OP stated that removing it before or after closing it not acceptable......sounds like it wouldn't fly regardless of who drives in and dumps the dirt.

A few other ideas:

1)  empty, dry, paint it, install stakeboarding rails, ramps, etc...   it's a park !

2)  fill partially with sand and fence it in ~ giant litter box or sandbox depending on who your kids are...

3)  wintertime luge track ?

4)  bomb shelter ????