At Fifth and Mission, the development company behind the 5M project that has helped the Chronicle lease out the unused square footage of their offices is ready to move to the next phase of the development project: Turning the Chronicle building in to something other people actually might want to visit.

So far the 5M project has been called a success β€” Besides the paper of record, much-hyped payment startup Square has their offices there and their most recent valuation made them worth around $2 billion. They've also got a parklet and food trucks down there. It's San Francisco in a nutshell, basically.

The goal of the next phase, according to the Business Times, is to create a new "central social district" at the nexus of the hopefully-cleaner-soon Mid-Market area and the more formal arts district around Yerba Buena. (Charitably, the developer calls Mid-Market a "less formal arts district". Whatever that means. At the very least, they'll be looking to fare better than the Federal Building a few blocks away.)

Phase 2 originally called for razing the Chronicle building entirely, but the new plan is to keep the old girl intact for the office space. Or as Alexa Arena, the project lead for developer Forest City, put it in urban planning-speak, the Chronicle building "creates the diversity of users and diversity of form and bridging between the new and the old." Plus it adds that subtle air of authenticity, if you will.

All told the project will be 1.3 million square feet of commercial space with 700 housing units spread over the four-acre site. About 35,000 square feet will be reserved for open space and 22,000 of that will be a park on the roof of the Chronicle building. (Beware: it's infested with bees up there.) The project, which was just filed with the planning department today, should be approved by 2014 and construction is projected to go for a whopping nine years from 2015 - 2026.

In the meantime, cue the gentrification concerns: at least one land-use lawyer has already weighed in, fearing that the new development will take away an area that has been "a resource for low-income people". And let's try not to think about what happens if the city decides to give a tax break to keep the high-value tech businesses there.