Sampling of Borehole WL-3A through -12 in Support of the Vadose Zone Transport Field Study

Abstract

SummaryThis report presents the results of the fiscal year (FY) 2001 core sampling effort conducted to support the Vadose Zone Transport Field Study (VZTFS). The VZTFS has been conducting a series of controlled near-surface tracer tests at the 299-E24-111 Experiment Test-Well Site (also known as the Sisson and Lu site). The purpose of these tests is to address principal uncertainties affecting the understanding of current contaminant distributions under Hanford waste sites, and to improve the prediction of future migration through the vadose zone (Ward and Gee 2000). The FY 2001 tests were conducted using a concentrated sodium thiosulfate tracer (Ward and Gee 2001). Subsurface monitoring of the tracer test was conducted using various geophysical and geochemical methods.This report presents the results from ten soil borings installed before, during, and after the tracer was injected. The first two soil borings were sampled seven days prior to the initiation of the tracer injections. Two more soil borings were sampled midway during the series of injections, and the remaining six soil borings were installed at three different times after the cessation of the injections. Over 300 soil samples were collected using a cone penetrometer and wireline sampling tools. The samples generally ranged in depth from 4.6 to 17.4 m (15 to 57 ft). Selected samples were analyzed for percent fines, moisture content, and/or tracer concentrations.Preliminary results from the core sample analyses indicate that the major concentration front of the thiosulfate tracer reached a relative depth of at least 5.5 m (18 ft) below the injection point 17 days after the tracer injections began. Fifty-one days later the tracer appears to have migrated to a relative depth of at least 12.3 m (40.5 ft). Lateral spreading appears to have exceeded 5.8 m (19 ft) even at these deepest points of migration. These data will be used in combination with other geophysical and geochemical results to further our understanding of contaminant transport within the vadose zone.v

Simulating field‐scale moisture flow using a combined power‐averaging and tensorial connectivity‐tortuosity approach

“…[12] Lithostratigraphy at the S&L site was characterized by drilling using a cone penetrometer and wireline sampling [Last et al, 2001]. The vertical heterogeneity at the S&L site was evaluated by visual inspection of the strata, which were classified into five units, which are labeled B through F [Last et al 2001] and shown in Figure 1b. The hydraulic properties at the core scale were from two sources [Schaap et al, 2003;Khaleel et al, 1995].…”