Wind energy developer Iberdrola Renewables has signed a power contract to underwrite construction of an array of industrial-scale turbines along the McCain Valley of southeastern San Diego County, the company announced Wednesday.

Southern California Edison has agreed to buy electricity from up to 67 turbines located mostly on public lands managed by the U.S. Bureau of Land Management, according to Iberdrola Renewables, a U.S. division of the Spanish energy company. The Tule Wind Power project should supply enough electricity to power about 40,000 typical homes.

Terms of the 15-year power purchase agreement were not made public. The California Public Utilities Commission has to review the agreement before Edison passes on costs to its customers.

The wind farm spans 14,000 acres, north of the town of Boulevard. Major approvals and permits are in place for the first 67-turbine phase. A second 27-turbine extension may be added later.

Tule would join three nearby utility-scale wind arrays: the Kumeyaay Wind project adjacent to I-8, Ocotillo Wind on the western edge of the Imperial Valley, and Energía Sierra Juárez just across the U.S. border in Mexico. Iberdrola expects to complete construction in late 2017 on Tule.

"It's one of the few sites in San Diego County that is a viable site for utility-scale projects," said Harley McDonald, a senior business developer with Iberdrola in San Diego County. "We are very excited to finally get to construction."

The power contract is the culmination of a decade of planning by Iberdrola, starting with meteorological tests and extending through a series of federal and state environmental reviews.

Some neighbors remain opposed to the new power plant based on concerns about low-frequency noise from spinning turbine blades and other impacts on water supplies and bird populations.

"It's pretty devastating to our community if they manage to get it built," said Boulevard area rancher and environmental activist Donna Tisdale.

She and the group Backcountry Against Dumps are challenging in court zoning changes for wind energy development in unincorporated areas of San Diego County. The Tule project appears to be moving forward despite that and other legal challenges.

Iberdrola asserts that its project has more local supporters than detractors.

McDonald said the company overcame concerns about fire risks from local agencies by helping fund additional fire service and adding several water tanks at the project, along with fire-suppression systems for each turbine.

The project will employ as many as 325 during construction, and hundreds more if manufacturing and supply chain jobs are taken into consideration. It was unclear how much of the installation would be performed by visiting specialists versus local contractors. Iberdrola has yet to select a turbine supplier.

The wind farm is likely to help Edison comply with California's mandates for renewable energy, set at 33 percent of power supplies by 2020. Edison already buys power from another Iberdrola wind farm, the 45 megawatt Dillon array in Palm Springs.