I was living in another state at the time. But I vaguely recall that he had to get an inspector to verify the holes were drilled, before it was filled in, and again at the end to verify that there wasn’t a a hazardous hole in the ground anymore.
But I could be wrong.
Since I now own the house – I know that we’re still on some list, somewhere, as having a pool. Zillow says we have one. And we get junk mail from pool supply companies trying to sell us chlorine, pool covers, etc. But mailing lists live forever. My dad removed the pool 20 years ago.