Plans for a huge four-day music festival at the Sonoma Raceway that would rival San Francisco’s Outside Lands and Coachella in Indio got their first public unveiling this week before an overflow crowd that was fairly evenly divided between supporters and opponents.

Promoters of the yet unnamed festival hope to attract as many as 55,000 music fans a day to hear major national acts as well as local bands playing on three or four stages at the southern Sonoma County raceway, formerly known as Infineon and Sears Point before that.

“This is much like the recent BottleRock Festival in Napa,” the raceway says in its application to modify its use permit.

On Wednesday, citizens packed a meeting of the Sonoma Valley Citizens Advisory Commission in the Sonoma Police Department Community Room and spilled into the lobby to hear details of the high-profile event for the first time.

“It was probably the biggest crowd the advisory commission has seen for a while,” said Pat Gilardi, district director for Sonoma County Supervisor Susan Gorin and the county’s liaison with the commission. She counted 18 speakers in favor of the festival and 16 against it.

“There were a lot of business folks there who would interpret the expansion of the race track as good for business,” Gilardi said. “It was the neighbors who can hear the sound from the race track who expressed the most concern about noise, traffic and impact on the environment.”

Commissioners have no approval authority and took no action on the high-profile proposal, which is in its early stages. The next step will be for the county planning department to select a firm to compile an environmental impact report that will be paid for by Sonoma Raceway. The county must also approve a modification of the raceway’s use permit, which is limited to “racing and race related purposes.”

During the year, the 1,600-acre facility hosts a 340-day schedule of motor sports, including three major NASCAR, NHRA and IndyCar races.

Assuming it’s ultimately approved by the Sonoma County Board of Supervisors, the festival would begin in the spring or fall of 2017 at the soonest, according to Steve Page, the raceway’s president and general manager.

“It’s a lengthy and expensive process,” he said.

Sonoma Raceway is one of eight tracks across the country owned by North Carolina-based Speedway Motorsports. Page said the raceway filed an application for the music festival a year ago after the concept was broached by Nitro Fidelity Entertainment, a newly formed company based in Napa with plans to produce “a branded music festival” at Sonoma and four other Speedway Motorsports tracks.

“We have been approached on countless occasions by promoters who wanted to bring music to the facility,” Page said. “We never took any of those seriously. This was the first time the business proposition and the philosophy were appealing to us.”

The first of the raceway music festivals will be in August at the Kentucky Speedway. The lineup is expected to be announced in the next couple of weeks, Page said.

The festival would include overnight camping for 6,000 music fans. Bands would play from noon to midnight and a dance party tent would be open until 4 a.m.

“Talent is going to vary from festival to festival,” Page said. “One of the things we hope to do is have a strong local presence for emerging talent and local acts from Northern California as part of the music mix. There would be a lot of opportunities for the business community — wineries, restaurants and other vendors — to participate.”