radioactivity of in ground uranium

Some one can correct me if I am wrong and I am no expert, but my information is that uranium in its natural state in sandstone is less radioactive than granite. Water has been leaching through these sandstone layers into the local water table since rain first fell. I don't see how drilling a hole through this sand stone can suddenly make the ground water radioactive. My information is that the problems occur when the mining and treatment processes begin and this is where worlds best practice mining methods need to be employed to prevent damage to the local environment. Maybe someone out there can throw light on this from a qualified perspective. It would be good if those comments were not written by raving greenies looking to stop all mining at all costs or greedy mining moguls looking for a quick profit. Something balanced and researched would be good.