I'll sit on the fence with this one (i.e. November), but here is the evidence for Denver 23rd September. There's a video which looks into evidence of a large underground facility at Denver Airport.
Operation Mountain Guardian Emergency Exercise
September 23, 2011
Operation Mountain Guardian is a terrorism-based, full-scale emergency exercise scheduled to take place in numerous locations in the Denver metro area on Friday, September 23, 2011. The exercise will involve first responders from 81 different agencies**, will be conducted at ten separate locations and will include loud noises, simulated weapons, smoke, emergency vehicles and other equipment that will be audible and visible throughout the day.
The purpose of this advisory is to provide information that can be disseminated to the public ahead of time to avoid confusion or concern on exercise day, as well as to invite media coverage of the event.
More here
http://www.douglas.co.us/Operation_M...xercise.htm l