Prepper Stash: Dumpster Diving
Find this one in Dodd's Dumps, well north of Fall's End. You will need the grapple to complete this stash.
The prepper note is just outside an office trailer (note that there is an arcade poster in the trailer itself)
Read it to start the mission.
Climb up the ladder to the trailer roof. You'll see a rope-marked jump platform blocked by hazard cones. Note that these hazard cones tend to mark your path forward.
Clear the platform by shooting the oil drum between them.
Jump across and bear right, along the red containers to the yellow toolbox.
Observing the hazard cones, turn left (east), and jump to the blue crates, then the red container beyond them.
Swing across the next gap (west), with your grapple.
Keep going west, following your marker to ground level.
Your marker will update. Follow it into the complex, through ankle-deep water, to the stash door.
The door needs power. Trace the power cable to a switch in the northwest corner of the complex.
Turning on the switch electrifies the water, so you'll have to pick you way back. Head straight south, then bear right as you come inside, following some pipes then crates to the top of a shelving unit.
From there, turn left (east), and jump across.
Knock away some of the blue barrels here, then jump over the chainlink fence to the south, onto some generators.
From the generators, turn left (east) to a jump platform.
You can't jump straight to the door from here. Keep going east to find a walkway that connects to the door via some planks.
Enter and loot the stash to complete the mission.
Note that you can easily exit by following the planks back to hidden exterior doorway.