Partnering to Protect Clean Water

• Serving a 1,000-square-mile area in Montgomery and Prince George's Counties, WSSC maintains approximately 5,200 miles of sewer mains.
• WSSC's sewer system is a modern sanitary, or separate, system - meaning the pipes that carry wastewater from homes and businesses to wastewater treatment plants are separate from the storm water drainage system.
• Combined sewer systems (found in portions of Washington, D.C., Baltimore, New York, Philadelphia and elsewhere) convey both wastewater and storm water in one piping system. During periods of rainfall or snowmelt, the wastewater volume in a combined sewer system can exceed the capacity of the sewer system, pumping station or treatment plant. In these instances, combined systems are designed to overflow occasionally and discharge excess wastewater directly to nearby streams, rivers, lakes and estuaries.
• WSSC's sewer system is primarily a gravity system - hence the fact that a majority of the pipes follow streambeds at the lowest elevation in the basin. There are 24 major basins within our service area.
• Blockages (grease, roots, debris) in sewer pipes are major factors in more than 70 percent of sewer overflows.
• In 1994, WSSC established the Fats, Oils and Grease (FOG) program to address grease discharged illegally or through improperly maintained grease abatement systems in restaurants and fast food establishments.
• The Sewer Reconstruction Program is among WSSC's proactive initiatives aimed at effectively operating and maintaining our wastewater collection system. The program encompasses comprehensive sewer basin studies and sewer main, manhole and house connection reconstruction and replacement. Funding for the Sewer Reconstruction Program has increased substantially since its inception in 1979.
• WSSC operates six Wastewater Treatment Plants (WWTP) and cleans more than 180 million gallons of wastewater each day. Last year, WSSC cleaned approximately 63 billion gallons of wastewater and removed 20 million pounds of nitrogen and phosphorus. Over the past 15 years, WSSC has reduced nitrogen discharges by 51 percent while wastewater flows have increased 22 percent.
• In 2004, the Chesapeake Bay Foundation (CBF) recognized WSSC for significantly reducing nitrogen levels entering the Bay through the use of an innovative process at its Piscataway facility in southern Prince George's County.
• WSSC recently completed a $70 million expansion of the Seneca WWTP that includes a new 20 million gallons-per-day (mgd) facility that replaces the existing 5 mgd plant. The new Seneca plant uses state-of-the-art biological and chemical processes that remove 64 percent more nitrogen and 77 percent more phosphorous than the original plant.
• All major WSSC WWTP use advanced biological nutrient removal technology.
• WSSC operates 47 wastewater pumping stations.