At 15-20ft below sea level, not another cent should be spent on that sewer. So I won’t offend anyone here who actually like NOLA, I won’t say what should be done with it.
The sinkhole could be a real danger though. Hydrogen sulfide, butane, methane, and other gasses have accumulated. And, the thing keeps growing. Hopefully the worst doesn’t happen; but, it doesn’t look like this will end well