Interesting... I've been wondering how many of the 5 million gallons will be saltwater and how many will be freshwater. Here's hoping it's mostly saltwater!
I was thinking about this huge water volume tonight and recalled that guy who had a 5,000 or 10,000g tank in his house and had to tear it down because of water damage due to evaporation... Will the evaporation from 5,000,000g of water affect the local climate??

I'll bet they'll have some condensers of some sort to collect some of the evaporated water... Or maybe not?