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

Publication number Date Published
22-03-019October 2022
VIEW NOW May Creek Landfill Groundwater Quality Monitoring, February 2020 – March 2022 (Number of pages: 34) (Publication Size: 1863KB)

(113 pages) (5MB)

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Author(s) Carnes, J.
Description The May Creek Landfill is the site of an unpermitted solid waste landfill east of Renton, Washington. In January 2003, King County notified the Department of Ecology (Ecology) of potential contamination at the site. In August 2003, Ecology placed the property on the Confirmed and Suspected Contaminated Sites List. The site was listed as confirmed for metals in surface water as well as suspected for petroleum, antifreeze, metals, and gasoline in soil and groundwater. In 2016, EPA took responsibility for identifying and removing hazardous wastes and materials.

Soil samples collected in 2018 during removal activities identified soil contamination including petroleum hydrocarbons, dioxins, and metals. Surface water samples collected from transient locations around the site demonstrated that diesel and motor oil were present at concentrations above (not meeting) applicable state cleanup levels. In July 2019, EPA installed and sampled seven groundwater monitoring wells. EPA sampling positively identified diesel range organics, metals, and SVOCs at concentrations above cleanup levels in one or more monitoring wells.

This site is regulated under the Model Toxics Control Act (MTCA). Preliminary cleanup levels (PCULs) for potential pollutants have been established using MTCA Method B. The PCULs are set at the most stringent Method B cleanup or screening level, unless the most stringent level is below natural background; if natural background is higher than the most stringent cleanup level, the PCUL is set at the natural background value.

Ecology sampled the seven monitoring wells eight times during February 2020 – March 2022. Sampling was for a broad list of pollutants, including petroleum products, volatile organic compounds, SVOCs, pesticides, PCBs, dioxins/ furans, and metals. Several pollutants – including #2 diesel, lube oil, multiple metals, and PCBs – were consistently detected above the established PCULs in one or more monitoring wells
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Contact Jacob Carnes at 360-407-6764 or
Keywords May Creek, Model Toxics Control Act (MTCA), metals, petroleum, groundwater, diesel, lube oil
WATERSHED Water Resource Inventory Area 08 Cedar-Sammamish
DATA Environmental Information Management (EIM) #FS1292568


Quality Assurance Project Plan: May Creek Landfill Groundwater Assessment Monitoring

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