Viaduct Harbour Bridge Coastal Effects Assessment

Prepared for Panuku Development Auckland Prepared by Beca Limited

12 June 2019

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Contents

Executive Summary ...... 1 1 Introduction ...... 1 2 Wynyard Crossing Bridges ...... 2 2.1 Existing Wynyard Crossing Bridge ...... 2 2.2 Proposed Wynyard Crossing Bridge ...... 3 2.3 Temporary Access ...... 3 2.4 Spatial Extent of Works ...... 3 3 Existing Environment ...... 4 3.1 Harbour Setting ...... 4 3.2 Tides, Currents and Flushing...... 4 3.3 Wind ...... 7 3.4 Waves and Wakes ...... 8 3.5 Sediment Processes and Sedimentation ...... 9 3.6 Coastal Hazards and Climate Change ...... 10 4 Effects of Construction ...... 12 4.1 Methodology for Marine Based Works ...... 12 4.2 Water and Sediment Quality ...... 12 5 Effects on Coastal Processes ...... 13 5.1 Approach for the Assessment of Coastal Processes ...... 13 5.2 Cumulative Effects ...... 13 5.3 Tidal Flows, Current and Flushing ...... 14 5.4 Waves and Wakes ...... 14 5.5 Sediment Processes, Sedimentation and Erosion ...... 14 5.6 Coastal Hazards and Climate Change Adaptation ...... 15 6 Mitigation and Monitoring ...... 16 7 Conclusions ...... 16 8 References ...... 17

Appendices

Appendix A – Tidal Modal Study

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| Viaduct Harbour Bridge Coastal Effects Assessment |

Revision History Revision Nº Prepared By Description Date A Stephen Priestley Draft report for client comment 14/05/19

B Stephen Priestley Final Draft 31/05/19

C Stephen Priestley Resource Consent Application 12/06/19

Document Acceptance Action Name Signed Date Prepared by Stephen Priestley 12/06/19

Reviewed by Niksa Sardelic 12/06/19

Approved by Stephen Priestley 12/06/19

on behalf of Beca Limited

© Beca 2019 (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.

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| Executive Summary |

Executive Summary

Overview 1. This resource consent application involves the removal of the existing Wynyard Crossing bridge which has reached the end of its design life. The existing bridge was designed and consented as a temporary bridge. The existing bridge will be replaced by the proposed Wynyard Crossing bridge, which is to be a double-leaf bascule bridge along the same alignment as the existing bridge.

2. Bridge approaches will connect the proposed bridge (the Proposal ) to land (Te Wero Island and Wynyard Precinct), either side of the double leaf bascule. It is expected that the construction will take approximately 9 months. During this period a temporary crossing will be established to the south of the existing bridge

3. Piles associated will the Proposal will occupy approximately 29m2 of seabed. The elevated footprint of the bridge is about 954 m 2. Piles will be bored and installed within steel casings.

4. Pontoons associated with the temporary crossing have a footprint of 480m2 and the associated temporary piles will occupy less than 5m2 of the seabed.

5. No reclamation or dredging of the Project Area is proposed .

Assessment Methodology 6. The proposal does not involve breakwaters (e.g. wave panels) or other structures which could have a large scale influence on the flow or velocity of water movement. Structures which are to be located below mean sea level are limited to piles and bulkhead structures which occupy a limited area of the Coastal Marine Area (CMA) within the Viaduct Harbour. As a result only numerical modelling of the tidal currents and basin flushing is considered appropriate to determine the actual and potential effects of the proposal on coastal processes. That modelling report is contained in Appendix A.

7. Unless otherwise stated, all other assessments in this report are based on the author’s experience with coastal structures in the Waitemata Harbour waterfront.

8. The existing environment is undergoing change. The infrastructure associated with Americas Cup 36 will alter the tidal and wave conditions within the Project Area. Relative effects on the environment are therefore described in this context, with references to Pre-Americas Cup and to Post-Americas Cup.

Existing Environment 9. Referred to as the Project Area, the affected CMA is in the lower Waitematā Harbour and within a narrow corridor (about a 10m width) between Karanga Plaza and Te Wero Island.

10. Tidal velocities within the Project Area are low and less than 0.1 m/s.

11. The natural, relatively high tidal range of 2.5m (median) results in good to fair flushing of Viaduct Harbour, including the post Americas Cup project.

12. The Project Area is sheltered from wind waves and external wakes, with the annual significant wave height less than 100mm.

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| Executive Summary |

13. Relevant coastal hazards include storm surge (extreme storm tides) and tsunami. The effects of sea level rise are a relevant component to these coastal hazards.

14. The coastal edge of the Viaduct Harbour contains hard engineering structures which are resistance to erosion and scour.

Potential Environmental Effects 15. From the author’s experience with waterfront projects, the effects during construction are expected to be less than minor. Some resuspension of sediment could be expected but will be localised and temporary. Any disturbed material will be deposited in the vicinity of the Project Area.

16. The Proposal will not change tidal currents within the harbour wide context and any changes will be local and of a low magnitude. Flushing of the Viaduct Basin will remain unchanged.

17. Any potential adverse effects related to wave/wake changes, sedimentation and scour will be negligible.

18. Coastal hazards (including the projected effects of climate change) have been considered for the Proposal as a whole. The lifting section of the proposed Wynyard Crossing bridge can be functional over a 100 year period, and the fixed sections of the bridge can be regraded to accommodate sea level rise.

19. As the overall adverse effects associated with this project are less than minor and probably negligible, no physical monitoring of water or sediment quality is proposed.

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| Introduction |

1 Introduction

Beca has been engaged by Panuku Development Auckland (Panuku) to carry out the coastal processes assessment for the proposed Wynyard Crossing bridge (the Proposal ) within the Viaduct Harbour. This report has been prepared to accompany a resource consent application for the Proposal. This bridge will link Te Wero Island and Wynyard Precinct (Karanga Plaza) and is located between the outer and inner Viaduct Harbour as shown in Figure 1.

The purpose of this document is to describe:

● The existing harbour sedimentation and coastal processes; ● Effects of the Proposal and its maritime related construction on coastal processes; and ● Mitigation measures where required to address these effects.

Other documents address engineering, services, traffic, noise (including underwater noise), ecology, urban design and landscape, navigational safety, and constructability associated with the proposed replacement bridge. It is noted that the existing environment is undergoing change. The infrastructure associated with the 36 th Americas Cup (AC36) has been consented and is being construction. That project will alter the tidal and wave conditions within the Project Area as generally shown in Figure 2.

Figure 1: Aerial photo showing the Wynyard Precinct and Viaduct Harbour

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| Wynyard Crossing Bridges |

Figure 2: Aerial photo showing the Wynyard Precinct and Viaduct Harbour. Existing wave panels are shown in Cyan. New breakwaters are shown in yellow. Black illustrates new structures. Point V9 is in the channel at the location of the Project.

2 Wynyard Crossing Bridges

Layouts of the existing Wynyard Crossing bridge and the Proposal are set out in the Drawing Set.

Both bridges comprise a central single opening, flanked by a fixed bridge-like section each side which are connected to land. The level of the land on the Karanga Plaza side is 5.0m CD and the level on the Te Wero Island side is 4.4m CD. The existing waterway opening will remain unchanged with an overall width of 105m and cross-sectional (facing the tide) area of 683 m2. The relevant approximate metrics for each bridge is given below (Note all levels are in terms of Chart Datum (CD)):

2.1 Existing Wynyard Crossing Bridge

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| Wynyard Crossing Bridges |

● No. of piles and cross-sectional area (to mean sea level -MSL) and volume on RHS: 14 no. piles, diameter of 356mm, frontal area of 32.2m 2, plan area of 1.4m 2, and occupying a space of 9.1m 3. ● Cross-section (to MSL) of bulkhead (for mechanical equipment) or other structural components on RHS: Nil as bulkhead is above 1.92m CD.

2.2 Proposed Wynyard Crossing Bridge

● Approximate width of bridge: 8.8m ● Fixed section span length (LHS- Karanga Plaza end): 28.4m ● Opening span: 43.4m ● Fixed section span length (RHS-Te Wero Island end): 33.1m ● No. of piles and cross-sectional area (to mean sea level (MSL)) and volume on LHS: 18 no. piles of varying length, 1020mm diameter, frontal area of 99.6m 2, plan area of 14.7m 2, and occupying a space 79.8m3. ● Cross-section (to MSL) and volume of bulkhead (for mechanical equipment) or other structural components on LHS: underside of bulkhead is -0.25 CD, area is 26.7m 2 occupying a space of 373.2m3. ● No. of piles and cross-sectional area (to mean sea level -MSL) and volume on RHS: 18 no. piles of varying length, 1020mm diameter, frontal area of 99.6m 2, plan area of 14.7m 2, and occupying a space 79.8m3. ● Cross-section (to MSL) and volume of bulkhead (for mechanical equipment) or other structural components on RHS: underside of bulkhead is -0.25 CD, area is 26.7m 2 occupying a space of 373.2m3.

2.3 Temporary Access The programme of works is to decommission the existing Wynyard Crossing bridge and construct the Proposal on the same alignment of the existing bridge. Temporary access will be provided by way of pontoon access from Karanga Plaza to Te Wero Island. Access from the land to the pontoons will be via gangways. The central section of the pontoons will be able to slide apart to facilitate safe vessel navigation. A general arrangement of these temporary works is included in the Drawing Set.

The pontoons have a width of 4m, a draft of 0.6m and a freeboard of 0.6m. The overall length of the pontoon is 120m with a plan area of about 480m 2. Its support piles occupy an area of less than 5m2.

2.4 Spatial Extent of Works

Based on the above metrics, the existing Wynyard Crossing bridge has a frontal blockage of (23+32)/683=8%, a plan area of the piles of (1+1.4)=2.4m 2, and a spatial extent of (6.5+9.1)/(683x5.4)=0.4%. The Proposal will have a frontal blockage of 2(99.6+26.7)/683=37%, a plan area of the piles of (14.7+14.7)=29.4m 2, and a spatial extent of 2(79.8+373.2)/(683x8.8)=15.1%. The frontal blockage factor is conservative as it does not take into account locations where the piles line up with the tidal flow. Temporary access will have a frontal blockage of about 120(0.6)/683=10%, and a plan area of the pontoons and piles of about 480m 2. To give the above metrics some context, comparison should be made with the inner Viaduct Harbour which has an area of about 77,000m 2 and a seawater volume of about 500,000m3 at mean sea level.

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| Existing Environment |

3 Existing Environment

3.1 Harbour Setting

Waitemata Harbour is a large drowned valley with numerous arms and extends some 25 kilometres inland from the harbour entrance at North Head. The high tide area of the harbour is some 180km 2 and the volume is approximately 460 million m 3. Hydraulic conditions are governed by the well-defined tidal channel, from north of Rangitoto Island through to Herald Island in the Upper Harbour. The channel is fixed by firm features like Takapuna Head and Stanley Point to the north, Rangitoto to the east and Takaparawha Point and the Port of Auckland to the south. The harbour catchment, or area of land draining into the harbour, is approximately 440km 2.

The present-day downtown Auckland waterfront has been formed by shoreline reclamation and development of roading and marine infrastructure over the past 150 years. This includes the Auckland Harbour Bridge reclamation, Westhaven Marina, Wynyard Precinct reclamation and wharves, Viaduct Harbour reclamation and wharves, Outer Viaduct Harbour, the Council-owned finger wharves and the Ports of Auckland wharves and terminals. The site is located in the lower Waitemata Harbour, within Freemans Bay where the Viaduct Harbour is located at the southern end of the Bay. The main harbour channel lies approximately 0.5 km from the site. Tidal flows generate currents in the lower Waitemata Harbour. It is estimated that the average tidal flow in the main harbour channel is 7,200m3/s.

The Project Area is within the Viaduct Harbour between Te Wero Island and Wynyard Precinct (Karanga Plaza). Seabed levels at the site are around -4.6m CD.

3.2 Tides, Currents and Flushing

The Waitemata Harbour experiences semi-diurnal tides (high tides every 12.4 hours). The tidal prism, or volume of seawater exchanged in every tide, is about 160 million m3 (Beca, 1996). This is about 35% of the harbour volume. Table 1 gives the astronomical tide levels for the lower Waitemata Harbour (Port of Auckland) due to the gravitational effects, most notably of the moon and sun.

Table 1: Tide levels for the lower Waitemata Harbour (LINZ, 2017)

Tide Condition Level

Highest Astronomical Tide (HAT) 3.70m CD

Mean High Water Springs (MHWS) 3.39m CD

Mean High Water Neaps (MHWN) 2.86m CD

Mean Sea Level (MSL) 1.90m CD

Mean Low Water Neaps (MLWN) 0.95m CD

Mean Low Water Springs (MLWS) 0.41m CD

Lowest Astronomical Tide (LAT) 0.05m CD

Spring tide range 2.98m

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Tide Condition Level

Neap tide range 1.91m

Tide levels are measured in relation to Chart Datum (CD), which is 1.743m below Auckland Vertical Datum 1946 (AVD-1946), and standard barometric pressure of 1013 hectopascals. Chart Datum is the datum adopted for marine-based projects and is at or close to the lowest astronomical tide. Extreme storm tides (storm surge) are covered in Section 3.6.2.

Recorded current data for the Waitemata Harbour has been predominantly collected by the Ports of Auckland Limited (POAL) but there is limited data within the Viaduct Harbour. The following datasets have been utilised for this study (refer to Appendix A):

● Boat mounted Acoustic Doppler Current Profiler (ADCP) measurements at hourly intervals over mean spring (3.0 m range) and neap (1.5 m range) tides. The survey tracks covered the harbour from Westhaven Marina to North Head at the harbour entrance (Vennell 2015-2017). ● ADCP measurements covering a 1-week duration from 23/11/2017 to 01/12/2017 at the Viaduct Harbour Bridge and the Inner Harbour.

A hydrodynamic tidal model has been set up for this study and results are reported in Appendix A and summarised in this report.

3.2.1 Pre-America’s Cup The current measurements show that within the main harbour currents are semi diurnal with higher ebb currents (up to 0.95m/s) compared to flood (up to 0.9m/s). Within the water spaces bounded by the wharves, reclamations and breakwaters, currents patterns are more confused due to the generation of eddies in the lee of the structures which tend to move as the current varies in the main channel. Generally, within these protected areas currents tend to have a single peak velocity and the semi diurnal pattern is less pronounced compared to the main channel velocities. Wind generated currents are also a frequent feature within the Harbour, with currents reaching about 2% of the wind speed. In general, for wind speeds less than 7 m/s, wind generated currents (typically up to 0.14 m/s) predominate whereas for wind speeds greater than 7 m/s, wave conditions predominate. A characteristic of Freemans Bay is an eddy driven by the tidal flow in the main harbour channel. The eddy develops over the last 2 hours of the flood flows and first 3 hours of the ebb flow and generally extends over the basin. The circulation is clockwise during ebb and anti-clockwise during flood tides. The ebb eddy is stronger, with peak velocities of approximately 0.1 m/s compared to lesser values during the flood eddy. A plot of current velocities in Freemans Bay, illustrating this eddy feature, is shown in Figure 3. These eddies provide a tidal flushing volume into and out of the water body that is greater than that associated with the filling and emptying of the tidal prism.

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| Existing Environment |

(m/s)

Figure 3: Plot of typical ebb tide vectors in Freemans Bay for Pre-Americas Cup

Eddies from Freemans Bay penetrate only slightly into Viaduct Harbour. For the Outer Viaduct Harbour the current pattern can be variable due to flows under Hobson Wharf, via the main entrance and leaving under Halsey Wharf. On average current velocities were measured to be less than 0.1 m/s. Within the Inner Viaduct Harbour the measurements suggested minor to no tidal response. Peak spring currents of approximately 0.05 m/s were modelled in the Project Area. Flushing can be assessed using the e-folding method. e is the Eulerian number, approximated by 2.71828. The flushing time calculated using this approach is the time required for an e-fold renewal of water, which is the time taken for a body of water to reach a dilution level of 1/e or 37%. For a point in the centre of the Inner Viaduct Harbour, the e-fold flushing time is about 45 hours (spring tide conditions) to about 70 hours (neap tide conditions) (see Appendices A). The neap tide flushing time within the Project Area was modelled at 43 hrs. E- folding times less than 96 hours are considered “good” flushing, between 96 – 240 hours indicates “fair” flushing and greater than 240 hours indicates “poor” flushing (EPA, 1985; PIANC 2008).

3.2.2 Post America’s Cup

Installation of wave-screens along Hobson Wharf and breakwaters within the Wynyard Basin were required to achieve the tranquillity requirements for the America’s Cup. These wave-screens will result in longer flushing times within the Viaduct Harbour. For example, the maximum spring tidal current within the Project Area will be 0.04 m/s and the neap tide flushing time 55 hrs . For a point in the centre of the Inner Viaduct Harbour, the e-fold flushing time is about 57 hours (spring tide conditions) to about 81 hours (neap tide conditions) (see Appendix A). These generally reflect good flushing within the inner Viaduct harbour.

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3.3 Wind Wind generates local currents and waves. The prevailing surface wind direction is predominantly from the south-west (25%), west (15%) and from the north to north-east (15%). Auckland wind roses for Whenuapai (long term record, 14km from site) and Mechanics Bay (historic shorter-term wind record, 2km from the site), are illustrated in Figures 4 and 5. The Whenuapai rose shows 10-minute mean wind speeds, measured hourly. The Mechanics Bay rose is based on daily observations. Wind speeds are typically less than 8 m/s (approximately 30 km/hr).

Figure 4: Wind rose for data recorded at Whenuapai (1960-2008) (Source; NIWA, 2012)

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| Existing Environment |

Figure 5: Wind rose for data recorded at Mechanics Bay (1955 to 1962) (Source: NIWA CliFlo)

Sustained extreme wind speeds for the predominant directions are given in Table 2, based on a review of wind data from the Whenuapai gauge (1960-2008) and the Weather Research and Forecasting (WRF) model data. These wind speeds include an allowance of 10% (compared to the existing environment) for climate change.

Table 2: Predicted extreme wind speeds

Average Recurrence Wind speed by direction (m/s) Interval (years) West North East

1 18 16 16

10 23 20 22

50 25 23 23

100 27 24 25

3.4 Waves and Wakes

The lower Waitemata Harbour is sheltered from ocean swell waves but will experience wind waves generated by westerly / northerly / easterly winds across the Waitemata Harbour. The fetches measured in the main channel north of the Project Area are approximately 8km (west), 4.5km (north, though much of this is over relatively shallow water) and 12km (east). Table 3 summarises extreme wave conditions within the lower Waitemata Harbour. Wave conditions have been determined from hindcasting using the local wind data in Table 3, the above fetches, and sea level at MHWS. It is based on Young (1997) for the shallow northerly fetch and the Coastal Engineering Manual (USACE, 2008) for the deeper water fetches to the west and east.

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Table 3: Hindcast extreme wave conditions, Lower Waitemata Harbour

Average Wave Parameter by direction Recurrence Interval Hs (m) West Tp (s) Hs (m) North Tp (s) Hs (m) East Tp (s) (years) Hmax Hmax Hmax (m) (m) (m)

1 0.9m 1.5m 2.8s 0.6m 0.9m 2.8s 0.9m 1.6m 3.1s

10 1.2m 2.0m 3.1s 0.7m 1.1m 3.0s 1.4m 2.3m 3.5s

50 1.3m 2.2m 3.2s 0.8m 1.2m 3.2s 1.5m 2.5m 3.6s

100 1.4m 2.4m 3.3s 0.9m 1.3m 3.3s 1.6m 2.6m 3.7s

The Project Area is sheltered from the lower harbour wave climate. Wave modelling (Beca and Tonkin & Taylor, 2018) was undertaken to assess the wave climate within the Viaduct Harbour for Americas Cup 36. The Project Area is also affected by vessel wakes. External ferry wakes are attenuated to a significant degree but there will be internally generated vessel wakes.

3.4.1 Pre-Americas Cup

The annual significant wave height at the Project Area was assessed at 0.09 m. The external (weekly) vessel wake was assessed at 0.14 m. The internal vessel wake will be in be order of 0.2 m.

3.4.2 Post Americas Cup

The annual significant wave height at the Project Area was assessed at 0.07 m. The external (weekly) vessel wake was assessed at 0.06 m. The internal vessel wave will be in be order of 0.2m.

3.5 Sediment Processes and Sedimentation

3.5.1 Sediment and Water Quality

The downtown Auckland waterfront has been created over the past 150 years by reclamation, dredging and construction, which have highly modified the environment. In general, the surface of the seabed is muddy shelly sand, regularly mobilised by vessels using the berths. Water quality along the city waterfront reflects the overall nature of the Waitemata Harbour catchment and the physical location of the site. Historical data indicates that water quality is generally good with mean total suspended sediment levels less than 10g/m 3. During storm conditions, increases in the sediment concentration on the ebb tide can be expected. Water clarity in the downtown area improves with distance from the shore and with depth, particularly away from the larger Auckland Council stormwater discharges. The waterfront receives all stormwater flows from Auckland’s CBD. Sediment quality reflects the historical uses of the downtown waterfront area and the material carried in stormwater from the CBD. Most of the sediment carried by stormwater flows settles out of suspension in the waterfront basins. Details of sediment quality in these basins are covered in the 2011 Port of Auckland Sediment Quality Survey by Golder Associates, which is already held by Auckland Council. Indications from waterfront sediment monitoring are that sediment quality has remained relatively consistent over time and the sediment typically contains elevated trace elements, such as mercury, copper and zinc, and organic compounds.

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| Existing Environment |

3.5.2 Sedimentation Since being dredged in 1998 and with infrequent maintenance dredging, some unconsolidated marine sediments have accumulated on the seabed surface of the Project Area. These generally comprise around 60% to 85% silt and clay size particles and are commonly referred to as marine mud. Based on recent bathymetric surveys annual deposition is about 40mm (Beca and Tonkin & Taylor, 2018). It is expected that any accumulated marine mud will have an average depth of about 300mm across the Project Area.

Underlying the marine mud, is Waitemata Series Sandstone (rock) which is not prone to scour or erosion.

3.6 Coastal Hazards and Climate Change

3.6.1 Sea Level Rise

In accordance with the New Zealand Coastal Policy Statement (NZCPS) (Policy 24 and 25), sea level rise (SLR) should be considered over at least a 100-year planning period. The Ministry for Environment’s (MfE) national guidance on Coastal Hazards and Climate Change (MfE, 2017) recommends use of four SLR scenarios corresponding to different Representative Concentration Pathways (RCPs, essentially these are emissions scenarios). Table 4 lists the SLR allowances for the recommended scenario (RCP 8.5) for medium to long term periods.

Table 4: Guidance for sea level rise allowances (MfE, 2017)

Period NZ RCP2.6 M SLR NZ RCP4.5 M SLR NZ RCP8.5 M SLR NZ RCP8.5 H* SLR

Medium term to 0.25m 0.26m 0.30m 0.39m 2055 (consistent with 35-year consent duration)

Long term to 0.55m 0.67m 1.06m 1.36m 2120s

The guidance for NZ RCP8.5 M SLR compares well with the Auckland Unitary Plan: Operative in Part (AUP: OP) policy, which requires consideration of a SLR allowance of 1.0m over 100 years as the base case. RCP8.5 M SLR envisages no climate change mitigation.

3.6.2 Storm Surge

Meteorological conditions such as low barometric pressure and on-shore winds combine with astronomical tides to produce short term increases in sea level known as storm tides. Table 5 lists storm tide levels for a range of annual exceedance probabilities (AEP) and ARI and storm tide levels with the 2120 sea level rise allowances added for the RCP 8.5 scenario.

Table 5: Storm tide levels for the lower Waitemata Harbour

Average Annual Present Day 2055 Level with 2120 Level with Recurrence Exceedance Level (m CD) NZ RCP8.5M SLR NZ RCP8.5M SLR Interval (years) Probability (m CD) (m CD)

2 39% 3.78 4.08 4.84

5 18% 3.86 4.16 4.92

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Average Annual Present Day 2055 Level with 2120 Level with Recurrence Exceedance Level (m CD) NZ RCP8.5M SLR NZ RCP8.5M SLR Interval (years) Probability (m CD) (m CD)

10 10% 3.92 4.22 4.98

20 5% 3.97 4.27 5.03

50 2% 4.05 4.35 5.11

100 1% 4.1 4.40 5.16

200 0.5% 4.15 4.35 5.21

For comparison with the above, the existing land at the Project Area is 5.0m CD at Karanga Plaza and 4.4m CD at Te Wero Island.

3.6.3 Tsunami

The present tsunami hazard response at the site is emergency evacuation. The Civil Defence maps identify approximately the seaward 10-20m of the city waterfront as Red Zone (shore exclusion zone, designated off limits in the event of any expected tsunami), and the remainder as Orange Zone (evacuation zone orange, evacuated if there is a medium to large tsunami threat) (Auckland Council website; Civil Defence, 2008).

The most current tsunami information is the probabilistic tsunami modelling undertaken by GNS in 2013. It considers tsunami generated by distant, regional (South Pacific), and local sources for Average Recurrence Intervals (ARIs) of 100 to 2500 years. For Auckland, the higher ARI events (e.g. 2500-year ARI) are generated by large earthquakes in the Kermadec Trench, Chile, Peru, Alaska, Japan and the Tonga Trench (GNS, 2013). Specific levels for the Auckland city waterfront are not modelled; rather the maximum probabilistic tsunami height (against an imaginary vertical wall at the coast) is given for a 20km section of Auckland coastline that includes the more exposed east coast beaches. This gives a reasonable approximation to the expected run- up height where the tsunami does not penetrate far inland i.e. the height at the coast for locations such as the city waterfront. The probabilistic tsunami heights do not include for tides and are determined relative to a background sea level i.e. sea level at the time of tsunami arrival is not included in the tsunami heights. Table 6 gives probabilistic maximum tsunami heights for the 20km Auckland East and Takapuna section of coastline.

Table 6: Maximum tsunami height for Auckland East and Takapuna coastline (50th percentile epistemic uncertainty) (GNS, 2013)

Annual Recurrence Interval (years) Maximum tsunami height relative to background

sea level (m)

100 2.1 500 3.6 2500 5.2

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Modelling of tsunami with future sea level rise is yet to be undertaken for New Zealand. With projected future sea level rise, higher tsunami would be generated compared with the same size source event today, due to the increased water depths from sea level rise.

Tsunami inundation modelling has been undertaken for the Auckland region using selected tsunami sources (NIWA & GNS, 2010; NIWA, 2009). The Auckland tsunami evacuation zone maps referenced above are partly based on those studies. The GNS (2010) report gives a tsunami height of 1.5m in the CBD for the 2500 ARI event.

4 Effects of Construction

4.1 Methodology for Marine Based Works

This section discusses the effects of the construction activities of the marine based works. These works include the removal of existing piles and the installation of new piles. The construction methodology and programme for all other works is discussed in another report by others.

Based on the information in Section 2, removal of the existing piles will entail cutting of the piles which currently occupy an area of 2.4 m 2. The elevated footprint of the existing Wynyard Crossing bridge is (105x5.4)=567 m 2. The existing piles will be cut off below seabed level with a proprietary cutting tool. All reinforcing will be removed, and the remnant piles taken off site. Piles associated will the Proposal will occupy approximately 29 m 2 of seabed. The elevated footprint of the bridge is about (105x8.8)+30 (for bulkheads)=954 m 2. Piles will be bored and installed within steel casings. The drilling rig will be based on a fixed platform. The casings will be installed 1-2m into the rock and thereafter will be drilled out to form a rough surface. The depth of the bored pile will be up to 10m into the underlying rock. The bored material from within the casing will be extracted and removed from site.

No reclamation or dredging of the Project Area is proposed.

4.2 Water and Sediment Quality Existing pile removal is likely to result in some resuspension of bottom sediment, causing a temporary increase in total suspended solids levels at the site but will be limited due to the small amount of sediment present. It will be localised and temporary. Given the depth of sediment is limited to about 300mm and the area affect per pile of about 2m diameter, the total volume affected will be about 40m 3 which is relatively low. Resuspended material will be deposited in the Project Area and adjoining areas.

Pile installation will result in some resuspension of bottom sediment, causing a local and temporary increase in total suspended solids levels at the site but will be limited due to the small amount of sediment present. In order to reduce this resuspension of sediment, Panuku has opted for bored piles installed within steel casings. Boring the piles also allows all the spoil to be contained within the steel casings, thereby reducing the impact on the surrounding environment. Spoil resulting from the installation of the piles will be collected via barge and/or truck. Based on the top 500mm being contaminated to some degree, the amount of this material will be about 15m 3 which is a relatively low volume and will need to be disposed of to landfill. Based on the rock being drilled to a 10m depth, the amount of rock spoil material will be limited to about 300m 3. This rock material could be removed from site as clean fill.

Due to the historical levels of suspended solids in the area and the low tidal flow, the impacts of resuspension in the relatively limited time frame that piling will be carried out are likely to be minimal. Resuspended material will be deposited in the Project Area and adjoining areas.

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It is noted that temporary access platforms and associated support piles will be installed. These temporary piles will probably be vibrated in and finished by driving to a set. This enables the piles to be removed from the site on completion of the works. This vibrating of piles into the seabed will cause some resuspension of sediment but disturbed sediment will be close to the seabed and localised. Overflow of harbour water from the pile casings during construction of the concrete piles will be managed on site to reduce impacts on water quality. Prior to the pile concrete being placed inside the casing, seawater inside the casing is pumped out. Much of this flow is clean water, but there will be some suspended solids and potentially small amounts of a concrete plume. On recent waterfront construction sites, the flow has been successfully managed using site procedures, such as pumping to an adjacent empty pile or removal and disposal via sucker truck. A similar managed approach is proposed for the new piles this project. Oil spillages during construction are a potential risk, which may affect the quality of water in the surrounding environment. To mitigate this risk, the contractor will be required to prepare and implement safe refuelling procedures and emergency spill response procedures at the construction site as part of the Construction Management Plan.

Effects on sediment quality will be less than minor as the amount of sediment affected will be small. The harbour sediment that is disturbed by construction will redeposit in nearby depositional areas (such as the Project Area and the adjacent inner and outer Viaduct Harbour), all of which have similar sediment quality.

5 Effects on Coastal Processes

The decommissioning of the existing Wynyard Crossing bridge, the installation of temporary access, and construction of the Proposal will not impact on large scale coastal processes such as tides, currents, waves and sediment transport. Any adverse effects will be localised and small scale.

5.1 Approach for the Assessment of Coastal Processes

The proposal does not involve breakwaters (e.g. wave panels) or other structures which could have a large- scale influence on the flow or velocity of water movement. Structures which are to be located below MSL are limited to piles and bulkhead structures which occupy a limited area of the CMA within the Viaduct Harbour. As a result only numerical modelling of the tidal currents and basin flushing is considered appropriate to determine the actual and potential effects of the proposal on coastal processes. That modelling report is contained in Appendix A. All other assessments in this report are based on the author’s experience with coastal structures in the Waitemata Harbour waterfront.

5.2 Cumulative Effects

This assessment of the coastal processes assumes that this Project along with other probable activities should be assessed on the environment as it exists. Other probable activities include other coastal works which have resource consents and natural processes such as climate change and tsunami.

It is understood there are a range of coastal projects being undertaken within the Ferry basin, Freeman’s Bay and Westhaven Marina. The coastal processes effects addressed below will not have any large-scale influence on other projects such as Americas Cup 36.

Cumulative historical developments within downtown Auckland have involved significant reclamation and extension into the harbour. It is acknowledged that many of the natural coastal features from pre-European times have been lost through that reclamation. Such features would have included small beaches, headlands, reefs, and cliff-lined embayments. However, for a long time, the downtown waterfront has been a

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highly-modified environment and the effects of the project on coastal processes must be considered in that context.

5.3 Tidal Flows, Current and Flushing

5.3.1 Pre-America’s Cup

Peak spring currents of approximately 0.05 m/s were modelled in the Project Area. The neap tide flushing time within the Project Area was modelled at 43 hrs. Within the inner section of the Lighter Basin the neap tide flushing time was 146 hrs which is the longest within Viaduct Harbour.

Modelling of the structures associated with the Proposal (see Appendix A) resulted in the following results and likely effects:

● Peak spring current of 0.05 m/s. This represent slight increase of 20% but it is very localised and does not change the currents within the inner or outer Viaduct Harbour. This current velocity is less than currents within the Viaduct Harbour entrance and within the outer Viaduct Harbour. Likely adverse effects are less than minor. ● Neap tide flushing times of 43 hrs within the Project Area and 152 hrs within the inner section of the Lighter Basin. As no changes in flushing times are apparent, likely adverse effects are negligible.

5.3.2 Post America’s Cup

Peak spring currents of approximately 0.04 m/s were modelled in the Project Area. The neap tide flushing time within the Project Area was modelled at 55 hrs. Within the inner section of the Lighter Basin the neap tide flushing time was 157 hrs.

Modelling of the structures associated with the Proposal (see Appendix A) resulted in the following results and likely effects :

● Peak spring current of 0.04 m/s. This represents no increase in tidal currents and does not change the currents within the inner or outer Viaduct Harbour. This current velocity is less than currents within the Viaduct Harbour entrance and within the outer Viaduct Harbour for which vessels are likely to frequently experience. Likely adverse effects are therefore less than minor. ● Neap tide flushing times of 55 hrs within the Project Area and 160 hrs within the inner section of the Lighter Basin. As no changes in flushing times are apparent, likely adverse effects are negligible.

As the spatial extent of the temporary access works is less than for the Proposal, the adverse effects on tidal currents and flushing times of the temporary works will also be negligible.

5.4 Waves and Wakes

The wave and wake climate within the Project Area will remain unchanged with the Proposal for both the pre- Americas Cup and post-Americas Cup scenario. Likely adverse effects are therefore negligible.

5.5 Sediment Processes, Sedimentation and Erosion

The Project Area is subject to regular sedimentation of about 40 mm/year and is in a depositional zone. Local current velocities and wave/wake orbital velocities are insufficient to mobilise the marine mud. Erosion of the bridge structure and the adjoining existing perimeter structures will not occur. Likely adverse effects are therefore negligible.

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5.6 Coastal Hazards and Climate Change Adaptation

5.6.1 Sea Level Rise (SLR) It is noted that the Auckland Unitary Plan includes a requirement to consider at least 1m sea level rise over the next 100 years. MHWS will then be 4.4m CD and the 100-year ARI storm surge level will be 5.20m CD.

While the bridge proposed has a design life of 100 years the resource consent for the bridge structure, will be for a 35-year period, following which a new consent would be required to be sought. During that time SLR is expected to be about 0.3m. MHWS will then be 3.7m CD and the 100-year ARI storm surge level will be 4.40m CD.

The land approaches at Karanga Plaza are at 5.0m CD, and at Te Wero Island are at 4.4m CD. These levels are above MHWS (in 35 years times) but in the 100-year ARI storm surge, wave/wake overtopping of the Te Wero approach will occur in severe sea storms. The proposed Wynyard Crossing bridge will be fully functional although the underbridge clearance (or air draft) will reduce from 3.0m to 2.7m. In terms of a longer-term strategy to manage the effects of SLR for this Project, the following approach is identified:

● A more definitive strategy will be required at the time of resource consent renewal. At that time more will be known about the actual degree of SLR over the prior 35-year period. ● As the replacement bridge is a complex mechanical structure, it is not practical to incorporate features within the design to raise the lifting section of the structure in the future. It is noted, however, that the fixed sections, which are proposed to be ramped down from the bridge deck level of 6.8m CD down to the land approach levels, could be regraded (i.e. lifted in part) in the future to accommodate higher land approach levels, elevating these areas above the 100-year ARI event including projected SLR. Other than routine structural inspection and re-evaluation of the structural integrity at the time of these works, no additional structural features need to be incorporated into the Proposal at this time. ● The central moving bridge structure itself will be fully functional for a 100-year period. ● Depending on the rate of SLR the underbridge clearance will reduce, from 3.0m (current design clearance) to 2.0m over 100 years (assuming a 1.0m SLR). This may necessitate more frequent openings of the bridge to enable vessels to pass which are no longer able to manoeuvre through the reduced air draft . ● The level of the land approach on the Karanga Plaza side is 5.0m CD and the level on the Te Wero Island side is 4.4m CD. These land levels could be raised to respond to SLR and the effects of storm surge in future. It is noted that adjoining land within the Wynyard Precinct and Eastern Viaduct is also low lying and a strategy for responding to the effects of future SLR and coastal hazards will be required for these wider areas of the waterfront. Future modifications for the bridge approaches or an alternative strategy will be a separate project and one that will be common to other areas within the waterfront area.

5.6.2 Tsunami As with other locations potentially exposed to tsunami, evacuation plans, and public information signs will be required for the wharves and landside area. From studies to date it appears that the tsunami hazard relates to regional and distant sources, which provides a window of between approximately 1 hr (regional source) and 12 hours (distant source) to evacuate the structures (NIWA, 2009; NIWA, 2010; GNS, 2013). The emergency evacuation plans for the Site will be subject to the CBD emergency management plan. The situation will be similar to other public areas the Auckland waterfront (e.g. Princes Wharf, Queens Wharf, Westhaven Marina breakwater).

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6 Mitigation and Monitoring

Mitigation measures during construction, which are consistent with those used on other recent waterfront projects, will include:

● Notification of the Harbourmaster and POAL’s Harbour Control and pilots before work starts. ● The work site will be advised to marine traffic via Harbourmaster broadcasting/Notice to Mariners at least 14 days prior to commencement of works. ● Specific notice of the work will be issued to yacht and boat clubs in the Waitemata Harbour, ferry operators, the Coastguard and the Police Maritime Unit. ● The Contractor will be required to maintain regular contact with the Harbourmaster and Harbour Control during the construction period. ● The work site will be marked with buoys. ● All barges, watercraft, work site marker buoys, temporary staging and the dolphins will be lit at night so that they are visible to passing watercraft. ● Closure of parts of Wynyard Precinct/Karanga Plaza and Te Wero Island required for construction purposes, particularly for health and safety reasons. With these proposed measures in place, and drawing on recent experience on other waterfront projects, the effects during construction are expected to be less than minor.

It is not intended to conduct any physical monitoring of water or sediment quality during construction as the effects on the surrounding environment are considered to be less than minor. Potential effects have been mitigated by the use of bored piles within casings.

The Construction Management Plan includes requirements for the construction mitigation measures set out above.

7 Conclusions

● From the author’s experience with waterfront projects, the effects during construction are expected to be less than minor. Some resuspension of sediment could be expected but will be localised and temporary. Any disturbed material will be deposited in the vicinity of the Project Area.

● The Proposal will not change tidal currents within the harbour wide context and any changes will be local and of a low magnitude. Flushing of the Viaduct Basin will remain unchanged.

● Any potential adverse effects related to wave/wake changes, sedimentation and scour will be negligible.

● Coastal hazards (including the projected effects of climate change) have been considered for the Proposal as a whole. The lifting section of the proposed Wynyard Crossing bridge can be functional over a 100-year period, and the fixed sections of the bridge can be regraded to accommodate sea level rise.

● As the overall adverse effects associated with this project are less than minor and probably negligible, no physical monitoring of water or sediment quality is proposed.

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| References |

8 References

Auckland Council website http://www.aucklandcivildefence.org.nz/hazards/natural-hazards/ Beca, 2018. Westhaven: Pile Berth Redevelopment – Civil Engineering & Infrastructure Report. Beca, 2018. America’s Cup 36: Base Infrastructure Technical Report. Beca and Tonkin and Taylor, 2018. America’s Cup 36: Coastal Processes and Dredging Technical Report. Beca, 2016. Waitemata Navigation Channel Maintenance dredging. Beca, 2015. Westhaven Northern Breakwater – Preliminary Engineering Design Report. Beca, 2007. Consent Permit Application – Dredging at the Port of Auckland.

Beca, 2006. Rangitoto Channel Dredging – Seawater Quality monitoring Beca, 2003. Americas Cup Extra Bases Hydraulics Report Beca, 2001a. Rangitoto Channel Proposed Deepening of Commercial Shipping Lane - Consent Application and Assessment of Environmental Effects

Beca, 2001b. Geotechnical Investigations Report - Rangitoto Channel Proposed Deepening of Commercial Shipping Lane Beca, 2001c. Rangitoto Channel Deepening Study - Hydrodynamics.

Beca, 2001d. Rangitoto Channel – Proposed Deepening of Commercial Shipping Lane: Wave Study.

Beca, 2001e. Rangitoto Channel Deepening: Sediment Plume and Fate Study Beca, 1997. Waitemata Harbour Tidal Model. Beca, 1996. Fergusson Container Terminal Expansion Assessment of Environmental Effects. Cardno, 2018, Americas Cup Investigations: Numerical Wave Modelling Civil Defence, 2008. Tsunami Evacuation Zones Director’s Guideline for Civil Defence Emergency Management Groups. GNS, 2013. Review of Tsunami Hazard in New Zealand (2013 Update) Golder Associates, 2018. America’s Cup 36: Assessment of Coastal Environmental Effects Associated with the Development of AC36 Facilities Golder Associates, 2011. Port of Auckland Sediment Quality Survey. Golder Associates, 2007. Port of Auckland Sediment Quality Survey. Kingett Mitchell and Associates, 1989. Dredging Requirements for the Port of Auckland - Report No.1. Ministry for the Environment, 2017. Coastal Hazards and Climate Change: Guidance for Local Government (3 rd edition). Mulgor Ltd, 2017. Waves in Hobson West Marina NIWA, 2017. Coastal Inundation by Storm Tides and Waves in Auckland TR2019/017. NIWA, 2012. The Climate and Weather of Auckland, 2 nd edition. NIWA & GNS, (2010). Probabilistic Hazard Analysis and Modelling of Tsunami Inundation for the Auckland Region from Regional Source Tsunami, TR2010/200. NIWA, 2009. Auckland Regional Council Tsunami Inundation Study TR2009/113 NIWA CliFlo website https://cliflo.niwa.co.nz/ NIWA and GNS, 2010. Probabilistic hazard Analysis and Modelling of Tsunami Inundation for the Auckland Region from Regional Source Tsunami.

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| References |

NZTA, 2010. Additional Waitemata Harbour Crossing Existing Environment Report. PIANC, 2008. RecCom Working Group 98 Protecting Water Quality in Marinas. PIANC, 1995. Working Group 24 Criteria for Movements of Moored Ships in Harbours. Thoresen 2014, Port Designers Handbook 3 rd edition USACE (2008) Coastal Engineering Manual, Engineer Manual 1110-2-1100, Volumes 1-7, Coastal Engineering Research Center, Waterways Experiment Station, US Army Corps of Engineer, Vicksburg, USA. USEPA Compliance Policy and Planning Branch, 1985. Coastal Marinas Assessment Handbook. Vennell, 2014. Current Animation and Maps, Lower Waitemata Harbour. Young I.R., 1997. “The growth rate of finite depth wind-generated waves.” In Coastal Engineering Manual (2008) Part 2, USACE.

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| Viaduce Harbour Replacement Bridge |

Appendix A – Tidal Model Study

Wynyard Crossing Bridge Hydraulic Modelling Report Prepared for Panuku Development Auckland Prepared by Beca Limited

12 June 2019

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Creative people together transforming our world | Introduction |

Contents

1 Introduction ...... 1 2 Proposed Developments ...... 2 2.1 AC36 Infrastructure ...... 2 2.2 Wynyard Crossing Bridge Crossing Bridge ...... 2 3 Numerical Modelling ...... 3 3.1 Changes in Tidal Currents ...... 3 3.2 Changes in Tidal Flushing ...... 5 4 Conclusion ...... 6 5 References ...... 6

Appendices

Appendix 1 – Viaduct Harbour Bridge Cross Sections

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| Introduction |

Revision History Revision Nº Prepared By Description Date A Louis Reed For internal review 24/05/2019

B Louis Reed Draft Report 30/05/2019

C Louis Reed Resource Consent Application 12/06/2019

Document Acceptance Action Name Signed Date Prepared by Louis Reed 12/06/2019

Reviewed by Connon Andrews 12/06/2019

Approved by Stephen Priestley 12/06/2019

on behalf of Beca Limited

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| Introduction |

1 Introduction

Beca Ltd (Beca) has been engaged by Panuku Development Auckland (Panuku) to carry out a coastal processes’ assessment for the proposed replacement bridge within the Viaduct Harbour. The bridge will link Te Wero Island and Wynyard Quarter (Karanga Plaza) and is located between the outer and inner Viaduct Harbour as shown in Figure 1.1.

As part of the AC36 project Beca completed a numerical model study to assess the potential effects from the proposed development (Beca and Tonkin & Taylor, 2018). The previous assessment which was used to support resource consent applications, was based on AC36 layout Option D. Subsequently, during detailed design the layout was slightly modified.

For the purposes of this assessment the Beca model has been revised to incorporate the “for construction” AC36 layout and the proposed bridge. The assessment has used the same methodology, assumptions and scenarios and accordingly this report should be read in conjunction with Beca and Tonkin & Taylor (2018). This assessment is based on quantifying the changes in tidal currents and flushing times between the existing Wynyard Crossing Bridge and the proposed Wynyard Crossing Bridge. It considers two scenarios; pre AC36 and post AC36.

Figure 1.1: Aerial photo showing the Wynyard Quarter. Existing wave panels are shown in Cyan. New breakwaters are shown in yellow. Black illustrates new structures. Points V7 to V14 illustrate data extraction points from the numerical model.

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| Proposed Developments |

2 Proposed Developments

2.1 AC36 Infrastructure

The AC36 development works on which this assessment is based on is presented in Figure 1.1. The main modifications from the previous assessment (Option D) include:

● Modification to the Hobson Wharf extension; ● Removal of a wave dissipation panel structure on the eastern side of Hobson Wharf; ● Changes to the wave dissipation panel structure on the western side of Hobson Wharf; ● Changes to the breakwater on Harbour Entrance Protection Wharf.

2.2 Wynyard Crossing Bridge Crossing Bridge

Both the existing and the replacement bridges comprise a central single opening, flanked by a fixed bridge- section each side which are connected to land. The level of the land on the Karanga Plaza side is 5.0m CD and the level on the Te Wero Island side is 4.4m CD. The existing waterway opening will remain unchanged with an overall width of 105m and cross-sectional (facing the tide) area at Mean Sea Level (MSL) of 683 m 2. The relevant approximate metrics for each bridge is given below (note all levels are in terms of Chart Datum (CD)):

Existing Wynyard Crossing Bridge

● Approximate width of bridge: 5.4m ● Fixed section span length (LHS- Karanga Plaza end): 23.6m ● Opening span: 44m ● Fixed section span length (RHS-Te Wero Island end): 37.54m ● No. of piles and cross-sectional area (to MSL) and volume on LHS: 10 no. piles, diameter of 356mm, frontal area (facing the tide) of 23.1m 2, plan area of 1 m 2, and occupying a space of 6.5 m 3. ● Cross-section (to MSL) of bulkhead (for mechanical equipment) or other structural components on LHS: Nil as bulkhead is above 1.92m CD. ● No. of piles and cross-sectional area (to MSL) and volume on RHS: 14 no. piles, diameter of 356mm, frontal area of 32.2m2, plan area of 1.4 m 2, and occupying a space of 9.1 m 3. ● Cross-section (to MSL) of bulkhead (for mechanical equipment) or other structural components on RHS: Nil as bulkhead is above 1.92m CD.

Proposed Wynyard Crossing Bridge

● Approximate width of bridge: 8.8m ● Fixed section span length (LHS- Karanga Plaza end): 28.4m ● Opening span: 43.4m ● Fixed section span length (RHS-Te Wero Island end): 33.1m ● No. of piles and cross-sectional area (to MSL) and volume on LHS: 18 no. piles of varying length, 1020mm diameter, frontal area of 99.6m2, plan area of 14.7 m 2, and occupying a space 79.8 m3. ● Cross-section (to MSL) and volume of bulkhead (for mechanical equipment) or other structural components on LHS: underside of bulkhead is -0.25 CD, area is 26.7m2 occupying a space of 373.2m3 ● No. of piles and cross-sectional area (to MSL) and volume on RHS: 18 no. piles of varying length, 1020mm diameter, frontal area of 99.6m2, plan area of 14.7 m 2, and occupying a space 79.8m3. ● Cross-section (to MSL) and volume of bulkhead (for mechanical equipment) or other structural components on RHS: underside of bulkhead is -0.25 CD, area is 26.7m2 occupying a space of 373.2m3.

Based on the above metrics, the existing bridge has a frontal blockage of (23+32)/683=8%, a plan area of the piles of (1+1.4)=2.4 m 2, and a space blockage of (6.5+9.1)/(683x5.4)=0.4%.

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The proposed replacement bridge will have a frontal blockage of 2(99.6+26.7)/683=37.0%, a plan area of the piles of (14.7+14.7)=29.4 m 2, and a space blockage of 2(79.8+373.2)/(683x8.8)=15.1%. These blockage factors are conservative as they do not take into account locations where the piles line up with the tidal flow.

3 Numerical Modelling

The calibrated and validated Beca numerical model developed for AC36 has been adopted for this assessment (refer to Beca and Tonkin & Taylor, 2018). To capture the effects of the proposed Wynyard Crossing bridge within the new model two impermeable walls were introduced in the model domain. The length of the two walls is equal to the equivalent frontal blockage length of the bulk heads and piles of the proposed Wynyard Crossing bridge. To ensure any changes in tidal current velocities and harbour flushing times due to the construction of the new bridge are captured the following scenarios were modelled:

● Pre AC36 with the existing bridge (Pre AC36 Existing Bridge ); ● Pre AC36 with the proposed bridge ( Pre AC36 Proposed Bridge ); ● Post AC36 with the existing bridge ( Post AC36 Existing Bridge ); and ● Post AC36 with the proposed bridge ( Post AC36 Proposed Bridge ).

Simulations were completed for both average Spring and Neap tidal cycles (refer to Beca and Tonkin & Taylor, 2018).

3.1 Changes in Tidal Currents

Peak tidal velocities for the Viaduct Harbour are presented in Table 3.1 and 3.2 and average tidal velocities are presented in Tables 3.3 and 3.4. Results are presented to 2 decimal places and relative percentage changes in tidal velocities between the existing Wynyard Crossing bridge and the proposed Wynyard Crossing bridge scenarios is shown.

Table 3.1: Peak spring tide velocities for Viaduct Harbour

Pre AC36 Pre AC36 % Post AC36 Post AC36 % Location Existing Proposed Change Existing Proposed Change Bridge Bridge Bridge Bridge V7 0.14 0.14 0.0 0.06 0.06 0.0 V8 0.11 0.11 0.0 0.06 0.06 0.0 V9 0.04 0.05 25.0 0.04 0.04 0.0 V10 0.10 0.10 0.0 0.02 0.02 0.0 V11 0.02 0.02 0.0 0.01 0.01 0.0 V12 0.00 0.00 0.0 0.00 0.00 0.0 V13 0.01 0.01 0.0 0.01 0.01 0.0 V14 0.00 0.00 0.0 0.00 0.00 0.0

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Table 3.2: Peak neap tide velocities for Viaduct Harbour

Pre AC36 Pre AC36 % Post AC36 Post AC36 % Location Existing Proposed Change Existing Proposed Change Bridge Bridge Bridge Bridge V7 0.09 0.09 0.0 0.04 0.04 0.0 V8 0.07 0.07 0.0 0.04 0.04 0.0 V9 0.03 0.03 0.0 0.02 0.03 50.0 V10 0.05 0.05 0.0 0.01 0.01 0.0 V11 0.01 0.01 0.0 0.01 0.01 0.0 V12 0.00 0.00 0.0 0.00 0.00 0.0 V13 0.01 0.01 0.0 0.01 0.01 0.0 V14 0.00 0.00 0.0 0.00 0.00 0.0

Table 3.3: Average spring tide velocities for Viaduct Harbour

Pre AC36 Pre AC36 % Post AC36 Post AC36 % Location Existing Proposed Change Existing Proposed Change Bridge Bridge Bridge Bridge V7 0.08 0.08 0.0 0.02 0.02 0.0 V8 0.05 0.05 0.0 0.03 0.03 0.0 V9 0.03 0.03 0.0 0.02 0.03 50.0 V10 0.04 0.04 0.0 0.01 0.01 0.0 V11 0.01 0.01 0.0 0.01 0.01 0.0 V12 0.00 0.00 0.0 0.00 0.00 0.0 V13 0.01 0.01 0.0 0.01 0.01 0.0 V14 0.00 0.00 0.0 0.00 0.00 0.0

Table 3.4: Average neap tide velocities for Viaduct Harbour

Pre AC36 Pre AC36 % Post AC36 Post AC36 % Location Existing Proposed Change Existing Proposed Change Bridge Bridge Bridge Bridge V7 0.05 0.05 0.0 0.01 0.01 0.0 V8 0.04 0.04 0.0 0.02 0.02 0.0 V9 0.02 0.02 0.0 0.01 0.02 100.0 V10 0.02 0.02 0.0 0.00 0.00 0.0 V11 0.01 0.01 0.0 0.01 0.01 0.0 V12 0.00 0.00 0.0 0.00 0.00 0.0 V13 0.00 0.00 0.0 0.00 0.00 0.0 V14 0.00 0.00 0.0 0.00 0.00 0.0

The results suggest the following: ● The proposed bridge generally results in an increase of tidal velocities in the vicinity of the bridge foundations (refer to location V9). ● There is no discernible effect on tidal currents within the inner or outer Viaduct Harbour from the proposed bridge configuration.

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| Numerical Modelling |

3.2 Changes in Tidal Flushing Water quality has been assessed by determining harbour flushing times. Flushing times are typically calculated as the time required to reduce an initial pollutant concentration within a semi enclosed water body to an acceptable level. Consistent with Beca and Tonkin & Taylor (2018) the e-folding method has been adopted. The e-folding method considers the time it takes for a contaminant introduced to a uniformly mixed body of water to achieve a dilution level of 37%. That is the time taken for 63% of the dye to be flushed out of the Marina. E-folding times of less than 4 days (96 hours) is considered “good”, e-folding times between 4 - 10 days (96 -240 hours) is considered “fair” and e-folding times greater than 10 days is considered “poor”.

Flushing times for the Viaduct Harbour are shown in Table 3.5 and 3.6 for Spring and Neap tides respectively. Green represents a “good” flushing time and orange represents a “fair” flushing time.

Table 3.5: e-folding times for Inner and Outer Viaduct Harbours- Spring tide and 0 m/s wind

Pre AC36 Pre AC36 % Post AC36 Post AC36 % Location Existing Proposed Change Existing Proposed Change Bridge Bridge Bridge Bridge V7 7.5 7.5 0.0 13.8 13.8 0.0 V8 8.0 8.0 0.0 27.0 27.0 0.0 V9 31.0 31.3 1.0 43.3 43.3 0.0 V10 19.0 19.0 0.0 35.0 34.8 -0.6 V11 44.8 45.0 0.4 57.0 57.0 0.0 V12 74.5 75.3 1.0 68.0 65.8 -3.2 V13 80.5 81.3 1.0 93.3 93.5 0.2 V14 107.8 110.8 2.8 121.5 122.3 0.7

Table 3.6: e-folding times for Inner and Outer Viaduct Harbours- Neap tide and 0 m/s wind

Pre AC36 Pre AC36 % Post AC36 Post AC36 % Location Existing Proposed Change Existing Proposed Change Bridge Bridge Bridge Bridge V7 14.0 14.0 0.0 6.3 6.3 0.0 V8 17.5 17.5 0.0 28.5 28.5 0.0 V9 43.0 43.3 0.7 55.3 55.5 0.4 V10 20.8 20.8 0.0 47.0 47.0 0.0 V11 69.5 69.8 0.4 81.3 81.5 0.4 V12 100.3 101.3 0.0 92.5 89.3 -3.5 V13 107.3 118.0 10 119.0 119.8 0.7 V14 146.5 151.8 3.6 157.5 160.0 1.6

The e-folding times suggest the following:

● The proposed bridge has no discernible effects on e-folding times within the Viaduct Harbour. ● Breakwater changes during detailed design to the AC36 consented layout resulted in a slightly different layout which subsequently improved flushing times.

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| Conclusion |

4 Conclusion

In conclusion the revised Beca numerical modelling presented in Beca and Tonkin & Taylor (2018) indicates the following:

● Overall, there is no discernible difference in current velocities within the viaduct harbour when the proposed bridge is introduced to the model; ● There is an increase in current velocity just at the proposed bridge (Point V9); ● Consistent with the tidal current velocities there is no discernible difference in Viaduct Harbour flushing times for the proposed bridge.

5 References

Beca and Tonkin and Taylor, 2018: America’s Cup 36. Coastal Processes and Dredging Technical Report.

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| References |

Appendix 1 – Viaduct Harbour Bridge Cross Sections

Wynyard Crossing Bridge Hydraulic Modelling Report | 3911594 | NZ1-16204614-8 0.8 | 12 June 2019 - Rev C | 7

Drawing Plotted: 24 May 2019 5:09 PM www.beca.com

3 4 SE-0130 SE-0130

KARANGA LEAF SUPERSTRUCTURE ℄ ℄ TE WERO LEAF SUPPORT SUPPORT SPAN LENGTH - 47500 SUPERSTRUCTURE

RC FLOATING PONTOON WITH FENDER FLOATING PONTOON WITH FENDER HEADSTOCKS KARANGA APPROACH TE WERO PIER TE WERO APPROACH BALUSTRADE 1 2 13200 LONG NOM SE-0130 SE-0130 13500 LONG NOM 18000 LONG NOM EXPANSION JOINT KARANGA PLAZA EXPANSION JOINT TE WERO ISLAND

+5.00m GL +4.40m GL +6.30m +6.40m U/S DECK AT MIDSPAN +3.39m MHWS CLEARANCE ENVELOPE 3000 RC PIER RC PIER 10000 WIDE x 3000 HIGH MIN RC +0.00m DATUM +0.41m MLWS VESSEL CORRIDOR (MHWS) HEADSTOCKS

36000 CLEAR WIDTH

-4.30m APPROX BED LEVEL -4.80m APPROX BED LEVEL

BORED PILES WITH STEEL CASINGS BORED PILES WITH STEEL CASINGS

A BRIDGE ELEVATION 0110 1:200 (A1), 1:400 (A3) www.beca.com

DRAFT ONLY NOT FOR CONSTRUCTION FOR INFORMATION NOT FOR CONSTRUCTION

Drawing Originator: Original Design Approved For Client: Project: Title: Discipline

V. Guillen 27.05.19 3911594-SE-0120.DWG Scale (A1) Construction* Drawn P. Noble 27.05.19 WYNYARD CROSSING BRIDGE GENERAL ARRANGEMENT AS SHOWN STRUCTURAL ENGINEERING Dsg Verifier Reduced PRELIMINARY DESIGN ELEVATION Drawing No. Rev. A ISSUED FOR INFORMATION PN VG WP 27.05.19 Scale (A3) Dwg Check Date No. Revision By Chk Appd Date HALF SHOWN * Refer to Revision 1 for Original Signature 3911594-SE-0120 A Document No.

DO NOT SCALE IF IN DOUBT ASK. | References |

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