Although Groundhogs, Woodchucks, are burrowers they do not make tunnels, so if what you have are tunnels yiu probably have a mole. If you are to use a smoke bomb to control a Groundhog you will need to find its burrow, home. and use that smoke bomb while the animal is in.
Live trapping may be an option, if Ontario allows you to transport the critter somplace else.

Here is a link that might be useful: About Groundhogs

They are, indeed groundhogs. I've seen them. I've had moles and voles too, but it's the groundhogs that are destroying my field. Groundhogs build mounds that one of them will sit on and watch for predators. Because a groundhog's den has multiple entrances, It's my intent to find each and every exit, and place traps at every one of them. I want these groundhogs gone. Does anyone know how to make a smoke stick?

I don't know how to make a smoke stick but we had trouble with groundhogs last year and we removed a family of them by dumping very soapy water into each hole (about a bucket full). Apparently they don't like the soap and they abandon the hole then move on.

Hi mrsbeasley~I'm an expert in getting rid of groundhogs, I hunt them all the time! (for farmers, near buildings and livestock too) I do most of this in SW Ontario, NW of Arthur. (roughly) I don't charge for this, and would be happy to discuss it further with you if you'd like to email me. If you're in a built-up area, you might need to resort to an alternative solution, but if you're in the country, I might be able to help.

Please email me hipwader@sympatico.ca Thanks!