In downtown San Francisco, cranes and machinery are clanking away on a construction site just south of Mission Street. They are working on the new Pelli Clarke Pelli'designed Transbay Terminal and surrounding buildings, the city's entr'e into high-density, transit-oriented development. The transportation hub and its 1,070-foot sky-piercing Salesforce Tower aren't due to be completed until 2017, but in the meantime, other parts of the 145-acre redevelopment area are starting to take shape. Located at the southernmost border of the district is the first new residential building, the Rene Cazenave Apartments. Its 120 units provide supportive housing for the chronically homeless and help satisfy the city's requirement that 35 percent of the approximately 4,500 apartments in the new neighborhood be affordable for very low- to moderate-income households.