London: West Ham Flood Alleviation Scheme

DAWSON-WAM installed a number of temporary steel sheet piled cofferdams for main contractor Costain at the Abbey Mills Pumping Station in West Ham as part of the West Ham Flood Alleviation Scheme as part of their works for Thames water.

The first cofferdam was to enable the construction of a stilling chamber. The second was to allow the construction of a vent chamber and valve chamber. The vent and valve chambers are in extreme proximity and therefore a single cofferdam encompasses the two structures. The chambers will facilitate the management of future flood relief. 

The stilling chamber cofferdam comprises of 54nr piles or approximately 32 linear metres, arranged in an arc around an existing circular shaft with an approximately 15m radius.

The second dual purpose cofferdam comprises of 74nr Arcelor 10m length AU20 piles - approximately 55 linear metres - and 35nr 5m length piles - approximately 20 linear metres.

The cofferdam is positioned on top of an original brick culvert possibly dating from the construction of the Bazalgette designed pumping station.

The short piles have been installed over the top of the tunnel, requiring two levels of support frames to be installed at the two locations to prevent deflection of the short piles once the construction cavity has been excavated. The excavation is to approximately 3.5m depth.

The support frames were installed by Costain.

DAWSON-WAM carried out installation and extraction following construction of the chambers over a number of visits.

Additional works to the contract included the installation of a CFA contig piled concrete chamber for tunnel boring machine access comprising approximately 65nr piles to a depth of 12m.

For further information please click on the UK Water Projects Online Link