Ground Investigation Factual Report and Geotechnical Long … · 2018-05-17 · Beca // 2 May 2018 4216571 // NZ1-15242655-52 0.52 // page 135 Appendix F Ground Investigation Factual

Beca // 2 May 2018

4216571 // NZ1-15242655-52 0.52 // page 135

Appendix F

Ground Investigation Factual Report and Geotechnical Long Sections - Aurecon

St Marys Bay and Masefield Beach Water Quality Improvement Project

Ground Investigation Factual Report 255303-0000-REP-GG-0008

Auckland Council

29 March 2018

Revision: 4

Reference: 255303

Aurecon |

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Document control

Report title Ground Investigation Factual Report255303-0000-REP-GG-0008

Document ID 255303-0000-REP-GG-0008

Project number 255303

Client Auckland Council Client contact Caroline Crosby

Rev Date Revision details/status Prepared by

Author Verifier Approver

1 23 June 2017 First Draft, for client comment IM IM PAK MC

2 29 August 2017 Updated with additional data IM IM JME MC

3 24 January 2018 Updated with additional data IM IM PAK MC

4 29 March 2018 Updated with additional data IM IM PAK MC

Current revision 4

Approval

Author signature Approver signature

Name Isabella Merschdorf Name Margaret Cobeldick

Title Geologist Title Associate Water Engineer

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Project 255303 | File 255303-0000-REP-GG-0008.docx | 29 March 2018 | Revision 4

Contents 1. Introduction 4

1.1 Overview 4 1.2 Previous investigations 4 1.3 Investigation Contractors 4 1.4 Revision History 4

2. Site Setting 5 2.1 Site Location 5 2.2 Geology 5

3. Methodology 6 3.1 Site Constraints 6 3.2 Numbering Systems 6 3.3 Core Logging 6 3.4 Logging Standard 6 3.5 Layer Codes 7 3.6 Surveying 8 3.7 Core Storage 9 3.8 Sampling 10

4 Ground Investigations 11 4.1 Overview 11 4.2 Pre-Drill 12 4.3 Rotary Cored Boreholes 13 4.4 Cone Penetration Tests 13 4.5 Trenches 13 4.6 In-situ Testing 13 4.7 Backfill 14 4.8 Geophysics 14

5 Installations 17 5.1 Introduction 17 5.2 Vibrating Wire Piezometers 17 5.3 Standpipes 17 5.4 Groundwater Monitoring 18

6 Laboratory Testing 19 6.1 Scope 19 6.2 Test Register 19 6.3 Soil Testing 20 6.4 Rock Strength Testing 21

7 Contamination Testing 23

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7.1 Scope of Contamination Testing 23 7.2 Schedule of Contamination Testing 23

8 Limitations 25 9 References 26

Appendices

Appendix A Exploratory Location Plans

Appendix B Boreholes

Appendix B1 Borehole Logs

Appendix B2 Borehole Photographs

Appendix B3 Borehole Installations

Appendix C In-situ Testing

Appendix C1 Packer Testing

Appendix C2 Cone Penetration Testing

Appendix D Laboratory Testing Results

Appendix D1 Test Register

Appendix D2 Push Tube Logs

Appendix D3 Tube Density Testing

Appendix D4 PSD – Wet Sieve Testing

Appendix D5 PSD – Hydrometer Testing

Appendix D6 Atterberg Limits Testing

Appendix D7 CU Triaxial Testing

Appendix D8 UU Triaxial Testing

Appendix D9 Unconfined Compressive Strength Testing

Appendix E Bathymetry and Geophysics

Appendix E1 Land-based and marine Geophysics

Appendix E2 Ports of Auckland Bathymetry

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Figures Figure 4-1 – Land Geophysics: 1 MASW (red) line and 9 GPR (yellow) lines 15 Figure 4-2 – Extent of Marine Geophysics (Appendix E1) coincides with extent of Bathymetry

(Appendix E2) 16

Tables Table 3-1: Geological Layer Codes used on Exploratory Hole Logs 7 Table 3-2: Ground Investigation Location Survey Data – Stage 1 Land Boreholes 8 Table 3-3: Ground Investigation Location Survey Data – Stage 2 Land Boreholes 8 Table 3-4: Ground Investigation Location Survey Data – Stage 2 Marine Boreholes 9 Table 3-5: Ground Investigation Location Survey Data – Stage 2 Cone Penetration Tests 9 Table 3-6: Ground Investigation Location Survey Data – Stage 2 Trenches 9 Table 4-1: Investigation Locations and Depths – Stage 1 Land Boreholes 11 Table 4-2: Investigation Locations and Depths – Stage 2 Land Boreholes 11 Table 4-3: Investigation Locations and Depth – Stage 2 Marine Boreholes 12 Table 4-4: Investigation Locations and Depths – Stage 2 Cone Penetration Tests 12 Table 4-5: Investigation Locations and Depths - Stage 2 Service Investigation Trenches 12 Table 4-6: Summary of Packer Testing 14 Table 5-1: Vibrating Wire Piezometer Details 17 Table 5-2: Standpipe Details – Stage 1 Boreholes 17 Table 5-3: Standpipe Details – Stage 2 Boreholes 18 Table 6-1: Summary of Laboratory Testing 19 Table 6-2: Summary of Testing Standards used by Testing Laboratory 20 Table 6-3: Summary of Soil Testing 20 Table 6-4: Summary of Rock Strength Testing 21 Table 7-1: Schedule of Contamination Testing Samples 23

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Aurecon | Page 4 Project 255303 | File 255303-0000-REP-GG-0008.docx | 29 March 2018 | Revision 4

1. Introduction 1.1 Overview The St Marys Bay and Masefield Beach Water Quality Improvement Project (herein ‘the project’) is an Auckland Council (AC) project being undertaken mitigate the frequent combined wastewater/stormwater overflows (CSOs) that occur at St Marys Bay and Masefield beaches, by providing CSO storage within a proposed new storage pipeline located from Point Erin Park to London/New Street. This pipeline will store the CSOs from the local catchment, and return these to Watercare’s Branch 5 sewer when this existing pipeline has capacity.

The project includes the construction of three shafts (one in Point Erin Park, one in St Marys Bay and one on the intersection of New Street / London Street) and the installation of the new storage pipeline by way of tunnelling. The main construction site will be located within the Point Erin Park, where the majority of spoil will be extracted, with some open trenching required along Curran Street and Sarsfield Street. Further trenching or jacking will be used to install the marine discharge pipeline across Curran St and past the seawall west of Curran Street, with the marine pipeline discharging via an outlet structure some 450m from shore to the west of the Auckland Harbour Bridge.

The present factual report contains the data collected during the two stages of Ground Investigation carried out along the preferred storage pipeline alignment and at the proposed shaft locations. This investigation was a combined geotechnical and environmental assessment. All drilling and geotechnical testing is reported here, while environmental testing and interpretation is reported in the Detailed Site Investigation Report, Aurecon (2018).

The site referred to as ‘St Marys Bay Reserve’ in this project is defined as that part of the larger Point Erin Park reserve that is accessed from the northern end of St Marys Road, and which lies between the settlement of St Marys Bay and the SH1 Northern Motorway to the north-east.

1.2 Previous investigations Aurecon was previously engaged by Auckland Council to carry out a geotechnical desktop study in 2016, looking at various alternative options including the concept design of a disinfection plant in St Mary’s Bay Reserve. A technical memorandum was issued in late 2016 presenting the findings of the geotechnical concept study looking at various tunnelling alignments and options as the preferred method of resolving the issue of regular overflows of wastewater onto the local beaches.

1.3 Investigation Contractors Drill Force New Zealand Ltd was engaged to carry out the geotechnical drilling component of the ground investigation (including road opening and associated activities by their sub-contractors).

ScanTec Ltd was engaged to carry out both marine and land geophysical surveys north of the Auckland Harbour Bridge and at St Mary’s Bay Reserve, respectively.

1.4 Revision History This document is Revision 4. It has been updated to include the results of laboratory testing carried out as part of the Stage 2 ground investigation that was carried out between October and December 2017.

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2. Site Setting 2.1 Site Location The investigation area covers the St Marys Bay area between New Street and Curran Street – bounded to the north by the Northern Motorway and to the south by Hackett Street and Sarsfield Street. The marine investigation covers a portion of the Waitemata harbour area between Masefield Beach and the Auckland Harbour Bridge.

2.2 Geology The regional geology of the Auckland urban area is described in the GNS Science 1:50,000-scale geological map of Sheet R11 (Kermode, 1992). Kermode’s stratigraphy provides the basis of the Aurecon understanding of the geology of the alignment and his terminology has been adopted for the Aurecon basic description and classification. The main stratigraphic units (from oldest to youngest) are:

East Coast Bays Formation (ECBF): is a thick (hundreds of metres) sequence of alternating sandstone and siltstone dating from the Miocene (c. 20 Million years old) that underlies the entire project area. The upper parts of the ECBF are typically weathered, though degree and depth of weathering varies considerably.

Tauranga Group: ECBF sedimentary rocks are locally overlain by the unconsolidated fine sediments of the Tauranga Group. Kermode subdivides the group into units ranging from older soils associated with Pleistocene low sea-levels (Puketoka Formation) to Recent (<10,000 years) “littoral” (intertidal) deposits associated with modern harbours and shorelines or alluvial deposits associated with modern streams.

Fill: The extent, depth and type of fill varies considerably across the project area. Hydraulic- and construction fill was used in the reclamation of the waterfront area for the construction of the motorway.

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3. Methodology 3.1 Site Constraints Ground investigation in the project is typically constrained by existing development, transport infrastructure and/or buried utilities. Final site selection of each investigation position was determined after an on-site investigation of utilities and approval of traffic management plans for those sites located on the road reserve.

3.2 Numbering Systems The exploratory hole locations are identified by a unique two-digit number after the prefix of ‘BH’ for land-based boreholes, ‘MA’ for marine boreholes, ‘RA’ for machine excavated test pits, or ‘CPT’ for cone penetration tests.

In general, Stage 1 boreholes were numbered in the series 1 to 10, and Stage 2 boreholes were numbered 20 onwards.

BH02 was dropped because it could not be safely drilled due to difficulties in locating the wastewater pipe beyond doubt.

Several holes have an A or B suffix, as explained below:

▪ In the case of BH07, two candidate locations (BH07A and BH07B) were initially marked up due to the proximity to utilities and uncertainty regarding the fill material. The service clearance hand auger refused in BH07A before achieving 1.5m clearance so drilling was abandoned at this location. Ultimately, BH07B was rotary core drilled to target depth after successful hand auger clearance to 1.5m.

▪ The initially proposed location for BH09 could not be safely drilled due to a significant number of key utilities at various depths, and so an alternate position, BH09A, was sought and finally drilled to target depth.

▪ BH21A and BH21B are less than 1.5m apart. There is no BH21.

3.3 Core Logging Drilling was carried out with full- or part-time supervision by an Aurecon geologist. Site observations were recorded on standard forms, and photographs were generally taken of samples recovered on the split, before samples were removed and placed in the core box. Core box photography was generally carried out on site. Core boxes were transferred to the Aurecon office basement, usually at the end of each drilling shift.

Core logging was carried out by Aurecon geologists on site where possible and additional observations and installation records were added later from daily drilling logs and site supervision records. All logging was checked and verified by senior staff to maintain a consistent approach and uniform quality of descriptions.

3.4 Logging Standard All rocks and soils were logged in general accordance with the guidelines set out in the New Zealand Geotechnical Society (NZGS) “Guideline for the Field Classification and Description of Soil and Rock for Engineering Purposes” (2005).

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3.5 Layer Codes The project has adopted a layer code system to facilitate data handling and the subsequent development of the geological model and analysis of test data. The purpose of this system was to group soils and rocks with broadly similar properties. The system used here was developed by Aurecon for the Waterview Connection and Western Ring Route ground investigations (and earlier investigations), but has been modified to accommodate ground conditions encountered in the St Marys Bay project.

Table 3-1 provides an explanation of the layer codes used in the report. Where possible the codes are aligned with map codes used by Kermode (1992). For example, the Aurecon layer code TL is functionally identical to Kermode’s “tl”.

The layer codes assist with electronic data management, enable emphasis to be placed on particular lithologies, and help with later interpretation, analysis and parameter evaluation. For example, EUs1 is used to identify ECBF lithology known as “uncemented sand” or “running sand”.

The system also allows alternate grouping to the NZGS standards: for example EUg refers to conglomeratic sandstones allowing differentiation from the more common fine-medium sandstones. Similarly, the strength code “3” identifies rock in the upper range of the NZGS weak range (or stronger).

Table 3-1: Geological Layer Codes used on Exploratory Hole Logs

Geological Layer Codes

Stratigraphic Contextual Modifier Lithologic Strength

F Fill c cohesive

g granular

T Tauranga Group

L Littoral (coastal,

estuarine, marine)

c clay

z silt

s sand

b bio-clastic

V Alluvium

associated with AVF

g gravel

p peat

A Alluvium o organic soil

E East Coast Bays Formation

R Residual to CW c clay (ER only)

z siltstone

W MW to HW

s sandstone

g conglomeratic medium to coarse sandstone

k conglomerate

U UW to SW i interbedded sandstone/siltstone

1 "uncemented" (for sand/sandstone only)

2 Extremely weak to weak

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3 "Weak+" to moderately strong

Notation: UW: Unweathered SW: Slightly Weathered MW: Moderately Weathered HW: Highly Weathered CW: Completely Weathered

3.6 Surveying The as–built locations of the investigative boreholes were surveyed in terms of Mount Eden 2000 Geodetic Datum and Auckland 1946 Vertical Datum. The survey equipment used was a combination of GNSS and total stations.

A location plan (Drawing DRG-CC-1023-E) showing the ground investigation positions is presented in Appendix A. The coordinates and ground levels for completed ground investigations are presented in Table 3-2 to Table 3-6.

Table 3-2: Ground Investigation Location Survey Data – Stage 1 Land Boreholes

Ground Investigation Location Survey Data – Stage 1 Land Boreholes

Borehole Easting Northing Surface (mRL)

BH01 398634.5 803974.6 21.4

BH03 398443.50 804082.20 3.84

BH04 398397.08 804096.50 3.35

BH05 398349.86 804156.07 3.19

BH06 398239.92 804266.22 19.79

BH07B 398037.91 804491.78 4.14

BH08 397888.13 804628.83 3.20

BH09A 397810.3 804598.9 4.7

Table 3-3: Ground Investigation Location Survey Data – Stage 2 Land Boreholes



BH20 398643.74 803967.92 21.53

BH21A 398657.40 803957.40 22.10

BH21B 398656.75 803956.42 22.33

BH23 398408.82 804100.44 3.67

BH24 398371.64 804136.21 3.26

BH25 398238.50 804269.38 19.63

BH26 397931.42 804638.48 3.52

BH27 397925.46 804674.85 3.41

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BH28 397818.98 804671.90 3.05

BH30 397897.42 804340.83 14.04

Table 3-4: Ground Investigation Location Survey Data – Stage 2 Marine Boreholes

Ground Investigation Location Survey Data – Stage 2 Marine Boreholes


MA01 397680.2 805060.1 -4

MA02 397771.6 804801 -2.2

MA03 397725.3 804910 -2.2

Table 3-5: Ground Investigation Location Survey Data – Stage 2 Cone Penetration Tests

Ground Investigation Location Survey Data – Stage Cone Penetration Tests

CPT Easting Northing Surface (mRL)

CPT20 398366.52 804137.1 3.16

CPT21 398375.27 804133.2 3.24

CPT22 398386.13 804124.8 3.32

CPT23 398399.23 804119.4 3.74

CPT24 398371.17 804135.3 3.19

CPT25 398361.03 804140.4 3.20

Table 3-6: Ground Investigation Location Survey Data – Stage 2 Trenches

Ground Investigation Location Survey Data – Trenches

Trench Easting Northing Surface (mRL)

RA04 397815 804661 3

RA05 397902 804640 3.5

RA06 397824 804661 3

RA07 397944 804652 3.5

The coordinates and levels provided in this table represent one point within each trench (where a utility is recorded).

3.7 Core Storage The recovered core was placed in core boxes on-site. Standard Penetration Tests (SPT) samples were bagged on-site to retain natural moisture content. Core boxes were transported to the Aurecon office basement.

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3.8 Sampling

3.8.1 Field Sampling Sampling requirements were communicated as a specification for each site. Requirements varied widely as holes had diverse purposes. Field sampling generally consisted of SPT split spoon sampling, and/or collection of thin-wall push tubes.

Soil samples for chemical analysis were collected on-site by an Aurecon contaminated land specialist and samples maintained in appropriate environmental conditions, accompanied by relevant chain-of-custody documentation until delivery to the laboratory. Details of samples collected and analysis undertaken are detailed in the Detailed Site Investigation Report (Aurecon (2018). St Marys Bay - Detailed Site Investigation).

3.8.1.1 Standard Penetration Test (SPT) sampling

Where identified as a requirement, SPT was typically carried out at 1.5m spacing (until at least two SPT tests with a penetration resistance of N=50 were carried out). However, SPT testing was discontinued at depth after the required data had been obtained and discussed with senior staff.

3.8.1.2 Thin Wall Push Tube Sampling

Thin wall ‘push tubes’ were used to collect ‘undisturbed’ samples in a near natural state with minimal sampling disturbance in a number of boreholes. An undisturbed sample is required for strength, compressibility and permeability testing. The samples are collected using a 54mm diameter (U54) push tube. The returned tube is then sealed with wax by the drilling contractors.

3.8.1.3 Core Sampling

In the field, core was logged, photographed and placed in core boxes before being transported off site.

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4 Ground Investigations 4.1 Overview The Stage 1 and Stage 2 ground investigations are summarised in Table 4-1 to Table 4-5. Table 4-1: Investigation Locations and Depths – Stage 1 Land Boreholes

Investigation Locations and Depths – Stage 1 Land Boreholes

Hole ID Location Pre-drilled type Depth drilled [m]

BH01 10 London Street, St Mary’s Bay, Auckland GAP to 1.5m 34.50

BH03 St Mary’s Bay Reserve HA to 1.5m 10.50

BH04 St Mary’s Bay Reserve GAP to 2.0m 15.00

BH05 St Mary’s Bay Reserve HA to 1.5m 12.00

BH06 29 Ring Terrace, St Mary’s Bay, Auckland GAP to 1.85m 25.15

BH07B Walkway between St Mary’s Reserve and Point Erin Park HA to 1.5m 15.05

BH8 Lower Point Erin Reserve, c. 50m East of Northbound Motorway On-ramp HA to 1.6m 15.10

BH09A Embankment between Curran St. and Northbound Motorway On-ramp HA to 1.5m 10.62

Table 4-2: Investigation Locations and Depths – Stage 2 Land Boreholes

Investigation Locations and Depths – Stage 2 Land Boreholes


BH20 Corner London & New Street GAP to 1.5m 4.95

BH21A 27 New Street, St Mary's Bay GAP to 1.5m 12.5

BH21B 27 New Street, St Mary's Bay GAP to 1.5m 6.00

BH23 St Mary's Bay Reserve GAP to 1.3m 15.10

BH24 St Mary's Bay Reserve GAP to 1.7m 12.36

BH25 29 Ring Terrace GAP to 1.5m 10.00

BH26 Point Erin Park - 15.10

BH27 Point Erin Park - 15.13

BH28 Curran Street GAP to 1.7m 10.64

BH30 Sarsfield Street GAP to 1.5m 15.05

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Table 4-3: Investigation Locations and Depth – Stage 2 Marine Boreholes

Investigation Locations and Depths – Stage 2 Marine Boreholes

Hole ID Location Depth drilled [m]

MA01 Marine - Between Masefield Beach and Harbour Bridge 15.00



Table 4-4: Investigation Locations and Depths – Stage 2 Cone Penetration Tests

Investigation Locations and Depths – Stage 2 Cone Penetration Tests


CPT20 St Mary's Bay Reserve GAP to 1.5m 10.44






Table 4-5: Investigation Locations and Depths - Stage 2 Service Investigation Trenches

Investigation Locations and Depths – Stage 2 Service Investigation Trenches

Hole ID Location Purpose Depth drilled [m]

RA04 Curran Street To positively locate service trenches 3

RA05 Point Erin Park To positively locate service trenches 3.5

RA06 Curran Street To positively locate service trenches 3

RA07 Point Erin Park To positively locate service trenches 3.5

4.2 Pre-Drill As discussed in earlier sections, pre-drilling activities by a specialist road-opening contractor were carried out to facilitate utility avoidance and protection, and to streamline the geotechnical drilling programme. The arrangement improves safety, facilitates programme control, and minimises downtime.

For the sites on the road or pavement a full Ground Access Portal (GAP) was used, comprising pavement cutting, hydro-excavation to 1.5m or more, installation of a 300mm PVC liner (cemented in place), with a heavy-traffic rated access cover cemented in place. Where considered important, pre-

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drill works were supervised by an Aurecon contaminated land specialist who logged the fill material and took environmental samples.

4.3 Rotary Cored Boreholes Geotechnical drilling was carried out using a range of plants to suit the conditions at each site. Details of the plant for each hole are included on the borehole log. Borehole logs, photographs and borehole installations are presented in Appendix B and locations are shown in Appendix A.

4.4 Cone Penetration Tests Six Cone Penetration Tests (CPTs) were carried out in St Mary’s Bay Reserve for the purpose of identifying the existence and extent of an alluvial palaeo-channel in the north-western side of the park. The locations of the CPTs are shown in Appendix A and the results are presented in Appendix B.

4.5 Trenches Four trenches were hydro-excavated for the purpose of identifying services on either side of the Curran Street SH1 on-ramp near Masefield Beach. The locations of these trenches are shown in Appendix A.

4.6 In-situ Testing

4.6.1 Standard Penetration Testing Standard Penetration Testing (SPT) was undertaken in the BH rotary drillholes. The SPT test is an in situ test that measures the number of blows required to penetrate soil or soft rock over a 300mm test increment following a 150mm seating (non-test) increment. The testing was carried out in accordance with EN ISO 22476-3:2005+A1:2011.

The termination criteria for SPT testing was specified on a hole-by-hole basis, but was generally 2 consecutive SPT tests with a penetration resistance of N=50+.

4.6.2 Hand-held Shear Vanes Hand held shear vane tests were carried out in selected core barrels in cohesive soils. Measurements were taken in accordance with the techniques descripted in New Zealand Geotechnical Society (NZGS) Guidelines (NZGS, 2001). The corrected shear strength results and the calibration factor for the shear vane used are reported on the formal logs.

4.6.3 Packer Testing In-situ packer testing was carried out in selected boreholes using a pneumatic (air-inflated) packer. The testing was carried out using a single terminal configuration where the test section is between the up-hole inflated packer (which seals off the test section) and bottom of the hole at the time of testing.

A summary of the packer tests is presented in Table 4-6 below and the test reports are included in Appendix C1 of this report.

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Table 4-6: Summary of Packer Testing

Packer Testing

Borehole Depth Range Groundwater Level Static Head Indicative Geology

BH01 12.5 m - 21.0 m 5.34 m BGL 57.29 kPa EUs2 / EUz2

BH01 29.15 m - 34.5 m 11.94 m BGL 122.04 kPa EUs2 / EUz2

BH04 9.75 m - 15.0 m 0.1 m AGL 15.0 kPa EUs / EUz

BH06 18.85 m - 25.15 m 3.11 m BGL 36.0 kPa EUs / EUz

BH08 9.85 m - 15.1 m 1.45 m BGL 24.1 kPa EUs

4.7 Backfill At the termination of ground investigations, boreholes were backfilled with bentonite to the base level of the monitoring installation (refer to Section 5 and Appendix B3 for details).

No drilling equipment has been left in any of the exploratory holes with only the monitoring installation and associated PVC conduit being left grouted in situ in selected boreholes as per section 5 below.

4.8 Geophysics Geophysical Investigation of the project area was carried out using Ground Penetrating Radar (GPR) and Multichannel Analysis of Surface Waves (MASW) in St Marys Bay Reserve and Bathymetry and Sub-Bottom Profiling in the harbour off Masefield Beach. The geophysics report is presented in Appendix E1.

4.8.1 Land Geophysics Invasive investigations at St Mary’s Reserve were supplemented by geophysical techniques. Two types of geophysical profiling were run, investigating shallow (<5m) and deeper conditions respectively. 9 GPR lines were carried out in St Marys Bay Reserve. 1 MASW profile targeted deeper layers, with the aim of confirming the existence (or otherwise) of a sediment filled paleo-channel.

Figure 4-1 shows the 9 GPR lines in yellow and the MASW line in red.

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Figure 4-1 – Land Geophysics: 1 MASW (red) line and 9 GPR (yellow) lines

Detailed reporting of the geophysics programme is included in Appendix E.

4.8.2 Bathymetry A detailed bathymetric survey was carried out by Ports of Auckland. The extent of the surveyed area is shown in Figure 4-2 and the report and visualisation of the results are included in Appendix E2.

4.8.3 Marine Geophysics Sub-Bottom profiling was carried out with the same extents as the bathymetry, to investigate the sub-surface conditions in the area of the proposed new marine outfall options. This is reported in Appendix E1.

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Figure 4-2 – Extent of Marine Geophysics (Appendix E1) coincides with extent of Bathymetry (Appendix E2)

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5 Installations 5.1 Introduction Following the completion of drilling at each borehole, PDP hydrogeologists reviewed encountered ground conditions and specified groundwater installation type (vibrating wire or standpipe piezometer) and depth (including screen intervals for standpipe piezometers).

As-built drawings for each installation are provided in Appendix B3.

5.2 Vibrating Wire Piezometers Vibrating Wire Piezometer (VW) installations consisting of a vibrating wire element connected to a sensitive diaphragm have been installed in selected boreholes at various depths.

The vibrating wire transducers and cable was supplied by HMA Geotechnical Systems Australia. Transducers within a 350kPa pressure range were installed in the boreholes at the depths specified. During the installation of the transducers, a series of pre-, during and post- installation measurements were taken to confirm functionality.

Vibrating Wire installation details are shown in Table 5-1.

Table 5-1: Vibrating Wire Piezometer Details

Vibrating Wire Piezometer Details

Borehole Vibrating Wire Traducer Depth (m bgl) Installation Date

Borehole termination

depth (m bgl)

Borehole Elevation

RL (m)

BH04 7.50 m 09/05/2017 15.0 3.35

BH08 9.20 m 15/05/2017 15.1 3.2

5.3 Standpipes Standpipe installations consisting of a 50mm diameter PVC pipe with a slotted section ranging between 2m and 6m long have been installed in selected boreholes.

The standpipes are constructed using PVC pipe with push joint connections. The void between the outside of the standpipe and the borehole has been backfilled.

Standpipe installation details are shown in Table 5-2 and Table 5-3.

Table 5-2: Standpipe Details – Stage 1 Boreholes

Standpipe Details Stage 1 Boreholes

Borehole Pipe

diameter (mm)

Screen Interval Installation

Date Borehole

termination depth (m bgl)

Borehole Elevation RL (m)

Top Bottom

BH01 50 18.0 m bgl 24.0 m bgl 04/05/2017 34.50 21.43

BH03 50 1.6 m bgl 4.0 m bgl 22/05/2017 10.50 3.84

BH05 50 1.0 m bgl 3.0 m bgl 05/05/2017 12.00 3.19

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Borehole Pipe

diameter (mm)


Date Borehole



Top Bottom

BH06 50 15.0 m bgl 18.0 m bgl 28/04/2017 25.15 19.79

BH07B 50 3.0 m bgl 5.5 m bgl 17/05/2017 15.05 4.14

BH09A 50 2.0 m bgl 5.0 m bgl 15/05/2017 10.62 4.74

Table 5-3: Standpipe Details – Stage 2 Boreholes


Borehole Pipe

diameter (mm)


Date Borehole



Top Bottom

BH20 50 1.5 m bgl 4.0 m bgl 20/10/2017 4.95 21.53

BH21A 50 8.0 m bgl 12.5 m bgl 26/10/2017 12.50 22.10

BH21B 50 1.5 m bgl 4.8 m bgl 27/10/2017 6.00 22.33

BH23 50 8.0 m bgl 15.0 m bgl 12/12/2017 15.10 3.67

BH24 50 6.0 m bgl 9.0 m bgl 13/12/2017 12.36 3.26

BH25 50 1.5 m bgl 5.5 m bgl 24/10/2017 10.00 19.63

BH26 50 9.0 m bgl 12.0 m bgl 21/11/2017 15.10 3.52

BH27 50 8.8 m bgl 14.8 m bgl 22/11/2017 15.13 3.41

BH28 50 6.8 m bgl 9.8 m bgl 23/11/2017 10.64 3.05

BH30 50 1.5 m bgl 5.5 m bgl 25/10/2017 15.05 14.04

5.4 Groundwater Monitoring Groundwater measurements were generally taken at various stages during drilling and a vibrating wire or a standpipe was installed in every borehole for ongoing monitoring. Many of the standpipes have also been equipped with a level logger to automatically take readings in order to establish a baseline and seasonal variation. All standpipes have also been manually dipped to calibrate level logger data. Ongoing groundwater records will be reported separately (updated approximately every 3 months).

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6 Laboratory Testing 6.1 Scope A range of classification and strength laboratory testing was undertaken on samples from the ground investigations. This testing focussed on characterisation of soils (younger alluvium, particularly), fill (reclamation material), and rock (unweathered ECBF at proposed tunnel depth).

6.2 Test Register Table 6-1 provides a summary of laboratory testing completed during Investigation Stage 1 and Stage 2, including total scheduled and total reported test results.

Table 6-1: Summary of Laboratory Testing

Summary of Laboratory Testing

Class Test Total scheduled Completed/ Reported

Reference in Appendix D

Classification & Index

Tube Logs 7 7 D2

In Situ Density 5 5 D3

PSD Wet Sieve 10 10 D4

PSD Hydrometer 4 4 D5

Atterberg Limits 13 13 D6

Petrography 4 0 D10

Strength

Triaxial (CU) 2 2 D7

Triaxial (UU) 1 1 D8

Unconfined Compressive Strength (UCS) 16 15* D9

*Laboratory reported sample BH07B 10.21m broke during preparation of the test specimen and could not be tested PSD = Particle Size Distribution; CU = Consolidated Undrained Triaxial; UU = Unconsolidated Undrained Triaxial Table 6-2 provides a summary of the laboratory testing standards that have been used by the laboratory for the testing completed.

20


Table 6-2: Summary of Testing Standards used by Testing Laboratory

Summary of Laboratory Testing Standards

Class Test Test Standard

Classification & Index

Tube Logs NZ Geotechnical Society Guideline 2001

PSD Wet Sieve NZS4402:1986

PSD Hydrometer NZS4402:1986

Atterberg Limits NZS4402:1986

Strength

Triaxial (CU) BS1377:1990

Triaxial (UU) BS1377:1990

UCS NZS4402:1986

6.3 Soil Testing Soil testing was carried out on samples collected across the project area during both stages of ground investigation. Samples include HQ3 core, SPT samples, U54 push-tube samples and loose sand collected and bagged on site.

Classification testing included logging of in situ push-tube contents, bulk density and moisture content, particle size distribution testing using both hydrometer and wet sieve methods, depending on applicability, and Atterberg limits testing. Soil strength testing was carried out in the form of UU and CU triaxial testing.

Table 6-3 provides a summary of the soil testing carried out and results are reported in Appendix D.

Table 6-3: Summary of Soil Testing

Summary of Soil Testing

Classification / Index Strength

Borehole Sample Depth Sample Type1

Tube Log

Bulk Density

PSD Hydrometer

PSD Wet Sieve

Atterberg Limit Triaxial

BH07B 1.3 – 1.5 m MD ✓

BH08 3.0 – 3.45 m U54 ✓ ✓ ✓ ✓ (UU)

BH09A 1.8 – 2.25 m SPT ✓

BH09A 3.0 – 3.45 m SPT ✓

BH20 1.6 – 1.75 m HQ3 ✓

BH20 3.45 – 3.62 m HQ3 ✓ ✓

BH24 1.85 – 1.97 m HQ3 ✓

BH24 11.5 – 11.65 m HQ3 ✓

BH26 3.0 – 3.5 m U54 ✓ ✓ ✓

BH26 13.11 – 13.29 m HQ3 ✓

BH27 7.5 – 7.95 m SPT ✓

21


Summary of Soil Testing

Classification / Index Strength

Borehole Sample Depth Sample Type1

Tube Log

Bulk Density

PSD Hydrometer

PSD Wet Sieve

Atterberg Limit Triaxial

BH27 7.95 – 8.1 m HQ3 ✓

BH27 8.4 – 8.67 m HQ3 ✓ ✓ ✓ (UU)

BH30 4.95 – 5.1 m HQ3 ✓

BH30 5.8 – 5.9 m HQ3 ✓

BH30 6.79 – 7.01 m HQ3 ✓ ✓

BH30 11.41 – 11.52 m HQ3 ✓

MA01 1.45 – 1.65 m HQ3 ✓

MA01 1.7 – 2.2 m U54 ✓ ✓ ✓ (CU)

MA01 2.2 – 2.7 m U54 ✓ ✓ ✓

MA03 0.5 – 1.0 m U54 ✓ ✓ ✓

MA03 1.0 – 1.5 m U54 ✓ ✓ ✓

MA03 2.3 – 2.8 m U54 ✓ ✓ ✓ 1Sample Type: MD = Medium Disturbed sample bag; HQ3 = HQ3 sized rotary core sample; SPT = Standard Penetration Test split spoon sample; U54 = 54mm thin wall ‘Shelby’ push tube PSD = Particle Size Distribution; CU = Consolidated Undrained Triaxial; UU = Unconsolidated Undrained Triaxial

6.4 Rock Strength Testing Unconfined compressive strength (UCS) testing was carried on 21 HQ3 core sized test specimens of ECBF rock taken from core boxes of core. The testing was carried out by Opus Testing Laboratories using a concrete compression testing machine.

The aim of the testing was to characterise typical strength of the tunnel depth and also attempt to determine upper-bound strength for baselining.

UCS Testing results are summarised in Table 6-4 and reported in Appendix D9.

Table 6-4: Summary of Rock Strength Testing

Summary of Rock Strength Testing

Borehole Sample Depth Specimen Depth Sample Type Specimen Description

BH01 19.9 – 20.12 m 19.98 – 20.10 m HQ3 core ECBF Siltstone, very weak

BH01 22.04 – 20.2 m 20.05 – 20.17 m HQ3 core ECBF Siltstone, very weak

BH01 27.0 – 27.47 m 27.1 – 27.22 m HQ3 core ECBF Fine to medium Sandstone, weak, well cemented

BH04 3.89 – 4.1 m 3.97 – 4.09 m HQ3 core ECBF Sandstone, very weak

BH04 5.25 – 5.41 m 5.265 – 5.365 m HQ3 core ECBF Sandstone, very weak

BH04 5.75 – 6.0 m 5.8 – 5.92 m HQ3 core ECBF EUz3 Siltstone, very weak

BH04 13.3 – 13.49 m 13.32 – 13.44 m HQ3 core ECBF EUs3 Sandstone, very weak

BH06 20.12 – 20.36 m 20.19 – 20.31 m HQ3 core ECBF Fine Sandstone, weak, well cemented

BH06 20.63 – 20.86 m 20.68 – 20.8 m HQ3 core ECBF Fine Sandstone, weak, well cemented

22


Summary of Rock Strength Testing

Borehole Sample Depth Specimen Depth Sample Type Specimen Description

BH06 21.87 – 22.02 m 21.89 – 22.01 m HQ3 core ECBF Fine to medium Sandstone, very weak, well cemented

BH07B 6.63 – 6.77 m 6.64 – 6.76 m HQ3 core ECBF Siltstone, extremely weak

BH07B 8.94 – 9.1 m 8.98 – 9.095 m HQ3 core ECBF Fine Sandstone, extremely weak

BH08 4.22 – 4.5 m 4.3 – 4.42 m HQ3 core ECBF Fine Sandstone, very weak, well cemented

BH08 5.27 – 5.43 m 5.29 – 5.41 m HQ3 core ECBF Fine Sandstone, very weak, well cemented

BH08 6.95 – 7.13 m 7.0 – 7.12 m HQ3 core ECBF Fine to medium Sandstone, very weak, well cemented

BH08 12.41 - 12.57 m 12.42 – 12.54 m HQ3 core ECBF Sandstone Unweathered 'strong'

BH08 13.5 – 13.69 m 13.51 – 13.63 m HQ3 core ECBF Sandstone Unweathered “very weak”

BH08 14.07 – 14.31 m 14.07 – 14.27 m HQ3 core ECBF Sandstone Unweathered “weak”

BH26 12.88 – 13.11 m 12.89 – 12.97 m HQ3 core ECBF Sandstone Unweathered “very weak”

BH30 12.10 – 12.77 m 12.11 – 12.23 m HQ3 core ECBF Siltstone “very weak”

MA03 8.2 – 8.48 m 8.21 – 8.33 m HQ3 core ECBF Silty fine Sandstone Slightly Weathered

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7 Contamination Testing 7.1 Scope of Contamination Testing Contamination testing details and results are reported and discussed in the Detailed Site Investigation report (Aurecon (2018). St Marys Bay - Detailed Site Investigation). Soil samples were collected from selected investigatory positions as presented in Table 7-1. Samples were sent to Hill Laboratories, an IANZ-accredited laboratory, and selected samples were scheduled for analysis in order to characterise soils to be disturbed during construction of the proposed tunnel.

Additionally, groundwater samples were collected from BH03, BH05, BH07, and BH09A to characterise potential contamination of groundwater in the vicinity of reclamation fill.

7.2 Schedule of Contamination Testing A summary of the soil samples taken and analysed for the purpose of contamination testing is presented in Table 7-1.

Table 7-1: Schedule of Contamination Testing Samples

Hole ID Location Depth below

ground level (m)

Contamination Samples Collected

Contamination Samples Analysed

BH01 10 London Street, St Mary’s Bay, Auckland 34.50 2 1

BH03 St Mary’s Bay Reserve 10.50 6 5



BH06 29 Ring Terrace, St Mary’s Bay, Auckland 25.15 0 0

BH07B Walkway between St Mary’s Reserve and Point Erin Park 15.05 4 2

BH8 Lower Point Erin Reserve, c. 50m East of Northbound Motorway On-ramp

15.10 5 3

BH09A Embankment between Curran St. and Northbound Motorway On-ramp 10.62 4 3

BH20 Corner London & New Street 4.95 1 1

BH21A 27 New Street, St Mary's Bay 12.5 0 0

BH21B 27 New Street, St Mary's Bay 6.00 0 0

BH23 St Mary's Bay Reserve 15.10 3 3

BH24 St Mary's Bay Reserve 12.36 0 0

BH25 29 Ring Terrace 10.00 0 0

BH26 Point Erin Park 15.10 0 0

BH27 Point Erin Park 15.13 1 1

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Hole ID Location Depth below

ground level (m)

Contamination Samples Collected

Contamination Samples Analysed

BH28 Curran Street 10.64 3 3

BH30 Sarsfield Street 15.05 0 0

Soil samples were scheduled for the following analytical suites, as deemed appropriate for the known history of the site:

▪ Total petroleum hydrocarbons (TPH);

▪ USEPA16 Polycyclic aromatic hydrocarbons (PAH);

▪ Volatile organic compounds (VOC);

▪ Heavy metals (arsenic, cadmium, chromium, copper, lead, mercury, nickel, and zinc); and

▪ Asbestos presence/absence screen.

Groundwater samples were scheduled for the following analytical suites:

▪ Total petroleum hydrocarbons (TPH);

▪ USEPA16 Polycyclic aromatic hydrocarbons (PAH);

▪ Heavy metals (arsenic, cadmium, chromium, copper, lead, mercury, nickel, and zinc); and

▪ General water quality analysis:

pH

Electrical conductivity

Total alkalinity

Total suspended solids

Chloride

Salinity

Total hardness

Sulphate

Cations

Nutrients

Langalier Index

Analytical results, chain of custody forms, and interpretation of results are reported separately in the Detailed Site Investigation (DSI) Report.

25


8 Limitations This report has been prepared in accordance with the brief as provided. The contents of the report are for the sole use of the Client (Auckland Council). No responsibility or liability will be accepted to any third party. Data or opinions contained within the report shall not be used in other contexts or for any other purposes without prior written agreement of Aurecon New Zealand Limited.

The information in this report is based on data collected at specific locations and by using appropriate investigation methods within the limits of specific site constraints. Only a finite amount of information has been collected to meet the specific financial and technical requirements of the Client’s brief and this report does not purport to completely describe all the site characteristics and properties.

The nature and continuity of the ground between test locations has been inferred using experience and judgment and it must be appreciated that actual conditions could vary from the assumed model.

Subsurface conditions relevant to construction works should be assessed by contractors who can make their own interpretation of the factual data provided. The contractors should perform any additional tests as necessary for their own purposes. Subsurface conditions, such as groundwater levels, can change over time. This should be borne in mind, particularly if the report is used after a protracted delay.

This report is not to be reproduced either wholly or in part without prior written permission from Aurecon New Zealand Ltd.

26


9 References American Society of Testing and Materials (2011). ASTM D3080 / D3080M - 11 – Standard Test Method for Direct Shear Test of Soils under Consolidated Drained Conditions. American Society of Testing and Materials. Aurecon (2018). St Marys Bay - Detailed Site Investigation. Auckland. Aurecon (2016). St Marys Bay CSO – Technical Memorandum: Hackett-Sarsfield Diversion Geotechnical Concept Study. Auckland. Aurecon (2016). St Marys Bay CSO – Technical Memorandum: Geotechnical Desktop Study for Disinfection Plant Concept. Auckland. British Standard Institute (2011): BS EN ISO 22476-3: 2005+A1: 2011 – Geotechnical Investigation and Testing – Field Testing – Standard Penetration. British Standards Institute. British Standard Institute (1990): BS 1377: Methods of Test for Soil for Civil Engineering Purposes. British Standards Institute. Kermode, L.O (1992). Geology of Auckland Urban Area. Scale 1:50,000, Institute of Geological and Nuclear Sciences geological map 2. 1 sheet + 63p. Lower Hutt, New Zealand. Institute of Geological and Nuclear Sciences Limited. New Zealand Geotechnical Society. (2005). Field Description of Soil and Rock – Guideline for the Field Classification and Description of Soil and Rock for Engineering Purpose. Wellington. New Zealand Geotechnical Society. (2001). Test method for determining the vane shear strength of a cohesive soil using a hand held shear vane. Wellington. New Zealand Standard. (1986). New Zealand Standard 3910: 2003 – Conditions of Contract for Building and Civil Engineer Construction. Wellington. New Zealand Standard. (1986). New Zealand Standard 4402: 1986 – Methods of Testing Soils for Civil Engineering Purposes. Wellington.

Technical Report Geophysical Survey Report Masefield Beach / St Marys Bay Project: AU867 Client: Aurecon / Auckland Council Location: Masefield Beach, St Marys Bay,

Auckland Date: April-June 2017 Technical Staff: Matt Watson

James McHardy Kirsty Hamlin

Release Date: 28/06/17

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CONTENTS 1.0 Introduction 1.1 Scope of Survey 2.0 Survey Methodology 2.1 Sub Bottom Profiling (SBP) 2.2 Sidescan Sonar 2.3 MASW and Ground Penetrating Radar (GPR) 3.0 Results 3.1 Masefield Beach – marine geophysical surveys 3.2 St Marys Bay – land geophysics

4.0 Summary LIST OF FIGURES Figure1 Figure 2a Figure 2b Figure 2c Figure 2d Figure 2e Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 APPENDIX Sidescan Sonar Data (KMZ)

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1.0 Introduction ScanTec Ltd was requested by Aurecon to provide geophysical measurements at Masefield Beach and St Marys Bay, Auckland, as part of a geotechnical investigation for the positioning and design of a sewerage pipeline. Two marine geophysical techniques were used for the work at Masefield Beach,

1) Sub Bottom Profiling (SBP), for measuring mud thickness and depth to bedrock 2) Sidescan sonar, to provide an image of the seabed.

Two land geophysical techniques were used at St Marys Bay,

1) Ground Penetrating Radar (GPR) 2) Passive MASW (multi-spectral analysis of surface waves)

Field work was carried out by Matt Watson (Geophysicist), James McHardy (Technician) and Kirsty Hamlin (Geologist) between April and May 2017.

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2.0 Survey methodology 2.1 Sub Bottom Profiling (SBP) A Raytheon PTR-106 Sub-bottom profiling system and 24bit ADC controller were used for SBP data acquisition. The 3.5KHz and 7kHz transducer was mounted off the bow of the vessel (Figure iv). Measurements were synchronized with the Trimble / Omnistar DGPS data. Measurements were recorded at a boat speed of between 2knot (confined areas) and 3knots. Multiple runs were recorded over some lines using different acquisition settings to obtain optimum results (Figure iv). The PTR-106 is a high resolution seismic (acoustic) system that transmits a high power (2kW) 3.5kHz to 7kHz frequency pulse stream into the water which has sufficient energy to penetrate deep into mud and sediment. The sonar equipment was connected to a digitiser in order to continuously log data in seismic binary format (SEGY) and stored on a laptop PC. The sonar data files were synchronised with Fugro Omnistar DGPS readings. Output power and receiver gain levels had to be carefully controlled due to the very shallow water. Some problems were also experienced with strong tidal flow perpendicular to the measurements direction. Figure iv shows the equipment used and its setup during the survey. Time variable gain (TVG) and bottom ramp functions were used to optimise the gain settings and minimise the ringing effect due to the very shallow water. A 200kHz transducer was also used to provide high resolution bottom readings and control the gain ramp functions of the 3.5kHz signal. SBP data processing All measurements were processed using REFLEX-W seismic processing software, RADAN 6.5 and SURFER v10. Data processing involved; • converting from SEG-Y to SEG2 and DZT format • high and low pass frequency filtering • linear gain ramp • horizontal background removal • predictive deconvolution Positional and height datum Positional and depth data are presented in NZTM 2000 and Auckland chart datum.

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2.2 Sidescan Sonar A sidescan sonar survey was carried out in the requested area using a Tritech dual channel towfish, at 450kHz frequency. Multiple passes were made at gradually increasing offsets from the shore to create a mosaic of overlapping swaths. Swath width was approximately 20m each channel and the sonar fish was towed at an elevation above the seabed of approximately 1-3metres. Acquisition speed was very slow at approximately 1-2 knots to maximize the resolution and sampling. Positions for the survey were continuously acquired using Fugro/Omnistar DGPS. 2.3 Ground Penetrating Radar (GPR) Ground penetrating radar (GPR) measurements were carried out using a GSSI SIR-3000 system with 200MHz and 400MHz frequency antennae. A combination of Differential GPS (DGPS), digital survey wheel and survey tapes were used for position control. Measurements were recorded at 24-bit resolution and a sampling density of 100scans per metre. Measurements were recorded in a series of 2D profiles towed manually. GPR Data Processing GPR data was processed in RADAN 6.6 software. Processing involved bandpass HP/LP filtering, predictive deconvolution, stacking, gain adjustments and background removal.

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2.4 Multispectral Analysis of Surface Waves (MASW) Equipment, measurement and data processing procedures A Geometrics Geode 24-channel (24-bit) digital seismograph was used with 14Hz geophones at 3m spacing. The seismic line orientation is shown on Figure 2. The measurement procedure followed published US guidelines for refraction microtremor (ReMi) testing (Optim, Inc. 2008) to produce shear wave profiles. Ambient background noise levels were used for this survey which included trucks, cars, heavy machinery, and the like. These were enhanced by hammer blows at intervals along each seismic line. Measurement windows were 30seconds duration at 2ms sample interval. Between ten windows were collected for each seismic spread. Data was recorded in SEG-Y format.

Figure i). Photos showing a passive MASW survey in progress using vibrations from vehicle traffic on the Motorway (to left of barrier) as a seismic source.

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Data processing was carried out in SeisOpt ReMi Version 4.0. This included;

• conversion SEG-2 data, • pre-processing (filtering), • Creating a velocity spectrum image (p-f) (frequency vs slowness) (Figure ii) • Manually picking a dispersion curve for each spread. (Figure iii) • Creating a velocity model using SeisOpt Disper Module (Figure iii), and • importing the dispersion curve from the p-f image to model the shear wave velocity for

each spread. • Creating a vertical shear wave profile (2D seismic cross-section)

Figure ii) Image showing the spectral ratio and dispersion curve for a single spread (Slowness vs Frequency vs spectral ratio).

Figure iii). Screenshot example of dispersion curve / velocity profile modelling procedure. The velocities and layer depths are adjusted manually to fit the each dispersion curve (line of red dots), with particular emphasis on the inflection points and gradients of each section

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3.0 Results 3.1 Masefield Beach (Marine Geophysical Survey)

Sub Bottom Profiling The SBP track lines used for the final processing are shown on Figure 1. More SBP lines were recorded (approximately double the amount shown). Gain adjustments and pulse width adjustments were made during the survey to enhance the penetration, so only the later lines were used in processing, with the maximum depth penetration. Each processed SBP line was interpreted and digitized to obtain XY coordinates and Z1 (depth of seabed), Z2 (reflector depth at base of sediment). This is carried out manually, within the software. The coordinates were used to generate a map showing interpreted sediment thickness above Waitemata Group reflection (Figure 2). A sample of the SBP lines are shown as an example of the data (Figures 2c, 2d, 2e) Observations

• Paleochannels are observed, eg SBP Line section AB, EF, CD (Figure 2), with example below. Typically, stronger reflection returns are observed within the channels relating to contrasting density of Pleistocene sediments (see below). The base of the channel is indistinct and undulating (not to be confused with the multiple of the seabed reflection).

Figure iv) example of SBP data showing paleochannel.

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• The SBP indicates two areas where mud thickness increases (see Figure 2). Area A

is interpreted as a paleochannel running in part beneath the current channel (see bathymetry map Figure 4). Mud thickness increases significantly to the south. (See section HBR-16-W, Figure 2d)

• Another area of thicker sediment (Area B) is interpreted extending into the main Harbour channel, near the Harbour Bridge (Figure 2). Reflection strength in this area was weak and also SBP measurements were complicated due to the changing bathymetry (edge of the slope). It is possible that reflection signature interpreted as sediments is very similar to that of weathered Waitemata Gp. The interpretation of a paleochannel is uncertain at this location, and it may be more likely to be due to extensive weathering.

• Over the coverage area, the interpreted sediment thickness varies between 0.5m and

10m. It is not possible to record sediment thickness less than approximately 0.5m with the equipment used, as the resolution at 7kHz frequency is too low.

• Dipping bedding in the Waitemata Group can be identified, which is useful for

interpretation purposes.

• Calibration with drill holes is recommended to increase confidence in the SBP interpretation and provide velocity control for more accurate depths.

Bathymetry Bathymetry for this area is shown in Figure 4 which was used in the processing of the SBP data. 3D projections with a vertically exaggerated depth scale (Z axis) are also provided (Figure 5), which can help in visualizing the shape of the seabed, and any features that may influence the current flow.

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Sidescan Sonar The sidescan sonar data is provided as KMZ files, which can be viewed at high resolution in Google Earth (freeware). The KMZ files are included in the digital appendix. Just click on the KMZ file to open in Google Earth. A low resolution sidescan sonar mosaic is shown as Figure 6. Features observed

• Very large sand ripples (Megaripples) are observed in an isolated area on the seabed (see Figure 2,3 for location). These were measured at up to 500cm-850cm between peaks and indicate that strong seabed currents are experienced due to wave and/or tidal activity. This may have implications for the positioning of outfall.

• Intertidal reef (This can also be observed on aerial photos at low tide). • Cables lying on seabed (can be observed at low tide)

(Figure v) example of megaripples.

• Isolated objects are visible on the seabed. The example shows the largest observed, at approximately 13m length, 3m width. Location is -36.834505, 174.740057. This may be a partially buried wreck.

(Figure vi) example of angular structure on seabed. Position -36.834265, 174.740136 WGS-84.

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3.2 St Marys Bay (Land Geophysical Survey)

The processed GPR images are provided as Figures 1 and 2. The location of all lines is indicated by the inset map. GPR Lines 1,2,3 (Figure 7) are sub-parallel to the motorway. GPR Lines 4,5,6,7,8,9 (Figure 8) are shorter lines, mainly starting at the footpath and ending at the cliff. GPR Observations

• GPR maximum signal penetration approximately 2-3m. • Undulating conductive fill reflections throughout. • Dipping reflections from ECB formation observed on lines perpendicular to cliff face.

(eg GPR 7, GPR8, Figure 8) • Isolated stronger reflections from buried debris or covered objects, possibly relating

to the old boat slipway Passive MASW Results Results from the passive MASW seismic line are shown as Figure 9, with the location of the line AB indicated on the inset map. Interpreted shear wave velocities (Vs) are indicated by the colour scale and the observed range is approximately 200m/sec to 2000m/sec. The interpreted fill thickness overlying the higher velocity material (East Coast Bays formation) is 5m at 40m line distance (SE from position A). This increases to an interpreted thickness greater than 10m at 90m line distance, which is approximately at the centre of the former bay. Generally, a layer of low velocity material (200-500m/sec) is present over the entire profile to a depth of 4-5metres corresponding to weak fill. Shear wave velocities of the fill are between approximately 200-1200m/sec, weathered ECB 1200-1700m/sec increasing to 2000m/sec+ for unweathered ECB.

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4.0 Summary / Recommendations A map showing interpreted sediment thickness has been generated by the marine SBP grid line dataset. The SBP measurements identified a paleochannel in the Waitemata Gp basement (area A, Figure 2) and possibly evidence of a second paleochannel (area B, Figure 2). The thickness of Pleistocene sediment is interpreted at up to 10m in the channel sediments (Area A). Reflection patterns at Area B which have been interpreted as palochannel sediment may also be due to increased weathering of the Waitamata Group. Clarification would be required using drilling. This section is also complicated due being positioned on the edge of to the slope into the main Auckland Harbour channel. Sidescan sonar (Figure 6) indicated an area of large ripples on the seabed (megaripples), some between 5m-8m peak to peak, which may indicate stronger currents in this localized area. GPR survey work (Figure 7,8) at St Marys Bay identified fill thickness and areas where coarse debris is located. Passive MASW measurements (Figure 9) provided shear wave velocity of the sediments in a 120m transect parallel to the motorway. A layer of low velocity material (200-500m/sec) to 4-5m depth overlies weathered ECB formation (1200-1700m/sec) and unweathered ECB >2000m/sec. Recommendations for additional work Drilling is recommended for velocity calibration used in SBP data interpretation. Depths to ECB interpreted from the MASW line (Figure 9) should be correlated with drill hole logs. Please let us know if you have any questions relating to this technical report. Matt Watson B.Sc. M.Sc Geophysicist ScanTec Ltd [email protected] ph 021-376-644

mailto:[email protected]

REPORT OF SURVEY

SURVEY LOCATION: Auckland Harbour. An area north of Masefield Beach, extending west to Watchman

Island and eastwards under the Harbour Bridge.

SURVEY DATE: 16th and 17th February 2017

REASON FOR SURVEY: Investigative site survey for the routing of a proposed outfall pipeline.

CLIENT: Auckland Council

WEATHER: Wind SW 10 knots, Sea generally calm, fine weather. Wave chop (0.1m-0.2m) with wind against

tide on the afternoon of the 16th February.

VESSEL AND EQUIPMENT (incl. software): POAL survey vessel ‘Acheron’ with standard equipment, and

Hydropro navigation and data acquisition software.

POSITIONING SYSTEM AND DATUM: POAL Trimble SPS852 GNSS Receiver. Differential corrections

provided by OmniSTAR HP broadcast. The survey was conducted on NZGD 2000, Mt Eden Circuit Grid 2000. All

data is logged directly to an onboard PC using Hydropro survey software.

ECHO SOUNDER AND TRANSDUCER DETAILS: Odom 3200 Echotrac Mk III, with in-built hull mounted

200kHz transducer.

TIDES AND DATUM: Auckland tides, Auckland Chart Datum.

CONDUCT OF SURVEY:

5m line spacing to cover the complete survey area, with 50m cross (check) lines run perpendicular to these.

ESTIMATED ACCURACY: Positioning +/-0.6m, echo sounder +/-0.12m.

COMMENTS AND RESULTS:

1. The survey was completed without incident apart from increasing wave chop on the afternoon of the 16th

February. This curtailed surveying for that day. The survey was completed on the morning of the 17th February

in calm, fine conditions once again.

2. All soundings have been reduced to Chart Datum using tide readings (1 minute interval) from the PoAL

automatic tide gauge located at Captain Cook Wharf.

3. The minimum and maximum reduced depths recorded during the survey are a drying height of 1.61m and a

depth of 13.53m.

4. The survey shows a gently sloping shelf falling away from Masefield Beach, the Curran Street seawall and the

western Westhaven breakwater into a deeper channel to the north. There are some patches of rocky reef close

to the seawall and the Masefield beach area.

Regards

David Bate

Hydrographic Surveyor,

Ports of Auckland Limited

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BH01 398634.511 803974.619 21.434

BH03 398443.501 804082.200 3.837

BH04 398397.084 804096.495 3.351

BH05 398349.864 804156.068 3.192

BH06 398239.921 804266.215 19.790

BH07B 398037.910 804491.783 4.144

BH08 397888.127 804628.827 3.204

BH09A 397810.299 804598.963 4.736

STAGE 2

EASTING NORTHING HEIGHT

BH20 398643.737 803967.920 21.529

BH21A 398657.401 803957.396 22.099

BH21B 398656.753 803956.422 22.333

BH23 398408.816 804100.435 3.665

BH24 398371.643 804136.205 3.262

BH25 398238.498 804269.382 19.633

BH26 397931.420 804638.484 3.515

BH27 397925.458 804674.845 3.405

BH28 397818.976 804671.900 3.049

BH30 397897.420 804340.831 14.038

CPT20 398366.519 804137.092 3.164

CPT21 398375.269 804133.210 3.240

CPT22 398386.130 804124.805 3.315

CPT23 398399.230 804119.374 3.739

CPT24 398371.174 804135.338 3.192

CPT25 398361.032 804140.408 3.195

MA01 397680.163 805060.071 -4.00

MA02 397771.574 804800.959 -2.20

MA03 397725.308 804910.014 -2.20

RA04 397815.000 804661.000 2.80

RA05 397902.000 804640.000 3.20

RA06 397824.000 804661.000 2.90

RA07 397944.000 804652.000 3.50

BH03 TO BH08 ACCURACY OF 30mmBH01 AND BH09A ACCURACY OF 200mm

CPT22

BH01BH03

BH04BH05

BH06BH07BH08

BH09A

LEGEND:

STORAGE TUNNEL

SHAFT LOCATION

STAGE 1 BOREHOLE LOCATION

STAGE 2 BOREHOLE LOCATION

WASTEWATER PIPE LINE

PROPOSED MARINE OUTFALL

PROPOSED WASTEWATERMANHOLE

MANA WHENUA OVERLAY

S S

RA04BH28

RA06

RA07

BH26

BH27

RA05

MA02

MA03

MA01

BH30

Documents

Ground Investigation Factual Report and Geotechnical Long … · 2018-05-17 · Beca // 2 May 2018 4216571 // NZ1-15242655-52 0.52 // page 135 Appendix F Ground Investigation Factual