Vacuum‐enhanced recovery of water and NAPL: Concept and field test

Abstract Many hydrocarbon‐contaminated soils contain nonaqueous phase liquid (NAPL) following releases from facilities such as underground storage tanks and pipelines. The recovery of free product by pumping from extraction wells or trenches is often an essential prerequisite step prior to further remedial actions. Vacuum‐enhanced NAPL recovery (sometimes referred to as dual‐phase extraction or bioslurping) has attracted recent attention because it offers a means to increase NAPL recovery rates compared with conventional methods, and to accomplish dewatering, while also facilitating vapor‐based unsaturated zone cleanup. A conceptual model is presented that recognizes the effects that vacuum‐enhanced recovery has on soil water and NAPL, with a focus on liquid residing at negative gage pressures and therefore lacking sufficient potential energy to flow into a conventional recovery well or trench. The imposition during vacuum‐enhanced recovery of subatmospheric pressures within the subsurface can reduce the ...