Your mountain daycare didn’t end well–mistakes were made an…

Your mountain daycare didn’t end well–mistakes were made and we’ll leave it at that.  Having learned to avoid places prone to landslides, you’ve decided to name your new daycare “Farm Babies” and have acquired very flat land right next to an enormous commercial pig farm that stores the pig offal in large, unlined ponds.  Given that the daycare is far from any cities, the only available water is well water (i.e., groundwater).  Knowing that, what type of groundwater source would be best?