A five commissioner public utility district is a district that (1) either:
(a) Has or had a license from the federal power commission to construct a hydroelectric project of an estimated cost of more than two hundred and fifty million dollars, including interest during construction; or (b) has a population of five hundred thousand or more; and (2) voters of the district approved a ballot proposition authorizing the district to become a five commissioner district as provided under RCW 54.40.040. All other public utility districts shall be known as three commissioner districts.1994 c 223 § 57; 1977 ex.s. c 36 § 1; 1959 c 265 § 2.