

NextEra Energy Resources, which operates about half of the 5,000 or so wind towers at the sprawling site straddling the Alameda-Contra Costa county line, will either swap 2,400 wind towers - some are 1980s vintage - for fewer, more advanced turbines or will stop operating the older turbines by late 2015. The company will also pay $2.5 million for raptor habitat restoration in the area.

The deal to address the long-running debate over bird kills in the country's oldest wind farm was announced Monday by California Attorney General Jerry Brown, whose office brokered the agreement between the state, NextEra, Bay Area branches of the Audubon Society and Californians for Renewable Energy. The agreement does not cover several other wind-power companies that operate at Altamont.

In keeping with recent scientific research on bird habitats, the pact requires NextEra to place the modern turbines away from ridge tops and valleys, where many of the eagles, kestrels, falcons and owls ride updrafts or hunt for prey. That provision represents a key victory for wildlife groups that say little thought was given to where the original turbines were erected.

"This is the first chance across the nation to take what was learned about turbines over the last 30 years and put it into use," said Mark Welther, executive director of the Golden Gate Audubon Society. "We support wind energy, but we need to make sure we don't sacrifice birds and wildlife to have renewable power."

The Altamont Pass, whipped by west-to-east currents that funnel cool Pacific Ocean air into the scorching Central Valley, was developed as an energy source following the 1970s oil crisis. At one point, about 5,800 turbines blanketed the 56 square miles of hills and vales along the Interstate 580 corridor, with the capacity to power hundreds of thousands of homes.

Thousands killed

The celebrated clean-energy project had a macabre environmental side effect, though, as thousands of birds died after flying into turbines' rotors each year. While there has been tremendous disagreement about the number of bird fatalities, recent research by Shawn Smallwood, a Sacramento biologist who studies the Altamont site, suggests that about 9,300 birds are killed annually, including more than 2,200 raptors.



Taller towers

The new, more efficient NextEra towers will number in the hundreds and will be taller and spread farther apart - though the rotors will be larger to produce the same amount of energy. They will be devoid of lattice-type features that became popular nesting spots on the old towers.

"They'll be much more friendly to avian species, and California will still get the same amount of renewable, emission-free energy," said Steve Stengel, spokesman for NextEra, headquartered in Juno Beach, Fla.

If NextEra - which sells its power to Pacific Gas and Electric Co. - wins approval for the first phase from regulators early next year, it will replace about 200 turbines with 59 new ones by December 2011. The company would not disclose the cost of upgrading the turbines.

The next-largest wind-energy company at Altamont is also considering replacing its older turbines, according to Mike Lynes, conservation director for Golden Gate Audubon Society. Other energy firms with smaller holdings have indicated they cannot replace their equipment due to economic reasons or property constraints.

"It's important to acknowledge that birds will continue to be killed at Altamont," Lynes said. "Wildlife agencies just have to be vigilant about ongoing impacts and address them."