Territory not originally within a district may be added thereto in the following ways:

Terms Used In Wisconsin Statutes 200.15

   (1)   
      (a)    Except as provided in par. (b), upon receipt by the commission, and the regional planning commission of the region within which the district or the greatest portion of the district is located, of official notice from the city, village, or town sanitary district for any of the following territories:
         1.    Territory that is annexed to a city or village that is located entirely within the original district prior to the annexation.
         2.    Territory that is added to a town sanitary district under s. 60.785 (1) that is located entirely within the original district prior to the addition.
         3.    Territory that is annexed or attached to a city or village or added to a town sanitary district under s. 60.785 (1) if a portion of the city, village, or town sanitary district is located within a district that contains a 2nd class city with a population of 200,000 or more.
      (b)    If, within 30 days after receipt of a notice under par. (a), the regional planning commission files with the commission a written objection to any part of the annexation or addition or the commission issues a written determination disapproving the addition of the territory, the territory proposed to be added or annexed under this subsection may be added or annexed only under sub. (2).
      (c)    Failure of the commission to disapprove the addition of the territory under this subsection is subject to review under ch. 227.
   (2)   Proceedings leading to the addition of other territory to a district may be initiated by petition from a municipal governing body or upon motion of the commission. Upon receipt of the petition or upon adoption of the motion, the commission shall hold a public hearing preceded by a class 2 notice under ch. 985. The commission may approve the annexation upon a determination that the standards of ss. 200.05 (4) (b) and (c) and 200.15 (3) are met. Approval actions by the commission under this section shall be subject to review under ch. 227.
   (3)   Annexations under subs. (1) and (2) may be subject to reasonable requirements as to participation by newly annexed areas toward the cost of existing or proposed district facilities.
   (4)   Section 200.09 (1) does not require the appointment of a commissioner from territory annexed under this section if that territory, on the day before the annexation, has a population of less than 8.5 percent of the total population served by the district.