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The project involved the stabilisation and repair work to a traditional masonry arch bridge. The bridge over the River Sprint had suffered significant scour to the western abutment during Storm Desmond flooding in late 2015. The remedial works were to arrest further movement and to install a new concrete saddle.

CLIENT: Cumbria County Council     VALUE: £600,000     COMPLETION: Autumn 2016    

DURATION: 19 weeks    CONTRACT: NEC 3 Option E

SCOPE OF WORKS

  • Liaising with statutory authorities including the regional Environment Agency office to procure the necessary permits.
  • Ecologists employed to carry out wildlife surveys, develop working procedures and monitor the site.
  • Fish and Crayfish capture/relocation.
  • In-water temporary works to dam and over-pump the River, creating a dry working environment.
  • Fluming was considered but discounted due to environmentally important gravel deposits and temporary support requirements under the bridge.
  • Design and installation of a temporary works centring system.
  • Underpinning of scoured abutment.
  • Pressure grout to the voids in the abutments.
  • Design and install concrete saddle.
  • Waterproof new bridge deck.
  • Design and construct upstream training wall.
  • Design and install Willow Spiling to downstream training wall and embankment.
  • Load testing of bridge upon completion.

DESIGN WORKS

  • Thomas Armstrong (Construction) Ltd appointed one of our regular local design partners, Curtins Consulting, for the Design element of the project.
  • Curtins’ Kendal office served the project easing arrangements for meetings & site inspections.  
  • Curtins have the in-house expertise to analyse
  • Load capacity of the masonry arch structure.
  • Structural stability in the temporary state
  • Due to the damage
  • During remedial construction work
  • Interpret structure monitoring data to ensure safety.
  • Scour assessment improved future resilience through upgrading of training walls
  • Temporary Works assessments
  • A good working relationship was maintained with Cumbria County Council’s Technical Approval Authority.
  • Independent design check facility at Curtins’ Liverpool office.

RISKS/CHALLENGES/LESSONS IMPLEMENTED

  • Early contractor involvement benefitted procurement of Environment Agency permits in advance of site work.  
  • Design & Build team flexibility improved project timescales.
  • Allowances for working and lay down areas need to take into account Public access rights of way.  
  • Fish capture needs the requisite Natural England licences in advance.
  • River flows & water levels can fluctuate rapidly, even in Summer months, threatening temporary works & progress.  
  • Twelve inch pumps are a specialist item and have a substantial lead in time.
  • Close monitoring of structure during dewatering operations highlighted bridge abutment movement due to the reduction of water pressure. Contingency response plan safeguarded the structure and workforce.
  • Construction loadings balanced to safeguard masonry arch. (During removal of fill and concreting of saddle)
  • Monitoring of structure during the Works to safeguard our workforce.  
  • Willow planting preferred by the Environment Agency as it complies with the Water Framework Directive.

SUCCESSFUL OUTCOMES

  • No pollution incidents
  • Wildlife was successfully relocated
  • Structure was safeguarded
  • Collaboration with Technical Approval Authority to achieve Client objectives
  • Structural strength for 40/44t traffic loading achieved
  • Future resilience improved, led by river/structure scour assessment
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