The Minnesota Department of Health is reminding rural residents during National Groundwater Awareness Week that regular testing is the only way to know if private well water is safe. Health officials say common contaminants in Minnesota wells include nitrate, coliform bacteria, arsenic, lead and manganese—most of which can’t be seen, smelled or tasted. With many homes in northwestern Minnesota relying on private wells, the state recommends testing for bacteria and nitrate every year to protect drinking water.