Ive been through that tunnel a "million" times. Theres mainly some radroaches, but they leave you alone if you stay away and dont shoot them. Some raider, feral ghoul, maybe a couple super mutant... that is until you reach the actual place near the station.
Radroaches
Raiders
Feral Ghouls
Super Mutants
I've beaten the game and have GOTY and have beat all the DLC except Point Lookout. I'm like level 27. But I can't play right now cause I don't have it on PC, and my PS3 isnt at my house at the moment :(. Hint: What I do to survive when I'm in tunnels is, stay sneaking, run(fast sneak) to get where your going if you hear something, walk slowly and look for it tapping your VATS button while turning around to locate it before you locates you. Only turn on your light if you REALLY need it. If your sneak indicator says caution, stop moving, use VATS to find who is looking for you and try to back away from them and turn off your light if its on so they will forget about you then kill them as they walk away.