(a) The geographical area embraced within the district may be enlarged to include any additional county, or part thereof, upon such terms and conditions, consistent with the provisions of this chapter, as may be agreed upon by the commission and such additional county and in conformance with the following procedures. The governing body of the county desiring to be included in the district shall adopt an ordinance or resolution, as may be appropriate, specifying the area of the county to be included and a statement that a contract or agreement between the county and the district, specifying the terms and conditions of admittance to the district has been executed. The ordinance or resolution to which shall be attached a certified copy of such contract shall be filed with the commission. Upon such filing, the district shall thereupon be enlarged to embrace the county or the portion thereof specified in the contract.
(b) A county may withdraw from the district by resolution or ordinance, as may be appropriate, adopted by majority vote of the governing body thereof. The withdrawal of any county shall not be effective until the resolution or ordinance of withdrawal is filed with the commission. The withdrawal from the district of any county shall not relieve such county from the obligation of any guarantee made by such county with respect to contracts, agreements, notes, certificate of indebtedness or other obligations of the district nor from the obligation to levy taxes and pay over to the district the proceeds therefrom for the purposes and in the manner set forth in section 87-14. (Mont. Co. Code 1965, § 72-21; 1965, ch. 870, § 1.)