We used to gas gophers. Hook a hose up to your exhaust on your pickup and other end of hose in the hole. Let er idle about 5 minutes or so. Never tried it on a woodchuck but it might work if you throw a few rocks in with the hose in case he tries to get out..
I use a victor mink trap to catch ground squirrels. One got locked in my shed one time when I closed it up-didn't know he was in there till a few days later-chewed extension cords, knocked over oil cans and generally made one :censored: mess. So after that I was on a mission to keep the little fellers eliminated from the area. Couldn't get the wiley ones so I drilled a pecan nut and wired it to the pedestal(trigger) of one of my victor traps. Got him then. Then I'd just walk up and shoot the critter. Works for the wiley critters although if you have other animals around might not be a good idea.
Bullets are cheap, hone your skills at the same time
opcorn: