Culmback Dam Water Temperature Conditioning Phase 2

Project Summary

The project involved tunneling into solid rock on the side of the existing Culmback Dam and building a 700-foot water conveyance tunnel to tie into the existing power water tunnel that conveys water to the powerhouse.  400 feet of the tunnel is open and conveys water within its walls to the concrete tunnel plug. Beyond the plug, conveyance pipe ranging in size from 24 inches to 72 inches, now conveys the water through the remaining 300 feet of tunnel and out into the creek.  The new conveyance pipeline connects into this system and sends water from the power water tunnel to the creek to increase the water temperature.  This new water line allows us to take water from varying levels of the lake above, down to the stream below. Red Path was our subcontractor who tunneled through the dam via drilling and blasting methods.



Sultan, WA


Snohomish County PUD

Contract Amount



August 2017 - October 2018

Project Highlights

The work was located at the bottom of the dam, with limited access, and 450 feet down a 28 degree slope. IMCO worked internally with our safety, management teams, and outside engineers to develop a safe and efficient access route down the slope.