Tonight, PNM continues our discussion of Madison’s water. Lincoln Tice talks with UW-Madison hydrogeologist Ken Bradbury about where Madison gets its water. That would be the groundwater. Madison is lucky to have two layers of groundwater with a layer of shale to help filtration for the lower groundwater. But, our groundwater isn’t safe from potential threats like road salt in the winter. Then, nitrate from fertilizer can also pollute the groundwater. And, another threat appears to be viruses, that Ken has been studying at the Wisconsin Geological and Natural History Survey. Viruses need a human host to multiply, but some may be able to survive and be transported in groundwater.