America s Cup Geotechnical Report

Transcription

1 Report America s Cup Geotechnical Report for Resource Consent Application, Wynyard Hobson Prepared for Panuku Development Auckland and Ministry Business, Innovation and Employment Prepared by Beca Ltd (Beca) April 2018

2 Revision History Revision Nº Prepared By Description Date 1 Nicola Ridgley Draft Issue for Comment Nicola Ridgley Issued for Consent Document Acceptance Action Name Signed Date Prepared by Nicola Ridgley Reviewed by Jason Anderson Approved by Stephen Priestley on behalf of Beca Ltd Beca 2017 (unless Beca has expressly agreed otherwise with the Client in writing). This report has been prepared by Beca on the specific instructions of our Client. It is solely for our Client s use for the purpose for which it is intended in accordance with the agreed scope of work. Any use or reliance by any person contrary to the above, to which Beca has not given its prior written consent, is at that person's own risk.

3 Executive Summary A desktop review of existing geotechnical information reveals that rock is located at varying depths across the reclamation and harbour, and is underlain by varying thicknesses of fill, Recent Marine Sediments and Tauranga Group sediments. a. Hobson and Wynyard Wharves and Breakwaters The new maritime structures can be supported on piles embedded into the underlying rock. The greater depth of rock at some locations (-15 to -20 m CD) will be a consideration for the use of precast piles or cast in situ piles with permanent steel casings. b. Wynyard Landside Existing perimeter structures at Wynyard Point and adjacent to Wynyard Wharf have low static factors of safety. The underlying soils may also be susceptible to liquefaction during an ultimate limit state (ULS) earthquake resulting in seismic lateral and vertical displacements. Any new structure adjacent to land may require ground stabilisation/improvement works, such as cement-stabilised columns with raft or stone columns, or construction of large diameter piles. Construction of ground improvements may necessitate the removal of existing structures. In addition, a review of the liquefaction potential of the reclamation and underlying soils around Wynyard Point and Wynyard Wharf undertaken in early January 2018 confirmed the potential for liquefaction. The need for stabilisation of the Wynyard Quarter seawalls was already identified prior to the America s Cup development. The stability of the structures needs to be addressed before development of this northern part of Wynyard Quarter is significantly advanced. A legacy of the America s Cup project is to initiate this work, advancing stabilisation of some sections of the seawall. This may potentially facilitate future development, notably in the location of the temporary bases following removal. New building structures located on the reclamation may need to be piled where the effects of ground settlement are not acceptable. c. General Commentary Further geotechnical investigations are recommended at all proposed development sites to confirm depth to rock and depth and strength of overlying soils for detailed design of the proposed structures. It is recommended that either the rock level at every second pile location be identified to optimise pile lengths or piles are cast longer and designed to be cut down where precast piles are selected. Further site specific investigations, analysis and assessment are also recommended as part of the design process in order to determine the most appropriate and cost-effective approach to mitigate the liquefaction potential. Geotechnical investigations are likely to comprise machine boreholes and cone penetrometer tests undertaken either from a barge within the harbour or from existing reclamation and wharf structures.

4 Contents 1. Introduction Report Context Purpose of Report Report Structure Proposed Use and Development Site Description Previous Investigations Geology Geology Seismic Setting Geotechnical Conditions Hobson and Wynyard Wharves and Breakwaters Wynyard Point Geotechnical Parameters Geotechnical Considerations Hobson and Wynyard Wharf and Breakwaters Wynyard Point Conclusions and Recommendations Hobson and Wynyard Wharves and Breakwaters Wynyard Point Further Geotechnical Investigations Applicability Statement Appendices Appendix A Previous Geotechnical Investigations

5 1. Introduction 1.1 Report Context Panuku Development Auckland (Panuku), as Auckland Council's lead delivery agency, has been tasked with providing waterfront infrastructure to host the America s Cup Events and associated regattas in Auckland. The Crown has agreed to provide significant funding to support the hosting of the Events in Auckland. The Ministry of Business, Innovation and Employment (MBIE) is the Crown's lead business-facing agency, responsible for New Zealand Major Events. Beca Limited (Beca) has previously been commissioned by Panuku to prepare reports for the initial A36 Wynyard Basin application and corresponding Ferry and Fishing Industry Relocation Facility. Beca has now been commissioned by Panuku and MBIE to undertake technical studies and engineering concept drawings in relation to the new proposal, called "Wynyard Hobson". Consents are sought for the use and development associated with holding the 36th America s Cup in December 2020 to May 2021 and any subsequent events within a 10 year period (each over a six-month event period), and to construct, use and operate up to seven syndicate bases within the 10 year period. The seven America s Cup bases are proposed in and around Freeman s Bay, which is located along part of Auckland s City Centre waterfront. This includes Wynyard Point, Hobson Wharf, a 74m extension to Hobson Wharf, Halsey Wharf (comprising the Halsey Street Extension Wharf and Western Viaduct Wharf) and Wynyard Wharf, including the surrounding land and water space // // page 1

6 Figure 1: Aerial photo showing the Wynyard Quarter Figure 2: Proposed infrastructure // // page 2

7 For the purpose of the RMA assessment, the effects have been assessed on the basis that the two bulk liquid operators where Bases E, F and G are proposed have vacated the sites in advance of the event. The proposal is made on the basis that part of Brigham Street will be permanently stopped. This will be achieved through a separate process. For the purpose of the RMA assessment, the effects of the road closure including works in the road have been assessed, but not the effects of the proposal on the road as it currently exists. The proposal includes a new road connection north of syndicate Base C to maintain a connection between Brigham Street and Hamer Street. To support this resource consent application, Beca has prepared a suite of reports and drawings: America s Cup Wynyard Hobson Physical Infrastructure Technical Report. America s Cup Wynyard Hobson - Geotechnical Report. America s Cup Wynyard Hobson - Groundwater Technical Report. America s Cup Wynyard Hobson - Preliminary Site Investigations (Contamination) and Draft Remediation Action Plan. America s Cup Wynyard Hobson - Coastal Processes and Dredging Technical Report. America s Cup Wynyard Hobson - Stormwater and Services Technical Report. America s Cup Wynyard Hobson - Traffic and Transport Technical Report. America s Cup Wynyard Hobson - Fire and Evacuation Assessment. America s Cup Wynyard Hobson - Marine Traffic Survey. America s Cup Wynyard Hobson - Engineering Concept Drawings. Each of the individual technical reports should be read in conjunction with the pack of Engineering Concept Drawings to which reference is made as applicable. Reports by other specialists for the resource consent application cover: Landscape, visual impact and natural character (Boffa Miskell). Urban design (McIndoe Urban). Ecology, sediment and water quality (Golder Associates). Noise and vibration (Marshall Day Acoustics). Navigation and recreational vessels (Navigatus). Environmental risk (Sherpa Consulting). Hazardous substances (4Sight) Planning (Assessment of Environmental Effects) (Unio Environmental). 1.2 Purpose of Report The purpose of this report is to provide a summary of the existing geotechnical conditions at the relevant sites, using existing available information. The geotechnical information contained in this report informs the concept design of the America s Cup activities and identifies further geotechnical investigations for this purpose. 1.3 Report Structure This report considers and has been informed by the above technical studies and provides an overview of key aspects relevant to the design. For brevity, detailed technical content has not been replicated and reference is made to the individual technical reports. This report is structured as follows: Section 1: Introduction outlines roles, the reporting context and gives an overview of proposed development. Section 2: Site Description gives the general setting for the proposed development. Section 3: Previous Investigations lists the previous geotechnical investigations in the area (see also Appendix A) // // page 3

8 Section 4: Geology gives an overview of the local geology and seismic setting. Section 5: Geotechnical Conditions describes the ground conditions at the development sites including material properties. Section 6: Geotechnical Considerations describes the potential geotechnical issues and design requirements Section 7: Conclusions and Recommendations summarises key findings and outlines further geotechnical investigations to inform design Section 8: Applicability Statement Appendix A: Previous Geotechnical Investigations includes a brief outline of previous investigations. 1.4 Proposed Use and Development The proposal involves the following three main elements (as described more fully in the Assessment of Environmental Effects (prepared by Unio Environmental) and as shown in the drawings and outlined in the reports which form part of this application: 1. Use and operation of land and water space associated with the 36 th America s Cup event to be held in the six month period from December 2020 to May 2021 (including pack in and pack out of land based and water based activities/structures) and any subsequent America s Cup event(s) held (with a six month period each) during the 10 year period from the commencement of consent. 2. The use and operation of the syndicate bases (buildings and associated yards on land/wharves and water space) for a period up to 10 years from the commencement of consent. 3. The construction and establishment of the wharves, piles, berths, buildings, other structures, and related works, services and access (including ground improvement works, contamination management, earthworks) including all event related structures and services. The infrastructure will be provided on a temporary and permanent basis, as follows: a. Temporary (up to 10 years) b. Permanent: i. Syndicate base buildings B to G; ii. Use of all syndicate base buildings (including ETNZ use of VEC); iii. Wynyard Wharf wharf infill to be removed (no less than 50%); iv. Event-related structures (up to 6 month(s) for each event period); and v. Marine and Port structures/facilities within the Wynyard Wharf South Water space and Outer Viaduct Harbour. i. A 74m extension to Hobson Wharf including a 35-year CMA occupation permit for this structure; ii. Four new breakwaters located as follows: An 81m breakwater east of Wynyard Wharf (Wynyard east); A 39m and 84m breakwater northwest of Halsey Wharf (Halsey west) A 35m breakwater east of Hobson Wharf (Hobson east) including a 35-year // // page 4

9 CMA occupation permit for this structure; A 42m breakwater south of Hobson Wharf (Hobson south) including a 35- year CMA occupation permit for this structure. iii. Wave panels on Hobson Wharf (including the 74m extension) and Halsey Wharf; iv. Wynyard Wharf wharf infill to remain (up to 50%); and v. Physical modifications to the VEC including the following key changes: Removal of the eastern public access ramp to the northern public viewing deck and replacement with a lift on the western side of the building; Modifications to the eastern façade of the building to construct new doors to facilitate for use as a syndicate base; The addition of a mezzanine floor at the northern end of the building for a sail loft; The addition of a new balcony on the eastern facade // // page 5

10 2. Site Description The site is located within an existing harbour basin, which is bounded on the landward side and to the west by historical waterfront reclamations. The Wynyard Point reclaimed land dates from the 1800s to the 1930s. The reclamations are bordered by seawalls and piled reinforced concrete wharves. The seawalls range from recent post and panel seawalls at North Wharf (completed in 2009), Outer Viaduct Harbour and Inner Viaduct Harbour (2000) to the Wynyard Point rock bunds dating from the 1920s. The wharves similarly range in age from Halsey Street Extension Wharf, Western Viaduct Wharf and the extension to Hobson Wharf (2000) to Wynyard and Princes Wharves (1920s-1930s). Base A is located in the existing Viaduct Events Centre on Halsey Street Extension Wharf and Base B is located on an extension to Hobson Wharf. Bases C-G are located on Wynyard Point, bounded by Hamer Street on the western sides and by existing bulk liquid storage facilities (tank farms) to the north and Silo Park to the south. To provide connectivity between the syndicate base buildings and the water loadout area a section of Brigham Street will be stopped and incorporated into the base yard areas. The location of Bases C G has been predominantly used for the storage of bulk liquids but some areas have been cleared of storage tanks and are now used for the parking of cars and general storage. With the existing Stolthaven South and Bulk Storage Terminals (BST) tanks due to be cleared in advance of the tenants vacating, it is anticipated the site will be free of all tanks, foundations and associated pipework prior to construction. The topography of the site is flat with ground levels varying from approximately +5.0 to +5.5 m CD // // page 6

11 3. Previous Investigations A number of previous investigations have been undertaken in and around the site and construction records are available for many of the existing structures. Some of this data is descriptive in nature and therefore primarily of use in defining soil/rock boundaries. Previous investigations have included machine boreholes, Standard Penetrations Tests (SPTs), Cone Penetration Tests (CPT) and prickings. Previous investigations are listed below and a brief summary of these is included in Appendix A: Wynyard Quarter Seawalls Investigation, Beca Ltd for Panuku Development Auckland, North Wall Construction Records, North Wall Investigation, Beca Infrastructure Ltd for Sea+City Developments Ltd, 2007 Halsey St Extension Wharf, Western Viaduct Wharf, New Western Viaduct and Harbour Entrance Protection Wharf Construction Records, Geotechnical Report on Americas Cup 2000 Viaduct Basin Facilities, Beca Carter Hollings and Ferner Ltd for Fletcher Construction Ltd, 1997 Lighter Basin (Americas Cup), Woodward-Clyde for Auckland Regional Services Trust, June 1996 Americas Cup Investigation, Woodward-Clyde for Auckland Regional Services Trust, June 1996 Ports of Auckland Ltd Viaduct Basin Development Site Investigation, Tonkin & Taylor Ltd, January 1991 Proposed Viaduct Basin Development Whitbread Home Base, Beca Carter Hollings & Ferner Ltd, December 1992 Viaduct Basin Development Site Investigation, Tonkin & Taylor Ltd, 25 October 1991 Viaduct Basin Development, Tonkin & Taylor Ltd, 14 August 1991 Viaduct Basin Development Engineering Report, Ports of Auckland Ltd, circa 1990 Freemans Bay Development Dredging and Foundations Investigation, Terra Aqua Consultants for Ports of Auckland Ltd, September 1989 Proposed Dry Dock G55, Gilberd Hadfield for Booth, Sweetman & Wolfe, April 1968 Proposed Dry Dock G46, Auckland Harbour Board, March 1965 Viaduct Basin Development G6B, Auckland Harbour Board, August/September 1962 Cement Jetty Western Viaduct G19, Auckland Harbour Board, March // // page 7

12 4. Geology 4.1 Geology The published geological map of the area (Edbrooke, 2001) indicates that the project area is underlain by construction fill (reclamation), overlying residual soils and rock of the East Coast Bays Formation (ECBF) of the Waitemata Group, also considered to be bedrock in the area. Tauranga Group sediments, not indicated on the map, were also encountered within the site investigations. These comprised Recent Marine Sediments (deposited within the last 12,000 years) and a range of Quaternary sediments (deposited within the preceding 2 million years). The Wynyard Quarter reclamation is 1920s-1930s fill, mostly hydraulically-placed material within a perimeter bund. 4.2 Seismic Setting Tectonic Setting The Wynyard Quarter is situated in an area of New Zealand assumed to have a low seismic hazard. This is due to low historical seismicity and the lack of active, low recurrence interval faults capable of generating large earthquakes in the Auckland region Fault Rupture Hazard The nearest mapped active fault to this part of Auckland (from the Geologic and Nuclear Science Active Faults Database - accessed August 2017) is the Wairoa North fault which is located approximately 27 km southeast of the site in the Hunua ranges. No active faults are mapped nearby and hence the fault rupture hazard is considered to be very low Liquefaction Potential Hydraulic sand fill and sand layers within the Recent Marine Sediments below the water table are expected to be susceptible to liquefaction at relatively low levels of earthquake shaking. However the potential for widespread liquefaction at this site is expected to be limited by the presence of clayey soils and by the moderate levels of shaking considered for design in Auckland. Specific investigations and analysis will be required to assess the susceptibility for liquefaction at each location // // page 8

13 5. Geotechnical Conditions This section outlines the geotechnical conditions at the sites based on the available historic geotechnical investigation data (refer to Section 3). No specific geotechnical investigations have been undertaken for the proposed development at this stage because of the extent of existing information and the compressed timeframe available to prepare this report. A plan of rock contour levels based on historical information has been developed across the project area (refer to Geotechnical Drawing 1). This plan also shows geological profile locations. 5.1 Hobson and Wynyard Wharves and Breakwaters a. Hobson Wharf Extension and Halsey and Hobson Breakwaters The soil profile encountered in the investigations comprises Waitemata Group rock at relatively shallow depths which is overlain in places with residual Waitemata Group soils and Recent Marine Sediments. The geological profile is shown on Geotechnical Drawings 2, 3 and 4. The Recent Marine Sediments were encountered in almost all of the boreholes drilled. Depths of sediment found in the relevant boreholes at that time and immediately adjacent to the original Western Viaduct were around 0 to 1 m thick. These sediments were thicker beneath the remainder of the wharf structures in the area including Hobson Wharf. The average thickness of sediment encountered beneath the existing Halsey Street Extension Wharf, Western Viaduct Wharf and Hobson Wharf was around 3 m. The shear strengths measured during the investigations using hand held Pilcon shear vane ranged between 1 and 16kPa, but were typically 2-6kPa. Residual Waitemata Group soils was only identified in a couple of boreholes. However it is likely that a thin layer (less than 1 m) of Residual soils overlies the Waitemata Group rock. The residual soils typically comprise firm to very stiff silt-clays grading to medium dense to dense sand-silts with depth. The underlying Waitemata Group rock was encountered at depths varying between -5 and -8 m CD in the area of the Halsey Street Extension, Western Viaduct and Hobson Wharves. BH 28 and 29 are located to the north of the existing Western Viaduct and Hobson wharves, rock was encountered within these boreholes at a greater depth of -6.5 m CD and -10 m CD respectively. Rock levels are expected to dip towards the north. b. Wynyard Wharf and Breakwater The soil profile encountered in the geotechnical investigations undertaken in the adjacent Wynyard Point Reclamation comprises construction fill materials over Recent Marine Sediments overlying Tauranga Group alluvial and estuarine sediments, all underlain by Waitemata Group Rock at depths of typically around -15 to -20 m CD. The geological profile is shown on on Geotechnical Drawing 5. Construction fill materials are also likely to be present beneath Wynyard Wharf and may comprise loose boulders from the perimeter rock bunds. Recent Marine Sediments underlie the seabed. These soils comprise fine sandy silt interbedded with loose silty sand and minor shells // // page 9

14 Tauranga Group alluvium was encountered beneath the recent marine sediments, and varied between weak clayey silt to loose to medium dense sand. 5.2 Wynyard Point The Wynyard reclamation was constructed across an old eroded river valley. The soil profile encountered in the investigations comprises construction fill materials over Recent Marine Sediments overlying Tauranga Group alluvial and estuarine sediments all underlain by Waitemata Group Rock. The depth that Waitemata Group rock was encountered was relatively deep at around -15 to -23 m CD. The geological profile is shown on Geotechnical Drawing 5. Construction fill materials were found to vary from hydraulic fill comprising sand, to hydraulic fill comprising silty clay. Sand/gravel and boulders were encountered, these are inferred to be perimeter rock bunds. The varying fill materials are likely to reflect the different stages of construction. Recent Marine Sediments underlie the fill. These soils comprise fine sandy silt interbedded with loose silty sand and minor shells. These soils have been consolidated beneath the fill materials. Tauranga Group alluvium was encountered beneath the recent Marine Sediments, and varied between weak clayey silt to loose to medium dense sand // // page 10

15 5.3 Geotechnical Parameters Typical soil strength design parameters based on experience with past projects are summarised in Table 1 below. Table 1: Material Properties Unit No Geologic Unit Unit Weight ɣ (kn/m 3 ) Undrained Shear Strength (ratio to overburden*) Friction angle φ' (degrees) Cohesion, c (kpa) Peak (kpa) Residual (kpa) 1a Sand (hydraulic) Fill b Silt (hydraulic) Fill (0.27)* 1d 1c 2a 2b 2c Rock Bund * (Sand and gravel with inferred Basalt boulder zones) Recent Marine Sediments (Fine sandy silt with loose silty sand.) Tauranga Group (Upper) (Firm clayey silt and sandy silt) Tauranga Group (Middle) (Loose to medium dense silty fine sand interbedded with clayey silt/gravelly sand) Tauranga Group (Lower) (Medium dense silty fine sand/gravelly sand) (0.08) (0.27)* (0.08) a Waitemata Group * Undrained shear strength expressed as a ratio to overburden stress // // page 11

16 6. Geotechnical Considerations This section discusses the geotechnical considerations for the proposed development. 6.1 Hobson and Wynyard Wharf and Breakwaters The proposed development in this area is to comprise extension of the existing piled wharf structure for Hobson Wharf. At Wynyard Wharf south, infill sections of wharf will span between the existing Wynyard Wharf and the Brigham Street seawall. In addition breakwaters are to extend from Wynyard Wharf, Halsey Wharf Extension and two off Hobson Wharf. The piles for the wharf extensions and wharf infill sections will be founded within the underlying Waitemata Group rock and generally embedded for a depth of 5-10 m. The key geotechnical issue for these structures are the potential variability in depth to Waitemata Group rock including the presence of localised valleys. Localised valleys up to 5 m depth have been encountered in the previous works at Viaduct Harbour. The wharf extensions are located towards the northern edge of a ridge. Therefore, rock level is likely to be variable, becoming deeper towards the north. Rock levels are also deeper in the area of Wynyard Wharf. 6.2 Wynyard Point Static Stability Under static (non-seismic) conditions, previous studies indicate a relatively low level of stability of the reclamation. This is consistent with historical reclamation structures found elsewhere within the region. Typically the outer m of the reclamation have levels of static (non-seismic) stability less than that generally adopted for building platforms Liquefaction and Seismic Stability The potential for reclamation, or parts of it, to be affected by instability due to liquefaction under Ultimate Limit State (ULS) earthquake shaking indicates that some form of liquefaction mitigation and/or slope stabilisation will be necessary to protect structures on or adjacent to the existing reclamation from excessive displacements and/or damage. Therefore, some form of stabilisation will be required to improve the seismic factors of safety (which are low). The approximate area of ground improvement is shown on Civil Drawing 7. This potential risk can be mitigated by several options, either by: Treatment of the soil by ground improvement. Ground improvement options include either a series of piles or stone columns to mitigate against liquefaction or cement-stabilised columns, placed in a lattice pattern to strengthen the soils and mitigate liquefaction. For the cement stabilised columns option, a raft around 2 m thick may be required to reduce the risk of columns reflecting though pavement surface and provide improved performance linking the columns together. Some improvement may also be undertaken using dig out and replace methodology (possibly to remove obstructions). Such treatments would likely extend some 20 m landward of the existing seawall and to depths of 10 to 15 m: or Specifically designing a structure to accommodate the displacement. The new structures may include large diameter piles up to 2 m in diameter and will adopt a displacement-based approach, accommodating seismic-induced movement for egress without collapse. Construction of such ground improvements in this area will likely necessitate the removal of existing structures such as the old seawalls and old isolated piles no longer required // // page 12

17 The America s Cup Wynyard Hobson Groundwater Technical Report covers potential groundwater effects relevant to the stabilisation (ground improvements). Noise effects relating to the ground improvements and other geotechnical-related work such as piling, are covered in the Noise and vibration report (Marshall Day Acoustics). While some investigation has already been undertaken (to a sufficient level to support a grant of consent), further site specific investigations, analysis and assessment are also recommended as part of the design process in order to determine the most appropriate and cost-effective approach to mitigate the risk. The need for stabilisation of the Wynyard Quarter seawalls was already identified prior to the America s Cup development. The stability of these structures needs to be addressed before development of this northern part of Wynyard Quarter is significantly advanced. A legacy of the America s Cup project is to initiate this work, advancing stabilisation of some sections of the seawall. This may potentially facilitate future development, notably in the location of the temporary bases following removal Building Structure Foundations It is understood the development on the sites will vary, but in general will comprise 15m multi-storey syndicate base buildings for ancillary offices, amenities, larger open boatshed/workshop areas and outdoor open yards. The landside building sites will be prone to settlement due to the presence of the weak fill, Recent Marine Sediments and underlying Tauranga Group soils. These soils will consolidate beneath any new loads such as new fill or new buildings resulting in settlement of the ground surface, building and potentially services located near any structures. For example if the sites were raised by around 0.5 m with fill, settlements in the order of mm may occur. Additional settlement due to earthquake shaking may also occur, particularly if liquefiable ground is present. It is understood that the prior building foundations have been removed or will be removed. It is likely piles will be required to support the proposed buildings and that these could comprise driven pile, screw pile or bored reinforced concrete piles founded in the Waitemata Group rock, 20 to 23 m below CD. Where the structure is lightweight, flexible and tolerant of differential settlement then shallow foundations may be suitable. Site specific geotechnical investigations will be required to finalise foundation requirements for each of the structures // // page 13

18 7. Conclusions and Recommendations 7.1 Hobson and Wynyard Wharves and Breakwaters The proposed development in this area is to comprise extension of the existing piled wharf structure Hobson Wharf. At Wynyard Wharf South, infill sections of wharf will span between the existing Wynyard Wharf and the Brigham Street seawall. In addition breakwaters are to extend from Wynyard Wharf, Halsey Wharf Extension and two off Hobson Wharf. The piles for the wharf extensions and infill sections will be founded within the underlying Waitemata Group rock and generally embedded for a depth of 5-10 m. The key geotechnical issue for these structures are the potential variability in depth to Waitemata Group rock including the presence of localised valleys. Localised valleys up to 5 m depth have been encountered in the previous works at Viaduct Harbour. The wharf extensions are located towards the northern edge of a ridge therefore rock level is likely to be variable, becoming deeper towards the north. 7.2 Wynyard Point The geotechnical issues associated with development in and around the Wynyard Point reclamation, involving the construction of infrastructure, buildings and wharf structures, include susceptibility of soils to liquefaction, slope stability and settlement due to the presence of reclamation fill, marine sediments and the depth to rock. Under static (non-seismic) conditions previous studies indicate a relatively low level of stability of the reclamation, consistent with historical reclamation structures found elsewhere within the region. Typically the outer m of the reclamation have levels of static (non-seismic) stability less than that generally adopted for building platforms. The potential for significant areas of the reclamation to be impacted by instability under Ultimate Limit State (ULS) earthquake shaking indicates that some form of liquefaction mitigation and/or slope stabilisation will be necessary for the structures on or adjacent to the existing reclamation (i.e. Wynyard Wharf). Mitigation could comprise ground improvement such as piles, stone columns or cement-stabilised columns with a cement stabilised raft. Ground improvement may extend some 20 m landward of the existing seawall. Construction of ground improvements may necessitate the removal of existing structures such as old seawalls and isolated piles. Building structures should also be piled unless designed to tolerate settlement. 7.3 Further Geotechnical Investigations The body of existing geotechnical information available is adequate for the present concept design process, and to enable a full assessment of effects for the purpose of obtaining consent. Further geotechnical investigations are recommended at all proposed development sites before mid-2018 to confirm depth to rock and depth and strength of overlying soils for detailed design of the proposed structures. Geotechnical investigations are likely to comprise machine boreholes and cone penetrometer tests undertaken from existing reclamation and wharf structures. A review of the liquefaction potential of the reclamation and underlying soils around Wynyard Point and Wynyard Wharf was undertaken in early January That review confirmed that there is likely to be // // page 14

19 potential liquefaction. That review also recommended further specific investigations of the more liquefiable materials be undertaken to better assess the likely potential for liquefaction in the design earthquake. However regardless of these outcomes some form of ground improvement at the reclamation perimeter is likely to be required to improve static stability to levels generally adopted for building platforms. 8. Applicability Statement This report has been prepared by Beca on the specific instructions of our Client. It is solely for our Client s use for the purpose for which it is intended in accordance with the agreed scope of work. Any use or reliance by any person contrary to the above, to which Beca has not given its prior written consent, is at that person's own risk. Should you be in any doubt as to the applicability of this report and/or its recommendations for the proposed development as described herein, and/or encounter materials on site that differ from those described herein, it is essential that you discuss these issues with the authors before proceeding with any work based on this document // // page 15

20 Appendix A Previous Geotechnical Investigations // // page 16

21 North Wall Construction Records Wynyard Quarter Seawalls Investigation By Beca Ltd for Panuku Development Auckland, 2008 Standard Penetration Test results for 6 Piles. Sandstone reduced level for 8 Piles. North Wall Investigation By Beca Infrastructure Ltd for Ports of Auckland Ltd, machine-drilled boreholes and laboratory testing. Halsey Street Extension Wharf, Western Viaduct Wharf, New Western Viaduct and Harbour Entrance Protection Wharf Construction Records, Americas Cup 2000 Viaduct Basin Facilities By Beca Carter Hollings and Ferner Ltd for Fletcher Construction Ltd, rotary boreholes and 28 penetration tests. Lighter Basin (Americas Cup) By Woodward-Clyde for Auckland Regional Services Trust, June 1996 Eight boreholes for ground water monitoring (4) and soil sampling (4) for chemical analysis. Boreholes are descriptive with no in situ testing undertaken. Results from chemical analyses included. Americas Cup Investigation By Woodward-Clyde for Auckland Regional Services Trust, June 1996 Seven boreholes for soil sampling for chemical analysis. Boreholes descriptive with no in situ testing undertaken. Results from chemical analyses included. Proposed Viaduct Basin Development Whitbread Home Base By Beca Carter Hollings & Ferner Ltd, December 1992 Nine boreholes with SPT s at 1-2 m centres and shear vanes in cohesive soils (six of these bores were within the basin, three onshore), shear vane tests. Plans and cross sections. Laboratory testing (Atterberg, NWC, bulk dry and solid density, particle size, consolidation, permeability, triaxial). Ports of Auckland Ltd Viaduct Basin Development Site Investigation By Tonkin & Taylor Ltd, January // // page 17

22 Lighter Basin region. Three 600 mm diameter auger inspection boreholes (full logs of fill only) plus 2 x 50 mm diameter standpipe holes (drillers logs). Plans and cross sections. Summary of laboratory results (NWC, dry density and WC of compacted sample, scala in compacted sample, mass retained on 19 mm sieve, largest gravel dimension). Environmental testing undertaken by Bioresearches Ltd (separate report). Viaduct Basin Development Site Investigation By Tonkin & Taylor Ltd, 25 October 1991 Letter Report to Holmes Consulting Group. Three boreholes (BH 1, 2 & 2A) near to Custom Street West, shear vane data for cohesive soils at approximately 1 m intervals and SPT s in rock. Viaduct Basin Development By Tonkin & Taylor Ltd, 14 August 1991 Letter Report to Holmes Consulting Group. One borehole undertaken in 1986 for Simunovich Fisheries with SPT s at 0.5 m to 1 m centres. Viaduct Basin Development Engineering Report By Ports of Auckland Ltd, circa 1990 Borehole, auger, and sampling location plans. Freemans Bay Development Dredging and Foundations Investigation By Terra Aqua Consultants for Ports of Auckland Ltd, September 1989 Ten boreholes with SPT testing predominantly within the bedrock (ie. below the fill). Logs are descriptive based on NZGS. Includes cross sections and plans. Laboratory tests include: point load test indices; NWC; dry density; triaxial and uniaxial compression; saturation ratio; bulk density. Supplemented in 1990 with three additional boreholes north of the Western Viaduct by Harrison Grierson Consultants Ltd. Proposed Dry Dock G55 By Gilberd Hadfield for Booth, Sweetman & Wolfe, April 1968 Wash boring used to define interface between marine mud, soft and hard sandstone at 15 locations. Shear strength measured in the sandstone/mudstone at some of the locations. Interfaces and shear strength in bedrock is the only information provided. Proposed Dry Dock G46 By Auckland Harbour Board, March // // page 18

23 34 Prickings to define mud level and depth to hard. Blows/depth measured to define the strength of the strata. Viaduct Basin Development G6B By Auckland Harbour Board, August/September 1962 Prickings to locate Hard at 75 locations to the south of the Western Viaduct and West of Customs Street West. Cement Jetty Western Viaduct G19 By Auckland Harbour Board, March 1959 Shear strength tests at 12 locations parallel and west of Western Viaduct (beside Shed 118). Plan for prickings along proposed cement jetty and bulk cement area. Western Viaduct Construction Records S Cross sections through 52 rows of piles for the existing Western Viaduct (typically 6 piles per row, more for raker piles and western fillet). Sections show mud and rock elevations relative to driven pile depth // // page 19