Unsaturated zone monitoring data from a reclaimed uranium mine site, Grand Canyon, USA, 2022-2025

These data are from the reclaimed uranium mine site Kanab North near Grand Canyon National Park in Arizona. We collected data and soil samples within a highly disturbed mine reclamation area and a nearby undisturbed area for comparison. The data set includes measurements of field saturated hydraulic conductivity (Kfs), particle size distributions, lab-measured soil-water content and bulk density from subsurface core samples, and time series data from soil-water content and matric potential probes. Kfs was measured by 2 methods: tension infiltrometer (30 disturbed locations, 21 undisturbed locations) and single ring falling head infiltrometer (28 disturbed locations, 21 undisturbed locations). Using two infiltration methods provides information on water movement through the soil matrix alone as well as combined matrix and macropore flow. We measured infiltration capacity of the soil matrix using mini disk (MD) tension infiltrometers (METER Group*), which are 90 ml-capacity plastic, 2-chamber cylindrical reservoirs. The water is held under tension connected to a 4.5‐cm‐diameter, 3‐mm‐thick sintered stainless-steel disk through which water flows into the soil. Infiltrating water under tension prevents the filling of the macropores and gives a field-saturated hydraulic conductivity (Kfs) characteristic of the soil matrix only. The MD tension, or suction head, was set at 1 cm for all measurements for consistency and comparability to other studies. For simplicity, we used the general calculation method recommended by the instrument manufacturer (METER Group*). We measured the combined infiltration capacity of the soil matrix and macropores using falling-head, single-ring infiltrometers. These metal rings, 10 cm in diameter and 13 cm in length, were pressed into the soil during the measurement interval. The method for calculating the field-saturated hydraulic conductivity (Kfs) accounts for both variable falling head and subsurface radial spreading that unavoidably occurs with small ring size (Nimmo et al. 2009). Continuous soil cores were collected at 7 disturbed (44 samples in total) and 6 undisturbed locations (25 samples in total). Bulk samples were collected at the land surface (0-3”) at 47 locations for particle size analysis. Samples were air-dried, disaggregated using a mortar and pestle, and any coarse fragments greater than 2 mm were removed using a screen mesh. Samples were then split using a stainless-steel sample splitter and a 16-part spinning riffler to achieve a representative sample. We analyzed the samples by optical diffraction (Gee and Or, 2002) using a Beckman-Coulter LS-13-320* Particle Size Analyzer. Standards were run prior to and following batch sample runs to ensure machine accuracy. Soil textural class was determined based on the USDA soil classification and clay, silt, and sand percentage are reported here. Bulk density and field water content were determined from basic weight and volume measurements on the core samples. Time series subsurface probe data are from 6 locations (3 disturbed with 2 depths each and 3 undisturbed with 3 depth each) with collection set at 15-minute time intervals. Water content was measured using model CS655 TDR probes from Campbell Scientific, Inc.* and matric potential was measured using model Teros 21 probes from Meter Group*. *Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Gee, G.W., and Or, D., 2002, Particle-Size Analysis, in Dane, J.H. and Topp, G.C. eds., Methods of Soil Analysis: Part 4--Physical Methods: Soil Science Society of America, Madison, WI, p. 255–293. Nimmo, J.R., Schmidt, K.M., Perkins, K.S., and Stock, J.D., 2009, Rapid Measurement of Field-Saturated Hydraulic Conductivity for Areal Characterization: Vadose Zone Journal, v. 8, no. 1, p. 142-149.