“Black well,” or septic tank. The first part is three rings deep; the second one ring deep. It will receive water from the bottom of the first tank, and when it overflows go into a pipe 60 meters or so slightly downhill to a sewage lagoon, in which we’ll plant papyrus, and around which we’ll plant some willow or eucalyptus trees that love water.
The soil is completely impermeable. If you dig a hole 50 cm deep and fill it with water, it will still be full a week later. A septic field would be useless. A friend suggested a mound system, running perforated pipe through a mound of sand topped by soil.
Perforated pipe? They didn’t even sell that in Mexico. And I don’t feel like spending hours (or paying someone to spend hours) drilling holes in plastic pipe. This is what they do in the country, and it works.