The house I moved into last year included an above ground pool. After removing the pool, we noticed what we thought was sand that was put on top of the ground cover (tarp). Though some of it obviously sand, there are parts that are more "pebbly" than sand. My husband says it looks like Perlite though he wouldn't be sure why they would put it under the pool.
Any way, take a look at the picture. Can anyone tell me what this is? What could have been used to level the ground?