Chip,
[EDIT: You posted just before I posted -- but here is one more solution if your's doesn't work. As they say in the fine print, please remember, it can be dangerous.]For over 25 years I've used a variation of EWEST's method.
As EWSET said -- please wait until after dark. They settle in around dusk, and aren't much of a danger at night.
Find the hole, and pour in about a half-cup of diesel fuel or kerosene. Wet a paper towel with the same oil, and place it at the top of the hole. Light another dry paper towel, or a piece of newspaper, and drop in on the hole. It will gently burn for 15-30 minutes. It will suck all the oxygen out of the hole.
I've never seen them come back within about 50 feet of a hole that has been burned out.
NOTE: Through very painful experience, I've learned to squat and look before I mow or weed whack. From early August, well into October, I look for any activity over the whole area I'm about to mow, weed whack, or brush hog. Sometimes I'm lucky and I find a nest before it finds me.
Good luck,
Ken
