Blackfriars bridge foreshore temporary western cofferdam
THE BRIEF
Flo JV appointed BAM Nuttall Ltd (BAMN) to design and construct a Temporary Cofferdam at the Thames Tideway Blackfriars bridge Foreshore Site. BAMN appointed Robert West Consulting with Byland Engineering Ltd. operating as geotechnical advisor, to complete the outline and detailed design of the Temporary Cofferdam Structure.
The Temporary Cofferdam is required to enable the construction of the permanent works proposed at the Thames Tideway Blackfriars Foreshore Site. The permanent works consist of the construction of a tunnel shaft, outfall chamber, culverts and new river wall, in order to intercept flow from the existing Fleet Main Sewer CSO located in the Victoria Embankment river wall. The brief for the required functionality of the Temporary Cofferdam, included:
• Retain reclaimed land south of the existing river wall to enable construction of the permanent works;
• Retain river water to enable construction of the permanent works;
• Provide a berth for construction barges during construction of the permanent works;
• Act as a working platform for construction plant traffic over the cofferdam;
• Provide temporary flood defence at a minimum level of 105.5mATD;
The Temporary Works solution developed by Robert West comprised a twin walled back to back tied temporary steel piled cofferdam infilled with dredged sand, to be located within the River Thames. Robert West engineers also proposed bespoke structures to seal the cofferdam against the existing Victoria Embankment river wall.
Our services included civil, structural and geotechnical design for the Temporary Works, as well as the definition of all nautical equipment required for the operation of the cofferdam (bollards, fenders, access ladders etc.).
VALUE-ADDED SOLUTION
RWC developed a solution within a tight design programme, which resolved the numerous challenges imposed on the Temporary Works design due to the various project constraints.
These value added elements of the Robert West design included:
- Development of bespoke details at the point of interface between the cofferdam and existing river wall to avoid intrusive works to the existing river wall;
- Assessment of the influence of the construction of the temporary works on the existing adjacent London Underground Waterloo & City Line tube tunnels;
- Development of a bespoke staged construction solution at the eastern end of the cofferdam to enable the cofferdam to be temporarily opened to allow the float-out of the permanent works culvert to intercept the existing CSO located under Blackfriars Bridge;
RWC worked in collaboration with BAM Nuttall, FLOJV and Thames Tideway within a co-located office environment in order to deliver the Temporary Works design within a challenging programme timescale.
FINAL OUTCOMES
An outline design was produced by RWC for the Temporary Cofferdam within the period of winter 2016. Detailed design of the cofferdam is due for completion in summer 2017 with a view to commencing construction on site later in the year.
