(1) A preliminary assessment, which shall be levied for the purpose of defraying the expenses incurred by the district for organization of the district, for organization of subdistricts, and for defraying overhead costs and other expenses including purchases of rights of way, acquisition of land and payment of fees and services as may be incurred by the district prior to the time that construction assessments are levied or a tax is levied. A preliminary assessment shall be apportioned on the basis of the assessed valuation of property in the district. A preliminary assessment shall be not more than five-hundredths of one percent (0.0005) of the real market value of all taxable property within the district computed in accordance with ORS 308.207. No district shall levy a preliminary assessment for more than three years.

(2) A construction assessment, which shall be levied for the purpose of defraying the cost of constructing or purchasing the works in each subdistrict. The construction assessment shall be levied as soon as the board is able to determine the probable cost of constructing or purchasing the works described in the engineering plan for a subdistrict or a construction assessment may be levied for the construction or purchase of works in accordance with any loan agreement with the government of the United States or the State of Oregon for money to be used in the construction or purchase of such works or in accordance with a purchase agreement entered into with the seller of such works. All construction assessments shall be paid in 10 equal annual installments and shall bear interest at a rate not to exceed six percent per annum until paid from the date the first installment of the assessment is due. Any landowner may make advance payments on the construction assessment levied against the lands of the landowner. The board may, in its discretion, decrease the amount of any annual installment and spread the payment of the construction assessment over a period longer than 10 years. Such decrease shall apply uniformly to all lands within the subdistrict. Whenever the board determines that the original construction assessment is not in an amount sufficient to pay the cost of constructing or purchasing the works described in the engineering plan for the subdistrict, the board shall assess a second construction assessment.

(3) A maintenance and operation assessment, which shall be levied for the purpose of defraying the cost of maintaining and operating the works constructed within any subdistrict. On or before November 1 of each year the board shall determine the probable cost of maintaining and operating the works within each subdistrict during the ensuing calendar year.

(4) An improvement assessment, which shall be levied for the purpose of defraying the cost of making improvements within a subdistrict. On or before November 1 of each year the board shall determine the probable cost of making any necessary improvements to any completed works within each subdistrict. No improvement assessment levied in any one year shall be greater in amount than one percent of all construction assessments levied against the same tract of land. In case of an emergency the board may, upon the approval of the owners of over half of the lands affected, levy, assess and collect a special improvement assessment. The board may, in its discretion, levy an improvement assessment within the limitations above provided in order to accumulate a fund to make improvements in future years. [Amended by 1959 c.605 §1; 1961 c.186 §8; 1965 c.623 §13; 1969 c.691 §8; 1991 c.459 §431]