Culmback Dam Fish Habitat Improvement

This remote project improved fish habitat in the Sultan River, enhancing productivity and survivability for both local and anadromous fish species. The work included tunneling into solid rock at the side of Culmback Dam and constructing a 700-foot water conveyance tunnel that ties into the existing power water tunnel. The first 400 feet of the tunnel directs water to a concrete tunnel plug, while the remaining 300 feet conveys water through pipe ranging from 24 to 72 inches in diameter before discharging into the creek. A new conveyance pipeline connects to this system, diverting water from the power tunnel to the creek to increase water temperature. The waterline is designed to draw from varying levels of the lake above and deliver flow to the stream below. 

Limited access shaped every aspect of the project. The worksite sat at the base of the dam, 200 vertical feet down a 450-foot, 26-degree slope. Cranes were required to move all materials and equipment to the bottom. The technical tunneling scope demanded an experienced hard-rock tunneling subcontractor. Despite the extremely tight workspace, crews successfully carried out steel pipe installation, portal improvements, complex material and personnel logistics, and coordination among multiple subcontractors.