Replacing a bridge over water is a complex challenge that requires specialist expertise, such as bridge jacking or sliding. Here are some of the key challenges.
Bridges are a vital component of our infrastructure, and often they exist to carry a road or a railway line over a body of water such as a river, estuary, or canal. Sometimes a bridge might need to be replaced because it’s no longer fit for purpose, or repairs are not considered to be a technically or economically feasible option.
Replacing a bridge over water is a complex challenge that requires specialist equipment and expertise, such as bridge jacking or sliding. Often, there are also historical and environmental considerations to be taken into account, as well as the logistical problems of closing a major transport route. Here are some of the key challenges involved.
Working with water
The location is obviously one of the biggest challenges, as water is a very powerful force and strong currents or tides may be involved, as well as variable depths and unpredictable weather conditions. Large projects are usually planned for the summer when conditions are more favourable.
Accessibility is often also tricky, especially in larger bodies of water. Barges or floating platforms may be necessary to move materials, and specialist lifting equipment such as pontoon cranes may be required to carry out construction processes.
Traffic management
Replacing a bridge is a costly, complex and time consuming process. Therefore, the work is benign carried out because it’s strictly necessary, such as for a key transport link with no quick and easy alternative routes. This means that research and planning is necessary to find out the best way to manage traffic.
This could be done by installing a temporary bridge near to the site, creating a land-based diversion, and investigating the quickest construction methods and off-peak times to carry out the work. If the waterway is used for boats, canals and so on it will be necessary to avoid accidents and blockages with clear warning systems and alternative routes.
Environmental considerations
Rivers and estuaries are natural ecosystems that support a wide range of wildlife, and they may be legally protected sites or home to protected species. It will be necessary to carry out an environmental impact assessment to identify areas of concern, and if necessary put mitigation measures in place.
This might include planning work to take place outside of breeding or migration seasons; creating new habitats for wildlife, and minimising debris and sediment build up in the water.
Protecting heritage features
Britain has many historically or architecturally significant bridges that might be protected by legislation. It will be necessary to liaise with the relevant authorities and heritage bodies to ensure that the designs for the new bridge are approved. This might involve preserving some of the original elements of the bridge or using like-for-like materials or designs.
Managing timelines and costs
Replacing a bridge over water will be slower and more expensive than work on land. The engineering design might include solutions such as prefabricated sections of bridge to speed up construction times and keep costs predictable and manageable.