'Hot Spot' Remediation Using Enhanced Natural Attenuation and Groundwater Extraction

摘要

In the current regulatory framework of risk-based corrective action programs, the focus of active remediation is shifting to "hot spots" (e.g. areas of free phase product and/or off-site migration) which can preclude obtaining a "No Further Remediation" determination. Not only do these hot spots present technical challenges to obtaining an NFR determination, they also pose financial, legal and compliance liabilities to the property owner; however, cost-effective remedial approaches exist where innovative and traditional technologies are combined to reduce and/or eliminate liabilities and obtain an NFR determination. This paper presents a case study of a voluntary, private-party remediation designed to reduce liabilities associated with free product and off-site migration of contamination in low permeability soils within a cost capped budget. The client's objective was to divest the property; however, the marketability and value of the property was greatly reduced by the existing environmental liabilities. The case involves an office/warehouse property impacted by the historical gasoline storage tank operations of a former owner. Site characterization revealed the presence of free product in the vicinity of the former tank locations as well as potential off-site groundwater impacts. A cost-effective hot spot remediation plan was developed to address the free product and off-site migration issues. The remedial action plan included installation of trenches to extract contaminated groundwater/free product and permeable barrier walls to enhance natural attenuation of the contaminant plume. The plan was successfully implemented to eliminate free product and prevent further off-site migration of contaminants. In addition, source area concentrations were reduced to below applicable remediation objectives.