Safe distance from river to put a well

I will be drilling a well next to a river. Is there a minimally accepted "safe" distance to drill next to a clean/unpolluted river to ensure that there is enough filtration to remove pathogens and the like? I will be having the water tested before using it but I'd just like a general idea of "do not drill within 50 feet of the river" or some such. If it makes any difference: the water table at this location is roughly 20' below the ground.

Thanks a lot for your info.

What are the state regulations about drilling close to a river?

Normally once the casing is set into competant bedrock there are no issues.

You could talk to Loyd Watson, Watson Water in Lascassas, Tn.

This is the only thing I see in the water well standards for AL regarding location:

335-9-1-.04 Location Standards. Every well shall be located so that it is
easily accessible, free from flooding from any known source of pollution. The
location of the well shall comply with local regulations. The following table is
recommended:
Projections or roofs of adjacent building 2 Feet
Secondary electrical services 10 Feet
Primary electrical services 75 Feet
Cess pool or sewage lagoon 150 Feet
Septic tank or field lines 100 Feet
Barnyard 150 Feet