ITEM 8(a) MANAGEMENT COMMITTTE 2 JUNE 2015

Transcription

1 ITEM 8(a) MANAGEMENT COMMITTTE 2 JUNE 2015 APPENDIX Report from Harbour Management Board -1April 2015 Weymouth Harbour Walls Remediation Work

2 Harbour Management Board 1 April 2015 Weymouth Harbour Walls Remediation Work For Recommendation to Management Committee Briefholder(s) Cllr Colin Huckle, Finance & Assets Cllr Ian Roebuck, Environment & Sustainability Director: David Evans, Director of Environment 1. Purpose of Report 1.1 To update members on progress. 1.2 To request members approvals as set out in paragraphs 2.1 to Officer Recommendations Page 1 of 13 E 2.1 That the council applies for Environment Agency (EA) grant funding towards reconstruction of Walls C and D as part of the programme of grant aided schemes flowing from the Weymouth Bay Coastal Processes Study, due to report in June That members note that formal agreement of Full Council and confirmation of council financial contributions will be required for the grant applications. 2.3 That the 15 year plan is updated when the outcome of the EA funding bids is known. 2.4 That Members note the financial implications outlined in Section That the demolition of Nelsons Wharf fixed jetty is approved subject to obtaining necessary consents, in advance of the Wall C replacement works. This will be funded from the budget allowance of 42,800 for Wall 2 (Nelsons Wharf). 2.6 That consents are applied for and tender documents prepared for the replacement of walls C and D.

3 2.7 That a regime of monitoring and risk management of Walls C and D is implemented until reconstruction can progress. 3. Reasons for Recommendations 3.1 Maintenance and repair of the harbour walls is essential to ensure that they continue to be safe and serviceable. 3.2 The costs and risks of planned replacement and repair will be significantly lower than allowing a wall to fail before rebuilding. 3.3 To ensure that work carried out to the harbour walls is compatible with and contributes towards overall flood management and drainage proposals for the town. 3.4 To maximise value for money in terms of the benefits of the work achieved for the council s financial contribution. 3.5 To mitigate financial and safety risks and minimise disruption to the activities of harbour users and the general public. 4. Background 4.1 The River Wey Project Report, February 2010 The River Wey Project report, produced by Dorset Coast Forum, provides extensive information on the history, condition, flood risks and operation of the River Wey and Weymouth Harbour, as well as ideas and proposals for the investigation, repair and improvement of harbour structures and the Westham Bridge Sluices. 4.2 Weymouth Flood Risk Management Strategy, June 2010 About 450 properties in the low-lying areas in and around the town centre are at risk from flooding from a 1 in 200 year tidal event. Flood risks are due to percolation of sea water through the quay walls and ground, occasional overtopping of the flood defence walls around the harbour and wave overtopping of the Esplanade, swamping the drainage systems on exceptionally high tides. Taking account of sea level rise the number of properties predicted to be at risk of flooding in the same event increases to 1007 in 2035 and 4042 in Page 2 of 13

4 Continuing development in the tidal flood zones depends on implementation of the Flood Risk Management Strategy produced by the EA and the council. The strategy report recommends: a preferred option (Option 4b) for flood defence: o Raised Esplanade sea wall with underground cut-off wall o Limited quay wall raising o Stabilise harbour walls with underground cut-off where necessary o Possible ground raising at a later date o Possible tidal barrier across the outer harbour at a later date Urgent repairs to the Custom House Quay walls and to other sections of dilapidated sheet steel piling around the harbour. Emergency Planning measures Data gathering Further studies Public engagement and consultation 4.3 Shoreline Management Plan Review, Durlston Head to Rame Head, June 2011 (SMP2) SMP2 is a non-statutory document produced by the South Devon and Dorset Coastal Authority Group as part of the government s strategy for managing flooding and coastal erosion. It promotes a hold the line approach for the Weymouth town coastal frontages including the harbour (units 5g16 and 5g17) for 100 years. It recommends policies and actions to be taken by the EA and local authorities in the period up to the next SMP review including maintenance and upgrading of sections of the quay walls. 4.4 Weymouth Bay Coastal Processes Study The current Weymouth Bay Coastal Processes Study, managed by the council with EA funding, is due to report in June 2015 and will provide a basis for implementation of the Strategy Report recommendations and SMP2 policies. It will deliver: Validation and adjustment of the existing wave and tide model Improved estimates of flood defence over-topping rates Desirable and minimum beach profiles A review of the Preston Beach sediment transport model and assessment of options for stabilising the beach An assessment of flood flows and levels in the River Wey/harbour Ground investigation with estimates of sub-surface flows Page 3 of 13

5 Property threshold survey and revised flood mapping Refinement of the engineering options recommended in the Strategy Report Preliminary environmental information to determine the scope of necessary environmental studies. On completion of the study, an initial assessment of grant and other funding will be carried out and a phased programme of coastal and harbour work will be recommended to the EA and the council. Initially the study information is to provide a basis for the assessment and design of three proposed flood management schemes; Preston Beach, Weymouth Esplanade and Weymouth Harbour. It will inform the design of harbour wall repairs and reconstruction. 4.5 River Wey Model The EA are updating and validating the River Wey fluvial model. This will complement the Coastal Processes Study by improving water flow and level information for the harbour and is essential for assessment of the feasibility of the tidal barrage proposed in the medium term. 4.6 Quay Walls C and D Condition Wall C (Nelsons Wharf) is a steel sheet pile wall on the south side of the harbour in two sections, a 19m length to the east of the Nothe Slipway and a 12m length to the west. An inspection and condition report carried out by Ramboll 2012 stated that the piles had reached a critical condition with a factor of safety of 1.25 against bending and had little or no remaining life. Wall D (Ferry Steps) is 76 metres of sheet steel piled quay wall on the northern side of the harbour between Custom House Quay and Ferry Berth 3. The 2012 condition and inspection report indicates that the piles are in a critical condition with a factor of safety of only 0.8 against bending under some possible load conditions. Concerns were also raised about scour at the base of the piles. 4.7 Council Reports The 9 January 2013 report to the Harbour Management Board updated members on the current condition and maintenance needs of the Harbour Walls and Pleasure Pier to ensure they remain safe and serviceable and reported the findings of consultant s studies categorising repair priorities and anticipated capital costs. Consequently the Management Committee approved: Page 4 of 13

6 A budget of 1.02M, to be taken forward as part of the budget setting proposals, for the implementation of years 1-3 of the Harbour Walls Remediation Works, subject to further discussion with the EA with regard to a contribution towards the repairs of Wall C. An outline total budget of 3.627M for the 15 year period identified in the Harbour Walls Remediation Works Outline Business Case and that further discussion will take place with the EA and the county council over joint funding of this work. An outline budget of 20k per annum to be taken forward as part of the budget setting proposals, for the implementation of the Pleasure Pier Outline Business Case. Continued public access to the Pleasure Pier will be kept under close review. In April 2014 the Board approved: Progress to detail design and tender of cantilever steel sheet piled replacement of Wall C and combination steel piled replacement of Wall D. Appointment of contractor to provide early contractor involvement to refine costings and potentially identify savings, alternative construction methods and design improvements. Consultation on the removal of Nelsons Wharf jetty structure. Subsequent to that meeting the Board have been informed, through minute updates, of the requirement for site investigation to inform the detail design. The site investigation works were incorporated into the Weymouth Bay Coastal Processes Study, which produced cost savings but led to some delay. Page 5 of 13

7 5. Report 5.1 Early Contractor Involvement By October 2014, sufficient ground information was available to inform the early contractor involvement exercise for the reconstruction of quay walls C and D. Specialist contractor Commercial Marine and Piling Ltd (CMP) was appointed to review the outline design proposals and provide cost estimates. Wall C The main conclusion of early contractor involvement is that the cantilevered sheet pile wall proposed in the outline design is the most appropriate method. The estimated cost of the piling is 275k. Wall D The conclusion of the early contractor involvement is that the previously proposed combination (steel tube and sheet) pile cantilevered wall would be unnecessarily expensive. The ground investigation indicates that due to the very stiff nature of the underlying ground, boring would be necessary prior to driving to avoid excessive noise and vibration and unacceptable risks of damage to nearby buildings. The large tube piles would cause the new wall face to be about 3 metres in front of the existing wall. The estimated cost of the piling work using this method is 1.82M. An option comprising sheet piles tied back by new ground anchors is considered more economic at an estimated cost of 1.37M. With this design the new wall face would be about 1metre in front of existing. The recommended option for Wall D is now a tied sheet pile. Further investigation is required to assess whether any of the existing pile ties and anchors can be re-used. 5.2 Nelsons Wharf Fixed Jetty For the Wall C re-piling work to be carried out, Nelsons Wharf fixed jetty needs to be demolished. It is proposed that the jetty is not subsequently rebuilt. The following have been consulted on the proposal: The leaseholder, Automarine Services The Harbour Consultative Group Letter drop to residents fronting the harbour (1 to 16 Nothe Parade and 15 to 24 Hope Street, total 29 properties) Page 6 of 13

8 One response opposed the proposal because the jetty provides a refuge for pedestrians from passing vehicles. This can be resolved in detailed design, particularly as the proposed piling will increase the roadway width by a minimum of 1metre. No other objections were raised. It was requested that the council consider piling across the Nothe Slipway entrance rather than leaving the entrance open, which potentially fits with a proposal to install boat lift tracks. This may offer a relatively straightforward solution for reconstruction of the quay wall in practical terms, but would raise significant planning issues and would need to be assessed in detail. 5.3 Option to Link to Weymouth Flood Alleviation Project Where dilapidated harbour walls, such as Walls C and D, have a flood defence function the council should consider applying to include reconstruction in the programme of grant aided work that will flow from the Coastal Processes Study. As well as providing the prospect of significant grant funding and a basis for requesting financial contributions from those who will benefit, this approach will impose the rigorous appraisal procedures required by EA/Defra and a structured, coordinated approach to work in the harbour and along the seafront. The appraisal, consenting and approval processes will however take several years, with increasing risks of structural failures. The council would continue to be responsible for the harbour structures and the EA for flood and coastal erosion management, but there is obvious overlap and need for cooperation. Due to increases in estimated cost, high construction and cost risks, complex consultation and consenting issues, the need for coordination with EA schemes and WPBC Town Centre redevelopment and the need for the harbour works to be compatible with the flood management proposals, it is recommended that as far as practical the harbour wall remediation works, should be included in the phased, grant aided programme of schemes flowing from the Coastal Processes Study. Formal agreement of Full Council and confirmation of council financial contributions will be required for the grant applications. Provisional allowances for grant in aid, local levy and contributions are included in the EA Medium Term Plan for projects at Preston Beach, The Esplanade and the harbour. The key factor in EA project appraisal and programming is the benefit/cost ratio, but urgency of the work and secured financial contributions are taken into account. The Coastal Processes Study will provide initial assessments of the elements of the harbour work eligible for grant, the level of council and other contributions required and the overall scheme programme. Page 7 of 13

9 The poor condition of the harbour walls requires risk management, including monitoring of Walls C and D, in the interim. 5.4 Consents and Approvals Preliminary enquiries are being made on the following consents and approvals required for reconstruction of walls C and D on a new line: Planning Permission Marine Management Organisation consent Flood Defence Consent For Defra grant in aid, EA technical and full approvals are necessary. This requires a grant application including a Project Appraisal Report and certificate of statutory consultations to be submitted. 5.5 Contract For both walls C and D, the best approach may be to appoint a contractor under a design and build, target contract. The design and build provisions enable the contractor to make use of its own specialist knowledge and methods. The tendered target price and programme are adjusted as the work proceeds to account for such factors as the conditions encountered and instructed changes to the works. For high risk coastal work, target contracts are seen as fairer and less likely to end in expensive disputes than other forms of contract and therefore attract lower tenders. The final cost is likely to be significantly higher than the tender total, so adequate contingency allowances should be made. 5.6 Sand Jetty Following initial investigations which identified serious structural deficiencies with the sand jetty, repairs were carried out in June 2014 to reinstate one of the piles which had eroded completely. With the pile reinstated and loading restrictions in place the jetty is considered to be serviceable at the present time. However consultants advised that further investigation into the extent of corrosion of steel reinforcement within the concrete deck should be carried out within the next 4 years and it is proposed to continue with this during 2015/16. The sand jetty has no flood protection function and repairs to it are not eligible for Defra grant. 6. Financial Implications Page 8 of 13

10 6.1 The outline business case identifies 3.627M of repair and maintenance costs to ensure that the harbour structures remain safe and serviceable for the next fifteen years. 6.2 Following early contractor involvement, the estimated costs are: Wall C k Design & Supervision 6 Piles (cantelever sheet piles) 275 Nelsons Wharf Demolition 22 Accommodation Works 40 Building surveys and monitoring 5 Contingency 10% 35 Total 383 Wall D k Design & Supervision 31 Site Investigations 10 Piles (anchored sheet piles) 1,368 Drainage 10 Building surveys and monitoring 10 Contingency 10% 143 Total 1472 Total budget estimate for Walls C & D 1,855k The current council budget allowance for replacing existing quay walls C and D, is 808k. The estimated budget shortfall, without grant or other outside contributions, is therefore 1,047k. 6.3 Of the 1.037M capital budget allocation for 2013/14 to 2015/16, the spend including commitments to date is: k Walls C & D Consultants fees and ECI 25 Walls C & D commitments for further fees 10 Sand Jetty and Nelsons Wharf Investigations 21 Sand jetty pile repair 14 Total 70 Further spend proposed for 2015/16 is: k Walls C & D further investigation and risk Management work 20 Sand jetty further investigation 22 Page 9 of 13

11 Ferry berth 4 repairs 43 Total 85 Total anticipated spend 2013 to The Coastal Processes Study report, due in summer 2015, will estimate budget requirements for the overall scheme and give greater clarity on which elements of the harbour wall remediation project have a flood protection function and are likely to be eligible for Defra grant support. It is proposed to update the 15 year plan and associated budget requirements in the light of that report. Other Considerations: 7. Legal/Statutory Power 7.1 Harbours Act Local Government Act 2000 Promotion of economic and social well being 7.3 Coast Protection Act Human Resources (including Health & Safety) 8.1 The Harbour Walls form a retaining structure carrying roads, footways, working and amenity areas directly adjacent to the harbour.sudden structural failure could result in serious injury or loss of life. 8.2 The project will be managed by the Engineering Team of Assets and Infrastructure. 9. Risk Management 9.1 There are serious risks associated with not carrying out work to repair the Harbour Wall. Considering the likely timescale of replacement of the walls through the Defra grant regime, in order to limit the risk of failure of Walls C & D, consulting engineers CH2MHILL recommend that the council undertake a detailed risk analysis to determine and prioritise the risks and consequences of failure of each wall and that the council consider instigating: A regime of regular inspection and monitoring of both walls. Further investigations to better define the proposed works. Page 10 of 13

12 At this stage the only further site investigation they consider appropriate is excavations to determine the position and condition of the existing pile anchorages. CH2MHILL also suggest that the council consider the following actions in respect of wall D: Restrictions on loading. Identify and fill scour holes in front of the walls. Patch repair holes in the walls. Impose further restrictions on vessel speeds. Prohibit berthing/mooring to walls. Prohibit use of or remove Wall D steps. Install a corrosion protection system. Realign or shut down utility mains behind the walls. 9.2 The council will carefully consider these recommendations and carry out futher investigation before any action is taken. Once the condition of the existing pile anchors has been established, a risk assessment will be completed. Action to mitigate the impact on harbour users and the public will be taken before any of these measures are introduced. The risk assessment will form part of an overall risk management process which will be developed through the project phases to cover safety, financial, construction, environmental, contractual and legal risks, taking into account effects on harbour users and the general public. 10. Reputation, including Communications and Consultation (Including comments from unions on decisions affecting staffing arrangements) 10.1 Failure of the Harbour Walls and associated safety issues would have an adverse impact on the reputation of the Council. Restoring the structural integrity of the harbour walls and reducing flood risks, wilth appropriate grant in aid, external contributions and risk management will mitigate pressure on the council s finances and have a positive impact on its reputation No implications for staffing arrangements Consultation will be carried out with stakeholders including the general public, as well as formal consultation required under consenting and grant approval processes. Coordination with proposals for redeveloping the town centre and peninsula is essential. 11. Equalities Page 11 of 13

13 11.1 No implications. 12. Crime and Disorder 12.1 No implications. 13. Environmental Considerations 13.1 Impact on the environment will be managed through consultation, application of methods of environmental best practice and by use of formal risk management processes. 14. Economic Impact Assessment 14.1 Is the proposal likely to lead to an increase in the level of skills needed in the local workforce? - No 14.2 Is the proposal likely to lead to growth in local employment? No however it will protect existing infrastructure supporting local employment Is the proposal likely to lead to growth in the number of businesses? No, however it will protect existing infrastructure supporting local businesses If the overall economic implications are seen as negative what mitigating factors have been considered? 15. Corporate Plan (links to corporate aims & priorities) 15.1 Economy priority A2 Improving infrastructure to enable businesses to grow 15.2 Environment priority C3 Managing the implications of climate change, including flooding and coastal protection 16. Appendices 16.1 Appendix A Drawing No. SCH 3208/6 - Walls C and D location Plan 17. Background Documents (including relevant policy documents) 17.1 Weymouth Flood Risk Management Strategy 23/06/ Weymouth Harbour Walls Remediation Works Outline Business Case 07/12/ Weymouth Pleasure Pier Outline Business Case - 07/12/2012 Page 12 of 13

14 Report Author & Contact: David Wilson Telephone: Page 13 of 13

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