The Challenge:

This landmark project involved the design and construction of a new six lane cable stayed toll bridge over the River Mersey, along with upgrades to 9km of the adjoining road network and associated junctions, crossing four waterways, one freight railway line and numerous environmentally sensitive locations.

The aim was to relieve congestion on the ageing Silver Jubilee Bridge and direct traffic over the new bridge, whilst ensuring an effective communication system to inform the travelling public while the demolition of existing bridges and reconfiguration of eight major road junctions took place.

During the pre-contract stages of the project, we reviewed the client‘s base design to determine whether engineering improvements could be developed to improve the original design from a cost, programme, environmental and health and safety perspective.

The estuary works presented significant challenges to traditional construction methods. Building on contaminated land meant preventing leeching into the river was essential, as was tailoring a solution to provide river traffic access with a 65-span temporary trestle bridge supporting construction work.

The Solution:

The choice of precast concrete for a number of infrastructure elements enabled us to provide low maintenance and durable structures. By standardising the design of major structural components of the scheme (pylons, piers and deck), and by using high strength precast concrete for the Freight Line Bridge, Clifton Road Bridge and the Bridgewater Junction, we maximised potential for the highest quality, safety, and streamlining of the construction programme.

The completed project includes elevated approach viaducts constructed from reinforced concrete using a specially-built moveable scaffolding system (MSS). This sped up the process of casting the concrete for the bridge decks and approach viaducts.

Our revised design of the Bridgewater and Astmoor Junction achieved:

  • Improved efficiency in the movement of traffic and non-motorised users
  • Reduced the elevation of the upper level of the junction by 4m
  • Reduced the amount of earthworks required beside the Bridgewater canal

Traffic flow was maintained through appropriate schemes and diversions based on traffic modelling. To maximise safety, a 40mph speed limit was introduced along with stopping operatives crossing carriageways and segregated walkways for pedestrians. Access for local businesses was prioritised throughout the project to minimise the impact on trade and our subcontractors were involved at the earliest stages possible through Meet the Buyer events held for local SMEs.

The Impact:

By standardising the design of major structural components of the scheme (pylons, piers and deck), and using high strength precast concrete for the Freight Line Bridge, Clifton Road Bridge and the Bridgewater Junctions, we maximised potential for the highest quality, safety, and streamlining of the construction programme.

The client supported our alternative design of the Bridgewater and Astmoor Junction and we successfully managed preparation and the approval of a modified planning application. The redesign provided significant benefits in the economic use of material and reduction in the cost of construction as follows:

  • Programme reduction of 6 months for this section of the work
  • 50,000 fewer vehicle movements with associated environmental benefits
  • Reduction of direct construction cost of £12m
  • Reduction in imported fill material provided a £3.5m capital saving
  • Reuse of 2 highway bridges provided a £7m net capital saving
  • Removal of a 6m high, reinforced concrete retaining wall on the tow path of the Bridgewater Canal. This was replaced with a landscaped green space.

Our project Communications Plan delivered proactive traffic management information leading to a dramatic reduction in the number of complaints received regarding the impact of construction works and traffic diversions.

" The Mersey Gateway is not only an iconic structure everyone can be proud of but it is already changing lives. Quicker, more reliable and consistent journeys across the River Mersey are helping businesses grow and creating new employment opportunities, bringing in new investment to the area and giving commuters more time with their families and a better quality of life. It is ‘a bridge to prosperity’ and I am confident that as the community grows more confident with the benefits the Mersey Gateway brings Halton will go from strength to strength "
David Parr Chief Executive Halton Borough Council

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