Size volume to include I&I during wet weather conditions. I would use max hourly inflow for the facility you've described, but you might be able to justify max daily.
Detention time: 10-30 minutes during design inflow, depending on length of force main; can be longer with odor control provisions, but these are very costly and have huge O&M ramifications.
Aeration: Min. 1.25 scfm / 1k gallons storage AND min. of 1 mg/L at standard air conditions.
Don't forget to budget Explosion Proof (Div 1) electrical for anything (even control voltage) within storage volume. Also, check local code, you may also need Div 1 within a given proximity outside storage as well. That is a big-ticket item that is often overlooked...I blew my first design job's budget on that one!
Remember: The Chinese ideogram for “crisis” is comprised of the characters for “danger” and “opportunity.”
-Steve