The major sewer pipe that collapsed last week in Montgomery County has spilled “catastrophic” levels of wastewater into the Potomac River, according to the nonprofit Potomac Riverkeeper Network.

The Jan. 19 break in a 72-inch diameter section of the Potomac Interceptor — along the Clara Barton Parkway near Interstate 495 — released hundreds of millions of gallons.

“The vile and putrid smell from the torrent of sewage discharging to the Potomac River for eight straight days is one of the most disturbing things I have ever seen in 25 years as a Riverkeeper,” Potomac Riverkeeper Dean Naujoks said in a statement.

Water samples taken by the nonprofit show levels of contamination that can lead to dead zones in the river, harmful algal blooms and fish kills, Naujoks said.

The concentration of E. coli near the broken pipe was nearly 12,000 times that which environmentalists consider acceptable for human contact, the group said.

DC Water, the utility that oversees the pipeline, told The Banner in a statement the Network’s findings are expected, given the volume of overflow, and that it is working with federal, state and local agencies to contain damage.

DC Water reported late Thursday that in the past 24 hours no overflow escaped from the damaged pipe for the first time since it collapsed.

Work began last week with the National Park Service to remove the upper lock gates on the C&O Canal so it can accommodate a bypass for wastewater to flow around the damaged section of the sewer line. It uses a contained section of the canal, running about 2,700 feet, to carry wastewater around the pipe’s damaged section and back into the Potomac Interceptor downstream.

Industrial pumps since Saturday have been moving water through the bypass. They need frequent cleaning, DC Water said, because oils, fats, grease, wipes and other debris cause blockages.

“Any amount of untreated sewage in our rivers and streams is unacceptable, but the volume of this spill is alarming,” said Gussie Maguire, a scientist with The Chesapeake Bay Foundation.

“The Potomac River is one of the Chesapeake Bay’s largest tributaries and is the only source of drinking water for people in the D.C. area.”

Drinking water in the region, which flows through a separate system, is safe and unaffected, and no overflow has reached the C&O Canal towpath, DC Water said.

Keep safe

The Riverkeeper took samples four days after the break in the 54-mile Interceptor, which handles up to 60 million gallons of wastewater a day, moving it from parts of Virginia and Maryland to the Blue Plains Advanced Wastewater Treatment Plant in Washington.

The nonprofit then measured the samples against standards established by Virginia’s Department of Environmental Quality and Maryland’s Department of the Environment.

It also took samples downstream in D.C., at Fletchers Cove, where it found E. coli levels 60 times higher than accepted limits.

People and pets should avoid contact with the contaminated water and shoreline, and immediately wash any exposed skin with water and soap, Montgomery County’s Department of Health and Human Services and the Department of Environmental Protection said Thursday in a press release.

Residents of Fairfax, Loudoun and Montgomery counties, who are served by the Potomac Interceptor, have been asked to avoid flushing wipes and grease.

The fix

Excavation began Wednesday to access a major section of the collapsed pipe. “We’ll be able to better assess the damage, determine the cause of the collapse and develop repair plans,” DC Water spokesperson Sherri Lewis said in a statement this week.

DC Water is rehabilitating the Potomac Interceptor through a 10-year, $625 million project to strengthen the most vulnerable sections of the sewer line, which is more than six decades old.

“Infrastructure failure is at the root of this disaster — the six foot diameter sewage interceptor pipe located this close to the river should have been better maintained in order to avoid this catastrophe," the Riverkeeper group said.

Maryland, Washington and Virginia have made significant investments in reducing wastewater pollution, said Maguire, the Chesapeake Bay Foundation scientist.

But the collapse, she said, shows the necessity of consistent pipe and infrastructure maintenance.