Railway services on London's Fenchurch Street to Shoeburyness line have been improved following the replacement of two underbridges.

VolkerFitzpatrick worked with Network Rail and Docklands Light Railway to replace the more than 100-year-old bridges at Caroline Street and Devonport Street in Limeshouse.

This route possession was deemed one of the nation's top five high risk projects by Network Rail.

A detailed plan and further carefully considered contingency plans were developed to ensure both bridges could be successfully reconstructed – concurrently - during a 98 hour blockade over the Easter Bank holiday weekend.

To replace the Caroline Street bridge, the two existing metal decks carrying the up and down lines were removed and replaced with one composite concrete deck, chosen for ease of installation and to help reduce the noise emanating for local residents. The new deck was built in advance of the main possession and incorporated eight prestressed concrete beams with an in-situ high strength concrete stitch. The ballast, sleepers and rails were all pre-loaded onto the deck in advance, de-risking installation during the possession.

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A more complex replacement, the Devonport Street bridge needed both the metal deck, which carried the down line, and an existing girder supporting the cross beams on the up line removed. Significant temporary works to support both the dead weight of the bridge deck and also the live load from trains and on track plant were completed prior to the installation of the new girder. To install the new U-deck, the existing brick abutments were partially demolished and new precast concrete cill beams and ballast walls were installed, which was completed using a 150 tonne mobile crane lift set up within the road closure.

Several full road closures and significant traffic diversions were needed to transport the new bridges, under police escort, from the site compound on Self Propelled Modular Transporters (SPMTs) partly along the busy A13 highway.

Commenting on the project, Mark Taylor, contracts manager, said: "The completion of this blockade is an amazing achievement by the team. With numerous other stakeholders involved, the team had to interface extremely closely with all parties; with constant communication and liaison throughout. We would also like to thank local residents who were very understanding of the closures within the area whilst these complex bridge replacements took place."