The Ute Indian Tribe and Bonneville Pacific Corp. have signed agreements to build a $45 million power plant and greenhouse on tribal land near Roosevelt, Bonneville spokeswoman said.

The 56-megawatt plant will be a cogeneration facility fueled by natural gas and providing electricity to Moon Lake Electric Association and heat and electricity to a 30-acre greenhouse."This cooperative venture between a sovereign nation and a private sector organization is a unique opportunity to use the tribal resources to promote economic development," said Lester M. Chapoose, chairman of the tribal business committee.

He noted the project will ease the tribe's unemployment pressures with the greenhouse employing about 120 Utes in production of high-grade tomatoes and the power plant employing 28 workers.

Under the agreement, the tribe has the option to purchase half the project in 15 years and the remaining half in 25 years.

"Revenues from the power plant operations are expected to be $12 million annually and the greenhouse operations will produce about $8 million annually," said Raymond L. Hixson, chairman of Bonneville.

The greenhouse should be completed next year and the power plant will be completed in 1991.