The Environmental Protection Administration (EPA) held a meeting for discussing on draft toxic substances risk assessment technical guideline on December 14, 2000, and invited relevant organizations and agencies to discuss the contents. 　This project is to focus on the portion of groundwater and soil modeling study, introduce models systematically and verify modeling results, so as to provide references for developers, assessors and EIA agencies. Based on the study site selected by the EPA, the project conducted the literature views of site geology, soil and groundwater, as well as field investigation, groundwater monitoring wells installation, groundwater sampling and analysis to supply model input requirements. Based on Soil and Groundwater Pollution Remediation Act, the site characteristics and the data acquired, groundwater contaminant transport and fate models, including BIOCHLOR, MODFLOW-MT3D and BioF&T, were used to simulate the behavior of chlorinated organic contaminants in the groundwater, predict future concentration of contaminants, and verify and discuss the applicability of the three models. The modeling results showed that BIOCHLOR, MODFLOW-MT3D and BioF&T had similar prediction outcomes. However, in terms of simulation time, cost and data available, BIOCHLOR tends to be more suitable for the study site in comparison with the other two models. In addition, the project reviewed the related modeling issues in the current draft toxic substance risk assessment technical guideline, accompanied with the modeling acquaintances, to provide suggestions on the draft technical guideline revision, including addition of release quantity estimation, description of parameters required for risk assessment, and increase in completeness of risk assessment results.

model, chlorinated organic compounds, risk assessment