Geochemical data, water-level data, and slug test analysis results from till confining units and confined aquifers in glacial deposits near Akeley, Cromwell, Litchfield, and Olivia, Minnesota, 2015-2018

Confined (or buried) aquifers overlain by till confining units are used to supply drinking water to millions of people. Till confining units are typically conceptualized as having very low potential for transmitting water. Thus, buried aquifers are thought to be less susceptible to surface contamination, but may recharge very slowly and may be prone to unsustainable groundwater withdrawals. Quantification of the recharge (leakage) rate through till is essential to understanding the long-term sustainability of groundwater withdrawals from buried aquifers and yet few data exist on the hydraulic properties of till and groundwater flux through till. The information contained in this data release is generated from field sample and data collection at four representative sites in Minnesota with high-capacity pumping wells in confined aquifers underlying glacial till. The field sites were near the cities of Akeley, Cromwell, Litchfield, and Olivia, Minnesota. Two general categories of data are available with this data release: (1) geochemical data from groundwater, pore water, and glacial sediments and (2) water-level data and analytical results for slug tests. Samples for geochemical analyses were collected from wells (or piezometers) and geologic cores. Slug tests were done in 1.25-inch or 2-inch wells (or piezometers) screened in aquifer sediments or till confining units. This data release contains data that could not be published in the USGS National Water Information System (NWIS) database; additional water-quality and water-level data are available for this study through NWIS. An R script is included in this data release that downloads the NWIS data for the sites in this study, and the primary publication has a list of sites that can be used for retrieving data from NWIS.