Where to put all the dirt excavated from the graywater ditch?

We built a container in our side yard. It is principally made of 8x8x16 blocks with 2x8x16 caps on the top. The internal dimensions are 32″ from the wall, 15 block long (which makes 14 blocks on the inside, since half a block overlaps at each end) and 3 blocks + the cap high. So the inside holds 32 x (14×16) x (3×8 + 2) inches in volume. This comes out to just under 108 cubic feet. Our original excavated amount was 84 cubic feet. In my opinion this is a pretty good ratio considering that dug earth “fluffs up” and when put back into the planter is not trampled on. I hoped to do a lot of composting in the planter so its volume may expand thru the years. So rule of thumb is to make the planter 20-25% larger than the dirt you have to put in it.  In the photo you can see a bucket where a compost bucket has already been planted.

Update: Over a year later, this planter has turned out well. I was able to improve the soil last year by bringing home over 1000 pounds of vegetable and fruit discarded from the company cafeteria. All that material has decomposed except for some volunteer tomato plants that are coming up now. With the orientation of the planter, it gets morning sun but is protected from the harsh afternoon sun. And with a soaker hose on a timer, the spring crops get reliably watered.