In our part of the country, you can't just dig a pit and build your outhouse on top if it. Health code regulations required us to use a 500 gallon, pre-cast concrete tank. Our local concrete supplier had a stock design that we were able to modify slightly to make it work.

We actually dug the hole for the tank by hand. It wasn't too difficult since the soil is mostly sand. The worst inconvenience was the rain during the four hours that it took Harlene and I to dig the hole.