Contaminants in the Glacial Aquifer Drinking Water System

Approximately one-sixth of the United States population, or 41 million people, relied on the glacial aquifer system for drinking water in 2005. However, untreated water from one in five drinking water wells in this aquifer, sampled as part of the USGS National Water Quality Assessment Program, exceeded a human-health benchmark for at least one contaminant. Contaminants derived from natural sources are more common and more frequently exceed human-health benchmarks than contaminants derived from the land surface. The types of contaminants and the likelihood of encountering them in untreated drinking water from the glacial aquifer system involves trade-offs that depend on a complex interplay of sources of water to wells from various parts of the hydrologic system.