An early vision of the Civic Square plaza as seen from Seattle City Hall.

Just a couple of blocks from Seattle’s award-winning library and City Hall, a fence of plywood surrounds the city’s last undeveloped downtown city block. A gaping hole in the ground, the site was once home to the city’s Public Safety Building, which was demolished in 2005 to make way for Seattle Civic Square. The cornerstone of the city’s 10-year Civic Center Master Plan, the estimated $300 million project includes a high-rise office and residential tower, a public plaza, retail space and underground parking. A new light rail line connecting downtown Seattle to the Seattle- Tacoma airport is slated to run directly underneath the square.

The design team, which the city selected in February 2007, includes Seattle developer Triad, London-based design architect Foster + Partners, Seattle architecture firm GGLO, engineering firm Arup and landscape architect Atelier Dreiseitl.

In August, the city passed a resolution to sell the block to Triad for $25 million. In exchange, the developer must deliver the public plaza and 36,000 square feet of retail space to the city. The mixed-use tower is expected to include 600,000 square feet of commercial office space with 182,000 square feet of residential on top of it, according to Triad’s Bill Krippaehne, the managing director of the project.

The Seattle Civic Square Group is still undergoing early design guidance with both the Seattle Design Review Board and Seattle Design Commission — a unique requirement, according to many. The project is currently aiming for a Gold rating from the U.S. Green Building Council’s Leadership in Energy and Environmental Design (LEED) Core and Shell program. Despite the team’s substantial sustainability credentials, the project has faced challenges designing a Platinum-level package, according to some observers.

“With a substantial mixed-use project, sometimes the criteria doesn’t really fit; you have to force the fit to get the points,” Krippaehne says.

“There are some things that we will likely consider that might not get us any points at all, but they make a lot of sense for the project.” Design elements being considered by the team include using an existing concrete subterranean garage as a big heat sink that could serve as a radiator for the entire building; laminating photovoltaics into the curtain wall of the building; harvesting rainwater to generate electricity via microturbines; and reusing graywater.