Cal. WAT § 2101

(a) Before filing or intervening in any such action the board shall hold a public hearing on the necessity for restricting ground water pumping or for a physical solution in order to protect the quality of water from destruction or irreparable injury. The board shall serve notice of such hearing as provided in Section 6066 of the Government Code and shall mail a copy of such notice to each producer of ground water within the area proposed for investigation, to the extent that such producers of ground water are known to the board, at least 15 days prior to the date of such hearing, except that notice need not be mailed to producers of minor quantities of water as defined in Section 2102.

(b) In the event the board decides that the rights to the use of the ground water must be adjudicated in order to require the restriction of pumping or physical solution necessary to preserve it from destruction or irreparable injury to quality, the board shall first determine whether any local public agency overlying all or a part of the ground water basin will undertake such adjudication of water rights. If such local agency commences an adjudication, the board shall take no further action, except that the board may, through the Attorney General, become a party to such action.

(c) In the event no local agency commences such action within 90 days after notice of the decision of the board, the board shall file such action.