Using Groundwater Models to Evaluate Strategies for Drinking-Water Protection in Rural Subdivisions

Problem: Groundwater contamination is a concern in rural residential subdivisions where numerous septic systems and private wells are sited in close proximity. Although most state codes regulate the construction and location of private wells, these regulations do not usually account for site-specific conditions that may impact drinking-water quality. Purpose: Groundwater models provide a technical basis for delineating groundwater flow to domestic wells. Despite their widespread use in the hydrologic sciences, planners and developers rarely have access to such models. We aimed to assess existing regulations for domestic wells and septic systems and illustrate how groundwater models can be used to evaluate strategies for additional drinking-water protection in unsewered residential subdivisions. Methods: We developed groundwater flow models for two subdivisions in southern Wisconsin, analyzed the results, and disseminated them to local officials, developers, and residents. Results and conclusions: Models of both subdivisions indicate that deeper individual wells or a single community well within a protected source area would improve the likelihood of obtaining high-quality drinking water. In response, several homeowners in one subdivision chose to pay for deeper wells and well casings or individual home water-treatment systems. The developer of the second site incorporated an unenforceable recommendation for deeper well casings into subdivision covenants, but none of the wells drilled so far have followed the recommendation. Implementing and enforcing well construction or setback criteria based on model results may require changing Wisconsin state codes to explicitly define what can and cannot be regulated at the local level. Takeaway for practice: Hydrogeologists can use standard groundwater modeling methods and information about local hydrologic conditions to inform planners as they develop guidelines to improve drinking-water quality. Partnerships between local hydrogeologists and planners are essential because differences in hydrogeologic setting, groundwater quality concerns, and regulatory structure will cause model results and proposed guidelines to vary on a case-by-case basis. Research support: Funding for this research was provided by the EPA Science to Achieve Results (STAR) graduate fellowship program, the University of Wisconsin Groundwater Resources Advisory Council (administered by the Wisconsin Water Resources Institute), and the Wisconsin Department of Natural Resources.