Trailing off

I've been doing a lot of walking/hiking lately. My good friend told me about an opportunity up here in the neighborhood-the trail conference up here was csting about for Trail Maintenance people on a newly-cut trail up here in Jenny Jump State forest/park. There was a 7 mile orientation hike yesterday and I'm thinking of joining up either as a Crew member (to build water dams, stone steps, clear major passageways along the trail) or a TM (trail maintenance person), clearing branches and cutting overgrown foliage to keep the site clear (and bramble-free). I certainly have enough experience to handle the latter, after "cutting line" on my brief surveying stint. Just please pass me that machete, please!
What I'm thinking is that I'd like to include Johnny, but dunno about having him roam the woods while I'm working-I'm nervous about him taking off, like he did that one time. At this point, I'd be lost without him: we've grown very attached since early December. Needless to say, we've both been through a lot since that time. Can you hire someone to train your dog to never leave your side? Guess I might as well ask about a relationship that will never lose its fervor...Mary, from whom I adopted Johnny, says that there is no sure way to have a dog like this-that they have their own minds and may or may not return... that there is always that possibility that you'll never see that dog again. I'm torn between not doing this trail thing if it means taking away from my time with the dog (each of my days are a week's worth-in dog life-to him)and taking him and letting fate decide if we are meant to be together forever. As someone who never had any good off-leash experience, this is a hard choice.