Whorlton Bridge - current programme
What's happening to Whorlton Bridge.
Because the bridge is a grade II* listed structure and a Scheduled Monument, we will need to work closely with Historic England and the Environment Agency (EA) throughout the process.
We have to carefully test different sections of the bridge before we can establish what work will be needed and the future capacity restrictions of the bridge. This will then allow us to develop a plan of what works are required. Before any works can start and at each stage, approval from the EA, Historic England and Scheduled Monument Consent (SMC) which has to be submitted to the Secretary of State for Digital, Culture, Media and Sport for approval.
Programme of work
The following is the anticipated programme. This assumes no delays throughout the process and that the scheme progresses as intended:
Develop Investigation and Testing Design Contract and appoint a Contractor
December 2020 to mid-March 2021 - COMPLETE
Complete design of temporary works and Investigation and Testing scope
Mid-March to end of May 2021 - COMPLETE
Submit a Scheduled Ancient Monument consent application
May 2021 - COMPLETE
Procure a testing Contractor to execute the works
June and July 2021 - COMPLETE
Scheduled Monument Consent granted
July 2021 - COMPLETE
Carry out Investigation and Testing Contract
Final report received from Contractor in August 2022
Revisit the assessment following completion of the site works
Completion due in December 2022
Design the required strengthening and refurbishment works and apply for Scheduled Monument Consent
Preliminary design in progress. Detailed design to commence in December 2022
Tender, plan and execute repair works (subject to funding)
December 2022 onwards
October 2022 update
The final testing and investigation report from Taziker Industrial Ltd. has been reviewed by Design Consultants Pell Frishcmann, who have highlighted two areas of Taziker's work that has been inconclusive:
- Strength of the lower stirrups that connect the timber beam to the suspension hangers.
- Geometrical and condition information for the chain saddles positioned to the tops of all four towers.
The requirements and preliminary design for the refurbishment of the bridge are currently being considered by Pell Frischmann (Design Consultant) VolkerLaser (Specialist Contractor) and Blackett-Ord Conservation (Accredited Conservation Engineers), who will work together to update the cost estimates and progress into a detailed design.
The project is on track to be completed no later than March 2024, as stipulated by the Levelling Up Funding.
Further thought and detailed design is needed in the following areas:
Strength of the timber deck:
To allow the bridge to reopen to vehicles and pedestrians, some of the materials used in the timber deck need to be improved along with a review of the layout and width of the deck. This work is nearing conclusion and is then subject to approval by Historic England.
Strength of the wrought iron lower stirrups:
The shape of the stirrups has been accurately recorded and assessed and the results show that the stirrups are theoretically only just strong enough to hold the required load on the bridge. Plans are underway to remove some stirrups and load test them in laboratory conditions to confirm the assessment results and that no modifications are needed.
Vertical alignment of the timber deck:
The current vertical alignment of the timber deck is not favourable and therefore the deck needs to be levelled out over the full span to allow even distribution of the loadings. This is how the bridge was initially designed. In order to allow maintenance and tuning of the vertical alignment, alteration to the tapered wedge details shown in Image 2 is being considered. Proposals include the addition of a height adjustable wedge as shown in Image 3. This will be subject to approval from Historic England.
July 2022 update
Taziker Industrial Ltd. have completed investigation and testing works on Whorlton Suspension Bridge.
The results of their findings determine that the initial method proposed to separate the main suspension chains for inspection and analysis was unsuccessful due to the significant extent of corrosion to the main chain pins that connect the chain links together. The site works were therefore put on hold until a new design could be developed to allow the safe and sympathetic removal of main chain pins.
We have concluded that the main suspension chains can support the anticipated pedestrian and vehicular loading. Elements of the timber deck and connection details to the hangers still fail assessment for the anticipated loads and our consultant engineers are progressing alternative designs and assessment methods to overcome the few remaining assessment failures.
We are still working to conclude and evaluate the findings obtained over the last 6 months, while continuing to work to develop the refurbishment and where necessary strengthening scheme to allow the bridge to be reopened to both pedestrians and vehicles within the timeframe set by the Levelling Up Funding bid.
We have found a number of typical defects associated with fatigue and consistent overstressing of individual members. There are also widespread generic defects associated with the age and type of the structure.
January 2022 update
Testing works commenced on Monday 1 November 2021 and we have concluded approximately 90% of the overall testing and investigation scope of works. There have been issues with the initial proposed method to separate the suspension chain links for inspection and therefore our contractor had to leave the site prior to Christmas to develop a revised chain separation plan. The contractor is planning to return to site in the middle of February to complete their remaining works.
Design and assessment work is ongoing to take into consideration the findings of the testing and develop the refurbishment works proposals. The delays experienced during the investigation and testing period have unfortunately had an impact on the overall programme. This has been updated in the table below.
October 2021 update
As part of the government's Comprehensive Spending Review on Wednesday 27 October, it has been announced that we have been successful in bidding for £20m from the Government's Levelling Up Fund for projects in Bishop Auckland including funding to support the repairs and reopening of Whorlton Bridge.
Securing this funding is a major step forward in the project to repair the bridge and will also support the development of a visitor centre to celebrate the bridge's transport heritage.
August 2021 update
Testing works on the bridge were planned to start in August, but have been rescheduled for the coming weeks, hopefully starting by Monday 13 September.
Although this will delay our reports, we do not expect it to impact greatly the overall programme.
It is anticipated that the investigation works will be completed by the end of November, when we will revisit the assessment before developing our plans for the future works.
The table outlining key project dates has been updated below.
July 2021 update
The Scheduled Ancient Monument consent application has been approved by Historic England.
We are currently progressing with the final phases of the procurement process to appoint an appropriate contractor to carry out the testing works.
Once appointed the contractor can begin the works on site to begin the testing of the structure.
June 2021 update
Scheduled Ancient Monument consent application was submitted to Historic England at the end of May 2021 and we are waiting for the outcome of the application.
We are currently progressing with the initial phases of the procurement to appoint an appropriate contractor to carry out the testing works.
May 2021 update
Our appointed specialist steelworks contractor Taziker have been working alongside accredited conservation specialists, designers and suppliers to develop the plan for the required investigations along with a Scheduled Monument Consent application for the consideration of Historic England.
We are currently intending to submit the Scheduled Ancient Monument consent application to Historic England at the end of May 2021.
Due to a short delay in the procurement process, we have revised the dates of the initial phases of the programme to reflect this. This should not impact the programme for the repair works which are scheduled to begin in July 2022 subject to funding.
Procurement of the contractor to execute the investigation and testing works is to commence in June 2021.
March 2021 update
We are pleased to say that the contract for the provision of temporary works designs, methodologies and specifications was awarded to Taziker on Friday 12 March.
We will now be working closely with them to develop proposals for a scheme of investigation and testing works. This will give us a more detailed understanding of the overall condition of the bridge including areas currently hidden from view.
Once the scheme has been developed it will have to be submitted to Historic England for Scheduled Ancient Monument consent before any physical testing can take place. This will then allow us to progress to the next stage which is to appoint a specialist Contractor to undertake the investigation and testing works.
February 2021 update
A procurement exercise is currently underway to appoint a steelwork contractor competent in assessment and inspection of historical wrought iron structures. The contract will require the contractor to design a series of temporary works systems to allow separation of the chain links and hangers in various locations for further inspection and assessment. A programme and methodology of in-situ non-destructive testing will also be developed. It is a critical requirement of this phase to understand how fatigue has compromised aspects of the structure over the 190-year life.
The investigation and testing contract will be developed alongside an accredited Conservation Engineer who will assist in ensuring the methods proposed are acceptable to Historic England. Before the works can commence on site, Scheduled Ancient Monument consent will be required once the testing plans are developed.
Tenders are due back for the Investigation and Testing design contract on the 26 February 2021.
January 2021 update
A contract has been developed that will allow an independent contractor to design temporary works to allow inspection and assessment of the bridge. We are working with our procurement team to develop the tendering proposal.
December 2020 update
Consideration of an alternative crossing has been given however there are significant access issues for construction and the costs involved would be significantly prohibitive. The construction and presence of an alternative crossing over or adjacent to the existing structure would also cause an obstruction to completion of some of the repair works.