Groundbreaking for a new mega-project in Downtown Seattle is slipping further back. The expansion of the Washington State Convention Center is now months behind schedule.

Developers still need two big things: money and land.

The convention center expansion project is so large – over two million square feet – it needs city-owned land, specifically, streets and alleys. But the city expects a fair exchange for the land. Developers have to show how the new buildings will benefit the public, otherwise, no city approval.

The most valuable offering is a big rooftop garden six stories above the sidewalk, accessible to the public by an elevator and one staircase. So far, that’s not enough to persuade city design consultants. Members of the Seattle Design Commission are vetting the expansion for the City Council based on how much the project contributes to the public's use of the space.

"What commissioners now need to see is how is that space being designed with the public in mind, and how can the public have the type of access to the space, physical access, that would be expected of any other open space," Michael Jenkins, commission director, said.