Cal. Pub. Resources Code § 8812
Prior to January 1, 2000, state plane coordinates shall be based on, or derived from, the plane coordinates of monumented second order or better horizontal control stations that have been published by the USC&GS or NGS. Any survey or map that uses those coordinates shall be based on, and show, established field-observed direct connections to at least two stations of corresponding or better accuracy whose credentials are based upon published stations of the USC&GS or NGS. The geodetic positions of CCS27 and CCS83 stations that are used to increase the density of control and that purport to be of second order or better accuracy shall have been surveyed in conformity with the applicable survey standards and specifications in effect at the time of the survey as defined by the FGCS.
Ca. Pub. Res. Code § 8812