That prison should have been the ultimate zombie-proof fortress. And if Rick would have quit agonizing over his invented moral dilemmas, he and his crew could have wiped the Goobner and his thugs off the earth, then taken over his town.
fire will kill them if it destroys the brain.
And then the series would have ended after season 2 and we'd all be sitting here wondering what happens now with no antagonists (aka zombies)