I played your game and done both sewers objectives but the Pig was bugged and blocking my way, tunnels are too small can't pass him. One more thing is that the Night Vision is totally useless, maybe add a flashlight that would be handy.
There are more objectives, its actually a mutated dog, sorry for that you should be able to lure him back in so you can get past him, its only really the area with the bars before the worker room thats a bit too tight Perhaps. Its actually infrared, and i beg to differ, flashlight and batteries would kinda ruin the Atmosphere. Really appreciate your feedback and thanks for playing I'll see if i can do something about those metal bars.
*EDIT* I've updated the main monster / mutated dogs nav mesh agent radius and removed some other collisions. Build is updated. Please let me know how it is now. Also a hint; If you have drained both sewer rooms, return to the worker and you will have to pickup a key card on the pipe, take that and find a door where you can decent below. Infrared should only really be used in very dark areas, and it is intentionally not very useful to be honest, sometimes it helps sometimes it's confusing as it sees dust etc.