The need to return to a natural state is only in the event of a full divestment/closure of the site. If the site continues to operate in some fashion, it is not

The need to return to a natural state is only in the event of a full divestment/closure of the site. If the site continues to operate in some fashion, it is not required to be restored. Also, if NSF divests the structure (essentially handing over all responsibility to some other party), I believe the new "owners" would also be bound by the need to restore. However, neither of the above would prohibit a new replacement being constructed. That being said, you're 100% correct. NSF is highly unlikely to fund the a new instrument. For a rather long time they've exhibited a distaste for Arecibo. Whoever it was that started NSF down this road back in 2006 must be quite happy with the results. What's insane is how "affordable" a telescope can be compared to the things we casually build and destroy for military spending. Green Bank Telescope (105m telescope) was constructed for around 100 Million USD, and it's a moving telescope. For the cost of a couple of F-35 jets, we could possibly build a new telescope, or make a rather large step in the right direction.