Which is least likely to be impacted by runoff from a factory?

Groundwater

Groundwater flows through rock with a high porosity and a high permeability at a fast rate. The denser and less permeable  the rock is, the slower the groundwater moves. The greater the permeability of a rock, the faster the groundwater flows through it. Groundwater is water that is found in spaces and fractures in rocks, as well as in the sediment between the earth's surface.