Idaho Code § 42-2962
The commissioners may also levy assessments for any expense necessarily incurred by them for construction, maintenance, repair, or any extraordinary reasons, and also may add to said assessment sufficient to pay any deficiency occurring the preceding year or any other unpaid warrant indebtedness, if any, or to pay any outstanding warrants: provided, that any assessments to be hereafter made by any drainage commissioners to pay for the payment or retirement of any bonds or warrants shall not exceed twenty percent (20%) of the original cost of organization and construction, and said assessment for the payment or retirement of any bonds or warrants shall be in addition to the assessments which may be levied under this section or section 42-2936, Idaho Code, and such assessments, when made, shall be apportioned under section 42-2961, Idaho Code, and collected as hereinbefore provided for.
Idaho Code § 42-2962