Dick Peterson is a great resource. I worked with him at Austin Energy's Green Building Program and he has always been our go-to person for rainwater harvesting.
Owner / Broker, LEED AP, EcoBroker, GREEN
I agree with Betina's recommendation. They should have the answer to all of your questions.
I just checked your profile. I would never have guessed that you were born in Texas! Hope you're doing well.
Hope everything is going great. An empty whiskey barrel weighs 125 pounds, there is a company in that will ship one ready to rock and roll to Austin for $375 this is the link: http://www.ne-design.net/oak-whiskey-barrel.html