I happen to have a degree in engineering and I was expecting to see an engineering drawing or something official (maybe even on vellum) - what I got was best described as "back of the napkin with a coffee ring as a bonus decoration". First, is that realistic, I don't want to harp on it if in fact that's what they're all like, and second how truthfully can I take the measurements and layout of the "drawing"?
I'm looking at the drawing and it looks like they deliberately routed the drain field so that it goes off in weird angles, makes several beelines for the massive Douglas Fir in my backyard and otherwise doesn't efficiently utilize the space provided for it. I was expecting a nice layed out route involving 90 deg bends and long branches. What I see is the first line making a large oblique angle into the middle of the yard then sending branches back toward the tree, finally connecting back to itself after circling the tree.
Was it common to design the field to incorporate trees as a means of absorbing water?