Nitrogen-fixing bacteria in soil can convert excess nitrogen into , which can contaminate groundwater. A/An forms around a well when the water table begins to slope toward the well. The water in an artesian well comes from a/an aquifer. A well not only has to reach the but also has to go deeper. aquifers are more prone to pollution. The two primary components of a septic system are a septic tank and a/an . Groundwater that comes to the surface naturally is known as a/an .