 Excavation of the dam site and construction of a diversion tunnel continued through 1954, with the first concrete placed on August 9, 1955.Despite major flooding between January and May 1956, more than 90 percent of the concrete had been laid by December 1956, and the dam was topped out on November 7, 1957, at a total cost of about $37 million.This figure also includes the cost for associated downstream irrigation works and the highway relocation.