I think there is a couple stashes around there. Some items are in the taller grey building. You can get up on the roof (I forget how exactly), then work your way down through the building. There's also an underground area with rats is the one you found underneath the big silos, and then it connects to the warhouse-type building. Another is near the taller grey building in the corner of the factory. Behind the building is a swampy area (you can see Bloodsuckers sometimes if you use your binoculars to look down into the swamp). (1) Go around the back of the building and head down towards the swamp (There should be a broken cement bridge to the right as you're walking down). (2) When you walk down there should be a cement slope leading down to the swamp. That cement slope has an area underneath it (there's big openings). I think the area underneath is for drainage. (3) Anyway, if you're going underneath the slope, now facing back towards the Cement Factory, there should be a broken vent / grate on the right side behind a bunch of Chemical anomalies. Crouch into it and there is an important stash. Sorry for the really late reply that might not be too helpful!