We started to dig the first trench for the earth tubes and as soon as it was full depth the walls started to collapse, a large chunk from the right and a smaller section on the left.
As we were planning to work at the bottom of these trenches this is a bit of problem… When we dug out the leach field the sides of the hole stayed put for a week and more!
I think we will have to think of another way to do the earth tubes…