Don Pedro Dam

The Don Pedro Dam, since 1971 also known as the Old Don Pedro Dam, was a dam across the Tuolumne River in Tuolumne County, California. The structure still exists and is flooded underneath Don Pedro Reservoir, which is formed by the New Don Pedro Dam.

Construction
It was a solid concrete gravity dam that was 283 ft high, 1000 ft wide, 16 ft thick at the crest, and 170 ft thick at the base. It was completed in 1923 where the Tuolumne River had carved a narrow gorge with walls of solid rock about a mile (2 km) below Don Pedro Bar. The reservoir created by this dam contained 290400 acre.ft of water when full, 14.3% of today's capacity.

A 15 megawatt power plant was part of the dam's original design, and two more 7500 kilowatt generators were added in 1926 for 30 megawatts total, just 15% of today's capacity. The old dam still exists about 1.5 mi upstream from the new 1971 dam, and since the old dam topped out at just 580 ft above sea level it is now under some 250 ft of water when the new reservoir is full.