Monticello Dam is a 304ft high concrete arch dam in Napa County, California, United States constructed between 1953 and 1957. The dam impounded Putah Creek to create Lake Berryessa in the Vaca Mountains.Lake Berryessa is currently the seventh largest man-made lake in California. Water from the reservoir primarily supplies agriculture in the Sacramento Valley downstream. The dam is noted for its classic, uncontrolled morning-glory type spillway. The diameter at the lip is 72ft. Locally, the spillway is also known as 'The Glory Hole'.To the south is Putah Creek State Wildlife Area.StatisticsAlthough the dam and its 26mi long reservoir are located entirely in eastern Napa County, the dam lies less than 500ft west of the boundary with Yolo County. In addition, parts of the lake's watershed extend into Lake County.Monticello is a concrete medium thick arch dam 304ft high from the foundations, 1023ft long and 239ft above the riverbed. The dam is 100ft thick at the base, tapering to 12ft at the crest. The total volume of construction materials is 326000yd3.The capacity of the reservoir is 1602000acre.ft, with a full surface area of 20700acre. The maximum operating elevation is 440ft; any higher water levels will flow over the dam's spillway. About 375000acre feet of runoff flow into the reservoir each year from its 566mi2 watershed.
