It terminated just outside the crawlspace (you can barely see the end of the pipe in the picture). I have seen a fair amount of these systems and have not seen something like this before. Most are not even vented - just loose tops. I just wanted to make sure there was something that I was not aware of. Who knows what someone was thinking, but I don’t think it is right.
Sorry, I’m a firm believer in not living that close to my sh!t-box. That’s just too close for comfort.
I agree on it possibly being an overflow (a bad overflow). I would think it should have been vented on the top of the wye where the threaded cap is. It can’t be a vent if there is a trap that holds sh!t, and blocks the venting process. At least when it overflows they will have a great looking garden, unless Jethro put a cap on that too.