Wash. Rev. Code § 34.05.365
An agency may incorporate by reference and without publishing the incorporated matter in full, all or any part of a code, standard, rule, or regulation that has been adopted by an agency of the United States, of this state, or of another state, by a political subdivision of this state, or by a generally recognized organization or association if incorporation of the full text in the agency rules would be unduly cumbersome, expensive, or otherwise inexpedient. The reference in agency rules shall fully identify the incorporated matter. An agency may incorporate by reference such matter in its rules only if the agency, organization, or association originally issuing that matter makes copies readily available to the public. The incorporating agency shall have, maintain, and make available for public inspection a copy of the incorporated matter. The rule must state where copies of the incorporated matter are available.
RCW 34.05.365