In ‘Waterplan 2 Rotterdam’, the Rotterdam municipal authorities set out the general outline of their plan for dealing with the city’s water mission. Various scenarios were studied for the city centre, for realising additional storage capacity. Realising an underground storage facility linked to the new parking garage beneath Museumplein square emerged as the best of those scenarios. The underground water storage (‘OWB’, for ondergrondse waterberging) has a volume of 10,000 m3 and has been incorporated into the design of the parking garage. It is a separate reservoir, part of which utilises residual spaces beneath the parking garage, such as the space below the entrances and exits. With the realisation of this reservoir, Rotterdam created 12% of the water storage capacity needed for the city centre.
The costs of the facility were 7.2 million euros. Nooijer, 2011