UNITED-STATES-ENVIRONMENTAL-PROTECTION-AGENCY SUPERFUND INNOVATIVE TECHNOLOGY EVALUATION OF PNEUMATIC FRACTURING EXTRACTION (SM)

The U.S. Environmental Protection Agency (EPA), in cooperation with Accutech Remedial Systems (ARS) and the New Jersey Institute of Technology (NJIT), performed a field demonstration of Pneumatic Fracturing Extraction (PFE)SM for the removal of chlorinated-volatile organic compounds (VOCs) from vadose zones of low permeability. The demonstration was conducted in the fall of 1992 at an industrial park in Somerville, New Jersey, where removal of VOC contamination in shale bedrock was required to comply with New Jersey's Environmental Cleanup Responsibility Act (ECRA). During the demonstration, airflow and contaminant concentrations were monitored to establish a database against which the developer's claims about the technology were evaluated. The developer contended that PFE would increase extracted-airflow rates from the subsurface formation by at least 100 percent and would increase the mass removal rate for the key contaminant, trichloroethene (TCE), by at least 50 percent. Also, during the demonstration hot-gas injection was evaluated. Based on comparisons of four-hour test results before and after fracturing, airflow rates increased more than 600 percent, and TCE mass-removal rates increased about 675 percent. The increase in TCE mass-removal rates appeared to be a result, primarily, of the increased airflow. In addition, the extracted air contained significantly higher concentrations of other VOCs after fracturing. Using data developed in the four-hour postfracture test, the estimated cost for a hypothetical one-year clean-up is $140 per pound of TCE removed, or $140 per ton of soil contaminated with one pound of TCE. Experiments to evaluate the effects of injecting heated air, at 200 to 250-degrees-F, into the vadose zone gave inconclusive results.