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Project description

In 2008, King County Solid Waste Division (SWD) contracted with renewable energy company Bio Energy (Washington) LLC, (BEW) to generate renewable energy from landfill gas produced by decomposing organic material at the Cedar Hills Regional Landfill, and thus reduce greenhouse gas emissions. The BEW gas-to-energy plant separates methane from the other components of the landfill gas, compresses the separated methane gas, and conveys it into a commercial natural gas pipeline as pipeline-quality gas.

At Cedar Hills, landfill gas is captured through a network of pipes and delivered to BEW’s on-site landfill gas-to-energy plant through a 24-inch diameter conveyance pipeline. The pipeline carries collected landfill gas from a flare station, located at the north end of the landfill property, to the BEW gas-to-energy plant, located at the south end of the landfill property, for processing. Prior to construction of the BEW gas-to-energy plant, all collected landfill gas was disposed of by burning at the flare station. When the BEW gas-to-energy plant was opened, the use of the flare station was reduced.

SWD is proposing to install a second conveyance pipeline to carry landfill gas from the flare station to BEW’s plant that would provide redundancy in this infrastructure; allowing a continuous supply of landfill gas to be produced into renewable energy. The new pipeline will be used as the primary pipeline for carrying landfill gas from the flare station to the BEW gas-to-energy plant for processing. The existing pipeline will be used in a back-up capacity. This will allow maintenance and testing to occur at the same time, and still allow landfill gas to be delivered for processing into renewable energy. Thus, less landfill gas will be disposed through the existing flare system.

Below are some of the features of the new pipeline:

  • Constructed of 30-inch diameter high density polyethylene (HDPE) pipe.
  • The pipe will be buried two to four feet underground.
  • Short pipe sections will be installed aboveground where the new pipeline connects to the existing pipeline system at the flare station and the BEW plant. Above-ground runs of pipeline will be assessed by design engineers to confirm that expansion and contraction can occur without impacts to the stability and function of the pipeline.
  • The existing conveyance pipeline operates under a vacuum over the entire length using fans that pull the landfill gas from the flare station to the BEW plant. This system creates the vacuum that ensures that landfill gas will not leak from the conveyance pipeline, and the new pipeline will operate under a similar system.
  • The pipeline will be installed within the landfill’s permitted footprint. It will not impact the landfill property buffer.
  • The pipeline will be routed along the edges of existing roads and developed areas located in the west and south portions of the landfill property.

In accordance with the State Environmental Policy Act (SEPA), the SWD is completing a SEPA checklist to identify possible environmental impacts from development of this project. Information provided during the SEPA review process helps agency decision-makers, applicants and the public understand how a proposal will affect the environment. The SEPA checklist addressing this project is available for review and comment under the project documents section of this page.

Gas Pipeline Upgrade vicinity map
Vicinity map
Project overview drawing
Project overview drawing

Project milestone schedule – january 2016 (subject to change)


Purpose / action taken

Jan. 20, 2016

SWD issues a “Determination of Nonsignificance” and issues a SEPA checklist for 14-day public review and comment period.

Feb. 3, 2016

Deadline for submitting comments on the Determination of Nonsignificance

Feb 8, 2016 at 5 p.m.

Deadline for submitting a written appeal of the SEPA determination per King County Public Rule PUT 7-4-1

Public involvement

Public involvement is essential to identify and evaluate the project. To learn more about the project and provide input, please:

Project documents

Project contacts

Project manager
Lynde Eller
King County Solid Waste Division
Telephone: 206-477-4466, TTY Relay: 711

Public involvement
Polly Young
King County Solid Waste Division
Telephone: 206-477-4466, TTY Relay: 711

Contact Us

 Call: 206-477-4466

TTY Relay: 711

Fax: 206-296-0197

King County Solid Waste Division mission: Waste Prevention, Resource Recovery, Waste Disposal