Yep, just what they need to drain all the floodwater into...resulting from all the other pipes, tunnels and waterways that have been allowed to be blocked up with garbage etc.

Then there are earthquakes.

I wish them well, but really I'd have thought a (strong, properly constructed) series of raised roadways, similar to the ones currently in use and being built, would be a more sensible idea in Manila.

I have worked on tunnel systems in Hong Kong, running below land and sea, so I'm aware of the many difficulties encountered... not least of which is water ingress !