Washington Revised Code Title 58. Boundaries and Plats § 58.04.020. Suit to establish lost or uncertain boundaries--Mediation may be required

(1) Whenever the boundaries of lands between two or more adjoining proprietors have been lost, or by time, accident or any other cause, have become obscure, or uncertain, and the adjoining proprietors cannot agree to establish the same, one or more of the adjoining proprietors may bring a civil action in equity, in the superior court, for the county in which such lands, or part of them are situated, and that superior court, as a court of equity, may upon the complaint, order such lost or uncertain boundaries to be erected and established and properly marked.

(2) The superior court may order the parties to utilize mediation before the civil action is allowed to proceed.