California Code, Streets and Highways Code - SHC § 728

Any person proposing or desiring to excavate or construct ditches in, under or over any State highway, to carry water for any purpose, shall construct, without expense to the State, such bridges, culverts, pipes, siphons or crossings as are necessary adequately and properly to carry such water in, under or over such State highway.

Any such construction shall be done in accordance with the permit and pursuant to section 671, and shall be subject to the approval of the department.  The issuance of any such permit may be withheld until the department finds that proper and adequate provision is made for the protection of such State highway and for the safety of travel thereon.