California Code, Streets and Highways Code - SHC § 1465

(a) Permittees may excavate openings in county highways to make repairs in cases of emergency requiring immediate action. In such cases the appropriate representative of the road commissioner shall be promptly notified of any such action, and such permittee, at his own expense, shall immediately replace such county highway in as good condition as before such excavation.

(b) A public agency supplying water service to its inhabitants may, within its corporate limits, excavate a county highway without a permit in cases of emergency requiring immediate action; but in such cases the county highway shall, at the expense of the public agency, be replaced in as good condition as before such excavation.