Interpreting INEEL Vadose Zone Water Movement on the Basis of Large‐Scale Field Tests and Long‐Term Vadose Zone Monitoring Results

Abstract

A review of the results from two large‐scale field tests and vadose zone monitoring data at two facilities at the Idaho National Engineering and Environmental Laboratory (INEEL) has provided information to support development of a conceptual model of water movement in the highly heterogeneous vadose zone beneath two INEEL facilities. Both of the large‐scale field tests were ponded water infiltration tests that approached the size of the two facilities. An assembly of perched water wells, neutron access tubes, and tensiometers have been used to monitor water movement beneath these sites. Once water has percolated through the surficial sediment at these facilities, the presence of the surficial sediment–basalt interface results in some perching of the percolated water with limited lateral movement. Water movement in basalt formations is mainly gravity‐dominated in preferential fracture pathways and rubble zones and results in rapid vertical flow especially frequently under conditions of positive hydrostatic head. Detection of wetting front advance is typically not sequential with depth and has been shown to vary between episodic infiltration events. At the basalt–sediment interface of the interbeds, perched water is often detected and has resulted in more lateral spreading of recharge than at the surficial sediment–basalt interface. Gaps in the sedimentary interbeds will allow some of the recharge water to bypass the interbeds and rapidly continue toward the aquifer. This complex water movement in the vadose zone beneath the INEEL supports the need to control surface infiltration, identify gaps and the lateral continuity of the interbeds, and investigate the influence of nearby surface water sources on perched water movement beneath these two facilities.

SCIMPI: A New Seafloor Observatory System

“…For example, data have been continuously collected since January 2002 from dozens of ARA' s CPT-deployed soil moisture-resistivity-temperature probes installed in a nuclear waste burial ground at Idaho National Engineering and Environmental Laboratory [22]. This harsh environment exposes the probes to radioactivity, organic solvents, and extreme pH conditions.…”

Soil column experiments to quantify vadose zone water fluxes in arid settings

“…Recently, efforts have been made to better understand and quantify processes within the vadose zone that determine water fluxes by improved measurement techniques of water content (e.g., Dahan et al 2003;Jones et al 2005), observation of different scale phenomena (e.g., Hendrickx and Flury 2001;Mattson et al 2004;Hopmans and Schoups 2005) and enhanced numerical modeling (e.g., Dong et al 2003;Saito et al 2006;Sakai et al 2009). Benchscale laboratory experiments can greatly support these efforts by simulating and investigating processes that occur in the field under controlled initial and boundary conditions (Oostrom et al 2005).…”