Wells

Source: adapted from Manual of Individual Water Supply Systems,
EPA-430/9-74-007, U.S. Environmental Protection Agency

Any well provides a conduit from the land surface directly to groundwater. Polluted surface water may enter the well and move rapidly to the underlying aquifer, contaminating groundwater. Because the well borehole may penetrate several aquifers, if a polluted aquifer lies above an unpolluted one, water from the polluted aquifer may drain through the well and contaminate the aquifer that lies below. Abandoned wells should be filled (with cement grout or clay) in such a way as to prevent water movement within the borehole and groundwater pollution. Active wells should be properly located and grouted. (See well construction section. Procedures vary with specific site conditions.)