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Dumpsite investigation

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As part of the Pacific Right Bank Flood Protection Project, King County has been investigating a former dumpsite under Pacific City Park for cleanup under the guidance of the Washington State Department of Ecology’s Voluntary Cleanup Program. King County conducted additional soil, groundwater, and vapor sampling in May 2023 as part of the multi-step dumpsite investigation. Results from the May 2023 sampling effort can be found in the Vapor Intrusion Investigation, May 2023 Sampling Results report.

Background 

The Pacific Right Bank Flood Protection Project started in 2010 to substantially reduce the potential for White River flooding within the City of Pacific and to improve environmental conditions along this portion of the river. The project site includes the land that Pacific City Park is on, which is owned by King County. From the 1920s to the 1960s the land was used as a dumpsite. Once dumping ended, the site was filled and leased by King County to the City of Pacific for use as a park in 1969.

The proposed flood protection project triggered the need to investigate the site for cleanup. This investigation began in 2016. King County has completed several studies of the dumpsite and is currently characterizing potential dumpsite contamination and migration pathways as part of a multi-step investigation process. 

A photo that shows a dumpsite sampling investigation happening in Pacific City Park. Two people in bright yellow utility vests are working with soil samples and instruments at a temporary table. A person in the foreground is digging up some soil with shovel, and putting that soil into a white bucket.
Sampling at Pacific City Park, May 2023

 

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.

How can I stay informed?  

General information about the dumpsite cleanup investigation and this sampling effort will be posted to this webpage. If you have questions about the Pacific Right Bank Project including investigation of the dumpsite and possible cleanup actions, please contact Mary Strazer at 206-263-5817, mstrazer@kingcounty.gov.

The public will have the opportunity to provide feedback on any proposed cleanup options when the Draft Environmental Impact Statement is released.

Dumpsite Information

Vapor Intrusion Investigation May Sampling Results, 2023 (1.70 MB, PDF)

Pacific Right Bank Project, 2022-23 Offsite Sampling (map), (1.20 MB, PDF)

Sample and Analysis Plan, 2023 (3.14 MB, PDF)

Remedial Investigation Report: Pacific City Park, 2019 (PDF, 60.79 MB)

Supplemental Remedial Investigation Report: Pacific City Park, 2019 (PDF, 34.55 MB)

Pacific Park Environmental Investigation, 2017 (9.07 MB)

Pacific Park Phase II Environmental Site Assessment, 2016 (19.11 MB)

Pacific Park Phase I Environmental Site Assessment, 2015 (23.69 MB)

Additional Information

Environmental Protection Agency – What you should know about Vapor Intrusion

Agency for Toxic Substances and Disease Registry - Vinyl Chloride – ToxFAQs

Department of Ecology Voluntary Clean-up Program

Department of Ecology Vapor Intrusion  

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