Tracking Down Elusive Source of Contamination


When discovery of previously unknown contamination complicated regulatory closure at a client’s property, Farallon identified an off-property source.

After Farallon successfully completed cleanup of a former dry cleaning facility on a client’s property, groundwater at another portion of the property was discovered to be impacted by the dry cleaning solvent tetrachloroethene (PCE), potentially impacting indoor air in a second building, and complicating the regulatory closure process.  Using results from historical land use research and groundwater quality and hydrogeological data, Farallon demonstrated to the Washington State Department of Ecology (Ecology) that the source of contamination impacting the client’s property was another dry cleaning facility formerly present on a nearby property.  A vapor intrusion mitigation system was installed to prevent PCE vapors from entering the second building and impacting breathing zone air.

According to Farallon Senior Geologist Brani Jurista, “Any time you have multiple potential sources, identifying the source of contamination is much more difficult.  But we were able to show that the second plume of PCE-contaminated groundwater was not emanating from our client’s property.”

The breakthrough in the project came when a 50-year-old flyer advertising a new dry cleaning facility within two blocks of the client’s property was discovered in the archives of the local historical society.  After Farallon demonstrated to Ecology that the source of contamination impacting the client’s property was the historical dry cleaning facility, this off-site source area was cleaned up in conjunction with redevelopment.  Farallon continued groundwater monitoring and vapor intrusion mitigation on the client’s property concurrent with the source cleanup until PCE concentrations attenuated to safe levels.  Farallon obtained two No Further Action determinations from Ecology:  one for the original cleanup location, and the other for the second area of the property and associated building.