Fremont Siphon Replacement project continues to impact Fremont around the tunnel site at N 36th from 7 a.m. – 6 p.m. on weekdays, as the city improves the system. “The existing Siphon is nearly 100 years old and has reached the end of its of service life. The new pipes will ensure north Seattle and northern King County continue to enjoy safe, reliable sewer service for decades.”  Tunnel launch shaft construction started at the Fremont site late last week.  Here’s what’s happening now:

King County’s Fremont Siphon Replacement Project contractor is building the outer wall of the Fremont site tunnel shaft. Crews will drill holes 90 feet into the ground and replace the soil with four-foot wide concrete cylinders. The cylinders are called secant piles.

Secant piles lock together to create a watertight ring that controls groundwater. The ring at the Fremont site will be 32 feet wide. Controlling groundwater protects nearby utilities, roads and buildings from settlement. Installing the secant piles is expected to take six weeks. After the shaft is excavated, the tunneling machine will be lowered into the shaft to dig the tunnel for the new pipe under the Ship Canal. This work will increase noise and activity at the Fremont site. Drill rigs, concrete pumps and trucks will be working at the site daily. Equipment will access the site from NW 36th St.

What to expect:

  • Work from 7 a.m. – 6 p.m. on weekdays
  • Drills, pumps and trucks working on and around the Fremont project site
  • Increased noise and activity
  • Trucks entering and exiting the site from NW 36th St

Or watch the movie! Learn more by watching this short video on how King County uses secant piles to control groundwater

From Doug Marsano, Community Relations Lead, King County Wastewater Treatment Division, p)206-477-5549 c)206-423-0480\

More about the whole project here.