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Quality Assurance Project Plan: May Creek Landfill Groundwater Assessment Monitoring

Publication number Date Published
20-03-115November 2020
VIEW NOW Quality Assurance Project Plan: May Creek Landfill Groundwater Assessment Monitoring (Number of pages: 61) (Publication Size: 2132KB)

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Author(s) Carnes, J.
Description The May Creek Landfill is an unpermitted solid waste landfill east of Renton, WA. King County notified the Department of Ecology (Ecology) of potential contamination at the site in January 2003. In August 2003, Ecology placed the May Creek Landfill on the Confirmed and Suspected Contaminated Sites List. The site was listed as confirmed for metals in surface water and suspected for petroleum, antifreeze, metals, and gasoline in soil and groundwater. In 2016, an EPA response team took responsibility for identification and removal of hazardous wastes and materials. Soil samples collected in 2018 identified soil contamination including petroleum hydrocarbons, dioxins, and metals. Surface water samples collected around the site demonstrated that diesel and motor oil were present at concentrations greater than applicable state cleanup levels.

In July 2019, EPA installed and sampled 7 groundwater monitoring wells on the site. EPA analyzed the samples for a wide range of contaminants. The results of EPA groundwater sampling positively identified diesel range organics, metals, and semi-volatile organic compounds at concentrations above applicable cleanup levels. Ecology will monitor groundwater quarterly for 2 years. The sampling program is designed to collect representative groundwater data to assess concentrations of the contaminants at the site.
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Contact Jacob Carnes at 360-407-6764 or
Keywords May Creek, groundwater monitoring, quality assurance project plan, PCBs, dioxin
WEB PAGE Groundwater quality assessment
WATERSHED Water Resource Inventory Area 08 Cedar-Sammamish
DATA Environmental Information Management (EIM) #FS1292568


May Creek Landfill Groundwater Quality Monitoring, February 2020 – March 2022

Addendum to Quality Assurance Project Plan: May Creek Landfill Groundwater Assessment Monitoring