sh20 manukau harbour crossing projectsh20 manukau harbour crossing project – assessment of...

SH20 Manukau Harbour Crossing Project Assessment of Environmental Effects

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NOTE: Report annotated September 2006 to refer to project updates described in August 2006 Section 92 Response Reports. Refer to notes on following page

SH20 Manukau Harbour Crossing Project Annotation Notes

Reference in text

Note

1 Proposed form of interchange revised August 2006 to “quarter diamond” configuration. Refer to August 2006 Interchange Report and s.92 Response Report to Auckland City Council.

2 Temporary reclamations no longer proposed. Coastal Permit application for temporary reclamation at Onehunga Harbour Road withdrawn August 2006.

3 Extent and area of proposed reclamation revised. Refer August 2006 s.92 Response Report to Auckland Regional Council.

4 Coastal Permit applications for replacement of Old Mangere Bridge were lodged in May 2006 but withdrawn in August 2006 to enable further consideration of design options. General information relating to the proposed replacement bridge as described within this AEE remains relevant. New consent applications will be lodged at a later date as appropriate. The concept design for the replacement bridge will be confirmed at that time.

5 The proposed designation no longer includes the Manukau Cruising Club lease area (refer August 2006 s.92 Response Report to Auckland City Council). The building, carparking area and boat ramp are no longer directly affected by the works.

6 Stormwater management proposals revised. Refer August 2006 s.92 Response Report to Auckland Regional Council.

28 September 2006 P.T.O

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SH20 Manukau Harbour Crossing Project Annotation Notes

Background

Transit’s proposals for the Manukau Harbour Crossing Project were submitted to Auckland City Council, Manukau City Council and the Auckland Regional Council in May 2006.

All three Councils requested further information from Transit, and this information was provided in August 2006. The requests for further information were made in accordance with Section 92 of the Resource Management Act 1991.

Preparation of this additional information has resulted in some revisions to the original proposals, and these are reflected in supplementary documentation dated 28 August 2006. The key revisions made are summarised below.

Key Revisions

• The proposed form of the motorway interchange at Gloucester Park has been revised from a “diamond” to a “quarter diamond” configuration.

• The extent of reclamation proposed within the Manukau Harbour has been reduced – only one area of reclamation is now proposed, this being along Onehunga Harbour Road and Orpheus Drive, east of the Manukau Cruising Club.

• The Manukau Cruising Club and associated parking area is no longer affected by the proposed works.

• Coastal Permit applications relating to demolition of the old Mangere Bridge and replacement with a new pedestrian and cycle bridge have been withdrawn to enable further consideration of design options.

• Stormwater management proposals have been refined to offer an improved degree of treatment prior to discharge to the receiving environment.

Notification Documentation

The documents submitted with the consent applications and Notices of Requirement in May 2006, along with the more recent information prepared in response to requests from the Councils for further information are available in full for viewing as part of the public notification process.

To avoid confusion, the May 2006 documentation has been annotated where appropriate to refer to the recent revisions summarised above and described in the August 2006 reports.

Reports Referred to in Annotations – Full Titles

Title Date Status / revision

August 2006 Interchange Report

Report: SH20 Manukau Harbour Crossing Project - Gloucester Park Interchange: Further Consideration of Alternatives

28 August 2006 Rev A Final

s.92 Response Report to Auckland City Council

Report: Response to Auckland City Council Requests for Further Information under Section 92 of the Resource Management Act 1991

28 August 2006 Final

s.92 Response Report to ARC

Report: Response to Auckland Regional Council Request for Further Information under Section 92 of the Resource Management Act 1991

28 August 2006 Final

SH20 Manukau Harbour Crossing Project – Assessment of Environmental Effects

Document Ref: Glossary of terms.doc Page ii Status: Final 19/05/06

Table of Contents Volume 1 Notice of Requirement and Assessment of Environmental Effects NOR - Alteration to Designation........................................................................Separate Document Notice of Requirement ......................................................................................Separate Document Resource Consents ARC Forms.......................................................................Separate Document Chapter 1 Overview ..................................................................................................01 - 10 Chapter 2 The Project...............................................................................................11 - 38 Chapter 3 Consideration of Alternatives ...................................................................39 - 76 Chapter 4 Statutory Considerations for Transit NZ...................................................77 - 80 Chapter 5 Existing Environment ...............................................................................81 - 93 Chapter 6 Assessment of Environmental Effects....................................................94 - 135 Chapter 7 Consultation .........................................................................................136 - 147 Chapter 8 Statutory Assessment ..........................................................................148 - 157 Chapter 9 Relevant Plan Provisions .....................................................................158 - 212 Volume 2 (Parts A, B and C) Technical Appendices Appendix 1 Detailed Description of Physical Works Appendix 2 South Western Corridor Strategy Study 2005 Executive Summary Appendix 3 Bridge and Structures Report Appendix 4 Consultation Reports Appendix 5 Gloucester Park Interchange Auckland City Council Alternative Appendix 6 Noise and Vibration Assessment Appendix 7 Air Quality Assessment Appendix 8 Urban Design Assessment Appendix 9 Landscape and Visual Assessment Appendix 10 Traffic Issues Assessment Appendix 11 Archaeology and Heritage Assessment Appendix 12 Tuff Ring Report Appendix 13 Social Impact Assessment Appendix 14 Coastal Marine Ecology and Water Quality Assessment Appendix 15 Coastal Processes Assessment Appendix 16 Stormwater Management Assessment Appendix 17 Geotechnical Appraisal Report


Document Ref: Glossary of terms.doc Page iii Status: Final 19/05/06

Appendix 18 Erosion and Sediment Control Plan Appendix 19 Draft Environmental Management Plan Appendix 20 Draft Environmental Monitoring Guidelines Appendix 21 ARC Relevant Plan Provisions - Relevant Objectives and Policies Considered Appendix 22 Recommended Conditions Volume 3 Scheme Plans and Drawings


Document Ref: Glossary of terms.doc Page iv Status: Final 19/05/06

Glossary of Terms-

ACC Auckland City Council ACFS Auckland City Freight Strategy ACGMS Auckland City: Growth Management Strategy 2003 AEE Assessment of Environmental Effects ARC Auckland Regional Council ARCS Auckland Regional Cycling Strategy 2002 ARGS Auckland Regional Growth Strategy ARLTS Auckland Regional Land Transport Strategy 2005 ARPC Operative Auckland Regional Plan: Coastal ARPSC Operative Auckland Regional Plan: Sediment Control ARPS Auckland Regional Policy Statement ARTA Auckland Regional Transport Authority ARWS Auckland Regional Walking Strategy 2002 ASHS Auckland State Highway Strategy CMA Coastal Marine Area CPA1 Coastal Protection Area 1 CPA2 Coastal Protection Area 2 CMP Construction Management Plan CPTED Crime Prevention Through Environmental Design DARLTS Draft Auckland Regional Land Transport Strategy 2006-2016 Duplicate Bridge New SH20 Motorway Bridge across the Manukau Harbour EMP Environmental Management Plan EMG Environmental Monitoring Guidelines GPI Gloucester Park Interchange Harbour Manukau Harbour HCV Heavy Commercial Vehicle LGA Local Government Act 2002 LTA Land Transport Act 1998 LTMA Land Transport Management Act 2003 Mangere Bridge Existing SH20 Motorway Bridge across the Manukau Harbour Mangere Footbridge Pedestrian and cycle bridge to replace the Old Mangere Bridge MCC Manukau City Council NES National Emission Standards NIWA National Institute of Water and Atmospheric Research Ltd NOR Notice of Requirement NSHS National State Highway Strategy NUO Network Utility Operator NZCPS New Zealand Coastal Policy Statement NZHPT New Zealand Historic Places Trust NZNLTS New Zealand National Land Transport Strategy Old Mangere Bridge The existing low level pedestrian and cycle connection between


Document Ref: Glossary of terms.doc Page v Status: Final 19/05/06

Onehunga and Mangere Bridge Townships. One Tree Hill Maungakiekie Opus Opus International Consultants PARPALW Proposed Auckland Regional Plan: Air, Land and Water Port The Port of Onehunga Port Road Ramp Ports access to GPI from Onehunga Harbour Road. Project SH20 Manukau Harbour Crossing Project as described in

Volume 1, Chapter 2, of this report Project Area SH20 area between Queenstown Rd and Walmsley Road Project Objectives Described in Chapter 2 of this Report RA Regional Authority RAQTs Regional Air Quality Targets RLTS Regional Land Transport Strategy 2003 RLTSSD Regional Land Transport Strategy 2005 Summary Document RMA Resource Management Act 1991 SH1 State Highway 1 SH16 State Highway 16 SH18 State Highway 18 SH20 State Highway 20 SWTC South Western Transport Corridor TDM Travel Demand Management TLA Territorial Local Authority TP90 Auckland Regional Council Technical Publication No 90 (TP90)

Erosion and Sediment Control Guidelines for Land Disturbing Activities

T10 Design guideline manual; Stormwater treatment devices 2003 TP108 TP108 Guidelines for stormwater runoff modelling in the

Auckland Region. TPPM Transit Planning Policy Manual 2005 Transit Transit New Zealand Tuff Ring Hopua tuff ring located in Gloucester Park WRR Western Ring Route

SH20 Manukau Harbour Crossing Project – Assessment of Environmental Effects Chapter 1 – Introduction and Overview

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Page 1 Status: Final 19/05/06

1 Introduction and Overview

1.1 Introduction

The SH20 Manukau Harbour Crossing is a key part of the Western Ring Route. Once completed, the Western Ring Route will provide a genuine alternative to SH1 between Manukau City and Albany via SH20, SH16 and SH18. Transit plans to actively manage traffic flows on both the Western Ring Route and SH1 to contribute to the long-term sustainability of the network overall and to provide more reliable travel times.

The completion of the SH20 and Western Ring Route will provide quicker and safer travel between Waitakere, Auckland and Manukau Cities. It will relieve congestion on the central motorway network and provide a strategic alternative route across the region.

The SH20 Manukau Harbour Crossing Project (the Project) covers the stretch of State Highway 20 (SH20) between Queenstown Road and Walmsley Road and is shown at Figure 1.

The overall objective of the Project is to increase capacity over the Manukau Harbour and to improve connections to arterial routes. The Project will widen SH20 between Queenstown Road and Walmsley Road Interchanges from four lanes to six lanes, with bus priority on shoulder lanes where practical, and from four lanes to eight lanes between Rimu Road and Gloucester Park Interchanges.

The existing Mangere Bridge will be duplicated to the east (i.e. a second bridge will be built) so that four traffic lanes and a shoulder lane for bus priority will be provided in each direction. Pedestrian and cyclist usage will continue to be provided along the line of the Old Mangere Bridge by way of a replacement structure (Mangere Footbridge).

The existing Gloucester Park split interchange will be upgraded to a grade separated diamond arrangement connected to Neilson Street and Orpheus Drive. The Project will require alterations to local streets (Rimu Road/Mahunga Drive, Neilson Street/Gloucester Park Road, Orpheus Drive/Onehunga Harbour Road) and modification to access arrangements to surrounding properties affected by the upgraded interchange at Gloucester Park Road.

The Rimu Road/Mahunga Drive Bridge will be replaced to allow motorway widening. Further south at Tararata Creek, a new off ramp bridge and widened motorway bridge is required. At the Queenstown Road Bridge, additional retaining walls at abutments will be required. The Beachcroft Avenue and Hastie Avenue footbridges will also need to be replaced to allow motorway widening.

The Project involves coastal reclamation or earthworks within the Coastal Marine Area (CMA) and includes temporary and permanent reclamations to construct the Duplicate Bridge, replacement of the Old Mangere Bridge with a pedestrian/cycle bridge including a fender protection structure, construction of a new off ramp over Tararata Creek and

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coastal reclamation adjacent to Orpheus Drive to accommodate the upgrade of Gloucester Park Interchange.

Figure 1.1 Location Plan


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Under the Resource Management Act 1991 (RMA), the existing motorway corridor (being part of the State highway network) is designated in the Operative Auckland City District Plan: Isthmus (1999) and the Operative Manukau City District Plan (2002). The following Notices of Requirements and resource consents have been lodged.

Notice of Requirement for an alteration to a designation – Manukau City Council

To accommodate the works outside of the designation, an alteration to the designation is required (under s181 RMA) for that section of works located in Manukau City. The proposed works comprise the construction, operation and maintenance of a motorway and associated works on land currently outside the existing designation.

Notice of Requirement for a new designation – Auckland City Council

To accommodate works for that section of the Project located in Auckland City a new designation has been lodged (under s168 RMA) for an upgraded interchange and the construction, operation and maintenance of motorway and associated works currently outside the existing designation.

Resource Consents

The Project includes the reclamation of land, the duplication of the existing Mangere Bridge, the diversion and discharge of stormwater, earthworks and other works in the Coastal Marine Area (CMA) which require resource consents (under s9, s12, s14 and s15 RMA) from the Auckland Regional Council (ARC).

The following table summarises the activities requiring Resource Consent from the ARC:

Auckland Regional Plan: Coastal 2004

RMA Sec.

Description of the Activity Relevant Rule Activity Status

Tararata Creek Bridges

S12 Coastal Permit application for the construction of a new off ramp over Tararata Creek and for widening and strengthening of the existing SH20 motorway bridge, including:

• Construction activities within the CMA including vegetation removal, disturbance of sediment, temporary structures and erosion and sediment control measures; and

• Ongoing use, operation and maintenance of the new motorway bridge.

Rule 12.5.18

Rule 16.5.14

Rule 11.5.5

Discretionary

Discretionary

Discretionary


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RMA Sec.


S12 Coastal Permit application for occupation of the CMA by the SH20 southbound off-ramp bridge and SH20 motorway bridge at Tararata Creek.

Rule 10.5.9 Discretionary

Mangere Footbridge – Pedestrian / Cycle Bridge and Fender Protection Structure

S12 Coastal Permit application for the demolition of the old Mangere Bridge and replacement with a new pedestrian / cycle bridge and adjacent fender protection structure, including:


• Ongoing use, operation and maintenance of the new pedestrian / cycle bridge and fender protection structure.

Rule 12.5.18

Rule 16.5.14

Rule 11.5.5

Discretionary

Discretionary

Discretionary

S12 Coastal Permit application for occupation of the CMA by a pedestrian and cycle bridge and adjacent fender protection structure between Coronation Road in Mangere and Onehunga Harbour Road in Onehunga.


Duplicate SH20 Motorway Bridge

S12 Coastal Permit application for the construction of the duplicate SH20 Mangere Bridge including temporary works for construction jetties and barge access ramps on the southern foreshore, including:

• Construction activities within the CMA including vegetation removal, disturbance of sediment, temporary structures and erosion and sediment control measures: and

• Ongoing use, operation and maintenance of the new motorway bridge.

Rule 12.5.18

Rule 16.5.14

Rule 11.5.5

Discretionary

Discretionary

Discretionary

S12 Coastal Permit application for occupation of the CMA by the duplicate SH20 Mangere Bridge over the Manukau Harbour


Onehunga Harbour Road Reclamation (Temporary)

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RMA Sec.


S12 Coastal Permit application for the construction of a temporary reclamation associated with the construction of the duplicate SH20 Mangere Bridge, including disturbance to the seabed, deposition of material, extension of existing culverts and temporary occupation of the CMA.

13.5.3

10.5.10

Non-complying

Non-complying

Orpheus Drive Reclamation (Temporary and Permanent)

S12 Coastal Permit application for the construction of a permanent reclamation adjacent to Orpheus Drive and Onehunga Harbour Road measuring approximately 1.4ha in area and 550m in length, and including extension of an existing culvert outfall structure, and for the construction and subsequent removal of a temporary reclamation measuring 0.2ha in area, including:


• Ongoing use, operation and maintenance of the reclamation.

Rule 13.5.5

Rule 13.5.3

Rule 16.5.14

Rule 11.5.5

Restricted Coastal Activity

Non-complying

Discretionary

Discretionary

S12 Coastal Permit application for permanent occupation of the CMA by the reclamation of land for realignment of Orpheus Drive and Onehunga Harbour Road, measuring approximately 1.4ha in area and 550m in length; and for temporary occupation of the CMA by the reclamation of land associated with the construction of the Gloucester Park Interchange of SH20.


Discharge of Stormwater into the CMA

S15 Coastal Permit application for the discharge of contaminants or water into coastal water arising from the collection treatment and discharge of stormwater treatment associated with SH20 Manukau Harbour Crossing Project.

Rule 20.5.6

Rule 20.5.7

Discretionary

Non-complying

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RMA Sec.


S12 Coastal Permit application for the construction of stormwater outfalls within the CMA at:

• Mahunga Drive; and

• Waterfront Road Reserve (proposed Pond 4).

Rule 12.5.18

Rule 12.5.22

Discretionary

Non-complying

S12 Coastal Permit application for the permanent occupation of the CMA by stormwater outfall structures at:

• Mahunga Drive; and

• Waterfront Road Reserve (proposed Pond 4).

Rule 10.5.9

Rule 10.5.10

Discretionary

Non-complying

Proposed Auckland Regional Plan: Air, Land and Water 2005

RMA Section

Description of the Activity Relevant

Rule Activity Status

Tararata Creek Stormwater Management Devices

S14 and 15

Resource consent application for the diversion and discharge of stormwater including contaminants from new impervious areas greater than 5000m2 including associated with the construction and operation of a road.


Auckland Regional Plan: Sediment Control 2001

RMA Section Description of the Activity

Relevant Rule

Activity Status

S9 Resource consent application for earthworks and sediment control and vegetation removal to undertake 22ha of earthworks within the Sediment Control Protection Area.

Rule 5.4.3.1 Restricted discretionary

Additional Resource Consents

Some additional activities associated with the Project may also require resource consents, including:

• Reconstruction and / or relocation of existing boat ramp under the southern abutment of the existing Mangere Bridge;


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• Removal of demolition materials and reinstatement of the coastal edge under the southern abutment of the existing Mangere Bridge;

• Reconstruction of existing outlet structures or construction of new outlet structures within the CMA associated with stormwater discharges from the SH20 motorway;

• Dredging of the seabed in front of the Manukau Cruising Club;

• Removal and reconstruction of part of the existing breakwater within the CMA;

• Relocation of Sea Scouts building to the proposed Orpheus Drive reclamation; and

• Consent for works within a watercourse (opposite Hill Street, Onehunga) for the reconstruction of a culvert associated with the construction of the SH20 southbound off-ramp at the proposed Gloucester Park Interchange.

These additional activities relate to matters of detail which will be developed as part of the detailed design process. As these additional activities are not critical to the project as a whole, it is anticipated that the required consents would be sought at a later date once the detailed design has progressed.

Other Consents and Approvals

Mangere Bridge was constructed from 1976 and was granted resource consent under Harbours Act 1950. This consent has subsequently expired and a Coastal Permit for the occupation of the sea bed for an existing bridge structure for use by vehicular traffic has been lodged (ARC ref: 31113).

The Project also requires a s.12 general authority under the Historic Places Act 1993 to destroy, damage or modify archaeological sites, as well as a range of building consents under the Building Act 2004. These applications will be lodged with the relevant authorities at a later date.

1.2 Transit New Zealand’s Role and Responsibilities

The Transit New Zealand Act 1989 (TNZA) constituted Transit and defined its functions and powers. It remains a key statutory basis for Transit alongside the LTMA. The TNZA confers on Transit the power to declare roads, State highways and motorways with the specific powers of control that State highway and motorway declarations infer (refer, in particular, to sections 61 and 80 of the TNZA). SH20 (of which the Manukau Harbour Crossing Project is part) has the legal status of motorway under section 71 of the TNZA.

In 2003, the Land Transport Management Act (LTMA) was enacted. The LTMA’s purpose is to “… contribute to the aim of achieving an integrated, safe, responsive and sustainable land transport system”.

Transit’s objective (under section 77 of the LTMA) is “to operate the State highway system in a way that contributes to an integrated, safe, responsive and sustainable land transport


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system”. Under section 77(2), in meeting its objective, the LTMA requires Transit to exhibit a sense of ‘social and environmental responsibility’, consistent with the overall purpose of the LTMA (Section 3). Exhibiting a sense of social and environmental responsibility is further detailed in the LTMA to include:

(a) Avoiding, to the extent reasonable in the circumstances, adverse effects on the environment;

(b) Taking into account the views of affected communities;

(c) Giving early and full consideration to land transport options and alternatives in a manner that contributes to paragraphs (a) and (b); and

(d) Providing early and full opportunities for the persons and organisations listed in section 15(1) to contribute to the development of its land transport programmes.

The purpose of the LTMA, including the key outcomes identified for activities and land transport programmes, together with Transit’s objective under the LTMA have been used in defining assessment criteria for the evaluation of options discussed in Chapter 3 of this report. The consultation section of this Assessment of Environmental Effects (Chapter 7) outlines the consultation undertaken to fulfil the requirements of the LTMA, in addition to other statutory requirements under the RMA. Chapter 3 contains the evaluation of alternatives considered as part of the SWTS which confirmed the need for this Project.

1.3 Overview of Documentation

This Assessment of Environmental Effects (AEE) contains information in support of the Notices of Requirement (NOR) and resource consent applications for the Project.

The documentation provides background information, assesses various issues and effects and/or provides further technical information to support the NORs and the consent applications. The documents comprise the following:

• SH20 Manukau Harbour Crossing Project – Volume 1 Assessment of Environmental Effects (AEE) and Attachments;

• SH20 Manukau Harbour Crossing Project – Volume 2 Technical Appendices – and

• SH20 Manukau Harbour Crossing Project – Volume 3 Scheme Plans and Drawings.

The relationship between these documents and technical appendices is set out on the following page in Figure 2.

The AEE has been prepared in accordance with the relevant provisions of the RMA and includes the following:

• Details of the proposed works (Chapter 2);


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• An outline of alternatives considered (Chapter 3);

• A description of the existing SH20 network between Walmsley Road and Queenstown Road (Chapter 5);

• An assessment of the actual and potential effects of the Project (Chapter 6);

• Measures which will be implemented in order to mitigate potential adverse effects (Chapter 6);

• Details of the consultation undertaken and proposed (Chapter 7); and

• An assessment of the Project against the relevant statutory and non-statutory documents (Chapters 8 and 9).


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Figure 1.2 Notices of Requirement and Resource Consent Supporting Documentation

Volume 1 - SH 20 Manukau Harbour Crossing Project:

Assessment of Effects

Volume 2 - Technical Appendices-

Appendix 01 Detailed Description of Physical Works

Appendix 02 South Western Corridor Strategy Study 2005 Executive Summary Appendix 03 Bridge and Structures Report Appendix 04 Consultation Reports Appendix 05 Gloucester Park Interchange

Assessment of ACC Alternative Appendix 06 Noise and Vibration Assessment Appendix 07 Air Quality Assessment Appendix 08 Urban Design Assessment Appendix 09 Landscape & Visual Assessment Appendix 10 Traffic Issues Assessment Appendix 11 Archaeology and Heritage

Assessment Appendix 12 Tuff Ring Report Appendix 13 Social Impact Assessment Appendix 14 Coastal Marine Ecology and

Water Quality Assessment Appendix 15 Coastal Processes Assessment Appendix 16 Stormwater Management

Assessment Appendix 17 Geotechnical Appraisal Report Appendix 18 Erosion and Sediment Control

Plan Appendix 19 Draft Environmental Management

Plan Appendix 20 Draft Environmental Monitoring

Guidelines Appendix 21 ARC Objectives and Policies Appendix 22 Proposed Conditions

Volume 3 - Plans

Scheme Overview – Drawing Schedule General Arrangement and Long Sections Bridge Plans Construction Sequencing Stormwater Drainage Plans Landscaping Plans Temporary Works and Construction Works Areas Services Plans Erosion and Sediment Control Plans

SH 20 Manukau Harbour Crossing Project – Assessment of Environmental Effects Chapter 2 – The Project


2 The Project

2.1 Overview

The SH20 Manukau Harbour Crossing Project (the Project) forms part of Transit’s Western Ring Route Strategy to provide a western corridor through the Auckland region as a viable alternative to SH1. The corridor, which includes SH20, 16 and 18, requires the upgrading of SH20 between Manukau and Waterview. Other projects forming part of the Western Ring Route are:

• SH20 to SH1 Manukau Extension;

• SH20 Mt Roskill Extension;

• SH20 Waterview Connection;

• SH16/18 Upper Harbour Corridor.

The Western Ring Route is shown on Figure 2.1 below and the SH20 Projects are shown on the following Figure 2.2.

Figure 2.1 Western Ring Route



Figure 2.2 SH20 Projects

To realise the full benefits of these works, the Project must be considered as an integral part of this wider corridor upgrade. The purpose of these works is to provide congestion relief and accessibility improvements across the entire Auckland urban motorway network by creating an efficient strategic alternative to SH1.



2.2 Strategic Context

Congestion has been identified as a key regional transport issue for Auckland.

Transit’s 10 Year State Highway Forecast (2005/06 – 2014/15) notes that:

“Traffic growth in Auckland is continuing at around two to four percent per year driven by population growth and [coupled with] the relatively cheap cost of travel… is causing increased congestion particularly for peak period commuter trips and freight”.

The continued increase in traffic growth means that the issue of congestion is no longer confined to morning and afternoon peak periods. Many sections of the network are increasingly becoming congested during the middle of the day and at weekends.

SH20 is a critical component of Auckland’s motorway network and the Project will assist to address congestion on the South Western Motorway. Current traffic demand on Mangere Bridge and the adjacent motorway exceeds available capacity, frequently causing congestion and extended journey times. The Project caters for both local trips (between Mangere Bridge and Onehunga) and longer strategic trips (from north to south including access to/from the airport).

It is projected that the strategic importance of this route will increase significantly following the completion of the proposed extensions to the motorway north (SH20 Mt Roskill Extension Project) and to the south (SH20 Manukau Extension Project) of the Project. It is anticipated that these related projects will lead to significantly increased flows across the Manukau Harbour.

The Onehunga – Pakuranga Corridor is shown on Figure 2.2. This corridor links SH20 at Onehunga to SH1 at Mt Wellington, and on to Ti Rakau Drive at Pakuraga. The route consists of Neilson St, Church St, the South Eastern Highway and the Pakuranga Highway. The 2005 Auckland Regional Land Transport Strategy (ARLTS) defines the corridor as a key strategic route (ARLTS Map 7.2).

The Onehunga – Pakuranga Corridor is a key east – west connection. It provides strategic access between the eastern areas of Auckland and Manukau cities with the Auckland International Airport (including surrounding commercial areas), Waitakere City and western areas of Auckland City. The commercial areas adjacent to the corridor also generate traffic that utilizes the route.

Therefore, the Onehunga – Pakuranga corridor is an integral consideration for improving overall links, connectivity, geometry and safety within the Project area.

Transit has long recognised the strategic importance of the Project as outlined above. As a result, a strategy study for the Queenstown Road to Walmsley Road section of SH20 was undertaken from 2000 to 2002 to determine route options to improve capacity. This is outlined in Volume 1 Chapter 3 Consideration of Alternatives, of this AEE.



The South Western Transport Corridor (SWTC) Strategy Study was undertaken during 2005 to determine the most appropriate package of projects to deliver the objectives of the LTMA and Auckland Regional Growth Strategy (ARGS). This confirmed the overall strategy for the SWTC, and the need for the Project. Following the SWTC Strategy Study the objectives of the Project were finalised.

2.3 Project Objectives

The Project has the following objectives:

To provide an integrated, safe, responsive and sustainable land transport system on the existing South Western Corridor between SH20A interchange and SH20 Mt Roskill extension, that will:

• provide a high standard strategic transport connection as part of the regional alternative route to State Highway 1 connecting Manukau and Auckland cities (the Western Ring Route);

• improve efficiency and safety in this part of the existing South Western Corridor; and

• improve access between the South Western and Onehunga-Pakuranga Corridors.

2.4 Existing Designation

2.4.1 State Highway Designations

Transit has existing designations for the SH20 corridor in both the Operative Auckland City District Plan: Isthmus (1999) and the Operative Manukau City District Plan 2002. Maps of the existing and proposed designations are attached to the NORs. The details of Transit’s existing designations for SH20 are described below.

ACC Designation

Designation Number: A07-01.

Description of Designation: Motorway.

Requiring Authority: Transit New Zealand.

MCC Designation

Designation Number: 182.

Description of Designation: South Western Motorway (State Highway 20).

Requiring Authority: Transit New Zealand.



Transit has given notice to ACC and MCC of its requirement to alter its boundaries and to seek a designation for new areas, the details of which are set out in the attached NORs.

2.4.2 Other Designations

The following designations are fully or partly overlain by the designations proposed for the Project.

ACC Designation

ACC has an existing ramps designation between the end of Selwyn Street and the middle of Gloucester Park for an interchange with SH20. The specified term for this designation is 12 years from inclusion within the Operative Auckland City District Plan (Isthmus Section 1999). It is understood that Auckland City have no plans to utilise this designation.

Designation Number: H10-32.

Description of Designation: Proposed Motorway Access Ramps, Gloucester Park.

Requiring Authority: ACC.

Rail Designation

The New Zealand Rail Limited has an existing designation for the Onehunga Branch Railway line to the Port of Onehunga. This rail line is currently not operational.

Designation Number: G12-07.

Description of Designation: Railway Purposes: Onehunga Branch Railway.

Requiring Authority: New Zealand Rail Limited.

MCC Designation

There are no other designations fully or partly overlain by the alteration to designation proposed by the Project.

2.5 Land Requirement: Construction and Operation

The majority of land required for the Project is held for motorway purposes, owned by the Crown and managed by Transit. In addition to the existing designation, more land will be required for permanent works and for construction, operation and maintenance purposes. To provide for this and incorporate all the land required, Transit is altering the existing designation boundaries within the MCC section of the Project and requires a new designation for that section of the Project within the jurisdiction of ACC. Negotiations are currently being undertaken with directly affected landowners to secure the necessary additional land for construction and operation of the Duplicate Bridge, Gloucester Park Interchange (GPI) and the widened sections of motorway.



2.6 Land Ownership

A schedule of affected properties where land is required for the designation is included with the NORs.

In summary, the total number of properties not currently in Crown ownership that are fully or partly required by Transit are as follows:

• Ten commercial properties within the ACC boundary.

• During construction three residential and two properties associated with Te Puea Marae are required within the MCC boundary.

The potential effect on these properties is addressed in Chapter 6 of this AEE.

2.7 Description of the Overall Project Works

The following sections of this chapter describe the general form of the project and construction activities. Further details can be found in Volume 2 Appendix 1 Detailed Description of Physical Works and the various technical reports referred to in this chapter. It is expected that some details will continue to be developed as the project progresses to the design phase. However, the overall works will be as generally described in this chapter.

The Project will widen SH20 between Queenstown Road and Walmsley Road Interchanges from four lanes to six lanes, with bus priority on shoulder lanes where practical. Eight lanes will be provided between the Rimu Road and Gloucester Park interchanges. Mangere Bridge will be duplicated to the east (i.e. a second bridge will be built) to provide four traffic lanes and a shoulder lane for bus priority. Pedestrian and cyclist usage will continue to be provided along the line of the Old Mangere Bridge by way of a replacement structure (Mangere Footbridge).

The existing Gloucester Park split interchange will be upgraded to a grade separated diamond arrangement connected to Neilson Street. The Project will require alterations to local streets (Rimu Road, Mahunga Drive, Neilson Street, Gloucester Park Road and Orpheus Drive) and modification to access arrangements to surrounding properties affected by the upgraded interchange at Gloucester Park Road. The Orpheus Drive modifications require reclamation in the adjacent CMA.

The Rimu Road/Mahunga Drive Bridge will be replaced to allow motorway widening. Further south at Tararata Creek a new off ramp bridge and widened motorway bridge will be required.

At the Queenstown Road Bridge, additional retaining walls and abutments will be required. The Beachcroft Avenue and Hastie Avenue footbridges will also need to be replaced to allow motorway widening.

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The location of the proposed works is shown on Figure 2.3 and is shown in detail in the plans attached in Volume 3 Scheme Plans and Drawings. A detailed description of the proposed works is included in Volume 2 Appendix 1 Detailed Description of Physical Works. The proposed works can be categorised as motorway widening, the duplication of the existing Mangere Bridge, the replacement of the Old Mangere Bridge, the construction of GPI, the replacement of the Rimu Road Bridge, construction of the Tararata Creek off ramp bridge, other associated structures and associated works (e.g. stormwater, landscaping and reclamation).

2.8 Motorway Alignment

The motorway will be widened to provide three lanes in each direction between the Queenstown Road and Walmsley Road interchanges, with bus priority on shoulder lanes where practicable. A fourth lane in each direction (eight lanes in total) will be provided between Gloucester Park and Rimu Road interchanges. The duplication of the existing Mangere Bridge will provide four southbound traffic lanes and a bus priority lane on the shoulder. The existing Mangere Bridge will be reconfigured with the same lane arrangement for north bound traffic. The motorway currently provides two traffic lanes in each direction. Alignment plans are provided on drawings 1/69/82/5104/2-25, Volume 3 Scheme Plans and Drawings.

It is proposed to widen the motorway on the eastern side of the existing alignment as this minimises coastal reclamation and makes efficient use of the existing designation. The widening is generally achieved within the existing designation, except at Gloucester Park and Rimu Road Interchanges.

The vertical alignment of the widened motorway will generally follow that of the existing motorway. Between Walmsley Road and Queenstown Road the shift in the motorway centreline created by widening to the east will require work on the median alignment.



Figure 2.3 Summary of Proposed Works



2.9 Gloucester Park Interchange

It is proposed to construct an upgraded motorway interchange at Gloucester Park as illustrated in Figure 2.4.

Figure 2.4 Schematic layout of proposed diamond interchange at Gloucester Park

The proposed interchange is a standard diamond interchange over the existing motorway alignment at Gloucester Park Road. It provides direct connections to Neilson Street and Onehunga Harbour Road as well as maintaining connection to Orpheus Drive. Drawings of the interchange are attached in Volume 3 Scheme Plans and Drawings 1/69/82/5104/6 and 1/69/89/5104/1-3.

2.10 Pedestrian and Cycling Routes

The Project involves new and improved pedestrian and cycling connections. These are described in more detail in Volume 2 Appendix 8 Urban Design Assessment and are also shown on drawings 1/69/82/5104/76 and 77 in Volume 3 Scheme Plans and Drawings.

In summary, they include:

• Improvement and extension of the foreshore and walkway between the Old Mangere Bridge causeway and Mahunga Drive;

• Replacement of the Old Mangere Bridge with a new Mangere Footbridge for pedestrian and cycle use;

• Provision of pedestrian access along Onehunga Harbour Road;

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• Provision of a new shared cycle/footpath along Onehunga Harbour Road and Orpheus Drive between the Old Mangere bridge and Manukau Cruising Club building;

• Provision for cycling and pedestrian use across the Gloucester Park Interchange bridge to provide a more direct link between Onehunga and the foreshore;

• Replacement of the existing Hastie Avenue and Beachcroft Avenue Footbridges; and

• Provision of cycle lanes and a footpath on the replacement Rimu Road/Mahunga Drive Bridge.

2.11 Earthworks

The extent of overall earthworks for the Project includes approximately 113,000 cubic metres of cut material and 222,000 cubic metres of fill over a total area of approximately 24 hectares. There is insufficient cut material suitable for use as fill to construct the road foundation in areas where embankments are required e.g. Gloucester Park Interchange ramps. As a result of the net deficit of cut material, approximately 188,000 cubic metres of imported fill will be required. Much of this will be required in the formation of ramps at the GPI.

Earthworks for the Project include local road and contractor’s work areas, together with earthworks in the CMA. Works in the CMA are summarised in the following section.

There are areas requiring earthworks where potentially contaminated materials may be encountered. The potential adverse effects associated with disturbance to any existing soil contamination will be managed using procedures, for example removal to controlled landfill, to be documented in the Environmental Management Plan (EMP). Areas where contaminated soils may be encountered include (but are not limited to) Mahunga Drive, the Harbour bed, and inside the tuff ring at Gloucester Park.

2.12 Works Within the CMA

The Project involves coastal reclamation or earthworks within the CMA. Figure 2.5 shows the location of the proposed work in the CMA, drawings 1/69/82/5104/93-99 in Volume 3 Scheme Plans and Drawings illustrate the extent of these works. The total proposed area of reclamation is approximately 2.1 hectares, of which about 0.7 hectares is likely to be temporary reclamation that will be removed after construction.

The following works are proposed within the CMA:

• Duplication of the existing Mangere Bridge. The permanent works include boring of piles, construction of piers and deck superstructure including road surfacing edge protection and stormwater collection system. Temporary works associated with the

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duplication are likely to include construction jetties, temporary reclamation at the north edge of the Harbour and a barge access ramp on the southern foreshore;

• Replacement of the Old Mangere Bridge with a pedestrian/cycle bridge including a fender protection structure. Demolition of the Old Mangere Bridge will be required. Temporary works associated with this are likely to include construction jetties;

• Construction of a new off ramp over Tararata Creek, together with widening and strengthening of the adjacent motorway bridge over Tararata Creek. Temporary works associated with this are likely to include construction jetties / staging. Removal of the edge of the existing motorway bridge over Tararata Creek will be required;

• Coastal Reclamation adjacent to Orpheus Drive. A portion of this is temporary reclamation and will be removed at the completion of the construction phase. The proposed permanent and temporary reclamation is described further in 2.12.1;

• Remediation of the southern foreshore in the area of the existing Mangere Bridge by removal of debris and provision of landscaping;

• Wave protection works to proposed reclamation areas e.g. Rock rip rap along Orpheus Drive;

• Dredging of the Harbour bed may be required e.g. between the breakwater and the Orpheus Drive reclamation;

• Other associated permanent works e.g. stormwater outfall structures and extension of the tidal culvert at Orpheus Drive; and

• Other temporary works e.g. erosion and sediment control.

The following sections describe these further. The Duplicate Bridge and other structures are described in Section 2.14.

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Figure 2.5 Location of Work in CMA

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2.12.1 Reclamation for Gloucester Park Interchange

The proposed embankment ramp for Onehunga Harbour Road and the north facing on ramp at the Gloucester Park Interchange necessitates moving the adjacent section of Orpheus Drive to the south and west. As a result, the existing carparks and boat ramp used by the Manukau Cruising Club will be relocated to the reclaimed area. The Sea Scouts building is currently located over the edge of the CMA. This location will become reclaimed land and will also have the Onehunga Harbour Road ramp immediately adjacent to it. The Sea Scouts building will therefore be relocated approximately 50m northwest, to be located over the edge of the CMA.

Therefore, permanent reclamation is proposed to accommodate the realigned Orpheus Drive, replace affected carparks and the boat ramp, and also to allow the proposed relocation of the Sea Scouts building as follows (The R references are shown on Figure 2.5 on the drawings 1/69/32/5104/93-99 in Volume 3):

• An area of 1.2 hectares adjacent to Orpheus Drive and Onehunga Harbour Road, east from the Manukau Cruising Club for 400 metres with a width from 25 to 40 metres (R1);

• An area of 0.2 hectares adjacent to Orpheus Drive west of the Cruising Club for 150 metres with a width of up to 10 metres (R2); and

• An additional area of 0.2 hectares of temporary reclamation (R3) up to 10 metres in width is also required which is adjacent to the permanent reclamation R1.

The additional area of temporary reclamation is proposed to allow for the continued operation of the north bound on ramp and Orpheus Drive while the new embankment for the north bound on ramp is constructed.

2.12.2 Temporary Reclamation for Contractors’ Work Area at Onehunga Harbour Road

A temporary reclamation will be necessary over a tidal area designated for railway purposes, south of Onehunga Harbour Road and east of the existing reclaimed area beneath Mangere Bridge. The purpose of this reclamation is to provide space for deliveries of bridge construction materials so they can be unloaded clear of Onehunga Harbour Road and for the temporary storage of equipment and materials. The area needs to be large enough to accommodate manoeuvring of large trucks, and storage of large items of equipment or materials (caissons, reinforcing cages, falsework and slipforms, large cranes, etc). An area of up to 0.5 hectares will be required. It is envisaged that this reclamation will be of a temporary nature, and would be removed to a height above mean sea level once it is no longer required for construction purposes. The area required is immediately adjacent to Onehunga Harbour Road to provide access to the temporary jetty. A work area further away would not be suitable.

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2.12.3 Reinstatement Work in the CMA

Reinstatement work in the CMA will include:

• Removal of temporary piles and piles of the Old Mangere Bridge to harbour bed level;

• Provision of wave protection works to exposed areas of permanent reclamation;

• Removal of temporary reclamation areas and reinstatement of the harbour bed. For the temporary reclamation at the north of the Duplicate Bridge, the reclamation will be removed to a height above mean sea level to allow the adjacent saline marsh to extend to this area. This is proposed as mitigation of the temporary adverse effect as outlined in Volume 2 Appendix 14 Coastal Marine Ecology and Water Quality Assessment;

• Foreshore remediation works to areas of previous reclamation e.g. removal of old construction debris and ramps on the southern foreshore adjacent to Mangere Bridge (these are shown on photos in Volume 2 Appendix 3 Bridge and Structures Report; and

• General tidy up of the edge of the CMA where work is undertaken e.g. at Tararata Creek.

2.13 Landscaping

Landscaping works are proposed at various locations along the length of the motorway comprising targeted planting. This includes landscaping at stormwater treatment ponds and at GPI. The objectives of landscaping varies along the length of the Project, using species relevant to the location, including:

• South of Rimu Road the objective is to conceal noise walls from the motorway and improve screening of traffic from neighbouring dwellings, whilst maintaining significant view corridors;

• From Rimu Road to Mangere Bridge views to the Harbour are important, so planting will reflect the need to maintain these views, while using species relevant to the coastal fringe;

• From the northern abutment of Mangere Bridge through Gloucester Park and across the causeway to Beachcroft Avenue footbridge the objective is to protect or enhance views to the coast and harbour, to accentuate the tuff ring, and to screen the appearance of the motorway from Gloucester Park and the Onehunga Bay Reserve; and

• From the causeway to the SH20 Mt Roskill Extension Project the objective is to consolidate the forested Hillsborough gully, and enhance views to the Harbour.

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Further details of proposed landscaping are set out in Volume 2 Appendix 9 Landscape and Visual Assessment and on drawings 1/69/82/5105/2-8 in Volume 3 Scheme Plans and Drawings.

2.14 Structures

This section summarises the proposed bridge and structures works. Further information is provided in Volume 2 Appendix 3 Bridge and Structures Report, and drawings in the series 1/69/86-89, 91-92 and 95 in Volume 3 Scheme Plans and Drawings.

2.14.1 Tararata Creek Bridge

The existing 24 metre long motorway overbridge just north of Walmsley Road Interchange will be widened on the eastern side by up to 7 metres at Tararata Creek. The eastern edge of the existing bridge deck will be removed for the deck extension. This will also require extension of the rock fill and revetment in the CMA together with bored concrete piles. Strengthening of the centre beams of the existing bridge is also proposed. The Walmsley Road off ramp Bridge will be constructed first to allow continued off ramp access.

2.14.2 Walmsley Road Off Ramp Bridge

The widened motorway will require a new off ramp bridge over Tararata Creek. The proposed off ramp bridge measures approximately 7.4 metres in width by 70 metres in length. The superstructure is likely to consist of prestressed concrete beams up to 30 metres in span supported on a bored piled foundation. The proposed off ramp bridge is located partly within the existing motorway designation, and partly within the CMA.

2.14.3 Hastie Avenue Footbridge

The existing footbridge will need to be replaced to allow the motorway widening and the centreline to be moved to the east. The new footbridge is likely to be 2.9 metres wide by 44 metres long. Access ramps are likely to extend on either side of the motorway and zigzag down to Hastie Avenue at either end. The new footbridge will be integrated with the proposed landscaping works. Public pedestrian access over the motorway will be maintained during construction with a temporary footbridge.

2.14.4 Rimu Road Bridge

It is proposed to replace the existing bridge at Rimu Road/Mahunga Drive in order to accommodate the widening of the motorway. The replacement bridge will be approximately 17.5 metres wide by 42.5 metres long. The superstructure is likely to consist of prestressed beams with two 20 metre spans, supported on bored piled foundations.

It may be necessary to install a temporary bridge during construction to maintain traffic flows while the bridge is replaced on its current alignment. The existing structure will be



demolished in stages. The proposed works do not alter the north facing on ramp and the existing ramp metering operation.

2.14.5 Duplicate Bridge

The proposed Duplicate Bridge across the Manukau Harbour will be located to the east of the existing Mangere Bridge with an approximate 3.5 metre separation. It will have a vertical profile similar to the existing bridge to ensure aesthetic compatibility. The Duplicate Bridge is likely to be 22 metres in width, with an overall length of 650 metres between abutments. The substructure for this bridge will consist of piers supported on bored piled foundations. This is discussed in more detail in Volume 2 Appendix 3 Bridge and Structures Report.

2.14.6 Replacement of the Old Mangere Bridge

The Old Mangere Bridge, which is at the end of its service life, will be replaced with a 5 metre wide and 250 metre long combined pedestrian and cycle bridge. It will have a slightly higher vertical level at the northern end to allow greater navigational clearance for low height recreational boats. The superstructure is likely to consist of prestressed beams up to 30 metres in length supported on a bored piled substructure. A fender structure to the west is also proposed which will either be separate or integrated with the new Mangere Footbridge. This will be determined at the design stage.

2.14.7 Gloucester Park Bridge

The new bridge at Gloucester Park Interchange will be approximately 32.4 metres wide and 39 metres long on a skew. The superstructure is likely to consist of prestressed concrete beams with two 19.5 metre spans, supported on bored piled foundations. A retaining wall will extend in front of the abutment piles to match surrounding ramp walls.

2.14.8 Beachcroft Avenue Footbridge

The existing footbridge will need to be replaced to allow the motorway widening and the centreline to be moved to the east. The new footbridge will be approximately 2.9 metres wide by 79 metres long. Ramps will provide access from Seacliffe Road and Beachcroft Avenue. The new footbridge will be integrated with the proposed landscaping works. Public pedestrian access over the motorway will be maintained during construction with a temporary footbridge.

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2.15 Other Construction Features

2.15.1 Retaining Walls

Retaining walls are proposed in the following locations:

• Walmsley Road off ramp;

• Gloucester Park Interchange ramps; and

• Queenstown Road Bridge abutment wall extension.

2.15.2 Fences and Acoustic Walls

Fences and acoustic walls are proposed in the following locations:

• Noise walls varying in height from 1.8m to 2.8m along the west boundary of the motorway reserve between Coronation Road on ramp and Rimu Road;

• A 3m high noise wall adjacent to Te Puea Marae;

• Noise walls at the Walmsley Road off ramps;

• Concrete barriers 0.8 metres high on both sides of the Duplicate Bridge. These will be TL5 barriers which have an overall height of 1.27 metres including the steel top rail;

• A 0.8 metre concrete barrier on the west side of the motorway, extending about 150 metres north from the northern abutment of Mangere Bridge;

• 2.5 metre high noise walls on the east side of the motorway, extending between the Queenstown Road on ramp and the Neilson Street off ramp; and

• A 1.8 metre noise wall along part of the Queenstown Road Northbound off ramp.

The Project may also require wire mesh fencing for the motorway boundary where the works will replace existing fences, such as alongside Waterfront Reserve, Gloucester Park, Onehunga Bay Reserve, and extending up past Queenstown Road to the Mt Roskill project. This is a standard requirement to ensure traffic and pedestrian safety.

2.15.3 Stormwater Management

Permanent stormwater treatment will be provided for the new pavement surfaces (except adjacent to the Rimu Road/Mahunga Drive Interchange where off set mitigation is proposed) as well as retrofitting treatment for some existing surfaces.

The relatively low level and flat terrain necessitates the adoption of swales between the Rimu Road and Walmsley Road interchanges and a series of sand filters along the length of the causeway. Stormwater Management is addressed in Volume 2 Appendix 16



Stormwater Management Assessment and drawings 1/69/82/5105/701-708 in Volume 3 Scheme Plans and Drawings.

Four permanent stormwater treatment ponds are proposed at the following locations:

• In the triangle of land bounded by the motorway, the Coronation Road off ramp and Tararata Creek (Pond 1, Tararata South);

• In the triangle of land bounded by the motorway, the Coronation Road on ramp and Tararata Creek (Pond 2, Tararata North);

• In the existing reclaimed land near the southern abutment of Mangere Bridge (Pond 4, Waterfront); and

• In the reserve bounded by Onehunga Harbour Road and the motorway (Pond 5, Gloucester Park).

In addition, there is an existing stormwater treatment pond in the area below Queenstown Road, between Beachcroft Avenue and the motorway (Pond 6, Beachcroft). This pond may receive some additional runoff from the motorway above it.

All proposed ponds are permanent, treating runoff from the motorway carriageways. They are intended to be landscaped with native wetland species around the periphery. The Gloucester Park Pond (Pond 5) will feature intertidal saline tolerant species as this pond will be inundated with sea water from time to time. It will also feature low growing species to be consistent with the intention to enhance the shape of the tuff ring.

A fifth stormwater treatment pond is preferred north of Mahunga Drive and east of the Rimu Road/Mahunga Drive off ramp (Pond 3, Mahunga). However, this is not currently consentable in this area. A range of other options were considered but were not considered practical given the surface levels, ground conditions and proximity to the CMA. Therefore, off set mitigation is proposed by means of treatment of additional existing surfaces. This is outlined further in Volume 2 Appendix 16 Stormwater Management Assessment.

2.15.4 Lighting

Existing lighting on the motorway is likely to be replaced with central median lighting on 12-15 metre high steel poles. This may continue across the Harbour, using similar columns with double outreach arms, mounted on the Duplicate Bridge. Median lighting columns are likely to be spaced about 40 metres apart.

Motorway ramps are likely to use similar height columns (12-15 metres) with single outreach arms. The new motorway interchange at Gloucester Park may use taller (approximately 20 metre) columns with downlights to reduce the total number of columns and light the area more efficiently.

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The Mangere Footbridge is likely to have up to 12 metre high lighting columns mounted on one side only. This will be confirmed during the design phase.

Local road lighting will comply with the relevant council’s engineering standards for lighting.

2.15.5 Traffic Controls and Signage

The widening of SH20 will mean that some roadside signs will be relocated and/or upgraded to the current Transit standards for motorways. The State Highway routes will be marked out and signposted in accordance with Transit’s standards. Similarly local authority roads will be signed and marked in accordance with the relevant local authority standards.

Traffic control equipment including signage along the motorway alignment is likely to be mounted on a series of overhead gantries, bridges and posts on the side of the carriageway. Overhead gantries which cross the full carriageway are likely to be associated with lane exits and lane drops, and also between each interchange. Gantries are likely to be approximately 7 to 9 metres in height and 2 metres in width. The design phase will define the final layout and extent of this signage.

2.15.6 Utility Services

The existing motorway designation is generally free of services orientated along the alignment, although services are located on the existing Mangere Bridge (Telecom and high tension power). Drawings 1/69/82/5104/65-72 in Volume 3 detail existing services in the Project area.

A major sewer pipe and gas line is located at GPI which will require relocation during interchange construction. A series of high voltage power lines cross the northern section of the motorway diagonally. One of the tower masts supporting these at Gloucester Park will require relocation for ramp construction. Another mast adjacent to Orpheus Drive is close to the coastal reclamation, but is unlikely to need to be relocated. This will be determined during the design phase. A major gas line which extends along Orpheus Drive is expected to be avoided. The gas line also crosses the motorway alignment at Gloucester Park and will need to be relocated around Onehunga Harbour Road.



2.15.7 Local Road Alterations

The motorway widening and interchange construction will require alteration to existing local roads including:

• Onehunga Harbour Road rising to the new interchange over the motorway;

• Orpheus Drive is to shift laterally to accommodate the new interchange;

• Widening of Neilson Street is required west of Selwyn Street;

• Gloucester Park Road’s access to Neilson Street is to be closed, forming a cul-de-sac north of Neilson Street;

• A new access cul-de-sac off Selwyn Street is to be created south of Neilson Street; and

• Vertical realignment of Rimu Road and Mahunga Drive is required to raise the new bridge higher over the motorway to achieve greater clearance.

New access arrangements for properties where the permanent works sever existing access arrangements are required. A new access road from Selwyn Street will provide access for those properties bounded by Selwyn Street/Neilson Street/Lower Gloucester Park Road and is shown on the plan 1/69/82/5104/6 contained in Volume 3 Scheme Plans and Drawings. This access road will be a two lane road with a turning head at the end to allow legal dimension vehicles to turn. Demolition of some existing buildings will be required to provide this. Properties not directly adjoining the access road will be connected to the turning head by a formed right-of-way. Details of these arrangements will be developed during the design phase in consultation with affected property owners and ACC. The new access road will become an ACC road on completion of the Project. The status of the right of way will be determined following discussions with affected property owners and ACC.

The Local Lockup site is currently accessed from lower Gloucester Park Road. It is required for construction activities, temporary on ramps and the contractor’s work area. As a result it will not be possible to maintain the existing operations of the Local Lockup during construction. Once the interchange is completed, access to the residual land could be provided from either Hill Street or Wharangi Street via the current off ramp, which will be decommissioned from motorway use.



2.16 Outline of Construction Methodology

The following summarises the construction activities required and their likely sequence. A detailed description is included in Volume 2 Appendix 1 Detailed Description of Physical Works. It should be noted that the methodology is indicative at this stage and gives a general overview of the likely scope of work. The details of the construction methodology will be developed by the construction contractor and submitted as part of the Construction Management Plan (CMP), Erosion and Sediment Control Plans (E&SCP) and other detailed management plans.

2.16.1 Site Clearance and Contractor Work Areas

The various construction sites will be cleared on commencement of physical works (or prior through advanced enabling works).

The main contractor establishment work areas are expected to be located as follows:

• Waterfront Road reserve for bridge construction activities;

• Between Gloucester Park Road, the motorway, and the existing southbound off ramp (currently used by the Local Lockup business) for Gloucester Park Interchange construction activities; and

• Between SH20 and Beachcroft Avenue from Queenstown Road to the Onehunga Bay Reserve for on motorway construction activities.

Smaller secondary contractor establishment work areas are expected to be located as follows:

• Temporary reclamation at north end of Duplicate Bridge adjacent to Onehunga Harbour Road;

• Adjacent to the Walmsley Road southbound off ramp;

• Adjacent to the Coronation Road northbound on/off ramps;

• South of Mahunga Drive adjacent to the motorway bridge;

• On Old Mangere Bridge approaches and causeway; and

• North end of Gloucester Park east adjacent to the existing southbound on ramp.

The project drawings, 1/69/82/5104/93-99, included in Volume 3 Scheme Plans and Drawings show these work areas.

Site clearance and contractor establishment will generally require ground preparation, establishment of Erosion and Sediment Control measures, and provision of contractor’s facilities.

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The contractor’s site offices will need to accommodate staff, labourers, sub contractors and facilities and parking for the site labour force. Offices and sheds will be located as far from residential properties within the designated site area as is practicable e.g. at Waterfront Road. The majority of the site will be fenced. The fencing is likely to be with hurricane wire netting or up to 2.4 metre tall plywood panels.

The establishment work and site clearance will also require the removal of various buildings adjacent to Gloucester Park Road, Lower Neilson Street and Selwyn Street. Discussions are ongoing with the property owners. These sites are described in the Schedule of Properties (ACC) attached to the NOR. Buildings located on these sites are generally single or two storey.

2.16.2 Construction Access

Construction access is required for large trucks, large cranes, deliveries and construction staff. The proposed designation includes provision for contractor establishment and working areas. Contractor establishment and works areas are listed above in section 2.16.1.

Access to these work areas is required from the existing motorway and from local roads including Gloucester Park Road/Neilson Street, Onehunga Mall/Onehunga Harbour Road, Orpheus Drive, Beachcroft Avenue, Waterfront Road, Rimu Road/Mahunga Drive, Walmsley Road and Kingfisher Place. It is anticipated that the majority of access to the motorway for carriageway widening will be from the motorway itself under temporary traffic management procedures.

All access requirements and truck movements will be considered in conjunction with the Auckland and Manukau City Councils through the preparation of a Construction Management Plan and a Construction Traffic Management Plan. Further information on construction access effects is contained in Volume 2 Appendix 10 Traffic Issues Assessment.

2.16.3 Enabling Works and Access Arrangements

Advanced enabling works may be undertaken dependent on the construction programme adopted following design phase. These could include:

• Construction of an access road from Selwyn Street to properties affected by the Gloucester Park Road/Neilson Street ramps. As noted above, this will involve demolition of some existing buildings. Details of arrangements will be confirmed during the design phase of the Project;

• Reclamation along Orpheus Drive. The reclamation is required early in the physical works programme to enable Orpheus Drive to be relocated westwards to allow construction of ramps and the relocation of the Sea Scouts building; and



• Services and pylon relocation. The existing Transpower pylon adjacent to lower Gloucester Park Road will need to be relocated to allow the lower Gloucester Park ramp to be built. The relocated pylon will either be further within the existing site or to the west of the motorway. A gas line and a sewer pipe on the east of Gloucester Park will require relocation (see 2.15.6). These works will be confirmed during the design phase of the Project.

2.16.4 Motorway Widening Construction

The majority of motorway widening works are expected to be undertaken on the eastern side of the existing motorway. This means that the majority of the works are able to be constructed off line, with barriers to separate work areas from the motorway or local roads. Some elements cannot be constructed off line because of their proximity to traffic lanes, including bridges over the motorway, and works to adjust the existing motorway shape. Such works will require temporary traffic control by either shoulder closures, traffic lane closures or shifts, or, in the case of lifting new beams over the highway, full motorway closures. This would be carried out in accordance with Transit’s temporary traffic management standards (COPTTM) and with public notification, to minimise traffic disruption.

2.16.5 Construction of the Duplicate Bridge

2.16.5.1 Construction Work Areas

The main site establishment facility for the bridge construction is proposed at the Waterfront Road site adjacent to the existing Mangere Bridge. This work will be within the reserve area and not physically on the road or the adjacent residential properties. These residential properties will continue to have access along Waterfront Road. Some temporary construction areas for site offices, car parking, facilities, materials delivery, storage and assembly will be required adjacent to the Duplicate Bridge site. It is proposed that the area of foreshore at the south end of the Mangere Bridge will be used together with a temporary reclamation area at the north of the proposed Duplicate Bridge alignment adjacent to Onehunga Harbour Road.

2.16.5.2 Temporary Works

The Duplicate Bridge requires the construction of piers within the CMA. It is expected that boring of the permanent foundation piles, construction of the reinforced concrete pile caps and construction of the reinforced concrete pier columns will be carried out from temporary staging. This temporary staging at each pier position will be provided by temporary jetties from the foreshore at each end of the Duplicate Bridge site. As for the staging, these temporary jetties will be supported on temporary piles driven from barges.

On completion of construction all temporary works, including the piles and temporary reclamation will be removed and the site reinstated.

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Construction of the south abutment and the alteration of the northern abutment and adjacent piers will be carried out on land.

2.16.6 Construction of Gloucester Park Interchange

Depending on the details developed in the design phase, it is proposed that the construction of GPI and associated ramps and bridges be undertaken in stages as illustrated on drawings 1/69/82/5104/83-87 in Volume 3 Scheme Plans and Drawings. These may be as follows:

• Foreshore reclamation and relocation of Orpheus Drive to a temporary alignment on the reclamation;

• Provision of a temporary north bound on ramp;

• Access road arrangements constructed from Selwyn Street;

• Existing Gloucester Park southbound on ramp relocated adjacent to existing off ramp and then around the Local Lockup site to merge with SH20;

• Gloucester Park Road ramp and new northbound on ramp constructed;

• Southbound on and off ramps constructed as Gloucester Park Bridge construction proceeds;

• Temporary Gloucester Park southbound on ramp relocated to permanent ramp, and southbound off ramp constructed;

• Northbound on ramp constructed;

• Orpheus Drive relocated to the final alignment; and

• Onehunga Harbour Road ramp completed.

2.16.7 Construction of Mangere Footbridge

The new Mangere Footbridge is approximately 5 metres wide and is narrower than the Old Mangere Bridge. Depending on the details developed in the design phase, it is anticipated that the eastern side of the Old Mangere Bridge will be progressively demolished to allow construction of the Mangere Footbridge. The remaining portion would then be demolished and fender pile arrangements installed. Closure of the Old Mangere Bridge for health and safety reasons is likely to be required during construction. This will affect pedestrian, cycling and recreational fishing access. Existing alternative access will continue to be provided via the walkway on Mangere Bridge. Security considerations associated with this will be reviewed during the design phase. The period between works commencing on the Old Mangere Bridge and opening of the new Mangere Footbridge will take approximately one year.

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2.16.8 Construction of the Replacement Rimu Road Bridge

The replacement bridge is likely to be located on the alignment of the existing bridge. A temporary bridge may be required to be constructed on the northern side of the existing bridge to carry traffic while the existing structure is demolished and replaced. This is in order to provide continued access from Rimu Road.

2.16.8.1 Construction of Tararata Creek Structures

The new off ramp bridge will need to be constructed first. The existing off ramp traffic will then be redirected, allowing shoulder and partial lane closure to enable widening of the existing motorway bridge over Tararata Creek. The staging of this construction is shown on drawings 1/69/82/5104/88-92 in Volume 3 Scheme Plans and Drawings.

2.16.9 Construction of Footbridges

Both Beachcroft Avenue and Hastie Avenue footbridges are proposed to be built immediately adjacent to the existing bridges to minimise closure of the existing structures. This will require temporary staging to protect motorway operations during construction and temporary (overnight) motorway closures to hoist beams over traffic lanes.

2.16.10 Construction of Stormwater Treatment Devices

The construction sequencing for stormwater devices will generally be integrated with the motorway widening elements.

2.16.11 Erosion and Sediment Control Measures

The proposed Erosion and Sediment Control measures for the project works comprise of several specific measures including the following:

• Cleanwater Runoff Diversion Bunds;

• Stormwater Inlet Protection;

• Silt Fencing;

• Stabilised Construction Entrances;

• Sediment Retention Ponds;

• Progressive Stabilisation;

• Dam and Divert methodology for culvert, and fish passage works;

• Floating Silt Fence/Booms (turbidity curtain); and

• Other Methods (e.g. flocculation/coagulation, and mudcrete stabilisation etc).



These are described in more detail in the Volume 2 Appendix 18 Erosion and Sediment Control Plan and drawings 1/89/82/5105/721-728 in Volume 3 Scheme Plans and Drawings. These measures will be established in advance of bulk earthworks.

2.16.12 Indicative Construction Programme

The following indicative construction durations are anticipated:

• Enabling works – 6 months;

• Mangere Bridge duplication – 24 to 36 months;

• Gloucester Park Interchange – 24 months; and

• On motorway works – staged over 36 months.

Overall, it is anticipated that the Project will take between 36 and 48 months to complete.

Construction Management Framework

2.16.13 Introduction

The physical works will be governed by a Construction Management Framework to assist the contractor (and Transit) to manage the Project in such a way as to meet or exceed Transit and stakeholder expectations.

Essentially, the framework sets out the requirements for operational management plans that the contractor will prepare and implement. These operational management plans will set out Transit and other stakeholders’ requirements to carrying out the physical works. They will include performance indicators for gauging compliance to ensure the best technical and environmental outcomes. These operational management plans are outlined in the following sections. The framework will be subject to ongoing review and improvement between Transit and the contractor.

The operational plans will include:

• Construction Management Plan;

• Stakeholder Management Plan;

• Safety Management Plan;

• Environmental Management Plan; and

• Traffic Management Plan.

These plans are discussed in more detail below. The plans may be separate or elements may be integrated into a single document.



2.16.14 Construction Management Plan

The Construction Management Plan (CMP) will detail the management processes that will be put in place to plan, execute and control the Project during the construction phase. The CMP will focus on the tasks and controls required for each construction activity, covering off the contributions from the various project management disciplines and may include:

• Work plans for each construction activity;

• Construction risk management;

• Health and safety plans;

• Quality control;

• Testing and inspection plans;

• Survey; and

• Programme.

2.17.3 Safety Management Plan

A Safety Management Plan will be required which identifies the statutory requirements with regard to safety and sets out the contractor’s proposals for planning, implementing, measuring and evaluating of the Health and Safety System.

It is likely that some works will need to take place during night time hours throughout the course of the Project for safety reasons, in order to meet completion deadlines or to avoid disruption to traffic on both the motorway and local road networks.

2.17.4 Stakeholder Management Plan

A Stakeholder Management Plan (SMP) will be developed to assist the Project team to identify and manage stakeholder issues and expectations throughout the Project. The SMP will set out the Project objectives with respect to stakeholders, identify the potential issues and include guidelines on strategies, systems and procedures that will be put in place to manage stakeholder relations, communications and issues.

2.17.5 Environmental Management Plan

An Environmental Management Plan (EMP) will be prepared that will set out the conditions of resource consents and designations is to be complied with. It will include the methodology for managing key environmental issues, including erosion and sediment control, dust management, vibration management, construction noise management and soil contamination management.



The construction noise section will identify the noise standards to be achieved, the particular activities that may require noise mitigation and details of that mitigation where provided.

A draft EMP has been prepared and is included in Volume 2 Appendix 19 Draft Environmental Management Plan.

2.17.6 Traffic Management Plan

A Traffic Management Plan (TMP) will be prepared that will set out the resources and procedures to be used to provide a safe working site and maintain safe passage of traffic and pedestrians through the site. The TMP will be used to design site specific TMPs for construction activities where traffic management is required. These will detail the proposed traffic management for each construction activity, relative to the existing operational traffic environment. The preparation of the TMPs will draw on Transit’s Code of Practice for Temporary Traffic Management.

SH 20 Manukau Harbour Crossing Project – Assessment of Environmental Effects Chapter 3 – Consideration of Alternatives


3 Consideration of Alternatives

3.1 Introduction

The SH20 Manukau Harbour Crossing Project (the Project) is the culmination of a series of investigations carried out over a period of more than 10 years.

Under section 171(1)(b) of the RMA, when considering a NOR, the consenting authority is required to have particular regard to whether adequate consideration has been given to alternative sites, routes and methods of undertaking the public work. This requirement in respect to consideration of alternatives applies to notices under Sections 168 and 181 (1) and (2) of the RMA. The requirement under Section 105(1) to consider alternatives for discharges is covered in Volume 2 Appendix 16 Stormwater Management Assessment.

In this chapter of the AEE, an overview is provided of the extensive investigations into:

• Alternative route options for increasing transportation capacity across the Manukau Harbour; and

• Alternative options for an improved connection between the South Western Corridor and the Onehunga-Pakuranga Corridor at Neilson Street.

The overall process that has been followed to determine alternatives is as follows:

Figure 3.1 Overall Process Diagram for Alternatives

Route Alternatives “how to increase capacity across the Manukau Harbour”

↓ Interchange Location Alternatives

“where to put an interchange to connect the SH20 Corridor with the Onehunga – Pakuranga Corridor at Neilson Street”

↓

Interchange Alternatives “how to configure the interchange”

↓

Design Alternatives “consider alternatives for design components” Refer respective technical reports in Volume 2



The Project area forms part of the SWTC. Figure 3.2 identifies the SWTC (labelled as South Western Motorway) as part of the Western Ring Route.

Figure 3.2 Western Ring Route

3.2 Consideration of Alternative Land Transport Options for SWTC

Consistent with Transit’s obligations under the LTMA, a Strategy Study of the SWTC, which includes SH20, was undertaken by Opus in 2005. This study was undertaken for Transit in conjunction with several other key stakeholders including the ARC, ARTA, ACC, MCC and Waitakere City Council (WCC). The study was a broad transportation study which considered the needs of all transport modes in the SWTC.

This study considered both the present land use and future changes with the aim of identifying and providing an effective transport network within the Corridor. The study was also undertaken as a condition of funding for the SH20 Mt Roskill Extension Project to determine the strategy for a future extension of SH20 to SH16. This included the development of an integrated package of proposals for the Corridor to ensure that the transportation benefits of the projects within the Corridor are consistent with the overall strategy for the Corridor.



The Strategy Study identified a range of component projects in the following categories:

• Passenger Transport;

• Rapid Transit;

• Local Roads;

• State Highways;

• Walking and Cycling Facilities; and

• Travel Demand Management.

A range of packages were agreed, each consisting of a combination of the component projects selected to achieve an overall strategic outcome. The evaluation criteria for these package options were based on the five principles of the New Zealand Transport Strategy. These were combined with criteria regarding the extent to which each package supported the Regional Growth Strategy and was able to provide economic efficiency.

The following component project specific conclusions were made in respect to the Manukau Harbour Crossing study area:

• The SH20 proposals will serve the growth centres of Mangere Bridge and Onehunga by improving accessibility around the centres and reducing traffic through the centres.

• The existing Manukau Harbour Crossing is a key constraint affecting the accessibility of the Auckland Airport. The route is heavily congested and this is expected to worsen following the completion of the SH20 Mount Roskill Extension and SH20 Manukau Extension Projects. While some form of additional transport capacity will be required, the modelling indicates that rapid transit will not sufficiently reduce the demand to avoid the need for additional traffic capacity.

• The SWTC Strategy Study 2005 recommended that Transit New Zealand should resume investigations into the SH20 Manukau Harbour Crossing Project on the basis of the proposed motorway bridge duplication forthwith. As part of this investigation, it was established that:

− The proposals should provide bus priority where appropriate, both along the route and at key interchanges;

− The proposals should include provision for pedestrian/cycle links across the harbour;

− The proposals should not preclude possible future rapid transit links;



− The proposals should not preclude a possible future local crossing; and

• The study should include further investigations into the form of GPI.

3.3 SH20 Manukau Harbour Crossing Project Scheme Development

The Project is described in Chapter 2 of this AEE. The location and study areas are shown on Figures 3.3 and 3.4 below.

The do minimum scenario for traffic modelling that was considered to compare the Project against consists of the existing transport network and a number of transportation projects. These projects are listed in Volume 2 Appendix 10 Traffic Issues Assessment. The following SH20 projects are in the do minimum scenario:

(Appendix A) w are assumed to have been completed, including:

• SH20 Mt Roskill Extension Project – extending SH20 to Richardson Road; and

• SH20 Manukau Extension Project – connecting SH1 and SH20 at Manukau City Centre.

Full details of the improvements assumed in the do minimum, in terms of roading, passenger transport and travel demand management projects, are set out in Volume 2 Appendix 10 Traffic Issues Assessment.



Figure 3.3 Location Plan



Figure 3.4 Project Study Area

Figure 3.5 below is a detailed process diagram which illustrates the sequence of investigations that resulted in the preferred scheme.



Figure 3.5: Detailed Process Diagram



The following sub-sections summarise the investigations that resulted in the preferred scheme.

3.3.1 Previous Investigations (1995 – 2002)

In 1995, ACC investigated options for providing an interchange at Gloucester Park. The aim of this initial study was to provide improved connectivity between SH20 and Neilson Street and relieve some of the congestion in the Onehunga area. Of particular focus was the congestion occurring on Onehunga Harbour Road.

This investigation provided base information for a subsequent Strategy Study undertaken on behalf of Transit to assess the interchange options at Gloucester Park. Opus was commissioned for the SH20 Walmsley Road to Queenstown Road Study. This was undertaken in two parts, an Options Study and a subsequent Strategy Study.

The SH20 Walmsley Road to Queenstown Road Options Report (ref: CER 01/01) was finalised in November 2001 and provided a comprehensive overview assessment of the issues and options for providing additional capacity across the Manukau Harbour. It identified the following route options:

• Route Option 1: Widen existing Mangere Bridge.

• Route Option 2: Widen motorway and provide duplicate existing Mangere Bridge.

• Route Option 3: Widen motorway (Queenstown to Neilson). Provide western Harbour crossing.

• Route Option 4: Widen motorway (Queenstown to Neilson). Provide eastern Harbour crossing.

This Options Report (2001) concluded that Option 2 was the most appropriate option, with high benefits for motorway users, relatively low impact on the local community and low environmental impacts.

The SH20 Walmsley Road to Queenstown Road Strategy Study Report was finalised in August 2002. The study considered all the options previously investigated in the Options Report, along with an additional Option (5) which consisted of an alternative eastern crossing from Rimu Road to Neilson Street (east of Onehunga Mall). Option 5 was put forward following consultation with the Maungakiekie Community Board (Community Board).

This fifth Option submitted by the Community Board was first considered in a separate report dated July 2002. It is understood that the main concerns of the Community Board related to traffic congestion in lower Onehunga and the impact of a grade separated interchange at Gloucester Park. Their proposal was intended to reduce congestion in



Onehunga by diverting traffic from Neilson Street across an eastern crossing to avoid a grade separated interchange at Gloucester Park.

Figure 3.6 below shows the indicative alignments of all options considered.

Figure: 3.6 Route Options

The 2002 analysis of Option 5 showed that it was less favoured relative to Option 2. The reasons for this were:

• Option 5 would be more expensive to construct and would not generate additional traffic benefits;

• Option 5 would have greater environmental impacts including larger reclamations over mudflats, increased visual impacts and impacts upon the Te Puea Marae; and

• Option 5 would still require additional Harbour Crossing capacity on the SH20 motorway route, but makes motorway widening more difficult in the future.

The Strategy Study (2002) which focused mainly on the issues of capacity, traffic analysis, planning/environmental and economic analysis, confirmed the earlier recommendations made in the Options Report.

It was recommended that the following strategy be adopted:



• Widen the motorway to three lanes in each direction between Queenstown Road and Neilson Street interchanges;

• Provide three lanes and one auxiliary lane in each direction across the Harbour through a duplicate bridge east of the existing bridge;

• Widen the southbound carriageway to three lanes from Hillsborough Road to Queenstown Road;

• Widen the motorway south of Rimu Road to three lanes in each direction at a later date (predicted to be in 2011);

• Increase capacity across the Manukau Harbour in the form of a local crossing at a later date; and

• Remove the Old Mangere Bridge and construct a replacement structure as a pedestrian/cycle link.

3.3.2 Recent Investigations (2003 – 2006)

Transit commissioned Opus in 2003 to undertake further scheme assessment investigations for the Project. This study drew upon the previous investigations to confirm a preferred route option, to improve transportation capacity across the Manukau Harbour and identify an interchange option to improve capacity between SH20 and the Onehunga – Pakuranga Corridor at Neilson Street.

As a result of the introduction of the LTMA, the Project investigations were suspended to allow for the consideration of the SWTC Strategy Study which addressed the wider transport implications within the corridor. At this point, the Stage 1 round of public consultation on the Project options had been completed.

As outlined above, the SWTC Strategy Study confirmed the location of the preferred linkages for the Project. Once the need for additional capacity in the Project area was confirmed, the scheme investigation recommenced (September 2005). Stage 2 public and stakeholder consultation was undertaken during October and November 2005. At this time, all previous options considered were re-assessed under the LTMA.



3.4 Consideration of Route Options

The following alternative route options were considered for evaluation:

Route Option Description

Option 2 Widen motorway and provide duplicate Mangere Bridge

Option 3 Widen motorway (Queenstown to Walmsley)

Provide local western Harbour crossing


Provide local eastern Harbour crossing


Alternative eastern crossing proposal put forward by the Maungakiekie Community Board including a link from the motorway at Rimu Road to Neilson Street, east of Onehunga Mall

Option 1 involved widening the existing Mangere Bridge. Widening of the existing four lane bridge would need to be of sufficient capacity to carry an additional four traffic lanes, effectively doubling the width of the bridge. An analysis has shown that the existing box girders do not have the capacity for the additional loads that would be imposed. Therefore, Option 1, the widening of the existing Mangere Bridge, was not considered feasible. This fatal flaw resulted in it not being considered further.

During scheme investigations, it was identified that, irrespective of which route crossing was chosen, widening of the motorway from Queenstown to Gloucester Park Road and Rimu Road to Walmsley Road Interchanges would be required due to the expected increase in traffic volumes. This widened motorway would need to be 3 lanes in each direction (up from the current 2) with the Harbour crossing expanded to 4 lanes each way and the provision of bus priority shoulder lanes where practical.



3.4.1 LTMA Evaluation Process

This section describes the LTMA assessment of the route and interchange options which comprised two stages.

3.4.1.1 Stage 1 – Fatal Flaw Analysis

Stage 1 involved a coarse review of each option assessed against the Project objectives, RMA requirements and LTMA requirements to determine any fatal flaws. Finally, an engineering review was completed to check feasibility of design and constructability. An option was removed from further consideration if it presented an obvious failure in any of the above criteria. It is noted that the Route Option One, comprising additional lanes on the existing motorway crossing, was found to be technically unfeasible and was discounted through this fatal flaw analysis.

3.4.1.2 Stage 2 – In Depth Review

Stage 2 comprised an in-depth review of the remaining options against a set of project defined criteria and LTMA objectives. This comprised of the following steps:

• A ratings matrix was developed, contrasting options against these evaluation criteria;

• Members of the Project team separately undertook specialist assessments of each option relevant to their area of expertise. The options were then compared during workshops and rated using the evaluation matrix and ratings below. The “do minimum” option was used as the benchmark for the evaluation;

• An evaluation workshop was held to formally assess and rate each option. Each team member presented their particular rating aspects and then the wider team debated the merits of each option before assigning a rating for each criteria;

• A summary table was prepared to derive an overall rating for each option and preferred options were identified; and

• Evaluation workshops were held in November and December 2005. The following section summarises the key issues and features from that consideration.



Figure 3.7 Stage 2 LTMA Assessment Process

MANUKAU HARBOUR CROSSING STAGE 2 LTMA ASSESSMENT PROCESS

Identification of criteria for assessment objectives based on the SWTC Strategy Study

Specialists briefed (including evaluation rating system) and all key staff undertaking assessment assigned responsibilities for particular criteria or sub-criteria

Evaluations of assessment workshopped with entire evaluation team, including reassessment according to new information

Re-evaluation of ratings based on workshop findings

Champions assess overall rating of criteria (balancing up ratings of sub-criteria)

Confirm overall rating

Workshop the overall ratings and identify the preferred option strategy

Confirm preferred option



3.4.1.3 Evaluation Criteria

The criteria adopted for this study are set out in the table below. They were developed by the project team, using similar evaluations undertaken for projects in the Auckland region including the Eastern Transport Corridor, SH20 Waterview Connection, North Auckland Line, SWTC Strategy Study and Southern Sector Study.

Objective Performance Indicator

(a) Assisting economic development Accessibility to employment opportunities

Accessibility to, between and within key economic and knowledge centres

General accessibility

Reliability

Transport network resilience

Impact on freight

(b) Assisting safety and personal security

Accidents, injuries and deaths

Actual and perceived levels of security

Effect on vulnerable users

(c) Improving access and mobility Connectivity

Availability of travel choices to key destinations

General accessibility

Impact on those without access to a car

Share of trips by public transport

Consideration of people with disabilities

(d) Protecting and promoting public health

Share of trips by active modes – walking and cycling

Emissions to air and water

Noise and vibration

(e) Ensuring environmental sustainability

Emissions to air, water and land

Use of non-renewable resources

Impact on heritage, cultural, visual, landscape and ecological sites

Energy efficiency and greenhouse gas emissions

Community severance



Objective Performance Indicator

(f) Supporting the Growth Strategy Relative accessibility to, within and between key Regional Growth Strategy growth centres

Community coherence

Level of fixed passenger transport as pre-condition for centre growth

(g) Cost effectiveness Affordability Benefit/cost analysis

(h) Project objectives To provide an integrated, safe, responsive and sustainable land transport system on the existing South Western Corridor between SH20A Interchange and SH20: Mt Roskill Extension, that will:

a) provide a high standard, strategic transport connection as part of the regional alternative route to State Highway 1 connecting Manukau and Auckland cities (the Western Ring Route);

b) improve efficiency and safety in this part of the existing South Western Corridor; and

c) improve access between the South Western and Onehunga-Papakura Corridors.



3.4.2 Summary of Route Option Assessment

The following Figures 3.8 to 3.11 illustrate Options 2 to 5 and identify the main features.

Figure 3.8 Option 2 Duplicate Motorway Crossing

The main features of Option 2 are:

• It emphasises the future importance of SH20 as part of the WRR and provides a significant improvement in capacity for the key north-south movements;

• It provides improved connections between SH20 and the Onehunga-Pakuranga Corridor via the motorway improvements and GPI;

• The Harbour crossing has “moderate” adverse environmental effects. It generally restricts the effects to within, or adjacent to, the existing motorway corridor;

• Existing views or environments are not changed significantly by the duplicate bridge;

• It would preserve an eastern alignment for a future rail/rapid transit corridor; and

• Less structure length crossing the Harbour is required compared to eastern options.



Figure 3.9 Option 3 Local Western Crossing


• This is a low cost option with relatively minor environmental effects;

• It would not attract significant volumes of traffic due to the lack of direct connections to the motorway;

• It would not significantly reduce congestion along the motorway;

• It does not sufficiently provide for any of the strategic travel movements, although it provides a local connection between Onehunga and Mangere Bridge township;

• As a result, duplication of the motorway bridge is still required at the time of opening of the “local” crossing;

• It would lead to increases in traffic through Mangere Bridge township;

• Less visual impact as replacement is on same alignment as the Old Mangere Bridge;

• Increased traffic on local roads adjacent to the Mangere Bridge foreshore; and



• Any widening of the existing southern causeway would require a structure because reclamation is prohibited in Coastal Protection Area 1 (CPA1).

Figure 3.10 Option 4 Local Eastern Crossing


• The southern half of the crossing is in CPA1. A number of activities required under Option 4 are prohibited in CPA1;

• This has a higher cost due to the significant length of structure across the harbour;

• It would not attract significant volumes of traffic due to the lack of direct connections to the motorway;

• It would not significantly reduce congestion along the motorway;

• It does not sufficiently provide for any of the strategic travel movements, although it provides a local vehicular connection between Onehunga and Mangere Bridge Township. It would not be on the desire line for pedestrian/cycle use;




• It would lead to increases in traffic along Mahunga Drive in the vicinity of the Te Puea Marae;

• Visual effects would be greater as the new bridge would be on a new alignment i.e. a third corridor; and

• It would have increased impact on the foreshore at Mahunga Drive which is more sensitive ecologically and culturally.

Figure 3.11 Option 5 Eastern Crossing (Community Board Alternative)


• This is the highest cost option due to the significant length of the structure and increased local road length;

• It provides an excellent connection for the movement between SH20 (south of the Harbour) and the Onehunga/Pakuranga Corridor;

• It will allow this traffic to bypass the southern end of Onehunga;



• It offers benefits for the key movement between SH20 (south) and SH20 (north) by removing South to East traffic from the Harbour Crossing, but congestion will still occur on the motorway;


• It does not improve the movement between SH20 (north) and the Onehunga/Pakuranga Corridor. Westbound traffic will still use Onehunga Harbour Road which has a poor alignment;

• It would have potentially significant effects on the Te Puea Marae;

• It would require the removal of the existing north facing ramps at SH20 Rimu Road Interchange in order to facilitate the proposed south facing ramps between the motorway and the new crossing. This would reduce the accessibility of the Mangere Bridge township;

• Loss of the Waterfront Road Reserve land;

• It would have greater impact on the coastal area than the duplicate motorway bridge, particularly to the south of the Harbour;

• The alignment at the southern abutment is restricted by the CPA1 zone where a number of activities are prohibited. The southbound lanes would need to be extended on structures to Mahunga Drive. This complex arrangement of ramps would visually compromise the southern foreshore and increase severance;

• The crossing does not align with the desire line for pedestrian/cycle users; and

• The eastern crossing is likely to constrain future rail/rapid transit crossings on the east.

3.4.3 Selection of Preferred Route Option

An LTMA analysis of options 2 to 5 was carried out. Options 2 and 5 scored higher than the other options. The following were key issues from the analysis:

• Option 1 failed the Stage 1 fatal flaw analysis as the existing bridge cannot be widened sufficiently for the lane capacity required;

• Option 2 provides significant improvement in capacity for the key north south movements while restricting environmental effects generally to the existing corridor. It would also not constrain future rail/rapid transit crossings on the east;



• Options 3 and 4 provide increased Harbour crossing capacity. However, this is insufficient to cater for the remainder of the predicted growth in demand on the SH20 route;

• Option 5, while providing a direct link between Neilson Street and SH20 to the south, does not provide a similar improved direct link to the northwest. As with options 3 and 4, the relief in demand provided by this option does not cater for the predicted demand on the main SH20 route crossing. Option 5 would require the severance of the existing north facing ramps at Rimu Road / Mahunga Drive, thereby reducing accessibility from and to the Mangere Bridge Community. It would also constrain future rail/rapid transit crossings on the east. Option 5 would also be difficult to obtain resource consent for due to the encroachment on CPA1; and

• None of the route options obviate the need for the Gloucester Park Interchange.

Further traffic modelling was undertaken to compare options 2 and 5. This is outlined in Volume 2 Appendix 10 Traffic Issues Assessments. It concluded that Option 2 will provide greater overall traffic benefits and better meet the Project objectives than Option 5.

The evaluation team reached the overall conclusion that Option 2 most consistently satisfied the evaluation criteria and best met the Project objectives. Therefore, it was identified as the preferred route option. This is the option now proposed and described in the Notice of Requirement (NOR) and consent applications.



Figure 3.12 Proposed Route

3.5 Consideration of Interchange Options

An objective of the Project is to improve access between the SWTC (SH20) and Onehunga – Pakuranga Corridor. These corridors are defined as strategic routes on Map 7.2 in the 2005 ARLTS. The Onehunga – Pakuranga Corridor is shown on Figure 3.3 and includes Neilson Street at its Onehunga end. This illustrates that it has a strategic function as a regional arterial connecting SH20 with SH1 and Pakuranga. It is a key east – west connection and provides strategic access between the eastern areas of Auckland and Manukau cities with the Auckland International Airport (including surrounding commercial areas), Waitakere City and western areas of Auckland City. The commercial areas adjacent to Neilson Street also generate traffic requiring access to SH20.

The improved access from the Onehunga – Pakuranga Corridor to SH20 needs to cater for both northbound and southbound trips. The existing SH20 Interchange to Neilson Street at Gloucester Park provides this connectivity but is currently over capacity resulting in significant traffic congestion at existing on and off ramps. It also has a number of deficiencies which are outlined in 3.5.1 following. An upgraded interchange in the Gloucester Park area is therefore required to provide the required traffic capacity and safety improvements and thereby meet the Project objectives.



Volume 2 Appendix 10 Traffic Issues Assessment in discusses further the traffic flow improvements that will result from an upgraded interchange at Gloucester Park.

3.5.1 Existing Interchange

The existing interchange connecting with Neilson Street has a non standard split interchange form. The northbound ramps connect to Neilson Street via Onehunga Mall/Onehunga Harbour Road and under the northern land span of Mangere Bridge. The southbound ramps connect to Neilson Street at the intersection of Neilson Street and Gloucester Park Road.

There are a range of deficiencies with the existing interchange which include:

General Functionality

• The non-standard arrangement can cause driver confusion which is a particular issue for overseas drivers given its proximity to Auckland International Airport;

• Port access to and from the southbound motorway lanes is circuitous via Onehunga Harbour Road and Neilson Street. It is understood that when heading south from the Port some drivers avoid the above route because of the left turn from Onehunga Mall to Neilson Street. They prefer to travel north to Queenstown Road Interchange to make the U turn on to the southbound lanes;

• Some movements are counter intuitive e.g. northbound traffic from Onehunga needs to initially travel south along Onehunga Mall to access the northbound on ramp;

• The changing of travel direction on the motorway (U turns) are not provided for;

• The northbound motorway connection is not direct to Neilson Street and requires a circuitous route along Onehunga Harbour Road; and

• No pedestrian or cycling connections are provided across the motorway at Gloucester Park Road.

Capacity and Efficiency

• The southbound motorway connections have three intersections in close proximity along Neilson Street. This is inefficient and results in congestion on those local streets and Neilson Street; and

• The circuitous route along Onehunga Harbour Road has insufficient capacity for traffic from the northbound ramp connections and results in congestion on the road.

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