The burden of proof should be on not contaminating the water supply. That is too dangerous to risk.

> Japan had great civil engineering for 100 years, they have made lots and lots and lots of tunnels. Japan overall has fantastic water quality ...

Does it? And if so, maybe that's because they make sure projects like this one don't contaminate the water supply.

> ... globally known for clean and safe bathrooms

What does this have to do with water supply? One suspects that you know very little if that's the best evidence you have.

Maybe if the only person that thinks that the water supply is being destroyed is a local politician with a massive axe to grind who is trying to extort a local stop, then maybe we should question that over the engineers who have built tunnels their whole lives.

This is specially true when these tunnel goes along many different areas and seemingly the only that complains and believes is unsafe is also the one that is trying to get a transit station in the district.

I'm sure they have plenty of evidence on why it is safe, like historical examples and such. But how do you 'prove' this to a point a politician can't just say, sure its 99.9999% safe but we can't risk it.

> What does this have to do with water supply? One suspects that you know very little if that's the best evidence you have.

The point is that Japan tends to take safety and cleanness very seriously. And they have built many train-lines and tunnels.

At one point to you personally consider the source of a claim?