SAN FRANCISCO -- An overflow crowd turned out Monday night in San Francisco for a public hearing about a controversial project at the Presidio.

More than 500 people showed up to discuss plans by Gap founder Don Fisher to build a new art museum on the former Army base. The proposed 135,000 square foot structure would hold his family's extensive collection of modern art.

Fisher and his wife, Doris, have been buying art for more than 30 years, and the collection includes pieces by Andy Warhol, Picasso, Alexander Calder and others.

The museum, dubbed the Contemporary Art Museum at the Presidio (CAMP), was proposed in 2007 by the Fisher family to house their internationally renowned collection of contemporary and modern art. The Fishers will pay for the museum's design and construction and have established a foundation to manage their collection and run the museum.

Supporters say it could be a great addition to the Bay Area cultural scene.

"We believe that anything that can keep families in the city is a wonderful asset to the city of San Francisco," said Chairman of the San Francisco School Alliance Philip Halperin. "And places that bring more art, more culture, more accessibility to the families of San Francisco is a wonderful thing."

But detractors say the building would ruin efforts to preserve the history of the Presidio itself. Organizations including the Sierra Club and the Presidio Historical Association have come out against the museum's scale, its design, and its location on the main post part of the base.

"To put sometlhing over that entire block... 60-foot tall slabs of white marble will smother it. It is not going to protect the history for future generations, " said Presidio Historical Association President Gary Widman.

It will be up to the board of the Presidio Trust to make a final decision in the matter. There's no word on when that decision might come, but Don Fisher has said he hopes to have the museum ready for the public in 2011.