APPENDIX L AHAD KHAN DEVELOPMENT ENGINEERING REPORT

Transcription

1 APPENDIX L AHAD KHAN DEVELOPMENT ENGINEERING REPORT

2 Technical memo - Specialist Unit To: Nicola Broadbent, Team Leader - North West Resource Consenting Unit, Auckland Council From: Ahad Khan, Team Leader, Regulatory Engineering Auckland Council Date: 19 June APPLICATION DESCRIPTION Application and property details Applicant's Name/ Application Name: Panuku Development Auckland / America s Cup Wynyard Hobson Service Centre Application Number & Water Allocation Consent Number: Activity type: Site address: BUN , LUC and DIS The Management of Stormwater, Wastewater, WaterSupply, Earthworks, Erosion and Sedimentation Control and Geotechnical related matters from a district perspective. Wynyard Point & Wynyard Wharf, Auckland CBD Introduction Scope of Report 1.1 This report provides a development engineering review and assessment, from a district perspective, of the management of effects relating to the following matters associated with the America s Cup Wynyard Hobson resource consent application, which I refer to in this memo as the Application : a. Stormwater; b. Wastewater / water supply; c. Earthworks and erosion and sediment control; and d. Geotechnical matters / coastal processes. 1.2 The focus of my report is on the district plan provisions of the Auckland Unitary Plan Operative in Part (AUP) relevant to the above matters. The regional provisions of the AUP contain different triggers and thresholds, and are addressed by other Council Consent: WAT

3 specialists. Specifically, I note that other Council specialists have addressed: stormwater and earthworks / erosion and sediment control matters from a regional perspective 1 ; coastal processes 2 ; and geotechnical matters My geotechnical assessment relates purely to managing any instability that could arise as a result of undertaking earthworks, such as deep trenches to accommodate drainage works. Mr Brightman will address other geotechnical matters. Application Documents 1.4 The following application documents are particularly relevant to this report: a. Application for Resource Consent: Assessment of Environmental Effects (AEE), America s Cup Wynyard Hobson, 13 April 2018, prepared by UNIO Environmental Limited (UNIO) (Application Document 4); b. The Applicant s Proposed Draft Consent Conditions, 13 April 2018, prepared by UNIO (the Applicant s Draft Conditions) (Application Document 4); c. America s Cup Physical Infrastructure Technical Report for Resource Consent Application, Wynyard Hobson, 11 April 2018, prepared by Beca Limited (the Beca Infrastructure Report) (Application Document 9); d. Beca s Basis of Design report dated April 2018 (Appendix A to the Beca Infrastructure Report); e. America s Cup, Wynyard Hobson, Coastal Processes and Dredging Technical Report by Tonkin and Taylor dated April 2018 (Application Document 16); f. America s Cup Geotechnical Report for Resource Consent Application, Wynyard Hobson by Beca dated April 2018 (Application Document 25); g. The Draft Remediation Action Plan, Appendix F to Beca s Preliminary Site Investigation Report (Application Document 27); h. Concept Engineering Drawings by Beca (Application Documents DS5.1 to DS5.3); i. America s Cup Stormwater and Services Technical Report for Resource Consent Application, Wynyard Hobson by Beca dated April 2014 (Application Document 28). 1 Hillary Johnston and Gemma Chuah have addressed regional stormwater, and Fiona Harte has addressed regional earthworks. 2 Sam Morgan. 3 Charlie Brightman. Consent: WAT

4 2.0 Summary of Proposal and District Engineering Assessments Proposal as relevant to Engineering 2.1 The development of infrastructure for the America s Cup applicant s proposal involves a range of engineering-related matters, from a district perspective, concerning the management of stormwater, wastewater, water supply, erosion and sediment control and earthworks and coastal processes. 2.2 A full description of the proposal is provided in the AEE. In brief: a. Construction around the Wynyard Point, and Halsey and Hobson Wharves is proposed to provide infrastructure and accommodation for America s Cup yachting syndicates and events from late b. Five syndicate bases are proposed on Wynyard Point between Jellicoe St and 90 Brigham St. These are proposed to be constructed by upgrading the wharf with cement-stabilised columns or piling to approximately m deep. Earthworks for building platforms and other site preparation earthworks are also proposed in this area. c. Private stormwater infrastructure is proposed to be installed for the management of stormwater from the buildings on and from Wynyard Point, and Halsey and Hobson Wharves. Minor trenching works to accommodate these drains and outfall structures are proposed. No new stormwater is proposed to be diverted to the existing public network. d. Public wastewater connections and private wastewater including private pump stations and rising mains are proposed to service the development at Wynyard Point, and Halsey and Hobson Wharves. New wastewater is proposed to discharge to existing network. A conditional approval from Watercare Services regarding discharge to their network has been obtained. e. Earthworks associated with installation of the private and public stormwater, wastewater and water networks are generally of minor nature. f. Stability arising from the minor earthworks for installation of stormwater, wastewater and water networks are generally low. g. Construction activities are proposed to occur over a period of 18 months. Site Locality and Environs Descriptions (Relevant to District Engineering Matters) 2.3 Construction works are primarily to be undertaken in the following areas: Wynyard Point on the eastern side of Hamer St between Jellicoe St and 90 Brigham St; Consent: WAT

5 Jellicoe St (works for services); Halsey St (works for services); Viaduct Events Centre (Halsey Wharf); Hobson Wharf. 2.4 The applicant provides a description of the site and receiving environment in the AEE at section 8. In brief: a. The AUP zones the site area as Business City Centre Zone and General Coastal Marine Zone. A number of precincts also apply, including the Wynyard Precinct. b. At the Wynyard Point construction area, surrounding land-uses to the north and west are predominantly industrial in nature. Immediately neighbouring businesses include the Firth concrete batching facility on Hamer St and the remaining Stolthaven bulk chemical storage silos to the north. c. The areas to the south of Jellicoe St and east of its intersection with Brigham St are considered to be sensitive to dust and odour as they now largely comprise high amenity recreation, retail, food and accommodation (residential and hotel) activities. 2.5 The key matters to note, for the purposes of assessing the actual and potential effects of the Application, are as follows: a) Installation of stormwater, wastewater and watersupply. In order to install these services, earthworks will be required. b) Sediment from the excavation to accommodate the stormwater, wastewater and water supply infrastructure is likely and must be managed. c) The stability of the excavated trench to accommodate the stormwater, wastewater and water supply infrastructure could result in stability issues arising if correct earthworks practices, methodology and stability devices are not properly implemented. d) Site-specific geotechnical investigations across Wynyard Point, the south side of Hobson, and Halsey Wharves indicate that the ground conditions consist of reclamation fill materials overlying a variable thickness of recent marine sediments and Tauranga Group alluvial deposits that have infilled an old valley system. East Coast Bays Formation rock is encountered at a variable depth, ranging from -15 m to -23 m Chart Datum (CD) with the axis of the paleo-valley inferred to run parallel to (and beneath) Wynyard Point reclamation. Consent: WAT

6 3.0 REASON FOR CONSENT RELEVANT TO DISTRICT ENGINEERING Reasons for consent 3.1 I have identified the key reasons for consent from a district engineering perspective below: a. E8 Stormwater Discharge and diversion The proposal involves the diversion and discharge of stormwater from impervious areas associated with the new wharf structures and landside activities. Consent is sought under rule E8.4.1(A10) of the AUP for discharge and diversion not otherwise provided for as a discretionary activity. b. E12 Land disturbance District Under rules E12.4.1(A6) and (A10) the proposal involves earthworks over an area exceeding 2500m 2 with a volume greater than 2500m 3 and requires consent as a restricted discretionary activity. c. E36 Natural hazards and flooding The proposal involves the location of buildings and structures (including temporary construction facilities and structures associated with the ground improvement works), and buildings (base syndicate bases and temporary event structures) and structures on land within the area defined as the coastal erosion hazard area. Consent is therefore required under E36.4.1(A4) as a restricted discretionary activity. d. E36 Natural hazards and flooding The Auckland Council Geomaps shows three overland flow paths within the Wynyard Point area discharging across the road and into the harbour. The GIS map also incorrectly shows a flood prone area between Brigham St and Wynyard Wharf. This is part of the Waitematā Harbour and is not a flood prone basin. As the proposal includes works within the overland flow paths, consent is sought in relation to these flow paths under E36.4.1(A42) as a restricted discretionary activity. 4.0 TECHNICAL ASSESSMENT OF EFFECTS Stormwater 4.1 Stormwater is addressed in several parts of the Application: a. Section 2.5.5, and of Beca s Basis of Design Report address stormwater in some detail. b. Section 3.3 and section 5.0 of the Stormwater and Technical Services Report Consent: WAT

7 by Beca further discusses reticulation and management of stormwater. c. Concept Engineering drawings, plans titled Proposed Services Drawings 2, Services, Sheet 1 of 6 to 6 of 6, reference numbers CU-4452, Rev B, to CU-4457, Rev B and dated March 2018 demonstrate the layout and levels of the proposed stormwater system. 4.2 The applicant has proposed to manage all stormwater runoff from the existing and new imperious areas and discharge it by use of a private stormwater drainage system directly to sea. The stormwater system, including the outfall structures will remain in private ownership. No stormwater will connect or discharge to the existing public network, and therefore no additional loading to the existing public stormwater network is proposed. The new private stormwater network is proposed to be designed for a return period of 10 years. The designed consideration with respect to 10 year return period is in line with Council s Engineering Code, entitled Code of Practice for Land Development and Subdivision, Chapter 4 - Stormwater. 4.3 Full consultation with Auckland Council (including the Council s Healthy Waters team) must occur at detail engineering design stage. Wastewater 4.4 Wastewater is addressed in several parts of the Application: a. Section 3.6.2, and subsections , , and of the Beca Infrastructure Report; b. Section 2.5, 3.3 and 4.9 of the Basis of Design Report address water and wastewater in some detail. c. Section 2.5 and section 4.0 of the Stormwater and Technical Services Report by Beca further discusses reticulation and management of water and wastewater. d. Concept Engineering drawings, plan/s titled Proposed Services Drawings 2, Services, Sheet 1 of 6 to 6 of 6, reference numbers CU-4452, Rev B, to reference numbers CU-4457, Rev B and dated March 2018 demonstrates the layout and levels of the proposed wastewater and watersupply system. 4.5 The applicant has proposed to manage all wastewater by use of private drains, private pump stations, private wastewater rising mains and public lateral. All wastewater therefore will eventually discharge to the existing public network. 4.6 All wastewater and water information was sent to Shane Lawton of Watercare for review. Mr Lawton confirmed that the design and proposal is within the scope of their approval, permit no with respect to capacity of their wastewater and water infrastructure, subject to Building Consent and Engineering Plan approval processes. Consent: WAT

8 I understand from speaking with Mr Lawton that they have been invited to attend meetings with the applicant s engineers for detail design. 4.7 Again, full consultation with the Council (and with Watercare Services) [as per the Watercare Review, Referenced 72816] must occur at detail engineering design stage. Earthworks / Erosion and Sediment Control 4.8 Very limited earthworks are proposed from a district perspective. The nature of earthworks is associated with installing the services, namely wastewater, water and stormwater. 4.9 A Remedial Action Plan (RAP), including site management measures such as soil excavation, disturbance and disposal procedures, has been drafted to cover the project. In addition, an Erosion and Sediment Control Plan will be prepared for the earthworks, referencing Auckland Council s guidance documents Erosion and Sediment Control Guide for Land Disturbing Activities in the Auckland Region GD2016/005 (2016) and Erosion and Sediment Control Guidelines for Land Disturbing Activities in the Auckland Region TP90 (2007). This will address measures such as collection and treatment of site stormwater during construction, protection of the existing stormwater network and closure of trenching An Erosion and Sediment Control Plan (ESCP) will be prepared for the landside earthworks, covering measures relating to site and stormwater management during construction. An outline ESCP is included in Appendix C to the Physical Infrastructure Report, which provides a high-level overview of measures that could be implemented. As with the draft RAP, above, this mitigates effects on stormwater and the surrounding Coastal Marine Area. I have had the opportunity to review Fiona Harte s proposed amendments to the earthworks and erosion / sediment control conditions, which I support. Geotechnical Matters / Coastal Processes 4.11 With respect to geotechnical matters, adequate measures will need to be in place to ensure that the trenches to accommodate drainage and surrounding buildings and services would be adequately protected so it would not lead to instability. I recommend several conditions in Section 6 of my report to address this The Mean High Water Spring provided is 3.39CD (Chart Datum). This figure is compatible with the New Zealand Nautical Almanac In terms on land datum (Dosli Auckland Datum), this level is equivalent to 1.65(DL) According to a separate study by NIWA, entitled Coastal Inundation by Storm-Tides and Waves in the Auckland region dated September 2013, the sea level for a 100 year return period is 2.4m (Dosli Auckland datum). See Figure 1 below. The AUP requires a metre freeboard above this figure to factor in climate change wave action = 3.4m + Wave Action (Dosli Auckland datum). (Refer to E (A9) and (A56) of the AUP). Consent: WAT

9 Figure 1 Table from NIWA study 4.14 The finished level of the wharfs would therefore need to be as per below: Wynyard Hobson Halsey = 3.65m (excluding any building freeboard) = 3.26m (excluding any building freeboard) = 3.26m (excluding any building freeboard) 4.15 The proposed finished wharf levels therefore do not meet the predicted sea levels due to climate change, once wave action and building freeboard is factored in for 100 year period In order to address this issue, the applicant has recommended in section of the Physical Infrastructure Technical Report by Beca dated April 2018, that the new piles be designed for a future 1m increase in height of the wharf deck that could be achieved using a lightweight core overlaid with reinforced concrete deck. Proposed condition 27 provides for this (Application Document 7). The increase in wharf deck level and wave panel height may be staged in 1 to 2 increments over the next 100 years in response to trigger points associated with sea level rise. The design response is expected to be refined with time to allow for updated climate change predictions As the buildings are designed for 10 years only, a pragmatic apprach as suggested by the applicant would be to review the finished level of the wharf against climate change for the period ranging from 2040 up to 2060 which would be prior to the end of consent and therefore allowing the adaptative measures to be incoporaed in the schedule assest renewal of major repair The applicant has used the recently released national guidance (MfE, 2017) Coastal Hazard and Climate Change recommendation that states the following: Consent: WAT

10 Overland flowpaths 4.19 The overland flowpaths are contained within the road reserve and discharge directly to the harbour. The proposed fill of the Wynyard Wharf therefore must be done to ensure continuity of these flowpaths and its discharge points into the harbour. Assessment of Effects 4.20 I consider there has been sufficient investigation by the applicant regarding geotechnical works, stormwater, wastewater, water supply, and earthworks to provide appropriate and suitably conservative data for an adequate assessment of effects The following summarises the outcome of my assessment: a. The existing public stormwater network will not be compromised due to the new stormwater generated as a result of the proposal. All stormwater will be collected via adequately designed stormwater infrastructure and discharged directly to sea. All new stormwater infrastructure will remain in private ownership. b. New wastewater generated is proposed to be collected and discharged to the public wastewater network. Watercare has agreed to accept the additional flows subject to detailed design. c. Earthworks to accommodate the new stormwater, wastewater and water infrastructure is considered to be of a shallow and minor nature. d. Instability arising as a result of excavating the trench to accommodate the stormwater, wastewater and water infrastructure is considered to be low provided adequate earthworks methodology as per the Earthworks Methodology and Erosion and Sediment Control Management Report mentioned in the Infrastructure Report By Beca dated April 2018, the Construction Environmental Management Plan and a finalised Erosion and Sediment Plan and Geotechnical Report by Beca dated April 2018 should adequately capture these requirements. e. The mitigation proposed by the applicant to address rise in sea level as a result of climate change is considered reasonable. Consent: WAT

11 f. Overall, I consider the potential adverse effects on the environment associated with the matters I have assessed above as a result of the proposed activities as being less than minor, subject to the conditions discussed below. 5.0 SUBMISSIONS Utility Providers 5.1 I have seen the submission by Vector (#5), in which Vector states that it is appropriate to require that any works in the vicinity of its assets and infrastructure be carried out in consultation with Vector, and using methods that avoid or mitigate any potential adverse effects. 5.2 Full consultation with all other utility providers, namely Vector, Spark, Vodafone, and Chorus, must occur. 5.3 The major issues encapsulating the consultation must address at least the following: Full and unimpeded access for the utility providers to their asset; and Adequate arrangements or agreement with utility providers if their asset is proposed to be either temporarily or permanently relocated or decommissioned. 6.0 RECOMMENDATION AND CONDITIONS Recommendation 6.1 The assessment in this memo does not identify any reasons to withhold consent and the aspect of the proposals considered by this memo could be granted consent subject to recommended conditions set out below. Proposed Conditions 6.2 In Application Document 7, the applicant has proposed a set of conditions including those in relation to the management of stormwater, wastewater, water supply, related earthworks and erosion and sedimentation. As a general observation, the proposed conditions are generally satisfactory and in accordance with typical conditions used for similar activities. 6.3 I have had the opportunity to review the reports by: a. Fiona Harte (regional earthworks); b. Hillary Johnston / Gemma Chuah (regional stormwater); c. Charlie Brightman (geotech and geology); and d. Sam Morgan (coastal processes). Consent: WAT

12 6.4 I agree with the amendments to the earthworks conditions recommended by Ms Harte, and the stormwater conditions recommended by Ms Hillary and Ms Chuah. I also support Nicola Broadbent s recommendation that an amended version of the applicant s proposed condition 13 be imposed requiring the consent holder to carry out the development in accordance with (among other documents) the Beca Infrastructure Report and relevant infrastructure plans. 6.5 I recommend the following further amendments to the proposed conditions: Water and wastewater 6.6 I recommend the following additional conditions relating to water and wastewater: shall apply to all wastewater and water supply works: (a) The Consent Holder shall design the wastewater drains and water supply in accordance with the wastewater and water supply drawings referred to in Condition 13 and the Annexure to these consents. (b) Wastewater and water drains shall be provided on the following: Wynyard Wharf permanent infill sections; Hobson Wharf extension Halsey Wharf and Wynyard Point bases. (c) Construction of the physical Infrastructure with respect to wastewater and water supply shall be undertaken in accordance with the drawings provided by Beca plan/s titled Proposed Services Drawings 2, Services, Sheet 1 of 6 to 6 of 6, reference numbers CU-4452, Rev B, to reference numbers CU-4457, Rev B and dated March 2018 in full consultation with Watercare Services (as per the Watercare review, Referenced 72816) and Auckland Council. Confirmation of construction works must be in the form of an engineering completion report or any other form acceptable to Watercare Services and Auckland Council. Pre-Construction Meeting (d) A pre-construction meeting shall be held by the consent holder, prior to commencement of the construction of any wastewater and water supply works, that: (i) Is arranged five working days prior to initiation of the construction of any wastewater and water supply works on the site; (ii) (iii) (iv) Is located on the subject area; Includes representation from the Team Leader Compliance Monitoring -Central; and Includes representation from the site engineer and contractors who will undertake the works and any other relevant parties (e) The following information shall be made available prior to, or at the preconstruction meeting: Consent: WAT

13 (i) (ii) (iii) Timeframes for key stages of the works authorised under this consent; Contact details of the site contractor and site engineer; and Construction plans certified (signed/stamped) by an Auckland Council Development Engineer. Post-construction meeting (f) A post-construction meeting shall be held by the consent holder, within 20 working days of completion of the wastewater and water supply works, that: (i) Is located on the subject area; (ii) (iii) Includes representation from the Team Leader Compliance Monitoring - Central; and Includes representation from the site engineer and contractors who have undertaken the works and any other relevant parties. As Built Drawings (g) No later than 30 working days after the practical completion of the project or of any project stage which is subject to separate practical completion, the Consent Holder shall supply As-Built Drawings for the wastewater and water supply works to the Team Leader Compliance Monitoring Central. Advice Note: All new and temporary public water and wastewater infrastructure including connection points to the existing systems will require an approval from Watercare Services and an Engineering Plan Approval from Auckland Council. All new and temporary private wastewater infrastructure will require a Building Consent from Auckland Council. Additional Geotechnical-Related Earthworks Conditions 6.7 Finally, I propose the following additional development engineering conditions to address geotechnical-related earthworks. I suggest that these be inserted at the end of the existing construction conditions (with consequential amendments to the SSESCP and CEMP conditions), sitting alongside the set of geotechnical conditions recommended by Mr Brightman: x.1 The following requirements shall apply to all geotechnical-related works and shall also be addressed in the SSESCPs and CEMP: (a) Prior to the commencement of geotechnical-related works, the Team Leader Compliance Monitoring - Central shall be provided with written certification from a suitably qualified professional that all trenches for the purpose of drainage (manholes and drains), fill and foundations (if any) have been provided with adequate support and protection so they will not lead to instability. (b) The trenches, retaining walls and building foundations shall be supervised by a suitably qualified engineering professional. In supervising the works, the suitably qualified engineering professional shall ensure that trenches for the purpose of drainage (manholes and drains), fill and foundations (if any), have been provided with adequate support and protection so they will not lead to instability. Consent: WAT

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