Many may not be aware but the dam at Lake Almanor was constructed in the three phases. The first was the initial dam completed in 1914. That dam had to be scaled back due to financial issues. The second phase was competed in 1926.
In the fall of 1961, PG&E disclosed that it intended to raise the dam by sixteen feet and increase the storage capacity by sixty percent. The $6.7 million project began in the spring of 1962—the job was awarded to construction giant Morrison-Knudsen. As the cost indicated, this was a substantial project, as the entire dam needed to be retrofitted. A portion of this was due that there was a seepage problem since the dam was first constructed. To rectify that problem over the years, several dikes were built in front of the dam, along with other alterations. To reinforce the dam required moving of some 800,000 cubic yards of earth; 275,000 tons of rock fill, and 90,000 square feet of gunite to prevent water seepage from the increased water pressure. Work on the new improved Lake Almanor dam was completed in the fall of 1963.