Laboratory Measurements of the Unsaturated Hydraulic Properties at the Vadose Zone Transport Field Study Site

Abstract

This report presents sampling and measurement procedures and measurement results for 60 samples from the S-1, S-2, and S-3 bore holes at the Vadose Zone Transport Field Study Leak Simulation Test Site, located at the Sisson and Lu (1984) injection site in the 200 East Area of the Hanford Site. Measured data include particle size distributions (19 points), bulk densities (and bulk density-derived porosity), water retention characteristics (16 static points), and saturated and unsaturated hydraulic conductivities. The coring and sub-sampling procedures led to partially, and occasionally completely, disturbed samples. Textural analyses showed that most of the samples could be classified as sand, some as loamy sands, and two as sandy loams. The multi-step outflow method failed for seven samples, yielding 53 samples for which hydraulic parameters were available. Van Genuchten and Brooks-Corey water retention parameters were determined using static retention points (derived from multi-step outflow time series). Inverse analyses of the multi-step outflow data yielded additional unsaturated hydraulic conductivity parameters. Unfortunately, the inverse analyses had some problems in reaching stable solutions. Therefore, we sometimes fixed saturated and residual water contents and saturated hydraulic conductivities at initial values. Even then, it was not possible to reach a solution for two samplesmore » leaving the total number of samples for which inverse solutions were available at 51. We also noticed that Brooks-Corey inversions were of lesser quality than van Genuchten inversions. We suggest that Brooks-Corey inversions be treated carefully and that, where possible, the far more reliable direct fits of the Brooks-Corey curve to the static retention data be used. The data gathered in this effort are for the most part reported in the appendix. Raw, outflow time series data from the multi-step outflow procedure are not included. An electronic version of the data is available from the first and third authors.« less