Key Highlights
- The Thames drilling project has unlocked vital data for the upcoming Restoration and Renewal of the Palace of Westminster.
- 14 boreholes were drilled in the River Thames to map geological conditions, while 2 boreholes were drilled on Parliament’s River Terrace.
- Data from these surveys will inform future designs including options for basement use and service routes.
- The project marks a significant first time river access for delivering equipment related to the Houses of Parliament Restoration and Renewal Programme.
Thames Drilling: A Critical Step in Westminster’s Restoration
Between April and September 2025, significant progress was made in preparation for the Restoration and Renewal of the Palace of Westminster. This project, spearheaded by the Delivery Authority, has unlocked vital data through a series of deep ground investigations beneath Parliament’s River Terrace and in the River Thames.
Underwater Exploration
The Thames drilling project involved 14 boreholes being drilled to depths of up to 74.5 metres in the River Thames. These boreholes were aimed at mapping geological conditions, providing essential data for future construction projects near the river frontage and any temporary works within the Thames.
On-Land Investigations
On land, two boreholes were drilled on Parliament’s River Terrace to confirm the boundary between the London Clay Formation and the deeper Lambeth Group. These ancient formations have been beneath London for tens of millions of years, key in understanding how future basements and service routes can be safely constructed.
Data and Discoveries
Among the key discoveries were remains of the 19th-century cofferdam, designed by architect Charles Barry. This find offers a fascinating glimpse into the engineering behind the rebuilding of the Palace following the fire of 1834. The data collected from these surveys will inform future designs including options for basement use and service routes.
Technical Challenges and Solutions
The River Thames works were delivered by leading UK ground investigation specialists, Structural Soils, part of the RSK Group. Gareth Jones, Senior Engineering Project Manager at Structural Soils, highlighted the complexity involved: “Our team applied specialist expertise in overwater drilling under tidal conditions, using boreholes, Cone Penetrometer Tests, and geophysical surveys to assess site geology and hydrogeology.”
The innovative approach used jack-up barges positioned opposite the Palace’s river-facing terrace. This method allowed for the safe delivery of heavy drilling equipment directly to the site, overcoming complex site conditions while minimizing disruption to the surrounding area.
Next Steps in the Restoration
These latest investigations build on seventeen previous borehole surveys across the Parliamentary Estate, adding valuable new data to support advanced digital modelling of the Palace. Early findings from the River Thames deposits have offered clues about how Charles Barry’s cofferdam was dismantled, echoing an 1849 article that described the difficulty of extracting timber piles from the river.
The project is expected to cost a significant multibillion-pound investment in the future of the Palace. This investment will support jobs and opportunities across the UK, including for craftspeople and specialists involved in the restoration works.
Conclusion
The Thames drilling project marks an important milestone in the ongoing Restoration and Renewal of the Palace of Westminster. The data collected from these surveys will be crucial in informing future designs and construction phases, ensuring that the historical significance of this iconic building is preserved while modernizing its infrastructure.
