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Agenda Item No

 

The Vale of Glamorgan Council

 

Cabinet Meeting: 16 December, 2013

 

Report of the Cabinet Member for the Environment and Visible Services

 

Cross Common Road Bridge, Dinas Powys - Feasibility Study

 

Purpose of the Report

1.         To advise Cabinet of the outcome of a feasibility study into the various options available to address the sub-standard condition of Cross Common Road Bridge Dinas Powys and to seek authority to progress works in accordance with the most suitable option.

Recommendations

1.         That Cabinet agree to the implementation of Option 3 of the feasibility study, i.e. that of replacing the existing deck with a shallower in-situ reinforced concrete deck including new parapets to current standards.

2.         That authority be granted to the Director of Visible Services and Housing, in consultation with the Head of Legal Services, to enter into any licence agreements that may be necessary for access to third party land in the vicinity of the bridge.

Reasons for the Recommendations

1.         To provide authority for works to be undertaken based on the most suitable option.

2.         To provide the necessary authority to enter into land access licence agreements as necessary.

Background

2.         The Cross Common Road Bridge is a sub-standard structure that has been supported by a timber frame sub-structure since 2005.  The timber frame has enabled the capacity of the bridge to be maintained but this was a temporary repair pending the replacement of the structure when capital funding became available.

3.         Capital bids for the replacement of this bridge have been unsuccessful since 2006, primarily due to the fact that the timber supports were ensuring no loss of bridge capacity but also as further deterioration of the steel structure was being closely monitored.

4.         A report from the then Environment Agency in 2008 advised that the timber bridge supports increased water levels upstream.  This report was produced shortly after a flooding event in July 2007 when a number of properties in St. Cadocs Avenue, Dinas Powys were flooded internally.  Whilst these houses are located within a known flood plain and therefore susceptible to flooding, the residents affected felt strongly that their situation would not have been so acute if the bridge supports had not been in place.  This will never be proved definitively but it is a fact that any fixed structures within the river will alter the river floor characteristics.  Such structures also make blockages by floating debris at peak river flows more likely and this would increase the flood risk for properties upstream.

5.         A number of site meetings have taken place involving residents, senior officers, local Members, Cabinet Members and representatives of the Environment Agency.  Cross Common Road Bridge spans a main river and the responsibility for main rivers lies with Natural Resources Wales (formerly the Environment Agency [Wales]).

6.         At a site meeting on 11th February 2013 it was agreed that an independent Consultant would be commissioned by the Council to undertake a principal inspection of the bridge structure.  Natural Resources Wales also agreed to undertake a river modelling exercise to establish if any upstream river flows could be attenuated to reduce flows at peak times in the St. Cadocs Avenue / Cross Common Road Bridge area.  The river modelling report is expected before the end of this current financial year.

7.         The final draft of the bridge Consultant's (Capita Symonds) report which was received in May 2013 advised that, without work being undertaken to strengthen the bridge deck, the bridge should be closed within 12 months.  This gives a suggested closure date of May 2014 at the latest.  The outcome of this report came too late to inform the initial 2013 / 2014 Capital biding process but a report was tabled at Cabinet in July 2013 detailing the outcome of the principal inspection.

8.         As a consequence of this report, Cabinet resolved that a feasibility study be undertaken into the various options available, with a further report being provided to Cabinet detailing the outcome of this study before the end of the 2013 calendar year (Cabinet Min. C1446 refers).  This report details the outcome of the feasibility study which is attached at Appendix 'A'.

Relevant Issues and Options

9.         The feasibility study considered 5 options:

(i)   Do nothing and close the bridge to traffic;

(ii)  Install a temporary "Quick Bridge";

(iii) Replace the deck of the existing bridge;

(iv) Construct an entirely new bridge;

(v)  Relocate the junction of Cross Common Road with Cardiff Road downstream;

The outcome of the study was influenced by the short lifespan for the bridge and the funding available.  Also, due to the importance of this road junction option (i) was discounted.  Full details of each option are shown in Appendix 'A' and are summarised below.

Option 1 - Do Nothing

10.      The creation of a permanent highway diversion would cost in the region of £5k.

11.      This is not considered a viable option due to the traffic diversion that would be required.  Cross Common Road is the bus route for Cardiff Bus 93, Watts Coaches 89A and Caring Coaches 86.  It is also a route used by a number of school buses.  Any permanent closure would have a serious impact on these services.

Option 2 - Install a temporary "Quick Bridge"

12.      This solution would be temporary and would cost up to £120k.  Due to the depth of the temporary bridge beams the existing road surface would have to be raised on Cardiff Road and Cross Common Road to compensate.  As a consequence of the close proximity of the bridge to Cardiff Road there is little available space to form an appropriate gradient.  It is therefore considered that this structure could create a traffic hazard greater than what currently exists at this very tight junction.  In this case the existing bridge deck would remain, though the timber props could be removed.  In addition to the water flow restriction posed by the timber props, the current bridge deck height will restrict some flows when the river is at capacity.  This is therefore not considered the most appropriate option.

Option 3 - Replace the deck of the existing structure

13.      The Capita Symonds report advises that the bridge deck has failed and the parapets are also sub-standard, whilst the abutments of the structure are in good condition.

14.      With this option only the sub-standard elements will be replaced and a shallower deck can be achieved allowing for a soffit level increase of 240mm.  This will mean that the new deck will permit greater water flows with the free flow under bridge cross sectioned area increased from 8.01m² to 10.17m².  The water flows under Cardiff Road after the Cross Common Road Bridge and the cross sectional area of this structure is 8.48m².

15.      The preferred option involves replacing the deck of the existing structure with a 'cast in situ' reinforced concrete deck and this would provide a permanent solution that could be implemented in a relatively short timescale at comparatively low cost.  There will be an opportunity as part of this work to increase the carriageway width to greater than the current 5.2 metres, though it is not expected that this would exceed 6 metres.  The estimated cost for this work is £500k and the bridge would need to be closed for up to 14 weeks for this work, where the road diversion shown in the feasibility study would be in place.

Option 4 - Construction of an entirely new bridge

16.      Whilst this scheme would provide the river flow benefits of Option 3 and would permit the carriageway width to be increased by over 2 metres, it is double the cost of Option 3 and involves a greater enclosure of the river which could be of concern to Natural Resources Wales.  It is unlikely that this work could be completed by May 2014.  The estimated cost of this option is circa £1m which is greater than the funding currently available.  This option could also result in greater disruption to the existing highway network.

Option 5 - Relocate the junction of Cross Common Road with Cardiff Road downstream

17.      This is the most desirable option as it removes the need for a bridge altogether and addresses all the highway issues posed by the current junction.  However, the Council does not own the land required and the scheme cost is greater than the budget available.  The Vale of Glamorgan Local Development Plan (LDP) Deposit Draft 2013 Policy MG 2 (29) proposes that as part of a proposed residential development at Cross Common Road, a contribution will be required as part of the development to contribute towards a new highway onto Cardiff Road (Policy MG 16 (19) refers) to mitigate the impact of the new residential development issues and also to address the safety / capacity at the existing junction.  The Draft LDP suggests that the development of 50 residential units will be completed before 2021.  However the LDP is Draft and is currently out to formal public consultation ("On Deposit") and as such the weight to be accorded to both the proposed residential and highway scheme is not as great as if it were Adopted (anticipated early 2017).   Even if it were Adopted Policy the development of the scheme and the proposed contribution to the new highway junction is extremely unlikely before May 2014.  If Option 3 is chosen the proposal as detailed in the Deposit Draft LDP would be revisited with a significant future funding contribution required from both the Cross Common development and any other future developments in the locality which may contribute to it.  The estimated cost of this option is circa £1m, though this does assume an element of land purchase cost.

18.      Whilst Option 3 is proposed, as it provides the most prompt, lowest cost solution, it is recognised that this option does not resolve the junction safety issues.  Such issues would be exacerbated by additional traffic movements and for this reason "Cross Common Road Junction Improvements" remains detailed within the Deposit LDP.  The provision of a new junction layout south of the current junction position will therefore remain an aspiration linked to any further development to the east of Cadoxton River.

19.      It is highly unlikely that any road junction layout change, as advised in 17 and 18 above, could be actioned by May 2014 and this would mean that the bridge would be closed, (assuming no progression of any other option), until such time as any new developments were agreed along with a contribution to, or the full provision of, the new junction layout.  The variables in respect to Option 5 are therefore too significant at this time for this option to be viable.  The progression of Option 3 does not however change the need for Option 5 to be progressed at the appropriate later stage.

Resource Implications (Financial and Employment)

20.      A sum of up to £650k has been made available within the capital programme from a revenue contribution and this was detailed in a report to Cabinet on 18th November 2013.

21.      Whilst every effort will be made to procure and commit funds to this scheme prior to the end of this financial year, it is likely that, due to the construction lead time, an element of slippage into the 2014 / 2015 financial year will be necessary.

Sustainability and Climate Change Implications

22.      Replacement of the existing bridge deck will assist in reducing flood risk to properties upstream, and will remove any risk of the bridge having to be closed due to structural concerns in the near future.

Legal Implications (to Include Human Rights Implications)

23.      The Council as a Highway Authority has a Legal duty to ensure the safety of the highway user.

24.      The option of a new junction under Option 5 of the Feasibility Report would have legal implications associated with purchasing of the necessary land for the realignment unless dedicated as part of the Proposed Draft LDP proposal.

25.      The replacement bridge under Option 3 might also require licences with adjoining landowners to enter their land for the purposes of accessing the structure and facilitating the works.

Crime and Disorder Implications

26.      None.

Equal Opportunities Implications (to include Welsh Language issues)

27.      None.

Corporate/Service Objectives

28.      Environment - Current and future generations of Vale residents and visitors enjoy the built and natural environments of the Vale of Glamorgan and actively protect and maintain them.

Policy Framework and Budget

29.      The report is a matter of Executive decision.

Consultation (including Ward Member Consultation)

30.      The local Dinas Powys Members have been consulted on the details of this report and have provided the following comments within two separate e-mails:

E-mail 1 - "I am of course disappointed that it has taken so long to address this problem which I brought to the previous Director’s attention in 2002 at one of Plaid’s regular meetings with the Director and Heads of Service at that time. The drawings for the proposed new junction was also a development from that meeting and was agreed by all Dinas Powys Members at the time as the preferred option rather than a new wider bridge. Those drawings have been gathering dust, due to lack of funding, since.

We are now ‘forced’ to accept a ‘last minute’ renewal of the bridge deck whilst still awaiting our desired new junction at this accident blackspot.

The report also links the proposed new junction with the proposed housing development near the bridge as though the new junction is only to be considered if the housing development is accepted in the draft LDP. The new junction should not be conditional on any other development and should be agreed and budgeted as a matter of urgency for the safety of not only Dinas Powys residents but all road users of this extremely busy road."

E-mail 2 - "We feel that this is a last minute response to an issue that local councillors and residents have been raising for many years. It would appear that there is currently no realistic alternative to the proposal to provide a new bridge deck. We believe that this is temporary solution and a new junction is essential. It is regrettable that this serious problem has been ignored for a considerable time.

It is alarming that the route might be closed for 14 week and consider is this unacceptable. We would remind Cabinet that this is one of two roads linking north and south Dinas Powys.  It also serves a bus route.  We request that any closure period is significantly reduced.

We request an assurance that that regardless of the final housing allocations of the Local Development Plan that the Cabinet confirms that it will provide a timetable to construct a new junction of Cross Common Road and Barry Road."

Relevant Scrutiny Committee

31.      Economy and Environment.

Background Papers

Capita Symonds Report - Cross Common Road Bridge, Principal Inspection and Assessment Report (Copies are available in the Members Room)

 

Cross Common Road Bridge - Feasibility Report November 2013

 

Contact Officer

Tamsin Robbins-Hill - Senior Technician, Highway Structures

Tel: 02920 673 129

 

Officers Consulted

 

Operational Manager - Legal (Committee Reports)

Capital Accountant

Accountant - Visible Services

Operational Manager - Development Control

Operational Manager - Planning and Transportation Policy

Group Estates Officer

 

Responsible Officer:

Miles Punter - Director of Visible Services and Housing

 

 

 

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