I’ve been reading about the original sewer project in
“The Great Stink of London”. There are interesting similarities in the enormous costs, political conflicts and motivation. Both projects were initated because of sewerage getting into the Thames. The Victorian design was put in place to take both household waste and surface water and deposit them further down the river by Becton. During the course of the project they realised that even this was not going to be acceptable and ended up taking the solid waste and dumping it at sea. More recently they have started burning it and using the heat to drive turbines and generate electricity from human waste.
The problem with the existing Victorian sewers is that they just don’t have the capacity to handle all the households and all the rain water. Hence when we have a bit of rain or Sophie Dahl shows us a new recipe for prune curry then the system overflows. So the new tunnel will take that extra and get it down to the power station rather than discharging into the river. You may not agree with the costs or the disruption caused by the works I am sure this will be as facinating an engineering project as per the origional project.