When there is unincorporated territory containing less than one hundred acres and having at least eighty percent of the boundaries of such area contiguous to two municipal corporations providing either water or sewer service, one of which is a water-sewer district, the legislative authority of either of the contiguous municipal corporations may resolve to annex such territory to that municipal corporation, provided a majority of the legislative authority of the other contiguous municipal corporation concurs. In such event, the municipal corporation resolving to annex such territory may proceed to effect the annexation by complying with RCW
57.24.170 through
57.24.190. For purposes of this section, "municipal corporation" means a water-sewer district, city, or town.