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Solid Waste and Recycling

The Cedar Hills Regional Landfill

In King County reducing waste and recycling are the first priorities for handling the waste we generate. Even so, the Cedar Hills Regional Landfill remains the backbone and a necessary part of the waste management system. After all, no matter how much we learn to reduce waste, reuse goods and recycle materials, we will always generate some waste.

Aerial image of Cedar Hills Landfill, with  red arrow indicating site of current work.
The Cedar Hills landfill is a state-of-the-art facility located about 20 miles southeast of the city of Seattle. It takes all of King County's garbage, excluding the city of Seattle's. It is approximately 1 mile wide, 1.5 miles long, and 125 feet deep. The active area of the landfill (indicated by the red arrow above) is where garbage is unloaded. A close-up of the active area is seen below.

Photo of the active portion of the landfill.

  • It takes about 5 minutes to unload an 18-ton trailer full of garbage.
  • As many as a dozen trailers may be unloading at the same time.
  • Every day, we add approximately 2,000 tons of garbage to the landfill!

Landfills are not just a huge mound of trash- they use the latest technology to keep the community as safe as possible from the dangers decomposing garbage can pose to the environment. This diagram illustrates some of the features of the Cedar Hills Landfill.

"Cross-section of an active landfill" diagram.

  • The 18-ton trailers dump their loads of garbage in the active area of the landfill. That garbage is then covered up at the end of the day with 6 inches of dirt.
  • Rain that filters in with the garbage produces leachate. Pipes at the bottom of the landfill collect this leachate and treat it before sending it to the County's main water treatment plant with the rest of the water we use at home, school and work.
  • A plastic and a clay layer beneath the garbage prevents contamination of ground water.
  • Landfill gas, a byproduct of the decomposition of garbage, is collected and piped to a flare station, where it is burned.

Garbage disposal is no simple matter. Remember, the threat of contaminating our water and air doesn't just go away when the landfill reaches its capacity. The garbage continues to decompose, and must be monitored long after the landfill reaches maximum capacity. (Federal, state and local regulations require a 30 year post-closure monitoring period upon landfill closure.)

In the meantime, in another location, the process begins again, as new land must be made available to take in our garbage. Landfills do not go away, but remain a permanent fixture of our landscape.


Through small changes in your behavior, you can greatly reduce the amount of garbage that you generate.


Updated: August 16, 2000

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