- You can't build a mile tall tower though.

- Keeping water out of a hole is a solved problem.

- as discussed in other comments here, adding more height gives you more PE for the same amount of weight so it's a very valuable investment that pays profits over 20-100 years for your one time investment.

https://docs.google.com/presentation/d/17FI-jrI9RWS3q7Ng44Yh...