In this section, “public agency” means: Any State, county, or municipal authority; Any public drainage commission; Any public sewerage commission; Any public water commission; or Any sanitary district created under Subtitle 6 of this title. A public agency may make a contract or an agreement with the Washington Suburban Sanitary Commission: To connect any drainage, sewerage, or water system of that public agency with facilities of the Washington Suburban Sanitary Commission; To buy water from or sell water to the Washington Suburban Sanitary Commission; To accept drainage or sewage from the Washington Suburban Sanitary Commission; and To send drainage or sewage to the Washington Suburban Sanitary Commission. A public agency may make any other agreement with the Washington Suburban Sanitary Commission to aid in the building or operation of any drainage system, sewerage system, or water system built or operated by the public agency or the Washington Suburban Sanitary Commission. The powers granted in this section are in addition to and not limited by any other powers granted to a public agency.