The Palermo Wellfield is an underground source of drinking water for the City of Tumwater, Washington. The wellfield is situated near a residential neighborhood at the foot of a steep hillside, below a number of current and former commercial sites containing potentially dangerous contamination by chlorinated solvents. This contamination poses a risk to the Palermo Wellfield and the health of local residents. GeoEngineers is working to identify the scope of the contamination and measure potential threats to residents of the Palermo neighborhood.
When City of Tumwater officials discovered chlorinated solvent trichloroethene (TCE) in the Palermo Wellfield’s groundwater, regulatory agencies began to investigate the source, magnitude and extent of the contamination in order to reduce public exposure. Upon investigation, Perchloroethylene (tetrachlorethylene) (PCE) was also found to be present in portions of the site. Based on the investigation results, the Environmental Protection Agency (EPA) designated the area, including the nearby Palermo neighborhood, as a Superfund site and began remediation efforts. The EPA was concerned that the TCE and PCE levels would present a potential health risk to portions of the city.
The EPA found PCE emanating from a commercial site (a dry cleaning business) on the hill above the neighborhood and wellfield, including one operational and historical dry cleaning business. EPA tests also identified sources of TCE at two separate Washington State Department of Transportation (WSDOT) properties. EPA ultimately identified WSDOT as a liable party for the TCE releases.
In 2013, WSDOT engaged GeoEngineers to continue monitoring groundwater and air to further characterize the nature and extent of contamination, assess health risks posed by these chemicals and eventually recommend additional remediation methods at the site. GeoEngineers is also monitoring remediation systems that the EPA already installed on the site, a subdrain and treatment lagoon to redirect contaminated groundwater away from the neighborhood.
In order to evaluate remaining data gaps and potentially update ongoing remediation methods, GeoEngineers also recommended a newer direct sensing drilling technology to perform an assessment. A more complete data set will give a clearer understanding of the location and amount of TCE and PCE remaining at the site.
TCE and PCE solvents may also pose a vapor intrusion risk—vapors can enter structures above impacted soil or groundwater and cause health problems. GeoEngineers used several air testing methods and worked with regulatory agencies to assess the air risk inside homes within the neighborhood.
GeoEngineers has used several unique strategies to efficiently characterize the extent of chemicals of concern on the Palermo site.
GeoEngineers’ work for WSDOT at Palermo is ongoing, and long-term environmental monitoring and remediation is expected. The data gaps assessment is expected to provide a significantly improved characterization of concentrations and locations of PCE and TCE in groundwater and soil at various locations throughout the site.