Water Treatment Plant Havre de GraceDepartmentsDepartment of Public WorksWater Treatment Plant Water Plant: 415 St. John Street, Havre de Grace, MD 21078 Ph. 410-939-1070 for any drinking water emergencies weekdays after 5 pm and weekends. Mission: The Public Works Division of the Water Treatment Plant is responsible for the operation and maintenance of the City water plant. Our goal is to provide our customers with safe, reliable water in a responsive and cost effective manner. The Safe Drinking Water Act (SDWA) is the main federal law that ensures the quality of drinking water. Under SDWA, U.S. Environmental Protection Agency (U.S. EPA) sets standards for drinking water quality and oversees the states, localities, and water suppliers who implement those standards.