In the plans for and in the construction of a drainage system in an irrigated region, under the provisions of this chapter, provision may be made for the prevention of, or affording an outlet for drains to prevent, injury to land from seepage of or saturation by irrigation water, and for the carrying off of necessary wastewater from irrigation, and benefits resulting from such provision shall be considered in making the apportionment of the cost of such system.
RCW 85.08.380