Radar report fails on mitigation -- No answers to questions

A long awaited report from the US Department of Defense (DOD) fails to tackle the critical question of how interference from wind turbines on military radar systems can be mitigated, says the country's wind energy industry. "In many ways the report tells us a lot of things we already know. We do know there are impacts from wind turbines on radars," says Laurie Jodziewicz of the American Wind Energy Association (AWEA). "What we are primarily disappointed about is there is a lot attention given to what those impacts are and only a cursory mention of mitigation methods. And many of those, other than moving the turbines out of the line of sight, are pretty summarily dismissed."

The report's emphasis on potential problems paints a "somewhat dire picture" of the issue that is not reflected in the field, adds Jodziewicz. Generally, wind power developers, the military and the Federal Aviation Administration (FAA) have been able to work out solutions satisfactory to all parties. "Of the projects that were originally held up due to radar concerns in the Upper Midwest, at least the projects that we were tracking, everything that was ready to start construction in 2006 has now been cleared for approval," she says. "And those determinations were given under pretty intense scrutiny, given the amount of attention this issue has received."

The Sierra Club's Dave Hamilton echoes Jodziewicz's comments. "The good news is that there is nothing in the report to prevent the construction of new windmills from proceeding as long as proper siting and mitigation measures are taken," he says. "Unfortunately, the Department of Defense's report fails to answer its own questions about the effectiveness of mitigation measures and thus is not authoritative."

The Sierra Club had filed suit against the DOD in June to try and force it to complete the study in a more timely way. Federal legislation enacted January 6 instructed the department to submit a report within 120 days. But the 62-page study was finally released September 28, nearly five months late.

What the report says

The Effect of Windmill Farms On Military Readiness reviews a number of US and international studies and concludes that wind farms located within radar line of sight "have the potential to downgrade the ability of that radar to perform its intended function." The magnitude of the impact will depend on the number of turbines and their location, it adds. "Should the impact prove sufficient to degrade the ability of the radar to unambiguously detect and track objects of interest by primary radar alone this will negatively impact the readiness of US forces to perform the air defence mission."

The only proven methods of mitigating adverse impacts are those that avoid locating the wind turbines within the radar line of sight, the report says. Those include keeping turbines a sufficient distance away from radar, ensuring there is elevated terrain between the radar and the wind turbines, or ensuring that wind turbines are substantially below radar elevations.

Other potential mitigation methods, the report goes on to explain, are best characterised as "works in progress" requiring further development and validation of their effectiveness. Included in that category are flight trials conducted earlier this year by the UK Ministry of Defence to test two tracking technologies designed to distinguish the flight of aircraft on radar screens from similar images caused by rotating turbine blades. According to DOD observers on the scene, "both approaches showed promise, but neither was fully successful."

What next?

Wind projects in the US, says the report, will have to continue to be evaluated on a case by case basis to ensure military readiness is maintained. "However, since wind energy use in the United States is dramatically increasing, research and interagency coordination is warranted to enhance capability for completing timely determinations and developing measures for mitigating readiness impacts." The DOD, it says, has "initiated efforts" to develop additional mitigation approaches.

The question now is what the US Congress, which ordered the report, will do with it. "There has been discussion about some sort of interagency task force that might take a more comprehensive look at how all sorts of renewable energy projects are reviewed," says Jodziewicz. "I think radar concerns prompted some interest in this type of group, but there is more than just radar they want to look at."

Funding for such a taskforce is already mentioned in the current Senate appropriations bill. Action on that legislation, however, is on hold until after the US midterm elections on November 7. Through a task force, Jodziewicz says, "there might be something that can be done to make the review more predictable for everybody involved."

But beyond that, she adds, it will be difficult to get away from the kind of case by case assessment that projects now face, at least when it comes to radar concerns. "The issues are so different site to site and radar to radar. The topography can be different, little changes can make the impact different and the mitigation methods potentially different," Jodziewicz explains. "We don't know what Congress will do now that they have got this report, but it doesn't seem appropriate, and the report backs this up, to come up with some sort of blanket policy."

Not a stumbling block

With the DOD report now out, Jodziewicz does not expect to see a repeat of the kind of sweeping freeze imposed on wind projects throughout the US Upper Midwest earlier this year. The construction delays were because the study was being conducted. On March 21, the DOD and the Department of Homeland Security (DHS) issued an interim policy saying they would contest any wind installations in the "line of sight" of their radars until the study was complete. As a result, the FAA's Midwest regional office issued "Notices of Presumed Hazard" to wind projects across five states, effectively stopping work on a reported 950 MW in Illinois, 570 MW in Wisconsin and about 200 MW each in Minnesota, North Dakota and South Dakota. The FAA later relented, agreeing to move forward with project reviews and approvals without waiting for the DOD study to be finished.

Any future notices, says Jodziewicz, will likely be issued on a site-specific basis. "We will probably see other projects that will need further review for radar concerns as we have in the past. And I think like we have seen in the past, for the most part those projects will be allowed to move forward," she says. "We don't see it as big stumbling block."