California Code, Health and Safety Code - HSC § 25296.30

(a) The board, in consultation with the State Department of Health Services, shall develop guidelines for the investigation and cleanup of methyl tertiary-butyl ether (MTBE) and other ether-based oxygenates in groundwater. The guidelines shall include procedures for determining, to the extent practicable, whether the contamination associated with an unauthorized release of MTBE is from the tank system prior to the system's most recent upgrade or replacement or if the contamination is from an unauthorized release from the current tank system.

(b) The board, in consultation with the State Department of Health Services, shall develop appropriate cleanup standards for contamination associated with a release of methyl tertiary-butyl ether.