New London Embassy

London’s biggest regeneration project received a crucial boost when plans for a new £620 million US embassy in Vauxhall got the green light in 2012.

Wandsworth councillors approved the application for a huge glass cube, a key element in the revival of a 450-acre stretch of rundown industrial land known as the Nine Elms Opportunity Area.

Hundreds of embassy staff will move from their existing site in Grosvenor Square in 2017 and are expected to live, shop and exercise in the “New South Bank” district, which will also include the restored Battersea Power Station.

Before work could be started on the main structure, WJ were hired to help with the construction of the basement carpark which needed up to 40,000 m3 of contaminated groundwater removing.

The source of the water was the perimeter diaphragm wall which provided a hydraulic cut-off into the London Clay. The subsequent excavation was approximately 170m by 120m and up to 9m deep. WJ designed an effective dewatering solution consisting of 6 No. internal pumping wells and 2 No. internal piezometers.

Due to the site’s past life, external water levels needed to be carefully monitored. A legacy of contamination in the groundwater within the gravels was detected, so WJ provided a treatment system consisting of a high efficiency tower stripper for mass removal of contaminants. This was followed by a final ‘polishing’ using activated carbon vessels to ensure the discharged water was compliant with the necessary discharge consent.

A monitoring system was also installed to track the water level. Additionally, trigger levels were established to prevent excess external drawdown being generated. The project was completed without any trigger levels being breached and all discharged water was compliant with the discharge consent throughout.

Another successful contract involving the regeneration of a previously run-down area of the capital.

• LOCATION: Wandsworth, London
• CLIENT: Confidential
• MAIN CONTRACTOR: Sir Robert McAlpine