How deep is your well? I don't use anything chemical, but I personally wouldn't take the chance. I'm not sure what studies show or what the recommended advice is. My well isn't that deep and I'm on a hillside so I'm a bit susceptible to what people up the hill on my side of the street do too. Given it's redneckville a few houses up I think most of the drainage down my hill has a bigger risk of contamination from rusted out garbage in the yard rather than lawn fertilizers. lol