Volatile Contaminant Extraction Enhanced by Pneumatic Fracturing

Abstract

Contamination of the subsurface by volatile organic compounds (VOCs) must be remediated to protect public health. Soil vapor extraction has been proven to be an effective technology for removing VOCs from the vadose zone of geologic formations of high air permeability. The effectiveness of the technology reduces tremendously in formations of low air permeability such as fine-grained soils or sedimentary rock formations. The technology can be enhanced by pneumatic fracturing to increase the air permeability of the formation. Pneumatic fracturing uses compressed clean air to create new fractures in soil formations and to widen existing fractures in sedimentary rock formations so that the air permeability of the formation is increased by orders of magnitude. The mode of contaminant transport in the subsurface is changed from primarily diffusion to advection and hydrodynamic dispersion. The efficiency of VOC contaminant removal by soil vapor extraction is thus improved tremendously and, in turn, is more economical. This paper presents the concepts of the enhancement technology, the development of the technology, and two field case histories on the application of the technology.