Figure 14. Diablo Canyon Nuclear Power Plant, operated by Pacific Gas & Electric Company, has 2 units on 750 acres in San Luis Obispo County, California. Construction of the units may have been the longest in U.S. history, at 15 and 16 years, due to regulatory concern for its ability to withstand seismic activity. Operation began in 1984. The combined capacity of the two units is 2,160 net MWe. Cooling water for the units is obtained from the Pacific Ocean.