What you need --
1 - metal trashcan lid
1 - hanging basket bowl/container, hanging apparatus removed
1 - energetic 12 yr old
Set the trashcan lid on the hanging basket bowl/lid in the middle of the yard between vegetable garden and the back fence and fill with water as a birdbath. **Wobbly/unstable base is the KEY**
When you see the groundHOG loitering near the vegetable garden, send the 12 yr old out to sneak up on it and chase it towards the birdbath.
If successful, the groundHOG will trip over the birdbath, ending up with the lid flipping over and dumping it with water, then in confusion and panic, be unable to remember how to get out of the yard while the 12 yr old closes in on it. By the time it finally makes it out, it would have been thoroughly rattled.
Day 4 and still no show.
p.s. Be prepared to console the 12 yr old -- she kept saying "The poor thing! I'm worried that it might get sick! it got completely drenched. Do you think it will be OK?". Practice saying with straight face: "Oh it'll be fine."