Q.wisteria
If I treat wisteria with an herbicide like Roundup, will it leach into a well system that we use for our drinking water? If so, how far away should the well system be for safety?

If you are trying to control or kill off the Wisteria, cutting the plant down and painting the cut ends with a herbicide instead of spraying the plant.
Here are some links with more information.
https://www.gardeningknowhow.com/ornamental/vines/wisteria/controlling-or-getting-rid-of-wisteria.htm
https://www.gardeningknowhow.com/plant-problems/weeds/using-herbicide-in-gardens.htm
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/how-long-does-weed-killer-last-in-the-soil.htm