Ballard Siphon replacement project

Design options

Early analysis ruled out some possible replacement options - for example, simply laying new siphons on the bottom next to the existing ones. That method could involve a lengthy permitting process, affect tribal fishing rights, require working around salmon migration periods, and stir up sediments during construction.

The design team also looked at horizontal directional drilling and microtunneling methods to install replacement pipes beneath the floor of the Ship Canal. These tunneling methods would avoid construction within the waterway and decrease permitting and sediment issues. These methods were ruled out because of their risks and potential impacts on the neighborhood and businesses.

The current design focuses on slip-lining new plastic pipes inside the existing siphon barrels and constructing a deep shaft tunnel some 60 feet beneath the bottom of the canal, with new below grade connection structures at both ends of the tunnel. Design and construction of the Ballard Siphon Replacement Project will not be easy. Space is limited by underground utilities, railroad tracks and businesses on both sides of Salmon Bay. The project team will continue to work with business owners, community leaders and residents to identify concerns and develop plans to minimize impact.

Conceptual profile

Ballard Siphon Project Conceptual Profile.
Also available as PDF file.