One of the key milestones that was finished in May 2015 was the completion of Halton's first new bridge over the Mersey in 54 years. The new trestle bridge which crosses the Mersey is a temporary structure which will be used as a platform from which workers will construct the new bridge.
Other work to construct the bridge has been ongoing inside 2 out of the 3 coffer dams constructed in the river, however progress has been out of sight for the most part. Work has been progressing within the walls of the north and south dams in order to excavate an enormous hole into which concrete will be poured. The concrete will act as foundations for the 3 large pylons from which the bridge will hang, the largest of which; the southern pylon will be 125m tall.
The central coffer dam is still under construction, after completion of small island which was built in the middle of the Mersey. The island has allowed for the safe construction of the coffer damn, which like the north and south dams will be excavated and then filled with concrete.
One visible aspect of the project which is taking shape on the northern bank is the construction of a massive 1500 tonne movable scaffold system or MSS, which once complete will construct the approach viaducts. The structure which will attach to the bridge piers will act as a mould into which concrete will be poured to form the approach viaducts. Once each section is complete the system will move along to attach to the next pier to repeat the process.
The actual bridge spans themselves will use separate cantilever system which will move out from each new completed section. Before each section is poured the movable system edges out from the completed section, a stay cable is then installed and attached to an anchor point at the base of the mould. Concrete is then poured into the mould and around the anchor point to form a strong connection between the span section and stay cable.
There is a full 3D fly through which shows how the systems will work.
With work progressing well the latest news from Mersey Gateway is that the project is on programme to have the bridge complete and operational by 2017. We hope to provide plenty of updates before that time. Our next Mersey Gateway blog will focus on the engineering taking place away from the bridge in order to upgrade the expressway which will connect the new bridge to the M56.
Wide shot of the temporary trestle bridge and the 3 coffer dams