California refinery operators are grappling with how to involve workers in drafting safety plans, a new consultation requirement they say is ambiguous and challenging.

Unions and companies are interpreting “consultation” differently under the state’s new refinery regulations—known as the process safety management rule or PSM. The safety rules haven’t been fully implemented 10 months after they took effect and have prompted enforcement actions.

Some facilities’ planning documents are caught up in disputes over who can be involved. And it is...