Bonneville Pacific Corp., the Salt Lake-based independent power producer, has reached a milestone in its history, according to Chairman Raymond L. Hixson.

He said the company will construct a $35 million 28.5 megawatt cogeneration plant in Watsonville, Calif., that will be the first project totally owned and controlled by Bonneville Pacific."We will be responsible for the construction, operation and, in the future perhaps the fuel. Also, this project is important to us because it represents the first application of aero-derivative technology that we will employ on future projects," said Hixson.

Annual revenues from steam and power sales from this project are estimated at $10.5 million for the first year, he said. Most of the electricity from the project will be sold to Pacific Gas and Electric under a 20-year contract.

The heat produced in the generating process, and some electricity, will be used by the thermal host, Norcal Crosetti Foods Inc., on the largest vegetable food processors in California.

The Watsonville plant will be a turn-key project constructed by MMR/Wallace Power and Industrial Inc. Engineering on the project will begin immediately with completion scheduled for May 1990. Bonneville has a similar cogeneration facility under construction at a food processing plant in Santa Maria, Calif.

Ray Walker, Norcal executive vice president, said the thermal energy will be used to provide steam for use in food processing and the electricity used for freezing and cold storage. He expects his company to be more efficient because of the power savings.