The California Division of Occupational Safety and Health fined three contractors $147,315 for safety violations following the collapse of a temporary mold and vertical shoring that sent 13 workers to the hospital.

Workers at an Oakland construction site were pouring concrete into elevated formwork in May when the support system collapsed. They 20 feet into freshly poured concrete, reinforced steel, timber framework, tools and equipment.

The workplace safety agency commonly known as Cal-OSHA said its investigation found the formwork and vertical shoring system were not properly designed, installed or inspected.

Cal-OSHA fined subcontractor Largo Concrete Inc. $73,365 and N.M.N. Construction Inc. $70,320. The agency said the companies failed to ensure the formwork and shoring were designed to safely withstand intended loads, failed to have calculations and drawing approved by an engineer as required, and failed to ensure the shoring supports were built on a level and stable base.

General contractor Johnstone Moyer Inc. was fined $3,630.