No abstract

Risk-based corrective action (RBCA) is a scientifically-accepted approach to remediate polluted sites. Under the RBCA approach, the risks to human health associated with polluted sites are assessed and appropriate remedial measures are taken to reduce risks. RBCA evaluations involve the use of risk models to assess health risks to different receptors. In Taiwan, the Soil and Groundwater Remediation Act was enforced in 2000. The government of Taiwan also use risk assessment protocols to obtain acceptable remediation goals for polluted sites with low risks. In this study, the application of risk assessment to derive remediation goals and develop remedial strategies at a fuel-oil spill site were performed. After the risk evaluation, the soil and groundwater remediation goals for total petroleum hydrocarbon (TPH), benzene, toluene, ethylbenzene, and xylenes (BTEX) were determined. The remediation levels meet with the requirements for minimum target risk levels (cancer risk = 1×10-6 and hazard quotient = 1). The developed risk-based cleanup goals are calculated based on actual land use and exposure pathways rather than on assumed maximum exposure. After the completion of RBCA process, the remediation cost can be significantly reduced. Based on the risk assessment results, source zone remediation, natural attenuation, and long term monitoring were recommended as the remediation strategies of the studied site to reduce risks to human health. Results from this study provide a streamlined process for future risk assessment work at petroleum-hydrocarbon polluted sites in Taiwan. RBCA is a sound and defensible basis for site closure, and it offers a more logical framework for making site closure decisions.

A trichloroethene (TCE) plume has been discovered inside an industrial park located in Taiwan. The objectives of this study were to characterize the solvent spill site and prepare a corrective action plan (CAP) for site remediation. The following tasks have been performed under Taiwan Soil and Groundwater Remediation Act corrective action: (1) geophysical survey to verify the existence and fate of all potential contaminant sources in the vicinity of the avionics repair shop; (2) soil-gas survey and soil/groundwater analyses to delineate the lateral and vertical extent of contaminants in the subsurface; (3) application of field screening techniques to determine the presence of dense, non-aqueous-phase liquids (DNAPLs); (4) contaminant transport modeling; (5) evaluation of the remedial options, conduction of cost analysis, and selection of the optimal treatment system. Results from the site characterization indicate that an extended TCE plume existed in site groundwater, which needs to be contained and remediated. A two-phase remedial approach has been developed. Phase I was to contain the existing dissolved groundwater plume in the surficial aquifer and initiate mass removal of DNAPLs. Phase II was to conduct feasibility studies and possibly test surfactant washing and biobarrier techniques.