Control of the River

The physical realization of the McNary project was accomplished in five basic steps related to the manipulation of the river during construction. The first two steps were taken by the Portland District prior to establishment of the Walla Walla District, so the project was a “going concern” on 1 November 1948. The initial step in 1947 had been excavation for the navigation lock area on the north shore, an access road, and some railroad work, all of which could be accomplished without disturbing the river.

. . . The second step was the large north shore cofferdam enclosing d major portion of the spillway and all of the north shore structural facilities including the fish ladder, fish lock and non-overflow section. The cofferdam was completed on 2 May l948, just in time to receive the

second largest flood of record which peaked on 30 May, overtopping the cofferdam. Repairs were made, the cofferdam pumped out, and work proceeded later that summer on excavation within the cofferdam. Actual construction of the dam got underway on the north side late that fall after the project was turned over to the new District. The first pour of concrete took place early that winter. It was made with appropriate ceremony on a Friday afternoon late, and the weather promptly turned bitter cold with one of the coldest weekends of the year. Some of the concrete was removed the next week and the structure started again.

The third basic step in the building process was the so-called junior cofferdam on the south shore to start construction of the south shore fish ladder and a portion of the powerhouse, still leaving an adequate channel open for the river. The fourth step involved the construction of the major south shore cofferdam, closing the river channel, forcing all of the river flow to the north through low spillway bays left incomplete to accommodate this move. The major portion of the powerhouse and nine sections of spillway were then constructed within this cofferdam.

The final step was to remove the fourth step cofferdam and again divert the river to the south through skeleton powerhouse bays while the low spillway bays were completed. As soon as they were finished the pool level behind the dam was raised and lock and power units placed into operation. All that then remained was to dedicate the project (a major undertaking when the President of the United States does the honors) and complete the details. Those seven years of work, however, were fraught with many decisions, anxious moments, major accomplishments in terms of structural features and work programs, and several heartaches, since 2 men lost their lives in building the structure and the relocations involved.