Drawings of a twisty track and low-slung grandstands, the promise of 1,200 temporary jobs during Austin Grand Prix race weekends and the expectation that a brand-new facility would be busy 250 days a year were among details about a proposed Formula One track released recently by City Hall.

The plans were contained in papers marked "confidential" but released in response to an American-Statesman open records request.

Most of the 20 or so pages are devoted to promoting an F1 race's economic impact on a host community. According to estimates produced by Full Throttle Productions, the Austin company that was awarded permission to host an Austin event beginning in 2012, a race weekend in Texas would pour $300 million into the area. The figure is based on attendance and spending at other F1 events.

The projections also calculate that building a track would employ 1,500-plus workers. Another 1,200 temporary workers would be hired over Formula One race weekends. About 40 employees would work year-round at the track, which would host additional races and other events.

The package appeared designed to generate support among city officials, whose endorsement of the race is crucial to qualify Full Throttle for $25 million a year for 10 years in state financial support through the Texas Major Events Trust Fund. Administered by the comptroller's office, the fund is generated by tax revenue attributable to a particular event.

A spokesman for Mayor Lee Leffingwell said the city viewed the figures included in the documents more as guidelines than hard numbers. "They gave us a frame of reference," said Matt Curtis, adding that the city planned to produce its own study.

The documents had originally been deemed off-limits to public view by city officials. Tavo Hellmund, Full Throttle's managing partner, also contended the papers contained trade secrets and thus did not have to be released. But a July 22 attorney general's decision ordered them turned over.

A spokesman for Full Throttle, Trey Salinas, wrote in an e-mail that the job projections were based on real-world comparisons of other recent F1 construction projects and "are pretty accurate based on our conversations with local contractors we have been having."

Craig Depken, an economics professor at the University of North Carolina at Charlotte who is critical of glowing economic impact projections for large sporting events, said such large job estimates can be misleading.

When it comes to construction jobs, for example, "the question is whether these people would be idle otherwise," Depken said. Temporary jobs during race weekends tend to be low-paying, he added.

The documents also detail the range of non-F1 activities Hellmund hopes to attract to the new facility when F1 is not in town. Among them: alternative-fuel automobile research, driving schools, police training facilities, concerts and "high-end auctions (i.e., Barrett-Jackson)." Scottsdale, Ariz.-based Barrett-Jackson Auction Co. specializes in car collections.

It is unclear how many of those activities would be attracted to an Austin track or are available. A spokeswoman for Barrett-Jackson said it holds auctions only four times a year, in set locations in Arizona, Florida, California and Las Vegas. "We're at capacity now," she said.

According to the papers, Hellmund anticipates hosting 400,000-plus fans at other, non-F1 racing events throughout the year, such as NASCAR, Grand Am and drag racing.

Together, racing and nonracing events will keep the facility booked 250 days out of the year, the projections say.

Keeping a track busy so many days is possible, said Eddie Gossage, president of the Texas Motor Speedway in Fort Worth, which he said has activity more than 300 days per year. But, he added, Hellmund "is going to have to work extremely hard," he said. "As a road course with no history, it's going to be tough sledding for them."

Also included in the documents are several depictions of the track to be built for an estimated $200 million near Austin-Berstrom International Airport. The drawings, by German racetrack design firm Tilke GmbH, include a view of a welcome center with rounded edges like a squashed ball and a partial view of what appears to be a multiturn track and grandstands.

The drawings and other materials are copyrighted to Full Throttle and cannot be reproduced without the company's permission. Salinas said the track depictions submitted to the city two months ago are now outdated and not appropriate for publication.

"We should have more information on that soon," he wrote.

The papers submitted to Austin officials emphasize the high prestige of hosting a Formula One event. With "global 'starpower' presence second only to the Oscars," the papers state, the Formula One race "would be the state and region's 'signature annual event.'\u2009"