Application of the Monte Carlo simulation procedure to estimate water-supply well/septic tank-drainfield separation distances in the Central Wisconsin sand plain

• Published in: Journal of contaminant hydrology 1991, Vol.8 (1), p.91-109
• Main Authors: Harmsen, Eric W., Converse, James C., Anderson, Mary P.
• Format: Article
• Language: English
• Subjects: Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Exact sciences and technology; Freshwater; Geochemistry; Mineralogy; Pollution, environment geology; Silicates; Water geochemistry
• ISSN: 0169-7722; 1873-6009
• DOI: 10.1016/0169-7722(91)90010-X

Using a three-dimensional groundwater-contaminant tracking model a number of Monte-Carlo simulations were performed to estimate the mean and standard deviations of the separation distances and minimum well depth required to avoid contamination of a pumping water-supply well by a nearby septic tank-drainfield. The range of conditions simulated represent those found in the Central Wisconsin sand plain. A sensitivity analysis revealed that the separation distances and minimum well depth are most sensitive to variations in the horizontal hydraulic conductivity, anisotropy ratio and horizontal regional hydraulic gradient. The mean and standard deviations of the theoretical safe separation distances and safe well depth are presented as contour diagrams that can be used for design purposes. An example is given for which the design separation distances and minimum well depth are determined for a hypothetical subdivision in the Central Wisconsin sand plain.