In Montgomery County or Prince George’s County, the comprehensive plan for water supply systems and sewerage systems may allow the installation and use of an individual sewerage system for an interim period until the necessary sewerage transmission and treatment capacity in the area is available to provide adequate community sewerage service if: A community sewerage system otherwise is required in the area; but Access to a community sewerage system is prohibited by an order of: The Department; Montgomery County; Prince George’s County; or The Washington Suburban Sanitary Commission.