That soil looks good and damp. Almost reminds me of the swamp land where the house I grew up in was located. dark, rich soil and heavy wet grey clay. The hole I'm digging is in pure red clay. There is white and black where water runs through once in a great while. That stuff is rock hard. Tool of choice is a mattock/pick axe. I am using about 5 different shovels depending on what I am digging. makes a difference. I was going to go with a retro fit drain at first. I changed my mind and am going with a 3" Koi Toilet 2 that I am modifying to be like the Koi Toilet 1. I just want to hide as much pipe as possible. If something does go wrong, I can always cap it off and do a retro-fit. I am hoping that never happens though.