There have been some studies that confirm that Amdro probably does not release the active ingredient into leachate. That being said, I believe that I would be hesitant to use it near my well, just as you are.

However, there is an organic (as in Certified Organic) ant bait that you can find, which the active ingredient Spinosad. Several companies are now manufacturing their own brand name using this ingredient....so you might want to Google ' Spinosad Ant Baits' to get some names. Or just be a good label reader.

I don't mind ants in my yard, for the most part, but wouldn't hesitate to get rid of them if they were making large mounds. That can be damaging to root systems. I also don't welcome fire ants!

You have little concern about contaminating your well with what you put on your soil although what you put down will affect someone elses water, unless you well is only 10 feet down. What others upstream of you dump on their lawns and gardens will affect what is in your water as that stuff works its way through the soil and into the aquifer.
Ants are part of Ma Natures recycling machine, a necessary and essential part of our world, except in our houses, and they are not pests, except in our houses. There is no good reason to put down a poison unless what you have are the Fire Ants.