If I had the space to avoid the area I would, but I would also not hesitate if it was the best location. A lot of people on smaller lots have no choice but to go over them. I have not personally heard of any septic issues in my area because of this. I doubt chickens could damage the system, but I could see a backup impacting the chickens. The home we bought last year currently has a seepage pit, so it takes up very little room in our 1/3 of an acre lot, but before that I had chickens and gardens over leaching fields with no issues. I would speak with the installers and get their opinion as they are the experts on that particular system!
