Following the August 2012 fire and chemical release at a San Fransico Bay Area refinery, the Governor of CA formed the Interagency Working Group on Refinery Safety to examine ways to improve public and worker safety through enhanced oversight of refineries, and to strengthen emergency preparedness in anticipation of any future incident. The Interagency Working Group found gaps in the regulatory schemes, noting that the regulations did not cover all aspects of process safety. The report recommended that existing CalARP regulations be strengthened to ensure that more data and information are provided to agencies, workers, and the public. The final CalARP Program 4 regulations were adopted and became effective on October 1, 2017. In addition to the expanded prevention program requirements, the refineries are required to perform a Hierarchy of Hazard Control Analysis (HCA) of a process or of recommendations from a PHA, in which the team applies INHERENT SAFETY MEASURES AND SAFEGUARDS in a structured sequence and priority order in order to identify the safest feasible alternative for a specific purpose. This is a nice explanation of what is necessary to perform a Hierarchy of Hazard Control Analysis (HCA).