ALAMEDA — City leaders and others celebrated a milestone Wednesday when they gathered to ceremoniously put shovels into the ground on a $500 million project to transform part of the former U.S. Navy base now known as Alameda Point into housing, shops and offices.

The groundbreaking at the edge of San Francisco Bay marked the official start of construction on the first major combined public and private development since the military base closed in 1997.

“We are now moving forward,” Mayor Trish Spencer told those gathered under a tent on a spot where Navy aircraft once taxied into hangars. “We are doing the next step.”

The 68-acre project calls for 800 apartments, townhomes and condominiums. It also would open up 600,000 square feet of commercial space for development at Alameda Point. The ambitious effort also will result in 15 acres of parks and open space and commits about $2.5 million toward rehabilitating and leasing an existing 100,000-square-foot building for light industrial and specialty manufacturing.

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Alameda Point Partners, the team behind the project, has pledged $10 million toward building a new ferry terminal adjacent to where the mayor and others gathered Wednesday, an area known as the Seaplane Lagoon when the site was an active Navy base. The terminal could serve commuters crossing the bay in as soon as two years.

“After decades of planning, we are excited to begin construction on this transformative development,” said Jennifer Ott, the city’s director of base reuse and transportation. “Once complete, Alameda Point will add 800 new residential units, including a significant amount of below-market units, to our housing supply, which this area desperately needs.”

Called Site A by city officials, the area is centered around the lagoon and is bordered by Pan Am Way, West Tower Avenue and Main Street.

“Where once stood former Navy facilities and heavy industrial equipment, there will be a vibrant mixed-use community complete with apartments, townhomes, parks and space for restaurants, retail, makers, R&D and office users,” Acting City Manager Liz Warmerdam said.

As part of the first phase of the project, 130 affordable housing units will be constructed in two buildings by Eden Housing, a nonprofit affordable housing developer. One will be a “family” building with 70 units, while the second will be a “senior building with 60 units.

“We are committed to building high-quality housing that is affordable, sustainable and transit-oriented,” Eden Housing President Linda Mandolini said.

Measure A1, the $580 million housing bond that Alameda County voters approved in November 2016, is helping fund the units, Alameda County Supervisor Wilma Chan said. The rest of the project is anticipated to be built in three phases over the next 15 years. The first residential units should be complete by the end of 2019. The project is expected to generate about 2,500 construction jobs.

Alameda Point Partners includes Trammell Crow Residential, a division of Dallas-based Crow Holdings; Madison Marquette and srmERNST Development Partners, which was behind the VF Outdoor campus and the Peet’s Coffee & Tea roasting facility at the Harbor Bay Business Park near Oakland International Airport. The financial partner is Cypress Equity Investments.

“The Bay Area is in tremendous need of additional housing at all levels of affordability — market rate, workforce and affordable,” said Stephanie Hill, of Trammell Crow. “One of the mandates for this development is to build 25 percent of the residential units on ‘Site A’ for affordable and below-market-rate housing. This is higher than most cities require in the Bay Area.”