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SEPTIC TANK SETBACK DISTANCES: A WAY TO MINIMIZE VIRUS CONTAMINATION OF DRINKING WATER
Citation:
Yates, M. AND S. Yates. SEPTIC TANK SETBACK DISTANCES: A WAY TO MINIMIZE VIRUS CONTAMINATION OF DRINKING WATER. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-89/126.
Description:
Septic tanks are the most frequently reported causes of contamination in groundwater disease outbreaks associated with the consumption of untreated ground water in the United States. he placement of septic tanks is generally controlled by country-wide or state-wide regulations with little consideration given to the local hydrogeologic, climatic, and land-use conditions. sing the travel time necessary to achieve a seven-order-of-magnitude reduction in virus number as the criterion, a wide range of septic tank setback distances (from less than 15 m to greater than 300 m) were calculated for a part of the Tucson Basin. his study makes use of disjunctive kriging to calculate the conditional probabilites associated with the setback distance estimates. he results are presented in two different ways: first, given a setback distance (e.g., prescribed by law) the probabilities that the level of viruses will be within acceptable limits are calculated; and second, the desired probability level is specified (e.g., 90%) and the setback distances required to achieve that level of confidence that the water will be free of virus contamination are calculated. he methods have potential for use by local government officials for land-use planning purposes.