The hole is about 8-9 feet deep ...
Built for posterity, sounds like...
I've never seen or built an outhouse that was very fancy when it comes to the pit. I have seen and used 55 gallon drums, both ends removed, when digging a hole in sand, but that's about it. Water sources, wells, drainage are the main things to consider beyond having a hole that won't fill itself in independently. Human waste won't fill a pit very fast, especially with intermittent use.
