Unsaturated zone soil properties near a dry well and Four-plex baseball field, Fort Irwin National Training Center, San Bernardino County, California, 2019-2020

The U.S. Army Fort Irwin National Training Center (NTC), approximately 35 miles north-northeast of Barstow, California, obtains all of its potable water supply from three groundwater basins (Irwin, Langford, and Bicycle Basins) within the NTC boundaries. In these basins, groundwater withdrawals exceed natural recharge, resulting in water-level declines. However, managed aquifer recharge using recycled water (treated wastewater) has offset water-level declines in Irwin Basin. Additionally, localized water-quality changes have occurred in some parts of Irwin Basin as a result of human activities (for example, wastewater disposal practices, landscape irrigation, and (or) leaking pipes). As part of a research study in cooperation with the U.S. Environmental Protection Agency (EPA) and the U.S. Army, the U.S. Geological Survey (USGS) evaluated unsaturated zone soil property data of cores from a borehole for a newly drilled monitoring well near a dry well and irrigated Four-plex baseball field. Measurements and observations are presented for cores from an initial drilling attempt (site ESW2A), which stopped at 85 feet below land surface due to equipment issues, and data are presented for cores from the successful drilling attempt (ESW2B) down to 240 feet below land surface. The two boreholes are located approximately 6 feet from each other. The grain size measurements were compared to a reference sample HMR2 collected as part of a previous study near Barstow.