The board of park commissioners of any metropolitan park district which includes a city with a population greater than one hundred thousand may submit to the electorate of the territory sought to be annexed a proposition that all property within the area annexed shall, upon annexation, be assessed and taxed at the same rate and on the same basis as the property of such annexing metropolitan park district to pay for all or any portion of the then outstanding indebtedness of the metropolitan park district.
RCW 35.61.275