California Code, Streets and Highways Code - SHC § 27206

If during the month of July next preceding the expiration of the time estimated for the construction of the works it shall appear to the board that the construction of the works may be delayed beyond the time so estimated the board shall estimate the period of such delay and cause a tax to be levied and collected in accordance with the provisions of this chapter which shall be sufficient to produce the amount required to pay one year's interest on the bonds or, if the estimated period of delay will be less than one year, the amount required to pay the interest which will accrue on the bonds during such estimated period of delay.

The amount of any such tax shall be reduced to the extent that the district has funds on hand and available for the purpose of paying such interest.