RCW 27.12.070 Rural county library districts or rural partial-county library districts — Disbursement of revenues and collection of taxes.The county treasurer of the county in which any rural county library district or rural partial-county library district is created shall receive and disburse all district revenues and collect all taxes levied under this chapter.
http://apps.leg.wa.gov/rcw/default.aspx?cite=27.12.070