We still have salt mines which have not operated since the 1800s. I visited them when I was serving on a prison site location committee. They're huge and would be excellent storage sites. I wouldn't be surprised if multiple states have mines or other "dead" sites that could be used as well. We also have dozens of closed coal mines which could be utilized in the same way.
Perhaps we are underestimating the ability of our scientists to deal with CO2. I'm betting they'll come up with economical storage ideas - possibly including ways to make C02 inert.
Hunter
I don't care if it hurts. I want to have control. I want a perfect body. I want a perfect soul. - Creep by Radiohead