In a press conference this afternoon that didn't include much, if any, new information about his Vulcan-backed proposal to increase building heights and density in South Lake Union, Mayor Mike McGinn told members of the press (plus a strong contingent of activists, including likely McGinn opponent and former city council member Peter Steinbrueck) that any "delay" by the city council, which must approve the proposal, "means we reduce the public benefits" provided through incentive zoning, a program that requires developers to provide public benefits like affordable housing, childcare, and open space in exchange for greater heights and density.

Any "delay" by the city council, which must approve the proposal, "means we reduce the public benefits"—Mayor McGinn McGinn's point was that the longer the council puts off approving his upzone, which would allow towers as tall as 400 feet in the neighborhood (stepping down toward Lake Union, where towers as tall as 240 might be permitted), the longer developers will be able to build under existing rules, which allow more lot coverage (buildings could cover up to 75 percent of a single block, compared to about a sixth of a block under McGinn's proposal) and don't require incentives.

"If we [keep] the existing zoning, those blocks will get built out with shorter buildings [that] occupy more of the block and we won’t get the public benefits or maximize the job or housing opportunities," McGinn said. "We need to have a plan to accommodate the type of growth that we're [expecting]. ... These developments could go somewhere else—some other part of the city, or some other city" if Seattle doesn't act to accomodate them, he added. 

The council, of course, includes at least one and possibly two members with a strong incentive for making sure McGinn doesn't get a "win" on South Lake Union—Tim Burgess, who has already declared his candidacy for mayor, and Bruce Harrell, who is rumored to be considering a run.

Burgess has expressed interest in going even further than incentives in South Lake Union and perhaps mandating inclusionary zoning, which would require developers to build a certain number of affordable units in their buildings. Steinbrueck, meanwhile, opposes the proposal altogether, arguing that it would block views and light and would not provide meaningful public benefits.

McGinn and city planning Marshall Foster defended their South Lake Union plans against criticisms that they allow buildings that are too tall, that they would block views and cast unsightly shadows on sidewalks and public parks, and that the buildings' "podiums"—large bases on which the narrower tall towers would rest—take up too much space on the ground. 

"What we're doing is ensuring that we have a great street-level environment," Foster said. "You have to be careful—you can have too much open space [on blocks with residential or commercial development], too."