Open AccessKilometer‐Scale Rapid Transport of Naphthalene Sulfonate Tracer in the Unsaturated Zone at the Idaho National Engineering and Environmental Laboratory
Author(s) -
Nimmo John R.,
Perkins Kim S.,
Rose Peter E.,
Rousseau Joseph P.,
Orr Bren R.,
Twining Brian V.,
Anderson Steven R.
Publication year - 2002
Publication title -
vadose zone journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.036
H-Index - 81
ISSN - 1539-1663
DOI - 10.2136/vzj2002.8900
Subject(s) - vadose zone , aquifer , geology , lava , tracer , infiltration (hvac) , hydrology (agriculture) , groundwater , water table , rubble , basalt , subsurface flow , geochemistry , geomorphology , volcano , geotechnical engineering , physics , nuclear physics , thermodynamics
To investigate possible long‐range flow paths through the interbedded basalts and sediments of a 200‐m‐thick unsaturated zone, we applied a chemical tracer to seasonally filled infiltration ponds on the Snake River Plain in Idaho. This site is near the Subsurface Disposal Area for radioactive and other hazardous waste at the Idaho National Engineering and Environmental Laboratory. Within 4 mo, we detected tracer in one of 13 sampled aquifer wells, and in eight of 11 sampled perched‐water wells as far as 1.3 km away. These detections show that (i) low‐permeability layers in the unsaturated zone divert some flow horizontally, but do not prevent rapid transport to the aquifer; (ii) horizontal convective transport rates within the unsaturated zone may exceed 14 m d −1 , perhaps through essentially saturated basalt fractures, tension cracks, lava tubes, or rubble zones; and (iii) some perched water beneath the Subsurface Disposal Area derives from episodic surface water more than 1 km away. Such rapid and far‐reaching flow may be common throughout the Snake River Plain, and possibly occurs in other locations that have a geologically complex unsaturated zone and comparable sources of infiltrating water.