Case Studies - NJ010 - Pneumatic Fracturing, Bioinjection

PVC Manufacturing Facility - Flemington, NJ

Project Objective
The site is a former polyvinyl chloride (PVC) manufacturing facility in Central New Jersey. The aquifer in the vicinity of a former aboveground TCE storage was contaminated with TCE at concentrations as high as 690 mg/L. The contamination is predominately within a bedrock formation transitioning from a weathered zone to that of a more competent and moderately fractured zone. The remediation approach involved the pneumatic fracturing (PF) and the injection of a strain of constitutive TCE degrading bacteria.

Approach
The field program was initiated with the installation of monitoring wells to provide a sufficient monitoring network surrounding a single PF/injection well installed in the center of the delineated plume. Prior to the commencement of the pneumatic fracturing and injection phase, the field personnel conducted a series of permeability tests to determine the baseline intrinsic air permeability and hydraulic conductivity values in addition to conducting visual inspections of naturally occurring fractures.

The same pneumatic and hydraulic tests were performed in the formation subsequent to the PF injection. Comparison of the pre- and post- test results indicated a 653% increase in the intrinsic air permeability and a 250% increase in hydraulic conductivity. In addition, fracture aperture increased from an average baseline value of 428 microns to 783 microns subsequent to the PF operation. The results showed that the PF was successful in enhancing the subsurface bulk permeability.

ARS’ proprietary pneumatic fracturing equipment was integrated with a slurry injection process for the delivery of a laboratory-cultured TCE degrading bacteria (Burkholderia cepacia ENV435) into the newly created or dilated fracture network.

The innoculum solution consisted of water and approximately 30 to 42 gallons of the bacteria, as well as a specific amount of a concentrated liquid carbon source sufficient to produce approximately 0.5% supplemental substrate in the injected solution. Approximately 178 gallons of the inoculum solution were injected in conjunction with the pneumatic fracturing.

Outcome
The performance verification monitoring consisted of background sampling prior to pneumatic injection of the TCE degrading bacteria, and a series of post-injection monitoring and sampling events.

The 10-week post-injection monitoring showed a 67% to 94% decrease in TCE concentrations in the monitoring wells.

Reference: Keffer, E., J. Schuring, and S. Abrams. 1999. “Remediation of a Low Permeability TCE Contaminated Bedrock, Part 1. Pneumatic Fracturing Technology for Permeability Enhancement.” In Remediation in Rock Masses. Edited by Inyand and Bruell. Reston, VA: ASCE Press.

Walsh, M., T. Boland, J.L. Liskowitz, M. DeFlaun, R. Steffan, 1996. “Remediation of a Low Permeability TCE Contaminated Bedrock, Part 2 Pneumatic Injection of Constitutive TCE Degrading Organism. Remediation in Rock Masses, edited by H. Inyang and C. Bruell, ASCE Press.

 

 

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