I suppose it was built without the back pressure (ie doesn’t rely on back pressure for stability) and the change in pressure over time is quite gradual (this drawdown has been occurring over years) so I don’t see a significant problem.
It also gets massively thick as you get deeper. Far more than you would think by looking at the exposed part. Check out old construction photos.
It also gets massively thick as you get deeper. Far more than you would think by looking at the exposed part. Check out old construction photos.