Rep. Martin J. Walsh, center, spoke during a forum at the Kroc Center on Dudley Street on Tuesday evening. He is flanked by candidates Charlotte Golar Richie, left, and Charles Clemons, right. Photo by Eric Esteves

With four months left in his term, Mayor Thomas Menino is looking ahead to 2020: His administration has unveiled a blueprint for building 30,000 units by that year, representing a $16.5 billion public and private investment.

“Some of these polices can be put in place in 2013, while others will need to be evaluated and adopted by a new administration starting in 2014,” the 48-page plan noted.

The city grew by 20,000 new housing units in the last decade, according to the plan report, 30 percent of them affordable. Looking ahead, the city’s job force is expected to gain 100,000 new jobs by 2020. “Those jobs, combined with a rising preference of workers to live in the city rather than the suburbs, are expected to generate demand for 28,000 new units,” the blueprint reported. “The primary growth demographics are expected to be empty-nesters and seniors; 20-34 year-olds; and downtown families.”

Other challenges include a risk to the city’s affordable housing stock due to declining federal funding and the large number of college students, 27,000 in total, living off campus.

The Menino administration hopes to keep pushing community-vetted projects through the development pipeline up through the end of 2013. The blueprint notes that there are 5,332 market-rate units under construction, 9,112 units approved but not yet permitted, and 3,600 units awaiting approval from the Boston Redevelopment Authority. A new homebuyer assistance program will be launched as well.

The blueprint also says the administration will create “targeted middle class development opportunities” through disposition of public land and “manage the tax foreclosure process to prioritize the acquisition of distressed and underutilized sites that can be turned quickly into tax-paying, middle income housing development sites.” The next administration should update the city’s zoning code and focus on housing the middle class, the blueprint adds.

The plan, laid out on Monday at City Hall, drew mixed reviews from the candidates who hope to succeed Menino in January.

During a televised debate put together by the Boston Herald and New England Cable News, Dorchester state Rep. Marty Walsh said the mayor should slow down as January draws closer, while Codman Square Health Center co-founder Bill Walczak, who has clashed with Menino over an East Boston casino, said, “Just stop.”

Others, like former state Rep. Charlotte Golar Richie, who once served as Menino’s housing chief, backed the mayor, who brushed off their pleas, chalking them up to politics. “I worked with a group of housing advocates,” he said. “Myself and them shaped this whole report. It’s not something that’s a political report. It’s a housing report that helps working people get a job and a place to live in the city. That’s what this is all about. Everything doesn’t have to be political. It’s about housing, a desperate need in our city. And I’m going to continue to advocate for that and work on that.”

John Barros, who has taken a leave of absence from his job as executive director of the Dudley Street Neighborhood Initiative to run for mayor, said the mayor’s plan is “headed in the right direction.” But he added that he was concerned about its mention of the disposition of property. Barros said it needs to be “embedded in the planning process” before it’s sold. “I’m worried about that part of it,” he said.

Walsh told the Reporter that he isn’t asking the mayor to stop doing his job, but he said he was concerned about discussions and expectations falling on the next the mayor. Walczak said his major issue with the mayor is the casino that Menino supports building at Suffolk Downs. Calling them a “public health disaster,” Walczak opposes casinos. “All I’m saying is do not commit to long term issues for the next mayor,” he said.