Landsburg Mine
Kent Kangley Rd & 268th Ave SE, Ravensdale, WA 98051

Landsburg Mine Trench
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Consent Decree (CD)
A final legal agreement, called a Consent Decree, went into effect for the Landsburg site as of November 6, 2017.  The CD settles liability between Ecology and the liable parties for the site, and spells out a final cleanup action plan that must be implemented, as well as a schedule for completing cleanup.

Cleanup Action Plan (CAP)
A main piece of the CD is a Cleanup Action Plan. The CAP spells out what steps will be taken to address contamination at the Site. It is designed to protect drinking water, people, and the environment. In this case the CAP calls for specific steps:

  • Bury and contain the wastes in the north trench with a protective cap to prevent contact with the waste and reduce rainwater from seeping into the trench and leaching the wastes;
  • Monitor groundwater with early warning wells and long-term monitoring;
  • Restrict future land use to protect cap;
  • Prohibit groundwater from being used except for monitoring purposes;
  • Test nearby private wells annually for five years and re-evaluate if further testing is needed;
  • Have a contingency plan if contamination is found in monitoring wells. The plan, if triggered, will pump, contain, treat, and safely discharge any contaminated groundwater to sewer;
  • Install roads, cement pad, electrical lines and utilities and other infrastructure for pumping and treatment systems.

New Substance Detected by Monitoring Wells, Added to Groundwater Monitoring Program
Before the CD and CAP were finalized, groundwater was monitored at the Site using 10 monitoring wells set at various depths and locations. The groundwater was analyzed for around 220 contaminants in order to detect any potential contamination coming from the waste area. 

In November 2017, low levels of a chemical called 1,4-Dioxane were found at several monitoring wells on the Site. Although these levels were low, they were above allowable levels under state standards of Washington cleanup law, the Model Toxics Control Act (MTCA). The decision was made to install more monitoring wells to help trace the extent of 1,4-Dioxane at the Site. All the site wells were resampled in May 2018 and showed slightly lower levels of the chemical. It had been previously decided to add 1,4-Dioxane to the list of chemicals tested from the Site monitoring wells. 

1,4-Dioxane is a man-made industrial chemical that is mixable in water. It is used as a stabilizer for chlorinated solvents, and is a byproduct in many products, including paint strippers, dyes, greases, antifreeze and aircraft deicing fluids. It is also common in consumer products such as deodorants, shampoos, and cosmetics.

1,4-Dioxane is a likely human carcinogen. Low level exposure to 1,4-Dioxane over a lifetime can increase the risk of cancer. However this would mean about a 1/1 million chance of getting cancer if someone drank 2 liters of water per day containing 1,4-Dioxane at 0.35 parts per billion for 70 years.  On part per billion is about one half teaspoon of water in an Olympic-size swimming pool.
While the risk from 1,4-Dioxane is low, it is a contaminant found at the Site at levels above allowable MTCA levels and must be addressed.

Read more about 1,4-Dioxane here.

Next Steps
Ecology is currently working with the liable parties for the Site and the City of Kent to formulate next steps based on the CAP.  Please stay tuned to this page in the next few days for updates. 

Landsburg Mine Location
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The Landsburg Mine site is a former underground coal mine located approximately 1.5 miles northwest of Ravensdale in southeast King County. The site is located directly south of the S.E. Summit-Landsburg Road and north of S.E. Kent-Kangley Road. The Cedar River is approximately 500 feet north of the site. The former mine site occupies property currently owned by Palmer Coking Coal Company and formerly by the Plum Creek Timber Company, L.P.

During the late 1960s to late 1970s, industrial wastes were disposed in the trench that formed above the former mine. The 1996 remedial investigation and subsequent interim, ongoing groundwater monitoring have shown no impacts to groundwater at the site or surrounding areas.

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In the next few months, waters in the north and south portals will be sampled and analyzed.  Sentinel wells will be installed as the cleanup action plan directs. In the meantime, interim groundwater sampling will continue.

The liable parties for the site must submit a report to Ecology that lays out the details of the cleanup action plan.  That report is called an Engineering Design Report (EDR). Ecology must review and approve that report.

Once the EDR is approved, the construction phase of the cleanup will begin. This phase includes filling in part of the trench where wastes are located, and covering it will a protective cap. The filling of the trench will occur over two years to allow the fill to settle. Ecology will closely monitor the site during this process.

Please check back here to get updates on cleanup activities!

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The Washington State Department of Health (Health) worked with Ecology and the City of Kent to complete a health consultation. They wanted to learn if the work done at the Landsburg Mine site provided the information they need to determine whether there is a potential threat to drinking water supplies and surface water in the area. Health learned three things:

The waste at the site could pose a health threat to ground-water in the area, which is used for drinking water.

None of the groundwater chemicals that were evaluated, except arsenic, pose a health threat. Although the highest level of arsenic found at the site presents some risk of long-term health effects, no one is drinking thegroundwater and the level of arsenic is below drinking water standards.

There are some physical hazards at the site, including steep trench walls and possible openings into the mine. 

Ecology and the Potentially Liable Persons agreed to take actions to address many of Health’s suggestions. This is also described in the Responsiveness Summary.  A full copy of the health consultation reportand recommendations is available at

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The Environmental Protection Agency (EPA) developed an Environmental Justice (EJ) tool for mapping and screening a community, called EJ Screen. Ecology uses this tool to learn about the demographics of communities around cleanup sites. By doing this we can better design a cleanup and communication strategy that works for the community. The EJ Screen tool is based on nationally consistent data and an approach that combines environmental and demographic indicators in maps and reports. See below for information about demographics in the area of the Landsburg Mine Site.

EJSCREEN Census Block Map - This shows the Census Blocks used to generate the reports below.

EJSCREEN ACS Summary Report Landsburg Mine Site – This shows the demographic information about the population of the area.

EJScreen Report Landsburg Mine Site – This report shows the values for environmental and demographic indicators and EJSCREEN indexes. These percentiles provide perspective on how the selected block group or buffer area compares to the entire state, EPA region, or nation.

What's in My Neighborhood?
In addition to EPA's EJ Screen tool, Ecology developed a tool you can use to see what other cleanups are happening in any neighborhood you're interested in. You can view it by going to What’s in My Neighborhood .



Map showing site location as King County, WA SITE INFORMATION


View Electronic Documents

Site Summary Report

Facility Site ID: # 2139

Cleanup Site ID: 60

Ravensdale, King County

Status: Cleanup Started   Get definitions of Status terminology

Jerome Cruz
Site Manager

Brad Petrovich
Project Planner and Public Involvement Coordinator
(425) 649-4486

Document Repositories:

Northwest Regional Office
3190 160th Ave SE
Bellevue, 98008-5452

Maple Valley Public Library
21844 SE 248th Street
Maple Valley, 98038