During Microsoft's E3 conference a new trailer for Tom Clancy's The Division was shown off detailing the events of the games next big expansion Underground.
In this trailer players can see a little bit into what they will be doing in the game, and they also provide insight into the reasoning. A voiceover explained that The Division’s enemies have regrouped in the sewer systems of New York, and are mounting an attack. The missions in Underground will be procedural. Based on the explanation many have theorized that this means enemies and their types will change on each playthrough, however we are unaware of whether this will affect the sewers unlike dungeons in other games. You can watch the trailer for yourself below: