I find these all the time in the summer in Nova Scotia. They usually hang out in the grass or under planks of wood. Usually I don't bother them, but sometimes I'll take one home for a while, and give them a mite & tick bath. They dont do well in cativity...I try feeding them a couple slugs or earthworms (to fatten them up before letting them go) and some eat, but many don't. Those I let go right away. The ones that eat I keep for a while.
I'm usually not in N.S. when the time comes for them to give birth, but when I am I'll keep any gravid females until they lay. The babies usually eat well and once they are well established I let them go. Figure they have a better chance at survival if they are a month old
All in all very fun little snakes, great to work with if you dont count on the WC ones eating.
BTW, if you find any smooth green snakes, there are probably some red-bellied snakes closeby! They are real small and hard to see, so I often set up little areas for them, with some moss, planks of wood, etc in a crate or something. I find them a lot in there.. along with black rats, greens, ring necks, you name it.