as waste discharged from an upstream community. In many areas of the country, septic wastes from rural onsite liquid waste disposal systems constitute a major source of ground water recharge. Septic tanks and cesspools rank highest among all wastewater systems in total volume of wastewater discharged directly to ground water (more than a trillion gallons per year) and are the most frequently reported sources of fecal bacteria and toxic chemical contamination. It is said that a few feet of soil between the disposal excavation and the ground water table are sufficient to cleanse the sewage effluent. However, the cumulative effects of inadequately treated sewage on local and regional ground water quality are potentially much more serious than the effects of surface water pollution. The goal of proper onsite liquid waste disposal practices is both to prevent disease and to provide future genera- ONSITE WASTEWATER DISPOSAL tions with ground water that can be used without extensive and expensive treatment. Periodic publications such as the Journal of the American Water Works Association and the Journal of Environmental Health have described a number of disease incidents associated with onsite waste disposal systems. In Richmond Heights, Florida, a church and day-care center septic tank contaminated a drinking water well 150 ft away. Twelve hundred people contracted gastroenteritis. In Polk County, Arkansas, the well of a general store became contami- nated by septic tank effluent. Ice made from the well water trans- mitted viral hepatitis. In Yakima, Washington, typhoid fever was spread by wells contaminated by the septic system of a typhoid carrier. There are other instances throughout Europe and America where long-term biological and chemical contamination of ground water has resulted from onsite wastewater disposal. People tend to dispose of their wastes into their neighbor's drink- ing water supply, whether surface or subsurface. Since the dilution factor is often relatively small for discharges into surface waters