Hinchee, R.E., P.R. Dahlen, P.C. Johnson, and D.R. Burris.
Groundwater Monitoring & Remediation [Published online 11 Jan 2018 prior to print]

Although some 1,4-dioxane can be removed from vadose zone pore water by conventional soil vapor extraction (SVE), remediation is typically inefficient. SVE efficiency is hindered by low Henry's Law constants at ambient temperature and redistribution to vadose pore water if SVE wells pull dioxane vapors across previously clean soil. Based on the hypothesis that heated air injection and more focused SVE extraction (XSVE) could increase the efficiency of dioxane removal from the vadose zone, a new process was pilot tested at the former McClellan Air Force Base, where the four peripheral heated air injection wells of the XSVE system surrounded a 6.1 m x 6.1 m x 9.1 m deep treatment zone with a central vapor extraction well. Soil temperatures reached as high as ~90°C near the injection wells after 14 months of operation and flushing of the treatment zone with ~20,000 pore volumes of injected air. Results post treatment showed dioxane reductions of ~94% and ~45% decrease in soil moisture. See additional information in slides at http://www.contaminantssummit.com/images/presentations/3_RobHinchee.pdf.