1.    For the purposes of this section, “lateral drain” means a drain constructed after the establishment of an original assessment drain or drainage system and which flows into such original drain or drainage system from outside the limits of the assessed area of the original drain; provided, that a determination by a water resource board as to whether an existing or proposed drain is a lateral or a new drain shall be conclusive when entered upon the records of the board.

2.    All property owners whose property would be affected by a lateral drain may jointly petition the board for the construction of such drain and shall deposit with the board a good and sufficient bond to be approved by the board, conditioned upon the petitioner or petitioners paying all costs of the proposed lateral drain. A petition for a lateral drain shall be sufficient if signed by one or more property owners whose property will be affected by the lateral drain. Whenever improvements of an original drain are made necessary by the construction of a lateral drain, the costs of such improvements to the original drain shall be charged as part of the cost of construction of the lateral drain and assessed against the property benefited thereby and collected as other assessments are collected. In the event the board determines that improvements to the original drain are also beneficial to property served by the original drain, the board may assess that portion of the cost of the improvements it determines appropriate to property benefited by the original drain. Unless the petitioners agree to construct the lateral drain, the board, within ten days, may commence proceedings for the construction of the lateral drain according to the provisions of this chapter. No person shall dig or construct any lateral ditch or drain which will conduct the flow of water from any land or lands into any drain constructed under the provisions of this chapter, except as provided in this section and with approval of the board. In all instances involving the construction of a lateral drain, the board shall estimate and determine the proportionate share of the cost of the main or original drain which should be paid by the petitioners. The petitioners shall pay into the district treasury the amount so determined, and shall then be allowed to connect such lateral ditches or drains with the original drain under the direction and superintendence of the board, but at their own cost and expense. The money paid into the county treasury shall be credited to the drainage fund of the specific drain involved.

    3.    If one or more of the property owners to be benefited by the construction of a lateral drain or ditch petitions the district for the construction of a lateral drain or ditch, the district shall then proceed in the same manner as is used for the establishment of a new drain and thereafter such lateral drain shall constitute a part of the original drain to which it is connected and the affected property shall be a part of such drainage district.