Trampoline Dreams

For years I've been telling my husband about my dream of creating an inground trampoline.  How difficult could it be?  Just dig.  And keep digging.  And plop the bugger in.  Right?

Image found here.

Well, apparently "it's not so simple", says he... what, with the whole water draining issue and such.  He also reminds me of the fact that we live on a quarry.  Solid rock just a few feet below us.

Oh yeah.

I've mentioned blasting, but for some reason he doesn't think a trampoline would be quite worth that hassle.  Is blasting difficult?  Expensive?  And who exactly do you call to blast?  Can it be a do-it-yourself project?  Or is that illegal?  And okay, I'm guessing probably dangerous.  But possible? Anything's possible.