A district may apply to the United States for permission to establish, operate, and maintain foreign trade zones: (1) Within the district; and (2) on property adjacent to but outside the district if the property is beyond the boundaries of any existing foreign trade zone grantee and is not currently designated as a foreign trade zone: PROVIDED, That nothing herein shall be construed to prevent such zones from being operated and financed by a private corporation(s) on behalf of such district acting as zone sponsor: PROVIDED FURTHER, That when the money so raised is to be used exclusively for the purpose of acquiring land for sites and constructing warehouses, storage plants, and other facilities to be constructed within the zone for use in the operation and maintenance of the zones, the district may contract indebtedness and issue general bonds therefor in an amount, in addition to the three-fourths of one percent hereinafter fixed, of one percent of the value of the taxable property in the district, as the term "value of the taxable property" is defined in RCW
39.36.015, such additional indebtedness only to be incurred with the assent of three-fifths of the voters of the district voting thereon.