WASHINGTON – Falling power prices, turmoil in the energy industry and concerns about state involvement in the electricity market have slowed the development of power plants in California, according to a congressional study released yesterday. But state officials disputed some of the report's assertions, saying dozens of plants had come on line or were in the works. Fifty-nine proposed power plants, representing 11,500 megawatts of generation, either were canceled or postponed as of December 2001, according to the General Accounting Office, the investigative arm of Congress. A megawatt can power 750 to 1,000 homes. But Steve Maviglio, a spokesman for...