King County officials continue to investigate the cause of a break in a landfill gas pipe earlier this month at the county’s Cedar Hills Regional Landfill.

The break was discovered during the early evening of Dec. 7, in between routine inspections along the perimeter of the 920-acre landfill, east of Renton. The break was in a pipe that delivers the collected landfill gas to a plant that cleans and sends the scrubbed gas to a nearby natural gas pipeline.

Workers 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. Prior to bringing the landfill gas-to-energy plant online in 2010, all of the collected landfill gas was burned off. The exact cause of the pipe failure has not yet been determined, pending the results of a detailed laboratory analysis of the broken pipe.

King County Solid Waste Division Director Pat McLaughlin said it’s possible overnight temperatures that fell into the single digits might have contributed to the break.

King County has taken several immediate steps in the wake of the pipe break:

· Employees have performed several pressure tests of the gas pipe within the landfill, including double-checking all of the welds throughout the network of pipes that draw gas from buried decomposing garbage toward the landfill gas-to-energy plant.

· Workers are making regular inspections of the supply line that feeds landfill gas to the energy plant, including hourly checks at night.

· Within the next four to six weeks, changes to the control system will provide real-time data on pipe status.

· Employees have also met with landfill neighbors to discuss their concerns about the pipe break. Air quality tests within landfill neighbor homes detected no landfill gas.