There are multiple bridges protruding from the Ark. I think one of them leads tot he Reactor.
Remember, Brink takes place in 2045 - they have built onto the Ark since then.
And there is a http://www.brinkthegame.com/ark/island/ overviewing the entire Ark on the Brink website. The bridge that you mention is quite one-dimensional and has only water below it with absolutely no vertical aspect until you get off of the actual bridge. Other than that there are two other bridges (not counting the short pedestrian walkways), one of which connects to the airport and the other I'm not quite sure where it leads. Anyway, all of these bridges are quite flat and offer no depth to the actual gameplay which is why I suggested the aircraft carrier alternative, which you ignored.
Sorry for claiming that there are no bridges near the Ark, but after viewing the map I would not consider them anything substantial as most of them are simply walkways over water (but by definition I guess they are still bridges). I will be especially careful now that I realize you will continue to ignore the substance of my posts and only correct the least significant errors contained in them.