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Standing water removed from London’s City Hall

The Project

ACO Building Drainage provided a bespoke drainage system for London's City Hall, one of the most visually striking buildings in London and the home to the Mayor of London's office, the London Assembly and the Greater London Authority (GLA). Located on the south bank of the Thames, alongside the More London development, City Hall is one of the capital's most symbolically important buildings.

The Brief

To develop a drainage system that would tackle the problem of standing water that was accumulating around City Hall's perimeter because of surface run-off from the granite slabs that surround the building, its proximity to the Thames, tidal action and high water table levels. The new system had to be designed so it could run exactly parallel to the faceted glass facade and be installed close to the structure in order to complement the building's design.

The Solution

ACO Building Drainage recognised that instead of removing the original drainage system, the problem could be solved by increasing its capacity along a 35 metre section of the perimeter and installing a series of direct connections to the existing mains system. The new systems was manufactured in modular form so it could be easily assembled on site with each section comprising two 1500mm straight runs of 155mm wide grade 304 stainless steel channel. Sections were welded together to form a wide 'V' shape that fits exactly to the angle of City Hall's glazed panels. The flanged ends of each panel are precision cut to form the same angle when they're bolted together. The channel also has 'Heelsafe' grating which is locked in place for additional security and pedestrian safety. Two 100mm outlets connect the sump sections to the existing rainwater manholes.

"The close working relationship established from the outset between ourselves and the ACO team gave us the assurance that the system would operate effectively in all soil conditions and, critically, would take into consideration the very sensitive visual environment around this important building. It was also easy to install, ensuring minimal disruption to the main entrance."

David O'Sullivan, Groundworks Contractor,
McNicholas Construction.


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