“We are acting to replace a conveyance system that if it fails, would spill untreated sewage into the Ship Canal and Lake Union,” said Council Chair Larry Phillips, who represents the neighborhoods using the Ballard Siphon. “These pipes are made of compressed wood installed eight decades ago. It’s past time to upgrade the siphon to ensure the safety of the system and the public.”

A recent inspection of the Ballard Siphon determined that the wooden pipes, which rest on the bottom of the ship canal, have exceeded their service life and are flattening out, exposing them to the danger of failure. Such a failure would spill untreated sewage into Lake Union and the Ship Canal. The 36-inch wood stave pipes are made by compressing wood planks into a cylinder held together by tensioned steel bands or rods. They are located east of the Ballard Locks and west of the Ballard Bridge.

The Ballard Siphon was built in 1935 and conveys an average of 8 million gallons of untreated wastewater each day from the Ballard, Blue Ridge, Carkeek, Crown Hill, Loyal Heights, North Beach, Whittier Heights neighborhood, as well as parts of the Greenwood and North Park neighborhoods.

The Council ordinance approves $12.9 million to install an emergency bypass pipe to divert sewage flows from the siphon and prepare for replacement of the siphon using reinforced concrete and plastic pipes.