Dumpsite investigation

Common questions about sampling

What contamination have you found?

Samples from surface water, soil and groundwater in the park and nearby areas have shown concentrations of synthetic chemicals, solvents, oil, and metal-related contaminants above site screening levels. Screening levels are used to guide when further investigation or immediate action may be necessary based on the contaminant migration pathway. Sampling completed to date has not found hazardous materials near the ground surface that could pose a health or safety risk to park users.

After playing in or coming into contact with soil in the park, we recommend that park users wash their hands with soap and water. This helps decrease contact with area-wide arsenic levels found in the soil. Learn more healthy actions to take to decrease your contact with arsenic at the WA State Department of Ecology Dirt Alert webpage.

What is being done now?

King County is committed to working with the Washington State Department of Ecology under the Voluntary Cleanup Program to investigate potential dumpsite contamination. In an abundance of caution, King County collected additional groundwater, soil, and vapor samples to the west of Pacific City Park in 2022 and 2023. Vapor sampling was recommended as a precaution to identify the concentrations and extent of contamination from a chemical called vinyl chloride.

What were the results of the May 2023 vapor intrusion investigation?

Sampling results from the most recent sampling effort in May 2023 indicate that there is not a dumpsite-associated vapor intrusion pathway to the apartment buildings adjacent to the western edge of Pacific City Park. Vinyl chloride and related contaminants of concern associated with the former landfill under Pacific City Park do not extend beyond the County property in soil or soil vapor, and they do not exceed vapor intrusion screening levels in groundwater beyond the County property boundary. Vinyl chloride was found in groundwater samples at concentrations below the screening level for vapor intrusion but in exceedance of the screening level for drinking water or human consumption of organisms (like fish). King County will continue to monitor groundwater and collect samples in 2023 and early 2024. 

Clean-up and containment of the dumpsite contaminants is being investigated as part of the Pacific Right Bank Project. Cleanup of the dumpsite would reduce the risk of exposure from dumpsite contaminants in the long-term.