The subsurface environmental contamination investigation, assessment and remediation of petro-chemical contaminated site have been the most challenging environmental issues of environmental protection. If subsurface environmental mediums like soil and groundwater are contaminated, the investigation and remediation will always be time-consuming and costly even though they could not be cleaned up completely. Groundwater contaminated by chlorinated volatile solvents is more difficult to remedy owing to its property of dense non-aqueous phase liquid (DNAPL). This study focuses on petro-chemicals contaminated site whose subsurface environment is contaminated by chlorinated ethene. The study will also find out the efficient, effective and economic ways to identify and concretely delineate the characterization of subsurface environment and contamination, conduct human health risk management and take risk-based corrective action, so as to formulate an appropriate risk management strategy and solution. Firstly, this study applies a Triad approach to accelerate and streamline the investigation process of contaminated site. Introduction of project systematic planning, dynamic work strategy and in situ, real time survey or direct-push sampling like membrane interface probe, together with off-site measures like physical measurement and chemical analytic testing in laboratory, could reduce the key uncertain characteristics of subsurface environmental contamination and establish the conceptual cite models for health risk assessment cost-effectively. It is estimated that this method could save 6 million NTD and shorten 3 years¡¦ time in site characteristics delineation and remediation. If we wish to make the site defensible via managing the uncertain decision, the integration of Triad approach which is developed by United States Environmental Protection Agency, and Environmental Site Assessment, Accelerated Site Characterization, Health Risk Assessment and Risk-based Corrective action which were developed by American Society for Testing and Materials (ASTM), are proved in this study that they could help streamline the site characterization and remediation. This study is based on the conceptual site models of Triad Approach, the Risk-based corrective action of ASTM, the Health Risk Assessment and Evaluation Methods for Soil and Groundwater Contaminated Site, and also the software developed by the Taiwan Environmental Protection Administration. Through the health risk assessment of chlorinated ethenes contaminated site, this research aims to evaluate the quantitative health risk like chemical of concern, environmental medium, and human exposure pathway etc. The result of evaluation showed that the carcinogenic risk of tier 2 is 1.080E-01 which exceeds the acceptable risk-based standard, 1E-06; tier 2¡¦s non-carcinogenic risk, 1.819E+03, also exceeds the acceptable hazard index which is 1. Groundwater poses the highest risk among environmental media, followed by inhalation of vapor from contaminated soil and/or groundwater. The risk of inhalation of top soil particulates is the lowest. The most dangerous carcinogenic exposure of groundwater is using groundwater for shower and washing whose risk is 8.064E-02; the second highest carcinogenic pathway is groundwater ingestion. Trichloroethylene is the key chemical of concern which poses 95.6% of carcinogenic risk among all chemicals of concern. Groundwater ingestion poses the highest non-carcinogenic risk (8.919E+02), and the main chemical of concern is cis-1, 2-dichloroethylene. The main chemical of concern of soil volatilization is cis-1, 2-dichloroethylene, followed by trichloroethylene. If the site in this study wishes to reduce the health risk of human beings, it is suggested to simultaneously implement integrated risk-based corrective actions including institutional control, engineering control and remediation. For institutional control, prohibition of pumping groundwater and pumping well installation is the most cost-effective choice. For engineering control, concrete capping on uncovered surface soil is feasible when dealing with soil contamination. When it comes to groundwater contamination, steel sheet pile containment or pumping well installation could help intercept the migration of groundwater. Regarding remediation, in-situ chemical reduction injection or permeable reactive barrier, incorporated together with monitored natural attenuation are more practicable alternatives, however, they are time-consuming and costly. The process and result of this study could be the basis for managers and/or decision makers of contaminated site to conduct risk-based management and decision making.