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Dirt Alert

Outreach and education for the Tacoma Smelter Plume Project

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The ASARCO smelter in Ruston, WA closed in 1986 after nearly 100 years in operation, but arsenic and lead remain in the soil and will continue to be a health risk for years to come. Public Health – Seattle & King County is working in partnership with the WA State Department of Ecology to share information about this issue.

Find out if your yard is contaminated

If you live on Vashon-Maury Island, you may be eligible to get free home soil testing. Type your address in the interactive search map of affected areas below to see if you are eligible. If you live on Vashon-Maury Island, and are not eligible for free home soil testing, check if you’re eligible for the Yard Program.

Whether or not you live in the eligible area, learn how you can test your own soil. Contact an accredited environmental laboratory to mail your samples and receive results. If you live outside Vashon-Maury Island, this is the only way you’ll be able to test your soil.

How you can protect yourself and your family

Healthy Actions are simple things you and your family can do to reduce contact with arsenic and lead in dirt.


Since arsenic and lead in soils can be a health hazard, gardeners and others who work or play in contaminated soils should take precautions to limit and reduce the amount of soil they swallow or breathe.
The goal of these suggestions is to reduce the amount of contaminated soil that you unintentionally swallow or breathe in while gardening or working around your home. Follow these guidelines to reduce your exposure:

  • Avoid gardening in soils with arsenic in excess of 20 ppm (parts per million). Bring in clean soils and build a raised bed instead.
  • Add clean soils or soil supplements such as compost or mulch to your existing garden. Clean soils are ones that are known to be contaminant-free. If you are unclear whether your new soils are clean you may consider testing. For more information on composting and mulch visit the King County Soils and Composting page.
  • Wear gloves while gardening.
  • Wash all homegrown vegetables carefully and peel vegetables where possible. Be sure to remove particles of soil on the food item. Wash inside crevices (e.g. broccoli and cauliflower).
  • Though there is evidence that vegetables and fruits may take up small amounts of arsenic into their roots or leaves, a more serious risk could come from eating fruits and vegetables that have bits of contaminated soils stuck to them.
  • Dampen soils with water before you garden to limit the amount of dust you inhale.
  • Consider wearing a mask if you spend time in dusty soils.

Review related posters and brochures.

More gardening tips from the WA Department of Ecology

Find out if your child's play area is contaminated by the Tacoma Smelter Plume

Ecology's Soil Safety Program tests and cleans up play areas at schools, childcares, and parks. Most of the clean-up work at these play areas have been completed. For more information, visit Ecology's Soil Safety Program's blog.
Check to see if your child's play area is impacted by the TSP:

  • View the King County TSP Soil Safety Service Area Map (203 KB) with zip codes and city names.
  • Type the address of your child’s school or favorite parks into Ecology’s interactive map embedded above. For privacy, the map will not display childcares.

Additional resources

What we do

With funding from the Department of Ecology's settlement with Asarco, King County Dirt Alert:

  • Collects soil samples from residential yards, within a defined service area
  • Provides soil sample results to homeowners, along with an explanation of what that means
  • Provides outreach and education to residents through community events and presentations and free multi-lingual resources.
  • Partners with community and gardening groups to increase education
  • Provides outreach to schools and childcare facilities

Contact us if you have an event or to schedule a presentation.

Background information on the Tacoma Shelter Plume Project

The plume is a 1,000 square mile area of arsenic and lead soil contamination from the former Asarco smelter in Tacoma. Levels of lead and arsenic soil contamination can be different from place to place. It is based on:

  • Distance from the smelter
  • Wind currents
  • Geographic features (such as hills)
  • If soil has been disturbed during construction, gardening, or other activities

We now know that arsenic and lead from the smelter were carried by the wind throughout all of the areas in King County that were studied, including Federal Way north to the Snohomish border and east to Maple Valley, Issaquah, and Duvall. In general, there is less contamination the farther away one goes from the smelter.
The amount of Asarco arsenic and lead is in the soil in any area of King County depends on several factors, including distance from the smelter, topography, and history of the property in question. Here are some rules of thumb to figure out the chances that your property has contamination:

  • Distance: The most contaminated soils tend to be in coastal King County from Seattle to Federal Way and on Vashon-Maury Island.
  • Topography: Soil on hillsides that face southwest tended to get more of the contamination than east and north facing hillsides because of the way the wind traveled and carried the contamination.
  • History of the property: Arsenic and lead tends to stay in the top six inches of soil. If the soil on a property was dug up, moved, or otherwise "disturbed" over the last 100 years, there may be less contamination there than on a property that was undisturbed for the entire time the smelter operated (from the late 1800s to 1986).

For example, an old growth forest or long-standing park would likely be more contaminated than a newer development where the soil was leveled and/or filled in. An older neighborhood that has not significantly changed over the years may have more chances of contamination than a newer subdivision.

The WA Dept. of Ecology is also: