The occurrence of arsenic in groundwater in parts of Northeast Wisconsin was first identified in 1987 during a routine feasibility study for a proposed landfill location in the town of Vinland, Winnebago County, and has been an ongoing problem since that discovery.

This project was designed to investigate the extent and source of radium contamination in the Cambro-Ordovician aquifer system of eastern Wisconsin.

The Maquoketa Formation, a dolomitic shale, forms the most important aquitard in eastern Wisconsin, USA, isolating the water-table and Silurian aquifers from the underlying Cambrian-Ordovician aquifer.

Carbonate aquifers form important regional sources of drinking water in eastern and southern Wisconsin. Previous work in Door County suggests that vertical fractures as well as horizontal partings and dissolution zones provide the primary pathways for groundwater flow

Inorganic arsenic is a well-known human poison that causes a wide array of adverse health effects. The World Health Organization and U.S. Environmental Protection Agency classify inorganic arsenic as a human carcinogen.

Concentrations of arsenic, ranging from 1.0 to 12000 micrograms per liter (ug/L), were detected in groundwater over a broad geographic region in Outagamie and Winnebago Counties in Wisconsin.