The county auditor of each county in which any rural fire protection district or districts have been organized under the provisions of this chapter, prior to the effective date of this chapter, shall forthwith designate a time and place for a hearing before the county board of such county and shall give due notice thereof in the manner prescribed by section 18-10-03. At the time and place so fixed the board of county commissioners shall meet and all persons interested shall have opportunity to be heard. Thereupon, the board of county commissioners shall consider the general rural fire protection policy for the county as a whole and shall determine the boundaries of said district or districts, whether as existing prior to such determination or otherwise, and shall make a written order of such determination which shall be filed in the office of the county auditor. Thereafter, such district or districts must be deemed to be organized and operating    under the provisions of this chapter. Nothing herein contained may impair, affect, or discharge any previously existing contract, obligation, lien, or change of said district or districts.