Cal. Health & Saf. Code § 25209.5
The liner, leachate collection and removal, groundwater monitoring, and vadose zone monitoring systems required by Sections 25209.2, 25209.3, and 25209.4 shall be designed, constructed, and operated according to regulations adopted by the department and State Water Resources Control Board regulations and standards for liner, leachate collection and removal, groundwater monitoring, and vadose zone monitoring systems for class I hazardous waste landfills, to the extent those regulations and standards are not less stringent than the regulations and standards of the department. Owners or operators of land treatment units which have treated and will treat solely non-RCRA hazardous waste and which are equipped with liners, leachate collection and removal systems, and a groundwater monitoring system that satisfy the requirements of this section shall not be required to perform vadose zone monitoring.
Ca. Health and Saf. Code § 25209.5