Forth Replacement Crossing: Queensferry Bridge – Principal Contract

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CEEQUAL Excellent (90.7%) – Whole Project Award
Version 4, March 2018 | Queensferry, Scotland

Client: Transport Scotland
Contractors: Forth Crossing Bridge Constructors (Dragados, American Bridge International, Hochtief and Morrison Construction
Designers: Ramboll, SWECO, and Leonhardt Andra und Partner; Jacobs / Arup (Joint venture)

Project summary

The Forth Replacement Crossing (FRC) is the project behind the Queensferry Crossing, the new road bridge connecting both sides of the Firth of Forth. By adding to the Forth Bridge and the Forth Road Bridge, Transport Scotland has safeguarded one of the most vital connections in Scotland’s transport network. The Queensferry Crossing opened to traffic on 30 August 2017.
The new bridge was designed and developed with an international team of architects and engineers. It is the tallest bridge in the UK, and an iconic structure with a 2.7km span over the Firth of Forth. 23,000 miles of cabling suspends the bridge from three narrow and elegant towers.
The Queensferry Crossing is replacing, not increasing, the road provision for general traffic. Future travel growth will be accommodated by increased use of public transport. As a dedicated public transport corridor, the existing Forth Road Bridge will provide additional infrastructure capacity for sustainable forms of travel, including walking and cycling.
While the new bridge is the most eye-catching element of the project, the scheme also involves a major improvement to the trunk road network in the east of Scotland with the upgrading of 19.7 km of roads connecting to the new crossing and the building of 4 km of new connecting roads. These plans were developed after extensive consultation with local communities and other stakeholders. By maximising the use of the existing road network, the FRC’s connecting roads resulted in less impact on the environment, properties and communities.
An Intelligent Transport System (ITS) is being used along the length of the Queensferry Crossing and connecting roads. The result is that a 22 km ‘Managed Motorway’ regulates the traffic travelling across the Forth with the aim of increasing the efficiency of the road, reducing congestion and improving road safety.

Landscape issues

Over 400,000 new trees, grown from the seeds of local trees, were planted. The new planting comprises large blocks of woodland, smaller areas of scrub woodland, hedgerows and individual trees, to integrate the new roads into the surrounding landscape and provide screening where required.
Transport Scotland procured all the trees through a separate contract with a plant nursery to prepare, supply and deliver good quality, local provenance stock throughout the construction period for use in the landscape and ecological mitigation planting. When areas of the site became available, these areas were planted to allow early establishment of the trees. Two areas were also planted in advance of the construction works starting and so benefitted from at least 5 years of growth before the new roads opened.
The design of the project ensured existing stone walls and other built landscape features were protected and retained where practicable. Field boundaries which were removed or disturbed along the A904 road were replaced with boundaries using the same design and materials as the original boundaries.

Ecology and Biodiversity

The Firth of Forth has a number of protected ecological sites, including Special Areas of Conservation, Special Protection Area and Sites of Special Scientific Interest. Before any construction work started, a large number of ecological surveys were undertaken to ensure appropriate mitigation measures were designed into the scheme. This included construction noise limits to minimise disturbance to birds in the marine environment. In addition, extensive mammal fencing and a number of mammal crossings were incorporated into the new roads.
An unavoidable impact from the project was the direct loss of land within St Margaret’s Marsh SSSI, which is notified for two habitat features; transition saltmarsh (reedbed) and saltmarsh. Both of these habitats are uncommon in Scotland.
In consultation with Scottish Natural Heritage it was agreed that a commitment to restore the remaining marsh to favourable conservation status was the preferred option to ensure long-term biodiversity benefits. A management plan was developed and a steering group set up which included input from local community groups and other organisations.
The mitigation required hard engineering for improving the water balance on the marsh and provide increased inundation by sea water on the salt marsh vegetation to direct the recovery of the designated features. This involved the construction of 3 sea-wall sluices to the Firth of Forth, in addition to 5 internal sluices between the compartments within the marsh.
The success of the mitigation is being monitored so it can be measured in terms of returning the site to conservation status. The effectiveness of the inundation strategy, management interventions and the direction the desired vegetation develops requires an adaptive long-term management strategy and iterative approach to ensure success. To date, the management of the saltwater inundation and reed management have seen a decline in the dominance of the reed over some of the site which is facilitating a diversification of the plant community.

The historic environment

Extensive archaeological works were undertaken in advance of construction starting. This comprised trial trenching and recording throughout the site, with further investigation undertaken wherever items of interest were discovered.
Evidence of a 10,000 year old Mesolithic Round House was identified during the excavations of a field at Echline in South Queensferry. A large oval pit was discovered along with hearths, flint and arrowheads. The radiocarbon dating showed this site to be one of the oldest of its type found in Scotland. The discovery has added valuable information to the understanding of buildings erected by Scotland’s first settlers after the last glaciation.

Energy and Carbon

The development of the Queensferry Crossing project was influenced by a desire to minimise embodied carbon which resulted in making maximum use of existing infrastructure, reducing the scale of new construction and applying best practice during design and construction. This included retaining the Forth Road Bridge as a Public Transport Corridor and an improved active travel route.
For operation of the Queensferry Crossing scheme, maximum use has been made of new technology to increase the efficiency of the network and reduce emissions related to congestion. This is achieved through implementation of Intelligent Transport System (ITS) measures, which improve traffic flow and minimise stop-start traffic conditions. The Queensferry Crossing has also been designed to allow individual cables to be replaced during maintenance without closing the bridge. Intelligent LED lighting systems have been introduced to allow lighting to dim when not required.
During construction the contractor also made efforts to minimise carbon emissions through optimising the cut/fill strategy to avoid the requirement for materials being transported off-site, using recycled concrete for fill and drainage and having an on-site concrete batching plant to minimise transportation.

Effects on Neighbours

The effect on neighbours was an important consideration from the start of the planning process for the project. The Queensferry Crossing and the new southern approach road are located close to residential areas which had previously had a semi-rural setting. This required a careful design to ensure visual and traffic noise impacts from the project were minimised. Extensive community consultation was undertaken and an Environmental Statement was published.
Mitigation for traffic noise included a combination of acoustic barrier and embankment. Additionally, low road noise surfacing was used on the mainline roads. Extensive woodland planting was carried out to screen views of the new roads and traffic with early planting undertaken in many areas.
A Code of Construction Practice (CoCP) was also published which set out an extensive set of controls to ensure the construction phase of the project had minimal impact on the surrounding communities.
A stringent noise control regime was in place during construction which included noise limits as set out in the CoCP. Another requirement was for the formation of a number of working groups, including a Noise Liaison Group (NLG). This group, which included members from the client, contractor and local authorities, met monthly throughout the construction period to discuss ongoing and future works and noise levels. Noisy activities were controlled by a Plan for the Control of Noise and Vibration which was agreed by the NLG. Monitoring stations were located around the site boundary which continually recorded noise levels. The results of the monitoring and the minutes from each NLG meeting were made publically available through the project website.
Similarly, during construction, air quality monitoring stations were also located around the site with real-time results available to the contractor to assist with management of activities which generated high levels of dust. Air quality was discussed at regular Environmental Liaison Group meetings which were attended by local authority representatives. Monthly air quality monitoring reports were also made available on the project website.
A dedicated enquiry helpline was set up at the start of the construction period to allow members of the public to contact the project team with any queries or concerns.

Relations with the Local Community and other Stakeholders