A final version of the report, by BioResource Consultants of Ojai, California, is due out later this month, but its primary conclusions are unlikely to change. It finds that the number of wind turbines in a specific location -- there are about 5400 turbines spread across the hills at Altamont Pass -- is less important when predicting the number of birds killed by rotors than is the total swept area of the rotors. Repowering involves the removal of wind turbines installed in the 1980s and 1990s and their replacement by larger turbines, resulting in a reduction in the number of machines by as much as ten to 15 times. But the total swept area of the larger and more efficient wind turbines would remain the same as that of the many smaller machines, the report concludes.
The report also says that the use of tubular towers instead of the lattice towers common at Altamont does not reduce the danger to birds. "Based on these two factors, one could presume that there will be little effect on the number of bird kills in the Altamont," says Karin Sinclair of the National Renewable Energy Laboratory. How the new turbines are sited, however, could have an impact on avian deaths in the pass, she says.
Jeff Miller of the Center for Biological Diversity (CBD) says location issues are paramount. His group filed a lawsuit in January against FPL Group Inc, parent company of FPL Energy, and NEG Micon, FPL's partner in its Altamont Pass Wind Resource Center (WRC) holdings (Windpower Monthly, February 2004). CBD claims WRC turbines kill too many raptors, most of which are protected by state and federal wildlife agencies and by federal law.
Miller says the group filed the lawsuit because Alameda County's East County Board of Zoning Adjustments approved new long term conditional use permits for Altamont Pass wind farms without requiring a plan to tackle the avian mortality problem. The board finished approving all the permits in January.
"It definitely was a mistake" to build the wind farm at Altamont Pass, he says. "But that's not to suggest it should be shut down," adding: "There are some lessons to be learned from this by the wind industry." The report, he says, could have an influence on how repowered turbines come online, but during repowering the wind industry could also use it as a way to study turbine size, location and groupings to see what is lethal to birds and what is not.
Removing the most lethal turbines would be a big step, Miller says. In addition, he suggests changing grassland management and attempting to site turbines with each species of bird in mind. Some birds like the valleys and dips in the landscapes, while others, such as golden eagles, like the ridge tops. With these siting changes, he predicts bird mortality would drop 30% to 50%.
What the industry finds in its avian research in the Altamont Pass could be applied to other areas, says Sinclair. Although the research is specific to the Altamont area, "We believe the findings may have broad applications for future facilities around the world, or so we hope. In other words, proper siting appears to be key to minimising avian impacts."
Based on five years of studies and avian surveys, the report also concludes that the number of birds killed by wind turbines at Altamont Pass is twice as many as previously reported. Previous reports pegged the total deaths since the project's construction at about 10,000 birds, but the report says as many as 20,000 would be a more accurate number of bird deaths.