Pen. Code, § 4058

The Secretary of State shall furnish and transmit to the clerk of the board of supervisors of the county adopting the initial resolution for the organization of any district under this chapter a certificate of the organization of the same. Upon receipt of the certificate the clerk shall within 10 days send a certified copy of the certificate to each of the clerks of the several boards of supervisors of the counties constituting the district, and shall also within the time specified in this section notify each supervisor appointed as a member of the board of directors of the district of such fact and of the time and place of the first meeting of the board of directors of the district. The time and place of the meeting shall be fixed and determined by the clerk of the board adopting the initial resolution, but said time of meeting shall be within 30 days after the date of mailing notices thereof. The necessary expense incurred by supervisors in attending and in going to and coming from any meeting of the board of directors of the district shall constitute a county charge of their respective counties.