A study prompted by national security concerns involving radar will affect wind-power development in Illinois and around the country, an official for a wind energy company said Thursday.

"It's stopping the progress of literally millions of dollars of projects," said Tim Polz, site manager for Chicago-based Midwest Wind Energy. The company has two projects slated for construction in 2007 in the Bureau County region.

The study, prompted by a clause in the 2006 Defense Authorization Act, calls for an assessment of the effects of windmill farms on military operations.

The Department of Defense and the Department of Homeland Security asked the Federal Aviation Administration to monitor possible wind farm problem sites, according to FAA spokeswomen Elizabeth Isham Cory.

The FAA began issuing notices of "presumed hazard" to wind project contractors in January for sites within 60 nautical miles of long-range radar installations, she said.

The study's main purpose, Defense Department spokeswoman Eileen Lainez said, is to determine the effect wind farms have on radar systems' ability to defend the nation's borders.

"We just want to stop new construction (to find out if) it is affecting our nation's security," Lainez said. "We're not talking about the specifics of the study until it's submitted to Congress."

In McLean County, construction of the $600 million Twin Groves wind farm in Saybrook is behind schedule, but not because of federal intervention, according to a developer with Horizon Wind Energy.

Work has been delayed to finalize agreements with landowners, said Michael Skelly, chief developer with Texas-based Horizon Wind Energy. He said construction should begin the end of this month.

With 240 turbines, each 260 feet tall, planned to generate 400 megawatts, the Twin Groves wind farm will be one of the nation's largest and is estimated to provide enough power to light up 120,000 homes.

"The FAA order has affected a lot of wind projects around the country, but we got our wind permit two days ago," Skelly said Thursday. "They looked at it more closely, and (a solution) was found because we did get a permit."

The study on wind farms and radar should have been completed no later than 120 days after the Defense Authorization Act took effect in January.

Defense Department spokeswoman Lainez said she does not know when the study will be completed.

Polz said he hopes the study will be concluded soon, because without a resolution, his company cannot begin building the farms, which include a second phase of the Crescent Ridge wind farm near Tiskilwa and a new 200- to 250-megawatt Big Sky wind farm near Ohio.

Polz said his company is moving forward with both projects, but added that it's possible - if the study shows the turbines do cause interference - the FAA could shut projects down.

Other planned projects in the area include the 64-megawatt Eurus Crescent Ridge II wind farm near Tiskilwa, and an 84-megawatt GSG LLC wind farm in LaSalle and Lee counties near Mendota owned by Bruce and Joyce Papeich.

Michael Vickerman with Renew Wisconsin, a not-for-profit wind farm advocacy group, said four large-scale wind farm projects in Wisconsin are delayed because they are near airports. He said instances have been documented in which test planes lost radar for "a handful of seconds" while flying over a wind farm. But technology is now available to eliminate interference caused by objects such as cell towers and wind turbines, Vickerman said.

"It's absurd," Vickerman said. "There are wind farms operating near Air Force bases." Vickerman said contractors will have to delay buying turbines, and the high demand for turbines will increase prices by 20 percent next year.

"The economic damage is widespread from this policy. Just about everyone suffers," Vickerman said.

Polz added there are already wind farms within the area of facilities using military radars.

"So they should already know the effects," Polz said.

"We would hope, along with everyone else in this industry, what they come out with is reasonable," he said.

Andrea Frampton and Erinn Deshinsky can be reached at 686-3041 or state@pjstar.com.