A month after a collapsed pipeline north of Washington, DC, spilled more than 240 million gallons of raw sewage into the Potomac River, potentially the largest sewage spill in U.S. history, weather and site issues continue to hamper efforts to clean up the damaged section and begin repairs. More questions remain about the time and investment needed to restore critical infrastructure and reduce environmental impacts, even with a Feb. 22 disaster declaration and new help from the U.S. Army Corps of Engineers and other federal agencies.
The January 19 sinkhole in Montgomery County, Maryland, occurred in a 72-inch section of the day. Potomac Interceptor operated by the District of Columbia Water and Sewer Authority (DC Water). Along the river near the I-495 Beltway crossing, the 1960s-era pipeline is part of a regional system that carries 60 million gallons of wastewater daily from areas of northern Virginia and Maryland to the city’s Blue Plains Wastewater Treatment Plant. Officials have not released the cause of the collapse, which they say is under investigation.
Since the spill, DC Water has said subsequent spills have been largely contained with a temporary diversion 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 increased flow from two major snowstorms and multiple rain events in recent weeks, DC Water reports no overflows since February 8th.
After President Donald Trump’s initial social media criticism of local officials over the collapse and the line’s response, despite his claims that the pipeline is on federal property, he approved Mayor Muriel E. Bowser’s (D) request on Feb. 18 for federal repair and cleanup in Washington, DC. The Corps and the Federal Emergency Management Agency have joined the effort, which already includes the US Environmental Protection Agency. The latter is involved to prevent additional overflows until the pipeline is repaired, he said in a statement.
A managed approach
Contractors have perfected a managed approach to taking individual pumps offline during periods of low flow for preventative maintenance while the Corps implements measures to contain and divert stormwater from the collapse and bypass zone. Drinking water is not affected by the spill because the dams in that system are several miles upstream, said Col. Francis Pera, who heads the corps’ Baltimore district.
With a temporary steel bulkhead completely isolating the damaged section, inspectors found a large blockage of rock and debris about 30 feet away from the break, DC Water said. The blocks, originally used as construction fill, likely entered the pipe during the initial collapse.
The section of pipe is considered structurally compromised and unsafe for workers, so crews are excavating a new 30- to 40-foot section to create another access point. Contractors will cut the crown of the pipe to provide direct access to the blockage, with a combination of manual and machine removal, DC Water said. The utility will then be able to fully develop an emergency repair strategy that could take up to six weeks to complete before the bypass system can be shut down.
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“An environmental restoration plan is being developed in coordination with federal, state and local regulators and will be released to the public when approved,” he said on Feb. 24.
An agency spokesman said the cost of both the remediation and environmental cleanup has now reached about $20 million, according to multiple media reports.
DC Water has not responded to ENR’s requests for information about the contractors involved in the response, or how the incident may affect the scope and cost of the agency’s current and long-term efforts to upgrade infrastructure, including an ongoing $625 million, ten-year program to rehabilitate sections of the Potomac Interceptor.
The agency has said the 2,700 linear foot section where the break occurred was earmarked for rehabilitation, with work to accelerate once emergency repairs to the pipeline are complete. Estimated to take nearly a year, the project will use sliding methods where possible, while other areas of the pipeline will be reinforced and reinforced with a high-strength geopolymer liner.
Bowser said in a Feb. 18 letter to Trump and FEMA that he is asking for “100 percent reimbursement of the costs incurred by the district” and DC Water, to avoid the impact on taxpayers. In media comments, he said “the communication from the president’s team … would indicate to me that they support the request.” But according to the Corps, the current agreement stipulates that the federal government covers 75 percent of the costs, with DC Water and its four county customers — Montgomery and Prince George’s in Maryland, and Fairfax and Loudoun in Virginia — covering the rest.
“How the cost will be borne and allocated is still being worked out,” said the DC Water spokesperson.
The lingering effects of the spill on the river’s water quality remain to be determined. Sampling by DC Water and state agencies has shown that levels of E. coli and other bacteria downstream of the overflow is gradually decreasing, although it continues to fluctuate, with health advisories issued, according to data released by DC Water.
Betsy Nicholas, president of the Potomac Riverkeeper Network, said the overall response to DC Water’s collapse has been good, and its independent testing shows water quality downstream largely meets recreational contact standards despite occasional spikes in high flows and ice melt. But he warned that “testing should continue”, especially as warmer weather draws people to coastal areas.
Another concern is that, like other infrastructure agencies, DC Water lacks the resources to address other parts of its infrastructure system that may be in danger of failing. “Hopefully, this incident will be the thread to prevent similar incidents in the future,” Nicholas said.
DC Water will hold public meetings on the status of the project on February 24 at 7:00 pm at city headquarters and on February 25 at 7:00 pm at Walt Whitman High School in Bethesda, Maryland. Both will be broadcast live.
