Response to Dilgp Letter, Ref. Dev2017/846, D17/159138 Dated 27 June 2017 Prepared By: Arup
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RESPONSE TO DILGP LETTER, REF. DEV2017/846, D17/159138 DATED 27 JUNE 2017 PREPARED BY: ARUP DATE OF ISSUE: 31.07.2017 REVISION: 4 DOCUMENT NO: ARP-RPT-HYD-PWD-00009 REVISION DATE DESCRIPTION 1 07.07.2017 Issued for review 2 13.07.2017 Issued for review 3 21.07.2017 Issued for review 4 31.07.2017 Final Copyright 2017 © DBC 2017 This publication is subject to copyright. Except as permitted under the Copyright Act 1968, no part of it may in any form or by any means (electronic, mechanical, photocopying, recording or otherwise) be reproduced, stored in a retrieval system or transmitted without prior written permission. Enquiries should be addressed to the publishers. DESTINATION BRISBANE CONSORTIUM www.queenswharfbrisbane.com.au Destination Brisbane Consortium for DILGP Queens Wharf Brisbane Response to DILGP Letter (DEV2017/846, D17/159138, dated 27 June 2017) ARP-RPT-HYD-PWD-00009 Rev 4 | 31 July 2017 This report takes into account the particular instructions and requirements of our client. It is not intended for and should not be relied upon by any third party and no responsibility is undertaken to any third party. Job number 247660 Arup Arup Pty Ltd ABN 18 000 966 165 Arup Level 4, 108 Wickham Street Fortitude Valley QLD 4006 GPO Box 685 Brisbane QLD 4001 Australia www.arup.com Document Verification Job title Queens Wharf Brisbane Job number 247660 Document title Response to DILGP Letter (DEV2017/846, File reference D17/159138, dated 27 June 2017) Document ref ARP-RPT-HYD-PWD-00009 Revision Date Filename ARP -RPT-HYD-PWD-00009_DOCX_1.docx Draft 1 07 Jul Description First draft 2017 Prepared by Checked by Approved by Dr. Tomoko Cecile Peille Name Jasvinder Opkar Shimamoto (RPEQ 18578) Signature Rev 2 13 Jul Filename ARP -RPT-HYD-PWD-00009_DOCX_2.docx 2017 Description Second draft Prepared by Checked by Approved by Dr. Tomoko Cecile Peille Name Jasvinder Opkar Shimamoto (RPEQ 18578) Signature Rev 3 21 Jul Filename ARP -RPT-HYD-PWD-00009_DOCX_3.docx 2017 Description Third draft Prepared by Checked by Approved by Dr. Tomoko Cecile Peille Name Jasvinder Opkar Shimamoto (RPEQ 18578) Signature Rev 4 31 Jul Filename ARP -RPT-HYD-PWD-00009_DOCX_4.docx 2017 Description Final for Issue Prepared by Checked by Approved by Dr. Tomoko Cecile Peille Name Jasvinder Opkar Shimamoto (RPEQ 18578) Signature Issue Document Verification with Document ARP-RPT-HYD-PWD-00009 | Rev 4 | 31 July 2017 | Arup J:\247000\247660-00 QUEENS WHARF\WORK\INTERNAL\DESIGN\CIVIL\FLOODING\02 REPORTING\05 REVIEWS\20170706 DILGP_EDQ\ARP-RPT-HYD-PWD-00009_DOCX_4.DOCX Destination Brisbane Consortium for DILGP Queens Wharf Brisbane Response to DILGP Letter (DEV2017/846, D17/159138, dated 27 June 2017) Contents Page 1 Context 1 2 Responses to DILPG 2 3 Further Discussion 7 3.1 Brisbane River Catchment Flood Study (BRCFS) 7 3.2 Comparison with Existing Bridges 8 3.3 Modelling precision 9 4 Conclusion 9 Attachment 1 DILGP Letter, Ref. DEV2017/846, D17/159138 dated 27 June 2017 Attachment 2 Arup Memo, Ref. ARP-RPT-MAR-PWD-00004 dated 15 June 2016 Attachment 3 Email correspondence, Arup and WSP dated May 2016 ARP-RPT-HYD-PWD-00009 | Rev 4 | 31 July 2017 | Arup J:\247000\247660-00 QUEENS WHARF\WORK\INTERNAL\DESIGN\CIVIL\FLOODING\02 REPORTING\05 REVIEWS\20170706 DILGP_EDQ\ARP-RPT-HYD-PWD- 00009_DOCX_4.DOCX Destination Brisbane Consortium for DILGP Queens Wharf Brisbane Response to DILGP Letter (DEV2017/846, D17/159138, dated 27 June 2017) 1 Context This technical note has been prepared in response to the Department of Infrastructure, Local Government and Planning (DILGP) letter dated 27 June 2017 (Attachment 1) with regards to the Priority Development Area (PDA) application for the Queens Wharf Brisbane Integrated Report Development (QWBIRD). The Minister for Economic Development Queensland (MEDQ) requested that a Hydraulic assessment technical note be prepared in relation to flooding considerations; the letter states: “The purpose of the requested Hydraulic assessment technical note is for EDQ to undertake an informed consideration of the practicality and implications for the proposed development to achieve a maximum of 10mm outside the PDA for all events up to and including the 1% AEP and 2011 event.” This Hydraulic technical note should be read in conjunction with the Plan of Development (POD), Volume 3 – Attachment K – Hydraulic Assessment Report1. As a reminder, the hydraulic modelling indicates that the maximum increase in flood levels as a result of the QWBIRD is +17mm along Montague Road in West End, observed in a modelled 2011 design storm event and in a 1% AEP (Annual Exceedance Probability) storm. Modelling indicates that this location is sensitive to small increase in the river levels, i.e. in the order of 5-10mm. 1 http://www.dilgp.qld.gov.au/planning/development-assessment/priority-development- area-development-applications.html. ARP-RPT-HYD-PWD-00009 | Rev 4 | 31 July 2017 | Arup Page 1 J:\247000\247660-00 QUEENS WHARF\WORK\INTERNAL\DESIGN\CIVIL\FLOODING\02 REPORTING\05 REVIEWS\20170706 DILGP_EDQ\ARP-RPT-HYD-PWD- 00009_DOCX_4.DOCX Destination Brisbane Consortium for DILGP Queens Wharf Brisbane Response to DILGP Letter (DEV2017/846, D17/159138, dated 27 June 2017) 2 Responses to DILPG For ease of reference, Sections 3 (a) to 3 (d) of the DILPG letter (attachment 1) are provided in blue text, with the corresponding responses in black text. The Hydraulic assessment technical note shall assess potential mitigation options, which must include: a) Redesign of the proposed bridge pier and pile cap to reduce bridge head losses and therefore afflux. Whilst more challenging from a structural engineering viewpoint, the realignment of the pier component to the direction of flow is to be investigated. The Redesign of the proposed central bridge pier and pile cap has already been discussed between Arup (the hydraulic modeller for DBC) and WSP (the bridge design engineer for DBC), upon request from Arup at various stages of the design. Attachment 2 provides a technical note prepared by Arup on the discussions regarding bridge pier flood afflux. Further email discussion dated May 2016 is also included in Attachment 3. Prior to the design refinement, modelling was performed by Arup to better understand the contribution to flooding of each vertical component (main supporting piles, pile cap, upper supporting cap and superstructure). It was found that for all the modelled events, the supporting piles were the main contributor to the flood impact, in generating approximately 50% of the impact, with the pile cap and upper structure generating each 25% of the impact (the exact contribution depends on the event). It is important to note here that the numerical modelling is 2D-depth averaged and the form loss is distributed across the water column. Alternate numerical modelling including CFD and 3D modelling were discussed as a method to better evaluate the impact from the bridge and overcome the simplification of the 2D scheme. These approaches were deemed not suitable for this assessment as being non-traditional for the assessment of impact and likely to be rejected by the State reviewers. Refinements of the central pier have been performed including: - Realignment and streamlining of the main supporting piles arrangement (16x1500mm piles) in the direction of the flow. This involved a rotation of approximately 18 degree to reach optimum alignment. - Consideration and testing of a larger pier support element with a more hydrodynamic efficient shape. It was identified that a series of circular piers was in theory less ‘efficient’ from a hydrodynamic perspective than a larger pier, oval shape of the same footprint. A steel skirt was tested as a flood mitigation option, however due to lateral freeboard requirements and other structural restrictions, the subsequent improvement with regards to flood impact was found to be negligible. A larger single circular supporting pier was also tested instead of two rows of smaller piers; the improvement on flood impact was also negligible. The outcome of various discussions was that the central bridge pier shape, size and configuration could not be further refined or redesigned whilst maintaining the architectural vision (June 2016). ARP-RPT-HYD-PWD-00009 | Rev 4 | 31 July 2017 | Arup Page 2 J:\247000\247660-00 QUEENS WHARF\WORK\INTERNAL\DESIGN\CIVIL\FLOODING\02 REPORTING\05 REVIEWS\20170706 DILGP_EDQ\ARP-RPT-HYD-PWD- 00009_DOCX_4.DOCX Destination Brisbane Consortium for DILGP Queens Wharf Brisbane Response to DILGP Letter (DEV2017/846, D17/159138, dated 27 June 2017) Further analysis has been performed to investigate whether the bridge pier could be relocated closer to the river banks in a lower flood velocity zone, as illustrated in Figure 1 to Figure 3 below. Figure 1: Velocity Magnitude and Pier Relocation, 2011 Flood event Figure 2: Pier relocation investigation, 2011 Flood event (plan view) Figure 3: Pier relocation investigation, 2011 Flood event (section views) ARP-RPT-HYD-PWD-00009 | Rev 4 | 31 July 2017 | Arup Page 3 J:\247000\247660-00 QUEENS WHARF\WORK\INTERNAL\DESIGN\CIVIL\FLOODING\02 REPORTING\05 REVIEWS\20170706 DILGP_EDQ\ARP-RPT-HYD-PWD- 00009_DOCX_4.DOCX Destination Brisbane Consortium for DILGP Queens Wharf Brisbane Response to DILGP Letter (DEV2017/846, D17/159138, dated 27 June 2017) As a minimum, the bridge pier would need to be relocated 45m towards south bank. As stated by WSP and Grismshaw: ‘such relocation would upset the balanced nature of the spans, and may disrupt the concept to such an extent so as to require a complete redesign. The resulting out-of-balance will require significant ballast or tension foundations to be constructed at the South Bank end to act as a counter balance for the cable stayed main span. From an engineering perspective, this is not practicable due to significant constraints at the South Bank, including the Wheel of Brisbane, significant in-ground services, and the required clearances at Clem Jones Promenade - notwithstanding the significant costs associated with a less optimal design.