King County repairs, tests pipeline | Cedar Hills Regional Landfill

Repairs, inspections and pressure testing have been completed to the landfill gas pipe that broke nearly two weeks ago at King County’s Cedar Hills Regional Landfill, and the pipeline is once again sending the collected gas from decomposing garbage to an energy conversion plant.

The pipeline break was discovered Dec. 7 at the landfill. The break occurred in a pipe that delivers collected landfill gas to a plant that cleans and sends the scrubbed gas to a nearby natural gas pipeline.

Upon discovery, workers immediately shut down the flow of gas through the broken pipe and sent the gas to the landfill’s flare station where it could be safely burned off.

The broken section of pipeline was replaced Dec. 10. Pressure testing on the repaired line was done Dec. 11 and again on Dec. 19 by an independent contractor. No leaks or other problems were found during pressure testing, and the flow of landfill gas to the energy conversion plant resumed in the early afternoon of Friday, Dec. 20.

As a result of this pipeline break, King County has added an additional alarm and pipeline shut-off mechanism to the pipeline control system at the landfill. King County Solid Waste Division workers will also conduct additional checks of the pipeline periodically throughout the day and night.

The cause of the pipeline break remains under investigation.

For more information about the pipe failure, contact Kevin Kiernan of the Solid Waste Division, at 206-477-4555. Learn more about the landfill gas-to-energy project at

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