California Code, Government Code - GOV § 26323

An indenture may include a clause relating to the bonds issued thereunder requiring the board to pay and discharge or cause to be paid and discharged from the funds available for that purpose all lawful claims for labor, materials and supplies or other charges which, if unpaid, might become a lien or charge upon the revenues, or any part thereof, of any improvements acquired, constructed or completed from the proceeds of the sale of the bonds, or upon any of the physical properties thereof which might impair the security of the bonds.