Los Alamos National Laboratory (LANL or the Laboratory) and the New Mexico Environment Department (NMED) are in the midst of a two-year project to investigate the sources, flow paths, flow velocities and mixing of groundwater in the vicinity of LANL from groundwater geochemical and isotopic data. Central to this investigation are groundwater carbon-14 (¹⁴C) data collected by the NMED from over 80 springs and wells in the LANL area. These data are being used to calculate groundwater travel times and residence times in the underlying regional aquifer. To sort out the relative impacts of water/rock interactions, groundwater mixing, and radioactive decay on the groundwater ¹⁴C activities, groundwater ¹⁴C data are being examined in conjunction with other groundwater geochemical and isotopic data from the study area.  These supporting data can help provide evidence of the source of the groundwater and its history of water/rock interaction, and thus aide in the interpretation of the ¹⁴C data.

Ongoing analyses suggest that only deep groundwater from the regional aquifer production wells and groundwater from some springs on the east side of the Rio Grande have undergone significant interactions with calcite. Based on their uncorrected ages, most of the groundwater in the regional aquifer appears to have a residence time of between 2,500 and 7,500 years, except for deep groundwater from production wells near the Rio Grande, where the apparent groundwater residence times exceed 10,000 years. However, even this groundwater may be younger than 10,000 years based on the age corrections using DIC and δ¹³C. Scatter plots and maps of the supporting geochemical data are being used to formulate conceptual and numerical geochemical models to calculate travel times in the regional aquifer.