The HAZWOPER regulation can be found within Title 8 of the California Code of Regulations in section 5192 (8 CCR 5192), Subsection (e) details the training requirements for three different "Site Worker" levels, detailed below. The "Sites" we're talking about are Superfund Sites. If you work at a Superfund Site, you'll need one of these levels of training. Although, because these trainings are so comprehensive, many agencies and employers require their employees to obtain and maintain one of these training certifications.
Subsection (q) of the HAZWOPER regulation details the training requirements for the (5) levels of Emergency Response training required when handling releases of hazardous materials. Organizations that incorporate an Emergency Response Team (ERT) will typically use one of these levels as the basis for their teams' training, depending on their anticipated level of involvement.