The developers looking to build tall towers near the South Waterfront now have a key supporter in City Hall.

Mayor Ted Wheeler backs a request by a Portland-based developer to lift the height restrictions for towers at RiverPlace to as high as 400 feet.

"I support it, number one, because I believe that as our city continues to grow, as the population continue to grow, we are going to need increased density," Wheeler said at a press conference on Friday. "And the best place in this city to create increased density is in the urban core."

The development company NBP Capital has been showing a project concept around City Hall that includes the possibility of 500 affordable units. Those units would be built under the city's inclusionary zoning program, which requires affordable housing be built for projects of 19 units or more, and offers density bonuses and tax breaks as well.

In downtown, the riverfront is zoned for much lower buildings. The proposed Central City plan would already raise height limits, including near the Morrison and Hawthorne bridges from as little as 75 feet to as much as 325 feet. The latest plan for RiverPlace calls for height limits of 200 feet—but NBP Capital is asking to double that.

In his press conference yesterday, Wheeler took on critics of building tall towers downtown, arguing that adding more housing in the central city can take "pressure off of the neighborhoods."

"And as you know, it is a real battle to get density into the neighborhoods," Wheeler said. "We're still doing that, but I support increased density in the downtown core."

RiverPlace is by far the largest number of affordable apartments in a single project proposed under Portland's inclusionary housing program.

The firm of the world-renowned architect Kengo Kumo is listed as the second architect for the project, in the booklet passed around City Hall to show what the project could look like.

NBP Capital, found by brother-sister team of Lauren Noecker Robert and Spencer Noecker, is majority-owned by the New York-based investment firm for philanthropist Nicolas Berggruen.

It's not clear when the development might get built, but the mayor says the ambitious proposal seems like a realistic possibility, given the people involved.

"My sense is that they're motivated," says Wheeler. "When I look at who the team is behind the project, they're not the kind of people who waste a lot of time."