Oceans are a lot easier to manage than underground aquifers. The only time oceans become an issue is during storm surge. Boston also had more up to date levies and canals which helped make the big dig possible.

Your looking at a 100 billion dollar project if Worcester wanted to do that. Not to mention around hundreds of millions a year to maintain it into the future.

I'd rather we spend that money on public transportation, than try to fix the massive problem that is the personal automobile. We all don't need vehicles.