I just spent money to replant seed to test if it grows again, seed and that blue mulch/seed patch stuff. I had to try before I dig it up...
Taste.
I knew from the instant I saw this in “Latest Posts” that this would be the kind of thread that makes FR fun.
I would suggest that if it were a broken sewer line or septic system, there would be no doubt about it whatsoever. That’s not the sort of thing that happens and you have to wonder what’s going on. It’s pretty clear.
My guess is first some kind of insect problem, or maybe something toxic was spilt on the ground?
Unless your mom dumps her meth lab waste and a couple of pounds of salt daily down her toilet I doubt that you have a sewer line break...those are usually identified by soggy ground, actual soil settlement, growth hot spot, and smell(dogs will come from miles to frolic there). It is possible that it is a bug infestation of a hot spot, so, you would do best to dig a slit trench down several feet to check the soil for foul odor and soggy soil...the easier the digging as you go down increases the chances of an actual line break. Or you can pay several hundreds of $$$ to have a camera inserted through the nearest washout. And those are as only as reliable as the operator.
I go with grubs or other infestation. They are probably more around the septic because its warmer.
Maybe you will find this lawn question and answer useful.
http://en.allexperts.com/q/Lawns-725/spreading-circles-dead-grass.htm
The question is at the top of the page and the answer way down lower. It goes through many possibilities from grubs to fungus.
Sometimes the failure of a septic system isn't necessarily a broken line or ruptured tank.... BUT--- actually the need to recondition the drainage field.
Bro.... get a hazmat suit...