Remediation of a Groundwater Contaminated Site in Yongkang

Taiwan’s First Demonstration Project Integrating Chlorinated Site Remediation with Urban Rezoning

Remediation with High-resolution Investigation and Injected Chemical Delivery Monitoring.
Demonstration Site for Collaborative Pollution Remediation and Urban Development.

Site Background

The site is located in the Yongkang District of Tainan City, adjacent to the National Highway No. 1 Yongkang Interchange. In 2005, three areas were declared groundwater pollution control sites with use restrictions. These areas included factories, auto repair shops, roads, and open land, some of which fell within the Yongkang Transit Specialized Area of Tainan City's urban rezoning plan.

Pollution Status

Two primary pollution sources were identified. The first source originated from historical PCE* contamination and its degradation products such as TCE*, cis-1,2-DCE* and VC* from a watch case factory. This pollution plume has extended downstream approximately 300 meters, with cis-1,2-DCE* and VC* as the main pollutants accumulating in high concentrations. The second source, located along Yong-An Road, comprised chloroethenes (PCE*, TCE*, 1,1-DCE*, cis-1,2-DCE*, VC*) and chloroethanes (1,1,2-TCA*, 1,2-DCA*) pollutants of an unknown origin.

Remediation Approach

This project, initiated by the Ministry of Environment, serves as a demonstration to promote accelerated site remediation. Pollution remediation is planned in phases, beginning with the active remediation of the two main sources and containment of high-pollution areas. Environmentally friendly in situ bioremediation techniques were used to fully remediate the PCE and its breakdown products within 3.5 years, successfully halting the spread of contaminants.

Surgical Remediation

A “surgical remediation" approach was adopted for this project, utilizing intelligent characterization to accurately identify injection points, multi-depth precision double-packer injection, and cross-hole geoelectrical resistance monitoring for reagent delivery. Real-time feedback was used to adjust injection designs, improving remediation outcomes. Within 3.5 years, pollutant concentrations dropped below regulatory limits with no rebound observed during subsequent monitoring.

Note: *Perchloroethylene (PCE)
Trichloroethylene (TCE)
cis-1,2-Dichloroethylene (cis-1,2-DCE)
1,1-Dichloroethylene (1,1-DCE)
Vinyl Chloride (VC)
1,1,2-Trichloroethane (1,1,2-TCA)
1,2-Dichloroethane (1,2-DCA)