A collapse in a major sanitary sewer line operated by the District of Columbia Water and Sewer Authority (DC Water) sent an estimated 243 million gallons of untreated wastewater into the Potomac River, prompting emergency repairs and the installation of a temporary bypass system to contain the overflow and restore normal operations.
The collapse of the Potomac Interceptor — a 54-mile sewer line that carries wastewater from parts of Virginia and Maryland to the Blue Plains Advanced Wastewater Treatment Plant — was discovered on January 19 through security camera footage at an odour control facility. The failure occurred along Clara Barton Parkway in Montgomery County, Maryland, and caused wastewater to overflow into the Chesapeake and Ohio Canal (C&O) National Historical Park and ultimately reach the Potomac River.
“The Potomac Interceptor collapse and overflow is a sewage crisis of historic proportions. Never should any American family, community, or waterway have to experience this level of sewage overflow,” said Environmental Protection Agency (EPA) Administrator Lee Zeldin in a statement on February 20.
DC Water is now performing daily water quality sampling in the river, where E. coli levels fluctuate widely due to weather, utility officials stated.
Subscribe to our Newsletter!
The latest environmental engineering news direct to your inbox. You can unsubscribe at any time.
DC Water crews and contractors have since installed six high-powered pumps upstream of the collapse to divert wastewater around the damaged section. Each pump is capable of moving up to seven million gallons per day, rerouting flows through an isolated portion of the C&O Canal and back into the sewer downstream of the break.
Engineers monitoring the system confirmed the pumps are capturing most of the wastewater, helping reduce pressure in the damaged interceptor and prevent additional dry-weather overflows into the canal and river.
“The bypass allows for excavation and repairs to begin at the site of the collapse,” DC Water said in a statement.
The temporary diversion system is considered critical to containing the spill and enabling crews to examine the damaged 72-inch-diameter pipe, which lies approximately 16 feet underground. Industrial vacuums were scheduled to begin clearing debris from the collapse site January 30, allowing wastewater levels to drop so engineers can assess structural damage and plan repairs.
Emergency repairs are expected to take four to six weeks, followed by longer-term rehabilitation work.
Once the collapse site is cleared, work will begin to remove a 30-foot rock dam blocking the pipe. Crews will need to “proceed carefully not to trigger another collapse, due to the uncertain integrity of the remaining pipe,” DC Water officials stated.
The Potomac Interceptor carries roughly 60 million gallons of wastewater daily from areas near Dulles International Airport to the Potomac Pumping Station in Washington, D.C., where flows are sent to the Blue Plains Advanced Wastewater Treatment Plant for treatment.
DC Water emphasized that its drinking water system remains unaffected by the incident, as it is separate from the wastewater system, but has told area residents to avoid contact with the untreated sewage. The overflow occurred downstream of the Washington Aqueduct’s drinking water intakes at Great Falls.
The interceptor is currently undergoing rehabilitation as part of a 10-year, $625-million capital improvement project aimed at strengthening vulnerable sections of the more than 60-year-old sewer line.
In a social media post, President Donald Trump criticized local and state authorities, calling for federal intervention to coordinate the response and address the infrastructure failure. Washington, D.C. Mayor Muriel Bowser announced in a statement that her district is seeking full federal reimbursement of costs incurred by DC Water.
With the collapse site now secured and wastewater flows partially restored through the bypass, crews are preparing to begin structural repairs while continuing efforts to minimize environmental impacts and restore full service.
