Within the debt limit provision of the Constitution of North Dakota, the municipality may pay, at the option of the governing body, any portion of the cost of the improvement by general taxation upon all the taxable property in the municipality. The tax shall be levied at the time of making the improvement and shall be spread over such years and in such amounts as will meet the municipality’s share of the cost represented by the principal of the warrants issued against the fund and the interest thereon. The tax, when collected, shall be paid into the fund of the district and shall be used solely for the payment of the principal and interest of the warrants issued against the district. The ordinance levying the tax shall be irrepealable so long as any warrants are outstanding against the fund.