Identifying and Mapping Areas at Risk for Private Well Water Contamination

BACKGROUND: Approximately 15% of the U.S. population relies on private domestic water sources for drinking water.  These sources may be susceptible to more frequent contamination and higher contaminant levels than in community water supplies.   Despite the significance of this threat, private water sources (mostly wells) are largely unregulated in the U.S. and monitoring is almost always the responsibility of the home owner.  States vary considerably in the availability of, access to, and organization of private water source data.  Several states that are part of the National Environmental Public Health Tracking (EPHT) program developed recommendations for measures of private water quality for specific contaminants of widespread concern (arsenic and nitrate).  The purpose of this presentation is to report on the efforts of nine EPHT states to compile data sets on private well water quality and to create and display maps of vulnerable areas in their jurisdictions at meaningful geographic scales.   

METHODS: Communication among the participating states was primarily via teleconferences, webinars and file sharing.  Initially, the participating states assessed the availability, geographic  coverage, time period and completeness of private water source data, and determined whether private well data could be summarized at county or sub-county geographic scales.  States also considered use cases, potential data users, and existing EPHT portal mapping and graphics tools to inform the design of state-specific displays and accompanying  messages.

RESULTS: States prepared data sets when possible, and some were able to create state-wide vulnerability maps based on existing private well water data.  One state without access to actual well data used a modeled vulnerability map based on geologic characteristics and limited groundwater data.  The presentation will show private well vulnerability maps for arsenic and nitrate from participating states.  Limited user testing in some states helped to refine the content of maps and graphics for all participants.  Some state participants were able to integrate private well information onto their existing EPHT portals together with appropriate public health messaging.

CONCLUSIONS: Participating states improved the availability and organization of private well water data.  Some developed maps showing geographic variation in private well contaminant vulnerability, using consistent metrics, and to display maps and public health messages on EPHT portals.    These efforts will assist public health practitioners at the state and local level to identify geographic areas of higher risk of contamination and to target outreach efforts to home owners to test and take action to reduce exposures to contaminants of concern.