Prepper Stash: Fire in the Hole
Find this one at the Wellington Residence, south of Orville Creek in the southeast corner of John's region.
There are usually about three cultists hanging around outside, including a sharpshooter. Take out the three before proceeding.
The stash note is on a rock out front (east) of the house.
Enter the house, and look for the mine entrance- it looks just like a giant gaping hole in the floor (plus ladder).
There's a lot of Bliss down here, but not enough to hurt you. Be sure to grab the dynamite from the table just by the ladder (it's hard to miss)
Use a stick to blow up the barricade at the east end of the tunnel (remember to stand back).
The tunnels here are full of dynamite, so feel free to knock down any barricades you come across- there will always be at least some minor loot behind them. There are also some Blissed out Angels down here- arrow headshots and takedowns are good from preventing their whole resurrection trick.
Barricades on your north and south will be the dead ends, the barricades leading east will take you to a room with a waterfall (there will usually be one Angel on the far ledge).
Jump over to that ledge, and throw a stick of dynamite at the blocked waterfall.
This will also open a new passage behind you (to the east).
Follow this to the stash, and mission completion.
You can technically retrace your steps to get back to the surface, but it's much quicker to grapple up out of here.