Conceptual Models of Flow through a Heterogeneous, Layered Vadose Zone under a Percolation Pond

摘要: Understanding how water and solutes move through the vadose zone is necessary to make effective remedial action decisions where contaminants were spilled or leaked at ground surface buried in shallow land-disposal sites. In layered, heterogeneous systems, high contrasts hydraulic conductivity can lead formation of perched zones, enhanced lateral spread contamination. Two conceptual models are considered solute for migration zone. diffuse flow model, zones accumulate until head over perching layer becomes sufficient drive infiltration layer. preferential moves laterally a path around encountered. Preferential paths enhance contaminant because greater moisture saturation leads higher advective velocities, bypass low permeability layers with sorption capacity. Monitoring wells instrumented boreholes installed newly constructed industrial-waste percolation pond an ephemeral river that lie 150-m-thick layered Background data gathered before discharge began show presence least one, possibly two, deep zones. The shallower zone, approximately 45-m below land (bls), extends 800-m south vicinity pond. There deeper 90-m bls, southeast pond, direction away from river. last contained May 2000, two years collection summer 2002. significant implications this (1) persists several absence recharge, (2) on order kilometer Hydrological collected analyzed since October 2002 indicate degree spatial variability within subsurface, resulting directional southern cell northern north cell. Water arrival was observed locations ones, transport not only basalt/interbed interfaces but also thick basalt layers. Recharge as 87-m bls far Big Lost River 860-m north. New formed first alluvium/basalt interface end after lithologic monitoring completed northern, southern, western perimeter found be most prevalent type Vadose Zone Research Park, contrast current INEEL model adopts predictions.