Just tore through all 9 sewers and did the job board quests to eradicate the left overs in them and I got nothing for it. No achievement, no item, no nothing! Is there another sewer I don't know about? Also, what is a field goal?

This really isn't surprising. Rage is a game that is mostly about the experience rather than the reward. For instance, I do side quests so that I can see everything this game has to offer, and get to play through even more awesome gunfights, rather than a game like dragon age or fallout where I do it for xp and new loot. At the same time, I'm surprised that there is no achievement.

The achievement was mainly what I was hoping for... that and maybe a boss or two.