Pacific Structures, a San Francisco-based company that's now under investigation by state workplace safety regulators in connection with a high-rise accident in the South of Market area on Wednesday, was one of the firms linked to a major construction fire in the city over two years ago.
On Thursday, city building inspectors barred construction work at the Tehama Street skyscraper site for 48 hours and California's Division of Occupational Safety and Health (Cal/OSHA) began its probe of the incident.
Cal/OSHA inspectors gained access to the building hours after crews were able to stabilize a platform on the 35th floor that began to tip the day before, a scare that led to the evacuation of more than a dozen nearby buildings.
A hydraulic jack, part of a device described by building inspectors as a climbing-form machine, was supporting the platform but failed, leading to concerns that a concrete slab it was holding up would fall to the street.
"The platform tilted when the hydraulic jack failed," said Cal/OSHA spokeswoman Erika Monterroza.
"It tipped over, the machine then ran into the wall and caused this concrete form to angle out," said Bill Strawn, a spokesman for the Department of Building Inspection, in an interview.
The climbing-form machine acts like a massive elevator, allowing crews to lay out concrete floor by floor. The large device was being dismantled Thursday, Strawn said.
Building inspectors have issued a notice of violation on the worksite, requiring that crews make the area safe and that a licensed engineer issue reports to the city on the cause of the failure and attesting to a new setup's structural integrity, he said.
The main contractor for the project is Lendlease, an international construction firm based in Sydney, Australia.
Pacific Structures, a subsidiary of the firm Build Group, is a subcontractor on the project dealing in concrete.
Pacific Structures and Build Group were involved in the renovation of the former Renoir Hotel at 45 McAllister St. when it was badly damaged in a three-alarm fire on Aug. 4, 2014.
The fire injured eight workers, led to an investigation by Cal/OSHA and eventually prompted the San Francisco Fire Department to issue two safety citations against Build Group.
Fire officials said at the time that the company removed sprinkler systems at the McAllister Street site and another one on Buchanan Street.
Build Group initially appealed the two $1,000 penalties, but in May 2015 it quietly withdrew its objection.
The Renoir Hotel blaze came in the middle of the city's building boom and months after a much larger construction site fire in the Mission Bay neighborhood that also led to citations against a subcontractor.
A spokeswoman for Build Group and Pacific Structures has yet to comment on Thursday's incident.
