An Apocalypse might be Imminent….

The likelihood of long-term human survival is reassuringly high—about 70%. This suggests that life managed to endure long enough to bring Homo sapiens or other intelligent artificial creatures—which we consider to be our intellectual ancestors—to the solar system and possibly the galaxy.
The likelihood of surviving is great, but this does not guarantee an easy ride. The likelihood that some terrible event will wipe out humanity within the lifetime of today's babies is roughly 50/50. That will put an end to the rapid speed of technological advancement and make the period following human devastation of the biosphere very safe, but maybe with a modified climate. In the meantime, the likelihood of extinction in the current era is over 4% every decade.
Global epidemic, Nanotechnology disaster, Global warming, Environmental toxins, Ecosystem collapse, Robots take over, Biotech disaster, Mass insanity, There is no need for yet another examination of these risks because they are all so well known and publicly reported. Furthermore, the danger that ultimately claims our lives is unlikely to be any of the ones mentioned above, nor will it likely be closely watched or widely publicised. Instead, it will be something absurd that surprises us because no one has considered it, or even if they have, no one ever took it seriously.
In these times of crisis its best to stick with the remnants and hope to survive till the apocalypse calms down. We designed our shelter with these fore mentioned characteristics. To make the People stick together as it was the one we have been doing the best. And we gave all the access through the bridge to supress any chance of risk or contamination. These pods are made from concrete as it would be a viable option during the times of crisis, as it requires low maintenance and withstands many negative effects.