A Broken Pipe Sent Hundreds of Millions of Gallons of Sewage into an NPS Site

Hundreds of millions of gallons of raw sewage spilled into a portion of the Potomac River just outside of Washington, D.C., after a major sewer pipe broke in January, according to the local public utility company. The sewage also poured into portions of the Chesapeake and Ohio National Historic Site, one of the 75 historic sites managed by the National Park Service (NPS).

Officials say more than 243 million gallons of sewage have flowed into the river, and elevated levels of E. coli have also been detected in the area.

“Clean-up of this disaster will not be cheap, likely going into the tens of millions of dollars,” Gary Belan, senior director of clean water supply for the nonprofit American Rivers, told Outside. “The wide variety of pollutants that are now in the river should be concerning to all, especially the immensely high E. coli levels, which, according to samples taken by the Potomac Riverkeeper, are over 4000 times higher than the safe recreational limit.”

On January 19, a pipe collapsed in a section of the Potomac Interceptor (PI), a 54-mile-long sewer system that carries roughly 60 million gallons of sewage daily between Dulles International Airport and the nation’s capital. According to the National Park Service (NPS), the pipe measures between 72 and 96 inches in diameter.

Starting in Washington, D.C.’s historic Georgetown neighborhood, the Chesapeake and Ohio Canal (C&O Canal) is a historic 184-mile canal running along Maryland’s Potomac River. The National Park Service (NPS) manages the National Historic Park in conjunction with the C&O Canal Trust. The site now contains more than 20,000 acres of historic sites and landmarks, attracting roughly 5 million visitors annually.

A Large Rock Dam Likely Caused the Pipe Failure

Crews believe a natural dam created by rocks obstructed the pipeline—they found it stretching “approximately 30 feet downstream of the original failure.”

Since the collapse, crews have set up a diversion around the damaged section of the pipe to excavate and repair it, which carries wastewater from millions of homes in the area, including their bathrooms.

Public utility company DC Water, which is working with NPS to repair the damage, estimates that approximately 243 million gallons have overflowed from the collapse site into the river in the weeks since. In the first five days alone, at least 194 million gallons overflowed.

Elevated Levels of Bacteria Detected in Water System

E. coli is a bacterium found in human feces that can cause gastrointestinal issues when consumed. Historical data show that E. coli levels in the Potomac River can range from 10 to 5,000 MPN/100mL, a statistical measure used to estimate E. coli levels.

At the overflow site, DC Water reported levels to be at 242,000 MPN/100mL on February 6.

These elevated levels of the bacterium are occurring where “snowmelt combined with residual wastewater are entering the river and are periodically further impacted by overflow events,” wrote DC Water in an update.

DC Water says it is preparing an Environmental Restoration Plan following a significant overflow on February 8, when non-biodegradable wipes were flushed into the system, causing another clog. At the time, multiple pumps were also out of service for required cleaning and maintenance.

Downstream sampling sites show that E. coli levels are within acceptable limits set by the Environmental Protection Agency.

Repairs Could Take Weeks or Months

C&O Canal is a popular recreational area for those living in the nation’s capital. The historic park offers hiking, cycling, rock climbing, paddling, and fishing, along with a variety of historic sights.

“The C&O Canal and its towpath are one of the D.C. region’s most heavily used outdoor recreation corridors, providing miles of hiking and biking trails along the Potomac while also preserving the historic landscape and protecting the river’s unique shoreline and habitat,” said Belan.

Repairs could take up to six weeks. The park remains open to visitors.