In selecting technologies to remediate contaminated soil and ground water, the in-situ approach-treating the contaminants in place without excavating and disturbing-is the preferred approach. In most cases, the in-situ approach is the most economical altcrnative, and a number of technologies have emerged over the last decade showing varying degrees of success. The major obstacle of in-situ remediation is the permeability of the geologic formation. If the site contains fine-grained soils, such as silts or clays, or dense bedrock, such as shale or siltstone, in-situ tcchnologies are nor effective. The hydraulic conductivity limit below which most in-situ technologies are not normally applicable is 1 x To overcome the inherent difficulties of remediating fine-grained soils and dense bedrock, a process known as 'pneumatic fracturing" was developed at the Hazardous Substance Management Research Center (HSMRC) located at the New Jersey Institute of Technology (NJIT) in Newark. The process may be generally described as injecting air (or another gas) into a contaminated geologic formation at sufficient pressure and flow rate so that artificial fractures are created. Once established, the fractures increase the permeability of the formation, thereby making contaminant removal or treatment more efficient. Pneumatic fracturing is similar in concept to the hydraulic fracturing techniques' used in the petroleum and watcr-well industry to cnhance product cm/sec.
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