Get Full Government Meeting Transcripts, Videos, & Alerts Forever!
Get email alerts on the Millennium Tower topic
No spam. Unsubscribe anytime.
Committee presses peer reviewer and DBI on Millennium Tower outriggers and foundation analysis
Summary
The GAO Committee continued its review of Millennium Tower safety. A peer reviewer flagged concerns about outrigger design and recommended nonlinear analysis; DBI consultants have requested additional pile/foundation data and expect further materials in weeks as part of an ongoing technical review.
Supervisor Aaron Peskin reopened the Committee—9s continuing inquiry into tall‑building seismic standards and the Millennium Tower (301 Mission Street). The session included sworn testimony from peer reviewer Hardeep Singh Panu (Middlebrook & Louie) about peer review scope and technical concerns, and Department of Building Inspection staff described ongoing consultant review of superstructure and foundation analyses.
Panu described the peer review role as independent and iterative. He said the building relied on shear walls, moment frames and outriggers that connect those systems, and that the outrigger elements needed clear design treatment to ensure they would be the intended "weak link" (the ductile, controlled damage location) rather than allowing column or other element failure in a seismic event. He recommended nonlinear modeling and careful design of outriggers as deep beams or discontinuous shear walls and flagged the need to understand forces transferred to columns. Panu said those concerns were addressed in comments and that some reconfiguration occurred, but he noted he had not analyzed foundation/pile issues and was not a geotechnical specialist.
DBI staff and the city—9s consultant team said they had reviewed the initial Simpson Gumpertz & Heger (Hamburger) report and requested additional foundation/pile analysis and documentation about driven and socketed piles. DBI reported consultants were reviewing supplemental materials and expected additional detailed pile calculations within weeks. The city also said it had contracted the Applied Technology Council to produce a broader inventory and tall‑building resilience recommendations, a study estimated to take roughly 16 months.
Committee members asked whether planned adjacent projects (the Transbay Terminal/related construction) had been reviewed for interaction effects; peer reviewers said that work was outside the peer review scope unless specifically requested and that no geotechnical cross‑analysis had been provided. DBI said recent on‑site inspections addressed maintenance items and that structural and geotechnical consultants were continuing technical review. No immediate retrofit plan was ordered at the hearing; DBI said remediation options were being discussed between developer, homeowners association, and consultants and that time frames and whether partial occupancy would be affected were not yet public.
