They're in the northeast corner of the Northern Slurries. Here, I'll give you directions starting from the Slurry Engine room:
Once you're out of the engine room, head north after the cactus station:
Follow the tracks upwards:
The tracks curve westward. Turn north at the giant obstacle thingy:
You should hit a fog gate, which can be opened by filling the Slurry engine. Past it you will find the abandoned labs.
If you're starting from Jefferson's Lab, I would just go northeast until you hit the cactus station and then follow the directions above. Hope that helps.