(1) The governing body may by resolution make changes in the boundaries of a district as they consider reasonable and proper but may not delete any portion of the proposed area if the deletion will create an island of included or excluded lands.
(2) The governing body may not delete any portion of the proposed area that is contributing or may reasonably be expected to contribute to the pollution of any watercourse or body of water in the proposed area.
(3) For the purpose of subsection (2), it is conclusively presumed that an area that is within 1,500 feet of a proposed or existing sanitary sewer is contributing to the pollution of a watercourse in the proposed area.