Intensive private drinking water well sampling in Carroll County, Iowa, will be conducted in 2007 – 2008 as part of the Comprehensive Assessment of Rural Health in Iowa (CARHI) project. This sampling will be a cooperative effort with the ongoing Iowa Statewide Rural Well Water Survey Phase 2 (SWRL2), a three year project (2006-08) conducted by CHEEC in collaboration with the Iowa County Health Departments and County sanitarians, the Iowa Departments of Public Health and Natural Resources, and other agencies. The intensive sampling effort in Carroll County will include 50 wells for the entire suite of SWRL2 compounds (nutrients, bacteria, metals, pesticides and herbicide degradates). Research questions of interest for this set of wells include are there seasonal variation for certain analytes in a confined geographic area (county), and what are the risk factors related to well characteristics/proximate sources of contaminants for poor water quality? An additional 100 wells will sampled and analyzed for total coliform bacteria, E. coli, enterococci, somatic coliphage, and chloride, as part of a special microbial monitoring study conducted by the University Hygienic Laboratory. The research objectives of the microbial monitoring study are to determine the incidence of enterovirus in private drinking water wells, to determine the occurrence of traditional and non-traditional fecal indicators in groundwater (e.g. somatic coliphage, chloride, and enterococci), and to determine whether the source of fecal pollution is human (by utilizing a human specific molecular marker).