Making deep end shallow - What to use as fill

This year we have to replace our vinyl liner in our in ground pool. While we are getting into this repair we thought it would also be a good time to bring the deep end up to 5’. Our problem is we don’t know what to fill the deep end with. We had to replace some pipes (of course under concrete) last year & still have a pile of concrete that we thought about using along with sand to fill then finishing with sand & topping with 3 inches of vermiculite. Any and all comments would greatly be appreciated. Sharon

Sharon,
I wish I had some ideas to help you, but unfortunately, this is an area where I have no expertise at all. But, just wanted to stop by and say hello and welcome you to the forum. We are glad to have you! Hopefully, someone will be along soon who can offer you some advice.

Sand is not stable fill -- one leak, and your fill is gone.

If you use concrete fragments, you have to try to use something on top that will not migrate into the spaces between the fragments of concrete. Of course, you can grind the concrete up intoin to gravel sized pieces.

Dunno what short of fill you have available in your area. Around here, the tendency would be to use chert backfill, and a 'whaley-packer' to compact it in 4 - 6" layers, that is, if the contractor were doing it 'right'.

Thanks your comments were helpful. Sharon