California Code, Health and Safety Code - HSC § 8136

Any city, including a chartered city, that owns and operates a cemetery may maintain a proceeding in the superior court of the county in which the cemetery is located to have any plot in the cemetery declared abandoned if the present owner of the plot is unknown to the city and a period of at least 50 years has passed since any portion of the plot has been used for interment purposes.The proceeding shall be initiated and conducted in the same manner as prescribed by Section 9069, except that any reference in that section to a public cemetery district shall be deemed to be a reference to the city for purposes of this section.