I no longer live at this location and I have since been had active engagement in my new house build which includes a drain field. I have the following updated inputs..
Not all drain fields are installed the same.
Not all soils around the drain field are equal.
I was here and walked the new lines at my current house, They are DEEP. Like 5 to 7 feet deep. They don't have to be this deep (i saw the plan details) , I doubt at my last house they were given how other things were done.
and the soil.. My soil now is quick draining, sandy loam. I have dug a surface drainage ditch for rain water that runs along the drain field and at the beginning it can have 6+ or so inches, 20 to 40 feet later and there is no water.. It just goes into the soil only to pop out like a spring downhill. If it rains (okay pours) hard enough the water makes it down the entire ditch to my garden. I have been working to keep leaves in the ditch (counterintuitive I know, an overflow would cause zero issues) in hopes that they will break down and line the bottom of the ditch so that water stays in the ditch.
there is no way my drain field at this location would have an issue. However, at a different site with some clay, shallow pipes, etc. I can see how issues could arise and quickly at that.