Minnesota Private Wells Study

Arsenic occurs naturally in soil and minerals and is commonly found in groundwater throughout much of Minnesota. The occurrence and distribution of arsenic in groundwater is difficult to predict. Research is steadily increasing our understanding of the mechanisms and geologic conditions that determine arsenic occurrence in groundwater. The arsenic concentration in a new well, measured at the time of construction, is sometimes higher or lower, compared to subsequent sampling results. It is not clear if these results reflect natural processes or may be influenced by well construction and development methods and if the initial sample is truly representative of arsenic for that new well. Accurate well water quality data enables the well owner to better assess health risks and avoid spending money treating well water that may not need special treatment or believing their well water is safe and consuming water with arsenic levels of health concern. For this study, 250 new water supply wells will be sampled three times over the next year for arsenic and other parameters. Wells are chosen based on different well contractors' water sampling protocols for testing well water, as well as factoring in different well development methods. All wells will be located in areas of elevated arsenic. The goals of this study are to: • Analyze different sampling protocols used by well contractors to determine how arsenic concentrations may be affected. • Track any variation in arsenic concentrations for a new well over the year following construction.