Maritime Infrastructure

Navigational Risk Assessment for Tideway's super sewer works

Navigational Risk Assessment for Tideway's super sewer works

The Tideway project on the River Thames in London is a Nationally Significant Infrastructure Project (NSIP) for a wastewater storage and transfer tunnel between Thames Water’s operational sites at Acton Storm Tanks and Abbey Mills Pumping Station.

Our team members have worked on this project since 2015, having established and led cumulative assessments across the whole River Thames and at each of the 12 in-river worksites, working for all three Tideway Main Works Contractors.

One of the worksites, King Edward Memorial Park Foreshore (KEMPF), is one of the highest discharge Combined Sewer Overflows (CSO) into the river. The Tideway work here will divert sewage into the new super sewer as it passes 60m below ground as well as extend the park with new land for terraces and seating.

Our work

For the KEMPF worksite, the Tideway East Main Works Contractor (CVB) needed NASH Maritime to assess and quantify the navigation risk posed by the marine construction and the permanent in-river structure which would be left following completion of the tunnel, particularly with regards to intertidal terraces and potential impacts of CSO discharges on river users.  

To ensure the statutory harbour authority (Port of London Authority) could understand and consider the navigation risk posed by the various phases of work, including the application of any identified risk control mitigation measures, we worked closely with CVB and their contractors Land& Water in undertaking the assessment.

Drawing upon our wider experience on the river beyond the Tideway project and our familiarity with the site, stakeholders, key issues, and navigation impacts, we took a two-stage approach on our assessments:

>Stage 1. consisted of a high-level review, focusing on design critical issues that impacted navigation so that these could be addressed in design including through developing embedded risk control measures.

>Stage 2. was a comprehensive navigation risk assessment of the finalised design and marine works activity bringing together all risk controls.  

Works at the King Edward Memorial Park site are ongoing, and the Tideway Project is due to complete in 2025.

Image copyright: Tideway, King Edward Memorial Park foreshore

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