There is a fairly comprehensive description of an “essential public facility” in RCW 36.70A.200(1) (emphasis added):
(d) The following facilities and types of facilities are identified in RCW 36.70A.200 as essential public facilities:
(ii) State education facilities;
(iii) State or regional transportation facilities;
(iv) Transportation facilities of statewide significance as defined in RCW 47.06.140. These include:
(A) The interstate highway system;
(B) Interregional state principal arterials including ferry connections that serve statewide travel;
(C) Intercity passenger rail services;
(D) Intercity high-speed ground transportation;
(E) Major passenger intermodal terminals excluding all airport facilities and services;
(F) The freight railroad system;
(G) The Columbia/Snake navigable river system;
(H) Marine port facilities and services that are related solely to marine activities affecting international and interstate trade;
(I) High capacity transportation systems.
(v) Regional transit authority facilities as defined under RCW 81.112.020;
(vi) State and local correctional facilities;
(vii) Solid waste handling facilities;
(viii) In-patient facilities, including substance abuse facilities;
(ix) Mental health facilities;
(x) Group homes;
(xi) Secure community transition facilities;
(xii) Any facility on the state ten-year capital plan maintained by the office of financial management.
This seems to be a fairly comprehensive list, but this regulation makes clear that the primary components of the definition of an essential public facility is that it (1) provides a public service; and (2) is difficult to site. See WAC 365-196-550(1)(f). Thus, there may be other uses that fall within the definition, even if they do not appear on this list.