DC Water did not respond to ENR’s requests for information about the scope, timing or cost of the cleanup and repairs, or the contractors involved in the containment effort—but reports say the effort could cost up to $10 million.

Constructed in the 1960s, the 54-mile Potomac Interceptor carries up to 60 million gallons of wastewater daily from Washington, D.C.’s Maryland and Virginia suburbs to the Blue Plains wastewater plant in the city, for treatment (see map below). 

DC Water says the break occurred about one-quarter-mile from where DC-based Fort Meyer Construction Corp. has been at work since last fall on an eight-month, $9.6-million project to rehabilitate an 800-ft segment of the 16-ft-deep interceptor using sliplining methods. That project is part of DC Water’s decade-long rehabilitation program, estimated to cost $625 million.

Rupture of 72-in. sewer pipe along the Potomac River north of Washington, D.C. on Jan. 19 caused massive wastewater spill that has bben contained, but cleanup and pipe repair could be $10-million effort.
Map: DC Water

With the collapse sending an estimated 40 million gallons of sewage per day gushing into the river, DC Water says on its website that its contractors worked with the National Park Service to reroute the bulk of the Potomac Interceptor flow around the leak through a dry, isolated section of the historic Chesapeake & Ohio Canal, located 125 ft away. As many as eight large pumps are being used to channel the sewage about 2,700 ft downstream, where it is then directed back into the interceptor, the agency says. Some existing flow is safely moving through the collapse site within the sewer line, according to DC Water.

The U.S. Corps of Engineers-operated Washington Aqueduct, which supplies drinking water to the city and parts of Northern Virginia, is unaffected by the incident, since the primary Potomac River intake point for that system is located upstream from the rupture site. But the Corps closed a downstream intake facility as a precaution.

Ten days following initial discovery of the sewage leak, DC Water reported that overflows from the breach appear to have ended, although maintaining 24/7 operation of the pumps has been complicated by the area’s protracted stretch of sub-freezing weather.

The agency’s focus now is on stabilizing excavations around the collapse site and clearing debris and obstructions from inside the pipe. Trench boxes were installed around the damaged section for containment and to prevent further erosion. Once truck-mounted industrial vacuums clear debris, and wastewater levels around the collapse decrease, the agency says teams will be able to more thoroughly assess the damage and determine a repair strategy. 

One repair possibility under consideration is to use a 50-ft section of 72-in pipe from another recently completed project.

Also yet to be determined are the spill’s environmental effects and potential remediation needs, an effort that DC Water says is being coordinated with federal, state and local partners. According to the Potomac Riverkeeper Network, water quality tests of the river taken immediately downstream of the overflow site within the first week found levels of E.coli bacteria to be nearly 12,000 times human safety levels. Although contamination is reportedly dissipating further downstream, the expected slow melt from the area’s heavy Jan, 25 snowfall will likely not aid the process immediately.

DC Water says its $625-million investment over the next ten years is for projects to rehabilitate sections of the Potomac Interceptor, which varies in size from 30-in- to 96-in-dia. reinforced concrete pipe in the main trunk to 13-ft x 7.75-foot rectangular, reinforced concrete pipe in the sewer system’s lower reaches. 

The area where the rupture occurred was to have been part of that program, but it is uncertain when any work there was to take place. At the time DC Water announced the current rehabilitation project by Fort Myer Construction, the agency noted that “a larger upgrade” on the interceptor was planned for later in 2025.