RCW 36.70.690: County improvements.

No county shall improve any street or lay or authorize the laying of sewers or connections or other improvements to be laid in any street within any territory for which the board has adopted an official control in the form of precise street map or maps, until the matter has been referred to the planning agency by the department or official having jurisdiction for a report thereon and a copy of the report has been filed with the department or official making the reference unless one of the following conditions apply:

(1) The street has been accepted, opened, or has otherwise received legal status of a public street;

(2) It corresponds with and conforms to streets shown on the official controls applicable to the subject;

(3) It corresponds with and conforms to streets shown on a subdivision (land plat) approved by the board.