Weber Siphon Project

The Project

After securing a new source of water from the Lake Roosevelt Storage Releases Project, OCR faced a new challenge: There was no way to deliver it to the southern part of the Columbia Basin. Interstate 90 was the problem. There was only one point, the Weber Siphon Complex, where water from the Columbia Basin Project passed under I-90, and it wasn’t large enough to handle the additional flow. A second siphon would be required.

The U.S. Bureau of Reclamation (Reclamation) had piping in place under I-90 at the Weber Siphon Complex. It just needed to be connected with the rest of the system. OCR contributed $800,000 for the design and worked with Reclamation and Washington’s congressional delegation to get stimulus funding for construction.

As part of the Lake Roosevelt Storage Releases Project, OCR will deliver at least 21,000 ac-ft of Lake Roosevelt water through Weber Siphon once it is finished. The siphon has the capacity to deliver much more water when new water supplies are developed

Expected Outcome

The water delivery bottleneck at I-90 is eliminated, allowing water from the Lake Roosevelt Project to be delivered to the southern portion of the Columbia Basin.

By the Numbers

  • Capacity – 2100 cfs
  • Diameter – Inside 14’8” Outside Up to 18’
  • Length – 8287 ft
  • Yards of Concrete – 60 cubic yards per 25 ‘ section
  • Pounds of Rebar – 30,000 per 25’ section or 6.5 million pounds
  • Dirt Moved – 266,000 cubic yards.

More Information





Double-click on photo for a description of what is depicted. Photos courtesy of U.S. Bureau of Reclamation



Grant County


Economic Benefits*

  • 543 Jobs Protected
  • $38 Million in Annual Income Protected

*Assuming 21,000 ac-ft of Lake Roosevelt Project water (could be increased to as much as 30,000 ac-ft) will pass through Weber Siphon. Economic benefits increase as more water from other sources is secured.

How we calculate economic benefits.