Md. Code, Pub. Util. § 23-314

(a) Unless the county councils of Montgomery County and Prince George’s County have approved the extension, the Commission: (1) 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 (2) 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. (b) 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: (1) the extension of the water line would provide water service to a development that is within an approved sewer project area; or (2) the affected county, through an appropriate county unit, has approved the installation of individual sewage disposal facilities. (c) The Commission may construct an extension that requires approval under this section if: (1) the proposed extension has been submitted for approval; and (2) within 30 days after receipt of the proposed extension, the affected county has not notified the Commission that the extension should not be made.