King Soopers has some UHF Freqs, (No repeaters) they use for security. As I remember they are grouped and different stores use different groups, but all the radios have the groups programmed.
They used to hire a lot of off duty denver sheriff deputies, but now it is mostly their own employees unless there is a need for more muscle like store 21. (Queen Soopers)
I think they are in the FCC database but you will have to get the analog or digital tones with a scanner;
In the parking lot is close enough. Most of the traffic will be employees in the attic or watching cameras in the office spotting shoplifters and alerting the security guards who to stop with (real) beef in their pants