- Bioremediation following steam injection decreased TCE concentrations to less than 2 µg/L in all source area wells
- Biobarrier successful in preventing TCE mass from migrating off-site
- Site Closure achieved
- Client: GSI Water Solutions, Inc.
- Site Location: Pacific Northwest
- Services Provided:
- KB-1® Bioaugmentation
- Gene-Trac® Testing
Site investigation activities performed in 1999 identified trichloroethene (TCE) concentrations greater than 100 mg/L in the primary source area and up to 1 mg/L in 2 other areas with low concentrations of cis-1,2-dichloroethene (cDCE) and vinyl chloride (VC). Source zone soils contained TCE concentrations as high as 1,960 mg/Kg, which acted as an ongoing source of TCE to groundwater.
Targeted injection of steam, pump & treat, and bioremediation technologies were the combined remedial actions used at the Site. In 2001, source area treatment was performed using steam injection coupled with dual-phase extraction of heated groundwater and vapor. A groundwater pump and treat system was operated from 2000 to 2007 at the north property to prevent further offsite migration of TCE in groundwater. Enhanced bioremediation using electron donor addition and KB-1® bioaugmentation was used in the source areas and for a biotreatment barrier located near the property. The bioremediation remedy was pilot tested in 2005 followed by full scale operations in 2007 and 2008.
Steam treatment in the source area resulted in a three order of magnitude decrease in groundwater TCE concentrations in the source area and a 30 to 95 % reduction of TCE concentrations in the downgradient wells. Soil TCE concentrations were reduced to 0.0027 mg/Kg indicating that the soils in the source area were no longer a significant source of TCE to groundwater. The steam injection and bioremediation efforts were successful leading to the shut down of the pump & treat system in 2007.
Following bioremediation in the source area, TCE concentrations decreased to less than 2 µg/L in all wells along with corresponding increases in degradation products indicating reductive dechlorination of cDCE and VC was occurring. Groundwater TCE concentrations decreased to less than 1 µg/L in samples collected from downgradient wells. Degradation products were also dechlorinated to less than regulatory limits with corresponding increases in ethene. Groundwater temperatures following the steam injection were optimal (20 to 30 oC) for bioremediation, increasing the rates of dechlorination and shortening the time to reach cleanup goals.