Goldman Sachs Group has signed a 15-month lease extension for its 517,000-square-foot space at One New York Plaza. The reported asking rent was around $50 per square foot. The investment bank is extending its lease there until 2010, as it awaits the 2009 completion of its new headquarters at Site 26 Downtown. Goldman broke ground on its 43-story tower in November 2005. The firm plans to add thousands of new workers in the next decade to its existing base of 9,000 employees.