Monticello Dam is a dam in Napa County, California, United States constructed between 1953 and 1957. It is a medium concrete-arch dam with a structural height of 304 ft (93 m) and a crest length of 1,023 ft (312 m). It contains 326,000 cubic yards (249,000 m³) of concrete. The dam impounded Putah Creek to cover the former town of Monticello and flood Berryessa Valley to create Lake Berryessa, then the second-largest man-made lake in California. The capacity of the reservoir is 1,602,000 acre·ft (1.976×109 m3).[1] Water from the reservoir primarily supplies agriculture in surrounding areas. The dam is noted for its classic, uncontrolled morning-glory type spillway.[1] The diameter at the lip is 72 ft (22 m). Locally, the spillway is also known as 'The Glory Hole'. [2]
The Monticello Dam Powerplant was built at the dam in 1983 and has three generators. The electrical power is sent mostly to the North Bay area of San Francisco.