Unless the county councils of Montgomery County and Prince George’s County have approved the extension, the Commission: may not extend or approve construction of a sewer of any size or capacity to serve property in either county beyond the area that has been approved for service in a Program and the 10–year water and sewer plan required under § 9–503 of the Environment Article; or subject to subsection (b) of this section, may not extend a water line of any size or capacity beyond the approved terminal point of a major project. If the county councils of Montgomery County and Prince George’s County have approved the extension, the Commission may extend a water line beyond the terminal point if: the extension of the water line would provide water service to a development that is within an approved sewer project area; or the affected county, through an appropriate county unit, has approved the installation of individual sewage disposal facilities. The Commission may construct an extension that requires approval under this section if: the proposed extension has been submitted for approval; and within 30 days after receipt of the proposed extension, the affected county has not notified the Commission that the extension should not be made.