You could prepare you site and your pile such that it doesn't get rained on.
I would suggest a diversion trench uphill of the pile, for starters, maybe a
swale across the whole slope. It doesn't have to be excessive, just about a foot trench with perhaps some large gravel with woodchips on top.
Incidentally, I would secure a source of clean, cheap
carbon. Woodchips would be good, if they're available in your area.
Some humanure setups involve dessication, either powered, or by adding
enough carbon that the moisture is absorbed from the solids, and then evaporates. This can be helped along by not urinating in the poo
bucket, or by installing a diverter if you have a more comprehensive setup.
I am guessing that your poo pile is going to be separate from the place where your daily deposits are made. I would put a roof, or some kind of tarp supported over the pile by a frame, like an easy-up or car port tent supports. This would keep your poo pile from getting all wet and trying to visit you downhill.
The specifics depend largely on how you wish to proceed to treat your feces. If you wish to just build a pile and add to it occasionally, I suggest lots of carbon, which would be piled 18" around and atop the initial pile, with an additional topping layer added for every deposit.
If you structure the pile such that it is sitting on a pallet, it would be easier to put in a coil of weeping tile or some other structure to let air in as much as possible. It might also be a good idea to bury the short end of an L-shaped bar in the centre of your pile, such that when it is rotated around, it turns the pile.
Another reason to build on a pallet is so that you can make the whole platform tilt slightly to one side and downslope, and so that you can drop an old tarp underneath. With this setup, it would be possible to direct any leacheate either to a reservoir, a hole filled with woodchips, or a bed of ornamentals or poop-eating perennials.
More details will make any further advice you get more useful. Keep us posted, and good luck.
-CK
A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, take orders, give orders, cooperate, act alone, solve equations, analyze a new problem, pitch manure, program a computer, cook a tasty meal, fight efficiently, die gallantly. Specialization is for insects.
-Robert A. Heinlein