Yes, and while you are running tell him not to be so stupid all of his life. They do the same thing to houses, they backfill with dirt, then put a patio on top of it. Dirt settles, forever. If you want to jet it then you can get it down, but that would be asking for trouble next to a foundation or pool. Basically with that you flood it from the bottom of the dig to the top, which makes some serious mud. This displaces all of the air, then as the water settles out it pulls the dirt down with it. But I stll don't think I would build on it right away. I would wait at least a year. I had replaced a waterline at my house before and it was still settling three years later.