed.

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Connectus Project #: 2719 Client: CRLL

Groundwater and Settlement Monitoring and Contingency Plan SP3 Revision: 1, Date: 9 February 2018

4 OVERVIEW OF MONITORING & REPORTING REQUIREMENTS This section provides an overview of the monitoring and reporting required by the Consent (refer to Sections 5 and 6 of this GSMCP for detailed monitoring plans).

4.1

CONSTRUCTION STAGES

There are three main construction stages, each with particular monitoring and reporting requirements (Table 3): Table 3: Monitoring Requirements for each Construction Stage

Stage

Expected Dates

Description

Before dewatering/excavation

January 2018 to February 2018

This monitoring phase will provide baseline data against which effects resulting from the bulk excavation works can be assessed. Data required by the Consent for this stage of works will be compiled in a factual report prior to the commencement of construction dewatering/excavation with any irregular results further assessed. The outcomes will form part of the input for the construction phase assessments.

During excavation

July 2018 to June 2019

Monitoring during the bulk excavation phase will be used to verify the design analyses, by comparing the actual measurements with those estimated. The monitoring data will be used to reassess the building damage classifications at critical locations. If these reassessments indicate that the damage classifications have increased significantly then additional analyses, increased monitoring or other actions may be required. Mitigation options, discussed in Section 7 of this GSMCP, may also be required to be implemented.

After dewatering/excavation

May 2019 until stable

Where specified in the Consent, monitoring will occur until the various stages of works are completed (excavation and construction), and shall continue until stable measurements are demonstrated and written approval is provided by AC to cease monitoring.

(Baseline)

4.2

NOTIFICATION AND GSMCP CERTIFICATION

Connectus will advise AC in writing of the date of the proposed commencement of dewatering/excavation.

As defined in the Consent, commencement of dewatering/excavation means commencement of bulk excavation and/or any dewatering prior to excavation.

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Connectus Project #: 2719 Client: CRLL

Groundwater and Settlement Monitoring and Contingency Plan SP3 Revision: 1, Date: 9 February 2018

The GSMCP is required to be certified by AC at least 20 working days prior to the commencement of dewatering/excavation, and dewatering/excavation on the site will not commence until certification from AC is provided.

4.3

DATA COLLECTION AND REPORTING REQUIREMENTS

All data collected as required by conditions of the Consent from commencement of excavation to completion of monitoring will be compiled, compared with the relevant trigger levels and submitted to AC at two monthly intervals by those responsible (refer Section 4.5 of this GSMCP).

In addition to this reporting frequency, specific monitoring reporting requirements are also outlined in the table below.

4.4

INDEPENDENT BUILDING ASSESSOR (IBA) REPORTING REQUIREMENTS

CRLL has requested that AC engage an Independent Building Assessor (IBA) in accordance with the requirements of condition 109 of the Consent. A suitably qualified independent specialist, Dr Mark Foo, has been appointed to fill the role of IBA with the agreement of CRLL. The Consent requires the IBA to provide a written report to AC prior to commencement of construction and at no less than monthly intervals following commencement of construction and at key construction stages. The report may include recommendations to AC on building serviceability and damage matters, and how these matters may be addressed, having regard to the following: 

Displacement and damage predictions of the affected buildings;



Monitoring methodology and the results of that monitoring;



Alert and alarm limits; and



Any monitoring reports prepared in accordance with the required BCS, visual inspections, and trigger level exceedance reports in accordance with the response and contingency plan (as outlined in Section 7 of this GSMCP).

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Connectus Project #: 2719 Client: CRLL

Groundwater and Settlement Monitoring and Contingency Plan SP3 Revision: 1, Date: 9 February 2018

Table 4 Summary of Monitoring Requirements - Settlement

Monitoring Type

Construction Stage

Minimum Measurement Frequency

Measurement Accuracy

Reporting Requirement to AC* *in addition to the monthly IBA reports – see Section 4.4

Baseline

Excavation/ dewatering Building Condition Surveys (BCS)

A detailed pre-construction condition survey is to be carried out prior to commencement of perimeter piling adjacent to the relevant building/structure and/or commencement of dewatering/excavation.

Visual inspection of surrounding ground and external building facades (buildings listed in Appendix 1 of the Consent). To be carried out at least quarterly (3 months) from the commencement of dewatering/excavation until completion of excavation, and then at least weekly until completion of dewatering/excavation.

BCS may be required to be undertaken during extraction/dewatering at the reasonable request of AC.

PostConstruction Dewatering/ excavation

N/A

Within 15 working days to the relevant property owner. A copy of each report shall be provided to AC. A record is to be maintained of the time, date and any observations for each inspection. This record is to be maintained and submitted to AC at two monthly intervals or upon reasonable request from the AC Representative.

A post-construction condition survey shall be carried out no earlier than 6 months after completion of dewatering/excavation and within 6 months of completion of construction for any building that had a pre-construction survey.

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Related Consent Conditions

Relevant GSMCP Sections

109 - 117

Section 6.2 Appendix B

Connectus Project #: 2719 Client: CRLL

Groundwater and Settlement Monitoring and Contingency Plan SP3 Revision: 1, Date: 9 February 2018

Table 5 Summary of Monitoring Requirements – Settlement (continued)

Monitoring Type

Construction Stage

Measurement Accuracy

Reporting Requirement to AC* *in addition to the monthly IBA reports – see Section 4.4

Baseline

Ground Surface and Building Monitoring

Minimum Measurement Frequency

Excavation/ dewatering

PostConstruction Dewatering/ excavation

Each ground settlement and building movement monitoring mark shall be surveyed and recorded at least three times prior to the commencement of excavation/dewatering to establish a baseline elevation.

Depending on the stage of construction: 

Monthly, at each ground settlement and building monitoring mark, within 50m of trench excavations during excavation until such time following the completion of excavation that stable measurements are demonstrated and certification is provided by AC.

Monthly, until stable measurements are demonstrated and written approval is provided by Council for certification.

Horizontal and vertical accuracy of at least ±2 mm, or as otherwise achieved by precise levelling during baseline phase.

These records shall be compiled and submitted to AC prior to the commencement of excavation.

A record is to be maintained of the time, date and any observations for each survey.

This record is to be maintained and submitted to the Council at two monthly intervals or upon reasonable request from the AC Representative.

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Related Consent Conditions

Relevant GSMCP Sections

119 - 120

Section 6.3 Appendix B Appendix C

Connectus Project #: 2719 Client: CRLL

4.5

Groundwater and Settlement Monitoring and Contingency Plan SP3 Revision: 1, Date: 9 February 2018

ROLES AND RESPONSIBILITIES

As per the CEMP, Connectus will be responsible for compliance with the GSMCP. The Roles and Responsibilities of those involved in the Project are outlined in Table 6.

Table 6 Roles and management responsibilities

Organisation

Role

Role Responsibility

Consent Holder

 Requiring Authority, Consent Holder and Project Manager  Overall responsibility for project compliance and performance in relation to environment, quality assurance and incident management

CRLL Engineer

 Engineer to the Contract, as appointed by CRLL

Specialist Technical Adviser

 Technical review of reporting and recommendations from Connectus Instrumentation and Monitoring Manager.

Project Director

 Reviewing and reporting on environmental performance.  Inspection of works to assess compliance with the GSMCP including monitoring.

Environment & Sustainability Manager (ESM)

 Inspecting, auditing and checking of environmental management practices and procedures.  On-site compliance with consent conditions and other requirements and tracking compliance information.  Reporting to CRLL changes to construction techniques or natural environmental changes which require alterations to existing consents or new resource consents.  Preparing, reviewing and updating the CEMP and relevant subplans (including GSMCP).

Connectus

 Facilitating and overseeing environmental monitoring, including reporting to CRLL and AC.  Updating and maintaining the environmental portion of the Project Risk Register.  Training of all staff including subcontractors.

Instrumentation and Monitoring Manager

 Reviewing the data and correlating the monitoring observations with construction activities and design assumptions.  Communicating trends and observations to the Project Director, relevant members of the construction team, and CRLL.  Responding to Alert and Alarm triggers.  Managing contingency measures and responses in the event that an Alarm level is exceeded.

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Connectus Project #: 2719 Client: CRLL

Groundwater and Settlement Monitoring and Contingency Plan SP3 Revision: 1, Date: 9 February 2018

Organisation

Role

Role Responsibility

AECOM

Connectus Consultant

 Prepare, review and update of GSMCP

Independent Building Assessor (IBA)

Independent specialist (refer to Section 4.4)

 Additional inputs provided by AECOM are at the discretion of Connectus and will be provided on an as-requested basis, with assistance from other Technical Specialists as required. This includes: o

General oversight of monitoring data.

o

Response as needed by an AECOM Engineer (CPEng) to alert/alarm triggers as requested by the Project Director.

 Reviewing the GSMCP and any reports associated with alarm triggers.  As an advocate for local stakeholders, the IBA will also receive and review monitoring data and on behalf of AC to track progress and building damage and building effects.

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Connectus Project #: 2719 Client: CRLL

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5 GROUNDWATER MONITORING PLAN The measured groundwater level is more than 10m below ground level which is far below the base of the trench excavation (4m deep maximum). As there will be no effect on groundwater, no groundwater monitoring is required for the Project (SP3).

6 SETTLEMENT MONITORING PLAN 6.1

INTRODUCTION

This section outlines the building condition and settlement monitoring program Connectus will implement to: a) Verify design assumptions; b) Confirm the construction induced surface settlements; and c) Provide warning that mitigation is required to minimise or rectify potential adverse effects of settlement on structures.

The pre-excavation set-up involves the following various functional areas and parties: 

The monitoring instrument array



AECOM



Connectus JV



CRLL Team



The Independent Building Assessor



Auckland Council’s Water Allocation, Natural Resources and Specialist Input Unit



Adjacent Property Owners / Community Liaison Group



Utility Asset Owners

6.2

BUILDING CONDITION SURVEYS

6.2.1

Building Monitoring Locations

The following buildings for which building condition surveys (BCS) are required in relation to SP3 only are: 

Auckland Council Tower – 135 Albert Street



SKYCITY Convention Centre – 109 – 125 Albert Street



Manhattan Apartments – 101 – 107 Albert Street



AA Centre – 99 Albert Street Page 25

Connectus Project #: 2719 Client: CRLL

6.2.2

Groundwater and Settlement Monitoring and Contingency Plan SP3 Revision: 1, Date: 9 February 2018

Building Condition Surveys and Visual Inspections

BCS and/or visual inspections will be carried out before and after the construction activities to identify and monitor effects to buildings, in accordance with Consent Conditions 109 - 117. Additional inspections may occur during the construction process if a related complaint is received and/or is recommended by the IBA. Details relating to building surveys and inspections during the Project are provided in the following sections. The following general requirements apply to all BCS and visual inspections during each stage of the Project: 

The BCS shall be undertaken by the Connectus Design Consultant (CPEng).



All contact, correspondence and communication with building owners will be documented with records available on request.



The BCS or structure condition survey reports shall be provided to the relevant property owner within 15 working days of any survey being undertaken. A copy of each report shall also be provided to CRLL and AC.



Damage to buildings identified during BCS and visual inspections as resulting from the exercise of the Consent (refer Conditions 109 - 117) requires action as outlined in Section 7 of this GSMCP.

6.2.3

Pre-construction Surveys

Individual pre-construction BCS of all structures listed in Section 6.2.1 of this GSMCP have been undertaken to establish a baseline building condition against which any subsequent surveys can be compared.

The owners of the buildings and structures have been contacted in advance to confirm the timing and methodology for the pre-construction survey. All contact, correspondence and communication with the owners has been recorded and is available on request for AC. 6.2.4

During-Construction Surveys

Visual inspection of ground and buildings adjacent to the trench shall be carried out according to consent conditions as follows: 

The Consent Holder shall undertake a visual inspection during construction if requested by the building or structure owner where a pre-construction condition survey has been undertaken.

Where a condition survey has been undertaken by the building or structure owner, the Consent Holder shall continue to undertake quarterly (3 months) visual inspections until the completion of dewatering/excavation of the project; and



The Consent Holder shall carry out a visual inspection of the surrounding ground and external building facades of the buildings identified in Section 6.2.1 to monitor any deterioration or further cracking of any pre-existing cracks. This is to be carried out at least quarterly from the commencement of dewatering/excavation until completion of excavation.

A record is to be maintained of the time, date and any observations for each inspection. This record is to be maintained and submitted to AC.

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Connectus Project #: 2719 Client: CRLL

6.2.5

Groundwater and Settlement Monitoring and Contingency Plan SP3 Revision: 1, Date: 9 February 2018

Post-Construction Surveys

No earlier than 6 months after the completion of dewatering/excavation and within 6 months of completion of construction, post-construction BCS shall be carried out on buildings where a building condition survey was undertaken prior and during the construction phase. The survey report shall include a determination of the cause of any damage identified.

Additional BCS and reporting up to 6 months’ post-construction on any building within the area potentially affected by the excavation may be made at the request of AC. The post construction building surveys are not required in the event that the building owner agrees that the building survey is not required, and written evidence is provided to AC. Where a post-construction building condition survey confirms that the building has deteriorated as the result of construction, remedial work will be required to rectify the damage.

6.3 6.3.1

MONITORING GROUND, BUILDINGS Ground Survey and Building Monitoring Locations

A series of ground and building survey marks will be installed at 10m centre to centre intervals along the western side of Albert Street. Building Movement Monitoring Markers shall be located on each building listed in Section 6.2.1 subject to owners’ approval. This will allow the actual building movement to be monitored and compared with the estimated potential effects. Monitoring locations are presented on the drawings included in Appendix A of this GSMCP: The drawings showing these monitoring locations require certification by AC prior to the commencement of bulk excavation/dewatering.

If a pre-construction Building Condition Survey identifies significant structural cracks then, subject to the building owner’s approval, crack monitoring systems will be installed to enable ongoing measurement of the extent and width of such cracks.

6.3.2

Pre-construction Settlement Monitoring

Monitoring will commence at least 5 working days before dewatering/excavation commences (baseline monitoring). Connectus will survey and record each ground settlement and building movement monitoring mark at least three times prior to the commencement of dewatering/excavation to establish a baseline elevation. These records will be compiled and submitted to AC prior to the commencement of dewatering/excavation.

6.3.3

During-Construction Settlement Monitoring

Monitoring during construction will comprise manual surveys of monitoring marks.

6.3.4

Post-Construction Settlement Monitoring

Monitoring of the survey marks shall continue until either the completion of dewatering/excavation, or until such time following the completion of excavation/dewatering that stable measurements are demonstrated and certification is provided by AC.

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Connectus Project #: 2719 Client: CRLL

6.4

Groundwater and Settlement Monitoring and Contingency Plan SP3 Revision: 1, Date: 9 February 2018

UTILITIES AND INFRASTRUCTURE MONITORING

6.4.1

Pre-Construction

Connectus have identified the utilities (including gas, water, sewerage, telecoms stormwater and power) potentially affected by the Project and have consulted with the relevant utility owners to determine the extent of pre-construction surveys required.

Connectus Utilities Manager consulted with utility owners (Vodafone, Chorus, Vector etc) during 2017 and they agreed there was no need for pre-construction surveys as we were relocating network utilities running through the SP3 excavation works. These services are also in PVC ducts as opposed to being rigid services and hence can withstand a certain level of settlement.

Connectus continues to meet regularly with the NUOs to ensure they are well briefed with regard to the construction methodologies.

6.4.2

During Construction

The monitoring of any settlement effects on adjacent utilities shall be carried out utilising the ground settlement markers utilised for ground settlement monitoring as outlined in Section 6.3.2.

6.4.3

Post Construction

No earlier than 6 months after completion of dewatering/excavation and no later than completion of construction (subject to the owner(s) reasonable approval), a post - completion survey is to be completed by the Consent Holder, to confirm that the immediately adjacent utilities identified in the pre-construction survey have not been damaged (as required by Condition 115).

The post-completion survey is to be provided in writing to AC and shall include a determination of the cause of damage identified (if any) since the pre-construction survey, and a description of the steps taken to repair any damage.

6.5

SETTLEMENT TRIGGER LEVELS

The trigger levels for the monitoring outlined above are presented in Appendix B: 

Table B1: Deformation Limits for building and ground settlement monitoring



Table B2: Trigger levels for Albert Street Ground Movement

The proposed monitoring frequencies, and alarm and alert trigger levels will be reviewed following the BCSs to confirm they are appropriately set to ensure the “negligible” damage category will not be breached (refer to Section 8 for conditions of review of this GSMCP).

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Connectus Project #: 2719 Client: CRLL

Groundwater and Settlement Monitoring and Contingency Plan SP3 Revision: 1, Date: 9 February 2018

7 RESPONSE, MITIGATION AND CONTINGENCY PLAN 7.1

INTRODUCTION

The previous section described: the process for Routine Monitoring, including responding to structural alerts.

This section presents three further processes: 1. Response to Alerts 2. Response to Alarms 3. Response to reports of building or asset damage The processes summarise actions and flow of information between the various functional areas and parties: 

The monitoring instrument array



AECOM



Connectus JV



CRLL Team



The Independent Building Assessor



Auckland Council’s Water Allocation, Natural Resources and Specialist Input Unit



Adjacent Property Owners / Community Liaison Group



Utility Asset Owners

Where mitigation and/or remedial requirements have been outlined in the Consent, these are presented within the relevant sections below.

7.2

RESPONSE TO ALERTS

7.2.1

Settlement Alerts

In the event that settlement exceeds an identified Alert trigger level during construction works, the following will occur: 

Connectus will notify CRLL, AC and the IBA within 24 hours.



Measurements for the affected area will be taken and immediately reported on a daily basis thereafter.



The Connectus Design Consultant will: o

Reassess the works constructed up to that time to identify the reasons for higher movements; and

o

Recommend measures to restrain further increases in movement and possible ensuing effects to existing structures.

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Connectus Project #: 2719 Client: CRLL



7.3

Groundwater and Settlement Monitoring and Contingency Plan SP3 Revision: 1, Date: 9 February 2018

The Connectus Design Consultant shall subsequently prepare and submit a written report to AC within one week of alert level exceedance, which provides analyses of all monitoring data, relating to the exceedance of the trigger levels and any actions taken.

RESPONSE TO ALARMS

In the event that settlement exceeds the identified Alarm trigger levels during construction works, the actions described above for an Alert level exceedance will be undertaken along with the following measures: 

Any work likely to result in further settlement will be stopped immediately.



An alarm notice will be prepared as an email and provided to AECOM, CRLL, IBA and AC. The notice will state: o

The date, time and duration

o

The location(s) where the alarm triggers have been activated

o

The nature of the trigger – settlement, absolute or differential, inclinometer etc

o

The trigger levels and the magnitude of the exceedance.



If required additional instrumentation will be installed to monitor affected parts of the buildings with greater detail prior to work being resumed.



The Connectus Design Consultant responsible for overview of the monitoring will prepare and submit a written report to AC within one week of alarm level exceedance. This report will provide:



o

Analyses of all monitoring data relating to the exceedance of the trigger levels;

o

Assessment of risk for any further settlement and building damage;

o

Recommendations for remedial actions required in order to complete construction so as to avoid damage that will affect building serviceability; and

o

The actions that will be or have already been taken to address the triggered alarm level.

These recommendations will be implemented.

The IBA may also recommend actions to prevent damage to building serviceability, which may include stopping the works if that is in the best interests of preventing building serviceability damage.

These will be implemented, unless the building owner(s) request in writing that the construction works are to be completed in accordance with the report prepared by the Connectus Design Consultant.

7.4

RESPONSE TO BUILDING DAMAGE

In the event that damage to buildings, structures and/or services is reported during the construction works or determined from a building condition survey or inspection the following will occur: 

Connectus will notify the Connectus Design Consultant, CRLL, AC and the IBA as soon as practical, and within 2 workings days;



The Connectus Design Consultant’s Engineer will be engaged as soon as practical and within 2 working days, to inspect and record the damage;



The reported damage will be compared with the pre-construction building condition survey to determine if the damage is: o

Pre-existing, Page 30

Connectus Project #: 2719 Client: CRLL

Groundwater and Settlement Monitoring and Contingency Plan SP3 Revision: 1, Date: 9 February 2018

o

New, or

o

Pre-existing, but exacerbated



The construction history in the vicinity of the building will be reviewed, along with the recorded settlement history, to determine if the damage can be reasonably attributed to the construction works



If the damage cannot be reasonably attributed to the construction works Connectus will present a report to the IBA setting out the basis for this assessment



If the damage can be reasonably attributed to the construction works Connectus will prepare a methodology for repair of the damage caused, including timeframes.



Repairs will be undertaken as soon as practicable unless written approval for this damage is provided from the owners stating alternative arrangements (in accordance with consent condition 125). The timing and nature of the repairs will depend on the owner’s requirements, stage of construction and degree of damage.

7.5

MITIGATION OPTIONS

7.5.1

Design Validation

The first mitigation measure for the effects of settlement is to ensure that temporary ground support works are constructed in accordance with the design, and that the ground conditions encountered are consistent with the design assumptions.

During construction of the temporary works the design assumptions with regard to ground conditions will be validated by observation of construction records, and by observation of materials encountered as the excavation proceeds.

The construction of the temporary works will be subject to quality control procedures and design validation records, certifying that the temporary works have been constructed in accordance with the design, will be issued progressively.

7.5.2

Mitigation of Effects

Effects severe enough to require mitigation are not expected, based on the Assessment of Settlement Effects.

However, in the event that differential settlement or total settlement exceeds the identified Alert or Alarm trigger level during construction works, or ground conditions differ significantly from the design assumptions then the mitigation options include: 

Additional specific structural and geotechnical calculations;



Strengthen and/or stiffen ground support



Installation of additional instrumentation



Further structural assessment of an affected building

7.5.3

Contingency Measures

Connectus will develop a range of contingency measures with which to respond to the events more likely to result in trigger levels being exceeded. These measures may include the provision of stand-by temporary works materials or components that may be added to the ground support system to increase its strength or stiffness.

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Connectus Project #: 2719 Client: CRLL

Groundwater and Settlement Monitoring and Contingency Plan SP3 Revision: 1, Date: 9 February 2018

In the event the most appropriate contingency measure will be implemented to mitigate the actual or anticipated adverse effects of the triggering event.

8 MONITORING AND CONTINGENCY PLAN REVIEW This section outlines how the GSMCP will be reviewed including the mitigation and contingency procedures to make sure they are still applicable to the activities carried out.

8.1

GENERAL REVIEW OF THE GSCMP

The GSMCP will be updated, with the necessary certification by AC, throughout the course of the Project to reflect material changes associated with changes to construction methods or site conditions.

AC certification will be required for any relevant revisions of a material nature to the GSMCP. A yearly management review will otherwise be undertaken of the Project CEMP, including the GSMCP and other sub-plans. The management review procedure is described in further detail within the Project CEMP.

8.2

REVIEW OF MONITORING AND CONTINGENCY REQUIREMENTS

The Consent allows for variation to the monitoring and reporting requirements, and performance standards (subject to certification by AC) in order to take account of information, including the results of previous monitoring and changed environmental knowledge, on: 

Ground conditions;



Aquifer parameters;



Groundwater levels; and



Ground surface deformation.

As such, the conditions of consent allow for specific review and updates to the following: 

Review of the settlement alarm/alert/stop trigger levels: The trigger levels as provided in of the Consent (Appendix B of this GSMCP) may be reviewed following the required BCS and assessment to confirm they are appropriately set to ensure the slight damage category will not be breached and whether monitoring frequency is adequate. These trigger levels may be revised with more stringent levels if recommended by further assessment.



Numbers of Instruments, Types and Locations: The specification of instruments, location and numbers of instruments has been modified as a result of the following: o

Additional geotechnical investigation and ground characterisation

o

Specification of instruments and monitoring tools

o

Building Damage Hazard assessments

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Connectus Project #: 2719 Client: CRLL

Groundwater and Settlement Monitoring and Contingency Plan SP3 Revision: 1, Date: 9 February 2018

o

Detailed design of the temporary trench support system

o

Modelling of the anticipated ground movement and associated settlements adjacent to the planned excavation

Instruments have been positioned where they will be able to report movement within their range of tolerance. They have been tied to the effects of the trench and the sensitivity of the surrounding building to damage. In terms of protection to stakeholders and asset owners the current plan provides data and monitoring at least as relevant and protective as that proposed in the consent application. 

The Response Plan: included in the GSMCP (Section 7) will be implemented in the event that differential settlement between any two ground settlement monitoring marks exceeds the identified trigger levels in Appendix B, or total settlement exceeds the trigger levels. The response plan may be updated in order to deal with any adverse effect on the environment arising or potentially arising from the exercise of this consent, and in particular effects on buildings, structures and services.

Changes to the GSMCP may also arise following review of the consent conditions by AC by giving notice to Connectus. These changes may be made order to keep up with the changing knowledge of the site and deal with adverse effects of the Project on the existing environment, as outlined above.

The timing for review of consent conditions by AC is within six months after commencement of dewatering/excavation and subsequently at intervals of not less than one year thereafter.

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Connectus Project #: 2719 Client: CRLL

Groundwater and Settlement Monitoring and Contingency Plan SP3 Revision: 1, Date: 9 February 2018

APPENDIX A: DRAWINGS INSTRUMENTATION MONITORING NETWORK PLANS

List of Drawings: ï‚·

INSTRUMENTATION LOCATION PLAN - CRLC SP3 WORKS.pdf

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Groundwater and Settlement Monitoring and Contingency Plan SP3 Revision: 1, Date: 9 February 2018

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Page 35

N

INSTRUMENTATION LOCATION PLAN - CRLC2 SP3 WORKS Created by S.Milosevic (AECOM) on 9/10/17 Reference to Aurecon Drawing: CRL-AOT-ARC-000-DRG-8003-B Legend Building Prisms (Upper & Lower)

Ground Monitoring Pin

ALBERT STREET

G - 04

U/L-04

G - 05

G - 06

G - 07

G - 08

G - 09

U/L-05

U/L-06

U/L-07

U/L-08

U/L-09

G - 10

U/L-10

G - 11

U/L-11

G - 12

G - 13

U/L-12

U/L-13

G - 14

U/L-14

G - 15

G - 16

G - 17

U/L-15

U/L-16

U/L-17

G - 18

G - 19

G - 20

G - 21

U/L-18

U/L-19

U/L-20

U/L-21

G - 03 U/L-03

G - 22

U/L-22

G - 23

U/L-23 U/L-24

G - 24

FACP

FA C

G - 02

P

U/L-02

G - 01

U/L-25

G - 25

U/L-26

G - 26

U/L-01

1

EXISTING STREET LEVEL PLAN SCALE @ A1 1 : 250

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Connectus Project #: 2719 Client: CRLL

Groundwater and Settlement Monitoring and Contingency Plan SP3 Revision: 1, Date: 9 February 2018

APPENDIX B: SETTLEMENT TRIGGER LEVELS

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Table B1: Deformation Limits for Buildings as estimated in Appendix C

LOCATION

Marker IDs (Appendix A Figures)

G-01 to G-09 U/L-01 to U/L-09

TRIGGER LEVELS [+/-] ADDRESS

MOVEMENT ALERT

99 Albert Street

HORIZONTAL AT FACE OF BUILDING

15mm

18mm

VERTICAL AT FACE OF BUILDING

8mm

10mm

-

1/1000

HORIZONTAL AT FACE OF BUILDING

15mm

18mm

VERTICAL AT FACE OF BUILDING

8mm

10mm

-

1/1000

HORIZONTAL AT FACE OF BUILDING

15mm

18mm

VERTICAL AT FACE OF BUILDING

8mm

10mm

-

1/1000

HORIZONTAL AT FACE OF BUILDING

15mm

18mm

VERTICAL AT FACE OF BUILDING

8mm

10mm

-

1/1000

DIFFERENTIAL VERTICAL SLOPE ACROSS BUILDING GROUND SURFACE MOVEMENT ACROSS BUILDINGS

G-10 to G-12 U/L-10 to U/L-12

G-13 to G-18 U/L-13 to U/L-18

G-19 to G-26 U/L-19 to U/L-26

101 - 107 Albert Street

DIFFERENTIAL VERTICAL SLOPE ACROSS BUILDING

109 – 125 Albert Street

DIFFERENTIAL VERTICAL SLOPE ACROSS BUILDING

135 Albert Street

ALARM

DIFFERENTIAL VERTICAL SLOPE ACROSS BUILDING

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Connectus Project #: 2719 Client: CRLL

Groundwater and Settlement Monitoring and Contingency Plan SP3 Revision: 1, Date: 9 February 2018

Table B2: Trigger levels for Albert Street Ground Movement SITE

Ground Movement within Albert St

MOVEMENT

TRIGGER LEVELS [+/-] ADVISE

ALERT

ALARM / STOP

HORIZONTAL

20mm

30mm

40mm

VERTICAL

26mm

32mm

40mm

DIFFERENTIAL VERTICAL GROUND MOVEMENT BETWEEN MONITORING POINTS

1/500

1/200

1/50

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Connectus Project #: 2719 Client: CRLL

Groundwater and Settlement Monitoring and Contingency Plan SP3 Revision: 1, Date: 9 February 2018

APPENDIX C: ASSESSMENT OF SETTLEMENT EFFECTS

Page 40

Auckland City Rail Link In association with:

ENABLING WORKS CONTRACT 2 Separable Portion 3 - Canopy Removal and Utilities Diversion Assessment of Settlement Effects Revision: 1

9th February 2018

COMMERCIAL IN CONFIDENCE

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DOCUMENT INFORMATION Organisation:

Connectus

Document Title:

SP3 Canopy Removal and Utilities Diversion Assessment of Settlement Effects

Document based on MMS No:

n/a

Client:

CRLL

Project:

CRL Enabling Works: Contract Two

Location:

Auckland CBD

Project No:

2665

REVISION HISTORY Rev

Date

Details

Author

Approver

0

10.10.2015

Detailed design issue

S.Milosevic

K.Anderson

01

09.02.2018

FINAL for CRLL submission to AC for certification

S.Milosevic

K.Anderson

This document remains the property of Connectus. Its contents are confidential and shall not be reproduced, destroyed or given away without the express, written permission of Connects. The electronic version of this document in MMS Database on designated server(s) is the Master Copy and is a controlled document. Unless specifically noted thereon, other copies of this document are uncontrolled.

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Connectus Project #: 2665 Client: CRLL

SP3 Assessment of Settlement Effects Revision: 1, Date: 9 February 2018

Table of Contents

.................................................................................................. 3 Document information ............................................................................................................................. 3 Revision History ....................................................................................................................................... 3 1

Introduction ............................................................................................................................ 7 1.1

Overview

7

1.2

Purpose

7

1.3

Report Structure

7

2

Project Description ................................................................................................................ 9 2.1

Canopy Removal

9

2.2

Diversion of Underground Utilities

9

2.3

Sources of Settlement Effects

9

2.4

Estimated Extent of Settlement Effects

3

10

Existing Environment ........................................................................................................... 11 3.1

Land Use

11

3.2

Topography

11

3.3

Geology

11

3.3.1

Site Investigations

11

3.3.2

Geological Interpretation

12

3.3.3

Geotechnical Parameters

12

3.4

Groundwater

12

3.5

Existing Buildings

13

3.6

Existing Utilities

13

4

Technical Assessment Methodology ................................................................................... 14 4.1

Settlement Estimation Methodology

14

4.2

Methodology for Effects Assessment

14

4.2.1

Buildings

14

4.2.2

Utilities

17

5

Effects Assessment ............................................................................................................. 18 5.1

5.2

Settlement Estimates

18

5.1.1

18

Settlement due to trench excavation

Assessment of Effects on Buildings

19 Page 5

Connectus Project #: 2665 Client: CRLL

SP3 Assessment of Settlement Effects Revision: 1, Date: 9 February 2018

5.2.1

99 Albert Street – AA Centre

19

5.2.2

101 - 107 Albert Street – Manhattan Apartments

20

5.2.3

109 - 125 Albert Street - SKYCITY Convention Centre

21

5.2.4

135 Albert Street – Auckland Council Tower

23

5.3

Assessment of Effects on Utilities

24

5.4

Assessment of Effects on Roads and Infrastructure

25

6

Monitoring and Mitigation .................................................................................................... 26

7

Conclusions ......................................................................................................................... 27

8

7.1

Settlement

27

7.2

Buildings

27

7.3

Utilities

27

References .......................................................................................................................... 28

Appendix A Surface Settlement Graphs ............................................................................................... 29

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Connectus Project #: 2665 Client: CRLL

SP3 Assessment of Settlement Effects Revision: 1, Date: 9 February 2018

1 INTRODUCTION 1.1

OVERVIEW

This report has been prepared as part of the City Rail Link (CRL) Contract 2 Separable Portion 3 (SP3; the Project) which involves the removal of existing building canopies from four buildings and diversion of underground utilities within the Albert Street road corridor from Victoria Street West to Wellesley Street West. The Project includes trenching and is expected to take 12 months to complete.

This project is being delivered by Connectus, a joint venture of McConnell Dowell Constructors Limited and Downer New Zealand Limited. This GSMCP has been prepared by AECOM New Zealand Limited (AECOM) for Connectus and forms part of the Construction Environmental Management Plan (CEMP) for the Project.

The relevant resource consent for the GSMCP is Water Permit R/REG/2016/1892 for the Take and Diversion of Groundwater (the Consent).

This Assessment of Settlement Effects report provides details of the estimated surface settlements and building risk assessments adjacent to the removal of the canopies and diversion of utilities.

The building risk assessment outlines the estimated impact on adjacent structures due to the estimated surface settlements. The monitoring proposal outlines the methods in which the ground and adjacent structures may be monitored in order to verify the design assumptions and provide control and confidence during construction. In addition to this, contingency plans and preventative measures to mitigate adverse surface settlements or structural movement are provided.

This report is part of a series of documents to fulfil the scope of work. The report should be read in conjunction with the Groundwater and Settlement Monitoring and Contingency Plan (GSMCP), which is part of the Construction Environmental Management Plan for the project. Monitoring is detailed in the GSMCP and therefore is not repeated in this report.

Note that construction activities for the wider CRL project or development of neighbouring sites have the potential to cause ground movements that may be additional to those detailed in this report.

1.2

PURPOSE

The purpose of this report is to present the results of the surface settlement analysis due to the construction of the project, and the subsequent assessment of the potential effects on adjacent buildings, utilities and infrastructure, and to propose monitoring and mitigation measures to address these potential effects (where required).

This report will review the existing environment and the infrastructure which is envisaged to be affected by construction. This includes buildings and utilities within the extent of the settlement effects.

1.3

REPORT STRUCTURE

This report is structured as follows: 

Description of the project.



Explanation of the sources and the estimated extent of the potential settlement effects.



Overview of the environment, including geological conditions, key inputs into the assessment, and existing key structures within the estimated extent of settlement effects.



Results of the potential settlement effects and building damage assessment.

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Connectus Project #: 2665 Client: CRLL



SP3 Assessment of Settlement Effects Revision: 1, Date: 9 February 2018

Definition of the monitoring scheme and mitigation measures to be implemented to ensure the estimated settlement effects are confirmed and the effects on surrounding structures are controlled during construction.

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Connectus Project #: 2665 Client: CRLL

SP3 Assessment of Settlement Effects Revision: 1, Date: 9 February 2018

2 PROJECT DESCRIPTION This section presents a summary of the Project works that relate to this report. The site location is situated within a heavily developed central city environment, with four high rise buildings situated immediately adjacent to the works. Ground level varies across the site, typically falling towards the east. The streets are busy with a variety of transport modes and there are numerous existing utilities & services, typical of the city centre location.

2.1

CANOPY REMOVAL

Before excavation and utility relocation can begin, overhanging canopies will be removed. As shown in Figure 1 below, canopies attached to buildings situated along Albert Street between Victoria Street and Wellesley Street will be affected.

Figure 1 Extent of Project Works

From PTA (26 May 2017).

2.2

DIVERSION OF UNDERGROUND UTILITIES

A trench approximately 200m long, 4m deep and 1.5m wide will be constructed along Albert Street between Victoria Street and Wellesley Street as shown in Figure 1 above. Underground utilities will be relocated, removed or abandoned.

2.3

SOURCES OF SETTLEMENT EFFECTS

The source of settlement associated with the construction and operation of the project will be due to mechanical displacement of the ground. This involves the physical movement of the temporary retaining walls supporting the sides of the trench. This is the result of the lateral movement of the retaining walls as they take load (i.e. as one side is excavated and/or the other side loaded). It will also

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Connectus Project #: 2665 Client: CRLL

SP3 Assessment of Settlement Effects Revision: 1, Date: 9 February 2018

occur relatively quickly following excavation and will be concentrated in the immediate area behind the retaining walls. The magnitude of influence is dependent on the wall stiffness and strut system.

2.4

ESTIMATED EXTENT OF SETTLEMENT EFFECTS

The estimated influence zone of the potential settlement effects extends along Albert Street from Victoria Street to Wellesley Street. The settlements resulting from the excavation were found to be approximately 12mm immediately adjacent to the trench. The ground beside Auckland Council and SKYCITY Buildings are expected to experience the most amount of settlement. It is estimated to reach a maximum of 9mm.

These settlements were then used to estimate the impact and settlement for the surrounding structures. The effect on surrounding structures is expected to be “Negligible� if the vertical settlement is below 10mm, based on the building Damage Assessment Criteria (Burland, 1997, also refer Section 4.2 of this report). As the excavation settlement effects are less than 10mm, the effects to structures along the excavation are expected to be negligible.

Note that seasonal movements in the order of 25mm to 50mm in response to soil moisture changes are not unusual in Auckland, although typical seasonal movements would be less in the project area considering the extensive surface paving.

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Connectus Project #: 2665 Client: CRLL

SP3 Assessment of Settlement Effects Revision: 1, Date: 9 February 2018

3 EXISTING ENVIRONMENT Section 3 of this report outlines the environment surrounding the works. This information is essential in order to undertake an appropriate assessment of the potential effects on surrounding structures.

3.1

LAND USE

The Auckland city centre area is a built up urban environment and is New Zealand’s largest city centre and commercial / business area. It is a centre of business, art, culture, entertainment, recreation, education, tourism and residential living. Land uses above the ground along the Project alignment include high density commercial and office buildings, residential and visitor accommodation, retail, restaurants and bars.

3.2

TOPOGRAPHY

Auckland is a city built on a volcanic field, characterised by a landscape dotted with the remnants of cones and craters, ridges and valleys. The topography of the city centre area is characterised by ridges and valleys (the Queen Street valley is flanked by the Symonds Street ridge and the Albert / Vincent / Pitt Street ridge, with the Karangahape ridge at its southern end). The topography around the Project area is defined by a sloping gradient that rises from north to south, with Albert Street located on the edge of the Queen Street valley and near the ridge line of Hobson Street. Adjoining streets that run from the east or west down the valley slopes to Queen Street are relatively steep whilst Albert Street, which runs north-south, is generally flatter.

3.3

GEOLOGY

Extensive and detailed geotechnical investigations have been carried for the project. Additional information is also available from nearby developments. Typically, investigations locations are not at the trench excavation but sufficient information is available to make reasonable interpretation of the ground conditions for the purpose of this report.

3.3.1

Site Investigations

Geotechnical site investigations consisting of Cone Penetration Tests (CPTs) and Machine Drillholes (DHs) have been undertaken in the vicinity of the trench. Logs and data obtained from these investigations were presented in the Auckland City Rail Link Stage 2 Ground Investigation Factual Report (Reference 228072-RPT-AC-060, dated 15 April 2013).

Six drillholes (BH205, 206A, 206B, BH208, BH207 and BH201) and two Cone Penetrometer tests (CPT203 and CPT204) were undertaken in the vicinity of the trench. There is also data from other investigations located in the vicinity of the works, for example from development of nearby buildings.

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Connectus Project #: 2665 Client: CRLL

3.3.2

SP3 Assessment of Settlement Effects Revision: 1, Date: 9 February 2018

Geological Interpretation

The general vertical stratigraphic sequence comprises the following, in chronological order (oldest to youngest): 

East Coast Bays Formation (ECBF): is present at depth, which forms the local basement rock.

The ECBF if characterised by alternating sandstone and siltstone beds with a completely weathered (residual soil) upper surface. The unweathered rock is fractured to a varying degree.



Tauranga Group Alluvium: unconformably overlies the ECBF and is present as unconsolidated alluvial sediments comprising peat, mud, silt, sand and gravel. These materials are frequently interlayered and may form discrete lenses at some locations.



Quaternary Volcanics of the Auckland Volcanic Field (AVF): volcanic ash deposits are present at discrete locations overlying the Tauranga Group. These deposits are limited to the southern extent of the Project area, in the vicinity of Victoria St.



Fill: asphalt or concrete pavement forms the ground surface and is underlain by granular base coarse, sub-base and/or variable fill materials. Fill materials may comprise re-worked natural soils (silts, sands and gravels) or waste materials such as ash, clinker and demolition rubble.

The excavation is expected to be in existing Fill, Tauranga Group Alluvium and East Coast Bay Formation residual soil and rock. The top 2-3m of the trench will be in stiff, well compacted fill. The underlying material will either be Tauranga Group alluvium or weathered ECBF. 3.3.3

Geotechnical Parameters

The geotechnical parameters were assessed from the specific project investigation data and experience with similar materials where appropriate. Material parameters used in design are described in the table below.

Table 3-1: Geotechnical Strength Parameters

Geotechnical Unit

Description

Unit Weight 3 (kN/m )

Fill

Silts and Clays

Tauranga Group Alluvium East Coast Bays Formation (Residual soil – Completely Weathered)

Strength

Stiffness

Su (kPa)

φʹ (deg)

cʹ (kPa)

ν

Eʹ (MPa)

17

45+ 2/m

28

0

0.3

10

Silts and Clays

18

20+ 7/m

28

0

0.3

2+0.9/m

Silty Clay

18

80

30

5

0.3

10+1.5/ m

Note: parameters related to depth are relative to depth below ground level

3.4

GROUNDWATER

The expected groundwater level is at least 10m below ground level which is far below the base of the trench excavation (4m deep maximum).

Two key groundwater systems have been identified for the Project: Shallow perched system - within the Tauranga Group sediments, upper weathered ECBF and local volcanic ash/fill materials. This system comprises numerous perched and isolated water tables, Page 12

Connectus Project #: 2665 Client: CRLL

SP3 Assessment of Settlement Effects Revision: 1, Date: 9 February 2018

supported by lenses of low permeability materials and the weathered ECBF. Areas of saturation are expected to be laterally discontinuous.

Deeper (regional) groundwater system – within the ECBF this aquifer underlies the shallow perched groundwater system and is a continuous zone of saturation. In areas of higher topography, some perching on discrete mudstone layers may be present within the ECBF.

3.5

EXISTING BUILDINGS

The buildings encountered along and adjacent to the alignment are all multi-storey piled buildings. The building uses comprise a mix of residential, commercial entertainment and retail. The piled buildings are typically of more modern frame structures. These buildings are still susceptible to settlement effects, however for the purposes of this analysis they are generally considered less critical than buildings with shallow foundations.

3.6

EXISTING UTILITIES

There are a number of utilities which run across or close to the trench excavation due to the highly developed nature of the area. The utilities which are expected to be encountered and their construction type are: 

Stormwater – reinforced concrete, PVC, and earthenware.



Wastewater – brick and earthenware.



Potable Water – cement-lined cast iron, and cast iron.



Electricity – direct buried cables, and cables in PE/PVC ducts.



Telecommunications – direct buried cables, cables in PVC/PE/cast iron ducts, and fibre optic in PVC/PE/cast iron ducts.



Gas – PE, steel, and cast iron.

These utilities vary in age considerably; many of the utilities have been in the ground for many years while some will be much newer. As such, it is expected that the condition of these utilities will likely be variable and will not be known until they are exposed. Ongoing consultation with the various stakeholders has been carried out since 2012 as part of the project design to obtain the best possible understanding of the infrastructure which can be expected.

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Connectus Project #: 2665 Client: CRLL

SP3 Assessment of Settlement Effects Revision: 1, Date: 9 February 2018

4 TECHNICAL ASSESSMENT METHODOLOGY The construction of the trench and relocation of the utilities have the potential to induce surface, subsurface and lateral ground movements with resulting effects on nearby structures and their foundations.

Mechanical settlements caused by the construction of the project are expected to occur within several weeks from the start of excavation and are therefore relatively instantaneous. With no effect on the groundwater level, ground settlement due to consolidation is not considered.

4.1

SETTLEMENT ESTIMATION METHODOLOGY

The methodology to estimate the settlement is discussed below: Mechanical settlement due to shaft excavation – Carried out by using Peck’s studies and correlations to approximate the expected settlement. The area is very well known as monitoring of the Victoria and Wellesley Street shafts has been occurring for over 12 months for CRLC2 SP2.

Consolidation due to ground water drawdown is not an issue for this works as the groundwater level is well below the base of the trench.

4.2 4.2.1

METHODOLOGY FOR EFFECTS ASSESSMENT Buildings

The Burland Building Damage Classification was adopted to categorise buildings based on the effects from settlement. The limiting tensile strain criteria are presented in Table 4-1.

Table 4-1: Building Damage Assessment Criteria

Building Damage Classification after Burland (1995), and Mair et al (1996) Category of Damage

Description of Degree of Damage

Limiting Tensile Strain (%)

0

Negligible

< 0.05

1

Very Slight

2

Approx. Equivalent Ground Settlement and Slopes (CIRIA 1996) Max. Slope of Ground

Max. Settlement of Building (mm)

0.05 – 0.075

< 1/500

< 10

Slight

0.075 – 0.15

1/500 – 1/200

10 – 50

3

Moderate

0.15 – 0.3

1/200 – 1/50

50 - 75

4

Severe

> 0.3

1/200 – 1/50

> 75

5

Very Severe

> 1/50

> 75

The list of buildings which were identified as potentially affected by the works was mapped out. These buildings include those stated in the resource consent conditions, the AEE assessment of settlement effects and related documents for the wider CRL project. In total, the potential effect on 4 buildings has been assessed. Further information on building identification is included in Section 5.2.

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Connectus Project #: 2665 Client: CRLL

SP3 Assessment of Settlement Effects Revision: 1, Date: 9 February 2018

The effects assessment includes determining the expected level of effects based on the estimated tensile strains and differential settlements or slope of the ground under the subject buildings, categorising them accordingly using Table 4-1 and Table 4-2.

The building damage categorisation is developed from a masonry brick or block building founded on shallow foundations, for which tensile strains induced in a building and associated ground slopes are derived and compared against limiting values to assess the risk category and degree of damage. The piled buildings in this analysis have also been categorised on the basis of the Burland Building Damage Classification, to address potential ground settlement impact on any slab on grade structures.

The above assessment method ignores the interaction between the ground and foundations (greenfield conditions). All buildings will inherently have some degree of resistance against bending imposed by the ground. As a result, the effects estimated in Table 4-3 can generally be considered conservative.

Settlement profiles were developed along the excavation in accordance with the method outlined above, and the building cross sections plotted against these. The resulting hogging and sagging strains under the building footprint have been estimated, according to the method of Burland and Wroth, considering bending, diagonal and horizontal strains. Allowance has been made for the structural stiffness of the building through use of a structural stiffness parameter that is dependent on the flexibility of the building. The estimated critical strain was then compared with the Burland criteria of Table 4-1 and the expected building damage classification in accordance with the following table.

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Connectus Project #: 2665 Client: CRLL

SP3 Assessment of Settlement Effects Revision: 1, Date: 9 February 2018

Table 4-2: Building Damage Classifications

Category of Damage 0

1

Normal Degree of Severity Negligible

Very Slight

Description of Typical Damage (Building Damage Classification after Burland (1995), and Mair et al (1996)) Hairline cracks.

Fine cracks easily treated during normal redecoration. Perhaps isolated slight fracture in building. Cracks in exterior visible upon close inspection.

Typical crack widths are up to 1 mm.

2

Slight

General Category (after Burland - 1995)

Cracks easily filled. Redecoration probably required.

Several slight fractures inside building. Exterior cracks visible, some repainting may be required for weather tightness. Doors and windows may stick slightly.

Aesthetic Damage

Typical crack widths are up to 5 mm.

3

Moderate

Cracks may require cutting out and patching.

Recurrent cracks can be masked by suitable linings.

Brick pointing and possible replacement of a small amount of exterior brickwork may be required. Doors and windows sticking. Utility services may be interrupted. Weather tightness often impaired.

Typical crack widths are 5 to 15 mm or several greater than 3 mm.

4

Severe

Extensive repair involving removal and replacement of walls especially over doors and windows required.

Window and door frames distorted. Floor slopes noticeably. Walls lean or bulge noticeably. Some loss of bearing in beams. Utility services disrupted.

Serviceability Damage

Typical crack widths are 15 to 25 mm but are also dependent on the number of cracks.

5

Very Severe

Major repair required involving partial or complete reconstruction. Beams lose bearing; walls lean badly and require shoring. Windows broken by distortion.

Danger of instability.

Stability Damage

Typical crack widths are greater than 25 mm but are also dependent on the number of cracks.

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4.2.1.1

SP3 Assessment of Settlement Effects Revision: 1, Date: 9 February 2018

Summary of Expected Building Damage Classification

All of the assessed buildings have been classified as “Negligible” on the basis of estimated ground movements, which correspond to aesthetic damage only. The following table provides a summary of the building classification of the buildings, as identified in the resource consent conditions (Appendix 2).

Table 4-3: Summary of Building Classification Affected by Displacement

Maximum Estimated Slope

Maximum Estimated Settlement (mm)

Building Damage Classification

Address

Building

Estimated Tensile Strain (%)

99 Albert Street

AA Centre

<0.001

1/5250

3

Negligible

101 - 107 Albert Street

Manhattan Apartments

<0.001

1/7500

3.5

Negligible

109 – 125 Albert Street

SKYCITY Convention Centre

<0.001

1/7200

9

Negligible

135 Albert Street

Auckland Council Tower

<0.001

1/4900

9

Negligible

4.2.2

Utilities

Damage to utilities due to settlement is considered less likely than damage to buildings as the allowable slopes are much lower for buildings. Damage to utilities due to settlement is usually the result of tension created in the walls of the utility. This typically manifests as either opening of joints (for jointed pipes/ducts) or cracks in the cables or ducts. The purpose of the works is to locate and relocate/abandon all utilities in that area. As such, no further assessment has been carried out for utilities which are in the vicinity of the excavation works.

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Connectus Project #: 2665 Client: CRLL

SP3 Assessment of Settlement Effects Revision: 1, Date: 9 February 2018

5 EFFECTS ASSESSMENT The settlement effects which have been analysed in this report are based on the sources of settlement discussed in Section 4. These effects have been combined to produce the overall long term estimated settlement effects due to the construction.

These settlement effects will predominantly occur during the construction period. The settlement due to mechanical effects is likely to occur quickly following the ground excavation.

The estimated settlement effects are summarised in this section. More detail is provided in Appendix A.

5.1

SETTLEMENT ESTIMATES

5.1.1

Settlement due to trench excavation

The estimated surface settlements due to the excavation works are presented in Appendix A. The mechanical settlements at the edge of excavation are up to 12mm and extend up to 7m away from the trench if it was a greenfield site. With the trench located in close proximity to buildings, the effect of settlement will intrude into the surrounding building properties. The largest mechanical settlement occurs at the Auckland Council Tower and SKYCITY Convention Centre where 9mm of settlement is estimated to occur adjacent to the building face. The largest horizontal displacement also occurs at the Auckland Council Tower and SKYCITY Convention Centre with the maximum estimated displacement being 18mm.

5.1.1.1

Vertical Settlement

The surface settlements are shown in Appendix A, and are summarised in the table below. As all of the trenches are 4m deep and 1.2-1.5m wide, the expected vertical settlement for all sections are identical.

Table 5-1: Estimated Vertical Settlement

Location

Maximum Vertical Settlement (mm)

Sections A - E 5.1.1.2

12

Distance from Wall (m) 5mm Settlement

10mm Settlement

3.7

1.1

Horizontal Settlement

In some cases the horizontal movement can govern the building damage assessment, therefore the horizontal displacements were also analysed for the excavation. The horizontal component of the settlements are summarised in the table below.

Table 5-2: Estimated Horizontal Displacement

Location

Sections A - E

Maximum Horizontal Settlement (mm) 24

Distance from Wall (m) 5mm Settlement

10mm Settlement

3.7

1.1 Page 18

Connectus Project #: 2665 Client: CRLL

5.2

SP3 Assessment of Settlement Effects Revision: 1, Date: 9 February 2018

ASSESSMENT OF EFFECTS ON BUILDINGS

This section provides the building description, potential effects and existing building condition of the buildings assessed. The full list of buildings that have been assessed are: 

99 Albert Street - AA Centre



101 – 107 Albert Street - Manhattan Apartments



109 – 125 Albert Street - SKYCITY Convention Centre



135 Albert Street - Auckland Council Tower

5.2.1 5.2.1.1

99 Albert Street – AA Centre Building description

The AA Centre building at 99 Albert Street is a nineteen-storey piled-foundation block constructed in or about 1986. The building comprises a basement and eighteen upper levels.

The building’s façade comprises reinforced concrete precast panels. The floor structure to the upper levels comprises precast steel-reinforced concrete supported by reinforced concrete frames.

5.2.1.2

Potential effects

The AA Centre is located 4.7m from the edge of the trench. As shown in the figure below, the scale of excavation work required for the SP3 section is very small in comparison to the size of the building and its piled foundations. There will be negligible effect on the building.

Figure 5-1: Cross-section of the AA Centre

The building has been assessed to fall within the risk category corresponding to “Negligible” damage on the basis of the estimated effects noted in the following table.

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Connectus Project #: 2665 Client: CRLL

SP3 Assessment of Settlement Effects Revision: 1, Date: 9 February 2018

Table 5-3: Estimated Effects on 99 Albert Street

Estimated Effects

Building Damage Classification

Maximum Estimated Settlement

3mm

Negligible

Maximum Estimated Slope

1/5250

Negligible

Maximum Differential Horizontal Displacement

6mm

-

Maximum Tensile Strain

<0.001

Negligible

Overall Building Damage Classification 5.2.1.3

Negligible

Conclusions

Based on the limited estimated effects on the AA Centre building from the trench excavation along Albert Street, the building is expected to experience negligible effects from project construction.

It is recommended that the building is monitored during construction.

5.2.2 5.2.2.1

101 - 107 Albert Street – Manhattan Apartments Building description

The Manhattan Apartments building, located at 101-107 Albert Street, is a twelve-storey piledfoundation building constructed in or about 1975.

The building’s façade is comprised of reinforced concrete precast panels. The floor structure to the upper levels comprises precast steel-reinforced concrete supported by reinforced concrete frames.

5.2.2.2

Potential effects

The edge of the trench is located 4.3m from the face of the Manhattan Apartments building at 101 107 Albert Street. As shown in the figure below, the scale of excavation work required for the SP3 section is very small in comparison to the size of the building and its piled foundations. There will be negligible effect on the building.

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Connectus Project #: 2665 Client: CRLL

SP3 Assessment of Settlement Effects Revision: 1, Date: 9 February 2018

Figure 5-2: Cross-section of the Manhattan Apartments

The building has been assessed to fall within the risk category corresponding to “Negligible” damage on the basis of the estimated effects noted in the following table.

Table 5-4: Estimated Effects on 101 - 107 Albert Street

Estimated Effects

Building Damage Classification

Maximum Estimated Settlement

3.5mm

Negligible

Maximum Estimated Slope

1/7500

Negligible

Maximum Differential Horizontal Displacement

7mm

-

Maximum Tensile Strain

<0.001

Negligible

Overall Building Damage Classification 5.2.2.3

Negligible

Conclusions

Based on the limited estimated effects on the Manhattan Apartments building from the trench excavation along Albert Street, the building is expected to experience negligible effects from project construction.

It is recommended that the building is monitored during construction.

5.2.3 5.2.3.1

109 - 125 Albert Street - SKYCITY Convention Centre Building description

The building located at 109 – 125 Albert Street, SKYCITY Convention Centre, is a 24-storey piledfoundation high rise building constructed in 2002. The building’s façade comprises reinforced concrete

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SP3 Assessment of Settlement Effects Revision: 1, Date: 9 February 2018

precast panels. The floor structure to the upper levels comprises precast steel-reinforced concrete supported by reinforced concrete frames.

5.2.3.2

Potential effects

The SKYCITY building is located 1.5m from the edge of the trench. As shown in the figure below, the scale of excavation work required for the SP3 section is very small in comparison to the size of the building and its piled foundations. There will be negligible effect on the building.

Figure 5-3: Cross-section of the SKYCITY Convention Centre

The building has been assessed to fall within the risk category corresponding to “Negligible” damage on the basis of the estimated effects noted in in the following table.

Table 5-5: Estimated Effects on 109 – 125 Albert Street

Estimated Effects

Building Damage Classification

Maximum Estimated Settlement

9mm

Negligible

Maximum Estimated Slope

1/7200

Negligible

Maximum Differential Horizontal Displacement

18mm

-

Maximum Tensile Strain

<0.001

Negligible

Overall Building Damage Classification

Negligible

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5.2.3.3

SP3 Assessment of Settlement Effects Revision: 1, Date: 9 February 2018

Conclusions

Based on the limited estimated effects on the SKYCITY building from the trench excavation along Albert Street, the building is expected to experience negligible effects from project construction.

It is recommended that the building is monitored during construction.

5.2.4 5.2.4.1

135 Albert Street – Auckland Council Tower Building description

The building located at 135 Albert Street is a 28-storey piled-foundation high rise building constructed in or about 1989. The building comprises of 28 floors with a basement. The building’s façade comprises reinforced concrete precast panels. The floor structure to the upper levels comprises precast steel-reinforced concrete supported by reinforced concrete frames.

5.2.4.2

Potential effects

The building at 135 Albert Street is located 1.5m from the edge of the trench. As shown in the figure below, the scale of excavation work required for the SP3 section is very small in comparison to the size of the building and its piled foundations. There will be negligible effect on the building.

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SP3 Assessment of Settlement Effects Revision: 1, Date: 9 February 2018

Figure 5-4: Cross-section of the Auckland Council Building above and below ground level

The building has been assessed to fall within the risk category corresponding to â&#x20AC;&#x153;Negligibleâ&#x20AC;? damage on the basis of the estimated effects noted in in the following table.

Table 5-6: Estimated Effects on 135 Albert Street

Estimated Effects

Building Damage Classification

Maximum Estimated Settlement

9mm

Negligible

Maximum Estimated Slope

1/4900

Negligible

Maximum Differential Horizontal Displacement

18mm

-

Maximum Tensile Strain

<0.001

Negligible

Overall Building Damage Classification 5.2.4.3

Negligible

Conclusions

Based on the limited estimated effects on the Auckland Council Tower from the trench excavation along Albert Street, the building is expected to experience negligible effects from project construction.

It is recommended that the building is monitored during construction.

5.3

ASSESSMENT OF EFFECTS ON UTILITIES

The potential effect of settlement on utilities is due to deflection causing horizontal strains or opening of joints (depending on the utility type). The ability of a utility to withstand the deflections caused by settlement will depend on its material, the type of joints, the working conditions, and the age of the utility.

Differential settlement for the project is limited, therefore any effect other utilities is expected to be negligible.

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Connectus Project #: 2665 Client: CRLL

5.4

SP3 Assessment of Settlement Effects Revision: 1, Date: 9 February 2018

ASSESSMENT OF EFFECTS ON ROADS AND INFRASTRUCTURE

The assessment of effects for the roads surrounding the excavation indicates that the settlement slopes are a very small change in gradient of the roads and is not expected to affect the road or drainage flow paths.

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Connectus Project #: 2665 Client: CRLL

SP3 Assessment of Settlement Effects Revision: 1, Date: 9 February 2018

6 MONITORING AND MITIGATION Refer to the Groundwater and Settlement Management and Contingency Plan for details of proposed monitoring and mitigation.

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Connectus Project #: 2665 Client: CRLL

SP3 Assessment of Settlement Effects Revision: 1, Date: 9 February 2018

7 CONCLUSIONS 7.1

SETTLEMENT

Settlement analysis was undertaken for the project which includes analysis of the proposed excavation. Sections were taken at key locations which were then assessed based on the mechanical settlement effects.

The resulting maximum vertical settlements were found to be less than 12mm across the trench. The maximum vertical settlement and horizontal displacement estimated are 9mm and 18mm respectively and located at the Auckland Council and SKYCITY Convention Centre Buildings. These settlements were then used to assess the building damage category for the surrounding structures.

7.2

BUILDINGS

The effects on the buildings were assessed using an internationally accepted method (Burland, 1997).

The method determines the curvature and strain in a building and plots the values against a series of criteria to assess the likely effect on the structure. The classification of potential effects was described in this report. In summary the assessments estimate that there will be â&#x20AC;&#x153;Negligibleâ&#x20AC;? for all the buildings assessed.

7.3

UTILITIES

The effects of the works on utilities at the surface are expected to be negligible and managed easily.

Effects on utilities at depth are expected to be no more than minor, and will be remedied by repairs if required.

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Connectus Project #: 2665 Client: CRLL

SP3 Assessment of Settlement Effects Revision: 1, Date: 9 February 2018

8 REFERENCES 1. AECOM (2015), Enabling works contract 2, groundwater and settlement monitoring and contingency plan 2. Aurecon (2014). City Rail Link Project: Reference Design – Assessment of Effects on the Environment, Albert Street Stormwater Main Realignment. Report prepared for Auckland Transport, dated November 2014 3. Burland J B and Wroth C P (1974), Settlement of buildings and associated damage. State of the Art Review, Proceedings, Conference on Settlement of Structures, Cambridge, Pentech Press, London, pp. 611-654.

4. Burland J B (1995), “Closing Ceremony”, Proc. 1st IS-Hokkaido’ 94, 2, pp. 703-705.

5. Burland J B (1997), Assessment of risk of damage to buildings due to tunnelling and excavation, Earthquake Geotechnical Engineering, Ishihara (ed), Balkema, Rotterdam, pp.

1189-1201.

6. CIRIA, 1996, Prediction and effects of ground movements caused by tunnelling in soft ground beneath urban areas, project report 30.

7. Mair, R.J, Taylor, R.N. and Burland, J.B., (1996), Prediction of ground movements and assessment of risk of building damage due to bored tunnelling, Geotechnical aspects of underground construction in soft ground.

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Connectus Project #: 2665 Client: CRLL

SP3 Assessment of Settlement Effects Revision: 1, Date: 9 February 2018

APPENDIX A SURFACE SETTLEMENT GRAPHS

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Expected Settlement Vertical settlement (mm) 0

1

2

3

4

5

6

7

8

9

10

0

Distance from excavation (m)

1 2 3 4 5 6 7 8

Legend - Face of building Sections A,B&C - Auckland Council & SKYCITY Convention Centre Section D - Manhattan Apartments Section E - AA Centre

Reference: O'Rourke et al, 1976.

Distance from edge of trench (m) Sections A,B&C 1.5 Section D 4.3 Section E 4.7

Reference: Aurecon dwg: CRL-AOT-UTI-000-SKE-0402-1.0

11

12

13