Assessment districts are formed to provide a specific service or benefit to lands contained within its boundaries. They are empowered to levy an assessment to fund district operations or to fund specific projects that fulfill the specific purpose for which the district was formed. These assessments are billed, collected and processed by the county treasurer in a manner similar to property taxes.

The assessment districts in Grays Harbor County that are actively levying an annual assessment are:

Grays Harbor Drainage District # 1
Located in Grayland to provide maintenance of the drainage system for local properties. The annual assessments are billed along with the first half property tax statements in February with a due date of April 30.

Grays Harbor Drainage District #2
Located along the Old Brady Highway east of Montesano to provide maintenance of the drainage system for local properties. The annual assessments are billed along with the first half property tax statements in February with a due date of April 30.