Rother District Council Agenda Item:
Report to - Cabinet
Date - 31 May 2005
Report of the - Director of Services
Subject - Landslip – Rockmead Road, Fairlight
Recommendation: That Members views are sought.
This report supports the Key Aim of Protecting and Enhancing the Built and Natural Environment.
Lead Cabinet Member: Councillor B Kentfield
Head of Services: Alwyn Roebuck
Introduction
1. Following landslips at Rockmead Road in 1997/2003 this Council, with the support of Defra, funded a Scoping Study and Geotechnical Survey to enable the Council and Defra to make decisions on the future management of this cliff. In funding this study it was essential to the Council that the findings be credible, technically sound and provide the following additional information:-
· A good understanding of the cliff failure mechanisms.
· Enable a prognosis to be made of the future recession of the cliff over the next 100 years.
· Establish local ground water levels and pressures including any water contained in the top sub-soil layers.
· Determine the impact which ground water or surface water run-off has on cliff stability.
· Make recommendations for improving cliff stability and the likely impact on the predicted recession rates.
The cost of this original study was £170,000 and was met from the approved Capital Programme with support of 35% Defra grant.
Final Draft Report
2. The draft final report of the Scoping Study has been received (copy in Members Room) and a copy given to the Fairlight Working Party on 21 April 2005. The study’s preferred policy option is to construct a toe revetment (protective wall) on the beach and a series of boreholes to reduce ground water levels on the cliff top. This action (Option 13) should achieve the “Hold the Line” option as required by Cabinet’s recent decision when reviewing the draft Shoreline Management Plan (Minute CB187/4/05 refers).
3. The Regional Engineer from Defra who attends the Fairlight Progress Meeting has indicated that following publication of the draft report he would recommend that by using the report’s technical findings, a detailed design be carried out to ascertain the detailed costing and engineering solutions of the proposals to be made in order to implement the programme, that in turn could increase Defra’s “priority score” from the current 12.2 to 15. The increase in the priority score would then make the scheme eligible for but may not guarantee funding from Defra in 2007/8.
4. Defra have advised verbally at the Fairlight Working Party on 21 April 2005 that they will favourably consider the production of the detailed design as a variation order to the existing Scoping Study with Terry Oakes and Associates acting as lead consultant. If this is their preferred option this Council will need a formal waiver from Defra exempting Rother District Council from the normal application process. The estimated cost of the detailed design is £89,000 and consists of three main parts, a) Toe Revetment on the beach to stabilise the cliff foot, b) Ground water boreholes and to remove ground water by pumping from the cliff top thereby reducing pressure on the cliff top and cliff face and c) a Environment Impact Assessment to allay English Nature’s concerns on environmental issues. Based on this Council’s historic spending on coast protection any expenditure would be eligible for 35% grant from Defra.
The benefit of obtaining a detailed design and costing by variation is the speed at which work can proceed, within weeks. If the Council choose to seek tenders for this work, (as required by the Council’s financial regulations) in preference to the variation order option, it will be considered by Defra as a new project and be required to proceed through their due process. Progress by variation or new project will not adversely affect our eligibility to Defra grant which remains at 35%.
5. A detailed justification for carrying out the works is attached as Appendix 1 and a copy of the draft final report from Terry Oakes is available in the Members Room.
6. Members are therefore asked to consider whether to extend the Scoping Study, whereby the consultant produces a detailed design and costing, for a scheme to enable an improved “priority score” to attract earlier Defra funding for a protection scheme to a “Hold the Line” policy and an application be made to Defra for an additional grant on the total of £89,000 to cover the design works. Any additional expenditure would require an amendment to the Capital Programme, making provision for the additional £89,000 expenditure. To proceed with the design work as a variation order, as preferred by Defra, will require Rother District Council financial regulations C4, C5, C6 and C7 to be waived. To confirm this the Director of Resources must be satisfied that it is in the Council’s best interest to do so, as the design work could place the Council in a position of having to commit some £5,000,000 of capital funding.
7. The benefit of moving to the next stage of producing a detailed scheme is the reduction of risk and better cost certainty of the final works, if the scheme proceeds. Better cost certainty in the final scheme provides all parties with greater confidence and increases Defra’s priority score.
8. It is estimated that the cost of preventative work to cliff top and cliff face as recommended in the Scoping Study will cost around £5,000,000. Depending on the final priority score, any proposed scheme arising from the design stage may not attract Defra support. The Council does not have sufficient capital resources of its own to meet this level of spending and therefore it is likely that loan finance would have to be sought. Even with Defra funding the financial impact on the Council could be up to £3.25 million. In both scenarios there will be an impact on the revenue budget through either lost investment income or interest payments on the loan. In progressing to the next stage of detailed design, it must be recognised that the Council may be unable to undertake the scheme due to the size of financial implications for the Council. Further discussions will be necessary with Defra to explore the funding opportunities or otherwise to see if it is possible to deliver a scheme.
Conclusion
9. If the Council supports the continuation of funding these works then it would now be appropriate to seek contributions from the residents, or their insurers, who will be the beneficiaries of these commitments.
Therefore, before making any decision Councillors may wish to seek assurance that the residents (or their insurers) would or could significantly contribute towards any potential major capital outlay.
Anthony Leonard
Director of Services
Risk Assessment Statement
Completion of the approved Scoping Study without carrying out a detailed design scheme could result in the failure to attract Government Funding for the coast protection works.
However continuing with the progress towards detailed engineering design will have cost implications upon this Council and would likely lead to Rother District Council making a substantial capital commitment to these works in the future.
1
cb050531 – Landslip – Rockmead Rd, Fairlight
Rother DC
Coastal Landslip at Rockmead Road, Fairlight – Scoping Study
Justification for additional costs for detailed design of the preferred option
Background
Terry Oakes Associates Ltd (TOAL) was appointed by Rother DC in March 2004 to review the issues and possible solutions for dealing with the problems associated with the landslide at Rockmead Road, Fairlight Cove. Their Interim Report, July 2004, identified major issues covering the areas of policy making, impact on the community, preservation of the SSSI designated cliffs and how to justify the works on economic grounds. However, there was a lack of information about the geology of the landslip which was inhibiting the development of technical solutions. The Council subsequently agreed with TOAL’s recommendation to undertake a geotechnical investigation and sought additional £120,000 grant aid to undertake the geotechnical survey. . GCG Ltd were appointed as specialist consultants and NorWest Holst, as contractors, won a tender to undertake a site investigation and geotechnical review to obtain a better understanding of the mechanisms of cliff failure and a view on the potential rate of cliff recession.
With this new information, TOAL assessed the likely scenario should nothing be done to arrest the recession of the cliff top, concluding that over the next 100 years between 148 and 195 houses could be lost as the cliff continues to recede under a cyclical failure process. The range in the number acknowledges the variation in soil characteristics which could influence the rate of recession. It also reflects the different confidence levels attaching to predictions about climate change and sea level rise. TOAL examined the technical, environmental and economic suitability of a range of options to stop or slow down the rate of cliff top recession and concluded that works, offering protection up to 100 years, are feasible.
English Nature acknowledges the seriousness of the situation at Rockmead Road and the need to look at each situation on a case by case basis. Initially, their preference is to “do nothing” but, if a decision is taken to “do something”, their next preference is for land drainage and re-profiling solutions without toe protection. However, they accept that the cliff face at Fairlight is currently obscured by the slip and that this may have been the case since 1873.
As a result, English Nature states that they may be able to accept toe protection providing it can be demonstrated that, even if natural processes continued, the virgin cliff face would not become exposed to its full height. GCG have provided an opinion which confirms this.
English Nature is also concerned about the potential damage to the foreshore of constructing a rock berm at the toe of the landslip.
The Project Steering Group, at their meeting held on 21st April 2005, received and supported the recommendations contained in TOAL’s draft Final Report, one of which was to ask Rother DC to seek funds from Defra to carry out detailed design in advance of seeking formal approval to implement the preferred option. The intention being to improve the accuracy in estimating the costs of the works, thereby reinforcing the case to reduce the Optimism Bias from the current 50% to 30% and, possibly, even lower. In achieving this lower OB figure it is expected that the Priority Score of the Preferred Option will rise above 15 points.
Preferred Option
The option with the highest range of benefit:cost ratios for all erosion scenarios is a three component engineering solution that could be used to implement a “Hold the Line” policy.
The first component is the provision of a “light” toe erosion protection berm constructed using rock armour along the toe of the existing lobe of landslip debris. The purpose of the berm would be to prevent wave action eroding the toe of the slope but it is not envisaged that it will structurally retain the slope.
The cliff slope itself would then be stabilised by re-profiling the slope to achieve an even grade between beach and cliff top level. This slope would be provided with a network of sub-surface drains to improve the soil’s physical characteristics. Re-profiling would achieve the minimum land take but must include the extent of existing tension cracks and achieve a sustainable cliff top alignment.
To provide long term stability and a margin of safety against elevated ground water levels associated with very wet winters and/or climate change, a series of pumped borehole wells along the cliff top are proposed to intercept ground water.
Whilst it is possible to implement only some of the components of the preferred option, this will not provide long term stability, nor will it achieve the overall objective of protecting the threatened properties.
Business Case for the Preferred Option
The sensitivity of the preferred option was tested by assessing the costs and benefits under a range of erosion rates and optimism bias (OB) scenarios using a range of OB allowances in accordance with Defra’s FCDPAG3 Economic Appraisal Supplementary Note to Operating Authorities, March 2003, on the revisions to economic appraisal procedures arising from the new HM Treasury “Green Book”. The results confirm that the scheme is technically viable and economically robust.
TOAL undertook additional work within the Scoping Study such that they recommended an Optimism Bias of 50% attaching to the scheme costs, commenting that the business case has been made in a robust manner and that little additional work would be required to confirm an Optimism Bias of 40%. However, Defra has set indicative thresholds of 19 and 15 for projects programmed to start in 2006-07 and 2007-08 respectively. Therefore, the scheme will have to await approval for grant aid as, using an OB of 50%, it only scores 12.2 points.
It is now intended to undertake the detailed design of the preferred option to make the case for a further reduction in the OB allowance in advance of submitting an application for formal approval of the scheme.
Objectives of the additional work
The Council is proposing to extend the remit of the current Scoping Study to include the detailed design of the preferred option to improve the accuracy of the estimated costs of the scheme. This work represents a variation to the original Scoping Study. The objectives of the investigation are: