Photo courtesy AGC of Washington Natt McDougall workers built a 100-foot-tall concrete tower and associated pipelines at the Swift No. 2 Hydroelectric project in Cowlitz County.

The Swift Hydro No. 2 Surge Arresting Structure was part of the overall replacement and reconstruction of the Swift Hydroelectric Generating Station. The initial project involved construction of a 100-foot-tall concrete tower and installations of a steel intake gate, trash racks, steel discharge pipeline, bifurcation valve house and two high-pressure discharge cone valves.

Major portions of the work had to be completed in less than five months during a winter season and the contract contained a $10,000 per day liquidated damages clause.

Natt McDougall workers set up an on-site pipe fabrication shop to make the 16-foot-diameter steel pipe and its 13-foot-diameter bifurcation and discharge legs in time for concrete encasement.

An innovative concept relating to pipe fabrication, concreting and work sequence was used on the detour plan for state Highway 403.

The plans called for a temporary bridge to be placed over the 16-foot pipe where it crossed under the highway, but the company was able to fabricate its pipe in lengths that allowed encasement and backfill in a sequence that switched three times, routing traffic both around and over the pipe — eliminating the bridge requirement.

There were no lost time accidents in 44,160 worker hours on the project.