Publication Summary

Groundwater samples to be tested for volatile organics were collected from five monitoring wells at the Shelton site from August 2005 through May 2006. The study purpose was to monitor concentrations of tetrachloroethylene (PCE) after the injection of a hydrogen release compound (HRC) for remediation treatment in June 2005. PCE concentrations in well 4W increased after the injection of HRC, from an average of 15 µg/L to a high of 324 µg/L in May 2006, which is higher than the MTCA cleanup standard of 5 ug/L. Groundwater monitoring is scheduled to continue quarterly for another year to determine if the HRC treatment has been effective.

Groundwater samples to be tested for volatile organic analysis were collected from five monitoring wells quarterly from August 2005 through May 2006 at Shelton Laundry and Cleaners in Shelton, Washington.

Samples were collected to monitor the concentration and distribution of tetrachloroethylene (PCE) after the injection of a hydrogen release compound (HRC) to remediate the remaining contaminants present in the vicinity of well 4W.

PCE contamination of the shallow groundwater was discovered in 1997. The source of contamination was assumed to be a 1993 spill outside a dry cleaning facility. Monitoring of four shallow wells in 1998 detected PCE in one well (4W) at a concentration of 280 µg/L.

In 2002 Ecology installed four deep wells and began monitoring groundwater quality of the eight on-site wells. From 2002 through early 2005, PCE concentrations in well 4W ranged from 10 to 25 µg/L. PCE was not detected in the four deep wells.

During August 2005 through May 2006, PCE concentrations in well 4W increased after the injection of HRC in June 2005. PCE concentrations in this well ranged from 6.8 µg/L in November 2005 to 324 µg/L in May 2006. The Model Toxic Control Act (MTCA) Method A cleanup standard for PCE is 5.0 µg/L.

Trichloroethylene (TCE) and cis-1,2-dichloroethylene (DCE) concentrations also increased in well 4W to 13 µg/L and 16 µg/L, respectively, in May 2006. The TCE concentration exceeds the MTCA cleanup standard of 5.0 µg/L. The DCE concentration was well below the cleanup standard of 70 µg/L.

Increases in contaminant concentrations such as detected in well 4W have been reported at other HRC sites as biosurfactants solubilize the volatile organics that are absorbed to the aquifer media. These increases are typically temporary. Groundwater monitoring should continue on a quarterly basis for a minimum of another year to determine if the remedial treatment with HRC has been effective.

Link to EIM data for User Study ID PMART001