Hundreds of workers are struggling in two 10-hour-a-day shifts to build a huge power-generating plant in the nation's largest state, which has not built a major energy plant in more than a decade. Several such mammoth construction projects are under way in California, and energy analysts say they are essential to easing the deepening electricity crisis that has led to rolling blackouts in recent days, threatening the livelihood of businesses including Internet companies in Silicon Valley and farms in the inland valleys.