The next construction start on the island
The Treasure Island Development Authority's upcoming-development notice, last updated 14 September 2026, lists the island's next construction start. It is a behavioral health building at Parcel E1.2, valued at $70 million, with an estimated start in November 2026 and an estimated finish in July 2028.
The notice names Mercy Housing and the San Francisco Department of Public Health as developers, Cahill as general contractor and a 41 percent small business enterprise participation goal. It records the project as 240 treatment beds and supportive housing.
The notice's own preface states that the dates and values are projections, are not guaranteed, and are subject to change.
What the developer publishes
Mercy Housing California issued a special inspection request for the building on 4 August 2026. It describes new construction of a 120-unit, 100% affordable residential step-down facility, a turnkey development to be owned by the San Francisco Department of Public Health.
That document puts the start of construction at 2 November 2026 and the anticipated completion at December 2028. It names Cahill Contractors as general contractor, Gensler and Paulett Taggart Architects as the architects, and DCI Engineers as structural engineer.
Two published counts cover one building. The authority counts 240 treatment beds. The developer counts 120 residential units.
The beds the city counts
The Mayor's Office announced $14.2 million of Proposition 1 funding on 12 March 2026 for 44 residential addiction treatment beds inside a new city-owned behavioral health facility on Treasure Island.
The same release describes the building as 64,000 square feet across six stories at Tradewinds Avenue and Mackey Lane. It states that 172 existing Treasure Island beds relocate there from former U.S. Navy housing that is slated for redevelopment.
Who the building employs and how they get there
The facility staffs around the clock. The island's transit timetable is fixed. The ferry runs from the Ferry Building's Gate B at $5 a ride, with weekday departures from the island between 7:30 a.m. and 8:00 p.m. and a last sailing from Gate B at 8:20 p.m.
Muni route 25 runs to the Salesforce Transit Center and along the Embarcadero every 20 minutes, every day. The island's getting-here page publishes no island shuttle.
A shift that ends after the last sailing has no published island service behind it. The island's two newest apartment buildings, Isle House and Hawkins, both stand above 90 percent leased, per the San Francisco Chronicle on 8 July 2026.
Lodging operators competing for service and support staff in San Francisco read this building as a new employer on an island with a fixed transit timetable. Its staffing plan has to solve an evening gap that the published island service does not cover.
Where the building sits in the sequence
The authority's table puts the care building ahead of every residential phase it lists. The 100 senior units at E1.2 follow in February 2027, the 150 units at IC4.3 in June 2027 and the 117 units at B1-B2 in 2027. The condominium parcels C2.1, C2.3 and C3.5 run from 2027 to 2030.
The notice carries no hotel project on Treasure Island or Yerba Buena Island.