⚠️ TRAIL ALERT: C&O Canal / Potomac River Corridor — Health Advisory in Effect
Don't drink or filter water along the C & O Canal Towpath near DC. A 300-million-gallon raw sewage spill near Cabin John, MD has contaminated this ADT corridor. The towpath is passable — but the waterway is off-limits as water sources until further notice.
If you're planning an American Discovery Trail or Great American Rail-Trail Thru-Hike or Section Hike through the C&O Canal corridor near Washington, D.C., there's something important you need to know before you head out.
On January 19, 2026, a section of the 54-mile Potomac Interceptor sewer line collapsed near Clara Barton Parkway and Lock 10 of the C&O Canal in Montgomery County, Maryland — releasing an estimated 240 to 300 million gallons of untreated wastewater into the Potomac River in what has become one of the largest sewage spills in U.S. history.
What hikers on this section of the ADT need to know
The D.C. Department of Energy and Environment, Virginia Department of Health, and Maryland Department of the Environment are urging residents and visitors to avoid recreational activities in the Potomac, including swimming, fishing, and kayaking. That advisory covers a 9.0 mile stretch of the C & O Canal from the American Legion Memorial Bridge to Georgetown.
Don't filter and drink water from the Potomac in this section
— treat it as a non-viable water source until further notice. Carry enough water to cover this corridor, or plan resupply from town sources only.
The trail itself is passable, but use caution.
The C&O Canal towpath remains a key ADT corridor, and you don't need to abandon your plans entirely. But you do need to take this seriously:
Avoid all contact with the Potomac River and the C&O Canal water in the affected area. Bacteria levels in the river during the overflow spiked to over 4,000 times the safe recreational level, and while levels have been trending down, thawing ice could result in delayed releases of bacteria, as could disturbances that churn up sediment on the river bottom.
Drinking water is not affected.
Maryland's active drinking water intakes are upstream and unaffected, and Washington and Arlington's principal water intake at Great Falls is also upstream of the spill.
What's the repair timeline?
DC Water estimates it will take four to six more weeks to route sewage through the pipe once a large boulder found inside it is removed, and a permanent fix is estimated to be 9 months away. That means this issue will likely persist well into the spring and summer 2026 hiking season.
I'll continue monitoring this situation and updating our waypoint notes for this section as conditions change. If you're heading out on the C&O Canal corridor, reach out, and I'll give you the most current intel I have. 🥾
Hike Your Hike - John.
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