Faced with economic and environmental uncertainties, the Hampton Roads Sanitation District (HRSD) was challenged to adapt its 249 million gallons per day wastewater-treatment network to address and maintain reliable service to more than 1.7 million residents across southeast Virginia while safeguarding the region’s diminishing water supply and ecologically sensitive Chesapeake Bay.
Designed to substantially reduce combined sewer overflows to the waterways of the nation’s capital, the $240-million, 12,300-ft-long hydraulic tunnel traverses a route that includes varying subsurface conditions, fragile utility networks and above-ground environments ranging from rivers and parks to densely populated urban neighborhoods.
To combat failing prestressed concrete cylinder pipe (PCCP) in its system, the Washington Suburban Sanitary Commission has placed a high priority on replacing sections of existing PCCP with ductile iron or steel pipe.
The new wastewater treatment plant is designed for an average daily flow of 332,000 gallons and provides nutrient removal to meet effluent requirements of 3.0 mg/l total nitrogen and 0.3 mg/l total phosphorus.