SEATTLE-Work got underway here this week for the 900,000-sf headquarters of the Bill and Melinda Gates Foundation, the world’s largest charitable foundation. The $500-million, full-block project across the street from the Space Needle is slated for occupancy in late 2010, nearly six years after it was first announced.

The project was first announced in January 2005, shortly after Alexandria Real Estate Equities paid $29 million for 1551 Eastlake, the 120,000-sf office building that the Bill & Melinda Gates Foundation leases for its current headquarters. Alexandria plans to re-lease the building to a life sciences operation after the Gates Foundation completes development of its new headquarters.

In March 2005, the Seattle City Council approved the $50.4-million sale of the 12.3-acre development site for the new headquarters—a city-owned parking lot adjacent to the Seattle Center—to the Bill and Melinda Gates Foundation. At that time, Foundation officials said construction of its new headquarters would commence sometime in 2007.

About $22 million of the city’s proceeds from the sale were earmarked for a 1,000-stall parking garage on the edge of the site for both the public and foundation employees. Another $10 million in proceeds was used to by the Seattle Center to pay off a debt owed to the city.

The Gates Foundation uses its $37.3 billion endowment to fight AIDS, malaria and other diseases, to provide Internet access at public libraries throughout the world and to improve public high schools in the US.