GOV §31770.3: (a) This article, or selected provisions of this article, shall become effective in any county or district only when the county board of supervisors or governing board of the district adopts an ordina

(a) This article, or selected provisions of this article, shall become effective in any county or district only when the county board of supervisors or governing board of the district adopts an ordinance or resolution providing for that implementation. The board of supervisors or governing board may not adopt that ordinance or resolution, and this article, or selected portions of this article, may not become effective in the county or district unless and until the actuarial analysis described in Section 31770.4 has been completed and has determined that the program, as proposed to be adopted by the county or district, will be cost neutral and agreed to in a collective bargaining agreement. (b) Based on the actuarial analysis, the requirement of cost neutrality, and the collective bargaining agreement, the county or district shall, in the implementing ordinance, elect one of the following for each bargaining unit other than a bargaining unit whose members are described in Section 31470.4: (1) To be subject to the provisions of this article, including the forward DROP provisions contained in Sections 31771 to 31776.5, inclusive, but excluding the actuarial equivalent DROP provisions contained in Section 31777 and excluding the backward DROP provisions contained in Sections 31778 to 31778.2, inclusive. (2) To be subject to the provisions of this article, including the actuarial equivalent DROP provisions contained in Section 31777, but excluding the forward DROP provisions contained in Sections 31771 to 31776.5, inclusive, and excluding the backward DROP provisions contained in Sections 31778 to 31778.2, inclusive. (3) To be subject to the provisions of this article, including the backward DROP options contained in Sections 31778 to 31778.2, inclusive, but excluding the forward DROP provisions contained in Sections 31771 to 31776.5, inclusive, and excluding the actuarial equivalent DROP provisions contained in Section 31777. (c) With respect to a bargaining unit whose members are described in Section 31470.4, the county or district may, in the implementing ordinance, be subject only to the provisions of this article as provided in paragraph (3) of subdivision (b). (d) The program shall become operative with respect to all safety members of the system on the date specified in the implementing ordinance. (e) The implementing ordinance shall specify a period of time, which shall be at least four years and not more than 10 years from the date of implementation, after which an initial review of the program shall be conducted pursuant to Section 31779.