Thames Tideway Tunnel aka the Super Sewer.
Why do we need this super sewer? Well, London is getting bigger and bigger and with all those extra people are doing what people do the sewer system can't cope. In addition it's never been that good at coping with heavy rainfalls and that has led to lots of raw sewage going straight into the Thames.
So there is a clear need for additional capacity, lots of it, and the statistics are pretty mind boggling. The main tunnel will have a width of 7m, enough for three double-decker busses to drive side by side along it (take that the Italian job) - that's wider than Crossrail.
6 tunnelling machines will be boring away about 75m under London at 100m / week with something like 25 km of tunnel to dig.
Of course it won't be cheap, with figures like £ 4.2 billion being quoted and there's a lot of engineering involved disturbing familiar places such as Putney Embankment, home of the start of the University Boat Race.
The digging will of course generated lots of soil, but the plan is to take as much as possible off by boat along the Thames itself - resulting in a projected 60% increase in river traffic.
Inevitably there will be disruption but it won't last for ever and at the end there's planned to be 3.5 acres of additional public spaces. And hopefully the Thames will be a lot healthier with much less outflows.
So what about the Bubbler? Well this is the Bubbler:
And that would be good news indeed.