News and analysis about energy in California with an eye toward renewables.

Agency Staff: 'Hidden Hills Solar Will Kill Eagles'

Golden eagle | Photo: kamerakamote/Flickr/Creative Commons License

ReWire reported on Monday on the dispute between the California Energy Commission (CEC) and BrightSource Energy over the risk to wildlife from the concentrated solar energy at BrightSource's proposed Hidden Hills Solar Electric Generating System, and we promised you an update on CEC scientific staff testimony when the transcript of a particularly groundbreaking hearing was made available. CEC made that transcript available today, and it's a doozy. According to CEC scientific staff, the Hidden Hills project will "almost certainly kill or injure" eagles and "other special status" species of birds.

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The hearing, held thursday March 14 in Shoshone, covered threats to birds from the facility's concentrated solar energy directed at boilers atop 750-foot tall towers by thousands of mirrored heliostats. As we mentioned Monday, concentrated "solar flux" can injure birds if it raises the temperature of their feathers past 160°C, at which point the keratin protein in those feathers begins to denature. As birds rely on their feathers not only for insulation and camouflage but for their ability to fly, damaging those feathers can cause serious harm to the bird that wears them -- either immediately, as the bird finds itself unable to fly at 1,000 feet above the ground, or more slowly due to more subtle impairments in speed and agility.

With the information we had available yesterday, we wrote that CEC staff had proposed a safety solar flux exposure threshold one tenth what is being advocated by BrightSource, saying that the firm's proposed 50 kilowatt-per-square meter (kW/m2) limit, 50 times the intensity of unaugmented sunshine, should be cut down to 10 kW/m2. That intensity threshold would mean that birds flying into a danger zone about 2,000 feet wide around each tower at Hidden Hills would run the risk of injury from solar flux.

That was before we saw the transcript of the March 14 hearing. According to the transcript, CEC staff actually advocates a 5 kW/m2 threshold, one-tenth what was proposed by BrightSource.

As one might expect, there's tension between BrightSource and the CEC staff on this and related matters. Here's how the CEC's Rick Tyler, a senior mechanical engineer with the California Energy Commission, started his hearing testimony on March 14. After introducing other CEC staff and experts who'd be offering testimony, Tyler said:

One of the overarching disputes between staff and applicant goes to analytical approach. Risk assessment is a widely accepted method to evaluate this type of risk and Exhibit 301 [quoted in ReWire's piece Monday] provides reference to one of State of California's guidelines for conducting ecological risk assessment. These and many other state, federal, and international guidelines provide direction on accepted practices and procedures for conducting such ecological risk assessments.

Staff's analysis conforms with these guidelines while BrightSource's does not. BrightSource contends that the use of dose response concepts and risk assessment are not appropriate and that the assumptions made by staff are either incorrect, wrong, conservative, or should have utilized average or median assumptions. This could not be further from the truth.

Artist's rendition, Hidden HIll solar plant | Image courtesy California Energy Commission

After a bit of a technical discussion of risk assessment and an introduction to staff's assumptions about modeling the complexities involved in how birds and their feathers interact with the air and solar flux, Tyler continued:

Staff believes that it's a near certainty that golden eagles and other special status bird species will be killed or injured over the 30-year life of this project, while BrightSource contends that golden eagles will not be killed or injured and that the flux field and the impacts to birds in general will be insignificant. Staff contends that eagles and significant numbers of other special status species of birds will be killed or injured from exposure to the flux field and concludes that the killing or injury of even one fully protected or endangered species such as the golden eagle would constitute a substantial change or impact on the environment. [Emphasis added.]

As for the safe threshold level of exposure to the solar flux, Tyler was unsparing of the scientific claims of BrightSource and its contractor CH2M Hill, based on CH2M Hill's experiments with dead birds photos of which have been kept from the public by BrightSource:

BrightSource contends that the safe exposure threshold is 50 kilowatts per meter squared based on experiments conducted by [CH2M Hill's] Mr. Santolo for BrightSource... However, these experiments cannot support BrightSource's contention of a safe threshold at 50 kilowatts per meter squared. The term threshold within the context of risk assessment has a very specific meaning. It implies that that level of exposure would cause no adverse effect whatsoever and that the exposure would leave no residual damage and that repeated exposures to that same level would not accumulate damage.

The fact is that the evidence from the photographs provided documenting this experiment indicate that there was carbonization of the end of the feathers which is a very, very serious end of the dose response spectrum and that in fact repeated exposures would result -- that there is residual damage as a result of it and that repeated exposures would accumulate damage.

So this cannot be considered a no-effect level. Based on standard risk assessment methods and assumptions and practice, it would be necessary to divide that flux level that caused that kind of damage by a factor of ten at a minimum. It is an adverse effect. It's not a no-effect level. It's an adverse-effect level. And so the interpretation of that data is what's really wrong. It cannot be used to support the concept of a threshold or a safe exposure threshold.

After some discussion of the dimensions of the solar flux field that Hidden Hills would create and the speed at which birds would likely fly through that field, Tyler concluded with a bleak assessment of Hidden Hills' likely deleterious impact on golden eagles and other birds, and a reminder that not all fatal injuries caused by the solar flux would show up right away:

Based on the hazard posed by the concentrated field and the presence of eagles in the area, staff concludes that eagles and other special status bird species will almost certainly be killed or injured by exposure to the flux field.

I'd like to just take a minute and explain something as a risk assessor that I think is very important. Risk assessors routinely rely on morbidity or death. The reason is morbidity or death is very clear. It's not ambiguous. You're either dead or you're not dead. When you start talking about morbidity or injury, that's much more subjective. But any risk assessor should realize and anybody looking at a risk assessment should realize that anytime you have fatalities you also have significant numbers of injuries. And the injuries are usually several times as large as the number of fatalities and those injuries can actually lead to late fatalities that aren't detected by the surveys that we've talked about.

So the bird lives for a while, flies off site, and dies later or it never reproduces or any number of other impacts that could occur, but I think it's really important to recognize that the actual number of injuries will be several times as large as the number of fatalities. Staff contends that killing or injuring even one golden eagle would constitute potential for substantial impact on the environment and over the life of the Hidden Hills project would cause a significant impact on avian resources.

That phrase "significant impact" is, well, significant. Under the California Environmental Quality Act (CEQA), the CEC would have to deliberately override the provisions of CEQA to approve Hidden Hills if any of the project's environmental impacts are found to be "significant." The CEC is no stranger to overriding CEQA provisions: They've done so for many of the desert solar projects they've approved so far. But the Commission has taken heat for it, and BrightSource increasingly seems the least favored solar developer among California regulators. The company has been slapped down by the CPUC of late, for instance. If there's a single developer for whom the CEC's commissioners might be tempted not to override CEQA, BrightSource is likely that company. And having the CEC fail to approve Hidden Hills would be one more setback for a company that's already had one setback too many.

So as you might expect, BrightSource -- whose very existence might actually be threatened by the solar flux and birds issue -- objected to this line of testimony. We'll discuss BrightSource's answers to CEC staff in Part 3 of this series.


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About the Author

Chris Clarke is a natural history writer and environmental journalist currently at work on a book about the Joshua tree. He lives in Joshua Tree.
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