Risk-based corrective action (RBCA) is rapidly becoming an accepted approach for the remediation of contaminated sites. Under a RBCA approach, the risks to human health and the environment associated with a contaminated site are evaluated and appropriate corrective measures are taken as needed to reduce risk to acceptable levels. A series of standard guides of RBCA have been developed by American Society for Testing and Materials (ASTM). The main task of this study was to conduct a risk assessment at a site contaminated with chlorinated organic compounds. The studied site had a chlorinated organic compound leakage incident, which caused groundwater contamination. The contaminants of concern included trichloroethylene (TCE) and dichloroethylene (DCE). The concentrations of TCE and DCE exceeded the control standards of 0.05 and 0.07 mg/L, respectively. The contamination has a tendency to move downstream along with groundwater. The goals of this study were to: (1) conduct risk assessment at the site, and to evaluate the risk of downstream acceptor; (2) analyze the carcinogenicity risk and the possible pollution transmission pathway to provide the management personnel a basis for future site screening, planning and technical improving; (3) evaluate the effect of natural attenuation (NA) processes on risk reduction; and (4) apply Monte Carlo analysis method to conduct uncertainty analysis at the site. In this study, RBCA Tool Kit for Chemical Release, 1.3 edition established by Groundwater Service, Inc. was applied for risk assessment. Moreover, the health risk assessment stimulation system developed by the Taiwan Environmental Protection Administration was also applied to conduct risk assessment simulation for comparison. The commercial software @RISK and Microsoft¡¦s EXCEL spreadsheet was used to conduct Monte Carlo analysis to analyze risk probability distribution.
Results show that the health risk assessment result has indicated that the main risk at this site was through groundwater exposure pathway. If the biodegradation process occurs, the contaminant plume will be controlled and the risk will be reduced. Thus, the total carcinogenicity risk and hazard index (HI) of the downstream residential area will be reduced to acceptable levels (cancer risk < 1 ¡Ñ10-5, and HI < 1). Results from the Monte Carlo simulation show that the carcinogenic risk is about 6.38¡Ñ10-6 when the accumulation rate is 90% via inhalation. The calculated risk levels are higher than the requirement for minimum target risk level (cancer risk of 1x10-6) described in Taiwan¡¦s ¡§Soil and Groundwater Remediation Act¡¨. Results also show that the hazard index of non-carcinogenic risk is about 3.28 via the route of ingestion, which is higher than the acceptable level of 1. Based on the results of risk assessment, it is very important for the decision makers to incorporate remedial activities including institutional controls, engineering controls, and remediation programs from RBCA results. This study provides a streamlined process and guidelines of developing the risk-based decision-making strategy for contaminated sites in Taiwan.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0820108-155414 |
| Date | 20 August 2008 |
| Creators | Lin, Shu-Yu |
| Contributors | Chen, Kang-Shin, Jimmy kao, Dr.Wu, Dr.Yeh |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0820108-155414 |
| Rights | campus_withheld, Copyright information available at source archive |
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