EPA Superfund Site

MOSES LAKE WELLFIELD CONTAMINATION

WA | EPA ID WAD988466355

About this site’s exposure pathways: As of January 2025, Moses Lake Wellfield Contamination Superfund (Site) is considered “Insufficient Data to make a Human Exposure control status” (HEID) because it has not been determined if per- and polyfluoroalkyl substances (PFAS) are present in residential drinking wells. The contaminants of concern for soil at the Site are polychlorinated biphenyls, petroleum hydrocarbons, trichloroethylene (TCE), arsenic, lead, and mercury. The contaminant of concern for groundwater at the Site is TCE. Currently, there are no exceedances above EPA’s maximum contaminant levels of TCE in private drinking water wells.

Perfluorohexanesulfonic acid, perfluorononanoic acid, perfluorooctane sulfonic acid and perfluorooctane acid are present and above EPA’s maximum contaminant level in monitoring wells at 6 isolated locations within the wellfield area. Sampling in private residential wells used for drinking water have not been tested for PFAS to date.

The planned activities to collect sufficient information to evaluate Human Exposure control status are groundwater sampling for PFAS and continued monitoring of TCE in private wells. EPA is currently determining strategic sampling locations at private residential wells to better understand PFAS contamination in groundwater and understand risk. EPA currently anticipates that there will be sufficient data to make a Human Exposure evaluation by 2026.

In addition, EPA will continue to conduct annual groundwater sampling for TCE at private wells throughout the site and install water filtration systems in homes with TCE levels at or above 3.5 ug/L. EPA is also developing an institution control plan to prevent the installation of new wells within the site’s groundwater institutional control boundary.