California Code, Health and Safety Code - HSC § 9027

(a) A local agency formation commission, in approving either a consolidation of districts or the reorganization of two or more districts into a single district, may, pursuant to subdivisions (k) and (n) of Section 56886 of the Government Code, change the number of members on the board of trustees of the consolidated or reorganized district, provided that the resulting number of trustees shall be an odd number but not less than five.

(b) Upon the expiration of the terms of the members of the board of trustees of the consolidated or reorganized district whose terms first expire following the effective date of the consolidation or reorganization, the total number of members on the board of trustees shall be reduced until the number equals the number of members determined by the local agency formation commission.

(c) Notwithstanding subdivision (c) of Section 9024, in the event of a vacancy on the board of trustees of the consolidated or reorganized district at a time when the number of members of the board of trustees is greater than the number determined by the local agency formation commission, the vacancy shall not be filled and the membership of the board of trustees shall be reduced by one member.