Department of Defense Issues Report on Effect of Windmills on Radar

November 23rd, 2006 - by admin

Green Power Magazine – 2006-11-23 00:12:45

The Department of Defense (DOD) made public its long-awaited report entitled “The Effect of Windmill Farms On Military Readiness.” The report concluded that wind farms located within radar line of sight of an air defense radar have the potential to degrade the ability of the radar to perform its intended function. The magnitude of the impact, according to the report, depends upon the number and location of the turbines.

The report resulted from a last-minute amendment to the National Defense Authorization Act for Fiscal Year 2006, enacted January 6, 2006, in which Congress mandated that the Secretary of Defense submit a report to Congress on the effects of wind farms on military readiness, specifically whether wind facilities interfere with military radar.

The amendment also required the Department of Defense to report on technologies that could mitigate any adverse effects on military operations. The report was due within 120 days after the amendment of the Act.

Pending the completion of the report, the Department of Defense and the Department of Homeland Security Long Range Rader Joint Program Office adopted an Interim Policy on Proposed Windmill Farm Locations, issued March 21, 2006.

The Interim Policy stated that the office will contest any establishment of windmill farms “within radar line of site of the National Air Defense and Homeland Security Radars.” The policy was to remain in effect until the completion of the report and its publication in the Congressional Record.

In response to the policy, the FAA began issuing “Notices of Presumed Hazard” to wind projects located within 60 nautical miles of long-range radar installations. At least twelve projects in Illinois, Wisconsin, North Dakota, and South Dakota received these notices, placing a de facto moratorium on construction.

The FAA’s actions have the potential to delay future wind projects. According to a statement issued by Senator Durbin of Illinois on June 2, the “overwhelming percentage of land in this country is classified as within the ‘radar line of sight’ and possibly obstructive.” The FAA’s actions could therefore affect wind farm development across the country.

The DOD’s September 27,2006 report evaluated several mitigation measures aimed at avoiding or eliminating impact of windmills on air defense radar. The Department defined mitigation as “either an approach that completely prevents any negative impact from occurring” or an approach that sufficiently reduces any negative impacts so that “there is no significant influence on the capability of air defense or missile warning radar.”

The report found that the only proven mitigation measure to completely prevent any degradation in primary radar performance of air defense radars is called “line of sight mitigation” – avoiding the placement of wind turbines within air defense radar lines of sight. Line of sight mitigations may be achieved by employing
1) the “bald earth” approach, achieved by increasing the distance between air defense radars and wind turbines;
2) terrain masking; or
3) terrain relief.

The “bald earth” approach is employed in areas where the landscape is fairly flat, and the wind turbines are places at a great enough distance from the air defense radar to be out of its line of sight. Alternatively, terrain masking occurs when elevated terrain is located between the radar and the wind turbines, and the turbines are “masked” by the terrain. Finally, terrain relief, a variation of terrain masking, can be employed when the elevation of the radar is significantly greater than the elevation of the wind turbines.

Currently, these are the only approved mitigation measures to eliminate wind turbine interference with air defense radar. The Department has initiated research to develop and test additional approaches, but these approaches will require adequate testing and validation before the Department will approve them.

Siting Requirement
The report concluded that case-by-case analysis by both the Federal Aviation Administration (“FAA”) and the Department of Defense/Department of Homeland Security Long Range Radar Joint Program Office (“JPO”) is necessary to assess potential impacts on local air defense systems to determine if a propose wind farm could compromise radar capability.

Therefore, a project proponent must apply to the FAA for a hazard determination prior to construction of any windmills. Additionally, a project proponent must also work with the JPO and its informal consultation program, which is aimed at assisting project proponents in identifying locations where radar line of sight concerns exist.

Additionally, the report notes that specific Department bases and installations are assigned management responsibilities for specific sections of airspace. Wind developers should continue to work with local base and installation managers to eliminate impacts to potentially impacted facilities.

The report also noted that the FAA has the responsibility to promote and maintain the safe and efficient use of US airspace for all users. The Department thus deferred to the FAA regarding possible impacts wind farms may have on air traffic control radars that are used to manage the US air traffic control system.

In order to avoid delays in project development, as well as to avoid unnecessary investigation expense, wind project proponents should first consult with the FAA, Joint Program Office, and the local DOD installation about the siting of their project. This should be a preliminary step in the development process.

Early consultation with the FAA and JPO will allow project developers to evaluate whether their project site may potentially interfere with air defense radar and determine whether mitigation is necessary and possible.

Further, an FAA determination should be sought as early as possible in the development process. Such determinations are obtained by submitting a “Notice of Proposed Construction or Alteration” to the Air Traffic Division Manager of the FAA Regional Office having jurisdiction over the site’s area, as well as the local JPO office.

Posted in accordance with Title 17, US Code, for noncommercial, educational purposes.