Wash. Rev. Code § 86.15.165
The supervisors may provide by resolution for levying voluntary assessments, under a mode of annual installments extending over a period not exceeding fifteen years, on property benefited from a flood control improvement or stormwater control improvement. The voluntary assessment shall be imposed only after each owner of property benefited by the flood control improvement has agreed to the assessment by written agreement with the supervisors. The agreement shall be recorded with the county auditor and the obligations under the agreement shall be binding upon all heirs and all successors in interest of the property.
The voluntary assessments need not be uniform or directly related to benefits to the property from the flood control improvement or stormwater control improvement.
The levying, collection, and enforcement authorized in this section shall be in the manner now and hereafter provided by law for the levying, collection, and enforcement of local improvement assessments by cities and towns, insofar as those provisions are not inconsistent with the provisions of this chapter.
The disposition of all proceeds from voluntary assessments shall be in accordance with RCW 86.15.130.
The proceeds from voluntary assessments may be used for any flood control improvement or stormwater control improvement not inconsistent with the provisions of this chapter, and in addition the proceeds may be used for operation and maintenance of flood control improvements or stormwater control improvements constructed under the authority of this chapter.
RCW 86.15.165
Severability-1983 c 315: See note following RCW 90.03.500.