We can't stress this enough: KEEP IT SUPER SIMPLE.
There is no doubt your idea is awesome + game-changing, but the folks processing your permits are chiefly concerned with two issues: LIABILITY and WHO ELSE NEEDS TO BE INVOLVED (think of this as a version of C.Y.A.).
How could you describe your idea in the most simple, broadest terms? Which checkbox would you mark for your project: a. an art installation; b. a community event; or c. a new facility?
The more earth-shattering your project sounds, the more complex it will seem to the permit department -- which translates into more departments that need to be involved and more fees.
Then, you'll get to have the same conversation with your insurance provider. Think in checkboxes and keep it simple.