I think water quality is the realm of DEQ (Dep't of Environmental Quality) in Oklahoma. They do water well testing, and when they were talking about building a power plant that would be running gray water piping through the Garber-Wellington aquifer in Norman, part of their permitting process involved a hearing before DEQ.If you’re concerned about ground water contamination, the county health or OCC should be able to help you out.
Drilling is usually easy or almost impossible.
FWIW, you'll want to talk to local water well drillers, as they'll know the land and geology, so they'll know location-based info like where there's no point in trying to sink a well. (I know someone in that boat--the most highly-recommended driller was the one who said he wouldn't waste the guy's time or money trying to sink a well, as he'd tried that area before, and they just couldn't get good enough results.)