Contamination by dense non aqueous phase liquids (DNAPLs) [e.g., trichloroethylene (TCE)] in soil and groundwater has become an issue of great concern in many industrialized counties. In this study, a chlorinated-compound spill site was selected as the case study site to evaluate the possible risk to site workers and local residents caused by the contaminated soil and groundwater. The contaminants of concern at this site were TCE and 1,1-Dichloroethylene (1,1-DCE). The detected concentrations for TCE and 1,1-DCE exceeded the control standards of 0.05 and 0.07 mg/L, respectively.
In this study, the Risk-based Corrective Action (RBCA) protocol developed by American Society for Testing and Materials (ASTM), health and risk assessment methods for soil and groundwater contaminated sites developed by Taiwan Environmental Protection Administration were applied for risk calculation and quantification. Monte Carlo analysis using @RISK software was applied for uncertainty analysis to calculate the cumulative risk at 95% probability distribution. Moreover, a natural attenuation model (BIOCHLOR) was used to evaluate the effectiveness of natural attenuation mechanisms on the chlorinated compounds.
Results from this study show that the occurrence of natural attenuation for the chlorinated compounds was confirmed through the anaerobic biodegradation processes. The calculated cumulative risk at 95% cumulative probability via ingestion route was 2.61¡Ñ10-5 through the Monte Carlo analysis. The calculated cumulative risk at 95% cumulative probability via inhalation route and ambient (outdoor) vapor inhalation diffusion channels were 1.461¡Ñ10-5 and 2.17¡Ñ10-6, respectively. Because the calculated risk levels were higher than the target cancer risk is 1¡Ñ10-6 described in Taiwan¡¦s ¡§Soil and Groundwater Remediation Act¡¨, appropriate remedial actions are required to lower the risk to below the target level. Results also show that the calculated hazard index (HI) values of the contaminated site are lower than the acceptable level (HI < 1) described in the ¡§Soil and Groundwater Remediation Act.¡¨
To meet the target level of cancer risk of 1¡Ñ10-6, TCE contaminated groundwater needs to be remediated to below the site specific target level (SSTL) for inhalation exposure routes in a confined space volume, which is 6.91 ¡Ñ 10-2 mg/L. 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-0803109-172424 |
| Date | 03 August 2009 |
| Creators | Tsai, Wei-anne |
| Contributors | Chin-ju Jou, Wei-ir Wu, Chih-ming Kao, Ting-nien Wu, Wen-yen Huang |
| 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-0803109-172424 |
| Rights | not_available, Copyright information available at source archive |
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