Skip to main content
King County logo


Natural Resources and Parks
Public Affairs

Watch tunnel boring machine removal July 12 as part of King County wastewater project


A remote-controlled microtunnel boring machine has completed two tunnels underneath the Lake Washington Ship Canal as part of a King County project to protect public health and the environment. Watch Tuesday afternoon as the 26-foot-long, 7-foot-wide machine is hoisted from its exit pit in Fremont.


Join the King County Wastewater Treatment Division along the Lake Washington Ship Canal to watch the removal of a microtunnel boring machine (MTBM) that completed two tunnels for the Fremont Siphon Replacement Project:

Tuesday, July 12, 3-5 p.m.
King County Environmental Laboratory
322 W. Ewing St., Seattle, WA 98119

The Fremont Siphon Replacement Project resets the clock for critical infrastructure that has provided 100 years of service. The new pipes replace World War I-era siphon pipes that were installed in a tunnel built before the Ship Canal was created.

For the past century, the pipes have carried flows of up to 220 million gallons per day, and for the past five decades, wastewater has traveled from the Fremont Siphon to King County’s West Point Treatment Plant in the Magnolia neighborhood.

This complex tunneling project required installation of two, 465-foot-long tunnels that are 80-90 feet deep and spaced just 6 feet apart.

A remote-controlled MTBM drilled from its Fremont launch site, underneath the Ship Canal, to the exit pit located on King County’s Environmental Laboratory property. The MTBM is 26 feet long and features a cutting face that is 7 feet across.

On Tuesday, July 12, the microtunnel boring machine will be hoisted by a large crane from its exit pit in two sections, marking the completion of the tunneling process.

Because this is a construction site, visitors are required to wear sturdy, close-toed shoes.
For more information:

Fremont Siphon Replacement Project-

Ballard Siphon Replacement Project- 

Driving directions:

• From Aurora Avenue North, turn right onto Halladay Street.  Continue onto 6th Avenue North. Turn left onto Dexter Avenue North, and then slight left onto Nickerson Street. Continue on 3rd Avenue West to West Ewing Street.

• From Aurora Avenue South, turn right onto Raye Street for 0.1 mile.  Continue onto Queen Anne Drive. Turn right onto Warren Avenue North.  Turn left onto Nickerson Street.  Turn right onto 3rd Avenue West.  Turn left onto West Ewing Street.
# # #

About King County Wastewater Treatment Division
People enjoy clean water and a healthy environment because of King County's wastewater treatment program. The county’s Wastewater Treatment Division protects public health and water quality by serving 17 cities, 17 local sewer districts and more than 1.5 million residents in King, Snohomish and Pierce counties. Formerly called Metro, the regional clean-water agency now operated by King County has been preventing water pollution for more than 40 years.