The Jan. 19 collapse in Montgomery County, Md., occurred in a section of the 72-in.-dia. Potomac Interceptor operated by the District of Columbia Water and Sewer Authority (DC Water). Adjacent to the river near the I-495 Beltway crossing, the 1960s-era pipe is part of a regional system that conveys 60 million gallons of sewage daily from areas of northern Virginia and Maryland to the city’s Blue Plains wastewater treatment plant. Officials have not disclosed the cause of the collapse, which they said is under investigation.

Since the spill, DC Water has said subsequent discharges have largely been contained with a temporary bypass system that uses eight high-capacity pumps to route sewage flow about ½-mile around the break through a dry, clay-lined section of the historic C&O Canal and back into the pipeline. Despite flow surges from two big snowstorms and multiple rain events in recent weeks, DC Water reports no overflows since Feb. 8.

"I’m reassured that DC Water is acting very aggressively to try to repair this, but there’s still a hundred questions out there about what the affect is on the C&O Canal, what the impact is on the Potomac River," Maryland Rep. Jamie Raskin (D) said at a Feb. 26 DC water briefing in Bethesda, Md.

After President Donald Trump's initial social media criticism of local officials for the line collapse and response—despite their assertions that the pipeline is on federal property—he approved the Feb. 18 request of Washington, D.C., Mayor Muriel E. Bowser (D) for federal repair and cleanup assistance. The Corps and the Federal Emergency Management Agency have joined the effort, already including the U.S. Environmental Protection Agency. The latter is involved to prevent additional overflows until the pipe is repaired, it said in a statement.

Rock Blockage Removed Feb. 26

Contractors have refined a managed approach to take individual pumps offline during low-flow periods for preventive maintenance, while the Corps implements measures to contain and divert stormwater from the collapse and bypass area and assist in other project execution areas. Drinking water is unaffected by the spill, as intakes for that system are located several miles upstream, said Col. Francisco Peña, who leads the Corps Baltimore District.

With a temporary steel bulkhead fully isolating the damaged section, inspectors found a large rock and debris blockage about 30 ft away from the break, DC Water said. Boulders, originally used as construction backfill, likely entered the pipe during the initial collapse. The pipe section was deemed structurally compromised and unsafe for workers, so crews excavated a new 30- to 40-ft section to create another access point. 

Contractors cut the crown of the pipe to provide direct access to the blockage, and DC Water said Feb. 26 that the blockage has been removed manualy and by machine, but some large rocks and boulders remain in other sections of the pipe and may require additional excavation to remove. The utility said it now intends to fully develop an emergency repair strategy that could take up to six weeks to complete before the bypass system can be decommissioned.

"An environmental restoration plan is being developed in coordination with federal, state, and local regulators and will be released to the public when approved," it said Feb. 24.

An agency spokesperson said the cost of both the repair and environmental cleanup has now reached about $20 million, according to multiple media reports.

Long Term View

DC Water has not responded to ENR’s requests for information on contractors involved in the response, or how the incident may affect the scope and cost of the agency’s current and long-term infrastructure upgrade efforts—including a previously stated ten-year, $625-million program underway to rehabilitate Potomac Interceptor sections.

The agency has said the 2,700-linear-ft section where the break occurred was targeted for rehabilitation, with work to accelerate when pipeline emergency repairs are complete. Estimated to take nearly one year, the project will use sliplining methods where feasible, while other areas of the pipe will be reinforced and strengthened with a high-strength geopolymer lining.

Bowser said in a Feb. 18 letter to Trump and FEMA that she seeks “100% reimbursement for costs incurred by the District” and D.C. Water, to avoid ratepayer impact. In media comments, she said that “outreach from the president’s team … would indicate to me that they’re supportive of the request.” 

But according to comments by D.C. emergency management Director Clint Osborn made at a Feb. 25 public briefing at DC Water headquarters, reported by locally-based WTOP News, the declaration does not allow the city or DC Water to recoup money already spent on repairs. He clarified earlier statements that the federal government would cover 75% of the utiity company's total repair and cleanup costs as only applying when U.S. agencies directly perform work assigned through the emergency declaration. “We’re going to continue to work through the preliminary damage assessment process with FEMA this week to determine whether we can convince [the agency] and the White House to upgrade us to a major disaster declaration, which would get us reimbursement,” he said.

“How the cost will be borne and allocated is still being worked out,” by DC Water and its four county customers—Montgomery and Prince George's in Maryland, and Fairfax and Loudoun in Virginia, the utility firm spokesperson said.

Meanwhile, a 14-member group of regional House members said it is seeking additional funding for the interceptor repair and upgrade, and related work on other U.S. wastewater treatment systems, “Congress must play a role in solving this crisis, investing in our nation’s wastewater infrastructure, and preventing this and similar crises from recurring,” they said in a Feb. 24 letter to House Transportation and infrastructure Committee leaders. “The failure of the Potomac Interceptor is an acute crisis for our region.”

Yet to be determined are the spill’s lingering effects on the river’s water quality. Sampling by DC Water and state agencies have shown gradually decreasing, although still fluctuating, levels of E. coli and other bacteria downstream from the overflow, with health advisories issued, according to DC Water posted data.

Betsy Nicholas, president of the Potomac Riverkeeper Network, said DC Water’s overall collapse response has been good, and that its independent testing shows downstream water quality largely meeting recreational contact standards despite occasional spikes from high flows and melting ice. But she cautioned that “testing should continue,” especially as warmer weather draws people to riverside areas.

Another concern is that, like other infrastructure agencies, DC Water lacks resources to address other parts of its infrastructure system that may be in jeopardy of failing. “Hopefully, this incident will be the poster child for preventing similar incidents in the future,” Nicholas said.

“It is important to note ... that this incident does not reflect a systematic failure on the Potomac Interceptor,” David Gadis, DC Water CEO and general manager, told regional gpvernment officials on Feb. 23, although describing it as a "known vulnerability" due to its age.. “However it reinforces the importance of the Potomac Interceptor and the continued investment that must occur in [it] to get to where we need to get.”

DC Water will hold another public meeting on the project status at 7 p.m. on Feb. 26 at Walt Whitman High School in Bethesda, Md.,, which will be livestreamed.