In the latest setback in the construction of Orange County's Great Park, demolition crews that were supposed to tear up 600 acres of runways at the former El Toro Marine Corps base have gone home with little work completed.

Recycled Materials Co. of Colorado caught city officials off guard last month by sending a terse memo announcing it was pulling up stakes from what the company's senior project manager called "the World's Largest Recycle Project."

Lennar Corp., which is building the Great Park in conjunction with the city of Irvine, had been paying Recycled Materials for the demolition, but the housing giant has been hit hard the past year by falling home sales.

Mark Wachal, Recycled Materials' senior project manager for the Great Park, said the company completed about 2% of the runway demolition in December 2006 but had not done much since. Work had been delayed by permit requirements and an inability to secure a long-term contract with Lennar.

"We kept thinking the beginning of the project was just around the corner, the next two weeks, the next two weeks, and finally we just had to give up on it," Wachal said. "When they're ready to start working again, we hope they call us."

Starting in the early 1990s with the first rumors that the El Toro base would be closed, politicians and citizen activists spent an estimated $100 million in advertising and legal fees arguing whether the 4,700-acre base should become an airport.

The base closed in 1999. Four elections and many lawsuits later, the battle appeared to be over when Lennar bought the bulk of the base from the federal government for about $650 million. It hired Recycled Materials in June 2005.

In May 2006, Recycled Materials broke up a few feet of runway to great fanfare, and local officials were given chunks of concrete to commemorate the occasion.

The concrete was supposed to be used for the park's paths, buildings and even a planned waterfall. But the demolition work never took off.

The demolition was supposed to be completed in five years, with homes going up for sale this year and a park grand opening slated for next year. The only project that has been completed is a balloon ride and visitors center.

Lennar's Carol Wold, vice president of community affairs for the company's Heritage Fields arm, said the housing slump has prompted the company to reconsider when and where to build the Great Park homes. It does not have an estimated date for the demolition work to resume, she said.

The Great Park Corp. has spent about $49 million designing the park and establishing the balloon ride. To build much of the rest of the park, officials are depending on taxes from homes Lennar will build. Because of the delay, the park won't receive that money as soon at it expected.

The city has an incentive to keep the runways intact. It makes about $2 million each year from a company that stores recreational vehicles on the runways and car companies that pay to test-drive cars there.

Supporters of the airport idea have been watching the slow pace of the Great Park a little wistfully, knowing that those runways could be used for more than 100 flights a day.

"We knew that Orange County needed an airport, not another park, and now we're not going to have either," said Barbara Lichman, executive director of the Airport Working Group.