Dave's Designs in Silverdale designed our septic system but that was 18 years ago. I recommended them to some guy from work after he was told he needed a pressurized system and they were able to design a gravity flow system so he ended up savings thousands. Check them out as their services were reasonably priced and they found a location that perked on my property which has a lot clay. We are thinking about selling. I think you can avoid capital gains taxes once you are 50.