California Code, Streets and Highways Code - SHC § 9546

The legislative body of any city which has issued bonds which are outstanding under this division, the original authorized aggregate principal amount of which was less than the aggregate principal amount of the original assessment which was levied as security therefor, and which intends to issue additional bonds to be secured by that original assessment to provide for and finance the construction and installation of further improvements, may, at any time, determine by resolution that the public interest or necessity requires the refunding of the bonds which are outstanding, the levy of a reassessment as security for the refunding bonds, and the continuation of the original assessment as to the unpaid principal amount thereof which shall be security for the additional bonds to be issued, and may declare its intention to so proceed by a resolution adopted pursuant to Section 9520.

The resolution shall, in addition to declaring the intention of the legislative body to refund the bonds which are outstanding and to levy reassessments as security for the refunding bonds, also declare the intention of the legislative body to issue additional bonds on the basis of the original assessment and to continue the original assessment in an amount sufficient to provide security for the additional bonds to be issued.  The resolution shall require that the report prepared pursuant to Section 9523 contain the unpaid principal amount of each original assessment in excess of the amount thereof which will be superseded and supplanted by the principal amount of the corresponding reassessment, which shall be security for the additional bonds to be issued.