As an alternative to other methods of ascertaining assessments for local improvements, in a local improvement district established for safeguarding open canals or ditches, the district may be sectioned into subdivisions or zones paralleling the canal or ditch, numbered respectively, first, second, third and fourth. Each subdivision shall be equal to one-quarter of the width of the district as measured back from the margin of the canal right-of-way. The rate of assessment per square foot in each subdivision so formed shall be fixed on the basis that the special benefits conferred on a square foot of land in subdivisions first, second, third, and fourth, respectively, are related to each other as are the numbers, forty, thirty, twenty, and ten, respectively, and shall be ascertained in the following manner:

(1) The products of the number of square feet in subdivisions first, second, third, and fourth, respectively, and the numbers forty, thirty, twenty, and ten, respectively, shall be ascertained;

(2) The aggregate sum thereof shall be divided into the total cost and expense of the local improvement;

(3) The resultant quotient multiplied by forty, thirty, twenty, and ten, respectively, shall be the respective rate of assessment per square foot for each subdivision.

Safeguarding open canals or ditches, assessments: RCW 35.43.040, 35.43.045, 36.88.015, 36.88.350, 36.88.380 through 36.88.400, 87.03.480, 87.03.526.