Compatible Technologies to Improve In-Situ Remediation of Chlorinated Solvents: A Case Study

Abstract: A chlorinated solvent plume (perchloroethylene or PCE) was discovered in the shallow ground water as a result of historical operating practices surrounding a Houston area dry cleaning facility. Permeable shallow soil at the site allowed rapid vertical migration at the source and lateral migration in the shallow ground water. This migration resulted in an off-site migration of the plume beneath an apartment complex causing concern for potential vapor intrusion hazards; as well as, a decrease in property value. A ground-water extraction and treatment system was installed to address the dissolved phase concentrations. The system reduced the total volatile organic compound (VOC) concentration in the source area from 115,400 to 36,500 µg/l. However, over time, operating maintenance and cost escalations were exceeding the ongoing remedial benefit. The system was shut down after nine years of operation. A review of available remedial technologies that could be implemented within the physical constraints of the site was conducted. In-situ enhanced aerobic bioremediation was selected to address the remaining ground-water concentrations because of the permeability of the formation, the relatively aerobic conditions, and the benefit of reducing the risk of VC accumulation.