An early morning walk around Cologne on Thursday before my workshop I came across the above street scene and like many previous visitors I assumed the sprawling blue pipes were some weird new innovatively TRIZed version of a sewage system. Further googling and the best explanation I can find is on Peter and Marians blog that its because:
excavation is ongoing in the city and the ground water is such that it has to be pumped out in order for more excavating to take place. The ground water is pumped through the blue pipe over several streets to disgorge into the river.
Sounds feasible to me.