This 12-foot high diversion dam was built in 1936 to provide water to the downstream Issaquah Salmon Hatchery. The dam provided an inadequate, steep, narrow fish ladder which severely restricted fish passage to 11 miles of upstream habitat. It was common for salmon to become stranded and die at this impasse during low flows. In other cases, adult returning salmon would give up, turn around and go downstream.

The 2005 Chinook Salmon Conservation Plan for WRIA 8 identified this dam as a significant barrier, and at that time the Army Corp of Engineers proposed to build a replacement dam and fish ladder. Those discussions did not move forward. In 2008, Washington Department of Fish & Wildlife partnered with the City of Issaquah and hired engineering consulting firm AMEC to take on the challenge to develop a better solution to continue to provide water to the hatchery while allowing easy passage for salmon.

The solution:

  • a series of 13 boulder weirs, which mimics natural conditions and provides a gentle, easily-passable incline for salmon.
  • a water intake structure (to continue to provide water to the hatchery downstream) which provides unobstructed fish passage and a low-maintenance design. (DOES IT SCREEN FOR JUVENILES?)

Additional restoration features:

  • Replace invasives with native riparian vegetation, which Mountains to Sound Greenway Trust will continue to monitor moving forward.
  • Large, in-stream woody debris to provide habitat and stream diversity.
  • Improved fish passage to Cabin Creek, which enters the creek at the site.

Pre-Construction Discussion of the Project

Post-Construction Discussion of the Project

Total cost of the project: $4.8 million