In September 1945, Tacoma City Light’s Alder Dam on the Nisqually River generates electricity for the first time. The dam is built upstream from Tacoma’s first hydroelectric project at LaGrande and is part of a major expansion of the Nisqually project during World War II. LaGrande Dam is also completed this month to replace a smaller dam for the LaGrande powerhouse.
Tacoma City Light had completed a diversion dam and hydroelectric plant at LaGrande in 1912, and two dams on the Skokomish River in the 1920s. Tacoma City Light’s load grew in the 1930s and the defense buildup in 1940 projected even more demand. During World War II, Tacoma had to purchase power from Seattle and from the Bonneville Power Administration for its war industries and for the flood of new residents. The extra power was costing $1 million a year.
Alder was a concrete arch structure, 330 feet high, two miles above the smaller dam at LaGrande. The town of Alder, population 200, was inundated by the reservoir in 1944. Construction was hampered by faults in the bedrock that required more excavation than planned. The labor shortage during the war also slowed progress. The Alder Powerhouse generated 50,000 kilowatts.
LaGrande was a concrete structure 192 feet high that replaced the 45-foot diversion dam. The additional impoundment of water increased the output of the powerhouse by 80 percent to 64,000 kilowatts.
Total cost of both projects was $23.6 million, more than twice the original estimate.